AI Trajectory

null

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "KMSANReasoning": "",
  "NeedsKMSAN": false,
  "Reasoning": "The patch series adds support for AMD SEV-SNP RMPOPT (RMP Optimization) instructions and management for AMD Zen6+ host processors. These code paths require physical AMD hardware supporting SEV-SNP host features and the AMD Platform Security Processor (PSP), and are disabled when running inside virtualized environments (X86_FEATURE_HYPERVISOR disables CC_ATTR_HOST_SEV_SNP during boot). Consequently, the modified code paths are structurally unreachable in standard virtualized fuzzing environments.",
  "WorthFuzzing": false
}

null

{
  "PatchDiff": "commit cd86c682f817b1270a358533227ac60089eba64a\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Thu Sep 3 21:53:48 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h\nindex f70ee74b5f921..3b5b32d3391b5 100644\n--- a/arch/x86/include/asm/cpufeatures.h\n+++ b/arch/x86/include/asm/cpufeatures.h\n@@ -76,7 +76,7 @@\n #define X86_FEATURE_K8\t\t\t( 3*32+ 4) /* Opteron, Athlon64 */\n #define X86_FEATURE_ZEN5\t\t( 3*32+ 5) /* CPU based on Zen5 microarchitecture */\n #define X86_FEATURE_ZEN6\t\t( 3*32+ 6) /* CPU based on Zen6 microarchitecture */\n-/* Free                                 ( 3*32+ 7) */\n+#define X86_FEATURE_RMPOPT\t\t( 3*32+ 7) /* Support for AMD RMPOPT instruction */\n #define X86_FEATURE_CONSTANT_TSC\t( 3*32+ 8) /* \"constant_tsc\" TSC ticks at a constant rate */\n /* free: was #define X86_FEATURE_UP\t( 3*32+ 9) * \"up\" SMP kernel running on UP */\n #define X86_FEATURE_ART\t\t\t( 3*32+10) /* \"art\" Always running timer (ART) */\ndiff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h\nindex 3a8e51a0c9e88..1635e2e1c576a 100644\n--- a/arch/x86/include/asm/msr-index.h\n+++ b/arch/x86/include/asm/msr-index.h\n@@ -761,6 +761,9 @@\n #define MSR_AMD64_SEG_RMP_ENABLED_BIT\t0\n #define MSR_AMD64_SEG_RMP_ENABLED\tBIT_ULL(MSR_AMD64_SEG_RMP_ENABLED_BIT)\n #define MSR_AMD64_RMP_SEGMENT_SHIFT(x)\t(((x) \u0026 GENMASK_ULL(13, 8)) \u003e\u003e 8)\n+#define MSR_AMD64_RMPOPT_BASE\t\t0xc0010139\n+#define MSR_AMD64_RMPOPT_ENABLE_BIT\t0\n+#define MSR_AMD64_RMPOPT_ENABLE\t\tBIT_ULL(MSR_AMD64_RMPOPT_ENABLE_BIT)\n \n #define MSR_SVSM_CAA\t\t\t0xc001f000\n \ndiff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h\nindex 9e7a077c445dc..3235e171647dd 100644\n--- a/arch/x86/include/asm/sev.h\n+++ b/arch/x86/include/asm/sev.h\n@@ -662,6 +662,8 @@ static inline void snp_leak_pages(u64 pfn, unsigned int pages)\n \t__snp_leak_pages(pfn, pages, true);\n }\n int snp_prepare(void);\n+void snp_rmpopt_all_physmem(void);\n+void snp_setup_rmpopt(void);\n void snp_shutdown(void);\n #else\n static inline bool snp_probe_rmptable_info(void) { return false; }\n@@ -680,6 +682,8 @@ static inline void snp_leak_pages(u64 pfn, unsigned int npages) {}\n static inline void kdump_sev_callback(void) { }\n static inline void snp_fixup_e820_tables(void) {}\n static inline int snp_prepare(void) { return -ENODEV; }\n+static inline void snp_rmpopt_all_physmem(void) {}\n+static inline void snp_setup_rmpopt(void) {}\n static inline void snp_shutdown(void) {}\n #endif\n \ndiff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c\nindex 8665a6474806c..d1795ce219dab 100644\n--- a/arch/x86/kernel/cpu/scattered.c\n+++ b/arch/x86/kernel/cpu/scattered.c\n@@ -67,6 +67,7 @@ static const struct cpuid_bit cpuid_bits[] = {\n \t{ X86_FEATURE_PERFMON_V2,\t\tCPUID_EAX,  0, 0x80000022, 0 },\n \t{ X86_FEATURE_AMD_LBR_V2,\t\tCPUID_EAX,  1, 0x80000022, 0 },\n \t{ X86_FEATURE_AMD_LBR_PMC_FREEZE,\tCPUID_EAX,  2, 0x80000022, 0 },\n+\t{ X86_FEATURE_RMPOPT,\t\t\tCPUID_EDX,  0, 0x80000025, 0 },\n \t{ X86_FEATURE_AMD_HTR_CORES,\t\tCPUID_EAX, 30, 0x80000026, 0 },\n \t{ 0, 0, 0, 0, 0 }\n };\ndiff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c\nindex 5705723f1f412..0babf96e38c6f 100644\n--- a/arch/x86/kvm/svm/sev.c\n+++ b/arch/x86/kvm/svm/sev.c\n@@ -3032,6 +3032,16 @@ void sev_vm_destroy(struct kvm *kvm)\n \t\t */\n \t\tif (snp_decommission_context(kvm))\n \t\t\treturn;\n+\n+\t\t/*\n+\t\t * Perform RMP optimizations on memory freed by terminating\n+\t\t * guests.  The scan is deferred, so it normally runs after\n+\t\t * sev_gmem_invalidate() has converted this guest's pages back to\n+\t\t * shared, and picks them up then.  A very large guest whose\n+\t\t * conversion has not finished by then is picked up by a later\n+\t\t * teardown's scan.\n+\t\t */\n+\t\tsnp_rmpopt_all_physmem();\n \t} else {\n \t\tsev_unbind_asid(kvm, sev-\u003ehandle);\n \t}\ndiff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c\nindex cff285d8ad8e3..fb66a1aa6fc35 100644\n--- a/arch/x86/virt/svm/sev.c\n+++ b/arch/x86/virt/svm/sev.c\n@@ -19,6 +19,7 @@\n #include \u003clinux/iommu.h\u003e\n #include \u003clinux/amd-iommu.h\u003e\n #include \u003clinux/nospec.h\u003e\n+#include \u003clinux/workqueue.h\u003e\n \n #include \u003casm/sev.h\u003e\n #include \u003casm/processor.h\u003e\n@@ -124,6 +125,17 @@ static void *rmp_bookkeeping __ro_after_init;\n \n static u64 probed_rmp_base, probed_rmp_size;\n \n+static u64 rmpopt_pa_start, rmpopt_pa_end;\n+\n+enum rmpopt_op_type {\n+\tRMPOPT_OP_VERIFY_AND_REPORT_STATUS,\n+\tRMPOPT_OP_REPORT_STATUS\n+};\n+\n+static struct workqueue_struct *rmpopt_wq;\n+static struct delayed_work rmpopt_delayed_work;\n+static DEFINE_MUTEX(rmpopt_wq_mutex);\n+\n static LIST_HEAD(snp_leaked_pages_list);\n static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);\n \n@@ -513,7 +525,6 @@ static void clear_hsave_pa(void *arg)\n \n int snp_prepare(void)\n {\n-\tint ret;\n \tu64 val;\n \n \t/*\n@@ -526,14 +537,18 @@ int snp_prepare(void)\n \n \tclear_rmp();\n \n-\tcpus_read_lock();\n+\t/*\n+\t * No CPU may come online without SnpEn while SNP is active; disable\n+\t * hotplug here and re-enable it in snp_shutdown().\n+\t */\n+\tcpu_hotplug_disable();\n \n \tif (!cpumask_equal(cpu_online_mask, cpu_present_mask)) {\n-\t\tret = -EOPNOTSUPP;\n+\t\tcpu_hotplug_enable();\n \t\tpr_warn(\"SNP init failed: not all CPUs online. (%*pbl online \u003c-\u003e %*pbl present masks).\\n\",\n \t\t\tcpumask_pr_args(cpu_online_mask),\n \t\t\tcpumask_pr_args(cpu_present_mask));\n-\t\tgoto unlock;\n+\t\treturn -EOPNOTSUPP;\n \t}\n \n \twbinvd_on_all_cpus();\n@@ -548,14 +563,35 @@ int snp_prepare(void)\n \t/* SNP_INIT requires MSR_VM_HSAVE_PA to be cleared on all CPUs. */\n \ton_each_cpu(clear_hsave_pa, NULL, 1);\n \n-\tret = 0;\n+\treturn 0;\n+}\n+EXPORT_SYMBOL_FOR_MODULES(snp_prepare, \"ccp\");\n \n-unlock:\n-\tcpus_read_unlock();\n+static void rmpopt_disable(void)\n+{\n+\tint cpu;\n \n-\treturn ret;\n+\tguard(mutex)(\u0026rmpopt_wq_mutex);\n+\n+\t/*\n+\t * rmpopt_wq is non-NULL only after RMPOPT has been fully set up: the\n+\t * workqueue is allocated and the RMPOPT_BASE MSRs are programmed.\n+\t * snp_setup_rmpopt() resets it to NULL if any of those steps fail, so a\n+\t * NULL rmpopt_wq means nothing was set up and there is nothing to tear\n+\t * down.