AI Trajectory

null

{
  "EnableConfigs": [
    "INTEL_TDX_HOST",
    "MEMORY_HOTPLUG",
    "MEMORY_HOTREMOVE",
    "ARCH_MEMORY_PROBE",
    "VIRTIO_MEM"
  ],
  "FocusSymbols": [
    "memblock_bsearch_start",
    "memblock_add_range",
    "memblock_isolate_range",
    "memblock_search",
    "memblock_add_node",
    "memblock_remove",
    "memblock_search_pfn_nid"
  ],
  "KMSANReasoning": "The patch optimizes memblock region lookups (in memblock_add_range, memblock_isolate_range, and memblock_search) by implementing a binary search helper memblock_bsearch_start() to locate candidate region indices instead of performing linear scans from index 0.\n\nNone of the changes touch kernel-to-user copy paths (no copy_to_user, netlink, ioctl, etc.), nor do they allocate or manipulate data structures with uninitialized fields or padding. All local variables (start_idx, low, high, mid) are fully initialized before use. Any potential bugs in this patch would be algorithmic or bounds-related (e.g., off-by-one errors or out-of-bounds indexing in the memblock region array), which are detected by KASAN, assertions, or functional tests. Because no uninitialized memory reads or information leaks are introduced or exposed, a dedicated KMSAN fuzzing session is not justified.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch introduces memblock_bsearch_start() and refactors region search and iteration loops in mm/memblock.c (memblock_add_range, memblock_isolate_range, memblock_search). While memblock is primarily used during boot, on amd64 CONFIG_INTEL_TDX_HOST selects CONFIG_ARCH_KEEP_MEMBLOCK, preventing discard of memblock data and code at runtime. When combined with CONFIG_MEMORY_HOTPLUG (reachable via virtio-mem or sysfs memory probe), memblock_add_node(), memblock_remove(), and memblock_search_pfn_nid() are actively invoked during runtime memory hotplug/hot-remove operations. Fuzzing is warranted to test the binary search boundaries and region isolation/addition logic for potential corruption or regression.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit a0b4f7e344ea151e0201c1a5949be01597a0a65f\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Sun Sep 27 22:33:02 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/mm/memblock.c b/mm/memblock.c\nindex f5aaa38cfa313..87c71435c80c5 100644\n--- a/mm/memblock.c\n+++ b/mm/memblock.c\n@@ -155,11 +155,6 @@ struct memblock_type physmem = {\n  */\n static __refdata struct memblock_type *memblock_memory = \u0026memblock.memory;\n \n-#define for_each_memblock_type(i, memblock_type, rgn)\t\t\t\\\n-\tfor (i = 0, rgn = \u0026memblock_type-\u003eregions[0];\t\t\t\\\n-\t     i \u003c memblock_type-\u003ecnt;\t\t\t\t\t\\\n-\t     i++, rgn = \u0026memblock_type-\u003eregions[i])\n-\n #define memblock_dbg(fmt, ...)\t\t\t\t\t\t\\\n \tdo {\t\t\t\t\t\t\t\t\\\n \t\tif (memblock_debug)\t\t\t\t\t\\\n@@ -591,6 +586,33 @@ static void __init_memblock memblock_insert_region(struct memblock_type *type,\n \ttype-\u003etotal_size += size;\n }\n \n+/**\n+ * memblock_bsearch_start - Find the first region index where rend \u003e base\n+ * @type: memblock type to search\n+ * @base: base physical address of the candidate range\n+ *\n+ * Returns the first region index that could potentially overlap @base.\n+ */\n+static int __init_memblock memblock_bsearch_start(struct memblock_type *type,\n+\t\t\t\t\t\t  phys_addr_t base)\n+{\n+\tint mid, low = 0;\n+\tint high = type-\u003ecnt;\n+\n+\tif (type-\u003ecnt \u0026\u0026 base \u003e= type-\u003eregions[type-\u003ecnt - 1].base +\n+\t\t\t\t type-\u003eregions[type-\u003ecnt - 1].size)\n+\t\treturn type-\u003ecnt;\n+\n+\twhile (low \u003c high) {\n+\t\tmid = (low + high) / 2;\n+\t\tif (type-\u003eregions[mid].base + type-\u003eregions[mid].size \u003c= base)\n+\t\t\tlow = mid + 1;\n+\t\telse\n+\t\t\thigh = mid;\n+\t}\n+\treturn low;\n+}\n+\n /**\n  * memblock_add_range - add new memblock region\n  * @type: memblock type to add new region into\n@@ -614,8 +636,7 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,\n \tbool insert = false;\n \tphys_addr_t obase = base;\n \tphys_addr_t end = base + memblock_cap_size(base, \u0026size);\n-\tint idx, nr_new, start_rgn = -1, end_rgn;\n-\tstruct memblock_region *rgn;\n+\tint idx, start_idx, nr_new, start_rgn = -1, end_rgn;\n \n \tif (!size)\n \t\treturn 0;\n@@ -650,8 +671,10 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,\n \t */\n \tbase = obase;\n \tnr_new = 0;\n+\tstart_idx = memblock_bsearch_start(type, base);\n \n-\tfor_each_memblock_type(idx, type, rgn) {\n+\tfor (idx = start_idx; idx \u003c type-\u003ecnt; idx++) {\n+\t\tstruct memblock_region *rgn = \u0026type-\u003eregions[idx];\n \t\tphys_addr_t rbase = rgn-\u003ebase;\n \t\tphys_addr_t rend = rbase + rgn-\u003esize;\n \n@@ -814,8 +837,7 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,\n \t\t\t\t\tint *start_rgn, int *end_rgn)\n {\n \tphys_addr_t end = base + memblock_cap_size(base, \u0026size);\n-\tint idx;\n-\tstruct memblock_region *rgn;\n+\tint idx, start_idx;\n \n \t*start_rgn = *end_rgn = 0;\n \n@@ -827,7 +849,10 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,\n \t\tif (memblock_double_array(type, base, size) \u003c 0)\n \t\t\treturn -ENOMEM;\n \n-\tfor_each_memblock_type(idx, type, rgn) {\n+\tstart_idx = memblock_bsearch_start(type, base);\n+\n+\tfor (idx = start_idx; idx \u003c type-\u003ecnt; idx++) {\n+\t\tstruct memblock_region *rgn = \u0026type-\u003eregions[idx];\n \t\tphys_addr_t rbase = rgn-\u003ebase;\n \t\tphys_addr_t rend = rbase + rgn-\u003esize;\n \n@@ -2067,19 +2092,10 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit)\n \n static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)\n {\n-\tunsigned int left = 0, right = type-\u003ecnt;\n-\n-\tdo {\n-\t\tunsigned int mid = (right + left) / 2;\n+\tint idx = memblock_bsearch_start(type, addr);\n \n-\t\tif (addr \u003c type-\u003eregions[mid].base)\n-\t\t\tright = mid;\n-\t\telse if (addr \u003e= (type-\u003eregions[mid].base +\n-\t\t\t\t  type-\u003eregions[mid].size))\n-\t\t\tleft = mid + 1;\n-\t\telse\n-\t\t\treturn mid;\n-\t} while (left \u003c right);\n+\tif (idx \u003c type-\u003ecnt \u0026\u0026 addr \u003e= type-\u003eregions[idx].base)\n+\t\treturn idx;\n \treturn -1;\n }\n \n@@ -2194,11 +2210,11 @@ static void __init_memblock memblock_dump(struct memblock_type *type)\n \tphys_addr_t base, end, size;\n \tenum memblock_flags flags;\n \tint idx;\n-\tstruct memblock_region *rgn;\n \n \tpr_info(\" %s.cnt  = 0x%lx\\n\", type-\u003ename, type-\u003ecnt);\n \n-\tfor_each_memblock_type(idx, type, rgn) {\n+\tfor (idx = 0; idx \u003c type-\u003ecnt; idx++) {\n+\t\tstruct memblock_region *rgn = \u0026type-\u003eregions[idx];\n \t\tchar nid_buf[32] = \"\";\n \n \t\tbase = rgn-\u003ebase;\n"
}

core

null

{
  "EnableConfigs": [
    "INTEL_TDX_HOST",
    "MEMORY_HOTPLUG",
    "MEMORY_HOTREMOVE",
    "ARCH_MEMORY_PROBE",
    "VIRTIO_MEM"
  ],
  "FocusSymbols": [
    "memblock_bsearch_start",
    "memblock_add_range",
    "memblock_isolate_range",
    "memblock_search",
    "memblock_add_node",
    "memblock_remove",
    "memblock_search_pfn_nid"
  ],
  "Reasoning": "The patch introduces memblock_bsearch_start() and refactors region search and iteration loops in mm/memblock.c (memblock_add_range, memblock_isolate_range, memblock_search). While memblock is primarily used during boot, on amd64 CONFIG_INTEL_TDX_HOST selects CONFIG_ARCH_KEEP_MEMBLOCK, preventing discard of memblock data and code at runtime. When combined with CONFIG_MEMORY_HOTPLUG (reachable via virtio-mem or sysfs memory probe), memblock_add_node(), memblock_remove(), and memblock_search_pfn_nid() are actively invoked during runtime memory hotplug/hot-remove operations. Fuzzing is warranted to test the binary search boundaries and region isolation/addition logic for potential corruption or regression.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer and security engineer.
Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on internal assumptions. You must actively use your code access
tools to inspect the actual source code, callers, and surrounding context.

================================================================================
1. CORE TRIAGE PHILOSOPHY
================================================================================
The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs,
and newly triggered assertions introduced by the patch series.

- REACHABILITY IS THE PRIMARY GATE:
  Fuzzing can only discover bugs in code that can actually execute in standard virtualized
  environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap).
  If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed,
  regardless of whether it adds assertions or complex logic.

- DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS:
  Patch authors routinely label changes as "cleanups", "refactorings", or state
  "No functional change intended". Do NOT take these claims at face value.
  Code refactorings that rearrange logic, introduce helper functions, or alter state management
  in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs.
  If reachable executable code is modified or refactored, it MUST be fuzzed.

- NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED:
  When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON*, VM_WARN_ON*,
  BUG_ON*, lockdep_assert*) in reachable code paths, it enforces new or stricter invariants.
  Even if the author believes the invariant always holds, fuzzing is essential to verify whether
  an unusual sequence of operations can violate it.

================================================================================
2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA)
================================================================================
Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories:

- Non-kernel and non-executable changes:
  * Modifications to Documentation/, comments, or spelling fixes.
  * User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/)
    that do not affect the compiled kernel image (vmlinux) or kernel modules.
  * Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints
    that do not alter control flow or data structures.
  * Build system or Kconfig changes that do not alter compiled C logic.
- Structurally unreachable hardware:
  * Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed,
    ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU.
- Unreachable execution paths:
  * Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during
    physical PCI hot-unplug or manual sysfs driver unbinding.
  * Code paths exclusive to architectures other than the target architecture.

================================================================================
3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA)
================================================================================
Return WorthFuzzing=true whenever the patch touches reachable executable code, including:
- Core Subsystems:
  * Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/),
    BPF, scheduler, core networking, VFS, or syscall handling.
- Refactorings and Code Cleanups:
  * Any restructuring of reachable data structures, helper abstractions, or algorithm flows.
- Runtime Assertions and Defensive Checks:
  * Any introduction or alteration of assertions (WARN_ON*, VM_WARN_ON*, BUG_ON*, etc.) in reachable paths.
- Reachable Drivers and Protocols:
  * Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.).

================================================================================
4. EXTRACTING FocusSymbols (PREVENTING DILUTION)
================================================================================
When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer:

- AVOID UBIQUITOUS LIFECYCLE HOT-PATHS:
  Do NOT list generic, ubiquitous functions called by almost every program in the corpus
  (including, but not limited to: general memory allocators and deallocators, page fault
  and trap handlers, or core synchronization primitives; this is not an exhaustive list).
  Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused",
  which severely dilutes fuzzing effort away from the actual changes.

- TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS:
  List functions that specifically implement the logic being added or altered, or direct API entrypoints
  for the subsystem feature under review.

- HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h):
  Compiler-inlined static functions (such as static inlines in mm/*.h or include/linux/*.h) lack
  distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters.
  If the changes are primarily in static inline helpers, identify non-static, feature-specific caller
  functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers).

================================================================================
5. IDENTIFYING EnableConfigs
================================================================================
Identify any specific CONFIG_ options required to properly compile and reach the modified code:
- Inspect Kconfig files and #ifdef guards; do not make assumptions.
- Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed.
- Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit a0b4f7e344ea151e0201c1a5949be01597a0a65f
Author: syz-cluster <triage@syzkaller.com>
Date:   Sun Sep 27 22:33:02 2026 +0000

    syz-cluster: applied patch under review

diff --git a/mm/memblock.c b/mm/memblock.c
index f5aaa38cfa313..87c71435c80c5 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -155,11 +155,6 @@ struct memblock_type physmem = {
  */
 static __refdata struct memblock_type *memblock_memory = &memblock.memory;
 
-#define for_each_memblock_type(i, memblock_type, rgn)			\
-	for (i = 0, rgn = &memblock_type->regions[0];			\
-	     i < memblock_type->cnt;					\
-	     i++, rgn = &memblock_type->regions[i])
-
 #define memblock_dbg(fmt, ...)						\
 	do {								\
 		if (memblock_debug)					\
@@ -591,6 +586,33 @@ static void __init_memblock memblock_insert_region(struct memblock_type *type,
 	type->total_size += size;
 }
 
+/**
+ * memblock_bsearch_start - Find the first region index where rend > base
+ * @type: memblock type to search
+ * @base: base physical address of the candidate range
+ *
+ * Returns the first region index that could potentially overlap @base.
+ */
+static int __init_memblock memblock_bsearch_start(struct memblock_type *type,
+						  phys_addr_t base)
+{
+	int mid, low = 0;
+	int high = type->cnt;
+
+	if (type->cnt && base >= type->regions[type->cnt - 1].base +
+				 type->regions[type->cnt - 1].size)
+		return type->cnt;
+
+	while (low < high) {
+		mid = (low + high) / 2;
+		if (type->regions[mid].base + type->regions[mid].size <= base)
+			low = mid + 1;
+		else
+			high = mid;
+	}
+	return low;
+}
+
 /**
  * memblock_add_range - add new memblock region
  * @type: memblock type to add new region into
@@ -614,8 +636,7 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,
 	bool insert = false;
 	phys_addr_t obase = base;
 	phys_addr_t end = base + memblock_cap_size(base, &size);
-	int idx, nr_new, start_rgn = -1, end_rgn;
-	struct memblock_region *rgn;
+	int idx, start_idx, nr_new, start_rgn = -1, end_rgn;
 
 	if (!size)
 		return 0;
@@ -650,8 +671,10 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,
 	 */
 	base = obase;
 	nr_new = 0;
+	start_idx = memblock_bsearch_start(type, base);
 
-	for_each_memblock_type(idx, type, rgn) {
+	for (idx = start_idx; idx < type->cnt; idx++) {
+		struct memblock_region *rgn = &type->regions[idx];
 		phys_addr_t rbase = rgn->base;
 		phys_addr_t rend = rbase + rgn->size;
 
@@ -814,8 +837,7 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
 					int *start_rgn, int *end_rgn)
 {
 	phys_addr_t end = base + memblock_cap_size(base, &size);
-	int idx;
-	struct memblock_region *rgn;
+	int idx, start_idx;
 
 	*start_rgn = *end_rgn = 0;
 
@@ -827,7 +849,10 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
 		if (memblock_double_array(type, base, size) < 0)
 			return -ENOMEM;
 
-	for_each_memblock_type(idx, type, rgn) {
+	start_idx = memblock_bsearch_start(type, base);
+
+	for (idx = start_idx; idx < type->cnt; idx++) {
+		struct memblock_region *rgn = &type->regions[idx];
 		phys_addr_t rbase = rgn->base;
 		phys_addr_t rend = rbase + rgn->size;
 
@@ -2067,19 +2092,10 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit)
 
 static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)
 {
-	unsigned int left = 0, right = type->cnt;
-
-	do {
-		unsigned int mid = (right + left) / 2;
+	int idx = memblock_bsearch_start(type, addr);
 
-		if (addr < type->regions[mid].base)
-			right = mid;
-		else if (addr >= (type->regions[mid].base +
-				  type->regions[mid].size))
-			left = mid + 1;
-		else
-			return mid;
-	} while (left < right);
+	if (idx < type->cnt && addr >= type->regions[idx].base)
+		return idx;
 	return -1;
 }
 
@@ -2194,11 +2210,11 @@ static void __init_memblock memblock_dump(struct memblock_type *type)
 	phys_addr_t base, end, size;
 	enum memblock_flags flags;
 	int idx;
-	struct memblock_region *rgn;
 
 	pr_info(" %s.cnt  = 0x%lx\n", type->name, type->cnt);
 
-	for_each_memblock_type(idx, type, rgn) {
+	for (idx = 0; idx < type->cnt; idx++) {
+		struct memblock_region *rgn = &type->regions[idx];
 		char nid_buf[32] = "";
 
 		base = rgn->base;

gemini-3.8-flash

null

null

							input: 4350
							output: 28
							thoughts: 199
						

**Analyzing the Proposed Patch to `mm/memblock.c`**

Okay, here's the situation: I need to evaluate a patch submitted for `mm/memblock.c`. My initial instinct is to dissect the changes meticulously. First, let's zoom in on the specific functions that have been touched. The patch seems to be modifying several key functions within `mm/memblock.c`: `memblock_bsearch_start`, `memblock_add_range`, `memblock_isolate_range`, `memblock_search`, and `memblock_dump`. The important detail is that `__init_memblock` is also being added/used.

My immediate question is: what is the meaning of `__init_memblock` and its relationship to the `memblock` subsystem? I know that `memblock` is crucial for early memory allocation in the kernel, but I need to fully understand this context to assess the potential impact of this patch and whether the added or modified code is reachable through something like syzkaller. Time to quickly search the include/ and mm/ directories for the `__init_memblock` to understand what this new flag means for the memblock structure.

{
  "Expression": "define __init_memblock",
  "PathPrefix": "include/"
}

{
  "Output": "include/linux/memblock.h=114=extern struct memblock memblock;\n--\ninclude/linux/memblock.h-116-#ifndef CONFIG_ARCH_KEEP_MEMBLOCK\ninclude/linux/memblock.h:117:#define __init_memblock __meminit\ninclude/linux/memblock.h-118-#define __initdata_memblock __meminitdata\ninclude/linux/memblock.h=119=void memblock_discard(void);\ninclude/linux/memblock.h-120-#else\ninclude/linux/memblock.h:121:#define __init_memblock\ninclude/linux/memblock.h-122-#define __initdata_memblock\n"
}

gemini-3.8-flash

null

null

							input: 5014
							output: 28
							thoughts: 97
						

**Analyzing the `memblock` Initialization and Usage**

Okay, so I'm digging into this `__init_memblock` function. It looks like its either defined as `__meminit` or it's empty if `CONFIG_ARCH_KEEP_MEMBLOCK` is set. That's the first thing I need to remember. Now, the big question is, *where* is `memblock` actually utilized? Is this just something that's relevant during early boot, initial memory setup, or is it something that's used throughout the system's lifetime, especially for runtime memory hotplug?

Alright, time to get practical. I need to track down the callers of the core `memblock` functions. I'm talking about `memblock_add_range`, `memblock_isolate_range`, `memblock_search`, and anything else related to `memblock`. I need to understand the execution flow and the contexts where these calls are made. My next step is a code search! Let's see who's making use of these functions.

{
  "Expression": "memblock_add_range",
  "PathPrefix": "mm/"
}

{
  "Output": "mm/memblock.c=596=static int __init_memblock memblock_bsearch_start(struct memblock_type *type,\n--\nmm/memblock.c-616-/**\nmm/memblock.c:617: * memblock_add_range - add new memblock region\nmm/memblock.c-618- * @type: memblock type to add new region into\n--\nmm/memblock.c-631- */\nmm/memblock.c:632:static int __init_memblock memblock_add_range(struct memblock_type *type,\nmm/memblock.c-633-\t\t\t\tphys_addr_t base, phys_addr_t size,\n--\nmm/memblock.c-746- * Add new memblock region [@base, @base + @size) to the \"memory\"\nmm/memblock.c:747: * type. See memblock_add_range() description for mode details\nmm/memblock.c-748- *\n--\nmm/memblock.c=752=int __init_memblock memblock_add_node(phys_addr_t base, phys_addr_t size,\n--\nmm/memblock.c-759-\nmm/memblock.c:760:\treturn memblock_add_range(\u0026memblock.memory, base, size, nid, flags);\nmm/memblock.c-761-}\n--\nmm/memblock.c-768- * Add new memblock region [@base, @base + @size) to the \"memory\"\nmm/memblock.c:769: * type. See memblock_add_range() description for mode details\nmm/memblock.c-770- *\n--\nmm/memblock.c=774=int __init_memblock memblock_add(phys_addr_t base, phys_addr_t size)\n--\nmm/memblock.c-780-\nmm/memblock.c:781:\treturn memblock_add_range(\u0026memblock.memory, base, size, MAX_NUMNODES, 0);\nmm/memblock.c-782-}\n--\nmm/memblock.c=1032=int __init_memblock __memblock_reserve(phys_addr_t base, phys_addr_t size,\n--\nmm/memblock.c-1039-\nmm/memblock.c:1040:\treturn memblock_add_range(\u0026memblock.reserved, base, size, nid, flags);\nmm/memblock.c-1041-}\n--\nmm/memblock.c=1044=int __init_memblock memblock_physmem_add(phys_addr_t base, phys_addr_t size)\n--\nmm/memblock.c-1050-\nmm/memblock.c:1051:\treturn memblock_add_range(\u0026physmem, base, size, MAX_NUMNODES, 0);\nmm/memblock.c-1052-}\n"
}

gemini-3.8-flash

null

null

							input: 6118
							output: 20
							thoughts: 106
						

**Investigating Memblock Usage**

Okay, let's dive into this `memblock` situation. My initial thought is to trace the callers of the core `memblock` functions – `memblock_add`, `memblock_reserve`, `memblock_isolate_range`, and `memblock_search` specifically. I need a clear picture of how these are being used within the system.

I have a nagging question though: can `memblock` functions even be called *after* the initial boot process? I need to be sure about that. Specifically, I'm wondering if memory hotplug mechanisms rely on `memblock` somehow. That's a critical point to clarify.

To get a better overview, I need to know how these memory blocks are deallocated. Let me track down where `memblock_free_all` or `memblock_discard` are being used. Following these function calls should provide insights into the lifecycle of these memory regions.

Finally, I'm going to take a look at the `mm/memblock.c` file. I'll read around the code that implements `memblock_free_all` or simply search for that function to quickly find the relevant part of the code and understand its behavior. This should give me a solid grasp on how `memblock` works under the hood.

{
  "Expression": "memblock_free_all"
}

{
  "Output": "Documentation/mm/memory-model.rst=44=call :c:func:`free_area_init` function. Yet, the mappings array is not\nDocumentation/mm/memory-model.rst:45:usable until the call to :c:func:`memblock_free_all` that hands all the\nDocumentation/mm/memory-model.rst-46-memory to the page allocator.\n--\nDocumentation/translations/zh_CN/mm/memory-model.rst=34=FLATMEM\n--\nDocumentation/translations/zh_CN/mm/memory-model.rst-44-为了分配 `mem_map` 数组，架构特定的设置代码应该调用free_area_init()函数。\nDocumentation/translations/zh_CN/mm/memory-model.rst:45:然而，在调用memblock_free_all()函数之前，映射数组是不能使用的，该函数\nDocumentation/translations/zh_CN/mm/memory-model.rst-46-将所有的内存交给页分配器。\n--\narch/x86/xen/mmu_pv.c=855=static void __init xen_mark_pinned(struct mm_struct *mm, struct page *page,\n--\narch/x86/xen/mmu_pv.c-864- * the book-keeping now once struct pages for allocated pages are\narch/x86/xen/mmu_pv.c:865: * initialized. This happens only after memblock_free_all() is called.\narch/x86/xen/mmu_pv.c-866- */\n--\nmm/memblock.c=1584=phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,\n--\nmm/memblock.c-1594-\t * this moment memblock may be deinitialized already and its\nmm/memblock.c:1595:\t * internal data may be destroyed (after execution of memblock_free_all)\nmm/memblock.c-1596-\t */\n--\nmm/memblock.c=2494=void __init reset_all_zones_managed_pages(void)\n--\nmm/memblock.c-2507-/**\nmm/memblock.c:2508: * memblock_free_all - release free pages to the buddy allocator\nmm/memblock.c-2509- */\nmm/memblock.c:2510:void __init memblock_free_all(void)\nmm/memblock.c-2511-{\n--\nmm/mm_init.c=820=static void __init init_unavailable_range(unsigned long spfn,\n--\nmm/mm_init.c-839- * Initially all pages are reserved - free ones are freed\nmm/mm_init.c:840: * up by memblock_free_all() once the early boot process is\nmm/mm_init.c-841- * done. Non-atomic initialization, single-pass.\n--\nmm/mm_init.c=2643=void __init mm_core_init(void)\n--\nmm/mm_init.c-2669-\nmm/mm_init.c:2670:\tmemblock_free_all();\nmm/mm_init.c-2671-\tmem_init();\n--\nmm/mm_init.h=114=bool memblock_has_mirror(void);\nmm/mm_init.h:115:void memblock_free_all(void);\nmm/mm_init.h-116-\n"
}

gemini-3.8-flash

null

null

							input: 7398
							output: 18
							thoughts: 52
						

Here's my summary, as the thought process unfolds:

**Digging into Early Boot Memory Management**

Okay, let's dive into the memory management initialization during early boot. Right, first up, let's look at `mm/mm_init.c`. Ah, `memblock_free_all()` is called pretty darn early. Okay, that's interesting. I know what `memblock_free_all()` *does* in principle - releases all the memory blocks the system knows about. But, the real question is *what happens next*? It's not the releasing of the memory blocks that's important - it is what is done *after* that. I need to understand the sequencing and dependencies here to see the overall memory strategy during this critical phase. Okay, let's get into the code and see where things go from there. Right, so I need to check `memblock_discard`. That has to be key. I have to see what that call does.

{
  "Expression": "memblock_discard"
}

{
  "Output": "include/linux/memblock.h=114=extern struct memblock memblock;\n--\ninclude/linux/memblock.h-118-#define __initdata_memblock __meminitdata\ninclude/linux/memblock.h:119:void memblock_discard(void);\ninclude/linux/memblock.h-120-#else\n--\ninclude/linux/memblock.h-122-#define __initdata_memblock\ninclude/linux/memblock.h:123:static inline void memblock_discard(void) {}\ninclude/linux/memblock.h-124-#endif\n--\nmm/kmsan/init.c=101=static struct metadata_page_pair held_back[NR_PAGE_ORDERS] __initdata;\n--\nmm/kmsan/init.c-113- * At the very end there may be leftover blocks in held_back[]. They are\nmm/kmsan/init.c:114: * collected later by kmsan_memblock_discard().\nmm/kmsan/init.c-115- */\n--\nmm/kmsan/init.c=181=static void collect_split(void)\n--\nmm/kmsan/init.c-202- */\nmm/kmsan/init.c:203:static void kmsan_memblock_discard(void)\nmm/kmsan/init.c-204-{\n--\nmm/kmsan/init.c=229=void __init kmsan_init_runtime(void)\n--\nmm/kmsan/init.c-232-\tkmsan_internal_task_create(current);\nmm/kmsan/init.c:233:\tkmsan_memblock_discard();\nmm/kmsan/init.c-234-\tpr_info(\"Starting KernelMemorySanitizer\\n\");\n--\nmm/memblock.c=143=struct memblock_type physmem = {\n--\nmm/memblock.c-153- *  For architectures that do not keep memblock data after init, this\nmm/memblock.c:154: * pointer will be reset to NULL at memblock_discard()\nmm/memblock.c-155- */\n--\nmm/memblock.c=359=static void __init_memblock memblock_remove_region(struct memblock_type *type, unsigned long r)\n--\nmm/memblock.c-377-/**\nmm/memblock.c:378: * memblock_discard - discard memory and reserved arrays if they were allocated\nmm/memblock.c-379- */\nmm/memblock.c:380:void __init memblock_discard(void)\nmm/memblock.c-381-{\n--\nmm/mm_init.c=2239=void __init page_alloc_init_late(void)\n--\nmm/mm_init.c-2270-\t/* Discard memblock private memory */\nmm/mm_init.c:2271:\tmemblock_discard();\nmm/mm_init.c-2272-\n"
}

gemini-3.8-flash

null

null

							input: 8445
							output: 20
							thoughts: 31
						

Okay, here's the summary, rendered as if I'm the one thinking it:

**Digging into `CONFIG_ARCH_KEEP_MEMBLOCK`**

Hold on a second, something just pinged my radar. I need to understand which architectures utilize `CONFIG_ARCH_KEEP_MEMBLOCK`. It's a key configuration, so I should know what specific platforms need this. Let me check the configuration definition directly. It's time to dig into the details and see what's being affected.

{
  "Expression": "ARCH_KEEP_MEMBLOCK"
}

{
  "Output": "arch/arm/Kconfig=2=config ARM\n--\narch/arm/Kconfig-35-\tselect ARCH_HAS_GCOV_PROFILE_ALL\narch/arm/Kconfig:36:\tselect ARCH_KEEP_MEMBLOCK\narch/arm/Kconfig-37-\tselect ARCH_HAS_UBSAN\n--\narch/arm64/Kconfig=2=config ARM64\n--\narch/arm64/Kconfig-63-\tselect ARCH_HAVE_TRACE_MMIO_ACCESS\narch/arm64/Kconfig:64:\tselect ARCH_KEEP_MEMBLOCK\narch/arm64/Kconfig-65-\tselect ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE\n--\narch/loongarch/Kconfig=2=config LOONGARCH\n--\narch/loongarch/Kconfig-58-\tselect ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPTION\narch/loongarch/Kconfig:59:\tselect ARCH_KEEP_MEMBLOCK\narch/loongarch/Kconfig-60-\tselect ARCH_MIGHT_HAVE_PC_PARPORT\n--\narch/mips/Kconfig=2=config MIPS\n--\narch/mips/Kconfig-21-\tselect ARCH_HAS_GCOV_PROFILE_ALL\narch/mips/Kconfig:22:\tselect ARCH_KEEP_MEMBLOCK\narch/mips/Kconfig-23-\tselect ARCH_USE_BUILTIN_BSWAP\n--\narch/powerpc/Kconfig=118=config PPC\n--\narch/powerpc/Kconfig-163-\tselect ARCH_HAVE_EXTRA_ELF_NOTES        if SPU_BASE\narch/powerpc/Kconfig:164:\tselect ARCH_KEEP_MEMBLOCK\narch/powerpc/Kconfig-165-\tselect ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE\tif PPC_RADIX_MMU\n--\narch/riscv/Kconfig=13=config RISCV\n--\narch/riscv/Kconfig-60-\tselect ARCH_HAVE_NMI_SAFE_CMPXCHG\narch/riscv/Kconfig:61:\tselect ARCH_KEEP_MEMBLOCK if ACPI || KEXEC\narch/riscv/Kconfig-62-\tselect ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE\tif 64BIT \u0026\u0026 MMU\n--\narch/x86/Kconfig=1868=config INTEL_TDX_HOST\n--\narch/x86/Kconfig-1873-\tdepends on X86_X2APIC\narch/x86/Kconfig:1874:\tselect ARCH_KEEP_MEMBLOCK\narch/x86/Kconfig-1875-\tdepends on CONTIG_ALLOC\n--\ndrivers/firmware/efi/efi.c=1073=static int efi_mem_reserve_iomem(phys_addr_t addr, u64 size)\n--\ndrivers/firmware/efi/efi.c-1095-\t */\ndrivers/firmware/efi/efi.c:1096:\tif (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK) \u0026\u0026 !ret)\ndrivers/firmware/efi/efi.c-1097-\t\tmemblock_reserve(addr, size);\n--\ninclude/linux/memblock.h=114=extern struct memblock memblock;\ninclude/linux/memblock.h-115-\ninclude/linux/memblock.h:116:#ifndef CONFIG_ARCH_KEEP_MEMBLOCK\ninclude/linux/memblock.h-117-#define __init_memblock __meminit\n--\nkernel/kexec_file.c=580=static int locate_mem_hole_callback(struct resource *res, void *arg)\n--\nkernel/kexec_file.c-606-\nkernel/kexec_file.c:607:#ifdef CONFIG_ARCH_KEEP_MEMBLOCK\nkernel/kexec_file.c-608-static int kexec_walk_memblock(struct kexec_buf *kbuf,\n--\nkernel/kexec_file.c=736=int kexec_locate_mem_hole(struct kexec_buf *kbuf)\n--\nkernel/kexec_file.c-758-\nkernel/kexec_file.c:759:\tif (!IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))\nkernel/kexec_file.c-760-\t\tret = kexec_walk_resources(kbuf, locate_mem_hole_callback);\n--\nmm/Kconfig=482=config HAVE_GUP_FAST\n--\nmm/Kconfig-488-# Also, memblocks are updated with memory hot(un)plug.\nmm/Kconfig:489:config ARCH_KEEP_MEMBLOCK\nmm/Kconfig-490-\tbool\n--\nmm/memblock.c-100- *\nmm/memblock.c:101: * Unless an architecture enables %CONFIG_ARCH_KEEP_MEMBLOCK, the\nmm/memblock.c-102- * memblock data structures (except \"physmem\") will be discarded after the\n--\nmm/memblock.c=359=static void __init_memblock memblock_remove_region(struct memblock_type *type, unsigned long r)\n--\nmm/memblock.c-375-\nmm/memblock.c:376:#ifndef CONFIG_ARCH_KEEP_MEMBLOCK\nmm/memblock.c-377-/**\n--\nmm/memblock.c=957=unsigned long free_reserved_area(void *start, void *end, int poison, const char *s)\n--\nmm/memblock.c-975-\nmm/memblock.c:976:\tif (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {\nmm/memblock.c-977-\t\tif (start_pa \u003c end_pa)\n--\nmm/memblock.c=1013=int __init_memblock memblock_phys_free(phys_addr_t base, phys_addr_t size)\n--\nmm/memblock.c-1022-\nmm/memblock.c:1023:\tif (!slab_is_available() || IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))\nmm/memblock.c-1024-\t\tret = memblock_remove_range(\u0026memblock.reserved, base, size);\n--\nmm/memblock.c=2893=__setup(\"reserve_mem=\", reserve_mem);\n--\nmm/memblock.c-2895-#ifdef CONFIG_DEBUG_FS\nmm/memblock.c:2896:#ifdef CONFIG_ARCH_KEEP_MEMBLOCK\nmm/memblock.c-2897-static const char * const flagname[] = {\n--\nmm/memblock.c=2957=static inline void memblock_debugfs_expose_arrays(struct dentry *root) { }\nmm/memblock.c-2958-\nmm/memblock.c:2959:#endif /* CONFIG_ARCH_KEEP_MEMBLOCK */\nmm/memblock.c-2960-\n--\nmm/memblock.c=2981=static int __init memblock_init_debugfs(void)\n--\nmm/memblock.c-2984-\nmm/memblock.c:2985:\tif (!IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK) \u0026\u0026 !reserved_mem_count)\nmm/memblock.c-2986-\t\treturn 0;\n--\nmm/memory_hotplug.c=1500=static int __add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags,\n--\nmm/memory_hotplug.c-1530-\nmm/memory_hotplug.c:1531:\tif (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {\nmm/memory_hotplug.c-1532-\t\tif (res-\u003eflags \u0026 IORESOURCE_SYSRAM_DRIVER_MANAGED)\n--\nmm/memory_hotplug.c-1601-error_memblock_remove:\nmm/memory_hotplug.c:1602:\tif (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))\nmm/memory_hotplug.c-1603-\t\tmemblock_remove(start, size);\n--\nmm/memory_hotplug.c=2291=static int try_remove_memory(u64 start, u64 size)\n--\nmm/memory_hotplug.c-2331-\nmm/memory_hotplug.c:2332:\tif (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))\nmm/memory_hotplug.c-2333-\t\tmemblock_remove(start, size);\n"
}

gemini-3.8-flash

null

null

							input: 10779
							output: 28
							thoughts: 302
						

**Analyzing the Memblock Patch**

Okay, here we go. First glance - hmm, interesting. The target architecture is amd64, that's x86_64. Now, I need to jog my memory...does x86 automatically enable `CONFIG_ARCH_KEEP_MEMBLOCK`? Ah, right, only if `CONFIG_INTEL_TDX_HOST` is also selected. But even if it's enabled or not, what exactly is this patch *doing*?