\n+\t */\n+\tif (!rmpopt_wq)\n+\t\treturn;\n+\n+\tcancel_delayed_work_sync(\u0026rmpopt_delayed_work);\n+\tdestroy_workqueue(rmpopt_wq);\n+\n+\tfor_each_cpu(cpu, cpu_primary_thread_mask)\n+\t\twrmsrq_on_cpu(cpu, MSR_AMD64_RMPOPT_BASE, 0);\n+\n+\trmpopt_pa_start = rmpopt_pa_end = 0;\n+\trmpopt_wq = NULL;\n }\n-EXPORT_SYMBOL_FOR_MODULES(snp_prepare, \"ccp\");\n \n void snp_shutdown(void)\n {\n@@ -565,11 +601,156 @@ void snp_shutdown(void)\n \tif (syscfg \u0026 MSR_AMD64_SYSCFG_SNP_EN)\n \t\treturn;\n \n+\trmpopt_disable();\n+\n \tclear_rmp();\n \ton_each_cpu(mfd_reconfigure, NULL, 1);\n+\n+\t/*\n+\t * The firmware has disabled SNP (SnpEn is clear), so re-enable CPU\n+\t * hotplug.  A legacy SNP shutdown returns above with SnpEn still set and\n+\t * leaves hotplug disabled.\n+\t */\n+\tcpu_hotplug_enable();\n }\n EXPORT_SYMBOL_FOR_MODULES(snp_shutdown, \"ccp\");\n \n+static bool rmpopt_capable(void)\n+{\n+\treturn cpu_feature_enabled(X86_FEATURE_RMPOPT) \u0026\u0026\n+\t       cc_platform_has(CC_ATTR_HOST_SEV_SNP);\n+}\n+\n+/*\n+ * RMPOPT optimizations skip RMP checks at 1GB granularity if this range of\n+ * memory does not contain any SNP guest memory.\n+ *\n+ * @pa is a system physical address; RMPOPT operates on the containing 1GB.\n+ */\n+static void rmpopt(u64 pa)\n+{\n+\tenum rmpopt_op_type op = RMPOPT_OP_VERIFY_AND_REPORT_STATUS;\n+\tu64 pa_start = ALIGN_DOWN(pa, SZ_1G);\n+\n+\tasm volatile(\".byte 0xf2, 0x0f, 0x01, 0xfc\"\n+\t\t     :: \"a\" (pa_start), \"c\" (op)\n+\t\t     : \"memory\", \"cc\");\n+}\n+\n+/* on_each_cpu() callback: optimize the whole RMPOPT range on this CPU. */\n+static void rmpopt_scan_range(void *arg)\n+{\n+\tu64 pa;\n+\n+\tfor (pa = rmpopt_pa_start; pa \u003c rmpopt_pa_end; pa += SZ_1G)\n+\t\trmpopt(pa);\n+}\n+\n+static void do_rmpopt_work(struct work_struct *work)\n+{\n+\t/*\n+\t * RMPOPT caches the results of a RMP table scan in reserved processor\n+\t * memory, allowing future invocations to skip such costly operations.\n+\t */\n+\tmigrate_disable();\n+\trmpopt_scan_range(NULL);\n+\tmigrate_enable();\n+\n+\ton_each_cpu_mask(cpu_primary_thread_mask, rmpopt_scan_range, NULL, true);\n+}\n+\n+/*\n+ * Delay, in milliseconds, before the RMP re-optimization pass runs after an\n+ * SNP guest is torn down.  snp_rmpopt_all_physmem() re-arms the delayed work\n+ * with mod_delayed_work() on each teardown, so the pass fires this long after\n+ * the last teardown.  This coalesces a burst of teardowns into a single scan\n+ * and gives each guest's pages time to be converted back to the shared,\n+ * hypervisor-owned state before the scan re-optimizes their 1GB regions.  The\n+ * 10 second value is a heuristic trading re-optimization latency against\n+ * scanning too eagerly.\n+ */\n+#define RMPOPT_WORK_TIMEOUT\t(10 * MSEC_PER_SEC)\n+\n+void snp_rmpopt_all_physmem(void)\n+{\n+\tif (!rmpopt_capable())\n+\t\treturn;\n+\n+\tguard(mutex)(\u0026rmpopt_wq_mutex);\n+\n+\tif (!rmpopt_wq)\n+\t\treturn;\n+\n+\tmod_delayed_work(rmpopt_wq, \u0026rmpopt_delayed_work,\n+\t\t\t msecs_to_jiffies(RMPOPT_WORK_TIMEOUT));\n+}\n+EXPORT_SYMBOL_FOR_MODULES(snp_rmpopt_all_physmem, \"kvm-amd\");\n+\n+void snp_setup_rmpopt(void)\n+{\n+\tu64 rmpopt_base;\n+\tint cpu;\n+\n+\tif (!rmpopt_capable())\n+\t\treturn;\n+\n+\tguard(mutex)(\u0026rmpopt_wq_mutex);\n+\n+\t/*\n+\t * On re-initialization after a legacy SNP shutdown (SNP_SHUTDOWN_EX\n+\t * with x86_snp_shutdown=0), snp_shutdown() and thus rmpopt_disable() are\n+\t * skipped, so the workqueue, delayed work and per-CPU RMPOPT_BASE MSRs\n+\t * are still set up and valid (SnpEn stayed set and CPU hotplug stayed\n+\t * disabled).  Rather than re-doing the setup, which would leak the\n+\t * existing state, just re-queue the optimization pass to re-optimize any\n+\t * memory the previous SNP session de-optimized.\n+\t */\n+\tif (rmpopt_wq) {\n+\t\tqueue_delayed_work(rmpopt_wq, \u0026rmpopt_delayed_work, 0);\n+\t\treturn;\n+\t}\n+\n+\t/*\n+\t * Create an RMPOPT-specific workqueue to avoid scheduling\n+\t * RMPOPT workitem on the global system workqueue.\n+\t */\n+\trmpopt_wq = alloc_workqueue(\"rmpopt_wq\", WQ_UNBOUND, 1);\n+\tif (!rmpopt_wq) {\n+\t\tpr_err(\"Failed to allocate RMPOPT workqueue\\n\");\n+\t\treturn;\n+\t}\n+\n+\tINIT_DELAYED_WORK(\u0026rmpopt_delayed_work, do_rmpopt_work);\n+\n+\trmpopt_pa_start = ALIGN_DOWN(PFN_PHYS(min_low_pfn), SZ_1G);\n+\trmpopt_base = rmpopt_pa_start | MSR_AMD64_RMPOPT_ENABLE;\n+\n+\t/*\n+\t * Per-CPU RMPOPT tables cover at most 2 TB.  Program each core's\n+\t * RMPOPT_BASE with the start of RAM to optimize up to 2 TB.\n+\t */\n+\tfor_each_cpu(cpu, cpu_primary_thread_mask)\n+\t\twrmsrq_on_cpu(cpu, MSR_AMD64_RMPOPT_BASE, rmpopt_base);\n+\n+\trmpopt_pa_end = ALIGN(PFN_PHYS(max_pfn), SZ_1G);\n+\n+\t/* Limit memory scanning to 2TB of RAM */\n+\tif ((rmpopt_pa_end - rmpopt_pa_start) \u003e SZ_2T) {\n+\t\tpr_info(\"RMPOPT coverage limited to 2TB; memory above 0x%llx not optimized\\n\",\n+\t\t\trmpopt_pa_start + SZ_2T);\n+\t\trmpopt_pa_end = rmpopt_pa_start + SZ_2T;\n+\t}\n+\n+\t/*\n+\t * Once all per-CPU RMPOPT tables have been configured, enable RMPOPT\n+\t * optimizations on all physical memory.\n+\t */\n+\tqueue_delayed_work(rmpopt_wq, \u0026rmpopt_delayed_work, 0);\n+\n+\tpr_info(\"RMPOPT optimizations enabled\\n\");\n+}\n+EXPORT_SYMBOL_FOR_MODULES(snp_setup_rmpopt, \"ccp\");\n+\n /*\n  * Do the necessary preparations which are verified by the firmware as\n  * described in the SNP_INIT_EX firmware command description in the SNP\n@@ -577,6 +758,8 @@ EXPORT_SYMBOL_FOR_MODULES(snp_shutdown, \"ccp\");\n  */\n int __init snp_rmptable_init(void)\n {\n+\tu64 val;\n+\n \tif (WARN_ON_ONCE(!cc_platform_has(CC_ATTR_HOST_SEV_SNP)))\n \t\treturn -ENOSYS;\n \n@@ -586,6 +769,15 @@ int __init snp_rmptable_init(void)\n \tif (!setup_rmptable())\n \t\treturn -ENOSYS;\n \n+\t/*\n+\t * On a kexec boot SNP may already be enabled (legacy firmware leaves\n+\t * SnpEn set across shutdown), in which case snp_prepare() bails without\n+\t * disabling CPU hotplug, so disable it here.\n+\t */\n+\trdmsrq(MSR_AMD64_SYSCFG, val);\n+\tif (val \u0026 MSR_AMD64_SYSCFG_SNP_EN)\n+\t\tcpu_hotplug_disable();\n+\n \t/*\n \t * Setting crash_kexec_post_notifiers to 'true' to ensure that SNP panic\n \t * notifier is invoked to do SNP IOMMU shutdown before kdump.\n@@ -683,13 +875,21 @@ static bool probe_segmented_rmptable_info(void)\n \n bool snp_probe_rmptable_info(void)\n {\n-\tif (cpu_feature_enabled(X86_FEATURE_SEGMENTED_RMP))\n+\tif (cpu_feature_enabled(X86_FEATURE_SEGMENTED_RMP)) {\n \t\trdmsrq(MSR_AMD64_RMP_CFG, rmp_cfg);\n \n-\tif (rmp_cfg \u0026 MSR_AMD64_SEG_RMP_ENABLED)\n-\t\treturn probe_segmented_rmptable_info();\n-\telse\n-\t\treturn probe_contiguous_rmptable_info();\n+\t\tif (rmp_cfg \u0026 MSR_AMD64_SEG_RMP_ENABLED)\n+\t\t\treturn probe_segmented_rmptable_info();\n+\t}\n+\n+\t/*\n+\t * Segmented RMP is either not supported on the platform or is\n+\t * disabled by the firmware.  RMPOPT is not supported without\n+\t * segmented RMP.\n+\t */\n+\tsetup_clear_cpu_cap(X86_FEATURE_RMPOPT);\n+\n+\treturn probe_contiguous_rmptable_info();\n }\n \n /*\ndiff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c\nindex f833cb7e4da36..287a8345854ba 100644\n--- a/drivers/crypto/ccp/sev-dev.c\n+++ b/drivers/crypto/ccp/sev-dev.c\n@@ -1663,6 +1663,8 @@ static int __sev_snp_init_locked(int *error, unsigned int max_snp_asid)\n \n \tsev_es_tmr_size = SNP_TMR_SIZE;\n \n+\tsnp_setup_rmpopt();\n+\n \treturn 0;\n }\n \n"
}

core

null

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "Reasoning": "The patch series adds support for AMD SEV-SNP RMPOPT (RMP Optimization) instructions and management for AMD Zen6+ host processors. These code paths require physical AMD hardware supporting SEV-SNP host features and the AMD Platform Security Processor (PSP), and are disabled when running inside virtualized environments (X86_FEATURE_HYPERVISOR disables CC_ATTR_HOST_SEV_SNP during boot). Consequently, the modified code paths are structurally unreachable in standard virtualized fuzzing environments.",
  "WorthFuzzing": false
}

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 cd86c682f817b1270a358533227ac60089eba64a
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Sep 3 21:53:48 2026 +0000

    syz-cluster: applied patch under review

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index f70ee74b5f921..3b5b32d3391b5 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -76,7 +76,7 @@
 #define X86_FEATURE_K8			( 3*32+ 4) /* Opteron, Athlon64 */
 #define X86_FEATURE_ZEN5		( 3*32+ 5) /* CPU based on Zen5 microarchitecture */
 #define X86_FEATURE_ZEN6		( 3*32+ 6) /* CPU based on Zen6 microarchitecture */
-/* Free                                 ( 3*32+ 7) */
+#define X86_FEATURE_RMPOPT		( 3*32+ 7) /* Support for AMD RMPOPT instruction */
 #define X86_FEATURE_CONSTANT_TSC	( 3*32+ 8) /* "constant_tsc" TSC ticks at a constant rate */
 /* free: was #define X86_FEATURE_UP	( 3*32+ 9) * "up" SMP kernel running on UP */
 #define X86_FEATURE_ART			( 3*32+10) /* "art" Always running timer (ART) */
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 3a8e51a0c9e88..1635e2e1c576a 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -761,6 +761,9 @@
 #define MSR_AMD64_SEG_RMP_ENABLED_BIT	0
 #define MSR_AMD64_SEG_RMP_ENABLED	BIT_ULL(MSR_AMD64_SEG_RMP_ENABLED_BIT)
 #define MSR_AMD64_RMP_SEGMENT_SHIFT(x)	(((x) & GENMASK_ULL(13, 8)) >> 8)
+#define MSR_AMD64_RMPOPT_BASE		0xc0010139
+#define MSR_AMD64_RMPOPT_ENABLE_BIT	0
+#define MSR_AMD64_RMPOPT_ENABLE		BIT_ULL(MSR_AMD64_RMPOPT_ENABLE_BIT)
 