Let's dive into the modified functions. Okay, we have:

1.  `memblock_bsearch_start` - that's a static helper function, straightforward.
2.  `memblock_add_range` - that's a critical one, used by a bunch of key memblock operations: `memblock_add_node`, `memblock_add`, `__memblock_reserve`, `memblock_physmem_add`, and even `memblock_double_array` which calls `memblock_insert_region`. That's a good starting point.
3.  `memblock_isolate_range` - now let's see, who *uses* this? I need to check the callers of `memblock_isolate_range`.
4.  `memblock_search` - same question here, what calls this function? Let me check its callers too.
5.  `memblock_dump` - and finally, I need to see the callers of `memblock_dump` too.

Alright, time to roll up my sleeves and grep for those function names. Let's see how they're being utilized in the code and what context they're being used in. That will reveal the changes better.

{
  "Expression": "memblock_isolate_range",
  "PathPrefix": "mm/"
}

{
  "Output": "mm/memblock.c=795=bool __init_memblock memblock_validate_numa_coverage(unsigned long threshold_bytes)\n--\nmm/memblock.c-818-/**\nmm/memblock.c:819: * memblock_isolate_range - isolate given range into disjoint memblocks\nmm/memblock.c-820- * @type: memblock type to isolate range for\n--\nmm/memblock.c-834- */\nmm/memblock.c:835:static int __init_memblock memblock_isolate_range(struct memblock_type *type,\nmm/memblock.c-836-\t\t\t\t\tphys_addr_t base, phys_addr_t size,\n--\nmm/memblock.c=897=static int __init_memblock memblock_remove_range(struct memblock_type *type,\n--\nmm/memblock.c-902-\nmm/memblock.c:903:\tret = memblock_isolate_range(type, base, size, \u0026start_rgn, \u0026end_rgn);\nmm/memblock.c-904-\tif (ret)\n--\nmm/memblock.c=1067=static int __init_memblock memblock_setclr_flag(struct memblock_type *type,\n--\nmm/memblock.c-1071-\nmm/memblock.c:1072:\tret = memblock_isolate_range(type, base, size, \u0026start_rgn, \u0026end_rgn);\nmm/memblock.c-1073-\tif (ret)\n--\nmm/memblock.c=1514=int __init_memblock memblock_set_node(phys_addr_t base, phys_addr_t size,\n--\nmm/memblock.c-1520-\nmm/memblock.c:1521:\tret = memblock_isolate_range(type, base, size, \u0026start_rgn, \u0026end_rgn);\nmm/memblock.c-1522-\tif (ret)\n--\nmm/memblock.c=2044=void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)\n--\nmm/memblock.c-2056-\nmm/memblock.c:2057:\tret = memblock_isolate_range(\u0026memblock.memory, base, size,\nmm/memblock.c-2058-\t\t\t\t\t\t\u0026start_rgn, \u0026end_rgn);\n"
}

gemini-3.8-flash

null

null

							input: 12120
							output: 26
							thoughts: 10
						

Okay, here's my attempt at summarizing the thought process, tailored for an expert audience, and written in the first person:

**Investigating `memblock_search`**

Alright, time to dive into this. Let's start with `memblock_search`. I'm going to carefully consider the context in which it's used. My immediate thought is to consider potential memory allocation failures if I were to use a pointer to an existing memory structure, as opposed to a dynamically allocated memblock. What are the likely calls to this function? What are the success criteria? What can I ascertain from the failure conditions? I should probably check for any subtle bugs related to alignment or size calculations here - off-by-one errors are always a risk in memory-related code. I'll mentally walk through its implementation, tracing the key variables and data structures. I'll need to think about any lock-related issues. Is it thread-safe? Or do I need to explicitly add that capability to it? Next, I will think about its performance characteristics with large memory regions. Does it scale linearly, logarithmically, or perhaps worse? Are there any potential bottlenecks, like cache misses or memory barriers, that might become problematic under high loads? And finally, of course, what are the error-handling paths and how graceful are they? Is there adequate logging, and if so, can I tweak this to be more informative? Essentially, I will need to understand this function's behavior in order to safely use it in my projects.

{
  "Expression": "memblock_search",
  "PathPrefix": "mm/"
}

{
  "Output": "mm/memblock.c=2077=void __init memblock_mem_limit_remove_map(phys_addr_t limit)\n--\nmm/memblock.c-2092-\nmm/memblock.c:2093:static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)\nmm/memblock.c-2094-{\n--\nmm/memblock.c=2102=bool __init_memblock memblock_is_reserved(phys_addr_t addr)\nmm/memblock.c-2103-{\nmm/memblock.c:2104:\treturn memblock_search(\u0026memblock.reserved, addr) != -1;\nmm/memblock.c-2105-}\n--\nmm/memblock.c=2107=bool __init_memblock memblock_is_memory(phys_addr_t addr)\nmm/memblock.c-2108-{\nmm/memblock.c:2109:\treturn memblock_search(\u0026memblock.memory, addr) != -1;\nmm/memblock.c-2110-}\n--\nmm/memblock.c=2112=bool __init_memblock memblock_is_map_memory(phys_addr_t addr)\nmm/memblock.c-2113-{\nmm/memblock.c:2114:\tint i = memblock_search(\u0026memblock.memory, addr);\nmm/memblock.c-2115-\n--\nmm/memblock.c-2120-\nmm/memblock.c:2121:int __init_memblock memblock_search_pfn_nid(unsigned long pfn,\nmm/memblock.c-2122-\t\t\t unsigned long *start_pfn, unsigned long *end_pfn)\n--\nmm/memblock.c-2124-\tstruct memblock_type *type = \u0026memblock.memory;\nmm/memblock.c:2125:\tint mid = memblock_search(type, PFN_PHYS(pfn));\nmm/memblock.c-2126-\n--\nmm/memblock.c=2146=bool __init_memblock memblock_is_region_memory(phys_addr_t base, phys_addr_t size)\nmm/memblock.c-2147-{\nmm/memblock.c:2148:\tint idx = memblock_search(\u0026memblock.memory, base);\nmm/memblock.c-2149-\tphys_addr_t end = base + memblock_cap_size(base, \u0026size);\n--\nmm/mm_init.c=630=static int __meminit __early_pfn_to_nid(unsigned long pfn,\n--\nmm/mm_init.c-638-\nmm/mm_init.c:639:\tnid = memblock_search_pfn_nid(pfn, \u0026start_pfn, \u0026end_pfn);\nmm/mm_init.c-640-\tif (nid != NUMA_NO_NODE) {\n"
}

gemini-3.8-flash

null

null

							input: 13254
							output: 26
							thoughts: 10
						

Okay, here's my attempt at summarizing the thought process, tailored for an expert audience, and written in the first person:

**Diving into `memblock_dump`**

Alright, time to dig into this `memblock_dump` function. I need to refresh my understanding of how it's used and what it's really showing me. I'm going to run it and really examine the output, looking for specific memory ranges and their associated flags. What's the context where this dump is being generated? Is it during early boot, kernel initialization, or is it triggered dynamically later on? That makes a big difference. I'll be focused on how it represents the system's memory map, the allocations, and if there are any obvious fragmentation issues being highlighted. Understanding the flags is crucial. Is it showing me reserved memory, used memory, free memory, or something else entirely? The nuances are always the key, you know, and I’m going to be looking for anomalies and areas that warrant a deeper investigation. It’s also important to consider if this dump is providing a *complete* view or a partial snapshot. Finally, I'll be comparing it to other memory reports to ensure consistency and gain further insights.

{
  "Expression": "memblock_dump",
  "PathPrefix": "mm/"
}

{
  "Output": "mm/memblock.c=2203=phys_addr_t __init_memblock memblock_get_current_limit(void)\n--\nmm/memblock.c-2207-\nmm/memblock.c:2208:static void __init_memblock memblock_dump(struct memblock_type *type)\nmm/memblock.c-2209-{\n--\nmm/memblock.c-2233-\nmm/memblock.c:2234:static void __init_memblock __memblock_dump_all(void)\nmm/memblock.c-2235-{\n--\nmm/memblock.c-2240-\nmm/memblock.c:2241:\tmemblock_dump(\u0026memblock.memory);\nmm/memblock.c:2242:\tmemblock_dump(\u0026memblock.reserved);\nmm/memblock.c-2243-#ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP\nmm/memblock.c:2244:\tmemblock_dump(\u0026physmem);\nmm/memblock.c-2245-#endif\n--\nmm/memblock.c-2247-\nmm/memblock.c:2248:void __init_memblock memblock_dump_all(void)\nmm/memblock.c-2249-{\nmm/memblock.c-2250-\tif (memblock_debug)\nmm/memblock.c:2251:\t\t__memblock_dump_all();\nmm/memblock.c-2252-}\n"
}

gemini-3.8-flash

null

null

							input: 13949
							output: 26
							thoughts: 131
						

**Investigating Potential Post-Boot Kernel Memory Manipulation**

Okay, hold on a second! Before I dive too deep, I need to take a step back and make sure I'm not barking up the wrong tree. The core question is: can any of this memory management stuff, specifically the `memblock` operations, be reached *after* the kernel has already booted? I'm thinking about fuzzing and whether `syzkaller` could potentially trigger these functions. It's crucial to confirm that before I waste time going down a rabbit hole.

Right, let's focus on that `memblock` and its interaction with potential system calls or operations that occur during runtime. Let me see... I recall seeing some relevant functions in `mm/memory_hotplug.c`. Specifically, I think I remember seeing `memblock_remove(start, size)` along with `memblock_add_node` and potentially `memblock_physmem_add`. The key here is to determine how `memory_hotplug.c` interacts with the `memblock` functions. Does it call `memblock_add_node` or is it `memblock_add`?

Alright, time to get practical. Let's do a quick grep search through `mm/` to see where `memblock_add` is used. That should give me a good overview of the call paths to that specific function within the memory management subsystem. This should help me quickly determine if any of those call paths originate from places that syzkaller could access.

{
  "Expression": "memblock_add",
  "PathPrefix": "mm/"
}

{
  "Output": "mm/memblock.c-77- * The early architecture setup should tell memblock what the physical\nmm/memblock.c:78: * memory layout is by using memblock_add() or memblock_add_node()\nmm/memblock.c-79- * functions. The first function does not assign the region to a NUMA\n--\nmm/memblock.c-82- * later in the setup process using memblock_set_node(). The\nmm/memblock.c:83: * memblock_add_node() performs such an assignment directly.\nmm/memblock.c-84- *\n--\nmm/memblock.c=193=unsigned long __init_memblock\nmm/memblock.c:194:memblock_addrs_overlap(phys_addr_t base1, phys_addr_t size1, phys_addr_t base2,\nmm/memblock.c-195-\t\t       phys_addr_t size2)\n--\nmm/memblock.c=200=bool __init_memblock memblock_overlaps_region(struct memblock_type *type,\n--\nmm/memblock.c-207-\tfor (i = 0; i \u003c type-\u003ecnt; i++)\nmm/memblock.c:208:\t\tif (memblock_addrs_overlap(base, size, type-\u003eregions[i].base,\nmm/memblock.c-209-\t\t\t\t\t   type-\u003eregions[i].size))\n--\nmm/memblock.c=596=static int __init_memblock memblock_bsearch_start(struct memblock_type *type,\n--\nmm/memblock.c-616-/**\nmm/memblock.c:617: * memblock_add_range - add new memblock region\nmm/memblock.c-618- * @type: memblock type to add new region into\n--\nmm/memblock.c-631- */\nmm/memblock.c:632:static int __init_memblock memblock_add_range(struct memblock_type *type,\nmm/memblock.c-633-\t\t\t\tphys_addr_t base, phys_addr_t size,\n--\nmm/memblock.c-739-/**\nmm/memblock.c:740: * memblock_add_node - add new memblock region within a NUMA node\nmm/memblock.c-741- * @base: base address of the new region\n--\nmm/memblock.c-746- * Add new memblock region [@base, @base + @size) to the \"memory\"\nmm/memblock.c:747: * type. See memblock_add_range() description for mode details\nmm/memblock.c-748- *\n--\nmm/memblock.c-751- */\nmm/memblock.c:752:int __init_memblock memblock_add_node(phys_addr_t base, phys_addr_t size,\nmm/memblock.c-753-\t\t\t\t      int nid, enum memblock_flags flags)\n--\nmm/memblock.c-759-\nmm/memblock.c:760:\treturn memblock_add_range(\u0026memblock.memory, base, size, nid, flags);\nmm/memblock.c-761-}\n--\nmm/memblock.c-763-/**\nmm/memblock.c:764: * memblock_add - add new memblock region\nmm/memblock.c-765- * @base: base address of the new region\n--\nmm/memblock.c-768- * Add new memblock region [@base, @base + @size) to the \"memory\"\nmm/memblock.c:769: * type. See memblock_add_range() description for mode details\nmm/memblock.c-770- *\n--\nmm/memblock.c-773- */\nmm/memblock.c:774:int __init_memblock memblock_add(phys_addr_t base, phys_addr_t size)\nmm/memblock.c-775-{\n--\nmm/memblock.c-780-\nmm/memblock.c:781:\treturn memblock_add_range(\u0026memblock.memory, base, size, MAX_NUMNODES, 0);\nmm/memblock.c-782-}\n--\nmm/memblock.c=1032=int __init_memblock __memblock_reserve(phys_addr_t base, phys_addr_t size,\n--\nmm/memblock.c-1039-\nmm/memblock.c:1040:\treturn memblock_add_range(\u0026memblock.reserved, base, size, nid, flags);\nmm/memblock.c-1041-}\n--\nmm/memblock.c=1044=int __init_memblock memblock_physmem_add(phys_addr_t base, phys_addr_t size)\n--\nmm/memblock.c-1050-\nmm/memblock.c:1051:\treturn memblock_add_range(\u0026physmem, base, size, MAX_NUMNODES, 0);\nmm/memblock.c-1052-}\n--\nmm/memory_hotplug.c=1500=static int __add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags,\n--\nmm/memory_hotplug.c-1533-\t\t\tmemblock_flags = MEMBLOCK_DRIVER_MANAGED;\nmm/memory_hotplug.c:1534:\t\tret = memblock_add_node(start, size, nid, memblock_flags);\nmm/memory_hotplug.c-1535-\t\tif (ret)\n--\nmm/numa_memblks.c=506=int __init numa_fill_memblks(u64 start, u64 end)\n--\nmm/numa_memblks.c-520-\nmm/numa_memblks.c:521:\t\tif (memblock_addrs_overlap(start, end - start, bi-\u003estart,\nmm/numa_memblks.c-522-\t\t\t\t\t   bi-\u003eend - bi-\u003estart)) {\n"
}

gemini-3.8-flash

null

null

							input: 15976
							output: 32
							thoughts: 328
						

**Memory Hotplug and `CONFIG_ARCH_KEEP_MEMBLOCK` - A Deep Dive**

Okay, let's see, I'm looking at `mm/memory_hotplug.c` and specifically line 1534. Hmm, there's a conditional statement: `if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))`. Right, I'm thinking about memory hotplug, and I'm asking myself, can this even happen at runtime? That's the first question. Also, can this `CONFIG_ARCH_KEEP_MEMBLOCK` setting be enabled on an amd64 system? I need to check the configurations.

Let me see... I'll check `arch/x86/Kconfig`. Ah, here it is: `config INTEL_TDX_HOST`... which has a `select ARCH_KEEP_MEMBLOCK`! Okay, so `CONFIG_ARCH_KEEP_MEMBLOCK` *can* be selected on amd64, but only if `CONFIG_INTEL_TDX_HOST` is enabled. That's good to know.

Now, hold on... if we're adding with `memblock_add_node` due to this configuration, what about removing? What does `memblock_remove` do? I'll check: `mm/memory_hotplug.c:1602:	if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)` and `mm/memory_hotplug.c-1603-		memblock_remove(start, size);`. This looks like we're removing it as well. I need to refresh my memory on the implementation of `memblock_remove`. Let's go look at the implementation. I need to be sure what we're actually doing with that.

{
  "Expression": "int __init_memblock memblock_remove",
  "PathPrefix": "mm/"
}

{
  "Output": "mm/memblock.c=835=static int __init_memblock memblock_isolate_range(struct memblock_type *type,\n--\nmm/memblock.c-896-\nmm/memblock.c:897:static int __init_memblock memblock_remove_range(struct memblock_type *type,\nmm/memblock.c-898-\t\t\t\t\t  phys_addr_t base, phys_addr_t size)\n--\nmm/memblock.c-911-\nmm/memblock.c:912:int __init_memblock memblock_remove(phys_addr_t base, phys_addr_t size)\nmm/memblock.c-913-{\n"
}

gemini-3.8-flash

null

null

							input: 16911
							output: 18
							thoughts: 157
						

**My Immediate Thoughts on Memory Management**

Okay, so `memblock_remove` is really just a wrapper for `memblock_remove_range`, which then delegates to `memblock_isolate_range`. And on the other side, `memblock_add_node` seems to be using `memblock_add_range`. That's standard stuff, but now I'm starting to think about how this interacts with *hotplugging*. Can a user space process *really* trigger memory hotplug? I need to figure out the attack surface here.

I need to quickly assess how memory hotplug can be initiated. My intuition tells me to check `/sys/devices/system/memory/...`, ACPI, DAX, and virtio-mem interfaces. Are these potential entry points? Where do they interface with the core memory management? I have to consider the drivers and subsystems involved.

Specifically, I'll start by examining `drivers/virtio/virtio_mem.c`, then `drivers/base/memory.c`, and finally, of course, the heart of the matter: `mm/memory_hotplug.c`. I need to grep for instances of `add_memory` or `__add_memory` within these files to get a clearer picture of the code path. My gut tells me these functions are key, but I need to map the entry points for external memory additions. Time to dig in!

{
  "Expression": "add_memory\\("
}

{
  "Output": "arch/arm/include/asm/setup.h=20=static const struct tagtable __tagtable_##fn __tag = { tag, fn }\narch/arm/include/asm/setup.h-21-\narch/arm/include/asm/setup.h:22:extern int arm_add_memory(u64 start, u64 size);\narch/arm/include/asm/setup.h-23-extern __printf(1, 2) void early_print(const char *str, ...);\n--\narch/arm/kernel/atags_parse.c=65=static int __init parse_tag_mem32(const struct tag *tag)\narch/arm/kernel/atags_parse.c-66-{\narch/arm/kernel/atags_parse.c:67:\treturn arm_add_memory(tag-\u003eu.mem.start, tag-\u003eu.mem.size);\narch/arm/kernel/atags_parse.c-68-}\n--\narch/arm/kernel/setup.c=746=void __init dump_machine_table(void)\n--\narch/arm/kernel/setup.c-759-\narch/arm/kernel/setup.c:760:int __init arm_add_memory(u64 start, u64 size)\narch/arm/kernel/setup.c-761-{\n--\narch/arm/kernel/setup.c=826=static int __init early_mem(char *p)\n--\narch/arm/kernel/setup.c-848-\narch/arm/kernel/setup.c:849:\tarm_add_memory(start, size);\narch/arm/kernel/setup.c-850-\n--\narch/arm64/mm/mmu.c=1975=struct range arch_get_mappable_range(void)\n--\narch/arm64/mm/mmu.c-2006-\narch/arm64/mm/mmu.c:2007:int arch_add_memory(int nid, u64 start, u64 size,\narch/arm64/mm/mmu.c-2008-\t\t    struct mhp_params *params)\n--\narch/loongarch/mm/init.c=64=void __init fixrange_init(unsigned long start, unsigned long end, pgd_t *pgd_base)\n--\narch/loongarch/mm/init.c-106-#ifdef CONFIG_MEMORY_HOTPLUG\narch/loongarch/mm/init.c:107:int arch_add_memory(int nid, u64 start, u64 size, struct mhp_params *params)\narch/loongarch/mm/init.c-108-{\n--\narch/powerpc/mm/mem.c=129=int __ref add_pages(int nid, unsigned long start_pfn, unsigned long nr_pages,\n--\narch/powerpc/mm/mem.c-144-\narch/powerpc/mm/mem.c:145:int __ref arch_add_memory(int nid, u64 start, u64 size,\narch/powerpc/mm/mem.c-146-\t\t\t  struct mhp_params *params)\n--\narch/powerpc/platforms/pseries/hotplug-memory.c=564=static int dlpar_add_lmb(struct drmem_lmb *lmb)\n--\narch/powerpc/platforms/pseries/hotplug-memory.c-586-\t/* Add the memory */\narch/powerpc/platforms/pseries/hotplug-memory.c:587:\trc = __add_memory(nid, lmb-\u003ebase_addr, block_sz, MHP_MEMMAP_ON_MEMORY);\narch/powerpc/platforms/pseries/hotplug-memory.c-588-\tif (rc) {\n--\narch/riscv/mm/init.c=1712=struct range arch_get_mappable_range(void)\n--\narch/riscv/mm/init.c-1720-\narch/riscv/mm/init.c:1721:int __ref arch_add_memory(int nid, u64 start, u64 size, struct mhp_params *params)\narch/riscv/mm/init.c-1722-{\n--\narch/s390/mm/init.c=271=device_initcall(s390_cma_mem_init);\n--\narch/s390/mm/init.c-274-\narch/s390/mm/init.c:275:int arch_add_memory(int nid, u64 start, u64 size,\narch/s390/mm/init.c-276-\t\t    struct mhp_params *params)\n--\narch/x86/mm/init_64.c=963=int add_pages(int nid, unsigned long start_pfn, unsigned long nr_pages,\n--\narch/x86/mm/init_64.c-990-\narch/x86/mm/init_64.c:991:int arch_add_memory(int nid, u64 start, u64 size,\narch/x86/mm/init_64.c-992-\t\t    struct mhp_params *params)\n--\ndrivers/acpi/acpi_memhotplug.c=168=static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)\n--\ndrivers/acpi/acpi_memhotplug.c-212-\t\tmhp_flags |= MHP_MEMMAP_ON_MEMORY;\ndrivers/acpi/acpi_memhotplug.c:213:\t\tresult = __add_memory(mgid, info-\u003estart_addr, info-\u003elength,\ndrivers/acpi/acpi_memhotplug.c-214-\t\t\t\t      mhp_flags);\n--\ndrivers/acpi/acpi_memhotplug.c-216-\t\t/*\ndrivers/acpi/acpi_memhotplug.c:217:\t\t * If the memory block has been used by the kernel, add_memory()\ndrivers/acpi/acpi_memhotplug.c:218:\t\t * returns -EEXIST. If add_memory() returns the other error, it\ndrivers/acpi/acpi_memhotplug.c-219-\t\t * means that this memory block is not used by the kernel.\n--\ndrivers/acpi/acpi_memhotplug.c-232-\t\t/*\ndrivers/acpi/acpi_memhotplug.c:233:\t\t * Add num_enable even if add_memory() returns -EEXIST, so the\ndrivers/acpi/acpi_memhotplug.c-234-\t\t * device is bound to this driver.\n--\ndrivers/acpi/scan.c=2820=void __init acpi_scan_init(void)\n--\ndrivers/acpi/scan.c-2860-\t/*\ndrivers/acpi/scan.c:2861:\t * Although we call __add_memory() that is documented to require the\ndrivers/acpi/scan.c-2862-\t * device_hotplug_lock, it is not necessary here because this is an\n--\ndrivers/base/memory.c=572=static ssize_t probe_store(struct device *dev, struct device_attribute *attr,\n--\ndrivers/base/memory.c-590-\tnid = memory_add_physaddr_to_nid(phys_addr);\ndrivers/base/memory.c:591:\tret = __add_memory(nid, phys_addr,\ndrivers/base/memory.c-592-\t\t\t   MIN_MEMORY_BLOCK_SIZE * sections_per_block,\n--\ndrivers/dax/Kconfig=73=config DEV_DAX_KMEM\n--\ndrivers/dax/Kconfig-76-\tdepends on DEV_DAX\ndrivers/dax/Kconfig:77:\tdepends on MEMORY_HOTPLUG # for add_memory() and friends\ndrivers/dax/Kconfig-78-\thelp\n--\ndrivers/dax/kmem.c=163=static int dax_kmem_init_resources(struct dev_dax *dev_dax,\n--\ndrivers/dax/kmem.c-197-\t\t * Set flags appropriate for System RAM.  Leave ..._BUSY clear\ndrivers/dax/kmem.c:198:\t\t * so that add_memory() can add a child resource.  Do not\ndrivers/dax/kmem.c-199-\t\t * inherit flags from the parent since it may set new flags\ndrivers/dax/kmem.c:200:\t\t * unknown to us that will break add_memory() later.\ndrivers/dax/kmem.c-201-\t\t */\n--\ndrivers/firmware/qcom/qcom_tzmem.c=185=static void qcom_tzmem_cleanup_area(struct qcom_tzmem_area *area)\n--\ndrivers/firmware/qcom/qcom_tzmem.c-194-\ndrivers/firmware/qcom/qcom_tzmem.c:195:static int qcom_tzmem_pool_add_memory(struct qcom_tzmem_pool *pool,\ndrivers/firmware/qcom/qcom_tzmem.c-196-\t\t\t\t      size_t size, gfp_t gfp)\n--\ndrivers/firmware/qcom/qcom_tzmem.c=245=qcom_tzmem_pool_new(const struct qcom_tzmem_pool_config *config)\n--\ndrivers/firmware/qcom/qcom_tzmem.c-282-\tif (config-\u003einitial_size) {\ndrivers/firmware/qcom/qcom_tzmem.c:283:\t\tret = qcom_tzmem_pool_add_memory(pool, config-\u003einitial_size,\ndrivers/firmware/qcom/qcom_tzmem.c-284-\t\t\t\t\t\t GFP_KERNEL);\n--\ndrivers/firmware/qcom/qcom_tzmem.c=375=static bool qcom_tzmem_try_grow_pool(struct qcom_tzmem_pool *pool,\n--\ndrivers/firmware/qcom/qcom_tzmem.c-392-\ndrivers/firmware/qcom/qcom_tzmem.c:393:\treturn !qcom_tzmem_pool_add_memory(pool, requested, gfp);\ndrivers/firmware/qcom/qcom_tzmem.c-394-}\n--\ndrivers/hv/hv_balloon.c=708=static void hv_mem_hot_add(unsigned long start, unsigned long size,\n--\ndrivers/hv/hv_balloon.c-730-\t\tnid = memory_add_physaddr_to_nid(PFN_PHYS(start_pfn));\ndrivers/hv/hv_balloon.c:731:\t\tret = add_memory(nid, PFN_PHYS((start_pfn)),\ndrivers/hv/hv_balloon.c-732-\t\t\t\t HA_BYTES_IN_CHUNK, MHP_MERGE_RESOURCE);\n--\ndrivers/hv/hv_balloon.c=1692=static int hot_add_enabled(void)\n--\ndrivers/hv/hv_balloon.c-1698-\t * DM_MEM_HOT_ADD_REQUEST doesn't have the NUMA node information for\ndrivers/hv/hv_balloon.c:1699:\t * add_memory().\ndrivers/hv/hv_balloon.c-1700-\t */\n--\ndrivers/hv/hv_balloon.c=1930=static int balloon_probe(struct hv_device *dev,\n--\ndrivers/hv/hv_balloon.c-1941-\t * Hot-add must operate in chunks that are of size equal to the\ndrivers/hv/hv_balloon.c:1942:\t * memory block size because that's what the core add_memory()\ndrivers/hv/hv_balloon.c-1943-\t * interface requires. The Hyper-V interface requires that the memory\n--\ndrivers/s390/char/sclp_mem.c=189=static ssize_t sclp_config_mem_store(struct kobject *kobj, struct kobj_attribute *attr,\n--\ndrivers/s390/char/sclp_mem.c-222-\t\t * Set entire memory block CMMA state to nodat. Later, when\ndrivers/s390/char/sclp_mem.c:223:\t\t * page tables pages are allocated via __add_memory(), those\ndrivers/s390/char/sclp_mem.c-224-\t\t * regions are marked __arch_set_page_dat().\n--\ndrivers/s390/char/sclp_mem.c-226-\t\t__arch_set_page_nodat((void *)__va(addr), block_size \u003e\u003e PAGE_SHIFT);\ndrivers/s390/char/sclp_mem.c:227:\t\trc = __add_memory(0, addr, block_size,\ndrivers/s390/char/sclp_mem.c-228-\t\t\t\t  sclp_mem-\u003ememmap_on_memory ?\n--\ndrivers/virtio/virtio_mem.c=67=enum virtio_mem_sbm_mb_state {\n--\ndrivers/virtio/virtio_mem.c-69-\tVIRTIO_MEM_SBM_MB_UNUSED = 0,\ndrivers/virtio/virtio_mem.c:70:\t/* (Partially) plugged, not added to Linux. Error on add_memory(). */\ndrivers/virtio/virtio_mem.c-71-\tVIRTIO_MEM_SBM_MB_PLUGGED,\n--\ndrivers/virtio/virtio_mem.c=90=enum virtio_mem_bbm_bb_state {\n--\ndrivers/virtio/virtio_mem.c-92-\tVIRTIO_MEM_BBM_BB_UNUSED = 0,\ndrivers/virtio/virtio_mem.c:93:\t/* Plugged, not added to Linux. Error on add_memory(). */\ndrivers/virtio/virtio_mem.c-94-\tVIRTIO_MEM_BBM_BB_PLUGGED,\n--\ndrivers/virtio/virtio_mem.c=588=static int virtio_mem_sbm_sb_states_prepare_next_mb(struct virtio_mem *vm)\n--\ndrivers/virtio/virtio_mem.c-619- */\ndrivers/virtio/virtio_mem.c:620:static bool virtio_mem_could_add_memory(struct virtio_mem *vm, uint64_t size)\ndrivers/virtio/virtio_mem.c-621-{\n--\ndrivers/virtio/virtio_mem.c-635- */\ndrivers/virtio/virtio_mem.c:636:static int virtio_mem_add_memory(struct virtio_mem *vm, uint64_t addr,\ndrivers/virtio/virtio_mem.c-637-\t\t\t\t uint64_t size)\n--\ndrivers/virtio/virtio_mem.c-669-/*\ndrivers/virtio/virtio_mem.c:670: * See virtio_mem_add_memory(): Try adding a single Linux memory block.\ndrivers/virtio/virtio_mem.c-671- */\ndrivers/virtio/virtio_mem.c=672=static int virtio_mem_sbm_add_mb(struct virtio_mem *vm, unsigned long mb_id)\n--\ndrivers/virtio/virtio_mem.c-676-\ndrivers/virtio/virtio_mem.c:677:\treturn virtio_mem_add_memory(vm, addr, size);\ndrivers/virtio/virtio_mem.c-678-}\n--\ndrivers/virtio/virtio_mem.c-680-/*\ndrivers/virtio/virtio_mem.c:681: * See virtio_mem_add_memory(): Try adding a big block.\ndrivers/virtio/virtio_mem.c-682- */\ndrivers/virtio/virtio_mem.c=683=static int virtio_mem_bbm_add_bb(struct virtio_mem *vm, unsigned long bb_id)\n--\ndrivers/virtio/virtio_mem.c-687-\ndrivers/virtio/virtio_mem.c:688:\treturn virtio_mem_add_memory(vm, addr, size);\ndrivers/virtio/virtio_mem.c-689-}\n--\ndrivers/virtio/virtio_mem.c=974=static void virtio_mem_bbm_notify_cancel_offline(struct virtio_mem *vm,\n--\ndrivers/virtio/virtio_mem.c-985-/*\ndrivers/virtio/virtio_mem.c:986: * This callback will either be called synchronously from add_memory() or\ndrivers/virtio/virtio_mem.c-987- * asynchronously (e.g., triggered via user space). We have to be careful\ndrivers/virtio/virtio_mem.c:988: * with locking when calling add_memory().\ndrivers/virtio/virtio_mem.c-989- */\ndrivers/virtio/virtio_mem.c=990=static int virtio_mem_memory_notifier_cb(struct notifier_block *nb,\n--\ndrivers/virtio/virtio_mem.c-1087-\t\tif (!atomic_read(\u0026vm-\u003ewq_active) \u0026\u0026\ndrivers/virtio/virtio_mem.c:1088:\t\t    virtio_mem_could_add_memory(vm, vm-\u003eoffline_threshold / 2))\ndrivers/virtio/virtio_mem.c-1089-\t\t\tvirtio_mem_retry(vm);\n--\ndrivers/virtio/virtio_mem.c=1760=static int virtio_mem_sbm_plug_request(struct virtio_mem *vm, uint64_t diff)\n--\ndrivers/virtio/virtio_mem.c-1793-\tvirtio_mem_sbm_for_each_mb(vm, mb_id, VIRTIO_MEM_SBM_MB_UNUSED) {\ndrivers/virtio/virtio_mem.c:1794:\t\tif (!virtio_mem_could_add_memory(vm, memory_block_size_bytes()))\ndrivers/virtio/virtio_mem.c-1795-\t\t\treturn -ENOSPC;\n--\ndrivers/virtio/virtio_mem.c-1804-\twhile (nb_sb) {\ndrivers/virtio/virtio_mem.c:1805:\t\tif (!virtio_mem_could_add_memory(vm, memory_block_size_bytes()))\ndrivers/virtio/virtio_mem.c-1806-\t\t\treturn -ENOSPC;\n--\ndrivers/virtio/virtio_mem.c=1878=static int virtio_mem_bbm_plug_request(struct virtio_mem *vm, uint64_t diff)\n--\ndrivers/virtio/virtio_mem.c-1888-\tvirtio_mem_bbm_for_each_bb(vm, bb_id, VIRTIO_MEM_BBM_BB_UNUSED) {\ndrivers/virtio/virtio_mem.c:1889:\t\tif (!virtio_mem_could_add_memory(vm, vm-\u003ebbm.bb_size))\ndrivers/virtio/virtio_mem.c-1890-\t\t\treturn -ENOSPC;\n--\ndrivers/virtio/virtio_mem.c-1901-\twhile (nb_bb) {\ndrivers/virtio/virtio_mem.c:1902:\t\tif (!virtio_mem_could_add_memory(vm, vm-\u003ebbm.bb_size))\ndrivers/virtio/virtio_mem.c-1903-\t\t\treturn -ENOSPC;\n--\ndrivers/virtio/virtio_mem.c=2879=static int virtio_mem_create_resource(struct virtio_mem *vm)\n--\ndrivers/virtio/virtio_mem.c-2901-\ndrivers/virtio/virtio_mem.c:2902:\t/* The memory is not actually busy - make add_memory() work. */\ndrivers/virtio/virtio_mem.c-2903-\tvm-\u003eparent_resource-\u003eflags \u0026= ~IORESOURCE_BUSY;\n--\ndrivers/xen/balloon.c=264=static enum bp_state reserve_additional_memory(void)\n--\ndrivers/xen/balloon.c-296-        /*\ndrivers/xen/balloon.c:297:         * add_memory() will build page tables for the new memory so\ndrivers/xen/balloon.c-298-         * the p2m must contain invalid entries so the correct\n--\ninclude/linux/memory_hotplug.h=32=struct page *pfn_to_online_page(unsigned long pfn);\ninclude/linux/memory_hotplug.h-33-\ninclude/linux/memory_hotplug.h:34:/* Flags for add_memory() and friends to specify memory hotplug details. */\ninclude/linux/memory_hotplug.h-35-typedef int __bitwise mhp_t;\n--\ninclude/linux/memory_hotplug.h=123=extern int try_online_node(int nid);\ninclude/linux/memory_hotplug.h-124-\ninclude/linux/memory_hotplug.h:125:extern int arch_add_memory(int nid, u64 start, u64 size,\ninclude/linux/memory_hotplug.h-126-\t\t\t   struct mhp_params *params);\n--\ninclude/linux/memory_hotplug.h=301=int __ref free_area_init_core_hotplug(struct pglist_data *pgdat);\ninclude/linux/memory_hotplug.h:302:extern int __add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags);\ninclude/linux/memory_hotplug.h:303:extern int add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags);\ninclude/linux/memory_hotplug.h-304-extern int add_memory_resource(int nid, struct resource *resource,\n--\nmm/memory_hotplug.c=1446=static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group,\n--\nmm/memory_hotplug.c-1470-\t\t/* call arch's memory hotadd */\nmm/memory_hotplug.c:1471:\t\tret = arch_add_memory(nid, cur_start, memblock_size, \u0026params);\nmm/memory_hotplug.c-1472-\t\tif (ret \u003c 0) {\n--\nmm/memory_hotplug.c=1500=static int __add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags,\n--\nmm/memory_hotplug.c-1560-\t} else {\nmm/memory_hotplug.c:1561:\t\tret = arch_add_memory(nid, start, size, \u0026params);\nmm/memory_hotplug.c-1562-\t\tif (ret \u003c 0)\n--\nmm/memory_hotplug.c=1609=int add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)\n--\nmm/memory_hotplug.c-1615-/* requires device_hotplug_lock, see __add_memory_resource() */\nmm/memory_hotplug.c:1616:int __add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags)\nmm/memory_hotplug.c-1617-{\n--\nmm/memory_hotplug.c-1630-\nmm/memory_hotplug.c:1631:int add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags)\nmm/memory_hotplug.c-1632-{\n--\nmm/memory_hotplug.c-1635-\tlock_device_hotplug();\nmm/memory_hotplug.c:1636:\trc = __add_memory(nid, start, size, mhp_flags);\nmm/memory_hotplug.c-1637-\tunlock_device_hotplug();\n--\nmm/memremap.c=144=static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,\n--\nmm/memremap.c-203-\t * over the device memory is un-accessible thus we do not want to\nmm/memremap.c:204:\t * create a linear mapping for the memory like arch_add_memory()\nmm/memremap.c-205-\t * would do.\n--\nmm/memremap.c-208-\t * the CPU, we do want the linear mapping and thus use\nmm/memremap.c:209:\t * arch_add_memory().\nmm/memremap.c-210-\t */\n--\nmm/memremap.c-220-\nmm/memremap.c:221:\t\terror = arch_add_memory(nid, range-\u003estart, range_len(range),\nmm/memremap.c-222-\t\t\t\t\tparams);\n"
}

gemini-3.8-flash

null

null

							input: 23780
							output: 35
							thoughts: 45
						

Here's my analysis of the provided snippet, framed as my own thought process:

**Diving into `drivers/base/memory.c`**

Alright, let's get down to brass tacks. The reference points to `drivers/base/memory.c`, and specifically around line 572. I need to understand what's happening at that point in the memory management subsystem. Ah, here it is: `probe_store`. This is the function of interest. Time to zoom in and see what's going on within that function call context, especially with respect to the surrounding code, as that context is often critical. I need to understand this `probe_store` call and how it's interacting with the broader memory management infrastructure. I'll need to consider what the probe is and what is being stored. What kind of memory access pattern is being implemented here? What are the implications if this function call experiences an error?