 #define MSR_SVSM_CAA			0xc001f000
 
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 9e7a077c445dc..3235e171647dd 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -662,6 +662,8 @@ static inline void snp_leak_pages(u64 pfn, unsigned int pages)
 	__snp_leak_pages(pfn, pages, true);
 }
 int snp_prepare(void);
+void snp_rmpopt_all_physmem(void);
+void snp_setup_rmpopt(void);
 void snp_shutdown(void);
 #else
 static inline bool snp_probe_rmptable_info(void) { return false; }
@@ -680,6 +682,8 @@ static inline void snp_leak_pages(u64 pfn, unsigned int npages) {}
 static inline void kdump_sev_callback(void) { }
 static inline void snp_fixup_e820_tables(void) {}
 static inline int snp_prepare(void) { return -ENODEV; }
+static inline void snp_rmpopt_all_physmem(void) {}
+static inline void snp_setup_rmpopt(void) {}
 static inline void snp_shutdown(void) {}
 #endif
 
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index 8665a6474806c..d1795ce219dab 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -67,6 +67,7 @@ static const struct cpuid_bit cpuid_bits[] = {
 	{ X86_FEATURE_PERFMON_V2,		CPUID_EAX,  0, 0x80000022, 0 },
 	{ X86_FEATURE_AMD_LBR_V2,		CPUID_EAX,  1, 0x80000022, 0 },
 	{ X86_FEATURE_AMD_LBR_PMC_FREEZE,	CPUID_EAX,  2, 0x80000022, 0 },
+	{ X86_FEATURE_RMPOPT,			CPUID_EDX,  0, 0x80000025, 0 },
 	{ X86_FEATURE_AMD_HTR_CORES,		CPUID_EAX, 30, 0x80000026, 0 },
 	{ 0, 0, 0, 0, 0 }
 };
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 5705723f1f412..0babf96e38c6f 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3032,6 +3032,16 @@ void sev_vm_destroy(struct kvm *kvm)
 		 */
 		if (snp_decommission_context(kvm))
 			return;
+
+		/*
+		 * Perform RMP optimizations on memory freed by terminating
+		 * guests.  The scan is deferred, so it normally runs after
+		 * sev_gmem_invalidate() has converted this guest's pages back to
+		 * shared, and picks them up then.  A very large guest whose
+		 * conversion has not finished by then is picked up by a later
+		 * teardown's scan.
+		 */
+		snp_rmpopt_all_physmem();
 	} else {
 		sev_unbind_asid(kvm, sev->handle);
 	}
diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index cff285d8ad8e3..fb66a1aa6fc35 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -19,6 +19,7 @@
 #include <linux/iommu.h>
 #include <linux/amd-iommu.h>
 #include <linux/nospec.h>
+#include <linux/workqueue.h>
 
 #include <asm/sev.h>
 #include <asm/processor.h>
@@ -124,6 +125,17 @@ static void *rmp_bookkeeping __ro_after_init;
 
 static u64 probed_rmp_base, probed_rmp_size;
 
+static u64 rmpopt_pa_start, rmpopt_pa_end;
+
+enum rmpopt_op_type {
+	RMPOPT_OP_VERIFY_AND_REPORT_STATUS,
+	RMPOPT_OP_REPORT_STATUS
+};
+
+static struct workqueue_struct *rmpopt_wq;
+static struct delayed_work rmpopt_delayed_work;
+static DEFINE_MUTEX(rmpopt_wq_mutex);
+
 static LIST_HEAD(snp_leaked_pages_list);
 static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);
 
@@ -513,7 +525,6 @@ static void clear_hsave_pa(void *arg)
 
 int snp_prepare(void)
 {
-	int ret;
 	u64 val;
 
 	/*
@@ -526,14 +537,18 @@ int snp_prepare(void)
 
 	clear_rmp();
 
-	cpus_read_lock();
+	/*
+	 * No CPU may come online without SnpEn while SNP is active; disable
+	 * hotplug here and re-enable it in snp_shutdown().
+	 */
+	cpu_hotplug_disable();
 
 	if (!cpumask_equal(cpu_online_mask, cpu_present_mask)) {
-		ret = -EOPNOTSUPP;
+		cpu_hotplug_enable();
 		pr_warn("SNP init failed: not all CPUs online. (%*pbl online <-> %*pbl present masks).\n",
 			cpumask_pr_args(cpu_online_mask),
 			cpumask_pr_args(cpu_present_mask));
-		goto unlock;
+		return -EOPNOTSUPP;
 	}
 
 	wbinvd_on_all_cpus();
@@ -548,14 +563,35 @@ int snp_prepare(void)
 	/* SNP_INIT requires MSR_VM_HSAVE_PA to be cleared on all CPUs. */
 	on_each_cpu(clear_hsave_pa, NULL, 1);
 
-	ret = 0;
+	return 0;
+}
+EXPORT_SYMBOL_FOR_MODULES(snp_prepare, "ccp");
 
-unlock:
-	cpus_read_unlock();
+static void rmpopt_disable(void)
+{
+	int cpu;
 
-	return ret;
+	guard(mutex)(&rmpopt_wq_mutex);
+
+	/*
+	 * rmpopt_wq is non-NULL only after RMPOPT has been fully set up: the
+	 * workqueue is allocated and the RMPOPT_BASE MSRs are programmed.
+	 * snp_setup_rmpopt() resets it to NULL if any of those steps fail, so a
+	 * NULL rmpopt_wq means nothing was set up and there is nothing to tear
+	 * down.
+	 */
+	if (!rmpopt_wq)
+		return;
+
+	cancel_delayed_work_sync(&rmpopt_delayed_work);
+	destroy_workqueue(rmpopt_wq);
+
+	for_each_cpu(cpu, cpu_primary_thread_mask)
+		wrmsrq_on_cpu(cpu, MSR_AMD64_RMPOPT_BASE, 0);
+
+	rmpopt_pa_start = rmpopt_pa_end = 0;
+	rmpopt_wq = NULL;
 }
-EXPORT_SYMBOL_FOR_MODULES(snp_prepare, "ccp");
 
 void snp_shutdown(void)
 {
@@ -565,11 +601,156 @@ void snp_shutdown(void)
 	if (syscfg & MSR_AMD64_SYSCFG_SNP_EN)
 		return;
 
+	rmpopt_disable();
+
 	clear_rmp();
 	on_each_cpu(mfd_reconfigure, NULL, 1);
+
+	/*
+	 * The firmware has disabled SNP (SnpEn is clear), so re-enable CPU
+	 * hotplug.  A legacy SNP shutdown returns above with SnpEn still set and
+	 * leaves hotplug disabled.
+	 */
+	cpu_hotplug_enable();
 }
 EXPORT_SYMBOL_FOR_MODULES(snp_shutdown, "ccp");
 