{
  "File": "drivers/base/memory.c",
  "FirstLine": 570,
  "LineCount": 40
}

{
  "Contents": " 570:\t */\n 571:\t#ifdef CONFIG_ARCH_MEMORY_PROBE\n 572:\tstatic ssize_t probe_store(struct device *dev, struct device_attribute *attr,\n 573:\t\t\t\t   const char *buf, size_t count)\n 574:\t{\n 575:\t\tu64 phys_addr;\n 576:\t\tint nid, ret;\n 577:\t\tunsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block;\n 578:\t\n 579:\t\tret = kstrtoull(buf, 0, \u0026phys_addr);\n 580:\t\tif (ret)\n 581:\t\t\treturn ret;\n 582:\t\n 583:\t\tif (phys_addr \u0026 ((pages_per_block \u003c\u003c PAGE_SHIFT) - 1))\n 584:\t\t\treturn -EINVAL;\n 585:\t\n 586:\t\tret = lock_device_hotplug_sysfs();\n 587:\t\tif (ret)\n 588:\t\t\treturn ret;\n 589:\t\n 590:\t\tnid = memory_add_physaddr_to_nid(phys_addr);\n 591:\t\tret = __add_memory(nid, phys_addr,\n 592:\t\t\t\t   MIN_MEMORY_BLOCK_SIZE * sections_per_block,\n 593:\t\t\t\t   MHP_NONE);\n 594:\t\n 595:\t\tif (ret)\n 596:\t\t\tgoto out;\n 597:\t\n 598:\t\tret = count;\n 599:\tout:\n 600:\t\tunlock_device_hotplug();\n 601:\t\treturn ret;\n 602:\t}\n 603:\t\n 604:\tstatic DEVICE_ATTR_WO(probe);\n 605:\t#endif\n 606:\t\n 607:\t#ifdef CONFIG_MEMORY_FAILURE\n 608:\t/*\n 609:\t * Support for offlining pages of memory\n"
}

gemini-3.8-flash

null

null

							input: 24597
							output: 37
							thoughts: 47
						

Here's my analysis of the provided snippet, framed as my own thought process:

**Diving into the Memory Hotplug Code**

Okay, so I need to understand this memory hotplug situation. Let's get right to the source code. I'm going to focus my attention on `mm/memory_hotplug.c`. I'm going to start by taking a peek at line 1530 to get a feel for what the immediate context is; specifically, I want to refresh my memory on the surrounding details. To get a comprehensive understanding of the situation, I should scan the code around that line – let's say from line 1520 through 1550. That should give me the necessary information to proceed.

{
  "File": "mm/memory_hotplug.c",
  "FirstLine": 1520,
  "LineCount": 40
}

{
  "Contents": "1520:\t\t\t\treturn -EINVAL;\n1521:\t\t\tnid = group-\u003enid;\n1522:\t\t}\n1523:\t\n1524:\t\tif (!node_possible(nid)) {\n1525:\t\t\tWARN(1, \"node %d was absent from the node_possible_map\\n\", nid);\n1526:\t\t\treturn -EINVAL;\n1527:\t\t}\n1528:\t\n1529:\t\tmem_hotplug_begin();\n1530:\t\n1531:\t\tif (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {\n1532:\t\t\tif (res-\u003eflags \u0026 IORESOURCE_SYSRAM_DRIVER_MANAGED)\n1533:\t\t\t\tmemblock_flags = MEMBLOCK_DRIVER_MANAGED;\n1534:\t\t\tret = memblock_add_node(start, size, nid, memblock_flags);\n1535:\t\t\tif (ret)\n1536:\t\t\t\tgoto error_mem_hotplug_end;\n1537:\t\t}\n1538:\t\n1539:\t\tret = __try_online_node(nid, false);\n1540:\t\tif (ret \u003c 0)\n1541:\t\t\tgoto error_memblock_remove;\n1542:\t\tif (ret) {\n1543:\t\t\tnode_set_online(nid);\n1544:\t\t\tret = register_node(nid);\n1545:\t\t\tif (WARN_ON(ret)) {\n1546:\t\t\t\tnode_set_offline(nid);\n1547:\t\t\t\tgoto error_memblock_remove;\n1548:\t\t\t}\n1549:\t\t\tnew_node = true;\n1550:\t\t}\n1551:\t\n1552:\t\t/*\n1553:\t\t * Self hosted memmap array\n1554:\t\t */\n1555:\t\tif ((mhp_flags \u0026 MHP_MEMMAP_ON_MEMORY) \u0026\u0026\n1556:\t\t    mhp_supports_memmap_on_memory()) {\n1557:\t\t\tret = create_altmaps_and_memory_blocks(nid, group, start, size);\n1558:\t\t\tif (ret)\n1559:\t\t\t\tgoto error;\n"
}

gemini-3.8-flash

null

null

							input: 25421
							output: 27
							thoughts: 99
						

**Investigating Memory Hotplug Removal**

Okay, so I'm diving into this memory hotplug situation, specifically focusing on `try_remove_memory` within `mm/memory_hotplug.c`, lines 2330-2340. I see that this code snippet checks `CONFIG_ARCH_KEEP_MEMBLOCK`. Now, the crucial question is *how* is `try_remove_memory` called in the first place? I need to understand the call chain here to grasp the broader context and implications. Therefore, I need to check the callers of this particular function, and also `remove_memory`, to find out where it fits into the overall memory management scheme. That's the key to understanding its function in the architecture, and whether the observed behavior is expected.

{
  "Expression": "try_remove_memory",
  "PathPrefix": "mm/"
}

{
  "Output": "mm/memory_hotplug.c=2271=static int memory_blocks_have_altmaps(u64 start, u64 size)\n--\nmm/memory_hotplug.c-2290-\nmm/memory_hotplug.c:2291:static int try_remove_memory(u64 start, u64 size)\nmm/memory_hotplug.c-2292-{\n--\nmm/memory_hotplug.c=2353=void __remove_memory(u64 start, u64 size)\n--\nmm/memory_hotplug.c-2359-\t */\nmm/memory_hotplug.c:2360:\tif (try_remove_memory(start, size))\nmm/memory_hotplug.c-2361-\t\tBUG();\n--\nmm/memory_hotplug.c=2368=int remove_memory(u64 start, u64 size)\n--\nmm/memory_hotplug.c-2372-\tlock_device_hotplug();\nmm/memory_hotplug.c:2373:\trc = try_remove_memory(start, size);\nmm/memory_hotplug.c-2374-\tunlock_device_hotplug();\n--\nmm/memory_hotplug.c=2461=int offline_and_remove_memory_ranges(const struct range *ranges,\n--\nmm/memory_hotplug.c-2518-\tfor (i = 0; i \u003c nr_ranges; i++)\nmm/memory_hotplug.c:2519:\t\tWARN_ON_ONCE(try_remove_memory(ranges[i].start,\nmm/memory_hotplug.c-2520-\t\t\t\t\t       range_len(\u0026ranges[i])));\n"
}

gemini-3.8-flash

null

null

							input: 26160
							output: 25
							thoughts: 317
						

**Memory Removal Hypothesis**

Okay, wait a minute! Is it possible to *trigger* memory removal somehow? This is interesting, the idea of virtio-mem unplugging just hit me. The idea of virtio-mem being *plugged and unplugged* is something I need to fully explore. Now, what else am I missing?

Let's see, my gut is telling me to check `kexec_file.c`. Specifically, I'm thinking about `kexec_walk_memblock`. Alright, let's look at `kexec_file.c`, specifically line 607:

```c
#ifdef CONFIG_ARCH_KEEP_MEMBLOCK
static int kexec_walk_memblock(struct kexec_buf *kbuf,
			       int (*func)(struct resource *, void *))
{
	int ret = 0;
	u64 i;
	phys_addr_t mstart, mend;
	struct resource res = { };

	if (kbuf->image->type == KEXEC_TYPE_CRASH)
		return func(&crashk_res, kbuf);

	if (kbuf->top_down) {
		for_each_free_mem_range_reverse(i, NUMA_NO_NODE, MEMBLOCK_NONE,
						&mstart, &mend, NULL) {
```

Aha! Wait a minute... `for_each_free_mem_range_reverse` is being called from the `kexec_file_load` syscall! This is a potential attack vector! Now, what does `for_each_free_mem_range_reverse` actually *do*? I need to check its definition right away to fully understand the implications.

{
  "Expression": "for_each_free_mem_range_reverse"
}

{
  "Output": ".clang-format=71=ForEachMacros:\n--\n.clang-format-298-  - 'for_each_free_mem_range'\n.clang-format:299:  - 'for_each_free_mem_range_reverse'\n.clang-format-300-  - 'for_each_func_rsrc'\n--\ninclude/linux/memblock.h=311=void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,\n--\ninclude/linux/memblock.h-345-/**\ninclude/linux/memblock.h:346: * for_each_free_mem_range_reverse - rev-iterate through free memblock areas\ninclude/linux/memblock.h-347- * @i: u64 used as loop variable\n--\ninclude/linux/memblock.h-356- */\ninclude/linux/memblock.h:357:#define for_each_free_mem_range_reverse(i, nid, flags, p_start, p_end,\t\\\ninclude/linux/memblock.h-358-\t\t\t\t\tp_nid)\t\t\t\t\\\n--\nkernel/kexec_file.c=608=static int kexec_walk_memblock(struct kexec_buf *kbuf,\n--\nkernel/kexec_file.c-626-\tif (kbuf-\u003etop_down) {\nkernel/kexec_file.c:627:\t\tfor_each_free_mem_range_reverse(i, NUMA_NO_NODE, MEMBLOCK_NONE,\nkernel/kexec_file.c-628-\t\t\t\t\t\t\u0026mstart, \u0026mend, NULL) {\n--\nmm/memblock.c=265=__memblock_find_range_top_down(phys_addr_t start, phys_addr_t end,\n--\nmm/memblock.c-271-\nmm/memblock.c:272:\tfor_each_free_mem_range_reverse(i, nid, flags, \u0026this_start, \u0026this_end,\nmm/memblock.c-273-\t\t\t\t\tNULL) {\n"
}

gemini-3.8-flash

null

null

							input: 27419
							output: 36
							thoughts: 866
						

**Analyzing Memblock Changes**

Okay, so I'm trying to understand the impact of this patch. My initial thought was to see if `for_each_free_mem_range_reverse` was touched, specifically if it called `memblock_bsearch_start` or any of the *changed* code, but it looks like it only calls `__next_mem_range_rev`, which isn't within the patch. I need to be sure.

Now, let's carefully go through the changes. A new function, `memblock_bsearch_start`, has been added. Looking at it, it seems to perform a binary search within a `memblock_type` structure to find the index where a given base address *would* be inserted or exists. Then, I see it's being used in `memblock_add_range`, `memblock_isolate_range`, and `memblock_search`. Interestingly, it replaces the existing loop-based iteration in those functions. `memblock_dump` changed to a direct index loop.

I'm starting to see that this is a performance optimization, replacing linear searches with binary searches in several crucial memblock operations. That's a reasonable change.

I'm thinking now about how these changes might be exposed. I should check the debugfs interface and other interfaces for memblock. Does anything call `memblock_dump` or `memblock_search` or anything using the new function or the changed ones? It makes sense to check `mm/memblock.c` with `CONFIG_DEBUG_FS` enabled, to understand if any of these changes are exposed through the debug interface. I'll read through that section carefully for any potential interactions.

{
  "File": "mm/memblock.c",
  "FirstLine": 2890,
  "LineCount": 100
}

{
  "Contents": "2890:\t\tpr_err(\"reserve_mem: empty or malformed parameter\\n\");\n2891:\t\treturn -EINVAL;\n2892:\t}\n2893:\t__setup(\"reserve_mem=\", reserve_mem);\n2894:\t\n2895:\t#ifdef CONFIG_DEBUG_FS\n2896:\t#ifdef CONFIG_ARCH_KEEP_MEMBLOCK\n2897:\tstatic const char * const flagname[] = {\n2898:\t\t[ilog2(MEMBLOCK_HOTPLUG)] = \"HOTPLUG\",\n2899:\t\t[ilog2(MEMBLOCK_MIRROR)] = \"MIRROR\",\n2900:\t\t[ilog2(MEMBLOCK_NOMAP)] = \"NOMAP\",\n2901:\t\t[ilog2(MEMBLOCK_DRIVER_MANAGED)] = \"DRV_MNG\",\n2902:\t\t[ilog2(MEMBLOCK_RSRV_NOINIT)] = \"RSV_NIT\",\n2903:\t\t[ilog2(MEMBLOCK_RSRV_KERN)] = \"RSV_KERN\",\n2904:\t\t[ilog2(MEMBLOCK_KHO_NOPRSRV)] = \"KHO_NOPRSRV\",\n2905:\t};\n2906:\t\n2907:\tstatic int memblock_debug_show(struct seq_file *m, void *private)\n2908:\t{\n2909:\t\tstruct memblock_type *type = m-\u003eprivate;\n2910:\t\tstruct memblock_region *reg;\n2911:\t\tint i, j, nid;\n2912:\t\tunsigned int count = ARRAY_SIZE(flagname);\n2913:\t\tphys_addr_t end;\n2914:\t\n2915:\t\tfor (i = 0; i \u003c type-\u003ecnt; i++) {\n2916:\t\t\treg = \u0026type-\u003eregions[i];\n2917:\t\t\tend = reg-\u003ebase + reg-\u003esize - 1;\n2918:\t\t\tnid = memblock_get_region_node(reg);\n2919:\t\n2920:\t\t\tseq_printf(m, \"%4d: \", i);\n2921:\t\t\tseq_printf(m, \"%pa..%pa \", \u0026reg-\u003ebase, \u0026end);\n2922:\t\t\tif (numa_valid_node(nid))\n2923:\t\t\t\tseq_printf(m, \"%4d \", nid);\n2924:\t\t\telse\n2925:\t\t\t\tseq_printf(m, \"%4c \", 'x');\n2926:\t\t\tif (reg-\u003eflags) {\n2927:\t\t\t\tfor (j = 0; j \u003c count; j++) {\n2928:\t\t\t\t\tif (reg-\u003eflags \u0026 (1U \u003c\u003c j)) {\n2929:\t\t\t\t\t\tseq_printf(m, \"%s\\n\", flagname[j]);\n2930:\t\t\t\t\t\tbreak;\n2931:\t\t\t\t\t}\n2932:\t\t\t\t}\n2933:\t\t\t\tif (j == count)\n2934:\t\t\t\t\tseq_printf(m, \"%s\\n\", \"UNKNOWN\");\n2935:\t\t\t} else {\n2936:\t\t\t\tseq_printf(m, \"%s\\n\", \"NONE\");\n2937:\t\t\t}\n2938:\t\t}\n2939:\t\treturn 0;\n2940:\t}\n2941:\tDEFINE_SHOW_ATTRIBUTE(memblock_debug);\n2942:\t\n2943:\tstatic inline void memblock_debugfs_expose_arrays(struct dentry *root)\n2944:\t{\n2945:\t\tdebugfs_create_file(\"memory\", 0444, root,\n2946:\t\t\t\t    \u0026memblock.memory, \u0026memblock_debug_fops);\n2947:\t\tdebugfs_create_file(\"reserved\", 0444, root,\n2948:\t\t\t\t    \u0026memblock.reserved, \u0026memblock_debug_fops);\n2949:\t#ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP\n2950:\t\tdebugfs_create_file(\"physmem\", 0444, root, \u0026physmem,\n2951:\t\t\t\t    \u0026memblock_debug_fops);\n2952:\t#endif\n2953:\t}\n2954:\t\n2955:\t#else\n2956:\t\n2957:\tstatic inline void memblock_debugfs_expose_arrays(struct dentry *root) { }\n2958:\t\n2959:\t#endif /* CONFIG_ARCH_KEEP_MEMBLOCK */\n2960:\t\n2961:\tstatic int memblock_reserve_mem_show(struct seq_file *m, void *private)\n2962:\t{\n2963:\t\tstruct reserve_mem_table *map;\n2964:\t\tchar txtsz[16];\n2965:\t\n2966:\t\tguard(mutex)(\u0026reserve_mem_lock);\n2967:\t\tfor (int i = 0; i \u003c reserved_mem_count; i++) {\n2968:\t\t\tmap = \u0026reserved_mem_table[i];\n2969:\t\t\tif (!map-\u003esize)\n2970:\t\t\t\tcontinue;\n2971:\t\n2972:\t\t\tmemset(txtsz, 0, sizeof(txtsz));\n2973:\t\t\tstring_get_size(map-\u003esize, 1, STRING_UNITS_2, txtsz, sizeof(txtsz));\n2974:\t\t\tseq_printf(m, \"%s\\t\\t(%s)\\n\", map-\u003ename, txtsz);\n2975:\t\t}\n2976:\t\n2977:\t\treturn 0;\n2978:\t}\n2979:\tDEFINE_SHOW_ATTRIBUTE(memblock_reserve_mem);\n2980:\t\n2981:\tstatic int __init memblock_init_debugfs(void)\n2982:\t{\n2983:\t\tstruct dentry *root;\n2984:\t\n2985:\t\tif (!IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK) \u0026\u0026 !reserved_mem_count)\n2986:\t\t\treturn 0;\n2987:\t\n2988:\t\troot = debugfs_create_dir(\"memblock\", NULL);\n2989:\t\n"
}

gemini-3.8-flash

null

null

							input: 30290
							output: 19
							thoughts: 430
						

**Analyzing the Call Chains of Modified `memblock` Functions**

Okay, let's break this down. My initial focus is on understanding the impact of these changes. I need to know how the functions I've touched, specifically `memblock_bsearch_start`, `memblock_add_range`, `memblock_isolate_range`, `memblock_search`, and `memblock_dump`, are used within the kernel. I've already identified the direct call sites for each.

First, I see that `memblock_bsearch_start` is only called by a small set of functions: `memblock_add_range`, `memblock_isolate_range`, and `memblock_search`. That simplifies things.

Next, `memblock_add_range` is a static function in `mm/memblock.c`. It's called by `memblock_add_node`, `memblock_add`, `__memblock_reserve`, and `memblock_physmem_add`. A good list to keep an eye on.

`memblock_isolate_range`, another static function, is called by `memblock_remove_range`, `memblock_setclr_flag`, `memblock_set_node`, and `memblock_cap_memory_range`. Got it.

`memblock_search` is used by quite a few routines: `memblock_is_reserved`, `memblock_is_memory`, `memblock_is_map_memory`, `memblock_search_pfn_nid`, and `memblock_is_region_memory`.

Finally, `memblock_dump` is a static function, called through `__memblock_dump_all` and subsequently by `memblock_dump_all`, which is only reached if `memblock_debug` is set during boot. That's a good sanity check, but likely not a runtime concern.

Now, the critical question: are any of these call chains *active* after boot? Are any of the modified functions actually hit at runtime? I need to focus on the ones that might. I'll start by checking all of the calls to `memblock_add(`, to see if that's happening during normal operation of the kernel. A grep should give me the answers.

{
  "Expression": "memblock_add\\("
}

{
  "Output": "\nFull output is too long, showing 500 out of 590 lines.\nUse more precise expression if possible.\n\narch/alpha/kernel/setup.c=286=setup_memory(void *kernel_end)\n--\narch/alpha/kernel/setup.c-307-\narch/alpha/kernel/setup.c:308:\t\tmemblock_add(PFN_PHYS(cluster-\u003estart_pfn),\narch/alpha/kernel/setup.c-309-\t\t\t     cluster-\u003enumpages \u003c\u003c PAGE_SHIFT);\n--\narch/arm/kernel/setup.c=760=int __init arm_add_memory(u64 start, u64 size)\n--\narch/arm/kernel/setup.c-816-\narch/arm/kernel/setup.c:817:\tmemblock_add(start, size);\narch/arm/kernel/setup.c-818-\treturn 0;\n--\narch/arm/mach-pxa/spitz.c=1134=static void __init spitz_fixup(struct tag *tags, char **cmdline)\n--\narch/arm/mach-pxa/spitz.c-1136-\tsharpsl_save_param();\narch/arm/mach-pxa/spitz.c:1137:\tmemblock_add(0xa0000000, SZ_64M);\narch/arm/mach-pxa/spitz.c-1138-}\n--\narch/arm64/mm/init.c=196=void __init arm64_memblock_init(void)\n--\narch/arm64/mm/init.c-256-\t\tmemblock_mem_limit_remove_map(memory_limit);\narch/arm64/mm/init.c:257:\t\tmemblock_add(__pa_symbol(_text), (resource_size_t)(_end - _text));\narch/arm64/mm/init.c-258-\t}\n--\narch/arm64/mm/init.c-282-\t\t} else {\narch/arm64/mm/init.c:283:\t\t\tmemblock_add(base, size);\narch/arm64/mm/init.c-284-\t\t\tmemblock_clear_nomap(base, size);\n--\narch/hexagon/mm/init.c=104=void __init setup_arch_memory(void)\n--\narch/hexagon/mm/init.c-123-\narch/hexagon/mm/init.c:124:\tmemblock_add(PHYS_OFFSET,\narch/hexagon/mm/init.c-125-\t\t     (bootmem_lastpg - ARCH_PFN_OFFSET) \u003c\u003c PAGE_SHIFT);\n--\narch/loongarch/kernel/mem.c=13=void __init memblock_init(void)\n--\narch/loongarch/kernel/mem.c-31-\t\tcase EFI_CONVENTIONAL_MEMORY:\narch/loongarch/kernel/mem.c:32:\t\t\tmemblock_add(mem_start, mem_size);\narch/loongarch/kernel/mem.c-33-\t\t\tbreak;\n--\narch/loongarch/kernel/mem.c-36-\t\tcase EFI_ACPI_RECLAIM_MEMORY:\narch/loongarch/kernel/mem.c:37:\t\t\tmemblock_add(mem_start, mem_size);\narch/loongarch/kernel/mem.c-38-\t\t\tfallthrough;\n--\narch/loongarch/kernel/setup.c=191=static int __init early_parse_mem(char *p)\n--\narch/loongarch/kernel/setup.c-221-\tif (!IS_ENABLED(CONFIG_NUMA))\narch/loongarch/kernel/setup.c:222:\t\tmemblock_add(start, size);\narch/loongarch/kernel/setup.c-223-\telse\n--\narch/loongarch/kernel/setup.c=380=static void __init check_kernel_sections_mem(void)\n--\narch/loongarch/kernel/setup.c-386-\t\tpr_info(\"Kernel sections are not in the memory maps\\n\");\narch/loongarch/kernel/setup.c:387:\t\tmemblock_add(start, size);\narch/loongarch/kernel/setup.c-388-\t}\n--\narch/m68k/kernel/setup_no.c=82=void __init setup_arch(char **cmdline_p)\n--\narch/m68k/kernel/setup_no.c-142-\narch/m68k/kernel/setup_no.c:143:\tmemblock_add(_rambase, memory_end - _rambase);\narch/m68k/kernel/setup_no.c-144-\tmemblock_reserve(_rambase, memory_start - _rambase);\n--\narch/mips/alchemy/common/prom.c=83=void __init prom_init(void)\n--\narch/mips/alchemy/common/prom.c-97-\narch/mips/alchemy/common/prom.c:98:\tmemblock_add(0, memsize);\narch/mips/alchemy/common/prom.c-99-}\n--\narch/mips/ath25/ar2315.c=255=void __init ar2315_plat_mem_setup(void)\n--\narch/mips/ath25/ar2315.c-269-\tmemsize \u003c\u003c= 3;\narch/mips/ath25/ar2315.c:270:\tmemblock_add(0, memsize);\narch/mips/ath25/ar2315.c-271-\tiounmap(sdram_base);\n--\narch/mips/ath25/ar5312.c=351=void __init ar5312_plat_mem_setup(void)\n--\narch/mips/ath25/ar5312.c-365-\tmemsize \u003c\u003c= 20;\narch/mips/ath25/ar5312.c:366:\tmemblock_add(0, memsize);\narch/mips/ath25/ar5312.c-367-\tiounmap(sdram_base);\n--\narch/mips/bcm47xx/prom.c=58=static __init void prom_init_mem(void)\n--\narch/mips/bcm47xx/prom.c-102-\t\tmem -= 0x1000;\narch/mips/bcm47xx/prom.c:103:\tmemblock_add(0, mem);\narch/mips/bcm47xx/prom.c-104-}\n--\narch/mips/bcm63xx/setup.c=155=void __init plat_mem_setup(void)\narch/mips/bcm63xx/setup.c-156-{\narch/mips/bcm63xx/setup.c:157:\tmemblock_add(0, bcm63xx_get_memory_size());\narch/mips/bcm63xx/setup.c-158-\n--\narch/mips/cavium-octeon/setup.c=928=static __init void memory_exclude_page(u64 addr, u64 *mem, u64 *size)\n--\narch/mips/cavium-octeon/setup.c-931-\t\tu64 inc = addr - *mem;\narch/mips/cavium-octeon/setup.c:932:\t\tmemblock_add(*mem, inc);\narch/mips/cavium-octeon/setup.c-933-\t\t*mem += inc;\n--\narch/mips/cavium-octeon/setup.c=967=void __init plat_mem_setup(void)\n--\narch/mips/cavium-octeon/setup.c-991-#ifdef CONFIG_CRASH_DUMP\narch/mips/cavium-octeon/setup.c:992:\tmemblock_add(reserve_low_mem, max_memory);\narch/mips/cavium-octeon/setup.c-993-\ttotal += max_memory;\n--\narch/mips/cavium-octeon/setup.c-996-\tif (crashk_size \u003e 0) {\narch/mips/cavium-octeon/setup.c:997:\t\tmemblock_add(crashk_base, crashk_size);\narch/mips/cavium-octeon/setup.c-998-\t\tcrashk_end = crashk_base + crashk_size;\n--\narch/mips/cavium-octeon/setup.c-1037-\t\t\t\t/* region is fully in */\narch/mips/cavium-octeon/setup.c:1038:\t\t\t\tmemblock_add(memory, crashk_base - memory);\narch/mips/cavium-octeon/setup.c-1039-\t\t\t\ttotal += crashk_base - memory;\narch/mips/cavium-octeon/setup.c:1040:\t\t\t\tmemblock_add(crashk_end, end - crashk_end);\narch/mips/cavium-octeon/setup.c-1041-\t\t\t\ttotal += end - crashk_end;\n--\narch/mips/cavium-octeon/setup.c-1067-#endif\narch/mips/cavium-octeon/setup.c:1068:\t\t\tmemblock_add(memory, mem_alloc_size);\narch/mips/cavium-octeon/setup.c-1069-\t\t\ttotal += mem_alloc_size;\n--\narch/mips/cobalt/setup.c=97=void __init prom_init(void)\n--\narch/mips/cobalt/setup.c-112-\narch/mips/cobalt/setup.c:113:\tmemblock_add(0, memsz);\narch/mips/cobalt/setup.c-114-\n--\narch/mips/dec/prom/memory.c=30=static __init void pmax_setup_memory_region(void)\n--\narch/mips/dec/prom/memory.c-51-\narch/mips/dec/prom/memory.c:52:\tmemblock_add(0, (unsigned long)memory_page - CKSEG1 - CHUNK_SIZE);\narch/mips/dec/prom/memory.c-53-}\n--\narch/mips/dec/prom/memory.c=59=static __init void rex_setup_memory_region(void)\n--\narch/mips/dec/prom/memory.c-76-\t\telse {\narch/mips/dec/prom/memory.c:77:\t\t\tmemblock_add(mem_start, mem_size);\narch/mips/dec/prom/memory.c-78-\t\t\tmem_start += mem_size + (8 * bm-\u003epagesize);\n--\narch/mips/dec/prom/memory.c-82-\tif (mem_size)\narch/mips/dec/prom/memory.c:83:\t\tmemblock_add(mem_start, mem_size);\narch/mips/dec/prom/memory.c-84-}\n--\narch/mips/fw/arc/memory.c=123=void __weak __init prom_meminit(void)\n--\narch/mips/fw/arc/memory.c-153-\narch/mips/fw/arc/memory.c:154:\t\tmemblock_add(base, size);\narch/mips/fw/arc/memory.c-155-\n--\narch/mips/fw/sni/sniprom.c=100=static void __init sni_mem_init(void)\n--\narch/mips/fw/sni/sniprom.c-130-\t\t\tmemconf[i].size, memconf[i].base);\narch/mips/fw/sni/sniprom.c:131:\t\tmemblock_add(memconf[i].base, memconf[i].size);\narch/mips/fw/sni/sniprom.c-132-\t}\n--\narch/mips/kernel/setup.c=98=void __init detect_memory_region(phys_addr_t start, phys_addr_t sz_min, phys_addr_t sz_max)\n--\narch/mips/kernel/setup.c-113-\narch/mips/kernel/setup.c:114:\tmemblock_add(start, size);\narch/mips/kernel/setup.c-115-}\n--\narch/mips/kernel/setup.c=346=static int __init early_parse_mem(char *p)\n--\narch/mips/kernel/setup.c-372-\telse\narch/mips/kernel/setup.c:373:\t\tmemblock_add(start, size);\narch/mips/kernel/setup.c-374-\n--\narch/mips/kernel/setup.c=379=static int __init early_parse_memmap(char *p)\n--\narch/mips/kernel/setup.c-398-\t\tstart_at = memparse(p+1, \u0026p);\narch/mips/kernel/setup.c:399:\t\tmemblock_add(start_at, mem_size);\narch/mips/kernel/setup.c-400-\t} else if (*p == '#') {\n--\narch/mips/kernel/setup.c-404-\t\tstart_at = memparse(p+1, \u0026p);\narch/mips/kernel/setup.c:405:\t\tmemblock_add(start_at, mem_size);\narch/mips/kernel/setup.c-406-\t\tmemblock_reserve(start_at, mem_size);\n--\narch/mips/kernel/setup.c=508=static void __init check_kernel_sections_mem(void)\n--\narch/mips/kernel/setup.c-514-\t\tpr_info(\"Kernel sections are not in the memory maps\\n\");\narch/mips/kernel/setup.c:515:\t\tmemblock_add(start, size);\narch/mips/kernel/setup.c-516-\t}\n--\narch/mips/loongson2ef/common/mem.c=18=void __init prom_init_memory(void)\narch/mips/loongson2ef/common/mem.c-19-{\narch/mips/loongson2ef/common/mem.c:20:\tmemblock_add(0x0, (memsize \u003c\u003c 20));\narch/mips/loongson2ef/common/mem.c-21-\n--\narch/mips/loongson2ef/common/mem.c-40-\tif (highmemsize \u003e 0)\narch/mips/loongson2ef/common/mem.c:41:\t\tmemblock_add(LOONGSON_HIGHMEM_START, highmemsize \u003c\u003c 20);\narch/mips/loongson2ef/common/mem.c-42-#endif /* !CONFIG_64BIT */\n--\narch/mips/n64/init.c=154=void __init plat_mem_setup(void)\n--\narch/mips/n64/init.c-156-\tiomem_resource_init();\narch/mips/n64/init.c:157:\tmemblock_add(0x0, 8 * 1024 * 1024); /* Bootloader blocks the 4mb config */\narch/mips/n64/init.c-158-}\n--\narch/mips/ralink/mt7621.c=77=static void __init mt7621_memory_detect(void)\n--\narch/mips/ralink/mt7621.c-82-\t\tif (mt7621_addr_wraparound_test(size)) {\narch/mips/ralink/mt7621.c:83:\t\t\tmemblock_add(MT7621_LOWMEM_BASE, size);\narch/mips/ralink/mt7621.c-84-\t\t\treturn;\n--\narch/mips/ralink/mt7621.c-87-\narch/mips/ralink/mt7621.c:88:\tmemblock_add(MT7621_LOWMEM_BASE, MT7621_LOWMEM_MAX_SIZE);\narch/mips/ralink/mt7621.c:89:\tmemblock_add(MT7621_HIGHMEM_BASE, MT7621_HIGHMEM_SIZE);\narch/mips/ralink/mt7621.c-90-}\n--\narch/mips/ralink/of.c=87=void __init plat_mem_setup(void)\n--\narch/mips/ralink/of.c-105-\telse if (soc_info.mem_size)\narch/mips/ralink/of.c:106:\t\tmemblock_add(soc_info.mem_base, soc_info.mem_size * SZ_1M);\narch/mips/ralink/of.c-107-\telse\n--\narch/mips/rb532/prom.c=102=void __init prom_init(void)\n--\narch/mips/rb532/prom.c-123-\t * except for the first 0x400 and the last 0x200 bytes */\narch/mips/rb532/prom.c:124:\tmemblock_add(ddrbase + 0x400, memsize - 0x600);\narch/mips/rb532/prom.c-125-}\n--\narch/mips/sgi-ip22/ip22-mc.c=53=static void __init probe_memory(void)\n--\narch/mips/sgi-ip22/ip22-mc.c-69-\t\tif (addr \u003e= SGIMC_SEG1_BADDR)\narch/mips/sgi-ip22/ip22-mc.c:70:\t\t\tmemblock_add(addr, size);\narch/mips/sgi-ip22/ip22-mc.c-71-\t}\n--\narch/mips/sgi-ip32/ip32-memory.c=22=void __init prom_meminit(void)\n--\narch/mips/sgi-ip32/ip32-memory.c-40-\t\t\tbank, base, size \u003e\u003e 20);\narch/mips/sgi-ip32/ip32-memory.c:41:\t\tmemblock_add(base, size);\narch/mips/sgi-ip32/ip32-memory.c-42-\t}\n--\narch/mips/sibyte/common/cfe.c=79=static __init void prom_meminit(void)\n--\narch/mips/sibyte/common/cfe.c-110-\t\t\t\t    (initrd_pstart \u003c (addr + size))) {\narch/mips/sibyte/common/cfe.c:111:\t\t\t\t\tmemblock_add(addr,\narch/mips/sibyte/common/cfe.c-112-\t\t\t\t\t\t     initrd_pstart - addr);\n--\narch/mips/sibyte/common/cfe.c-116-\t\t\t\t    (initrd_pend \u003c (addr + size))) {\narch/mips/sibyte/common/cfe.c:117:\t\t\t\t\tmemblock_add(initrd_pend,\narch/mips/sibyte/common/cfe.c-118-\t\t\t\t\t\t(addr + size) - initrd_pend);\n--\narch/mips/sibyte/common/cfe.c-136-\t\t\t\t\tsize -= 512;\narch/mips/sibyte/common/cfe.c:137:\t\t\t\tmemblock_add(addr, size);\narch/mips/sibyte/common/cfe.c-138-\t\t\t}\n--\narch/mips/sibyte/common/cfe.c-142-\tif (initrd_start) {\narch/mips/sibyte/common/cfe.c:143:\t\tmemblock_add(initrd_pstart, initrd_pend - initrd_pstart);\narch/mips/sibyte/common/cfe.c-144-\t\tmemblock_reserve(initrd_pstart, initrd_pend - initrd_pstart);\n--\narch/mips/txx9/rbtx4927/prom.c=38=void __init rbtx4927_prom_init(void)\narch/mips/txx9/rbtx4927/prom.c-39-{\narch/mips/txx9/rbtx4927/prom.c:40:\tmemblock_add(0, tx4927_get_mem_size());\narch/mips/txx9/rbtx4927/prom.c-41-\ttxx9_sio_putchar_init(TX4927_SIO_REG(0) \u0026 0xfffffffffULL);\n--\narch/parisc/mm/init.c=112=static void __init setup_bootmem(void)\n--\narch/parisc/mm/init.c-260-\t\t/* add system RAM memblock */\narch/parisc/mm/init.c:261:\t\tmemblock_add(start, size);\narch/parisc/mm/init.c-262-\n--\narch/powerpc/kernel/prom.c=528=static int  __init early_init_drmem_lmb(struct drmem_lmb *lmb,\n--\narch/powerpc/kernel/prom.c-579-\t\tDBG(\"Adding: %llx -\u003e %llx\\n\", base, size);\narch/powerpc/kernel/prom.c:580:\t\tmemblock_add(base, size);\narch/powerpc/kernel/prom.c-581-\n--\narch/powerpc/kernel/prom.c=590=static int __init early_init_dt_scan_memory_ppc(void)\n--\narch/powerpc/kernel/prom.c-608- * we just want to get the memstart_address and would not like to mess the\narch/powerpc/kernel/prom.c:609: * memblock at this stage. So introduce a variable to skip the memblock_add()\narch/powerpc/kernel/prom.c-610- * for this reason.\n--\narch/powerpc/kernel/prom.c=618=void __init early_init_dt_add_memory_arch(u64 base, u64 size)\n--\narch/powerpc/kernel/prom.c-639-\t\tif (validate_mem_limit(base, \u0026size))\narch/powerpc/kernel/prom.c:640:\t\t\tmemblock_add(base, size);\narch/powerpc/kernel/prom.c-641-\t}\n--\narch/powerpc/platforms/ps3/mm.c=1202=void __init ps3_mm_init(void)\n--\narch/powerpc/platforms/ps3/mm.c-1239-\t\t\tmap.total - map.rm.size);\narch/powerpc/platforms/ps3/mm.c:1240:\t\tmemblock_add(map.rm.size, map.total - map.rm.size);\narch/powerpc/platforms/ps3/mm.c-1241-\t}\n--\narch/powerpc/platforms/pseries/hotplug-memory.c=866=static int pseries_add_mem_node(struct device_node *np)\n--\narch/powerpc/platforms/pseries/hotplug-memory.c-886-\t */\narch/powerpc/platforms/pseries/hotplug-memory.c:887:\tret = memblock_add(res.start, resource_size(\u0026res));\narch/powerpc/platforms/pseries/hotplug-memory.c-888-\treturn (ret \u003c 0) ? -EINVAL : 0;\n--\narch/s390/kernel/setup.c=703=static void __init memblock_add_physmem_info(void)\n--\narch/s390/kernel/setup.c-712-\tfor_each_physmem_usable_range(i, \u0026start, \u0026end)\narch/s390/kernel/setup.c:713:\t\tmemblock_add(start, end - start);\narch/s390/kernel/setup.c-714-\tfor_each_physmem_online_range(i, \u0026start, \u0026end)\n--\narch/sh/mm/init.c=36=void __init generic_mem_init(void)\narch/sh/mm/init.c-37-{\narch/sh/mm/init.c:38:\tmemblock_add(__MEMORY_START, __MEMORY_SIZE);\narch/sh/mm/init.c-39-}\n--\narch/sh/mm/numa.c=23=void __init setup_bootmem_node(int nid, unsigned long start, unsigned long end)\n--\narch/sh/mm/numa.c-35-\narch/sh/mm/numa.c:36:\tmemblock_add(start, end - start);\narch/sh/mm/numa.c-37-\n--\narch/sparc/mm/init_32.c=131=unsigned long __init bootmem_init(unsigned long *pages_avail)\n--\narch/sparc/mm/init_32.c-156-\t\t\t\t} else {\narch/sparc/mm/init_32.c:157:\t\t\t\t\tmemblock_add(sp_banks[i].base_addr,\narch/sparc/mm/init_32.c-158-\t\t\t\t\t\t     sp_banks[i].num_bytes);\n--\narch/sparc/mm/init_32.c-164-\t\t}\narch/sparc/mm/init_32.c:165:\t\tmemblock_add(sp_banks[i].base_addr, sp_banks[i].num_bytes);\narch/sparc/mm/init_32.c-166-\t}\n--\narch/sparc/mm/init_32.c-193-\tmemblock_reserve(phys_base, size);\narch/sparc/mm/init_32.c:194:\tmemblock_add(phys_base, size);\narch/sparc/mm/init_32.c-195-\n--\narch/sparc/mm/init_64.c=2275=void __init paging_init(void)\n--\narch/sparc/mm/init_64.c-2366-\t\tphys_base = min(phys_base, pavail[i].phys_addr);\narch/sparc/mm/init_64.c:2367:\t\tmemblock_add(pavail[i].phys_addr, pavail[i].reg_size);\narch/sparc/mm/init_64.c-2368-\t}\n--\narch/um/kernel/physmem.c=62=void __init setup_physmem(unsigned long start, unsigned long reserve_end,\n--\narch/um/kernel/physmem.c-92-\narch/um/kernel/physmem.c:93:\tmemblock_add(__pa(start), len);\narch/um/kernel/physmem.c-94-\tmemblock_reserve(__pa(start), reserve);\n--\narch/x86/kernel/e820.c=1288=__init void e820__memblock_setup(void)\n--\narch/x86/kernel/e820.c-1346-\narch/x86/kernel/e820.c:1347:\t\tmemblock_add(entry-\u003eaddr, entry-\u003esize);\narch/x86/kernel/e820.c-1348-\t}\n--\narch/xtensa/kernel/setup.c=91=static int __init parse_tag_mem(const bp_tag_t *tag)\n--\narch/xtensa/kernel/setup.c-97-\narch/xtensa/kernel/setup.c:98:\treturn memblock_add(mi-\u003estart, mi-\u003eend - mi-\u003estart);\narch/xtensa/kernel/setup.c-99-}\n--\narch/xtensa/mm/init.c=132=static void __init parse_memmap_one(char *p)\n--\narch/xtensa/mm/init.c-147-\t\tstart_at = memparse(p + 1, \u0026p);\narch/xtensa/mm/init.c:148:\t\tmemblock_add(start_at, mem_size);\narch/xtensa/mm/init.c-149-\t\tbreak;\n--\ndrivers/firmware/efi/efi-init.c=233=void __init efi_init(void)\n--\ndrivers/firmware/efi/efi-init.c-262-\t/*\ndrivers/firmware/efi/efi-init.c:263:\t * For memblock manipulation, the cap should come after the memblock_add().\ndrivers/firmware/efi/efi-init.c-264-\t * And now, memblock is fully populated, it is time to do capping.\n--\ndrivers/firmware/efi/efi.c=655=static __init int match_config_table(const efi_guid_t *guid,\n--\ndrivers/firmware/efi/efi.c-684- *\ndrivers/firmware/efi/efi.c:685: * memblock_add() makes sure that the table is mapped in direct mapping. During\ndrivers/firmware/efi/efi.c-686- * normal boot it happens automatically because the table is allocated from\ndrivers/firmware/efi/efi.c-687- * usable memory. But during crashkernel boot only memory specifically reserved\ndrivers/firmware/efi/efi.c:688: * for crash scenario is mapped. memblock_add() forces the table to be mapped\ndrivers/firmware/efi/efi.c-689- * in crashkernel case.\n--\ndrivers/firmware/efi/efi.c=698=static __init void reserve_unaccepted(struct efi_unaccepted_memory *unaccepted)\n--\ndrivers/firmware/efi/efi.c-704-\ndrivers/firmware/efi/efi.c:705:\tmemblock_add(start, end - start);\ndrivers/firmware/efi/efi.c-706-\tmemblock_reserve(start, end - start);\n--\ndrivers/of/fdt.c=892=void __init early_init_dt_check_for_usable_mem_range(void)\n--\ndrivers/of/fdt.c-922-\tfor (i = 1; i \u003c MAX_USABLE_RANGES \u0026\u0026 rgn[i].size; i++)\ndrivers/of/fdt.c:923:\t\tmemblock_add(rgn[i].base, rgn[i].size);\ndrivers/of/fdt.c-924-}\n--\ndrivers/of/fdt.c=1159=void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)\n--\ndrivers/of/fdt.c-1197-\t}\ndrivers/of/fdt.c:1198:\tmemblock_add(base, size);\ndrivers/of/fdt.c-1199-}\n--\ninclude/linux/memblock.h=127=int memblock_add_node(phys_addr_t base, phys_addr_t size, int nid,\ninclude/linux/memblock.h-128-\t\t      enum memblock_flags flags);\ninclude/linux/memblock.h:129:int memblock_add(phys_addr_t base, phys_addr_t size);\ninclude/linux/memblock.h-130-int memblock_remove(phys_addr_t base, phys_addr_t size);\n--\nkernel/liveupdate/kexec_handover.c=1957=void __init kho_populate(phys_addr_t fdt_phys, u64 fdt_len,\n--\nkernel/liveupdate/kexec_handover.c-2005-\nkernel/liveupdate/kexec_handover.c:2006:\t\tmemblock_add(area-\u003eaddr, size);\nkernel/liveupdate/kexec_handover.c-2007-\t\terr = memblock_mark_kho_noprsrv(area-\u003eaddr, size);\n--\nmm/memblock.c-77- * The early architecture setup should tell memblock what the physical\nmm/memblock.c:78: * memory layout is by using memblock_add() or memblock_add_node()\nmm/memblock.c-79- * functions. The first function does not assign the region to a NUMA\n--\nmm/memblock.c=752=int __init_memblock memblock_add_node(phys_addr_t base, phys_addr_t size,\n--\nmm/memblock.c-773- */\nmm/memblock.c:774:int __init_memblock memblock_add(phys_addr_t base, phys_addr_t size)\nmm/memblock.c-775-{\n--\ntools/testing/memblock/tests/basic_api.c=41=static int memblock_add_simple_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-54-\treset_memblock_regions();\ntools/testing/memblock/tests/basic_api.c:55:\tmemblock_add(r.base, r.size);\ntools/testing/memblock/tests/basic_api.c-56-\n--\ntools/testing/memblock/tests/basic_api.c=117=static int memblock_add_disjoint_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-135-\treset_memblock_regions();\ntools/testing/memblock/tests/basic_api.c:136:\tmemblock_add(r1.base, r1.size);\ntools/testing/memblock/tests/basic_api.c:137:\tmemblock_add(r2.base, r2.size);\ntools/testing/memblock/tests/basic_api.c-138-\n--\ntools/testing/memblock/tests/basic_api.c=170=static int memblock_add_overlap_top_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-190-\treset_memblock_regions();\ntools/testing/memblock/tests/basic_api.c:191:\tmemblock_add(r1.base, r1.size);\ntools/testing/memblock/tests/basic_api.c:192:\tmemblock_add(r2.base, r2.size);\ntools/testing/memblock/tests/basic_api.c-193-\n--\ntools/testing/memblock/tests/basic_api.c=222=static int memblock_add_overlap_bottom_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-242-\treset_memblock_regions();\ntools/testing/memblock/tests/basic_api.c:243:\tmemblock_add(r1.base, r1.size);\ntools/testing/memblock/tests/basic_api.c:244:\tmemblock_add(r2.base, r2.size);\ntools/testing/memblock/tests/basic_api.c-245-\n--\ntools/testing/memblock/tests/basic_api.c=272=static int memblock_add_within_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-289-\treset_memblock_regions();\ntools/testing/memblock/tests/basic_api.c:290:\tmemblock_add(r1.base, r1.size);\ntools/testing/memblock/tests/basic_api.c:291:\tmemblock_add(r2.base, r2.size);\ntools/testing/memblock/tests/basic_api.c-292-\n--\ntools/testing/memblock/tests/basic_api.c=308=static int memblock_add_twice_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-318-\ntools/testing/memblock/tests/basic_api.c:319:\tmemblock_add(r.base, r.size);\ntools/testing/memblock/tests/basic_api.c:320:\tmemblock_add(r.base, r.size);\ntools/testing/memblock/tests/basic_api.c-321-\n--\ntools/testing/memblock/tests/basic_api.c=342=static int memblock_add_between_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-366-\treset_memblock_regions();\ntools/testing/memblock/tests/basic_api.c:367:\tmemblock_add(r1.base, r1.size);\ntools/testing/memblock/tests/basic_api.c:368:\tmemblock_add(r2.base, r2.size);\ntools/testing/memblock/tests/basic_api.c:369:\tmemblock_add(r3.base, r3.size);\ntools/testing/memblock/tests/basic_api.c-370-\n--\ntools/testing/memblock/tests/basic_api.c=396=static int memblock_add_near_max_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-412-\treset_memblock_regions();\ntools/testing/memblock/tests/basic_api.c:413:\tmemblock_add(r.base, r.size);\ntools/testing/memblock/tests/basic_api.c-414-\n--\ntools/testing/memblock/tests/basic_api.c=432=static int memblock_add_many_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-457-\t\t\t\t\t     sizeof(struct memblock_region));\ntools/testing/memblock/tests/basic_api.c:458:\tmemblock_add(base, new_memory_regions_size);\ntools/testing/memblock/tests/basic_api.c-459-\n--\ntools/testing/memblock/tests/basic_api.c-469-\t\t */\ntools/testing/memblock/tests/basic_api.c:470:\t\tmemblock_add(base, size);\ntools/testing/memblock/tests/basic_api.c-471-\t\tbase += size + gap_size;\n--\ntools/testing/memblock/tests/basic_api.c-489-\t * Now memblock_double_array() works fine. Let's check after the\ntools/testing/memblock/tests/basic_api.c:490:\t * double_array(), the memblock_add() still works as normal.\ntools/testing/memblock/tests/basic_api.c-491-\t */\ntools/testing/memblock/tests/basic_api.c:492:\tmemblock_add(r.base, r.size);\ntools/testing/memblock/tests/basic_api.c-493-\tASSERT_EQ(memblock.memory.regions[0].base, r.base);\n--\ntools/testing/memblock/tests/basic_api.c=901=static int memblock_reserve_many_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-918-\tdummy_physical_memory_init();\ntools/testing/memblock/tests/basic_api.c:919:\tmemblock_add(dummy_physical_memory_base(), MEM_SIZE);\ntools/testing/memblock/tests/basic_api.c-920-\n--\ntools/testing/memblock/tests/basic_api.c=1000=static int memblock_reserve_all_locations_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-1018-\t\tdummy_physical_memory_init();\ntools/testing/memblock/tests/basic_api.c:1019:\t\tmemblock_add(dummy_physical_memory_base(), MEM_SIZE);\ntools/testing/memblock/tests/basic_api.c-1020-\n--\ntools/testing/memblock/tests/basic_api.c=1123=static int memblock_reserve_many_may_conflict_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-1154-\t\t/* Add a valid memory region used by double_array(). */\ntools/testing/memblock/tests/basic_api.c:1155:\t\tmemblock_add(MEMORY_BASE_OFFSET(0, offset), MEM_SIZE);\ntools/testing/memblock/tests/basic_api.c-1156-\t\t/*\n--\ntools/testing/memblock/tests/basic_api.c-1159-\t\t */\ntools/testing/memblock/tests/basic_api.c:1160:\t\tmemblock_add(MEMORY_BASE_OFFSET(skip, offset), MEM_SIZE);\ntools/testing/memblock/tests/basic_api.c-1161-\n--\ntools/testing/memblock/tests/basic_api.c=1280=static int memblock_remove_simple_check(void)\n--\ntools/testing/memblock/tests/basic_api.c-1297-\treset_memblock_regions();\ntools/testing/memblock/tests/basic_api.c:1298:\tmemblock_add(r1.base, r1.size);\n\n"
}

gemini-3.8-flash

null

null

							input: 41863
							output: 20
							thoughts: 515
						

**My Analysis of `memblock_add` Usage**

Okay, so I'm thinking about `memblock_add` and how it's typically used. The vast majority of calls to it are from `__init` functions during the boot process. But there's this one exception: `arch/powerpc/platforms/pseries/hotplug-memory.c`. I need to figure out how `pseries_add_mem_node` interfaces with `memblock_add`. Ah, right, memory hotplug! It appears that `mm/memory_hotplug.c` calls `memblock_add_node`, which makes sense. I see it right there in the code: `__add_memory_resource` calls `memblock_add_node`.

But wait, look at this `IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)` check. This could be important. Is `CONFIG_ARCH_KEEP_MEMBLOCK` enabled on x86_64, which is what I'm mostly concerned with? Let me check how it's defined and selected in `arch/x86/Kconfig`. Okay, it looks like `INTEL_TDX_HOST` selects `ARCH_KEEP_MEMBLOCK`. So, could `INTEL_TDX_HOST` be enabled in a standard x86_64 configuration? It's definitely something to consider.

Now, a critical point – how does this relate to fuzzing? Does memory hotplug even happen during fuzzing with tools like syzkaller? Can syzkaller trigger memory hotplug operations, like writing to `/sys/devices/system/memory/probe`? Actually, I need to check if `CONFIG_ARCH_MEMORY_PROBE` exists on x86. Let's look that up.

{
  "Expression": "ARCH_MEMORY_PROBE"
}

{
  "Output": "Documentation/admin-guide/mm/memory-hotplug.rst=276=The following files are currently defined:\n--\nDocumentation/admin-guide/mm/memory-hotplug.rst-290-\nDocumentation/admin-guide/mm/memory-hotplug.rst:291:\t\t       Availability depends on the CONFIG_ARCH_MEMORY_PROBE\nDocumentation/admin-guide/mm/memory-hotplug.rst-292-\t\t       kernel configuration option.\n--\narch/loongarch/Kconfig=776=config ARCH_SPARSEMEM_ENABLE\n--\narch/loongarch/Kconfig-784-\narch/loongarch/Kconfig:785:config ARCH_MEMORY_PROBE\narch/loongarch/Kconfig-786-\tdef_bool y\n--\narch/powerpc/Kconfig=806=config ILLEGAL_POINTER_VALUE\n--\narch/powerpc/Kconfig-812-\narch/powerpc/Kconfig:813:config ARCH_MEMORY_PROBE\narch/powerpc/Kconfig-814-\tdef_bool y\n--\narch/x86/Kconfig=1569=config ARCH_SELECT_MEMORY_MODEL\n--\narch/x86/Kconfig-1572-\narch/x86/Kconfig:1573:config ARCH_MEMORY_PROBE\narch/x86/Kconfig-1574-\tbool \"Enable sysfs memory/probe interface\"\n--\ndrivers/base/memory.c=562=static DEVICE_ATTR_RO(crash_hotplug);\n--\ndrivers/base/memory.c-570- */\ndrivers/base/memory.c:571:#ifdef CONFIG_ARCH_MEMORY_PROBE\ndrivers/base/memory.c-572-static ssize_t probe_store(struct device *dev, struct device_attribute *attr,\n--\ndrivers/base/memory.c=920=static struct attribute *memory_root_attrs[] = {\ndrivers/base/memory.c:921:#ifdef CONFIG_ARCH_MEMORY_PROBE\ndrivers/base/memory.c-922-\t\u0026dev_attr_probe.attr,\n"
}

gemini-3.8-flash

null

null

							input: 43323
							output: 30
							thoughts: 138
						

**My Immediate Concerns Regarding Memory Management**

Okay, hold on a minute. I need to backtrack and really consider the implications here. My first thought is, did I neglect `drivers/dax/kmem.c` in my analysis? It's crucial to understand the interactions with DAX kmem. Specifically, I'm now wondering, and this is a significant point, can a DAX device actually be hotplugged and presented as system RAM via `dax_kmem`? That possibility changes everything.

And what about `virtio-mem`? Its capabilities could fundamentally alter how memory is managed in virtualized environments. I can't overlook its potential role here.

Then, I'm reminded of `drivers/hv/hv_balloon.c`. Hyper-V ballooning might present a specific set of memory management challenges or behaviors I haven't fully accounted for. I need to factor that in.

Wait, the potential interplay with `memblock_remove` is also concerning me. What are the knock-on effects here? How does its presence shape these interactions?

And then, I have to zoom out and think about the overall sysfs interaction... When memory is offlined and removed via sysfs, there must be a specific process. Wait! I can remove memory via sysfs and specifically `/sys/devices/system/memory/memoryX/state`? If this is accurate, I definitely need to understand this better. To get to the bottom of this, let's consult `drivers/base/memory.c` and specifically investigate the `state_store` function. That seems like the right place to begin.

{
  "Expression": "state_store",
  "PathPrefix": "drivers/base/memory.c"
}

{
  "Output": "drivers/base/memory.c=394=static int memory_subsys_offline(struct device *dev)\n--\ndrivers/base/memory.c-403-\ndrivers/base/memory.c:404:static ssize_t state_store(struct device *dev, struct device_attribute *attr,\ndrivers/base/memory.c-405-\t\t\t   const char *buf, size_t count)\n"
}

gemini-3.8-flash

null

null

							input: 43948
							output: 35
							thoughts: 19
						

Okay, let's dive into this. Here's my take on what's going on:

**Analyzing the `state_store` Function in `drivers/base/memory.c`**

Alright, time to crack open `drivers/base/memory.c` and specifically, let's zero in on the `state_store` function. Knowing the context of device drivers and memory management, I'm already anticipating some low-level interactions. I expect this function deals with persisting or retrieving some kind of state related to memory within the system. "State" could refer to anything from power-saving configuration to persistent memory ranges, or even more mundane things. My gut tells me this is probably involved with managing a device's view of memory, perhaps in a way that’s resistant to rebooting the system.

I'm instantly thinking about potential areas of concern: concurrent access, atomicity, and error handling. Given its place in the base memory drivers, the function's interface likely deals with things that may be widely accessed across the system, so proper synchronization is going to be crucial. I'm going to be looking for mutexes, spinlocks, or other synchronization primitives. I'll also be scrutinizing how the function handles errors. A simple return code might not suffice if we're dealing with potentially critical system state. Maybe there's logging involved, or possibly even more complex error recovery mechanisms. Let's see how they deal with this.

{
  "File": "drivers/base/memory.c",
  "FirstLine": 404,
  "LineCount": 50
}

{
  "Contents": " 404:\tstatic ssize_t state_store(struct device *dev, struct device_attribute *attr,\n 405:\t\t\t\t   const char *buf, size_t count)\n 406:\t{\n 407:\t\tconst int online_type = mhp_online_type_from_str(buf);\n 408:\t\tstruct memory_block *mem = to_memory_block(dev);\n 409:\t\tint ret;\n 410:\t\n 411:\t\tif (online_type \u003c 0)\n 412:\t\t\treturn -EINVAL;\n 413:\t\n 414:\t\tret = lock_device_hotplug_sysfs();\n 415:\t\tif (ret)\n 416:\t\t\treturn ret;\n 417:\t\n 418:\t\tswitch (online_type) {\n 419:\t\tcase MMOP_ONLINE_KERNEL:\n 420:\t\tcase MMOP_ONLINE_MOVABLE:\n 421:\t\tcase MMOP_ONLINE:\n 422:\t\t\t/* mem-\u003eonline_type is protected by device_hotplug_lock */\n 423:\t\t\tmem-\u003eonline_type = online_type;\n 424:\t\t\tret = device_online(\u0026mem-\u003edev);\n 425:\t\t\tbreak;\n 426:\t\tcase MMOP_OFFLINE:\n 427:\t\t\tret = device_offline(\u0026mem-\u003edev);\n 428:\t\t\tbreak;\n 429:\t\tdefault:\n 430:\t\t\tret = -EINVAL; /* should never happen */\n 431:\t\t}\n 432:\t\n 433:\t\tunlock_device_hotplug();\n 434:\t\n 435:\t\tif (ret \u003c 0)\n 436:\t\t\treturn ret;\n 437:\t\tif (ret)\n 438:\t\t\treturn -EINVAL;\n 439:\t\n 440:\t\treturn count;\n 441:\t}\n 442:\t\n 443:\t/*\n 444:\t * Legacy interface that we cannot remove: s390x exposes the storage increment\n 445:\t * covered by a memory block, allowing for identifying which memory blocks\n 446:\t * comprise a storage increment. Since a memory block spans complete\n 447:\t * storage increments nowadays, this interface is basically unused. Other\n 448:\t * archs never exposed != 0.\n 449:\t */\n 450:\tstatic ssize_t phys_device_show(struct device *dev,\n 451:\t\t\t\t\tstruct device_attribute *attr, char *buf)\n 452:\t{\n 453:\t\tstruct memory_block *mem = to_memory_block(dev);\n"
}

gemini-3.8-flash

null

null

							input: 45011
							output: 25
							thoughts: 71
						

Okay, let's see. My mind is racing a bit here.

**Navigating Memory Offlining and Removal**

Right, so, I'm thinking about this `device_offline` process and how it relates to memory. The initial thought was, "Does offlining a device *remove* its memory?" Seems like a reasonable question to start with. Then I realized, wait, `device_offline` *actually* calls `offline_pages`. That's not the same as `remove_memory`. Interesting distinction. So, when *is* the `remove_memory` function actually invoked? That's the key now. I need to understand the control flow. The next logical step is to track down all calls to `remove_memory`, or anything like it, such as `try_remove_memory` or, even better, any internal or private versions, like `__remove_memory`. That should give me the answer I need. I need to trace this down and get the precise flow of how the memory is handled in this scenario.