+static bool rmpopt_capable(void)
+{
+	return cpu_feature_enabled(X86_FEATURE_RMPOPT) &&
+	       cc_platform_has(CC_ATTR_HOST_SEV_SNP);
+}
+
+/*
+ * RMPOPT optimizations skip RMP checks at 1GB granularity if this range of
+ * memory does not contain any SNP guest memory.
+ *
+ * @pa is a system physical address; RMPOPT operates on the containing 1GB.
+ */
+static void rmpopt(u64 pa)
+{
+	enum rmpopt_op_type op = RMPOPT_OP_VERIFY_AND_REPORT_STATUS;
+	u64 pa_start = ALIGN_DOWN(pa, SZ_1G);
+
+	asm volatile(".byte 0xf2, 0x0f, 0x01, 0xfc"
+		     :: "a" (pa_start), "c" (op)
+		     : "memory", "cc");
+}
+
+/* on_each_cpu() callback: optimize the whole RMPOPT range on this CPU. */
+static void rmpopt_scan_range(void *arg)
+{
+	u64 pa;
+
+	for (pa = rmpopt_pa_start; pa < rmpopt_pa_end; pa += SZ_1G)
+		rmpopt(pa);
+}
+
+static void do_rmpopt_work(struct work_struct *work)
+{
+	/*
+	 * RMPOPT caches the results of a RMP table scan in reserved processor
+	 * memory, allowing future invocations to skip such costly operations.
+	 */
+	migrate_disable();
+	rmpopt_scan_range(NULL);
+	migrate_enable();
+
+	on_each_cpu_mask(cpu_primary_thread_mask, rmpopt_scan_range, NULL, true);
+}
+
+/*
+ * Delay, in milliseconds, before the RMP re-optimization pass runs after an
+ * SNP guest is torn down.  snp_rmpopt_all_physmem() re-arms the delayed work
+ * with mod_delayed_work() on each teardown, so the pass fires this long after
+ * the last teardown.  This coalesces a burst of teardowns into a single scan
+ * and gives each guest's pages time to be converted back to the shared,
+ * hypervisor-owned state before the scan re-optimizes their 1GB regions.  The
+ * 10 second value is a heuristic trading re-optimization latency against
+ * scanning too eagerly.
+ */
+#define RMPOPT_WORK_TIMEOUT	(10 * MSEC_PER_SEC)
+
+void snp_rmpopt_all_physmem(void)
+{
+	if (!rmpopt_capable())
+		return;
+
+	guard(mutex)(&rmpopt_wq_mutex);
+
+	if (!rmpopt_wq)
+		return;
+
+	mod_delayed_work(rmpopt_wq, &rmpopt_delayed_work,
+			 msecs_to_jiffies(RMPOPT_WORK_TIMEOUT));
+}
+EXPORT_SYMBOL_FOR_MODULES(snp_rmpopt_all_physmem, "kvm-amd");
+
+void snp_setup_rmpopt(void)
+{
+	u64 rmpopt_base;
+	int cpu;
+
+	if (!rmpopt_capable())
+		return;
+
+	guard(mutex)(&rmpopt_wq_mutex);
+
+	/*
+	 * On re-initialization after a legacy SNP shutdown (SNP_SHUTDOWN_EX
+	 * with x86_snp_shutdown=0), snp_shutdown() and thus rmpopt_disable() are
+	 * skipped, so the workqueue, delayed work and per-CPU RMPOPT_BASE MSRs
+	 * are still set up and valid (SnpEn stayed set and CPU hotplug stayed
+	 * disabled).  Rather than re-doing the setup, which would leak the
+	 * existing state, just re-queue the optimization pass to re-optimize any
+	 * memory the previous SNP session de-optimized.
+	 */
+	if (rmpopt_wq) {
+		queue_delayed_work(rmpopt_wq, &rmpopt_delayed_work, 0);
+		return;
+	}
+
+	/*
+	 * Create an RMPOPT-specific workqueue to avoid scheduling
+	 * RMPOPT workitem on the global system workqueue.
+	 */
+	rmpopt_wq = alloc_workqueue("rmpopt_wq", WQ_UNBOUND, 1);
+	if (!rmpopt_wq) {
+		pr_err("Failed to allocate RMPOPT workqueue\n");
+		return;
+	}
+
+	INIT_DELAYED_WORK(&rmpopt_delayed_work, do_rmpopt_work);
+
+	rmpopt_pa_start = ALIGN_DOWN(PFN_PHYS(min_low_pfn), SZ_1G);
+	rmpopt_base = rmpopt_pa_start | MSR_AMD64_RMPOPT_ENABLE;
+
+	/*
+	 * Per-CPU RMPOPT tables cover at most 2 TB.  Program each core's
+	 * RMPOPT_BASE with the start of RAM to optimize up to 2 TB.
+	 */
+	for_each_cpu(cpu, cpu_primary_thread_mask)
+		wrmsrq_on_cpu(cpu, MSR_AMD64_RMPOPT_BASE, rmpopt_base);
+
+	rmpopt_pa_end = ALIGN(PFN_PHYS(max_pfn), SZ_1G);
+
+	/* Limit memory scanning to 2TB of RAM */
+	if ((rmpopt_pa_end - rmpopt_pa_start) > SZ_2T) {
+		pr_info("RMPOPT coverage limited to 2TB; memory above 0x%llx not optimized\n",
+			rmpopt_pa_start + SZ_2T);
+		rmpopt_pa_end = rmpopt_pa_start + SZ_2T;
+	}
+
+	/*
+	 * Once all per-CPU RMPOPT tables have been configured, enable RMPOPT
+	 * optimizations on all physical memory.
+	 */
+	queue_delayed_work(rmpopt_wq, &rmpopt_delayed_work, 0);
+
+	pr_info("RMPOPT optimizations enabled\n");
+}
+EXPORT_SYMBOL_FOR_MODULES(snp_setup_rmpopt, "ccp");
+
 /*
  * Do the necessary preparations which are verified by the firmware as
  * described in the SNP_INIT_EX firmware command description in the SNP
@@ -577,6 +758,8 @@ EXPORT_SYMBOL_FOR_MODULES(snp_shutdown, "ccp");
  */
 int __init snp_rmptable_init(void)
 {
+	u64 val;
+
 	if (WARN_ON_ONCE(!cc_platform_has(CC_ATTR_HOST_SEV_SNP)))
 		return -ENOSYS;
 
@@ -586,6 +769,15 @@ int __init snp_rmptable_init(void)
 	if (!setup_rmptable())
 		return -ENOSYS;
 
+	/*
+	 * On a kexec boot SNP may already be enabled (legacy firmware leaves
+	 * SnpEn set across shutdown), in which case snp_prepare() bails without
+	 * disabling CPU hotplug, so disable it here.
+	 */
+	rdmsrq(MSR_AMD64_SYSCFG, val);
+	if (val & MSR_AMD64_SYSCFG_SNP_EN)
+		cpu_hotplug_disable();
+
 	/*
 	 * Setting crash_kexec_post_notifiers to 'true' to ensure that SNP panic
 	 * notifier is invoked to do SNP IOMMU shutdown before kdump.
@@ -683,13 +875,21 @@ static bool probe_segmented_rmptable_info(void)
 
 bool snp_probe_rmptable_info(void)
 {
-	if (cpu_feature_enabled(X86_FEATURE_SEGMENTED_RMP))
+	if (cpu_feature_enabled(X86_FEATURE_SEGMENTED_RMP)) {
 		rdmsrq(MSR_AMD64_RMP_CFG, rmp_cfg);
 
-	if (rmp_cfg & MSR_AMD64_SEG_RMP_ENABLED)
-		return probe_segmented_rmptable_info();
-	else
-		return probe_contiguous_rmptable_info();
+		if (rmp_cfg & MSR_AMD64_SEG_RMP_ENABLED)
+			return probe_segmented_rmptable_info();
+	}
+
+	/*
+	 * Segmented RMP is either not supported on the platform or is
+	 * disabled by the firmware.  RMPOPT is not supported without
+	 * segmented RMP.
+	 */
+	setup_clear_cpu_cap(X86_FEATURE_RMPOPT);
+
+	return probe_contiguous_rmptable_info();
 }
 
 /*
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index f833cb7e4da36..287a8345854ba 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -1663,6 +1663,8 @@ static int __sev_snp_init_locked(int *error, unsigned int max_snp_asid)
 
 	sev_es_tmr_size = SNP_TMR_SIZE;
 
+	snp_setup_rmpopt();
+
 	return 0;
 }
 

gemini-3.7-flash

null

null

							input: 8263
							output: 24
							thoughts: 651
						

**Analyzing the SEV-SNP Patch for Fuzzing Potential**

Okay, let's break this down. My initial assessment is: is this patch fuzz-worthy, and if so, how do we best approach it? First, I need to get a handle on what's changed. Looks like we've got some new definitions related to `RMPOPT` (Restricted Memory Protection Optional) in the `x86` architecture, specifically related to AMD SEV-SNP (Secure Encrypted Virtualization - Secure Nested Paging).