{
  "Expression": "(remove_memory|try_remove_memory)"
}

{
  "Output": "\nFull output is too long, showing 500 out of 548 lines.\nUse more precise expression if possible.\n\narch/arm64/mm/mmu.c=2007=int arch_add_memory(int nid, u64 start, u64 size,\n--\narch/arm64/mm/mmu.c-2041-\narch/arm64/mm/mmu.c:2042:void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,\narch/arm64/mm/mmu.c-2043-\t\t\tstruct dev_pagemap *pgmap)\n--\narch/loongarch/mm/init.c=107=int arch_add_memory(int nid, u64 start, u64 size, struct mhp_params *params)\n--\narch/loongarch/mm/init.c-121-\narch/loongarch/mm/init.c:122:void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,\narch/loongarch/mm/init.c-123-\t\t\tstruct dev_pagemap *pgmap)\n--\narch/powerpc/mm/mem.c=145=int __ref arch_add_memory(int nid, u64 start, u64 size,\n--\narch/powerpc/mm/mem.c-160-\narch/powerpc/mm/mem.c:161:void __ref arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,\narch/powerpc/mm/mem.c-162-\t\t\t      struct dev_pagemap *pgmap)\n--\narch/powerpc/platforms/pseries/hotplug-memory.c=233=static int pseries_remove_memblock(unsigned long base, unsigned long memblock_size)\n--\narch/powerpc/platforms/pseries/hotplug-memory.c-248-\tfor (i = 0; i \u003c sections_per_block; i++) {\narch/powerpc/platforms/pseries/hotplug-memory.c:249:\t\t__remove_memory(base, MIN_MEMORY_BLOCK_SIZE);\narch/powerpc/platforms/pseries/hotplug-memory.c-250-\t\tbase += MIN_MEMORY_BLOCK_SIZE;\n--\narch/powerpc/platforms/pseries/hotplug-memory.c=302=static int dlpar_remove_lmb(struct drmem_lmb *lmb)\n--\narch/powerpc/platforms/pseries/hotplug-memory.c-319-\narch/powerpc/platforms/pseries/hotplug-memory.c:320:\t__remove_memory(lmb-\u003ebase_addr, memory_block_size);\narch/powerpc/platforms/pseries/hotplug-memory.c-321-\tmemory_block_put(mem_block);\n--\narch/powerpc/platforms/pseries/hotplug-memory.c=564=static int dlpar_add_lmb(struct drmem_lmb *lmb)\n--\narch/powerpc/platforms/pseries/hotplug-memory.c-596-\t\tpr_err(\"Failed to online LMB 0x%x on node %u\\n\", lmb-\u003edrc_index, nid);\narch/powerpc/platforms/pseries/hotplug-memory.c:597:\t\t__remove_memory(lmb-\u003ebase_addr, block_sz);\narch/powerpc/platforms/pseries/hotplug-memory.c-598-\t\tinvalidate_lmb_associativity_index(lmb);\n--\narch/riscv/mm/init.c=1721=int __ref arch_add_memory(int nid, u64 start, u64 size, struct mhp_params *params)\n--\narch/riscv/mm/init.c-1739-\narch/riscv/mm/init.c:1740:void __ref arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,\narch/riscv/mm/init.c-1741-\t\t\t      struct dev_pagemap *pgmap)\n--\narch/s390/mm/init.c=275=int arch_add_memory(int nid, u64 start, u64 size,\n--\narch/s390/mm/init.c-295-\narch/s390/mm/init.c:296:void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,\narch/s390/mm/init.c-297-\t\t\tstruct dev_pagemap *pgmap)\n--\narch/x86/mm/init_64.c=1267=kernel_physical_mapping_remove(unsigned long start, unsigned long end)\n--\narch/x86/mm/init_64.c-1274-\narch/x86/mm/init_64.c:1275:void __ref arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,\narch/x86/mm/init_64.c-1276-\t\t\t      struct dev_pagemap *pgmap)\n--\ndrivers/acpi/acpi_memhotplug.c=168=static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)\n--\ndrivers/acpi/acpi_memhotplug.c-252-\ndrivers/acpi/acpi_memhotplug.c:253:static void acpi_memory_remove_memory(struct acpi_memory_device *mem_device)\ndrivers/acpi/acpi_memhotplug.c-254-{\n--\ndrivers/acpi/acpi_memhotplug.c-261-\t\tacpi_unbind_memory_blocks(info);\ndrivers/acpi/acpi_memhotplug.c:262:\t\t__remove_memory(info-\u003estart_addr, info-\u003elength);\ndrivers/acpi/acpi_memhotplug.c-263-\t\tlist_del(\u0026info-\u003elist);\n--\ndrivers/acpi/acpi_memhotplug.c=325=static void acpi_memory_device_remove(struct acpi_device *device)\n--\ndrivers/acpi/acpi_memhotplug.c-332-\tmem_device = acpi_driver_data(device);\ndrivers/acpi/acpi_memhotplug.c:333:\tacpi_memory_remove_memory(mem_device);\ndrivers/acpi/acpi_memhotplug.c-334-\tacpi_memory_device_free(mem_device);\n--\ndrivers/base/memory.c=790=static int add_memory_block(unsigned long block_id, int nid, unsigned long state,\n--\ndrivers/base/memory.c-835-\ndrivers/base/memory.c:836:static void remove_memory_block(struct memory_block *memory)\ndrivers/base/memory.c-837-{\n--\ndrivers/base/memory.c=860=int create_memory_block_devices(unsigned long start, unsigned long size,\n--\ndrivers/base/memory.c-885-\t\t\t\tcontinue;\ndrivers/base/memory.c:886:\t\t\tremove_memory_block(mem);\ndrivers/base/memory.c-887-\t\t}\n--\ndrivers/base/memory.c-898- */\ndrivers/base/memory.c:899:void remove_memory_block_devices(unsigned long start, unsigned long size)\ndrivers/base/memory.c-900-{\n--\ndrivers/base/memory.c-915-\t\tunregister_memory_block_under_nodes(mem);\ndrivers/base/memory.c:916:\t\tremove_memory_block(mem);\ndrivers/base/memory.c-917-\t}\n--\ndrivers/char/agp/agp.h=97=struct agp_bridge_driver {\n--\ndrivers/char/agp/agp.h-114-\tint (*insert_memory)(struct agp_memory *, off_t, int);\ndrivers/char/agp/agp.h:115:\tint (*remove_memory)(struct agp_memory *, off_t, int);\ndrivers/char/agp/agp.h-116-\tstruct agp_memory *(*alloc_by_type) (size_t, int);\n--\ndrivers/char/agp/agp.h=192=int agp_generic_insert_memory(struct agp_memory *mem, off_t pg_start, int type);\ndrivers/char/agp/agp.h:193:int agp_generic_remove_memory(struct agp_memory *mem, off_t pg_start, int type);\ndrivers/char/agp/agp.h-194-struct agp_memory *agp_generic_alloc_by_type(size_t page_count, int type);\n--\ndrivers/char/agp/ali-agp.c=202=static const struct agp_bridge_driver ali_generic_bridge = {\n--\ndrivers/char/agp/ali-agp.c-218-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/ali-agp.c:219:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/ali-agp.c-220-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/ali-agp.c=227=static const struct agp_bridge_driver ali_m1541_bridge = {\n--\ndrivers/char/agp/ali-agp.c-242-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/ali-agp.c:243:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/ali-agp.c-244-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/alpha-agp.c=84=static int alpha_core_agp_insert_memory(struct agp_memory *mem, off_t pg_start,\n--\ndrivers/char/agp/alpha-agp.c-105-\ndrivers/char/agp/alpha-agp.c:106:static int alpha_core_agp_remove_memory(struct agp_memory *mem, off_t pg_start,\ndrivers/char/agp/alpha-agp.c-107-\t\t\t\t\tint type)\n--\ndrivers/char/agp/alpha-agp.c=122=struct agp_bridge_driver alpha_core_agp_driver = {\n--\ndrivers/char/agp/alpha-agp.c-139-\t.insert_memory\t\t= alpha_core_agp_insert_memory,\ndrivers/char/agp/alpha-agp.c:140:\t.remove_memory\t\t= alpha_core_agp_remove_memory,\ndrivers/char/agp/alpha-agp.c-141-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/amd-k7-agp.c=284=static int amd_insert_memory(struct agp_memory *mem, off_t pg_start, int type)\n--\ndrivers/char/agp/amd-k7-agp.c-325-\ndrivers/char/agp/amd-k7-agp.c:326:static int amd_remove_memory(struct agp_memory *mem, off_t pg_start, int type)\ndrivers/char/agp/amd-k7-agp.c-327-{\n--\ndrivers/char/agp/amd-k7-agp.c=363=static const struct agp_bridge_driver amd_irongate_driver = {\n--\ndrivers/char/agp/amd-k7-agp.c-379-\t.insert_memory\t\t= amd_insert_memory,\ndrivers/char/agp/amd-k7-agp.c:380:\t.remove_memory\t\t= amd_remove_memory,\ndrivers/char/agp/amd-k7-agp.c-381-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/amd64-agp.c=216=static const struct agp_bridge_driver amd_8151_driver = {\n--\ndrivers/char/agp/amd64-agp.c-232-\t.insert_memory\t\t= amd64_insert_memory,\ndrivers/char/agp/amd64-agp.c:233:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/amd64-agp.c-234-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/ati-agp.c=258=static int ati_insert_memory(struct agp_memory * mem,\n--\ndrivers/char/agp/ati-agp.c-305-\ndrivers/char/agp/ati-agp.c:306:static int ati_remove_memory(struct agp_memory * mem, off_t pg_start,\ndrivers/char/agp/ati-agp.c-307-\t\t\t     int type)\n--\ndrivers/char/agp/ati-agp.c=411=static const struct agp_bridge_driver ati_generic_bridge = {\n--\ndrivers/char/agp/ati-agp.c-427-\t.insert_memory\t\t= ati_insert_memory,\ndrivers/char/agp/ati-agp.c:428:\t.remove_memory\t\t= ati_remove_memory,\ndrivers/char/agp/ati-agp.c-429-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/efficeon-agp.c=237=static int efficeon_insert_memory(struct agp_memory * mem, off_t pg_start, int type)\n--\ndrivers/char/agp/efficeon-agp.c-285-\ndrivers/char/agp/efficeon-agp.c:286:static int efficeon_remove_memory(struct agp_memory * mem, off_t pg_start, int type)\ndrivers/char/agp/efficeon-agp.c-287-{\n--\ndrivers/char/agp/efficeon-agp.c-289-\ndrivers/char/agp/efficeon-agp.c:290:\tprintk(KERN_DEBUG PFX \"efficeon_remove_memory(%lx, %d)\\n\", pg_start, count);\ndrivers/char/agp/efficeon-agp.c-291-\n--\ndrivers/char/agp/efficeon-agp.c=313=static const struct agp_bridge_driver efficeon_driver = {\n--\ndrivers/char/agp/efficeon-agp.c-330-\t.insert_memory\t\t= efficeon_insert_memory,\ndrivers/char/agp/efficeon-agp.c:331:\t.remove_memory\t\t= efficeon_remove_memory,\ndrivers/char/agp/efficeon-agp.c-332-\t.cant_use_aperture\t= false,\t// true might be faster?\n--\ndrivers/char/agp/generic.c=448=int agp_unbind_memory(struct agp_memory *curr)\n--\ndrivers/char/agp/generic.c-459-\ndrivers/char/agp/generic.c:460:\tret_val = curr-\u003ebridge-\u003edriver-\u003eremove_memory(curr, curr-\u003epg_start, curr-\u003etype);\ndrivers/char/agp/generic.c-461-\n--\ndrivers/char/agp/generic.c=1104=EXPORT_SYMBOL(agp_generic_insert_memory);\n--\ndrivers/char/agp/generic.c-1106-\ndrivers/char/agp/generic.c:1107:int agp_generic_remove_memory(struct agp_memory *mem, off_t pg_start, int type)\ndrivers/char/agp/generic.c-1108-{\n--\ndrivers/char/agp/generic.c-1142-}\ndrivers/char/agp/generic.c:1143:EXPORT_SYMBOL(agp_generic_remove_memory);\ndrivers/char/agp/generic.c-1144-\n--\ndrivers/char/agp/intel-agp.c=450=static const struct agp_bridge_driver intel_generic_driver = {\n--\ndrivers/char/agp/intel-agp.c-466-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/intel-agp.c:467:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/intel-agp.c-468-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/intel-agp.c=477=static const struct agp_bridge_driver intel_815_driver = {\n--\ndrivers/char/agp/intel-agp.c-493-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/intel-agp.c:494:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/intel-agp.c-495-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/intel-agp.c=504=static const struct agp_bridge_driver intel_820_driver = {\n--\ndrivers/char/agp/intel-agp.c-520-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/intel-agp.c:521:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/intel-agp.c-522-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/intel-agp.c=531=static const struct agp_bridge_driver intel_830mp_driver = {\n--\ndrivers/char/agp/intel-agp.c-547-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/intel-agp.c:548:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/intel-agp.c-549-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/intel-agp.c=558=static const struct agp_bridge_driver intel_840_driver = {\n--\ndrivers/char/agp/intel-agp.c-574-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/intel-agp.c:575:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/intel-agp.c-576-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/intel-agp.c=585=static const struct agp_bridge_driver intel_845_driver = {\n--\ndrivers/char/agp/intel-agp.c-601-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/intel-agp.c:602:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/intel-agp.c-603-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/intel-agp.c=612=static const struct agp_bridge_driver intel_850_driver = {\n--\ndrivers/char/agp/intel-agp.c-628-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/intel-agp.c:629:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/intel-agp.c-630-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/intel-agp.c=639=static const struct agp_bridge_driver intel_860_driver = {\n--\ndrivers/char/agp/intel-agp.c-655-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/intel-agp.c:656:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/intel-agp.c-657-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/intel-agp.c=666=static const struct agp_bridge_driver intel_7505_driver = {\n--\ndrivers/char/agp/intel-agp.c-682-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/intel-agp.c:683:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/intel-agp.c-684-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/intel-gtt.c=1206=static const struct agp_bridge_driver intel_fake_agp_driver = {\n--\ndrivers/char/agp/intel-gtt.c-1218-\t.insert_memory\t\t= intel_fake_agp_insert_entries,\ndrivers/char/agp/intel-gtt.c:1219:\t.remove_memory\t\t= intel_fake_agp_remove_entries,\ndrivers/char/agp/intel-gtt.c-1220-\t.alloc_by_type\t\t= intel_fake_agp_alloc_by_type,\n--\ndrivers/char/agp/nvidia-agp.c=202=static int nvidia_insert_memory(struct agp_memory *mem, off_t pg_start, int type)\n--\ndrivers/char/agp/nvidia-agp.c-240-\ndrivers/char/agp/nvidia-agp.c:241:static int nvidia_remove_memory(struct agp_memory *mem, off_t pg_start, int type)\ndrivers/char/agp/nvidia-agp.c-242-{\n--\ndrivers/char/agp/nvidia-agp.c=311=static const struct agp_bridge_driver nvidia_driver = {\n--\ndrivers/char/agp/nvidia-agp.c-327-\t.insert_memory\t\t= nvidia_insert_memory,\ndrivers/char/agp/nvidia-agp.c:328:\t.remove_memory\t\t= nvidia_remove_memory,\ndrivers/char/agp/nvidia-agp.c-329-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/parisc-agp.c=173=static int\ndrivers/char/agp/parisc-agp.c:174:parisc_agp_remove_memory(struct agp_memory *mem, off_t pg_start, int type)\ndrivers/char/agp/parisc-agp.c-175-{\n--\ndrivers/char/agp/parisc-agp.c=227=static const struct agp_bridge_driver parisc_agp_driver = {\n--\ndrivers/char/agp/parisc-agp.c-239-\t.insert_memory\t\t= parisc_agp_insert_memory,\ndrivers/char/agp/parisc-agp.c:240:\t.remove_memory\t\t= parisc_agp_remove_memory,\ndrivers/char/agp/parisc-agp.c-241-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/sis-agp.c=122=static struct agp_bridge_driver sis_driver = {\n--\ndrivers/char/agp/sis-agp.c-138-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/sis-agp.c:139:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/sis-agp.c-140-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/sworks-agp.c=316=static int serverworks_insert_memory(struct agp_memory *mem,\n--\ndrivers/char/agp/sworks-agp.c-356-\ndrivers/char/agp/sworks-agp.c:357:static int serverworks_remove_memory(struct agp_memory *mem, off_t pg_start,\ndrivers/char/agp/sworks-agp.c-358-\t\t\t     int type)\n--\ndrivers/char/agp/sworks-agp.c=419=static const struct agp_bridge_driver sworks_driver = {\n--\ndrivers/char/agp/sworks-agp.c-434-\t.insert_memory\t\t= serverworks_insert_memory,\ndrivers/char/agp/sworks-agp.c:435:\t.remove_memory\t\t= serverworks_remove_memory,\ndrivers/char/agp/sworks-agp.c-436-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/uninorth-agp.c=150=static int uninorth_insert_memory(struct agp_memory *mem, off_t pg_start, int type)\n--\ndrivers/char/agp/uninorth-agp.c-199-\ndrivers/char/agp/uninorth-agp.c:200:static int uninorth_remove_memory(struct agp_memory *mem, off_t pg_start, int type)\ndrivers/char/agp/uninorth-agp.c-201-{\n--\ndrivers/char/agp/uninorth-agp.c=509=const struct agp_bridge_driver uninorth_agp_driver = {\n--\ndrivers/char/agp/uninorth-agp.c-524-\t.insert_memory\t\t= uninorth_insert_memory,\ndrivers/char/agp/uninorth-agp.c:525:\t.remove_memory\t\t= uninorth_remove_memory,\ndrivers/char/agp/uninorth-agp.c-526-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/uninorth-agp.c=537=const struct agp_bridge_driver u3_agp_driver = {\n--\ndrivers/char/agp/uninorth-agp.c-552-\t.insert_memory\t\t= uninorth_insert_memory,\ndrivers/char/agp/uninorth-agp.c:553:\t.remove_memory\t\t= uninorth_remove_memory,\ndrivers/char/agp/uninorth-agp.c-554-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/via-agp.c=170=static const struct agp_bridge_driver via_agp3_driver = {\n--\ndrivers/char/agp/via-agp.c-186-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/via-agp.c:187:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/via-agp.c-188-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/char/agp/via-agp.c=197=static const struct agp_bridge_driver via_driver = {\n--\ndrivers/char/agp/via-agp.c-213-\t.insert_memory\t\t= agp_generic_insert_memory,\ndrivers/char/agp/via-agp.c:214:\t.remove_memory\t\t= agp_generic_remove_memory,\ndrivers/char/agp/via-agp.c-215-\t.alloc_by_type\t\t= agp_generic_alloc_by_type,\n--\ndrivers/dax/kmem.c=220=static int dax_kmem_do_hotremove(struct dev_dax *dev_dax,\n--\ndrivers/dax/kmem.c-247-\ndrivers/dax/kmem.c:248:\trc = offline_and_remove_memory_ranges(ranges, nr_ranges);\ndrivers/dax/kmem.c-249-\tkfree(ranges);\n--\ndrivers/dax/kmem.c=383=static int dev_dax_kmem_probe(struct dev_dax *dev_dax)\n--\ndrivers/dax/kmem.c-482-/*\ndrivers/dax/kmem.c:483: * Remove the device's added ranges with remove_memory().\ndrivers/dax/kmem.c-484- * Unlike the sysfs unplug path it never offlines and fails if the blocks are\n--\ndrivers/dax/kmem.c=489=static int dax_kmem_remove_ranges(struct dev_dax *dev_dax,\n--\ndrivers/dax/kmem.c-499-\t\t\tcontinue;\ndrivers/dax/kmem.c:500:\t\tif (remove_memory(range.start, range_len(\u0026range))) {\ndrivers/dax/kmem.c-501-\t\t\tdev_warn(dev, \"mapping%d: %#llx-%#llx stuck online until reboot\\n\",\n--\ndrivers/dax/kmem.c=513=static void dev_dax_kmem_remove(struct dev_dax *dev_dax)\n--\ndrivers/dax/kmem.c-520-\t * Remove every range that is still added.  dax_kmem_remove_ranges()\ndrivers/dax/kmem.c:521:\t * uses remove_memory(), which never offlines: an online block fails\ndrivers/dax/kmem.c-522-\t * with -EBUSY rather than deadlocking an uninterruptible unbind.\n--\ndrivers/dax/kmem.c-525-\t * blocks were toggled via memoryX/state. Do not trust it here and\ndrivers/dax/kmem.c:526:\t * attempt simply remove_memory() - which reports the true state of\ndrivers/dax/kmem.c-527-\t * each range anyway. Anything left online is leaked until reboot.\n--\ndrivers/firmware/efi/libstub/efistub.h=405=union efi_dxe_services_table {\n--\ndrivers/firmware/efi/libstub/efistub.h-410-\t\tvoid *free_memory_space;\ndrivers/firmware/efi/libstub/efistub.h:411:\t\tvoid *remove_memory_space;\ndrivers/firmware/efi/libstub/efistub.h-412-\t\tefi_status_t (__efiapi *get_memory_space_descriptor)(efi_physical_addr_t,\n--\ndrivers/firmware/efi/libstub/efistub.h-433-\t\tu32 free_memory_space;\ndrivers/firmware/efi/libstub/efistub.h:434:\t\tu32 remove_memory_space;\ndrivers/firmware/efi/libstub/efistub.h-435-\t\tu32 get_memory_space_descriptor;\n--\ndrivers/s390/char/sclp_mem.c=189=static ssize_t sclp_config_mem_store(struct kobject *kobj, struct kobj_attribute *attr,\n--\ndrivers/s390/char/sclp_mem.c-247-\t\tsclp_mem_change_state(addr, block_size, 0);\ndrivers/s390/char/sclp_mem.c:248:\t\t__remove_memory(addr, block_size);\ndrivers/s390/char/sclp_mem.c-249-#ifdef CONFIG_KASAN\n--\ndrivers/virtio/virtio_mem.c=683=static int virtio_mem_bbm_add_bb(struct virtio_mem *vm, unsigned long bb_id)\n--\ndrivers/virtio/virtio_mem.c-699- */\ndrivers/virtio/virtio_mem.c:700:static int virtio_mem_remove_memory(struct virtio_mem *vm, uint64_t addr,\ndrivers/virtio/virtio_mem.c-701-\t\t\t\t    uint64_t size)\n--\ndrivers/virtio/virtio_mem.c-706-\t\taddr + size - 1);\ndrivers/virtio/virtio_mem.c:707:\trc = remove_memory(addr, size);\ndrivers/virtio/virtio_mem.c-708-\tif (!rc) {\n--\ndrivers/virtio/virtio_mem.c-721-/*\ndrivers/virtio/virtio_mem.c:722: * See virtio_mem_remove_memory(): Try removing a single Linux memory block.\ndrivers/virtio/virtio_mem.c-723- */\ndrivers/virtio/virtio_mem.c=724=static int virtio_mem_sbm_remove_mb(struct virtio_mem *vm, unsigned long mb_id)\n--\ndrivers/virtio/virtio_mem.c-728-\ndrivers/virtio/virtio_mem.c:729:\treturn virtio_mem_remove_memory(vm, addr, size);\ndrivers/virtio/virtio_mem.c-730-}\n--\ndrivers/virtio/virtio_mem.c-739- */\ndrivers/virtio/virtio_mem.c:740:static int virtio_mem_offline_and_remove_memory(struct virtio_mem *vm,\ndrivers/virtio/virtio_mem.c-741-\t\t\t\t\t\tuint64_t addr,\n--\ndrivers/virtio/virtio_mem.c-749-\ndrivers/virtio/virtio_mem.c:750:\trc = offline_and_remove_memory(addr, size);\ndrivers/virtio/virtio_mem.c-751-\tif (!rc) {\n--\ndrivers/virtio/virtio_mem.c-769-/*\ndrivers/virtio/virtio_mem.c:770: * See virtio_mem_offline_and_remove_memory(): Try offlining and removing\ndrivers/virtio/virtio_mem.c-771- * a single Linux memory block.\n--\ndrivers/virtio/virtio_mem.c=773=static int virtio_mem_sbm_offline_and_remove_mb(struct virtio_mem *vm,\n--\ndrivers/virtio/virtio_mem.c-778-\ndrivers/virtio/virtio_mem.c:779:\treturn virtio_mem_offline_and_remove_memory(vm, addr, size);\ndrivers/virtio/virtio_mem.c-780-}\n--\ndrivers/virtio/virtio_mem.c=788=static int virtio_mem_sbm_try_remove_unplugged_mb(struct virtio_mem *vm,\n--\ndrivers/virtio/virtio_mem.c-799-\ndrivers/virtio/virtio_mem.c:800:\t/* offline_and_remove_memory() works for online and offline memory. */\ndrivers/virtio/virtio_mem.c-801-\tmutex_unlock(\u0026vm-\u003ehotplug_mutex);\n--\ndrivers/virtio/virtio_mem.c-810-/*\ndrivers/virtio/virtio_mem.c:811: * See virtio_mem_offline_and_remove_memory(): Try to offline and remove a\ndrivers/virtio/virtio_mem.c-812- * all Linux memory blocks covered by the big block.\n--\ndrivers/virtio/virtio_mem.c=814=static int virtio_mem_bbm_offline_and_remove_bb(struct virtio_mem *vm,\n--\ndrivers/virtio/virtio_mem.c-819-\ndrivers/virtio/virtio_mem.c:820:\treturn virtio_mem_offline_and_remove_memory(vm, addr, size);\ndrivers/virtio/virtio_mem.c-821-}\n--\ninclude/linux/memory.h=182=int create_memory_block_devices(unsigned long start, unsigned long size,\n--\ninclude/linux/memory.h-184-\t\t\t\tstruct memory_group *group);\ninclude/linux/memory.h:185:void remove_memory_block_devices(unsigned long start, unsigned long size);\ninclude/linux/memory.h-186-extern void memory_dev_init(void);\n--\ninclude/linux/memory_hotplug.h=134=static inline bool movable_node_is_enabled(void)\n--\ninclude/linux/memory_hotplug.h-138-\ninclude/linux/memory_hotplug.h:139:extern void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,\ninclude/linux/memory_hotplug.h-140-\t\t\t       struct dev_pagemap *pgmap);\n--\ninclude/linux/memory_hotplug.h=266=extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages,\ninclude/linux/memory_hotplug.h-267-\t\t\t struct zone *zone, struct memory_group *group);\ninclude/linux/memory_hotplug.h:268:extern int remove_memory(u64 start, u64 size);\ninclude/linux/memory_hotplug.h:269:extern void __remove_memory(u64 start, u64 size);\ninclude/linux/memory_hotplug.h:270:extern int offline_and_remove_memory(u64 start, u64 size);\ninclude/linux/memory_hotplug.h:271:int offline_and_remove_memory_ranges(const struct range *ranges,\ninclude/linux/memory_hotplug.h-272-\t\tunsigned int nr_ranges);\n--\ninclude/linux/memory_hotplug.h=277=static inline int offline_pages(unsigned long start_pfn, unsigned long nr_pages,\n--\ninclude/linux/memory_hotplug.h-282-\ninclude/linux/memory_hotplug.h:283:static inline int remove_memory(u64 start, u64 size)\ninclude/linux/memory_hotplug.h-284-{\n--\ninclude/linux/memory_hotplug.h-287-\ninclude/linux/memory_hotplug.h:288:static inline void __remove_memory(u64 start, u64 size) {}\ninclude/linux/memory_hotplug.h-289-\ninclude/linux/memory_hotplug.h:290:static inline int offline_and_remove_memory_ranges(const struct range *ranges,\ninclude/linux/memory_hotplug.h-291-\t\tunsigned int nr_ranges)\n--\nmm/memory_hotplug.c=1412=static void altmap_free(struct vmem_altmap *altmap)\n--\nmm/memory_hotplug.c-1417-\nmm/memory_hotplug.c:1418:static void remove_memory_blocks_and_altmaps(u64 start, u64 size)\nmm/memory_hotplug.c-1419-{\n--\nmm/memory_hotplug.c-1439-\nmm/memory_hotplug.c:1440:\t\tremove_memory_block_devices(cur_start, memblock_size);\nmm/memory_hotplug.c:1441:\t\tarch_remove_memory(cur_start, memblock_size, altmap, NULL);\nmm/memory_hotplug.c-1442-\t\taltmap_free(altmap);\n--\nmm/memory_hotplug.c=1446=static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group,\n--\nmm/memory_hotplug.c-1480-\t\tif (ret) {\nmm/memory_hotplug.c:1481:\t\t\tarch_remove_memory(cur_start, memblock_size, params.altmap, NULL);\nmm/memory_hotplug.c-1482-\t\t\taltmap_free(params.altmap);\n--\nmm/memory_hotplug.c-1489-\tif (ret \u0026\u0026 cur_start != start)\nmm/memory_hotplug.c:1490:\t\tremove_memory_blocks_and_altmaps(start, cur_start - start);\nmm/memory_hotplug.c-1491-\treturn ret;\n--\nmm/memory_hotplug.c=1500=static int __add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags,\n--\nmm/memory_hotplug.c-1567-\t\tif (ret) {\nmm/memory_hotplug.c:1568:\t\t\tarch_remove_memory(start, size, params.altmap, NULL);\nmm/memory_hotplug.c-1569-\t\t\tgoto error;\n--\nmm/memory_hotplug.c=2271=static int memory_blocks_have_altmaps(u64 start, u64 size)\n--\nmm/memory_hotplug.c-2290-\nmm/memory_hotplug.c:2291:static int try_remove_memory(u64 start, u64 size)\nmm/memory_hotplug.c-2292-{\n--\nmm/memory_hotplug.c-2324-\t\t */\nmm/memory_hotplug.c:2325:\t\tremove_memory_block_devices(start, size);\nmm/memory_hotplug.c:2326:\t\tarch_remove_memory(start, size, NULL, NULL);\nmm/memory_hotplug.c-2327-\t} else {\nmm/memory_hotplug.c-2328-\t\t/* all memblocks in the range have altmaps */\nmm/memory_hotplug.c:2329:\t\tremove_memory_blocks_and_altmaps(start, size);\nmm/memory_hotplug.c-2330-\t}\n--\nmm/memory_hotplug.c-2344-/**\nmm/memory_hotplug.c:2345: * __remove_memory - Remove memory if every memory block is offline\nmm/memory_hotplug.c-2346- * @start: physical address of the region to remove\n--\nmm/memory_hotplug.c-2352- */\nmm/memory_hotplug.c:2353:void __remove_memory(u64 start, u64 size)\nmm/memory_hotplug.c-2354-{\n--\nmm/memory_hotplug.c-2359-\t */\nmm/memory_hotplug.c:2360:\tif (try_remove_memory(start, size))\nmm/memory_hotplug.c-2361-\t\tBUG();\n--\nmm/memory_hotplug.c-2367- */\nmm/memory_hotplug.c:2368:int remove_memory(u64 start, u64 size)\n\n"
}

gemini-3.8-flash

null

null

							input: 56639
							output: 23
							thoughts: 341
						

**Investigating Memory Removal and `ARCH_KEEP_MEMBLOCK`**

Okay, I need to understand this `try_remove_memory` function in `mm/memory_hotplug.c` and specifically, that conditional using `CONFIG_ARCH_KEEP_MEMBLOCK`. I see it calls `memblock_remove` if the config is enabled. My immediate thought is, on AMD64, is this even *enabled* in any of the commonly used configurations? I need to check the Kconfig files.

Let's look at `arch/x86/Kconfig`. Ah, here we go, `CONFIG_INTEL_TDX_HOST` selects `ARCH_KEEP_MEMBLOCK`. Hmm, Intel TDX host support. Okay, that makes sense. It *could* be enabled. But let me quickly look for other ways `ARCH_KEEP_MEMBLOCK` gets used, just to be sure.

Now, let's also check `drivers/firmware/efi/efi.c`. Ah, `efi_mem_reserve_iomem`! This function also uses `memblock_reserve` *if* `ARCH_KEEP_MEMBLOCK` is enabled. Okay, so that's another potential use case. Wait! Now I need to know what *calls* `efi_mem_reserve_iomem` or the related `efi_mem_reserve_persistent` function. I need to trace the callers to get the complete picture.

{
  "Expression": "efi_mem_reserve_iomem"
}

{
  "Output": "drivers/firmware/efi/efi.c=1060=static int __init efi_memreserve_map_root(void)\n--\ndrivers/firmware/efi/efi.c-1072-\ndrivers/firmware/efi/efi.c:1073:static int efi_mem_reserve_iomem(phys_addr_t addr, u64 size)\ndrivers/firmware/efi/efi.c-1074-{\n--\ndrivers/firmware/efi/efi.c-1091-\t/*\ndrivers/firmware/efi/efi.c:1092:\t * Given that efi_mem_reserve_iomem() can be called at any\ndrivers/firmware/efi/efi.c-1093-\t * time, only call memblock_reserve() if the architecture\n--\ndrivers/firmware/efi/efi.c=1102=int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)\n--\ndrivers/firmware/efi/efi.c-1127-\t\t\tmemunmap(rsv);\ndrivers/firmware/efi/efi.c:1128:\t\t\treturn efi_mem_reserve_iomem(addr, size);\ndrivers/firmware/efi/efi.c-1129-\t\t}\n--\ndrivers/firmware/efi/efi.c-1138-\ndrivers/firmware/efi/efi.c:1139:\trc = efi_mem_reserve_iomem(__pa(rsv), SZ_4K);\ndrivers/firmware/efi/efi.c-1140-\tif (rc) {\n--\ndrivers/firmware/efi/efi.c-1160-\ndrivers/firmware/efi/efi.c:1161:\treturn efi_mem_reserve_iomem(addr, size);\ndrivers/firmware/efi/efi.c-1162-}\n"
}

gemini-3.8-flash

null

null

							input: 57803
							output: 21
							thoughts: 14
						

Okay, here's my take on those thoughts, tailored for an expert audience, presented in the first person:

**Eavesdropping on `efi_mem_reserve_persistent`'s Circle of Influence**

Hmm, `efi_mem_reserve_persistent`... that function name rings a bell. But now I'm really digging in to the actual code. My initial question is: where is it *actually* being called? I need to understand its context within the UEFI ecosystem. I want to trace the call paths. Is it something invoked during early boot, perhaps? Or is it used later in the OS's runtime to allocate persistent memory regions? Knowing the caller is the key to understanding the intent. I immediately start mentally mapping out the possible scenarios. Are we talking about firmware runtime services? Or something within a specific driver? Or something else entirely?

{
  "Expression": "efi_mem_reserve_persistent"
}

{
  "Output": "drivers/firmware/efi/efi.c=1055=EXPORT_SYMBOL_GPL(efi_status_to_err);\ndrivers/firmware/efi/efi.c-1056-\ndrivers/firmware/efi/efi.c:1057:static DEFINE_SPINLOCK(efi_mem_reserve_persistent_lock);\ndrivers/firmware/efi/efi.c-1058-static struct linux_efi_memreserve *efi_memreserve_root __ro_after_init;\n--\ndrivers/firmware/efi/efi.c=1073=static int efi_mem_reserve_iomem(phys_addr_t addr, u64 size)\n--\ndrivers/firmware/efi/efi.c-1101-\ndrivers/firmware/efi/efi.c:1102:int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)\ndrivers/firmware/efi/efi.c-1103-{\n--\ndrivers/firmware/efi/efi.c-1155-\ndrivers/firmware/efi/efi.c:1156:\tspin_lock(\u0026efi_mem_reserve_persistent_lock);\ndrivers/firmware/efi/efi.c-1157-\trsv-\u003enext = efi_memreserve_root-\u003enext;\ndrivers/firmware/efi/efi.c-1158-\tefi_memreserve_root-\u003enext = __pa(rsv);\ndrivers/firmware/efi/efi.c:1159:\tspin_unlock(\u0026efi_mem_reserve_persistent_lock);\ndrivers/firmware/efi/efi.c-1160-\n--\ndrivers/irqchip/irq-gic-v3-its.c=2310=static int gic_reserve_range(phys_addr_t addr, unsigned long size)\n--\ndrivers/irqchip/irq-gic-v3-its.c-2312-\tif (efi_enabled(EFI_CONFIG_TABLES))\ndrivers/irqchip/irq-gic-v3-its.c:2313:\t\treturn efi_mem_reserve_persistent(addr, size);\ndrivers/irqchip/irq-gic-v3-its.c-2314-\n--\ninclude/linux/efi.h=759=extern void efi_mem_reserve(phys_addr_t addr, u64 size);\ninclude/linux/efi.h:760:extern int efi_mem_reserve_persistent(phys_addr_t addr, u64 size);\ninclude/linux/efi.h-761-extern u64 efi_get_fdt_params(struct efi_memory_map_data *data);\n"
}

gemini-3.8-flash

null

null

							input: 58699
							output: 20
							thoughts: 420
						

**Analyzing `memblock_discard` and Memory Management**

Okay, let's dive into what `memblock_free_all` and `memblock_discard` actually *do*. Specifically, I need to understand how they function within the x86 (amd64) architecture. Right, so unless `CONFIG_INTEL_TDX_HOST` is enabled, `memblock_discard()` gets called during the boot process, specifically within `mm/mm_init.c` inside `page_alloc_init_late()`. Let me see... here it is: the function itself:

```c
void __init memblock_discard(void)
{
	phys_addr_t addr;
	phys_addr_t size;

	if (memblock.memory.regions != memblock_memory_init_regions) {
		addr = __pa(memblock.memory.regions);
		size = PAGE_ALIGN(sizeof(struct memblock_region) *
				  memblock.memory.max);
		__memblock_free_late(addr, size);
	}

	if (memblock.reserved.regions != memblock_reserved_init_regions) {
		addr = __pa(memblock.reserved.regions);
		size = PAGE_ALIGN(sizeof(struct memblock_region) *
				  memblock.reserved.max);
		__memblock_free_late(addr, size);
	}

	memblock_memory = NULL;
}
```

Okay, so it appears that `memblock_discard()` is freeing the memory associated with the `memblock.memory.regions` and `memblock.reserved.regions` structures *after* they've served their purpose during early boot. Specifically, `__memblock_free_late` is being called which means these regions are being freed after the early boot stage is complete. Got it. Now, let's go over to `memblock.c` and see if we can get a better handle on this,

Aha! `__init_memblock` is defined there and depends on `CONFIG_ARCH_KEEP_MEMBLOCK`.

```c
#ifndef CONFIG_ARCH_KEEP_MEMBLOCK
#define __init_memblock __meminit
#define __initdata_memblock __meminitdata
void memblock_discard(void);
#else
#define __init_memblock
#define __initdata_memblock
static inline void memblock_discard(void) {}
#endif
```

If `CONFIG_ARCH_KEEP_MEMBLOCK` is *not* set, `__init_memblock` is defined as `__meminit`. Otherwise, `memblock_discard` is defined to nothing. Okay, so that must be where `__meminit` comes into play. What *is* `__meminit`? Let's check `include/linux/init.h` to see what's going on.

{
  "Expression": "define __meminit\\b"
}

{
  "Output": "include/linux/init.h-81-#ifdef CONFIG_MEMORY_HOTPLUG\ninclude/linux/init.h:82:#define __meminit\ninclude/linux/init.h-83-#define __meminitdata\n--\ninclude/linux/init.h-85-#else\ninclude/linux/init.h:86:#define __meminit\t__init\ninclude/linux/init.h-87-#define __meminitdata\t__initdata\n--\ntools/include/linux/init.h-17-#define __initconst\ntools/include/linux/init.h:18:#define __meminit\ntools/include/linux/init.h-19-#define __meminitdata\n"
}

gemini-3.8-flash

null

null

							input: 59961
							output: 29
							thoughts: 1412
						

**Analyzing Memory Hotplug Reachability in Syzkaller**

Okay, so I'm looking at this code and thinking, "Hold on a minute!" When `CONFIG_MEMORY_HOTPLUG` is enabled – and it *always* is, practically, in both standard Linux distributions and syzkaller configurations – that `__meminit` section is effectively *empty*, meaning it's not discarded during initialization. And what about `ARCH_KEEP_MEMBLOCK`? Specifically, if `CONFIG_ARCH_KEEP_MEMBLOCK` is enabled – like when `CONFIG_INTEL_TDX_HOST=y` on amd64, or on arm64/powerpc, etc. – `memblock` is preserved! Then, `memblock_add_node` and `memblock_remove` are definitely called during memory hotplug and hot-remove!

Now, the crucial question: is memory hotplug *reachable* in a fuzzing context on amd64? I have to be careful here. I need to refer back to the core triage philosophy for patch fuzzing that I know so well. The primary hurdle is reachability. Fuzzing only works on code that *can* be executed in standard virtualized environments. And I need to always keep in mind that I can't blindly trust claims like "no functional change" or "refactoring."

So I need to check the instructions. Specifically Sections 1, 2, and 3.

Let's see: the goal is to discover crashes, regressions, exposed latent bugs, and newly triggered assertions. Reachability is key. I need to make sure that the code can execute in a standard virtualized environment. If the code is structurally unreachable, it shouldn't be fuzzed. No matter if it adds assertions or complex logic. Section 2, specifically, lays out when to return `WorthFuzzing=false`. It says it should be only if the code falls strictly into one or more of these categories: non-kernel and non-executable changes, structurally unreachable hardware, and unreachable execution paths. And that section is pretty specific about what those things are. Section 3 defines the opposite, when to return `WorthFuzzing=true`. Basically, any time reachable code is touched, including memory management, synchronization, BPF, scheduler, networking, VFS, or syscall handling.

So, is early boot code reachable by syzkaller? Remember, syzkaller operates on a *running* kernel through syscalls and user-accessible interfaces: sysfs, procfs, ioctls, netlink, sockets, etc. It doesn't fuzz early boot code at all. It starts after the kernel has booted. But, the question isn't about *early* boot, but about code *after* boot. Can `memblock` be reached *after* boot? I need to check if it's *ever* executed after boot.

I need to look at the functions modified in this patch: `memblock_bsearch_start`, `memblock_add_range`, `memblock_isolate_range`, `memblock_search`, `memblock_dump`. Can any of those be called *after* boot? Memory hotplug *definitely* runs after boot! It's *designed* to. So, if memory is added or removed post-boot, can syzkaller trigger that?

How is memory hotplug triggered? Well, the obvious one is `/sys/devices/system/memory/probe` (if `CONFIG_ARCH_MEMORY_PROBE` and `CONFIG_MEMORY_HOTPLUG` are enabled). Writing a physical address to `/sys/devices/system/memory/probe` triggers a sequence: `probe_store` -> `__add_memory(nid, phys_addr, size, MHP_NONE)` -> `__add_memory_resource`. Importantly, it seems like if `IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)` that `memblock_add_node` *is* called.

Does syzkaller have access to `/sys/devices/system/memory/probe`? It should! Syzkaller is known to fuzz `/sys` files if they are mounted/writable. And, it fuzzes pseudo-syscalls as well! What about other drivers? What about virtio-mem or DAX kmem? Could they trigger hotplug? Looking at `drivers/dax/kmem.c`... let's check how dax kmem works. Does syzkaller interact with dax kmem? I need to check `dax_kmem.c`. I have a pretty strong hunch this is a path that's reachable and worth investigating.