I see header files defining `X86_FEATURE_RMPOPT`, MSRs like `MSR_AMD64_RMPOPT_BASE`, and some supporting functions like `snp_rmpopt_all_physmem` and `snp_setup_rmpopt`. The changes are spread across various parts of the kernel. We're touching `cpufeatures.h`, `msr-index.h`, `sev.h`, the `scattered.c` file (which now includes the `X86_FEATURE_RMPOPT`), and then both the KVM and standard virtualization SVM code. It seems like the KVM changes are focused on enabling and disabling `RMPOPT`, and the SEV-SNP host setup. The crypto driver also gets involved, calling `snp_setup_rmpopt()` within `sev_snp_init_locked()`.

Now, the critical question: can we even *fuzz* this in a typical environment? My immediate concern is SEV-SNP's reliance on specific AMD hardware and potentially a specific CCP (Cryptographic Coprocessor) or firmware. I need to figure out if this functionality is realistically reachable in a QEMU setup, or GCE for that matter, or if we're going to need some custom environment to trigger the new code paths.

I need to confirm if we can run the AMD SEV-SNP host in standard QEMU/nested virtualization, or if it requires specific hardware/firmware, let's verify how `cc_platform_has(CC_ATTR_HOST_SEV_SNP)` works, or what the Kconfig settings are. I'll need to check the Kconfig, probably use grep, or just read the code to see how SEV-SNP is configured, and if there are any conditional dependencies that we need to account for. If it's a hardware-gated feature, that's a whole different ballgame for fuzzing.

{
  "Expression": "CC_ATTR_HOST_SEV_SNP"
}

{
  "Output": "arch/x86/coco/core.c=70=static bool noinstr amd_cc_platform_has(enum cc_attr attr)\n--\narch/x86/coco/core.c-103-\narch/x86/coco/core.c:104:\tcase CC_ATTR_HOST_SEV_SNP:\narch/x86/coco/core.c-105-\t\treturn cc_flags.host_sev_snp;\n--\narch/x86/coco/core.c=170=static void amd_cc_platform_clear(enum cc_attr attr)\n--\narch/x86/coco/core.c-172-\tswitch (attr) {\narch/x86/coco/core.c:173:\tcase CC_ATTR_HOST_SEV_SNP:\narch/x86/coco/core.c-174-\t\tcc_flags.host_sev_snp = 0;\n--\narch/x86/coco/core.c=192=static void amd_cc_platform_set(enum cc_attr attr)\n--\narch/x86/coco/core.c-194-\tswitch (attr) {\narch/x86/coco/core.c:195:\tcase CC_ATTR_HOST_SEV_SNP:\narch/x86/coco/core.c-196-\t\tcc_flags.host_sev_snp = 1;\n--\narch/x86/kernel/cpu/amd.c=356=static void bsp_determine_snp(struct cpuinfo_x86 *c)\n--\narch/x86/kernel/cpu/amd.c-373-\t\t    snp_probe_rmptable_info()) {\narch/x86/kernel/cpu/amd.c:374:\t\t\tcc_platform_set(CC_ATTR_HOST_SEV_SNP);\narch/x86/kernel/cpu/amd.c-375-\t\t} else {\narch/x86/kernel/cpu/amd.c-376-\t\t\tsetup_clear_cpu_cap(X86_FEATURE_SEV_SNP);\narch/x86/kernel/cpu/amd.c:377:\t\t\tcc_platform_clear(CC_ATTR_HOST_SEV_SNP);\narch/x86/kernel/cpu/amd.c-378-\t\t}\n--\narch/x86/kernel/cpu/mtrr/generic.c=104=static inline void k8_check_syscfg_dram_mod_en(void)\n--\narch/x86/kernel/cpu/mtrr/generic.c-111-\narch/x86/kernel/cpu/mtrr/generic.c:112:\tif (cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/kernel/cpu/mtrr/generic.c-113-\t\treturn;\n--\narch/x86/kvm/svm/avic.c=1257=static bool __init avic_want_avic_enabled(void)\n--\narch/x86/kvm/svm/avic.c-1280-\narch/x86/kvm/svm/avic.c:1281:\tif (cc_platform_has(CC_ATTR_HOST_SEV_SNP) \u0026\u0026\narch/x86/kvm/svm/avic.c-1282-\t    !boot_cpu_has(X86_FEATURE_HV_INUSE_WR_ALLOWED)) {\n--\narch/x86/kvm/svm/sev.c=1259=static void *sev_dbg_crypt_slow_alloc(struct page *page, unsigned long __va,\n--\narch/x86/kvm/svm/sev.c-1293-\t */\narch/x86/kvm/svm/sev.c:1294:\tif (cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/kvm/svm/sev.c-1295-\t\treturn (void *)__get_free_page(GFP_KERNEL);\n--\narch/x86/kvm/svm/sev.c=1300=static void sev_dbg_crypt_slow_free(void *buf)\narch/x86/kvm/svm/sev.c-1301-{\narch/x86/kvm/svm/sev.c:1302:\tif (cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/kvm/svm/sev.c-1303-\t\tfree_page((unsigned long)buf);\n--\narch/x86/kvm/svm/sev.c=3096=void __init sev_hardware_setup(void)\n--\narch/x86/kvm/svm/sev.c-3200-\tsev_es_supported = true;\narch/x86/kvm/svm/sev.c:3201:\tsev_snp_supported = sev_snp_enabled \u0026\u0026 cc_platform_has(CC_ATTR_HOST_SEV_SNP);\narch/x86/kvm/svm/sev.c-3202-\n--\narch/x86/kvm/svm/sev.c=4995=struct page *snp_safe_alloc_page_node(int node, gfp_t gfp)\n--\narch/x86/kvm/svm/sev.c-4999-\narch/x86/kvm/svm/sev.c:5000:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/kvm/svm/sev.c-5001-\t\treturn alloc_pages_node(node, gfp | __GFP_ZERO, 0);\n--\narch/x86/kvm/svm/sev.c=5213=void sev_gmem_make_shared(kvm_pfn_t pfn, kvm_pfn_t nr_pages)\n--\narch/x86/kvm/svm/sev.c-5216-\narch/x86/kvm/svm/sev.c:5217:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/kvm/svm/sev.c-5218-\t\treturn;\n--\narch/x86/mm/mem_encrypt.c=102=void __init mem_encrypt_setup_arch(void)\n--\narch/x86/mm/mem_encrypt.c-110-\t */\narch/x86/mm/mem_encrypt.c:111:\tif (cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/mm/mem_encrypt.c-112-\t\tsnp_fixup_e820_tables();\n--\narch/x86/virt/svm/cmdline.c=19=static int __init init_sev_config(char *str)\n--\narch/x86/virt/svm/cmdline.c-31-\t\t\t\tsetup_clear_cpu_cap(X86_FEATURE_SEV_SNP);\narch/x86/virt/svm/cmdline.c:32:\t\t\t\tcc_platform_clear(CC_ATTR_HOST_SEV_SNP);\narch/x86/virt/svm/cmdline.c-33-\t\t\t\tcontinue;\n--\narch/x86/virt/svm/sev.c=147=static void mfd_reconfigure(void *arg)\narch/x86/virt/svm/sev.c-148-{\narch/x86/virt/svm/sev.c:149:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-150-\t\treturn;\n--\narch/x86/virt/svm/sev.c=158=static void snp_enable(void *arg)\n--\narch/x86/virt/svm/sev.c-161-\narch/x86/virt/svm/sev.c:162:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-163-\t\treturn;\n--\narch/x86/virt/svm/sev.c=260=static void clear_rmp(void)\n--\narch/x86/virt/svm/sev.c-264-\narch/x86/virt/svm/sev.c:265:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-266-\t\treturn;\n--\narch/x86/virt/svm/sev.c=618=static bool rmpopt_capable(void)\n--\narch/x86/virt/svm/sev.c-620-\treturn cpu_feature_enabled(X86_FEATURE_RMPOPT) \u0026\u0026\narch/x86/virt/svm/sev.c:621:\t       cc_platform_has(CC_ATTR_HOST_SEV_SNP);\narch/x86/virt/svm/sev.c-622-}\n--\narch/x86/virt/svm/sev.c=759=int __init snp_rmptable_init(void)\n--\narch/x86/virt/svm/sev.c-762-\narch/x86/virt/svm/sev.c:763:\tif (WARN_ON_ONCE(!cc_platform_has(CC_ATTR_HOST_SEV_SNP)))\narch/x86/virt/svm/sev.c-764-\t\treturn -ENOSYS;\n--\narch/x86/virt/svm/sev.c=968=static int __snp_lookup_rmpentry(u64 pfn, struct rmpentry *e, int *level)\n--\narch/x86/virt/svm/sev.c-972-\narch/x86/virt/svm/sev.c:973:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-974-\t\treturn -ENODEV;\n--\narch/x86/virt/svm/sev.c=1094=int psmash(u64 pfn)\n--\narch/x86/virt/svm/sev.c-1098-\narch/x86/virt/svm/sev.c:1099:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-1100-\t\treturn -ENODEV;\n--\narch/x86/virt/svm/sev.c=1203=static int rmpupdate(u64 pfn, struct rmp_state *state)\n--\narch/x86/virt/svm/sev.c-1207-\narch/x86/virt/svm/sev.c:1208:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-1209-\t\treturn -ENODEV;\n--\narch/x86/virt/svm/sev.c=1296=void kdump_sev_callback(void)\n--\narch/x86/virt/svm/sev.c-1301-\t */\narch/x86/virt/svm/sev.c:1302:\tif (cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-1303-\t\twbinvd();\n--\ndrivers/crypto/ccp/sev-dev.c=1508=static int __sev_snp_init_locked(int *error, unsigned int max_snp_asid)\n--\ndrivers/crypto/ccp/sev-dev.c-1516-\ndrivers/crypto/ccp/sev-dev.c:1517:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\ndrivers/crypto/ccp/sev-dev.c-1518-\t\treturn -ENODEV;\n--\ndrivers/crypto/ccp/sev-dev.c=2067=static int sev_get_api_version(void)\n--\ndrivers/crypto/ccp/sev-dev.c-2076-\t */\ndrivers/crypto/ccp/sev-dev.c:2077:\tif (cc_platform_has(CC_ATTR_HOST_SEV_SNP)) {\ndrivers/crypto/ccp/sev-dev.c-2078-\t\tret = snp_get_platform_data(sev, \u0026error);\n--\ndrivers/crypto/ccp/sev-dev.c=2977=u64 sev_get_snp_policy_bits(void)\n--\ndrivers/crypto/ccp/sev-dev.c-2982-\ndrivers/crypto/ccp/sev-dev.c:2983:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\ndrivers/crypto/ccp/sev-dev.c-2984-\t\treturn 0;\n--\ndrivers/iommu/amd/init.c=3395=static __init void iommu_snp_enable(void)\n--\ndrivers/iommu/amd/init.c-3397-#ifdef CONFIG_KVM_AMD_SEV\ndrivers/iommu/amd/init.c:3398:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\ndrivers/iommu/amd/init.c-3399-\t\treturn;\n--\ndrivers/iommu/amd/init.c-3441-disable_snp:\ndrivers/iommu/amd/init.c:3442:\tcc_platform_clear(CC_ATTR_HOST_SEV_SNP);\ndrivers/iommu/amd/init.c-3443-#endif\n--\ndrivers/iommu/amd/init.c=3567=static int __init iommu_go_to_state(enum iommu_init_state state)\n--\ndrivers/iommu/amd/init.c-3587-\t */\ndrivers/iommu/amd/init.c:3588:\tif (ret \u0026\u0026 cc_platform_has(CC_ATTR_HOST_SEV_SNP) \u0026\u0026\ndrivers/iommu/amd/init.c-3589-\t    !WARN_ON_ONCE(amd_iommu_snp_en))\ndrivers/iommu/amd/init.c:3590:\t\tcc_platform_clear(CC_ATTR_HOST_SEV_SNP);\ndrivers/iommu/amd/init.c-3591-\n--\ndrivers/iommu/amd/init.c=3694=void __init amd_iommu_detect(void)\n--\ndrivers/iommu/amd/init.c-3713-disable_snp:\ndrivers/iommu/amd/init.c:3714:\tif (cc_platform_has(CC_ATTR_HOST_SEV_SNP))\ndrivers/iommu/amd/init.c:3715:\t\tcc_platform_clear(CC_ATTR_HOST_SEV_SNP);\ndrivers/iommu/amd/init.c-3716-}\n--\ninclude/linux/cc_platform.h=22=enum cc_attr {\n--\ninclude/linux/cc_platform.h-92-\t/**\ninclude/linux/cc_platform.h:93:\t * @CC_ATTR_HOST_SEV_SNP: AMD SNP enabled on the host.\ninclude/linux/cc_platform.h-94-\t *\n--\ninclude/linux/cc_platform.h-97-\t */\ninclude/linux/cc_platform.h:98:\tCC_ATTR_HOST_SEV_SNP,\ninclude/linux/cc_platform.h-99-\n"
}

gemini-3.7-flash

null

null

							input: 13507
							output: 41
							thoughts: 59
						

**Investigating the Enabling Conditions**

Okay, so I need to figure out what precisely allows the system to utilize `CC_ATTR_HOST_SEV_SNP` and `X86_FEATURE_RMPOPT`. My intuition says it will be based on CPU flags or some other platform feature. To get a handle on this, I'll dive into the `arch/x86/kernel/cpu/amd.c` file. Specifically, I'll start around line 356, as that seems like a reasonable place for AMD-specific CPU feature initialization or detection logic, where the enabling conditions for these features would likely be defined. This should give me a good starting point to trace the dependencies.