{
  "Expression": "dax_kmem",
  "PathPrefix": "drivers/dax"
}

{
  "Output": "drivers/dax/Kconfig=50=config DEV_DAX_CXL\n--\ndrivers/dax/Kconfig-61-\t  Per usual it can remain as dedicated access via a device interface, or\ndrivers/dax/Kconfig:62:\t  converted to \"System RAM\" via the dax_kmem facility.\ndrivers/dax/Kconfig-63-\n--\ndrivers/dax/bus.c=67=static int dax_match_type(const struct dax_device_driver *dax_drv, struct device *dev)\n--\ndrivers/dax/bus.c-77-\ndrivers/dax/bus.c:78:\t/* default to device mode if dax_kmem is disabled */\ndrivers/dax/bus.c-79-\tif (dax_drv-\u003etype == DAXDRV_DEVICE_TYPE \u0026\u0026\n--\ndrivers/dax/hmem/hmem.c=12=static int dax_hmem_probe(struct platform_device *pdev)\n--\ndrivers/dax/hmem/hmem.c-22-\t * wants to manipulate the range partitioning before the devices\ndrivers/dax/hmem/hmem.c:23:\t * are created, so do not send them to the dax_kmem driver by\ndrivers/dax/hmem/hmem.c-24-\t * default.\n--\ndrivers/dax/kmem.c=29=static bool any_hotremove_failed;\ndrivers/dax/kmem.c-30-\ndrivers/dax/kmem.c:31:static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r)\ndrivers/dax/kmem.c-32-{\n--\ndrivers/dax/kmem.c-44-\ndrivers/dax/kmem.c:45:struct dax_kmem_data {\ndrivers/dax/kmem.c-46-\tconst char *res_name;\n--\ndrivers/dax/kmem.c=62=static void kmem_put_memory_types(void)\n--\ndrivers/dax/kmem.c-68-/* True for the online states a kmem dax device can hold. */\ndrivers/dax/kmem.c:69:static bool dax_kmem_state_is_online(int state)\ndrivers/dax/kmem.c-70-{\n--\ndrivers/dax/kmem.c-76-/**\ndrivers/dax/kmem.c:77: * dax_kmem_do_hotplug - hotplug memory for dax kmem device\ndrivers/dax/kmem.c-78- * @dev_dax: the dev_dax instance\ndrivers/dax/kmem.c:79: * @data: the dax_kmem_data structure with resource tracking\ndrivers/dax/kmem.c-80- * @online_type: the online policy to use for the memory blocks\n--\ndrivers/dax/kmem.c-86- */\ndrivers/dax/kmem.c:87:static int dax_kmem_do_hotplug(struct dev_dax *dev_dax,\ndrivers/dax/kmem.c:88:\t\t\t       struct dax_kmem_data *data,\ndrivers/dax/kmem.c-89-\t\t\t       int online_type)\n--\ndrivers/dax/kmem.c-94-\ndrivers/dax/kmem.c:95:\tif (dax_kmem_state_is_online(data-\u003estate))\ndrivers/dax/kmem.c-96-\t\treturn -EINVAL;\n--\ndrivers/dax/kmem.c-103-\ndrivers/dax/kmem.c:104:\t\trc = dax_kmem_range(dev_dax, i, \u0026range);\ndrivers/dax/kmem.c-105-\t\tif (rc)\n--\ndrivers/dax/kmem.c-154-/**\ndrivers/dax/kmem.c:155: * dax_kmem_init_resources - create memory regions for dax kmem\ndrivers/dax/kmem.c-156- * @dev_dax: the dev_dax instance\ndrivers/dax/kmem.c:157: * @data: the dax_kmem_data structure with resource tracking\ndrivers/dax/kmem.c-158- *\n--\ndrivers/dax/kmem.c-162- */\ndrivers/dax/kmem.c:163:static int dax_kmem_init_resources(struct dev_dax *dev_dax,\ndrivers/dax/kmem.c:164:\t\t\t\t   struct dax_kmem_data *data)\ndrivers/dax/kmem.c-165-{\n--\ndrivers/dax/kmem.c-172-\ndrivers/dax/kmem.c:173:\t\trc = dax_kmem_range(dev_dax, i, \u0026range);\ndrivers/dax/kmem.c-174-\t\tif (rc)\n--\ndrivers/dax/kmem.c-209-/**\ndrivers/dax/kmem.c:210: * dax_kmem_do_hotremove - hot-remove memory for dax kmem device\ndrivers/dax/kmem.c-211- * @dev_dax: the dev_dax instance\ndrivers/dax/kmem.c:212: * @data: the dax_kmem_data structure with resource tracking\ndrivers/dax/kmem.c-213- *\n--\ndrivers/dax/kmem.c-219- */\ndrivers/dax/kmem.c:220:static int dax_kmem_do_hotremove(struct dev_dax *dev_dax,\ndrivers/dax/kmem.c:221:\t\t\t\t struct dax_kmem_data *data)\ndrivers/dax/kmem.c-222-{\n--\ndrivers/dax/kmem.c-236-\t\t\tcontinue;\ndrivers/dax/kmem.c:237:\t\tif (dax_kmem_range(dev_dax, i, \u0026range))\ndrivers/dax/kmem.c-238-\t\t\tcontinue;\n--\ndrivers/dax/kmem.c-267-#else\ndrivers/dax/kmem.c:268:static int dax_kmem_do_hotremove(struct dev_dax *dev_dax,\ndrivers/dax/kmem.c:269:\t\t\t\t struct dax_kmem_data *data)\ndrivers/dax/kmem.c-270-{\n--\ndrivers/dax/kmem.c-275-/**\ndrivers/dax/kmem.c:276: * dax_kmem_cleanup_resources - remove the dax memory resources\ndrivers/dax/kmem.c-277- * @dev_dax: the dev_dax instance\ndrivers/dax/kmem.c:278: * @data: the dax_kmem_data structure with resource tracking\ndrivers/dax/kmem.c-279- *\n--\ndrivers/dax/kmem.c-281- */\ndrivers/dax/kmem.c:282:static void dax_kmem_cleanup_resources(struct dev_dax *dev_dax,\ndrivers/dax/kmem.c:283:\t\t\t\t       struct dax_kmem_data *data)\ndrivers/dax/kmem.c-284-{\n--\ndrivers/dax/kmem.c-307-\ndrivers/dax/kmem.c:308:static int dax_kmem_parse_state(const char *buf)\ndrivers/dax/kmem.c-309-{\n--\ndrivers/dax/kmem.c=323=static ssize_t state_show(struct device *dev,\n--\ndrivers/dax/kmem.c-325-{\ndrivers/dax/kmem.c:326:\tstruct dax_kmem_data *data = dev_get_drvdata(dev);\ndrivers/dax/kmem.c-327-\tconst char *state_str;\n--\ndrivers/dax/kmem.c=337=static ssize_t state_store(struct device *dev, struct device_attribute *attr,\n--\ndrivers/dax/kmem.c-340-\tstruct dev_dax *dev_dax = to_dev_dax(dev);\ndrivers/dax/kmem.c:341:\tstruct dax_kmem_data *data = dev_get_drvdata(dev);\ndrivers/dax/kmem.c-342-\tint online_type;\n--\ndrivers/dax/kmem.c-344-\ndrivers/dax/kmem.c:345:\tonline_type = dax_kmem_parse_state(buf);\ndrivers/dax/kmem.c-346-\tif (online_type \u003c DAX_KMEM_UNPLUGGED)\n--\ndrivers/dax/kmem.c-355-\tif (online_type == DAX_KMEM_UNPLUGGED) {\ndrivers/dax/kmem.c:356:\t\trc = dax_kmem_do_hotremove(dev_dax, data);\ndrivers/dax/kmem.c-357-\t\tif (rc)\n--\ndrivers/dax/kmem.c-367-\t/* Re-acquire resources if previously unplugged, otherwise no-op */\ndrivers/dax/kmem.c:368:\trc = dax_kmem_init_resources(dev_dax, data);\ndrivers/dax/kmem.c-369-\tif (rc \u003c 0)\n--\ndrivers/dax/kmem.c-371-\ndrivers/dax/kmem.c:372:\trc = dax_kmem_do_hotplug(dev_dax, data, online_type);\ndrivers/dax/kmem.c-373-\tif (rc \u003c 0) {\ndrivers/dax/kmem.c-374-\t\t/* Total failure, drop the reservations we took. */\ndrivers/dax/kmem.c:375:\t\tdax_kmem_cleanup_resources(dev_dax, data);\ndrivers/dax/kmem.c-376-\t\treturn rc;\n--\ndrivers/dax/kmem.c-382-\ndrivers/dax/kmem.c:383:static int dev_dax_kmem_probe(struct dev_dax *dev_dax)\ndrivers/dax/kmem.c-384-{\n--\ndrivers/dax/kmem.c-386-\tunsigned long total_len = 0, orig_len = 0;\ndrivers/dax/kmem.c:387:\tstruct dax_kmem_data *data;\ndrivers/dax/kmem.c-388-\tstruct memory_dev_type *mtype;\n--\ndrivers/dax/kmem.c-415-\t\torig_len += range_len(\u0026dev_dax-\u003eranges[i].range);\ndrivers/dax/kmem.c:416:\t\trc = dax_kmem_range(dev_dax, i, \u0026range);\ndrivers/dax/kmem.c-417-\t\tif (rc) {\n--\ndrivers/dax/kmem.c-440-\tif (!data)\ndrivers/dax/kmem.c:441:\t\tgoto err_dax_kmem_data;\ndrivers/dax/kmem.c-442-\n--\ndrivers/dax/kmem.c-455-\ndrivers/dax/kmem.c:456:\trc = dax_kmem_init_resources(dev_dax, data);\ndrivers/dax/kmem.c-457-\tif (rc \u003c 0)\n--\ndrivers/dax/kmem.c-459-\ndrivers/dax/kmem.c:460:\trc = dax_kmem_do_hotplug(dev_dax, data, online_type);\ndrivers/dax/kmem.c-461-\tif (rc \u003c 0)\n--\ndrivers/dax/kmem.c-467-err_hotplug:\ndrivers/dax/kmem.c:468:\tdax_kmem_cleanup_resources(dev_dax, data);\ndrivers/dax/kmem.c-469-err_resources:\n--\ndrivers/dax/kmem.c-475-\tkfree(data);\ndrivers/dax/kmem.c:476:err_dax_kmem_data:\ndrivers/dax/kmem.c-477-\tclear_node_memory_type(numa_node, mtype);\n--\ndrivers/dax/kmem.c-488- */\ndrivers/dax/kmem.c:489:static int dax_kmem_remove_ranges(struct dev_dax *dev_dax,\ndrivers/dax/kmem.c:490:\t\t\t\t  struct dax_kmem_data *data)\ndrivers/dax/kmem.c-491-{\n--\ndrivers/dax/kmem.c-497-\ndrivers/dax/kmem.c:498:\t\tif (!data-\u003eres[i] || dax_kmem_range(dev_dax, i, \u0026range))\ndrivers/dax/kmem.c-499-\t\t\tcontinue;\n--\ndrivers/dax/kmem.c-512-\ndrivers/dax/kmem.c:513:static void dev_dax_kmem_remove(struct dev_dax *dev_dax)\ndrivers/dax/kmem.c-514-{\n--\ndrivers/dax/kmem.c-516-\tstruct device *dev = \u0026dev_dax-\u003edev;\ndrivers/dax/kmem.c:517:\tstruct dax_kmem_data *data = dev_get_drvdata(dev);\ndrivers/dax/kmem.c-518-\ndrivers/dax/kmem.c-519-\t/*\ndrivers/dax/kmem.c:520:\t * Remove every range that is still added.  dax_kmem_remove_ranges()\ndrivers/dax/kmem.c-521-\t * uses remove_memory(), which never offlines: an online block fails\n--\ndrivers/dax/kmem.c-528-\t */\ndrivers/dax/kmem.c:529:\tif (dax_kmem_remove_ranges(dev_dax, data)) {\ndrivers/dax/kmem.c-530-\t\tdev_err(dev, \"Hotplug regions stuck online until reboot\\n\");\n--\ndrivers/dax/kmem.c-548-#else\ndrivers/dax/kmem.c:549:static void dev_dax_kmem_remove(struct dev_dax *dev_dax)\ndrivers/dax/kmem.c-550-{\n--\ndrivers/dax/kmem.c=562=static DEVICE_ATTR_RW(state);\ndrivers/dax/kmem.c-563-\ndrivers/dax/kmem.c:564:static struct attribute *dev_dax_kmem_attrs[] = {\ndrivers/dax/kmem.c-565-\t\u0026dev_attr_state.attr,\n--\ndrivers/dax/kmem.c-567-};\ndrivers/dax/kmem.c:568:ATTRIBUTE_GROUPS(dev_dax_kmem);\ndrivers/dax/kmem.c-569-\ndrivers/dax/kmem.c:570:static struct dax_device_driver device_dax_kmem_driver = {\ndrivers/dax/kmem.c:571:\t.probe = dev_dax_kmem_probe,\ndrivers/dax/kmem.c:572:\t.remove = dev_dax_kmem_remove,\ndrivers/dax/kmem.c-573-\t.type = DAXDRV_KMEM_TYPE,\ndrivers/dax/kmem.c-574-\t.drv = {\ndrivers/dax/kmem.c:575:\t\t.dev_groups = dev_dax_kmem_groups,\ndrivers/dax/kmem.c-576-\t},\n--\ndrivers/dax/kmem.c-578-\ndrivers/dax/kmem.c:579:static int __init dax_kmem_init(void)\ndrivers/dax/kmem.c-580-{\n--\ndrivers/dax/kmem.c-587-\ndrivers/dax/kmem.c:588:\trc = dax_driver_register(\u0026device_dax_kmem_driver);\ndrivers/dax/kmem.c-589-\tif (rc)\n--\ndrivers/dax/kmem.c-599-\ndrivers/dax/kmem.c:600:static void __exit dax_kmem_exit(void)\ndrivers/dax/kmem.c-601-{\ndrivers/dax/kmem.c:602:\tdax_driver_unregister(\u0026device_dax_kmem_driver);\ndrivers/dax/kmem.c-603-\tif (!any_hotremove_failed)\n--\ndrivers/dax/kmem.c=610=MODULE_LICENSE(\"GPL v2\");\ndrivers/dax/kmem.c:611:module_init(dax_kmem_init);\ndrivers/dax/kmem.c:612:module_exit(dax_kmem_exit);\ndrivers/dax/kmem.c-613-MODULE_ALIAS_DAX_DEVICE(0);\n"
}

gemini-3.8-flash

null

null

							input: 66939
							output: 31
							thoughts: 410
						

**Analyzing Memory Hotplug and Removal Mechanisms**

Okay, let's break this down. My initial focus is on how memory hotplug and hotremove are handled, specifically within the context of DAX kmem and virtio-mem. I'm seeing a common pattern emerging.

First, I observe that when memory is added via `dax_kmem_do_hotplug` it funnels through `add_memory_resource`, then `__add_memory_resource`. The crucial part for retaining memory configuration across reboots is handled by `memblock_add_node` and ultimately `memblock_add_range` if `CONFIG_ARCH_KEEP_MEMBLOCK` is enabled.

Conversely, memory removal with `dax_kmem_do_hotremove` goes through `offline_and_remove_memory_ranges`, then `try_remove_memory`.  Again, if the configuration must be retained across reboots, we end up using `memblock_remove` (after a check if `CONFIG_ARCH_KEEP_MEMBLOCK` is enabled) ultimately calling `memblock_remove_range` and `memblock_isolate_range`. This is essentially the reverse process.

Now, for virtio-mem, the approach is very similar. `virtio_mem_add_memory` directly calls `add_memory_resource` and follows the same path down to `memblock_add_range`. Removal, through `virtio_mem_remove_memory`, leverages `remove_memory`, which again funnels into `try_remove_memory` and `memblock_remove` and finally `memblock_isolate_range`.

Interestingly, I notice that `memblock_bsearch_start` is used by both `memblock_add_range` and `memblock_isolate_range`. This means it likely has an important role in inserting or removing ranges in a sorted manner within the memory block structure.

I have to now widen the lens and check the calls to `memblock_search`. So, where is `memblock_search` called? I see several functions that utilize `memblock_search`: `memblock_is_reserved`, `memblock_is_memory`, `memblock_is_map_memory`, `memblock_search_pfn_nid`, and `memblock_is_region_memory`. It seems these functions offer methods to check if a specific physical address is reserved, considered memory, is mapable, used for specific page frame number (PFN) node lookups, or is defined as a memory region.

Now, my next step is to grep the kernel source for each of these `memblock_*` calls to understand the broader context and see where else they’re used and what that might imply about the architecture. I’ll be able to infer what dependencies exist and see if the same approach for DAX/virtio-mem is used elsewhere.

{
  "Expression": "memblock_is_(reserved|memory|map_memory|region_memory)"
}

{
  "Output": "arch/arm/kernel/machine_kexec.c=33=int machine_kexec_prepare(struct kimage *image)\n--\narch/arm/kernel/machine_kexec.c-57-\narch/arm/kernel/machine_kexec.c:58:\t\tif (!memblock_is_region_memory(idmap_to_phys(current_segment-\u003emem),\narch/arm/kernel/machine_kexec.c-59-\t\t\t\t\t       current_segment-\u003ememsz))\n--\narch/arm/mach-sti/platsmp.c=49=static void __init sti_smp_prepare_cpus(unsigned int max_cpus)\n--\narch/arm/mach-sti/platsmp.c-85-\narch/arm/mach-sti/platsmp.c:86:\t\tif (!memblock_is_memory(release_phys))\narch/arm/mach-sti/platsmp.c-87-\t\t\tcpu_strt_ptr =\n--\narch/arm/mm/ioremap.c=274=static void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn,\n--\narch/arm/mm/ioremap.c-317-\t */\narch/arm/mm/ioremap.c:318:\tif (WARN_ON(memblock_is_map_memory(PFN_PHYS(pfn)) \u0026\u0026\narch/arm/mm/ioremap.c-319-\t\t    mtype != MT_MEMORY_RW))\n--\narch/arm/mm/ioremap.c=515=bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size,\n--\narch/arm/mm/ioremap.c-517-{\narch/arm/mm/ioremap.c:518:\treturn memblock_is_map_memory(offset);\narch/arm/mm/ioremap.c-519-}\n--\narch/arm64/kernel/acpi.c=295=void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)\n--\narch/arm64/kernel/acpi.c-331-\t\tcase EFI_PERSISTENT_MEMORY:\narch/arm64/kernel/acpi.c:332:\t\t\tif (memblock_is_map_memory(phys) ||\narch/arm64/kernel/acpi.c:333:\t\t\t    !memblock_is_region_memory(phys, size)) {\narch/arm64/kernel/acpi.c-334-\t\t\t\tpr_warn(FW_BUG \"requested region covers kernel memory @ %pa\\n\", \u0026phys);\n--\narch/arm64/kernel/acpi.c-366-\t\t\t */\narch/arm64/kernel/acpi.c:367:\t\t\tif (memblock_is_map_memory(phys))\narch/arm64/kernel/acpi.c-368-\t\t\t\treturn (void __iomem *)__phys_to_virt(phys);\n--\narch/arm64/mm/init.c=167=int pfn_is_map_memory(unsigned long pfn)\n--\narch/arm64/mm/init.c-174-\narch/arm64/mm/init.c:175:\treturn memblock_is_map_memory(addr);\narch/arm64/mm/init.c-176-}\n--\narch/arm64/mm/mmap.c=43=int valid_phys_addr_range(phys_addr_t addr, size_t size)\n--\narch/arm64/mm/mmap.c-54-\t */\narch/arm64/mm/mmap.c:55:\treturn memblock_is_region_memory(addr, size) \u0026\u0026\narch/arm64/mm/mmap.c:56:\t       memblock_is_map_memory(addr);\narch/arm64/mm/mmap.c-57-}\n--\narch/loongarch/kernel/acpi.c=56=void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)\narch/loongarch/kernel/acpi.c-57-{\narch/loongarch/kernel/acpi.c:58:\tif (!memblock_is_memory(phys))\narch/loongarch/kernel/acpi.c-59-\t\treturn ioremap(phys, size);\n--\narch/loongarch/kernel/setup.c=380=static void __init check_kernel_sections_mem(void)\n--\narch/loongarch/kernel/setup.c-384-\narch/loongarch/kernel/setup.c:385:\tif (!memblock_is_region_memory(start, size)) {\narch/loongarch/kernel/setup.c-386-\t\tpr_info(\"Kernel sections are not in the memory maps\\n\");\n--\narch/loongarch/mm/init.c=39=int __ref page_is_ram(unsigned long pfn)\n--\narch/loongarch/mm/init.c-42-\narch/loongarch/mm/init.c:43:\treturn memblock_is_memory(addr) \u0026\u0026 !memblock_is_reserved(addr);\narch/loongarch/mm/init.c-44-}\n--\narch/loongarch/mm/mmap.c=133=int valid_phys_addr_range(phys_addr_t addr, size_t size)\n--\narch/loongarch/mm/mmap.c-144-\t */\narch/loongarch/mm/mmap.c:145:\treturn memblock_is_region_memory(addr, size) \u0026\u0026 memblock_is_map_memory(addr);\narch/loongarch/mm/mmap.c-146-}\n--\narch/loongarch/mm/pageattr.c=161=bool kernel_page_present(struct page *page)\n--\narch/loongarch/mm/pageattr.c-170-\tif (addr \u003c vm_map_base)\narch/loongarch/mm/pageattr.c:171:\t\treturn memblock_is_memory(__pa(addr));\narch/loongarch/mm/pageattr.c-172-\n--\narch/mips/kernel/setup.c=508=static void __init check_kernel_sections_mem(void)\n--\narch/mips/kernel/setup.c-512-\narch/mips/kernel/setup.c:513:\tif (!memblock_is_region_memory(start, size)) {\narch/mips/kernel/setup.c-514-\t\tpr_info(\"Kernel sections are not in the memory maps\\n\");\n--\narch/mips/mm/init.c=423=static inline void __init highmem_init(void)\n--\narch/mips/mm/init.c-439-\narch/mips/mm/init.c:440:\t\tif (!memblock_is_memory(PFN_PHYS(tmp)))\narch/mips/mm/init.c-441-\t\t\tSetPageReserved(page);\n--\narch/powerpc/kernel/crash_dump.c=72=ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,\n--\narch/powerpc/kernel/crash_dump.c-83-\narch/powerpc/kernel/crash_dump.c:84:\tif (memblock_is_region_memory(paddr, csize)) {\narch/powerpc/kernel/crash_dump.c-85-\t\tvaddr = __va(paddr);\n--\narch/powerpc/kernel/prom.c=117=static void __init move_device_tree(void)\n--\narch/powerpc/kernel/prom.c-127-\tif ((memory_limit \u0026\u0026 (start + size) \u003e PHYSICAL_START + memory_limit) ||\narch/powerpc/kernel/prom.c:128:\t    !memblock_is_memory(start + size - 1) ||\narch/powerpc/kernel/prom.c-129-\t    overlaps_crashkernel(start, size) || overlaps_initrd(start, size)) {\n--\narch/riscv/kernel/acpi.c=227=void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)\n--\narch/riscv/kernel/acpi.c-263-\t\tcase EFI_PERSISTENT_MEMORY:\narch/riscv/kernel/acpi.c:264:\t\t\tif (memblock_is_map_memory(phys) ||\narch/riscv/kernel/acpi.c:265:\t\t\t    !memblock_is_region_memory(phys, size)) {\narch/riscv/kernel/acpi.c-266-\t\t\t\tpr_warn(FW_BUG \"requested region covers kernel memory\\n\");\n--\narch/riscv/kernel/acpi.c-297-\t\t\t */\narch/riscv/kernel/acpi.c:298:\t\t\tif (memblock_is_map_memory(phys))\narch/riscv/kernel/acpi.c-299-\t\t\t\treturn (void __iomem *)__va(phys);\n--\narch/riscv/kernel/setup.c=135=static void __init init_resources(void)\n--\narch/riscv/kernel/setup.c-180-\t\t */\narch/riscv/kernel/setup.c:181:\t\tif (memblock_is_memory(res-\u003estart)) {\narch/riscv/kernel/setup.c-182-\t\t\t/* Re-use this pre-allocated resource */\n--\narch/x86/mm/init.c=346=static void __ref adjust_range_page_size_mask(struct map_range *mr,\n--\narch/x86/mm/init.c-361-\narch/x86/mm/init.c:362:\t\t\tif (memblock_is_region_memory(start, end - start))\narch/x86/mm/init.c-363-\t\t\t\tmr[i].page_size_mask |= 1\u003c\u003cPG_LEVEL_2M;\n--\narch/x86/mm/init.c-369-\narch/x86/mm/init.c:370:\t\t\tif (memblock_is_region_memory(start, end - start))\narch/x86/mm/init.c-371-\t\t\t\tmr[i].page_size_mask |= 1\u003c\u003cPG_LEVEL_1G;\n--\narch/x86/xen/enlighten_hvm.c=50=static void __init reserve_shared_info(void)\n--\narch/x86/xen/enlighten_hvm.c-63-\t     !e820__mapped_all(pa, pa + PAGE_SIZE, E820_TYPE_RAM) ||\narch/x86/xen/enlighten_hvm.c:64:\t     memblock_is_reserved(pa);\narch/x86/xen/enlighten_hvm.c-65-\t     pa += PAGE_SIZE)\n--\narch/x86/xen/setup.c=601=phys_addr_t __init xen_find_free_area(phys_addr_t size)\n--\narch/x86/xen/setup.c-611-\t\tfor (addr = start; addr \u003c start + size; addr += PAGE_SIZE) {\narch/x86/xen/setup.c:612:\t\t\tif (!memblock_is_reserved(addr))\narch/x86/xen/setup.c-613-\t\t\t\tcontinue;\n--\ndrivers/firmware/efi/efi-init.c=68=static void __init init_primary_display(void)\n--\ndrivers/firmware/efi/efi-init.c-81-\ndrivers/firmware/efi/efi-init.c:82:\t\tif (memblock_is_map_memory(sysfb_primary_display.screen.lfb_base))\ndrivers/firmware/efi/efi-init.c-83-\t\t\tmemblock_mark_nomap(sysfb_primary_display.screen.lfb_base,\n--\ninclude/linux/memblock.h=289=static inline bool memblock_is_nomap(struct memblock_region *m)\n--\ninclude/linux/memblock.h-293-\ninclude/linux/memblock.h:294:static inline bool memblock_is_reserved_noinit(struct memblock_region *m)\ninclude/linux/memblock.h-295-{\n--\ninclude/linux/memblock.h=496=void memblock_mem_limit_remove_map(phys_addr_t limit);\ninclude/linux/memblock.h:497:bool memblock_is_memory(phys_addr_t addr);\ninclude/linux/memblock.h:498:bool memblock_is_map_memory(phys_addr_t addr);\ninclude/linux/memblock.h:499:bool memblock_is_region_memory(phys_addr_t base, phys_addr_t size);\ninclude/linux/memblock.h:500:bool memblock_is_reserved(phys_addr_t addr);\ninclude/linux/memblock.h-501-bool memblock_is_region_reserved(phys_addr_t base, phys_addr_t size);\n--\ninit/initramfs.c=617=void __init reserve_initrd_mem(void)\n--\ninit/initramfs.c-636-\ninit/initramfs.c:637:\tif (!memblock_is_region_memory(start, size)) {\ninit/initramfs.c-638-\t\tpr_err(\"INITRD: 0x%08llx+0x%08lx is not a memory region\",\n--\nmm/memblock.c=2093=static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)\n--\nmm/memblock.c-2101-\nmm/memblock.c:2102:bool __init_memblock memblock_is_reserved(phys_addr_t addr)\nmm/memblock.c-2103-{\n--\nmm/memblock.c-2106-\nmm/memblock.c:2107:bool __init_memblock memblock_is_memory(phys_addr_t addr)\nmm/memblock.c-2108-{\n--\nmm/memblock.c-2111-\nmm/memblock.c:2112:bool __init_memblock memblock_is_map_memory(phys_addr_t addr)\nmm/memblock.c-2113-{\n--\nmm/memblock.c=2121=int __init_memblock memblock_search_pfn_nid(unsigned long pfn,\n--\nmm/memblock.c-2136-/**\nmm/memblock.c:2137: * memblock_is_region_memory - check if a region is a subset of memory\nmm/memblock.c-2138- * @base: base of region to check\n--\nmm/memblock.c-2145- */\nmm/memblock.c:2146:bool __init_memblock memblock_is_region_memory(phys_addr_t base, phys_addr_t size)\nmm/memblock.c-2147-{\n--\nmm/memblock.c=2413=static void __init memmap_init_reserved_pages(void)\n--\nmm/memblock.c-2448-\tfor_each_reserved_mem_region(region) {\nmm/memblock.c:2449:\t\tif (!memblock_is_reserved_noinit(region)) {\nmm/memblock.c-2450-\t\t\tnid = memblock_get_region_node(region);\n"
}

gemini-3.8-flash

null

null

### 1. Approaches Tried and Results

- **Examined the Git Diff**:
  - The patch modifies `mm/memblock.c`.
  - Removed macro `for_each_memblock_type`.
  - Added `memblock_bsearch_start(struct memblock_type *type, phys_addr_t base)` (marked `__init_memblock static`).
  - Updated `memblock_add_range()`, `memblock_isolate_range()`, and `memblock_search()` to use `memblock_bsearch_start()` to find the first candidate index instead of iterating from index 0.
  - Rewrote `memblock_search()` to directly check `memblock_bsearch_start()` results.
  - Rewrote loop in `memblock_dump()` to open-code the index loop.

- **Investigated `__init_memblock` and Subsystem Lifecycles**:
  - Grepped `__init_memblock`: in `include/linux/memblock.h`, `#ifndef CONFIG_ARCH_KEEP_MEMBLOCK #define __init_memblock __meminit`, else `#define __init_memblock`.
  - In architectures without `ARCH_KEEP_MEMBLOCK`, memblock code and data structures are discarded during boot by `memblock_free_all()` and `memblock_discard()` (called in `mm_core_init()` / `page_alloc_init_late()`).
  - Grepped `ARCH_KEEP_MEMBLOCK`: Selected unconditionally by ARM, ARM64, LOONGARCH, MIPS, PPC, conditionally on RISCV (ACPI || KEXEC).
  - On the target architecture (`amd64` / x86_64), `ARCH_KEEP_MEMBLOCK` is selected when `CONFIG_INTEL_TDX_HOST` is enabled (`arch/x86/Kconfig:1874`).

- **Investigated Runtime Call Paths to Modified Functions**:
  - Investigated callers of modified functions: `memblock_bsearch_start`, `memblock_add_range`, `memblock_isolate_range`, `memblock_search`, `memblock_dump`.
  - `memblock_bsearch_start` is static in `mm/memblock.c`, called by `memblock_add_range`, `memblock_isolate_range`, `memblock_search`.
  - `memblock_add_range` is called by:
    - `memblock_add_node()`
    - `memblock_add()`
    - `__memblock_reserve()`
    - `memblock_physmem_add()`
  - `memblock_isolate_range` is called by:
    - `memblock_remove_range()` -> called by `memblock_remove()` (and `memblock_phys_free()`)
    - `memblock_setclr_flag()`
    - `memblock_set_node()`
    - `memblock_cap_memory_range()`
  - Traced runtime callers of `memblock_add_node()` and `memblock_remove()`:
    - In `mm/memory_hotplug.c:1534` (`__add_memory_resource`), when `IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)`, `memblock_add_node(start, size, nid, memblock_flags)` is called during runtime memory hot-add.
    - In `mm/memory_hotplug.c:1602` and `mm/memory_hotplug.c:2332` (`try_remove_memory`), when `IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)`, `memblock_remove(start, size)` is called during runtime memory hot-remove.
  - Investigated entry points for memory hotplug reachable by syzkaller:
    - Sysfs memory probe interface: `drivers/base/memory.c:572` (`probe_store` writes to `/sys/devices/system/memory/probe` calls `__add_memory`). Enabled via `CONFIG_ARCH_MEMORY_PROBE` (available on x86).
    - Virtio-mem driver: `drivers/virtio/virtio_mem.c` calls `add_memory()`, `remove_memory()`, `offline_and_remove_memory()`. Virtio-mem is a virtual device emulated in QEMU.
    - DAX kmem: `drivers/dax/kmem.c` calls `offline_and_remove_memory_ranges()`.
    - Memory offline/removal via sysfs: `/sys/devices/system/memory/memoryX/state` offlines memory, and drivers (virtio-mem, dax_kmem, etc.) trigger `remove_memory()` / `try_remove_memory()`.
    - DebugFS: `/sys/kernel/debug/memblock/` exists if `CONFIG_ARCH_KEEP_MEMBLOCK && CONFIG_DEBUG_FS`, but reads only iterate over regions (`memblock_debug_show`), not calling the search/add/isolate functions.

### 2. Current Hypotheses / Lines of Investigation

- **Reachability and WorthFuzzing Evaluation**:
  - The patch modifies core memory management code (`mm/memblock.c`).
  - While memblock is primarily an early-boot allocator, when `CONFIG_ARCH_KEEP_MEMBLOCK` is enabled (selected by `CONFIG_INTEL_TDX_HOST` on amd64), memblock data structures are kept at runtime and actively modified during runtime memory hotplug and hot-remove (`__add_memory_resource` calls `memblock_add_node` -> `memblock_add_range`, and `try_remove_memory` calls `memblock_remove` -> `memblock_remove_range` -> `memblock_isolate_range`).
  - Both memory hotplug and virtio-mem are accessible in standard QEMU environments (via sysfs `/sys/devices/system/memory/probe` when `CONFIG_ARCH_MEMORY_PROBE=y`, or via virtio-mem devices).
  - The patch alters search algorithms (linear scan replaced with binary search `memblock_bsearch_start`) and loop boundaries in core insertion/isolation routines.
  - Subsystem: Core Subsystems / MM. According to triage rules: modifications in `mm/` that alter reachable algorithm flows and state management qualify for fuzzing.
  - Verdict: `WorthFuzzing=true`.

- **Target Symbols for Fuzzing (FocusSymbols)**:
  - Avoid ubiquitous hot-paths (e.g. general page allocator wrappers).
  - Specific target symbols implementing the altered logic:
    - `memblock_add_range` (static, but inlined/exercised via `memblock_add_node`)
    - `memblock_isolate_range` (static, exercised via `memblock_remove`)
    - `memblock_search`
    - API entrypoints: `memblock_add_node`, `memblock_remove`, `memblock_add`, `memblock_search_pfn_nid`
    - Or direct non-static callers / subsystem entry points in memory hotplug: `add_memory`, `try_remove_memory`, `__add_memory_resource`.

- **Configuration Requirements (EnableConfigs)**:
  - `ARCH_KEEP_MEMBLOCK`: Requires `INTEL_TDX_HOST` on x86_64 (`arch/x86/Kconfig`).
  - `MEMORY_HOTPLUG`: Required for runtime memory addition/removal (`mm/memory_hotplug.c`).
  - `MEMORY_HOTREMOVE`: For `try_remove_memory`.
  - `ARCH_MEMORY_PROBE`: For sysfs `/sys/devices/system/memory/probe`.
  - `VIRTIO_MEM`: For emulated virtio-mem hotplug device in QEMU.

### 3. Key Files, Functions, and Code References

- **`mm/memblock.c`**:
  ```c
  static int __init_memblock memblock_bsearch_start(struct memblock_type *type,
  						  phys_addr_t base)
  {
  	int mid, low = 0;
  	int high = type->cnt;

  	if (type->cnt && base >= type->regions[type->cnt - 1].base +
  				 type->regions[type->cnt - 1].size)
  		return type->cnt;

  	while (low < high) {
  		mid = (low + high) / 2;
  		if (type->regions[mid].base + type->regions[mid].size <= base)
  			low = mid + 1;
  		else
  			high = mid;
  	}
  	return low;
  }
  ```
  Modified functions:
  - `memblock_add_range(struct memblock_type *type, phys_addr_t base, phys_addr_t size, int nid, enum memblock_flags flags)`: Uses `start_idx = memblock_bsearch_start(type, base);`
  - `memblock_isolate_range(struct memblock_type *type, phys_addr_t base, phys_addr_t size, int *start_rgn, int *end_rgn)`: Uses `start_idx = memblock_bsearch_start(type, base);`
  - `memblock_search(struct memblock_type *type, phys_addr_t addr)`:
    ```c
    static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)
    {
    	int idx = memblock_bsearch_start(type, addr);

    	if (idx < type->cnt && addr >= type->regions[idx].base)
    		return idx;
    	return -1;
    }
    ```

- **`mm/memory_hotplug.c`**:
  - `__add_memory_resource()`:
    ```c
    if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {
        if (res->flags & IORESOURCE_SYSRAM_DRIVER_MANAGED)
            memblock_flags = MEMBLOCK_DRIVER_MANAGED;
        ret = memblock_add_node(start, size, nid, memblock_flags);
        ...
    }
    ```
  - `try_remove_memory()`:
    ```c
    if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))
        memblock_remove(start, size);
    ```

- **`include/linux/memblock.h`**:
  - `memblock_add_node()`
  - `memblock_remove()`
  - `memblock_search_pfn_nid()`

### 4. Watchouts / Potential Reasoning Loops
- Do not conclude code is unreachable solely because memblock is an "early boot" allocator; `CONFIG_ARCH_KEEP_MEMBLOCK` keeps memblock structures active across runtime memory hotplug/hot-remove.
- Ensure focus symbols are limited to feature-specific non-ubiquitous symbols (`memblock_add_node`, `memblock_remove`, `memblock_add_range`, etc.), avoiding ubiquitous memory allocation functions like `kmalloc`, `page_alloc`, or generic allocators.
- Call `set-results` tool once before final response.

							input: 55531
							output: 2569
							thoughts: 0
						

gemini-3.8-flash

null

null

							input: 19692
							output: 35
							thoughts: 154
						

**Analyzing the Core of `memblock_search`**

Okay, so I need to understand the role of `memblock_search`. Right, let's break down where it's used. Based on these calls, `memblock_search` seems to be the fundamental function used to determine if a physical address falls within a reserved memory region. It underpins crucial checks like determining if a memory address is reserved (`memblock_is_reserved`), if it's considered regular memory (`memblock_is_memory` and `memblock_is_map_memory`), if a Page Frame Number (PFN) falls within a specific memory region for a particular Node ID (`memblock_search_pfn_nid`), and whether a range of addresses constitutes valid memory (`memblock_is_region_memory`). This is the workhorse.

To really grasp how it operates, I should dive into the code itself. I'll focus on lines 2090 to 2155 of `mm/memblock.c`. That should give me the core logic of the function, how it iterates through the memory block list, and how it determines if an address is "found" or not. I'll be looking for the search algorithm, the data structures it uses, and how it handles different scenarios. This is key to understanding how the memory allocator and memory management in general works at this level.

{
  "File": "mm/memblock.c",
  "FirstLine": 2090,
  "LineCount": 60
}

{
  "Contents": "2090:\t\tmemblock_cap_memory_range(0, max_addr);\n2091:\t}\n2092:\t\n2093:\tstatic int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)\n2094:\t{\n2095:\t\tint idx = memblock_bsearch_start(type, addr);\n2096:\t\n2097:\t\tif (idx \u003c type-\u003ecnt \u0026\u0026 addr \u003e= type-\u003eregions[idx].base)\n2098:\t\t\treturn idx;\n2099:\t\treturn -1;\n2100:\t}\n2101:\t\n2102:\tbool __init_memblock memblock_is_reserved(phys_addr_t addr)\n2103:\t{\n2104:\t\treturn memblock_search(\u0026memblock.reserved, addr) != -1;\n2105:\t}\n2106:\t\n2107:\tbool __init_memblock memblock_is_memory(phys_addr_t addr)\n2108:\t{\n2109:\t\treturn memblock_search(\u0026memblock.memory, addr) != -1;\n2110:\t}\n2111:\t\n2112:\tbool __init_memblock memblock_is_map_memory(phys_addr_t addr)\n2113:\t{\n2114:\t\tint i = memblock_search(\u0026memblock.memory, addr);\n2115:\t\n2116:\t\tif (i == -1)\n2117:\t\t\treturn false;\n2118:\t\treturn !memblock_is_nomap(\u0026memblock.memory.regions[i]);\n2119:\t}\n2120:\t\n2121:\tint __init_memblock memblock_search_pfn_nid(unsigned long pfn,\n2122:\t\t\t\t unsigned long *start_pfn, unsigned long *end_pfn)\n2123:\t{\n2124:\t\tstruct memblock_type *type = \u0026memblock.memory;\n2125:\t\tint mid = memblock_search(type, PFN_PHYS(pfn));\n2126:\t\n2127:\t\tif (mid == -1)\n2128:\t\t\treturn NUMA_NO_NODE;\n2129:\t\n2130:\t\t*start_pfn = PFN_DOWN(type-\u003eregions[mid].base);\n2131:\t\t*end_pfn = PFN_DOWN(type-\u003eregions[mid].base + type-\u003eregions[mid].size);\n2132:\t\n2133:\t\treturn memblock_get_region_node(\u0026type-\u003eregions[mid]);\n2134:\t}\n2135:\t\n2136:\t/**\n2137:\t * memblock_is_region_memory - check if a region is a subset of memory\n2138:\t * @base: base of region to check\n2139:\t * @size: size of region to check\n2140:\t *\n2141:\t * Check if the region [@base, @base + @size) is a subset of a memory block.\n2142:\t *\n2143:\t * Return:\n2144:\t * 0 if false, non-zero if true\n2145:\t */\n2146:\tbool __init_memblock memblock_is_region_memory(phys_addr_t base, phys_addr_t size)\n2147:\t{\n2148:\t\tint idx = memblock_search(\u0026memblock.memory, base);\n2149:\t\tphys_addr_t end = base + memblock_cap_size(base, \u0026size);\n"
}

gemini-3.8-flash

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							input: 21131
							output: 23
							thoughts: 20
						

Okay, let's dive into this. Here's how I'd approach this, thinking out loud as I unravel this bit of code:

**Finding the Callers of `memblock_search_pfn_nid`**

Right, so I need to understand the context of `memblock_search_pfn_nid`. My immediate thought is, "Okay, where is this function *actually* being used?" Knowing the call sites is key to understanding its purpose and impact. I need to track down all the places in the codebase where `memblock_search_pfn_nid` is called. That's the starting point. Time to fire up the search tools and trace those function calls. Let's get to work!

{
  "Expression": "memblock_search_pfn_nid"
}

{
  "Output": "include/linux/memblock.h=304=static inline bool memblock_is_kho_noprsrv(struct memblock_region *m)\n--\ninclude/linux/memblock.h-308-\ninclude/linux/memblock.h:309:int memblock_search_pfn_nid(unsigned long pfn, unsigned long *start_pfn,\ninclude/linux/memblock.h-310-\t\t\t    unsigned long  *end_pfn);\n--\nmm/memblock.c=2112=bool __init_memblock memblock_is_map_memory(phys_addr_t addr)\n--\nmm/memblock.c-2120-\nmm/memblock.c:2121:int __init_memblock memblock_search_pfn_nid(unsigned long pfn,\nmm/memblock.c-2122-\t\t\t unsigned long *start_pfn, unsigned long *end_pfn)\n--\nmm/mm_init.c=630=static int __meminit __early_pfn_to_nid(unsigned long pfn,\n--\nmm/mm_init.c-638-\nmm/mm_init.c:639:\tnid = memblock_search_pfn_nid(pfn, \u0026start_pfn, \u0026end_pfn);\nmm/mm_init.c-640-\tif (nid != NUMA_NO_NODE) {\n"
}

gemini-3.8-flash

null

null

							input: 21690
							output: 30
							thoughts: 54
						

Here's my take on the thought process, as requested:

**Digging into Memory Node Initialization**

Okay, let's dive into this memory management stuff. My immediate focus is on `mm/mm_init.c`. Specifically, I'm interested in how the system determines the NUMA node ID (`nid`) from a Page Frame Number (PFN) early in the boot process. The key function here seems to be `__early_pfn_to_nid`. I'll need to double check if there are other similar functions, such as `early_pfn_to_nid`, being used. Now, the next logical step is to track down all the call sites of either of these functions. I need to understand where and when this PFN-to-NID conversion is happening during the early initialization phase. That will give me a better picture of how the system is setting up the initial memory node assignments. This is a critical building block.

{
  "Expression": "early_pfn_to_nid",
  "PathPrefix": "mm/"
}

{
  "Output": "mm/hugetlb.c=3103=static bool __init alloc_bootmem_huge_page(struct hstate *h, int nid)\n--\nmm/hugetlb.c-3112-\tpfn = PHYS_PFN(__pa(m));\nmm/hugetlb.c:3113:\tnid = early_pfn_to_nid(pfn);\nmm/hugetlb.c-3114-\t/*\n--\nmm/memblock.c=2413=static void __init memmap_init_reserved_pages(void)\n--\nmm/memblock.c-2454-\t\t\tif (!numa_valid_node(nid))\nmm/memblock.c:2455:\t\t\t\tnid = early_pfn_to_nid(PFN_DOWN(start));\nmm/memblock.c-2456-\n--\nmm/mm_init.c=595=void __meminit __init_single_page(struct page *page, unsigned long pfn,\n--\nmm/mm_init.c-615- * During memory init memblocks map pfns to nids. The search is expensive and\nmm/mm_init.c:616: * this caches recent lookups. The implementation of __early_pfn_to_nid\nmm/mm_init.c-617- * treats start/end as pfns.\n--\nmm/mm_init.c=625=static struct mminit_pfnnid_cache early_pfnnid_cache __meminitdata;\n--\nmm/mm_init.c-629- */\nmm/mm_init.c:630:static int __meminit __early_pfn_to_nid(unsigned long pfn,\nmm/mm_init.c-631-\t\t\t\t\tstruct mminit_pfnnid_cache *state)\n--\nmm/mm_init.c-648-\nmm/mm_init.c:649:int __meminit early_pfn_to_nid(unsigned long pfn)\nmm/mm_init.c-650-{\n--\nmm/mm_init.c-654-\tspin_lock(\u0026early_pfn_lock);\nmm/mm_init.c:655:\tnid = __early_pfn_to_nid(pfn, \u0026early_pfnnid_cache);\nmm/mm_init.c-656-\tif (nid \u003c 0)\n--\nmm/mm_init.c=2409=void __init memblock_free_pages(unsigned long pfn, unsigned int order)\n--\nmm/mm_init.c-2413-\tif (IS_ENABLED(CONFIG_DEFERRED_STRUCT_PAGE_INIT)) {\nmm/mm_init.c:2414:\t\tint nid = early_pfn_to_nid(pfn);\nmm/mm_init.c-2415-\n--\nmm/numa.c=12=void __init alloc_node_data(int nid)\n--\nmm/numa.c-26-\t\tnd_pa, nd_pa + nd_size - 1);\nmm/numa.c:27:\ttnid = early_pfn_to_nid(nd_pa \u003e\u003e PAGE_SHIFT);\nmm/numa.c-28-\tif (tnid != nid)\n--\nmm/sparse-vmemmap.c=140=void __meminit vmemmap_verify(pte_t *pte, int node,\n--\nmm/sparse-vmemmap.c-143-\tunsigned long pfn = pte_pfn(ptep_get(pte));\nmm/sparse-vmemmap.c:144:\tint actual_node = early_pfn_to_nid(pfn);\nmm/sparse-vmemmap.c-145-\n"
}

gemini-3.8-flash

null

null

							input: 22921
							output: 27
							thoughts: 82
						

Okay, let's break this down.

**Investigating a Potential Memory Hotplug Issue**

Alright, so I'm digging into a memory management issue, likely related to hotplug. My initial thought is to zero in on `sparse-vmemmap.c` at line 140. Specifically, I'm following the trail from `vmemmap_verify` down to `early_pfn_to_nid`. The fact that `vmemmap_verify` is flagged as `__meminit` is immediately interesting – that screams early boot-time initialization, which makes it particularly relevant to how the virtual memory map is set up *before* standard memory hotplug operations. That's a good place to start my investigation.

My next step is to trace the calls to `vmemmap_verify` and `vmemmap_populate` to understand at what point they're invoked during the memory hotplug process. I need to understand the timing and context. Knowing when these functions are called during hotplug will tell me whether a bug in either function can contribute to the suspected problem.

{
  "Expression": "vmemmap_verify",
  "PathPrefix": "mm/"
}

{
  "Output": "mm/sparse-vmemmap.c=113=static void * __meminit altmap_alloc_block_buf(unsigned long size,\n--\nmm/sparse-vmemmap.c-139-\nmm/sparse-vmemmap.c:140:void __meminit vmemmap_verify(pte_t *pte, int node,\nmm/sparse-vmemmap.c-141-\t\t\t\tunsigned long start, unsigned long end)\n--\nmm/sparse-vmemmap.c=246=static pte_t * __meminit vmemmap_populate_address(unsigned long addr, int node,\n--\nmm/sparse-vmemmap.c-271-\t\treturn NULL;\nmm/sparse-vmemmap.c:272:\tvmemmap_verify(pte, node, addr, addr + PAGE_SIZE);\nmm/sparse-vmemmap.c-273-\n--\nmm/sparse-vmemmap.c=394=int __weak __meminit vmemmap_check_pmd(pmd_t *pmd, int node,\n--\nmm/sparse-vmemmap.c-398-\t\treturn 0;\nmm/sparse-vmemmap.c:399:\tvmemmap_verify((pte_t *)pmd, node, addr, next);\nmm/sparse-vmemmap.c-400-\n"
}

gemini-3.8-flash

null

null

							input: 23609
							output: 20
							thoughts: 190
						

**Deep Dive into Memory Management and the memblock Structure**

Okay, so I'm thinking about memory hotplug and what's happening under the hood when a new memory range gets introduced. The `vmemmap` gets populated, which triggers `vmemmap_verify`. That in turn calls `early_pfn_to_nid`, which then drills down into `__early_pfn_to_nid`. Ultimately, it seems like we're hitting `memblock_search_pfn_nid`, and this function is calling `memblock_search`. This goes down the rabbit hole to `memblock_bsearch_start`! That's quite a chain of function calls for a seemingly simple task.

And it's not just hotplug; `__add_memory_resource` is also using similar methods. It calls `memblock_add_node`, which then moves to `memblock_add_range`, and again, ends up at `memblock_bsearch_start`. This `memblock_bsearch_start` function must be doing a lot of heavy lifting.

What's really grabbing my attention is how interconnected the `memblock` operations appear to be. Even on the removal side, `try_remove_memory` is using this structure via `memblock_remove`, which heads to `memblock_remove_range`, and ultimately, `memblock_isolate_range`, and... you guessed it, `memblock_bsearch_start`! So, insertion, deletion, and verification all rely on the same fundamental building block.

Given how pervasive `memblock` is in these core memory operations, I'm now curious about how `ARCH_KEEP_MEMBLOCK` is defined across different architectures and the configurations that enable it. I need to understand the nuances of how this crucial structure is handled in various hardware environments.

{
  "Expression": "ARCH_KEEP_MEMBLOCK"
}

{
  "Output": "arch/arm/Kconfig=2=config ARM\n--\narch/arm/Kconfig-35-\tselect ARCH_HAS_GCOV_PROFILE_ALL\narch/arm/Kconfig:36:\tselect ARCH_KEEP_MEMBLOCK\narch/arm/Kconfig-37-\tselect ARCH_HAS_UBSAN\n--\narch/arm64/Kconfig=2=config ARM64\n--\narch/arm64/Kconfig-63-\tselect ARCH_HAVE_TRACE_MMIO_ACCESS\narch/arm64/Kconfig:64:\tselect ARCH_KEEP_MEMBLOCK\narch/arm64/Kconfig-65-\tselect ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE\n--\narch/loongarch/Kconfig=2=config LOONGARCH\n--\narch/loongarch/Kconfig-58-\tselect ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPTION\narch/loongarch/Kconfig:59:\tselect ARCH_KEEP_MEMBLOCK\narch/loongarch/Kconfig-60-\tselect ARCH_MIGHT_HAVE_PC_PARPORT\n--\narch/mips/Kconfig=2=config MIPS\n--\narch/mips/Kconfig-21-\tselect ARCH_HAS_GCOV_PROFILE_ALL\narch/mips/Kconfig:22:\tselect ARCH_KEEP_MEMBLOCK\narch/mips/Kconfig-23-\tselect ARCH_USE_BUILTIN_BSWAP\n--\narch/powerpc/Kconfig=118=config PPC\n--\narch/powerpc/Kconfig-163-\tselect ARCH_HAVE_EXTRA_ELF_NOTES        if SPU_BASE\narch/powerpc/Kconfig:164:\tselect ARCH_KEEP_MEMBLOCK\narch/powerpc/Kconfig-165-\tselect ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE\tif PPC_RADIX_MMU\n--\narch/riscv/Kconfig=13=config RISCV\n--\narch/riscv/Kconfig-60-\tselect ARCH_HAVE_NMI_SAFE_CMPXCHG\narch/riscv/Kconfig:61:\tselect ARCH_KEEP_MEMBLOCK if ACPI || KEXEC\narch/riscv/Kconfig-62-\tselect ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE\tif 64BIT \u0026\u0026 MMU\n--\narch/x86/Kconfig=1868=config INTEL_TDX_HOST\n--\narch/x86/Kconfig-1873-\tdepends on X86_X2APIC\narch/x86/Kconfig:1874:\tselect ARCH_KEEP_MEMBLOCK\narch/x86/Kconfig-1875-\tdepends on CONTIG_ALLOC\n--\ndrivers/firmware/efi/efi.c=1073=static int efi_mem_reserve_iomem(phys_addr_t addr, u64 size)\n--\ndrivers/firmware/efi/efi.c-1095-\t */\ndrivers/firmware/efi/efi.c:1096:\tif (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK) \u0026\u0026 !ret)\ndrivers/firmware/efi/efi.c-1097-\t\tmemblock_reserve(addr, size);\n--\ninclude/linux/memblock.h=114=extern struct memblock memblock;\ninclude/linux/memblock.h-115-\ninclude/linux/memblock.h:116:#ifndef CONFIG_ARCH_KEEP_MEMBLOCK\ninclude/linux/memblock.h-117-#define __init_memblock __meminit\n--\nkernel/kexec_file.c=580=static int locate_mem_hole_callback(struct resource *res, void *arg)\n--\nkernel/kexec_file.c-606-\nkernel/kexec_file.c:607:#ifdef CONFIG_ARCH_KEEP_MEMBLOCK\nkernel/kexec_file.c-608-static int kexec_walk_memblock(struct kexec_buf *kbuf,\n--\nkernel/kexec_file.c=736=int kexec_locate_mem_hole(struct kexec_buf *kbuf)\n--\nkernel/kexec_file.c-758-\nkernel/kexec_file.c:759:\tif (!IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))\nkernel/kexec_file.c-760-\t\tret = kexec_walk_resources(kbuf, locate_mem_hole_callback);\n--\nmm/Kconfig=482=config HAVE_GUP_FAST\n--\nmm/Kconfig-488-# Also, memblocks are updated with memory hot(un)plug.\nmm/Kconfig:489:config ARCH_KEEP_MEMBLOCK\nmm/Kconfig-490-\tbool\n--\nmm/memblock.c-100- *\nmm/memblock.c:101: * Unless an architecture enables %CONFIG_ARCH_KEEP_MEMBLOCK, the\nmm/memblock.c-102- * memblock data structures (except \"physmem\") will be discarded after the\n--\nmm/memblock.c=359=static void __init_memblock memblock_remove_region(struct memblock_type *type, unsigned long r)\n--\nmm/memblock.c-375-\nmm/memblock.c:376:#ifndef CONFIG_ARCH_KEEP_MEMBLOCK\nmm/memblock.c-377-/**\n--\nmm/memblock.c=957=unsigned long free_reserved_area(void *start, void *end, int poison, const char *s)\n--\nmm/memblock.c-975-\nmm/memblock.c:976:\tif (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {\nmm/memblock.c-977-\t\tif (start_pa \u003c end_pa)\n--\nmm/memblock.c=1013=int __init_memblock memblock_phys_free(phys_addr_t base, phys_addr_t size)\n--\nmm/memblock.c-1022-\nmm/memblock.c:1023:\tif (!slab_is_available() || IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))\nmm/memblock.c-1024-\t\tret = memblock_remove_range(\u0026memblock.reserved, base, size);\n--\nmm/memblock.c=2893=__setup(\"reserve_mem=\", reserve_mem);\n--\nmm/memblock.c-2895-#ifdef CONFIG_DEBUG_FS\nmm/memblock.c:2896:#ifdef CONFIG_ARCH_KEEP_MEMBLOCK\nmm/memblock.c-2897-static const char * const flagname[] = {\n--\nmm/memblock.c=2957=static inline void memblock_debugfs_expose_arrays(struct dentry *root) { }\nmm/memblock.c-2958-\nmm/memblock.c:2959:#endif /* CONFIG_ARCH_KEEP_MEMBLOCK */\nmm/memblock.c-2960-\n--\nmm/memblock.c=2981=static int __init memblock_init_debugfs(void)\n--\nmm/memblock.c-2984-\nmm/memblock.c:2985:\tif (!IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK) \u0026\u0026 !reserved_mem_count)\nmm/memblock.c-2986-\t\treturn 0;\n--\nmm/memory_hotplug.c=1500=static int __add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags,\n--\nmm/memory_hotplug.c-1530-\nmm/memory_hotplug.c:1531:\tif (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {\nmm/memory_hotplug.c-1532-\t\tif (res-\u003eflags \u0026 IORESOURCE_SYSRAM_DRIVER_MANAGED)\n--\nmm/memory_hotplug.c-1601-error_memblock_remove:\nmm/memory_hotplug.c:1602:\tif (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))\nmm/memory_hotplug.c-1603-\t\tmemblock_remove(start, size);\n--\nmm/memory_hotplug.c=2291=static int try_remove_memory(u64 start, u64 size)\n--\nmm/memory_hotplug.c-2331-\nmm/memory_hotplug.c:2332:\tif (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))\nmm/memory_hotplug.c-2333-\t\tmemblock_remove(start, size);\n"
}

gemini-3.8-flash

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null

							input: 26387
							output: 18
							thoughts: 221
						

**Investigating Memory Block Initialization**

Okay, so I'm looking at this code and something jumps out at me. Even without `CONFIG_ARCH_KEEP_MEMBLOCK` defined, I need to understand what `__init_memblock` is doing here. Diving into `include/linux/memblock.h`, I see that it's defined as `__meminit` if `CONFIG_ARCH_KEEP_MEMBLOCK` isn't set. Alright, what's `__meminit`?

Checking `include/linux/init.h`, the picture starts to clarify. If `CONFIG_MEMORY_HOTPLUG` is *enabled*, `__meminit` effectively does *nothing*! It's not discarded, it's kept. But if it's disabled, then `__meminit` maps to `__init`, which *is* discarded, right?

But that's interesting because if `CONFIG_MEMORY_HOTPLUG` *is* enabled, then the memory isn't actually discarded by `__meminit`! I remember that `memblock_free_all()` is the function used to discard memory, and `memblock_discard` is another related function, so if `memblock_free_all` discards memory if `!CONFIG_ARCH_KEEP_MEMBLOCK`, then `__meminit` and `__meminitdata` must be handled with a different mechanism! I need to dig into `memblock_free_all` and `memblock_discard` to trace the whole memory block lifecycle. Let's see...

{
  "Expression": "memblock_discard"
}

{
  "Output": "include/linux/memblock.h=114=extern struct memblock memblock;\n--\ninclude/linux/memblock.h-118-#define __initdata_memblock __meminitdata\ninclude/linux/memblock.h:119:void memblock_discard(void);\ninclude/linux/memblock.h-120-#else\n--\ninclude/linux/memblock.h-122-#define __initdata_memblock\ninclude/linux/memblock.h:123:static inline void memblock_discard(void) {}\ninclude/linux/memblock.h-124-#endif\n--\nmm/kmsan/init.c=101=static struct metadata_page_pair held_back[NR_PAGE_ORDERS] __initdata;\n--\nmm/kmsan/init.c-113- * At the very end there may be leftover blocks in held_back[]. They are\nmm/kmsan/init.c:114: * collected later by kmsan_memblock_discard().\nmm/kmsan/init.c-115- */\n--\nmm/kmsan/init.c=181=static void collect_split(void)\n--\nmm/kmsan/init.c-202- */\nmm/kmsan/init.c:203:static void kmsan_memblock_discard(void)\nmm/kmsan/init.c-204-{\n--\nmm/kmsan/init.c=229=void __init kmsan_init_runtime(void)\n--\nmm/kmsan/init.c-232-\tkmsan_internal_task_create(current);\nmm/kmsan/init.c:233:\tkmsan_memblock_discard();\nmm/kmsan/init.c-234-\tpr_info(\"Starting KernelMemorySanitizer\\n\");\n--\nmm/memblock.c=143=struct memblock_type physmem = {\n--\nmm/memblock.c-153- *  For architectures that do not keep memblock data after init, this\nmm/memblock.c:154: * pointer will be reset to NULL at memblock_discard()\nmm/memblock.c-155- */\n--\nmm/memblock.c=359=static void __init_memblock memblock_remove_region(struct memblock_type *type, unsigned long r)\n--\nmm/memblock.c-377-/**\nmm/memblock.c:378: * memblock_discard - discard memory and reserved arrays if they were allocated\nmm/memblock.c-379- */\nmm/memblock.c:380:void __init memblock_discard(void)\nmm/memblock.c-381-{\n--\nmm/mm_init.c=2239=void __init page_alloc_init_late(void)\n--\nmm/mm_init.c-2270-\t/* Discard memblock private memory */\nmm/mm_init.c:2271:\tmemblock_discard();\nmm/mm_init.c-2272-\n"
}

gemini-3.8-flash

null

null

							input: 27728
							output: 40
							thoughts: 2002
						

**Fuzzing Recommendation: Memory Block Management (memblock)**

Okay, let's break this down. My goal is to determine if this patch warrants fuzzing. On an x86_64 system, specifically a system that could potentially enable Intel Trust Domain Extensions (`CONFIG_INTEL_TDX_HOST`), it seems `ARCH_KEEP_MEMBLOCK` gets enabled. That's key. I need to understand the implications of this.

Looking at the code, when `ARCH_KEEP_MEMBLOCK` is active, functions like `memblock_add_node`, `memblock_remove`, `memblock_phys_free`, and even things tied to EFI memory reservations use `memblock_add_node`, and similar related functions. Also, functions like `vmemmap_verify` use things like  `memblock_search`. Debugging is even exposed via debugfs.

The critical part is memory hotplug. This is reachable through things like virtio-mem or writing to the memory probe sysfs, or DAX kmem. This means there's a practical way to trigger this code in a standard environment like QEMU. Can I use TDX in QEMU? Yes, because it's a standard x86_64 host kernel config; it depends on the necessary CPU features.

Now, does this qualify as `WorthFuzzing`? Absolutely. This touches core memory management and algorithmic flows. This patch alters the core `memblock` subsystem code, specifically how it searches, adds, and isolates memory regions, and rewrites the search. Since the modified functions are executed dynamically, and I can trigger this code using virtio-mem, or the memory probe, it meets the criteria for fuzzing. Any bugs could lead to memory corruption, wrong NUMA node assignment, or infinite loops.

Now, for focus symbols. I need to identify the *specific* functions to target. The modified functions are `memblock_bsearch_start`, `memblock_add_range`, `memblock_isolate_range`, `memblock_search`, and `memblock_dump`. These are all static. Let's make sure that these are visible as symbols - and they are, unless the compiler inlines them.

Also, I should look at the non-static callers too: `memblock_add_node`, `memblock_add`, `memblock_remove`, `memblock_remove_range`, `memblock_search_pfn_nid`, `memblock_is_memory`, and `memblock_is_reserved`. These aren't ubiquitous functions like memory allocators and deallocators. They're specific to memblock operations. These should definitely be the FocusSymbols. So, by adding these as focus symbols, I'm setting the fuzzer to focus on the specific logic that's being changed. I will inspect the code of `memblock_add_node` and `memblock_remove` to ensure I'm getting the precise caller functions.

{
  "Expression": "int __init_memblock memblock_add_node\\b",
  "PathPrefix": "mm/memblock.c"
}

{
  "Output": "mm/memblock.c=632=static int __init_memblock memblock_add_range(struct memblock_type *type,\n--\nmm/memblock.c-751- */\nmm/memblock.c:752:int __init_memblock memblock_add_node(phys_addr_t base, phys_addr_t size,\nmm/memblock.c-753-\t\t\t\t      int nid, enum memblock_flags flags)\n"
}

gemini-3.8-flash

null

null

							input: 30532
							output: 38
							thoughts: 19
						

Here's a summary of my thought process, as requested:

**Diving into Memory Block Removal**

Alright, let's get down to brass tacks. I need to take a closer look at `memblock_remove` and its counterpart, `memblock_remove_range`. I know how critical memory management is, especially at the kernel level. These functions are absolutely central to reclaiming and freeing memory regions within the memblock structure. I need to understand their exact behavior, error handling, and performance characteristics in detail. I'm thinking about things like: What are the edge cases? How do they handle overlapping regions? Are there any potential race conditions I need to be aware of? Are there areas where performance could be optimized with some novel approaches? It's time to dive into the code and see how these crucial functions truly tick.

{
  "Expression": "int __init_memblock memblock_remove\\b",
  "PathPrefix": "mm/memblock.c"
}

{
  "Output": "mm/memblock.c=897=static int __init_memblock memblock_remove_range(struct memblock_type *type,\n--\nmm/memblock.c-911-\nmm/memblock.c:912:int __init_memblock memblock_remove(phys_addr_t base, phys_addr_t size)\nmm/memblock.c-913-{\n"
}

gemini-3.8-flash

null

null

							input: 30873
							output: 36
							thoughts: 441
						

**Analyzing Memory Block Management Functions and Configuration Dependencies**

Okay, let's dive in. My immediate focus is on several key memory block management functions within the kernel. I need to refresh my understanding of how they work, so I'm going to quickly review their definitions. First, I'm checking `memblock_bsearch_start`, then `memblock_add_range`, then `memblock_isolate_range`, then `memblock_search`, followed by `memblock_search_pfn_nid`, then `memblock_add_node`, and lastly, `memblock_remove`. Understanding the mechanics of these functions is crucial for any deeper dive.

Now, I need to understand the configuration space related to memory block management, particularly on amd64. I'm going to look at what configurations are necessary to enable `ARCH_KEEP_MEMBLOCK` and memory hotplug, and how they interact. Specifically, I'm going to check `arch/x86/Kconfig` for `INTEL_TDX_HOST`.

{
  "Expression": "config INTEL_TDX_HOST",
  "PathPrefix": "arch/x86/Kconfig"
}

{
  "Output": "arch/x86/Kconfig=1848=config X86_USER_SHADOW_STACK\n--\narch/x86/Kconfig-1867-\narch/x86/Kconfig:1868:config INTEL_TDX_HOST\narch/x86/Kconfig-1869-\tbool \"Intel Trust Domain Extensions (TDX) host support\"\n"
}

gemini-3.8-flash

null

null

							input: 31679
							output: 37
							thoughts: 22
						

Okay, here's my interpretation of what's going on, formatted as you requested:

**Navigating the Kconfig Labyrinth**

Alright, let's dive in. The task is to examine `arch/x86/Kconfig` starting around line 1868. This likely means we're looking at a specific configuration option or a related block of options. Given the location in `arch/x86`, I'm expecting this section to deal with processor-specific features, maybe something related to CPU models, specific instruction set extensions, or potentially a driver configuration for a particular hardware element. It's also possible we are looking at dependencies of other more specific configurations. The fact that the line is identified is crucial, because this is the entry point, it means that someone has identified this section as relevant to some investigation, likely about a specific configuration option or issue. I'll need to use my existing knowledge of the kernel's x86 configuration system to interpret the context correctly. I'm going to start by getting a broad view, and quickly looking for any clue of dependencies and potential relationships with other parts of the x86 configuration. From here, I'll need to be quick to spot the key information and to synthesize the available information into something that is useful to me and to my objectives.

{
  "File": "arch/x86/Kconfig",
  "FirstLine": 1865,
  "LineCount": 25
}

{
  "Contents": "1865:\t\n1866:\t\t  If unsure, say N.\n1867:\t\n1868:\tconfig INTEL_TDX_HOST\n1869:\t\tbool \"Intel Trust Domain Extensions (TDX) host support\"\n1870:\t\tdepends on CPU_SUP_INTEL\n1871:\t\tdepends on X86_64\n1872:\t\tdepends on KVM_INTEL\n1873:\t\tdepends on X86_X2APIC\n1874:\t\tselect ARCH_KEEP_MEMBLOCK\n1875:\t\tdepends on CONTIG_ALLOC\n1876:\t\tdepends on X86_MCE\n1877:\t\thelp\n1878:\t\t  Intel Trust Domain Extensions (TDX) protects guest VMs from malicious\n1879:\t\t  host and certain physical attacks.  This option enables necessary TDX\n1880:\t\t  support in the host kernel to run confidential VMs.\n1881:\t\n1882:\t\t  If unsure, say N.\n1883:\t\n1884:\tconfig EFI\n1885:\t\tbool \"EFI runtime service support\"\n1886:\t\tdepends on ACPI\n1887:\t\tselect UCS2_STRING\n1888:\t\tselect EFI_RUNTIME_WRAPPERS\n1889:\t\tselect ARCH_USE_MEMREMAP_PROT\n"
}

gemini-3.8-flash

null

null

							input: 32369
							output: 33
							thoughts: 91
						

Okay, here's my summary, tailored for an expert audience, in the first person:

**My Deductions on Intel TDX Host Configuration**

Alright, let's break this down. My initial assessment is that `CONFIG_INTEL_TDX_HOST` hinges on several prerequisites. I see it depends on `CPU_SUP_INTEL`, `X86_64`, `KVM_INTEL`, `X86_X2APIC`, `CONTIG_ALLOC`, and `X86_MCE`. That makes perfect sense. Given the nature of TDX, each of those dependencies logically plays a critical role in providing the foundational hardware and virtualization support needed.

Now, a question is tickling the back of my mind: what about `MEMORY_HOTPLUG`? TDX is about memory isolation, and hotplugging impacts memory management, so it's a valid concern. I should really check the memory management configuration to see how that interacts.

I will delve into `mm/Kconfig` to confirm whether or not `MEMORY_HOTPLUG` is included. I need to understand its relationship to TDX support.

{
  "Expression": "config MEMORY_HOTPLUG\\b",
  "PathPrefix": "mm/Kconfig"
}

{
  "Output": "mm/Kconfig=506=config ARCH_ENABLE_MEMORY_HOTPLUG\n--\nmm/Kconfig-509-# eventually, we can have this option just 'select SPARSEMEM'\nmm/Kconfig:510:menuconfig MEMORY_HOTPLUG\nmm/Kconfig-511-\tbool \"Memory hotplug\"\n"
}

gemini-3.8-flash

null

null

							input: 32831
							output: 32
							thoughts: 17
						

Okay, here's my interpretation of what's going through my mind as I approach this `mm/Kconfig` file and line 510, tailored for an expert audience:

**Diving into mm/Kconfig - Line 510**

Alright, let's get down to it. Time to dig into `mm/Kconfig`, specifically around line 510. My initial thought process is geared up: I need to quickly grasp what's being configured there. Knowing the Kconfig format, I'm expecting to see a configuration option, or perhaps a series of options, related to memory management. Given the file and context, it's almost certainly dealing with features, settings, or parameters that influence how the kernel handles memory allocation, paging, or related subsystems. My expert intuition is immediately activated, anticipating the underlying kernel features being governed. My mind is already running through possible options: is this about NUMA, page sizes, slab allocation, virtual memory limitations, or something more specialized? The fact it's Kconfig implies compile-time configuration, meaning there's some critical decision about how this kernel image will behave regarding memory, and I need to parse the specifics quickly to grasp the functionality or feature involved. This is going to be interesting.

{
  "File": "mm/Kconfig",
  "FirstLine": 510,
  "LineCount": 40
}

{
  "Contents": " 510:\tmenuconfig MEMORY_HOTPLUG\n 511:\t\tbool \"Memory hotplug\"\n 512:\t\tselect MEMORY_ISOLATION\n 513:\t\tdepends on SPARSEMEM_VMEMMAP\n 514:\t\tdepends on ARCH_ENABLE_MEMORY_HOTPLUG\n 515:\t\tdepends on 64BIT\n 516:\t\tselect NUMA_KEEP_MEMINFO if NUMA\n 517:\t\n 518:\tif MEMORY_HOTPLUG\n 519:\t\n 520:\tchoice\n 521:\t\tprompt \"Memory Hotplug Default Online Type\"\n 522:\t\tdefault MHP_DEFAULT_ONLINE_TYPE_OFFLINE\n 523:\t\thelp\n 524:\t\t  Default memory type for hotplugged memory.\n 525:\t\n 526:\t\t  This option sets the default policy setting for memory hotplug\n 527:\t\t  onlining policy (/sys/devices/system/memory/auto_online_blocks) which\n 528:\t\t  determines what happens to newly added memory regions. Policy setting\n 529:\t\t  can always be changed at runtime.\n 530:\t\n 531:\t\t  The default is 'offline'.\n 532:\t\n 533:\t\t  Select offline to defer onlining to drivers and user policy.\n 534:\t\t  Select auto to let the kernel choose what zones to utilize.\n 535:\t\t  Select online_kernel to generally allow kernel usage of this memory.\n 536:\t\t  Select online_movable to generally disallow kernel usage of this memory.\n 537:\t\n 538:\t\t  Example kernel usage would be page structs and page tables.\n 539:\t\n 540:\t\t  See Documentation/admin-guide/mm/memory-hotplug.rst for more information.\n 541:\t\n 542:\tconfig MHP_DEFAULT_ONLINE_TYPE_OFFLINE\n 543:\t\tbool \"offline\"\n 544:\t\thelp\n 545:\t\t  Hotplugged memory will not be onlined by default.\n 546:\t\t  Choose this for systems with drivers and user policy that\n 547:\t\t  handle onlining of hotplug memory policy.\n 548:\t\n 549:\tconfig MHP_DEFAULT_ONLINE_TYPE_ONLINE_AUTO\n"
}

gemini-3.8-flash

null

null

							input: 33748
							output: 32
							thoughts: 14
						

Okay, let's dive into this. Here's my take on those thoughts, as if they're my own:

**Delving into MEMORY_HOTPLUG**

Right, let's get back to this. I've been focusing on various aspects, but now it's time to circle back to what else we have under `MEMORY_HOTPLUG`. I need a more comprehensive understanding of the surrounding landscape to make a sound decision. We can't make informed decisions with incomplete data. Time to explore. I need to know the next logical steps to take.

{
  "File": "mm/Kconfig",
  "FirstLine": 550,
  "LineCount": 40
}

{
  "Contents": " 550:\t\tbool \"auto\"\n 551:\t\thelp\n 552:\t\t  Select this if you want the kernel to automatically online\n 553:\t\t  hotplugged memory into the zone it thinks is reasonable.\n 554:\t\t  This memory may be utilized for kernel data.\n 555:\t\n 556:\tconfig MHP_DEFAULT_ONLINE_TYPE_ONLINE_KERNEL\n 557:\t\tbool \"kernel\"\n 558:\t\thelp\n 559:\t\t  Select this if you want the kernel to automatically online\n 560:\t\t  hotplugged memory into a zone capable of being used for kernel\n 561:\t\t  data. This typically means ZONE_NORMAL.\n 562:\t\n 563:\tconfig MHP_DEFAULT_ONLINE_TYPE_ONLINE_MOVABLE\n 564:\t\tbool \"movable\"\n 565:\t\thelp\n 566:\t\t  Select this if you want the kernel to automatically online\n 567:\t\t  hotplug memory into ZONE_MOVABLE. This memory will generally\n 568:\t\t  not be utilized for kernel data.\n 569:\t\n 570:\t\t  This should only be used when the admin knows sufficient\n 571:\t\t  ZONE_NORMAL memory is available to describe hotplug memory,\n 572:\t\t  otherwise hotplug memory may fail to online. For example,\n 573:\t\t  sufficient kernel-capable memory (ZONE_NORMAL) must be\n 574:\t\t  available to allocate page structs to describe ZONE_MOVABLE.\n 575:\t\n 576:\tendchoice\n 577:\t\n 578:\tconfig MEMORY_HOTREMOVE\n 579:\t\tbool \"Allow for memory hot remove\"\n 580:\t\tselect MIGRATION\n 581:\t\n 582:\tconfig MHP_MEMMAP_ON_MEMORY\n 583:\t\tdef_bool y\n 584:\t\tdepends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE\n 585:\t\n 586:\tendif # MEMORY_HOTPLUG\n 587:\t\n 588:\tconfig ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE\n 589:\t       bool\n"
}

gemini-3.8-flash

null

null

							input: 34491
							output: 21
							thoughts: 12
						

Okay, here's my take on those thoughts, tailored for an expert audience and presented in the first person:

**Deep Dive on `ARCH_MEMORY_PROBE`**

Right, let's get down to brass tacks. My initial thought? Let's immediately zero in on `ARCH_MEMORY_PROBE`. It's the lynchpin, isn't it? The starting point. What can this tell us, and where do we need to look in the code to get a handle on it? Depending on the architecture, it could be anything from a simple flag check to an elaborate memory map examination. I need to understand its intent and implications within the context of the larger system. Is it for general memory availability? Specific region protection? Perhaps it’s a probe to determine if the system has some specific hardware feature to support larger memory. The details are important. Let’s figure out what this probe is doing with respect to how it works on different architectures.

{
  "Expression": "config ARCH_MEMORY_PROBE"
}

{
  "Output": "arch/loongarch/Kconfig=776=config ARCH_SPARSEMEM_ENABLE\n--\narch/loongarch/Kconfig-784-\narch/loongarch/Kconfig:785:config ARCH_MEMORY_PROBE\narch/loongarch/Kconfig-786-\tdef_bool y\n--\narch/powerpc/Kconfig=806=config ILLEGAL_POINTER_VALUE\n--\narch/powerpc/Kconfig-812-\narch/powerpc/Kconfig:813:config ARCH_MEMORY_PROBE\narch/powerpc/Kconfig-814-\tdef_bool y\n--\narch/x86/Kconfig=1569=config ARCH_SELECT_MEMORY_MODEL\n--\narch/x86/Kconfig-1572-\narch/x86/Kconfig:1573:config ARCH_MEMORY_PROBE\narch/x86/Kconfig-1574-\tbool \"Enable sysfs memory/probe interface\"\n"
}

gemini-3.8-flash

null

null

							input: 34986
							output: 37
							thoughts: 19
						

Okay, here's my take on those thoughts, tailored for an expert audience and presented in the first person:

**Diving into the x86 Kernel Configuration**

Alright, time to get to it. My immediate thought is to zero in on `arch/x86/Kconfig:1573`. That line number's practically etched in my memory given what I'm working on right now, which likely means I have some very specific context I'm hoping to refresh or clarify. It probably involves a particular feature, driver, or architectural setting within the x86 kernel configuration space. I'm likely chasing down a dependency, exploring a potential conflict, or verifying the state of a crucial option before making a modification. The line number is my key. No guesswork. Let's see what we find there. It's time to dive into that specific nugget of configuration data and understand the nuance of the situation.

{
  "File": "arch/x86/Kconfig",
  "FirstLine": 1570,
  "LineCount": 15
}

{
  "Contents": "1570:\t\tdef_bool y\n1571:\t\tdepends on ARCH_SPARSEMEM_ENABLE \u0026\u0026 ARCH_FLATMEM_ENABLE\n1572:\t\n1573:\tconfig ARCH_MEMORY_PROBE\n1574:\t\tbool \"Enable sysfs memory/probe interface\"\n1575:\t\tdepends on MEMORY_HOTPLUG\n1576:\t\thelp\n1577:\t\t  This option enables a sysfs memory/probe interface for testing.\n1578:\t\t  See Documentation/admin-guide/mm/memory-hotplug.rst for more information.\n1579:\t\t  If you are unsure how to answer this question, answer N.\n1580:\t\n1581:\tconfig ARCH_PROC_KCORE_TEXT\n1582:\t\tdef_bool y\n1583:\t\tdepends on X86_64 \u0026\u0026 PROC_KCORE\n1584:\t\n"
}

gemini-3.8-flash

null

null

							input: 35476
							output: 20
							thoughts: 214
						

Here's my analysis of the provided information:

**Memory Management Deep Dive**

Okay, so I'm looking at this code and immediately my attention is drawn to `ARCH_MEMORY_PROBE`. It's a key feature, allowing for dynamic probing of physical memory ranges through the `/sys/devices/system/memory/probe` interface, but crucially it relies on `MEMORY_HOTPLUG`. I see now that when this probe feature is enabled, userspace applications, perhaps even something like syzkaller, can trigger the `add_memory` function. This, in turn, cascades down to `__add_memory_resource`, then through `memblock_add_node`, and ultimately boils down to `memblock_add_range` and, of course, the ever-useful `memblock_bsearch_start` for insertion. Clearly this is a critical path for managing newly added memory.

On the hot-removal side, `MEMORY_HOTREMOVE` enables the un-plugging of memory, either through the sysfs interface (specifically the `state` store) or via a driver. This process is initiated through `try_remove_memory`, which then leads to `memblock_remove`, followed by `memblock_remove_range`. Then we have the isolation of a range using `memblock_isolate_range`, and ultimately, again, the use of `memblock_bsearch_start` to locate the ranges we need to act upon. That `bsearch_start` function seems critical for maintaining the memory map's integrity.

Finally, I need to check out `VIRTIO_MEM`. It's time to check the `drivers/virtio/Kconfig` file to see how it's integrated and what dependencies it has.

{
  "Expression": "config VIRTIO_MEM"
}

{
  "Output": "drivers/virtio/Kconfig=112=config VIRTIO_BALLOON\n--\ndrivers/virtio/Kconfig-122-\ndrivers/virtio/Kconfig:123:config VIRTIO_MEM\ndrivers/virtio/Kconfig-124-\ttristate \"Virtio mem driver\"\n"
}

gemini-3.8-flash

null

null

							input: 36173
							output: 35
							thoughts: 17
						

Okay, here's my interpretation of that request, formatted as requested:

**Digging into the Virtio Driver Configuration**

Alright, let's get down to brass tacks. I need to understand how this virtio driver is configured. The starting point is always the Kconfig file, so I'm heading straight to `drivers/virtio/Kconfig`, specifically line 123. This is where the magic happens. I expect to find the core definitions for the driver's build options – things like whether it's modular, configurable features, dependencies, and any default settings. Line 123 should be key to unraveling the build-time behavior of this virtio implementation. Now, let's see what gems are contained there.

{
  "File": "drivers/virtio/Kconfig",
  "FirstLine": 123,
  "LineCount": 20
}

{
  "Contents": " 123:\tconfig VIRTIO_MEM\n 124:\t\ttristate \"Virtio mem driver\"\n 125:\t\tdepends on X86_64 || ARM64 || RISCV || S390\n 126:\t\tdepends on VIRTIO\n 127:\t\tdepends on MEMORY_HOTPLUG\n 128:\t\tdepends on MEMORY_HOTREMOVE\n 129:\t\tdepends on CONTIG_ALLOC\n 130:\t\tdepends on EXCLUSIVE_SYSTEM_RAM\n 131:\t\thelp\n 132:\t\t This driver provides access to virtio-mem paravirtualized memory\n 133:\t\t devices, allowing to hotplug and hotunplug memory.\n 134:\t\n 135:\t\t This driver currently supports x86-64, arm64, riscv and s390.\n 136:\t\t Although it should compile on other architectures that implement\n 137:\t\t memory hot(un)plug, architecture-specific and/or common\n 138:\t\t code changes may be required for virtio-mem, kdump and kexec to\n 139:\t\t work as expected.\n 140:\t\n 141:\t\t If unsure, say M.\n 142:\t\n"
}

gemini-3.8-flash

null

null

							input: 36706
							output: 306
							thoughts: 2278
						

**Analysis of Memory Block Management in Kernel Patch**

Okay, let's break this down. My initial thought is to ensure the patch's changes are contextually sound, so I start by reviewing the related configurations that would activate the changed code path, specifically on amd64. I quickly identify the necessary configurations like `INTEL_TDX_HOST`, `MEMORY_HOTPLUG`, and others related to memory hot-add/remove functionalities. This confirms that these functions, and therefore the patch, are not just theoretical, but can be reached under certain build configurations and use cases.

Next, I look at the heart of the code change, the specific functions within `mm/memblock.c` that are altered: `memblock_bsearch_start`, `memblock_add_range`, `memblock_isolate_range`, and so on. These are key because they are the new implementation of iteration and region search. I recognize that these functions are not involved in ubiquitous system routines, but deal directly with memory block operations during the system lifecycle, particularly when memory is added or removed. This makes them good candidates for in-depth analysis.

I then proceed to conduct a sanity check, verifying that the intended fuzzing configuration is appropriate. The reasoning is clear: the patch's modifications, especially in the core search and iteration logic, introduce new opportunities for boundary conditions and potential region corruption, specifically when running with dynamic memory management. By selecting specific symbols and enabling the identified configurations, we're targeting a test scenario that makes the changes practically relevant. This will set the right parameters. This confirms the validity of the "set-results" configuration and its associated fuzzing effort.

{
  "EnableConfigs": [
    "INTEL_TDX_HOST",
    "MEMORY_HOTPLUG",
    "MEMORY_HOTREMOVE",
    "ARCH_MEMORY_PROBE",
    "VIRTIO_MEM"
  ],
  "FocusSymbols": [
    "memblock_bsearch_start",
    "memblock_add_range",
    "memblock_isolate_range",
    "memblock_search",
    "memblock_add_node",
    "memblock_remove",
    "memblock_search_pfn_nid"
  ],
  "Reasoning": "The patch introduces memblock_bsearch_start() and refactors region search and iteration loops in mm/memblock.c (memblock_add_range, memblock_isolate_range, memblock_search). While memblock is primarily used during boot, on amd64 CONFIG_INTEL_TDX_HOST selects CONFIG_ARCH_KEEP_MEMBLOCK, preventing discard of memblock data and code at runtime. When combined with CONFIG_MEMORY_HOTPLUG (reachable via virtio-mem or sysfs memory probe), memblock_add_node(), memblock_remove(), and memblock_search_pfn_nid() are actively invoked during runtime memory hotplug/hot-remove operations. Fuzzing is warranted to test the binary search boundaries and region isolation/addition logic for potential corruption or regression.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "INTEL_TDX_HOST",
    "MEMORY_HOTPLUG",
    "MEMORY_HOTREMOVE",
    "ARCH_MEMORY_PROBE",
    "VIRTIO_MEM"
  ],
  "FocusSymbols": [
    "memblock_bsearch_start",
    "memblock_add_range",
    "memblock_isolate_range",
    "memblock_search",
    "memblock_add_node",
    "memblock_remove",
    "memblock_search_pfn_nid"
  ],
  "Reasoning": "The patch introduces memblock_bsearch_start() and refactors region search and iteration loops in mm/memblock.c (memblock_add_range, memblock_isolate_range, memblock_search). While memblock is primarily used during boot, on amd64 CONFIG_INTEL_TDX_HOST selects CONFIG_ARCH_KEEP_MEMBLOCK, preventing discard of memblock data and code at runtime. When combined with CONFIG_MEMORY_HOTPLUG (reachable via virtio-mem or sysfs memory probe), memblock_add_node(), memblock_remove(), and memblock_search_pfn_nid() are actively invoked during runtime memory hotplug/hot-remove operations. Fuzzing is warranted to test the binary search boundaries and region isolation/addition logic for potential corruption or regression.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

core

null

{
  "KMSANReasoning": "The patch optimizes memblock region lookups (in memblock_add_range, memblock_isolate_range, and memblock_search) by implementing a binary search helper memblock_bsearch_start() to locate candidate region indices instead of performing linear scans from index 0.\n\nNone of the changes touch kernel-to-user copy paths (no copy_to_user, netlink, ioctl, etc.), nor do they allocate or manipulate data structures with uninitialized fields or padding. All local variables (start_idx, low, high, mid) are fully initialized before use. Any potential bugs in this patch would be algorithmic or bounds-related (e.g., off-by-one errors or out-of-bounds indexing in the memblock region array), which are detected by KASAN, assertions, or functional tests. Because no uninitialized memory reads or information leaks are introduced or exposed, a dedicated KMSAN fuzzing session is not justified.",
  "NeedsKMSAN": false
}

You are an expert Linux kernel security engineer specializing in kernel memory
error detectors (KASAN and KMSAN). Your job is to review the provided patch series and
determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer)
fuzzing session in addition to standard KASAN fuzzing.

CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN:
- Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable
  a comprehensive suite of debugging tools and sanitizers, including KASAN
  (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP
  (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks.
- KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap,
  or page allocations) and kernel-to-user memory info-leaks.

Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN,
LOCKDEP, OR OTHER STANDARD BUG DETECTORS.
A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY
set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks
that are detected ONLY by KMSAN.

Look holistically at the patch series and surrounding code. Even if no direct
uninitialized field accesses or new buffer allocations are added in the diff itself,
a patch may alter control flow, bounds checking, or data length calculations in ways
that change how the rest of the code operates on existing buffers (e.g. allowing
uninitialized stack/heap memory to be read, copied to user space, or used in control
flow). Do not hesitate to use your code access tools to inspect the surrounding code,
called functions, and callers.

Set NeedsKMSAN=true ONLY IF the patch introduces or modifies:
1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb
   attributes, ioctl output arguments, socket options, or BPF buffers) where fields
   or structure padding might not be fully initialized/zeroed.
2. Conditional logic or branching that depends on potentially uninitialized variables
   or struct fields.
3. Allocation or initialization of complex data structures where uninitialized fields
   could be read later in reachable code paths.
4. Bounds checks, lengths, or logic in a way that allows surrounding code to access
   uninitialized bytes of existing buffers.

Set NeedsKMSAN=false IF:
- The code changes primarily risk out-of-bounds access, array overflows, NULL pointer
  dereferences, locking deadlocks, or use-after-free bugs (these are already caught
  by KASAN, LOCKDEP, or standard bug detectors).
- All stack/heap structures touched or introduced by the patch are fully zeroed
  or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied.
- The patch does not introduce any risk of uninitialized memory usage or info-leaks.

Use your code access tools to inspect the surrounding code if necessary, then provide
detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch.
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit a0b4f7e344ea151e0201c1a5949be01597a0a65f
Author: syz-cluster <triage@syzkaller.com>
Date:   Sun Sep 27 22:33:02 2026 +0000

    syz-cluster: applied patch under review

diff --git a/mm/memblock.c b/mm/memblock.c
index f5aaa38cfa313..87c71435c80c5 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -155,11 +155,6 @@ struct memblock_type physmem = {
  */
 static __refdata struct memblock_type *memblock_memory = &memblock.memory;
 
-#define for_each_memblock_type(i, memblock_type, rgn)			\
-	for (i = 0, rgn = &memblock_type->regions[0];			\
-	     i < memblock_type->cnt;					\
-	     i++, rgn = &memblock_type->regions[i])
-
 #define memblock_dbg(fmt, ...)						\
 	do {								\
 		if (memblock_debug)					\
@@ -591,6 +586,33 @@ static void __init_memblock memblock_insert_region(struct memblock_type *type,
 	type->total_size += size;
 }
 
+/**
+ * memblock_bsearch_start - Find the first region index where rend > base
+ * @type: memblock type to search
+ * @base: base physical address of the candidate range
+ *
+ * Returns the first region index that could potentially overlap @base.
+ */
+static int __init_memblock memblock_bsearch_start(struct memblock_type *type,
+						  phys_addr_t base)
+{
+	int mid, low = 0;
+	int high = type->cnt;
+
+	if (type->cnt && base >= type->regions[type->cnt - 1].base +
+				 type->regions[type->cnt - 1].size)
+		return type->cnt;
+
+	while (low < high) {
+		mid = (low + high) / 2;
+		if (type->regions[mid].base + type->regions[mid].size <= base)
+			low = mid + 1;
+		else
+			high = mid;
+	}
+	return low;
+}
+
 /**
  * memblock_add_range - add new memblock region
  * @type: memblock type to add new region into
@@ -614,8 +636,7 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,
 	bool insert = false;
 	phys_addr_t obase = base;
 	phys_addr_t end = base + memblock_cap_size(base, &size);
-	int idx, nr_new, start_rgn = -1, end_rgn;
-	struct memblock_region *rgn;
+	int idx, start_idx, nr_new, start_rgn = -1, end_rgn;
 
 	if (!size)
 		return 0;
@@ -650,8 +671,10 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,
 	 */
 	base = obase;
 	nr_new = 0;
+	start_idx = memblock_bsearch_start(type, base);
 
-	for_each_memblock_type(idx, type, rgn) {
+	for (idx = start_idx; idx < type->cnt; idx++) {
+		struct memblock_region *rgn = &type->regions[idx];
 		phys_addr_t rbase = rgn->base;
 		phys_addr_t rend = rbase + rgn->size;
 
@@ -814,8 +837,7 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
 					int *start_rgn, int *end_rgn)
 {
 	phys_addr_t end = base + memblock_cap_size(base, &size);
-	int idx;
-	struct memblock_region *rgn;
+	int idx, start_idx;
 
 	*start_rgn = *end_rgn = 0;
 
@@ -827,7 +849,10 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
 		if (memblock_double_array(type, base, size) < 0)
 			return -ENOMEM;
 
-	for_each_memblock_type(idx, type, rgn) {
+	start_idx = memblock_bsearch_start(type, base);
+
+	for (idx = start_idx; idx < type->cnt; idx++) {
+		struct memblock_region *rgn = &type->regions[idx];
 		phys_addr_t rbase = rgn->base;
 		phys_addr_t rend = rbase + rgn->size;
 
@@ -2067,19 +2092,10 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit)
 
 static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)
 {
-	unsigned int left = 0, right = type->cnt;
-
-	do {
-		unsigned int mid = (right + left) / 2;
+	int idx = memblock_bsearch_start(type, addr);
 
-		if (addr < type->regions[mid].base)
-			right = mid;
-		else if (addr >= (type->regions[mid].base +
-				  type->regions[mid].size))
-			left = mid + 1;
-		else
-			return mid;
-	} while (left < right);
+	if (idx < type->cnt && addr >= type->regions[idx].base)
+		return idx;
 	return -1;
 }
 
@@ -2194,11 +2210,11 @@ static void __init_memblock memblock_dump(struct memblock_type *type)
 	phys_addr_t base, end, size;
 	enum memblock_flags flags;
 	int idx;
-	struct memblock_region *rgn;
 
 	pr_info(" %s.cnt  = 0x%lx\n", type->name, type->cnt);
 
-	for_each_memblock_type(idx, type, rgn) {
+	for (idx = 0; idx < type->cnt; idx++) {
+		struct memblock_region *rgn = &type->regions[idx];
 		char nid_buf[32] = "";
 
 		base = rgn->base;

gemini-3.8-flash

null

null

							input: 3562
							output: 32
							thoughts: 1097
						

**Analyzing the `mm/memblock.c` Patch**

Okay, let's break this down. My task is to assess whether this patch series on `mm/memblock.c` requires KMSAN fuzzing over KASAN. From the initial context, this looks like a straightforward software auditing/security analysis task – benign severity, no malicious intent. I'm safe to proceed.

First, I need to understand what this patch is doing. It seems the core of the change is optimizing some linear searches within `memblock.c` using binary search. Specifically, it's replacing uses of the `for_each_memblock_type` macro and linear searches with a new function `memblock_bsearch_start`. This new function is a binary search algorithm to find a starting index for memory regions. It appears to be a performance optimization. The patch impacts `memblock_add_range`, `memblock_isolate_range`, `memblock_search`, and `memblock_dump`.

Now, considering the context, `mm/memblock.c` is the early boot physical memory allocator. This means it's running very early in the boot process, and most of its functions are `__init` or `__init_memblock`. My initial question is whether this code is even reachable from user space or through syscalls. Memblock being an early boot memory allocator makes me wonder about the fuzzing implications. Does syzkaller even target memblock? Are there any debugfs, sysfs, or memory hotplug interactions that might be relevant?

The key area of concern becomes uninitialized memory. Let's dig deeper: Does this patch introduce or modify any kernel structures that are sent to user space? No. Does it introduce conditional logic or branching that relies on uninitialized variables? I need to check the variables in the functions being modified: `memblock_bsearch_start`, `memblock_add_range`, `memblock_isolate_range`, `memblock_search`, and `memblock_dump`. From the code snippet, it looks like all the variables are initialized correctly, including those in the binary search. I've confirmed that the access of `type->regions` is within bounds.

However, I'm starting to get a little concerned. The binary search and its use in `memblock_add_range` and `memblock_isolate_range` introduce a new logic path. Even though the variables look initialized, is there a potential logic error or out-of-bounds access introduced by the `start_idx` value returned by the binary search? How did the original linear search work, and how might the binary search result in an issue in the subsequent loop logic? I need to review the original implementation of those loops to see what assumptions were made about the index being used. Time to get the original code and investigate.

{
  "Expression": "memblock_add_range",
  "PathPrefix": "mm/memblock.c"
}

{
  "Output": "mm/memblock.c=596=static int __init_memblock memblock_bsearch_start(struct memblock_type *type,\n--\nmm/memblock.c-616-/**\nmm/memblock.c:617: * memblock_add_range - add new memblock region\nmm/memblock.c-618- * @type: memblock type to add new region into\n--\nmm/memblock.c-631- */\nmm/memblock.c:632:static int __init_memblock memblock_add_range(struct memblock_type *type,\nmm/memblock.c-633-\t\t\t\tphys_addr_t base, phys_addr_t size,\n--\nmm/memblock.c-746- * Add new memblock region [@base, @base + @size) to the \"memory\"\nmm/memblock.c:747: * type. See memblock_add_range() description for mode details\nmm/memblock.c-748- *\n--\nmm/memblock.c=752=int __init_memblock memblock_add_node(phys_addr_t base, phys_addr_t size,\n--\nmm/memblock.c-759-\nmm/memblock.c:760:\treturn memblock_add_range(\u0026memblock.memory, base, size, nid, flags);\nmm/memblock.c-761-}\n--\nmm/memblock.c-768- * Add new memblock region [@base, @base + @size) to the \"memory\"\nmm/memblock.c:769: * type. See memblock_add_range() description for mode details\nmm/memblock.c-770- *\n--\nmm/memblock.c=774=int __init_memblock memblock_add(phys_addr_t base, phys_addr_t size)\n--\nmm/memblock.c-780-\nmm/memblock.c:781:\treturn memblock_add_range(\u0026memblock.memory, base, size, MAX_NUMNODES, 0);\nmm/memblock.c-782-}\n--\nmm/memblock.c=1032=int __init_memblock __memblock_reserve(phys_addr_t base, phys_addr_t size,\n--\nmm/memblock.c-1039-\nmm/memblock.c:1040:\treturn memblock_add_range(\u0026memblock.reserved, base, size, nid, flags);\nmm/memblock.c-1041-}\n--\nmm/memblock.c=1044=int __init_memblock memblock_physmem_add(phys_addr_t base, phys_addr_t size)\n--\nmm/memblock.c-1050-\nmm/memblock.c:1051:\treturn memblock_add_range(\u0026physmem, base, size, MAX_NUMNODES, 0);\nmm/memblock.c-1052-}\n"
}

gemini-3.8-flash

null

null

							input: 6044
							output: 34
							thoughts: 24
						

Okay, here's my take on those snippets, tailored for an expert's understanding:

**Analyzing `memblock_add_range` and `memblock_isolate_range`**

Right, let's dive into the code surrounding `memblock_add_range` and `memblock_isolate_range`. My immediate focus is on how these functions handle memory block management. I need to refresh my understanding of their interaction, especially in the context of the overall boot process and early memory allocation. I'm thinking about:

*   **Synchronization:** Are there any subtle race conditions or locking issues I should watch out for, particularly if these functions are called from different contexts during early boot? The `memblock` data structure itself usually implies some form of locking, but it's always worth confirming.
*   **Fragmentation:** I need to analyze how well these functions handle coalescing adjacent memory blocks or if they might lead to internal or external fragmentation over time, especially during complex memory map modifications. What's the strategy for splitting or merging?
*   **Error Handling:** It's critical to review how these functions respond to out-of-memory scenarios or invalid ranges. Do they return errors, panic, or something else? I want to understand what the upstream caller needs to do in error handling.
*   **Architecture Specifics:** I'm curious if there are any architecture-specific implementations or optimizations related to these functions that I should be aware of. Does a particular architecture impact its capabilities?
*   **Usage Context:** I want to consider where the functions are called from. Are they primarily used during early boot, device initialization, or during runtime? The context will influence my understanding of the criticality and performance constraints.
*   **Assumptions and Invariants:** What assumptions do these functions make about the memory map state? Are there any preconditions that need to be met before calling them?
*   **Range Validation:** How robust is the range validation performed within the functions? I need to look for any potential for integer overflows or other vulnerabilities related to range calculations.
*   **Interaction with other functions:** How does `memblock_add_range` and `memblock_isolate_range` interact with related functions such as `memblock_remove_range` and `memblock_find_range`? Are there any unexpected side effects to consider?

I'll be paying close attention to any uses of atomic operations, bitfields, or other low-level constructs that might indicate performance optimization or subtle concurrency issues. The ultimate goal is to get a very clear mental model of how these functions fit into the memory management jigsaw puzzle and to spot any potential trouble spots or opportunities for improvement.

{
  "File": "mm/memblock.c",
  "FirstLine": 645,
  "LineCount": 50
}

{
  "Contents": " 645:\t\tif (type-\u003eregions[0].size == 0) {\n 646:\t\t\tWARN_ON(type-\u003ecnt != 0 || type-\u003etotal_size);\n 647:\t\t\ttype-\u003eregions[0].base = base;\n 648:\t\t\ttype-\u003eregions[0].size = size;\n 649:\t\t\ttype-\u003eregions[0].flags = flags;\n 650:\t\t\tmemblock_set_region_node(\u0026type-\u003eregions[0], nid);\n 651:\t\t\ttype-\u003etotal_size = size;\n 652:\t\t\ttype-\u003ecnt = 1;\n 653:\t\t\treturn 0;\n 654:\t\t}\n 655:\t\n 656:\t\t/*\n 657:\t\t * The worst case is when new range overlaps all existing regions,\n 658:\t\t * then we'll need type-\u003ecnt + 1 empty regions in @type. So if\n 659:\t\t * type-\u003ecnt * 2 + 1 is less than or equal to type-\u003emax, we know\n 660:\t\t * that there is enough empty regions in @type, and we can insert\n 661:\t\t * regions directly.\n 662:\t\t */\n 663:\t\tif (type-\u003ecnt * 2 + 1 \u003c= type-\u003emax)\n 664:\t\t\tinsert = true;\n 665:\t\n 666:\trepeat:\n 667:\t\t/*\n 668:\t\t * The following is executed twice.  Once with %false @insert and\n 669:\t\t * then with %true.  The first counts the number of regions needed\n 670:\t\t * to accommodate the new area.  The second actually inserts them.\n 671:\t\t */\n 672:\t\tbase = obase;\n 673:\t\tnr_new = 0;\n 674:\t\tstart_idx = memblock_bsearch_start(type, base);\n 675:\t\n 676:\t\tfor (idx = start_idx; idx \u003c type-\u003ecnt; idx++) {\n 677:\t\t\tstruct memblock_region *rgn = \u0026type-\u003eregions[idx];\n 678:\t\t\tphys_addr_t rbase = rgn-\u003ebase;\n 679:\t\t\tphys_addr_t rend = rbase + rgn-\u003esize;\n 680:\t\n 681:\t\t\tif (rbase \u003e= end)\n 682:\t\t\t\tbreak;\n 683:\t\t\tif (rend \u003c= base)\n 684:\t\t\t\tcontinue;\n 685:\t\t\t/*\n 686:\t\t\t * @rgn overlaps.  If it separates the lower part of new\n 687:\t\t\t * area, insert that portion.\n 688:\t\t\t */\n 689:\t\t\tif (rbase \u003e base) {\n 690:\t#ifdef CONFIG_NUMA\n 691:\t\t\t\tWARN_ON(nid != memblock_get_region_node(rgn));\n 692:\t#endif\n 693:\t\t\t\tWARN_ON(flags != MEMBLOCK_NONE \u0026\u0026 flags != rgn-\u003eflags);\n 694:\t\t\t\tnr_new++;\n"
}

gemini-3.8-flash

null

null

							input: 7453
							output: 34
							thoughts: 15
						

Okay, here's my summarized thought process, assuming I'm an expert in this field, and speaking as myself:

**Delving Deeper: Investigating `memblock_isolate_range`**

Right, let's not just focus on `memblock_isolate_range` itself. That's obviously a crucial point to understand, but as an expert, I know that function rarely lives in a vacuum. To get a *real* handle on its behavior, and any potential issues or nuances surrounding it, I need to expand the scope of my investigation. I need to look at the surrounding code. What's calling this function? What's *being* called by this function? What are the implications of the calls before and after? What are the assumptions being made about the memory block being isolated? Essentially, I need to see the context of the function's usage to understand it. So, I need to check the lines of code around it. That's where the real answers usually reside. I'm thinking I'll start by checking the surrounding lines for any calls to `memblock_isolate_range` as well as variables involved around that function to understand more about its use.

{
  "File": "mm/memblock.c",
  "FirstLine": 835,
  "LineCount": 50
}

{
  "Contents": " 835:\tstatic int __init_memblock memblock_isolate_range(struct memblock_type *type,\n 836:\t\t\t\t\t\tphys_addr_t base, phys_addr_t size,\n 837:\t\t\t\t\t\tint *start_rgn, int *end_rgn)\n 838:\t{\n 839:\t\tphys_addr_t end = base + memblock_cap_size(base, \u0026size);\n 840:\t\tint idx, start_idx;\n 841:\t\n 842:\t\t*start_rgn = *end_rgn = 0;\n 843:\t\n 844:\t\tif (!size)\n 845:\t\t\treturn 0;\n 846:\t\n 847:\t\t/* we'll create at most two more regions */\n 848:\t\twhile (type-\u003ecnt + 2 \u003e type-\u003emax)\n 849:\t\t\tif (memblock_double_array(type, base, size) \u003c 0)\n 850:\t\t\t\treturn -ENOMEM;\n 851:\t\n 852:\t\tstart_idx = memblock_bsearch_start(type, base);\n 853:\t\n 854:\t\tfor (idx = start_idx; idx \u003c type-\u003ecnt; idx++) {\n 855:\t\t\tstruct memblock_region *rgn = \u0026type-\u003eregions[idx];\n 856:\t\t\tphys_addr_t rbase = rgn-\u003ebase;\n 857:\t\t\tphys_addr_t rend = rbase + rgn-\u003esize;\n 858:\t\n 859:\t\t\tif (rbase \u003e= end)\n 860:\t\t\t\tbreak;\n 861:\t\t\tif (rend \u003c= base)\n 862:\t\t\t\tcontinue;\n 863:\t\n 864:\t\t\tif (rbase \u003c base) {\n 865:\t\t\t\t/*\n 866:\t\t\t\t * @rgn intersects from below.  Split and continue\n 867:\t\t\t\t * to process the next region - the new top half.\n 868:\t\t\t\t */\n 869:\t\t\t\trgn-\u003ebase = base;\n 870:\t\t\t\trgn-\u003esize -= base - rbase;\n 871:\t\t\t\ttype-\u003etotal_size -= base - rbase;\n 872:\t\t\t\tmemblock_insert_region(type, idx, rbase, base - rbase,\n 873:\t\t\t\t\t\t       memblock_get_region_node(rgn),\n 874:\t\t\t\t\t\t       rgn-\u003eflags);\n 875:\t\t\t} else if (rend \u003e end) {\n 876:\t\t\t\t/*\n 877:\t\t\t\t * @rgn intersects from above.  Split and redo the\n 878:\t\t\t\t * current region - the new bottom half.\n 879:\t\t\t\t */\n 880:\t\t\t\trgn-\u003ebase = end;\n 881:\t\t\t\trgn-\u003esize -= end - rbase;\n 882:\t\t\t\ttype-\u003etotal_size -= end - rbase;\n 883:\t\t\t\tmemblock_insert_region(type, idx--, rbase, end - rbase,\n 884:\t\t\t\t\t\t       memblock_get_region_node(rgn),\n"
}

gemini-3.8-flash

null

null

							input: 8554
							output: 226
							thoughts: 908
						

**KMSAN Assessment: Optimization in `mm/memblock.c`**

Okay, so this patch in `mm/memblock.c` looks like a performance optimization. We're replacing linear searches through `type->regions` with a binary search, courtesy of `memblock_bsearch_start`, which seems sensible for potentially large region lists in `memblock_add_range`, `memblock_isolate_range`, and `memblock_search`. Also, the macro `for_each_memblock_type` is swapped out for an explicit loop.

My immediate thought is, "Are there any uninitialized memory issues introduced or exposed by these changes?" Let's break it down:

*   **No Uninitialized Memory Usage:** There are no newly allocated stack or heap buffers without initialization. Kernel structures aren't being copied to user space. There's no risk of padding leaks or uninitialized fields making their way into user space. Conditional jumps aren't dependent on uninitialized values. All variables used (indices like `idx`, `start_idx`, `mid`, `low`, and `high`) are integer indices and are properly initialized before use.

*   **Potential Bug Types:** Any bugs here are likely logical errors, like off-by-one errors or incorrect search bounds, which would lead to incorrect region indices or out-of-bounds array access on `type->regions`. But those issues will be picked up by KASAN or standard assertions. KMSAN isn't the right tool for those types of problems. Plus, `memblock` operates during early boot, well before user space even gets a chance to mount or for KMSAN to be running for user payloads.

Let's double-check the KMSAN rules to be absolutely sure:

"THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN, LOCKDEP, OR OTHER STANDARD BUG DETECTORS." Sounds good. We only need KMSAN if the patch introduces or exposes uninitialized memory risks *that are detected ONLY by KMSAN*.

The rules are pretty clear: We need KMSAN if the patch involves kernel structures sent to user space where fields might be uninitialized, conditional logic depending on potentially uninitialized variables, the allocation/initialization of complex data structures where uninitialized fields could be read later, or logic that allows access to uninitialized bytes of existing buffers. The rules say to set `NeedsKMSAN=false` if there is no risk of uninitialized memory usage or info-leaks, or if all structures are initialized before being read or copied.

Therefore, `NeedsKMSAN` is clearly `false`.

Now, for the justification for `set-results`:

*   This patch is optimizing memblock region lookups with binary search (`memblock_bsearch_start()`) which replaces linear iterations in `memblock_add_range`, `memblock_isolate_range`, and `memblock_search`.
*   There's no introduction or modification of user-space copy operations or information leaks.
*   No uninitialized variables or struct padding are read or exposed. All scalar variables are explicitly initialized before use.
*   Any potential issues with the binary search logic would lead to incorrect region indexing or out-of-bounds accesses on the array, which are covered by existing unit tests, kernel assertions, and KASAN. KMSAN is overkill here.
*   A dedicated KMSAN fuzzing session is not needed.

Time to call `set-results` and submit the assessment.

{
  "KMSANReasoning": "The patch optimizes memblock region lookups (in memblock_add_range, memblock_isolate_range, and memblock_search) by implementing a binary search helper memblock_bsearch_start() to locate candidate region indices instead of performing linear scans from index 0.\n\nNone of the changes touch kernel-to-user copy paths (no copy_to_user, netlink, ioctl, etc.), nor do they allocate or manipulate data structures with uninitialized fields or padding. All local variables (start_idx, low, high, mid) are fully initialized before use. Any potential bugs in this patch would be algorithmic or bounds-related (e.g., off-by-one errors or out-of-bounds indexing in the memblock region array), which are detected by KASAN, assertions, or functional tests. Because no uninitialized memory reads or information leaks are introduced or exposed, a dedicated KMSAN fuzzing session is not justified.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch optimizes memblock region lookups (in memblock_add_range, memblock_isolate_range, and memblock_search) by implementing a binary search helper memblock_bsearch_start() to locate candidate region indices instead of performing linear scans from index 0.\n\nNone of the changes touch kernel-to-user copy paths (no copy_to_user, netlink, ioctl, etc.), nor do they allocate or manipulate data structures with uninitialized fields or padding. All local variables (start_idx, low, high, mid) are fully initialized before use. Any potential bugs in this patch would be algorithmic or bounds-related (e.g., off-by-one errors or out-of-bounds indexing in the memblock region array), which are detected by KASAN, assertions, or functional tests. Because no uninitialized memory reads or information leaks are introduced or exposed, a dedicated KMSAN fuzzing session is not justified.",
  "NeedsKMSAN": false
}