{
  "File": "arch/x86/kernel/cpu/amd.c",
  "FirstLine": 350,
  "LineCount": 40
}

{
  "Contents": " 350:\t\t\t\tnode = nearby_node(apicid);\n 351:\t\t}\n 352:\t\tnuma_set_node(cpu, node);\n 353:\t#endif\n 354:\t}\n 355:\t\n 356:\tstatic void bsp_determine_snp(struct cpuinfo_x86 *c)\n 357:\t{\n 358:\t#ifdef CONFIG_ARCH_HAS_CC_PLATFORM\n 359:\t\tcc_vendor = CC_VENDOR_AMD;\n 360:\t\n 361:\t\tif (cpu_has(c, X86_FEATURE_SEV_SNP)) {\n 362:\t\t\t/*\n 363:\t\t\t * RMP table entry format is not architectural and is defined by the\n 364:\t\t\t * per-processor PPR. Restrict SNP support on the known CPU models\n 365:\t\t\t * for which the RMP table entry format is currently defined or for\n 366:\t\t\t * processors which support the architecturally defined RMPREAD\n 367:\t\t\t * instruction.\n 368:\t\t\t */\n 369:\t\t\tif (!cpu_has(c, X86_FEATURE_HYPERVISOR) \u0026\u0026\n 370:\t\t\t    (cpu_feature_enabled(X86_FEATURE_ZEN3) ||\n 371:\t\t\t     cpu_feature_enabled(X86_FEATURE_ZEN4) ||\n 372:\t\t\t     cpu_feature_enabled(X86_FEATURE_RMPREAD)) \u0026\u0026\n 373:\t\t\t    snp_probe_rmptable_info()) {\n 374:\t\t\t\tcc_platform_set(CC_ATTR_HOST_SEV_SNP);\n 375:\t\t\t} else {\n 376:\t\t\t\tsetup_clear_cpu_cap(X86_FEATURE_SEV_SNP);\n 377:\t\t\t\tcc_platform_clear(CC_ATTR_HOST_SEV_SNP);\n 378:\t\t\t}\n 379:\t\t}\n 380:\t#endif\n 381:\t}\n 382:\t\n 383:\t#define ZEN_MODEL_STEP_UCODE(fam, model, step, ucode) \\\n 384:\t\tX86_MATCH_VFM_STEPS(VFM_MAKE(X86_VENDOR_AMD, fam, model), \\\n 385:\t\t\t\t    step, step, ucode)\n 386:\t\n 387:\tstatic const struct x86_cpu_id amd_tsa_microcode[] = {\n 388:\t\tZEN_MODEL_STEP_UCODE(0x19, 0x01, 0x1, 0x0a0011d7),\n 389:\t\tZEN_MODEL_STEP_UCODE(0x19, 0x01, 0x2, 0x0a00123b),\n"
}

gemini-3.7-flash

null

null

							input: 14495
							output: 17
							thoughts: 571
						

**My Analysis of SEV-SNP and RMPOPT Initialization**

Okay, let's break this down. Line 369 immediately catches my eye: `if (!cpu_has(c, X86_FEATURE_HYPERVISOR) && ...`.  The check for the absence of the hypervisor feature is interesting. I know that `X86_FEATURE_HYPERVISOR` is set within a hypervisor environment like QEMU or GCE (CPUID leaf 0x1 ECX bit 31). So, because of this, `bsp_determine_snp` is correctly clearing `X86_FEATURE_SEV_SNP` and then calling `cc_platform_clear(CC_ATTR_HOST_SEV_SNP)` in virtualized environments. That makes perfect sense.

My next immediate thought is to confirm the obvious – does QEMU even *emulate* a SEV-SNP host? I know it doesn't. SEV-SNP needs bare metal AMD hardware with specific components and BIOS/MSR settings. No surprises there.

Alright, moving on, I see a new instruction in the code: `asm volatile(".byte 0xf2, 0x0f, 0x01, 0xfc" :: "a" (pa_start), "c" (op) : "memory", "cc");`. This is `RMPOPT`, which I know is an AMD Zen6 instruction (CPUID Fn8000_0025_EDX[0]).

I have to look at `rmpopt_capable()`. I see the check, and it's what I'd expect:

```c
static bool rmpopt_capable(void)
{
	return cpu_feature_enabled(X86_FEATURE_RMPOPT) &&
	       cc_platform_has(CC_ATTR_HOST_SEV_SNP);
}
```

Then I notice:

```c
void snp_rmpopt_all_physmem(void)
{
	if (!rmpopt_capable())
		return;
...
```

```c
void snp_setup_rmpopt(void)
{
...
	if (!rmpopt_capable())
		return;
...
```

Makes sense. These functions are guarded by `rmpopt_capable()` and so will not be invoked when running in a hypervisor.

Now, let's shift gears. I need to understand the larger context. I need to check `snp_prepare()`, `snp_shutdown()`, and `snp_rmptable_init()`.

I see in `snp_prepare()`:

```c
int snp_prepare(void)
{
...
	clear_rmp();
	cpu_hotplug_disable();
...
```

I'll use `grepper` to see where `snp_prepare()` is actually *called* from in the code. I need to understand the initialization sequence to see how all these pieces fit together.

{
  "Expression": "snp_prepare"
}

{
  "Output": "arch/x86/include/asm/sev.h=660=static inline void snp_leak_pages(u64 pfn, unsigned int pages)\n--\narch/x86/include/asm/sev.h-663-}\narch/x86/include/asm/sev.h:664:int snp_prepare(void);\narch/x86/include/asm/sev.h-665-void snp_rmpopt_all_physmem(void);\n--\narch/x86/include/asm/sev.h=683=static inline void snp_fixup_e820_tables(void) {}\narch/x86/include/asm/sev.h:684:static inline int snp_prepare(void) { return -ENODEV; }\narch/x86/include/asm/sev.h-685-static inline void snp_rmpopt_all_physmem(void) {}\n--\narch/x86/virt/svm/sev.c=521=static void clear_hsave_pa(void *arg)\n--\narch/x86/virt/svm/sev.c-525-\narch/x86/virt/svm/sev.c:526:int snp_prepare(void)\narch/x86/virt/svm/sev.c-527-{\n--\narch/x86/virt/svm/sev.c-567-}\narch/x86/virt/svm/sev.c:568:EXPORT_SYMBOL_FOR_MODULES(snp_prepare, \"ccp\");\narch/x86/virt/svm/sev.c-569-\n--\narch/x86/virt/svm/sev.c=759=int __init snp_rmptable_init(void)\n--\narch/x86/virt/svm/sev.c-773-\t * On a kexec boot SNP may already be enabled (legacy firmware leaves\narch/x86/virt/svm/sev.c:774:\t * SnpEn set across shutdown), in which case snp_prepare() bails without\narch/x86/virt/svm/sev.c-775-\t * disabling CPU hotplug, so disable it here.\n--\ndrivers/crypto/ccp/sev-dev.c=1508=static int __sev_snp_init_locked(int *error, unsigned int max_snp_asid)\n--\ndrivers/crypto/ccp/sev-dev.c-1530-\ndrivers/crypto/ccp/sev-dev.c:1531:\trc = snp_prepare();\ndrivers/crypto/ccp/sev-dev.c-1532-\tif (rc)\n"
}

gemini-3.7-flash

null

null

							input: 16432
							output: 17
							thoughts: 89
						

Here's my thinking process:

**Diving into the SEV-SNP Driver**

Okay, so `snp_prepare()` is apparently only called within `drivers/crypto/ccp/sev-dev.c`, specifically in `__sev_snp_init_locked()`. That's good, it narrows down where I need to focus. Now, let's see, it looks like it does some quick checks at the beginning:

```c
	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
		return -ENODEV;
```

This makes sure the host actually supports SEV-SNP before doing anything else. Standard stuff.

Now, I need to understand the lifecycle of this thing better. I've got to find out where `snp_shutdown()` is called from, since it's logical that there should be a corresponding shutdown function. Let's fire up `grepper` and see where that function is used.

{
  "Expression": "snp_shutdown"
}

{
  "Output": "arch/x86/include/asm/sev.h=666=void snp_setup_rmpopt(void);\narch/x86/include/asm/sev.h:667:void snp_shutdown(void);\narch/x86/include/asm/sev.h-668-#else\n--\narch/x86/include/asm/sev.h=686=static inline void snp_setup_rmpopt(void) {}\narch/x86/include/asm/sev.h:687:static inline void snp_shutdown(void) {}\narch/x86/include/asm/sev.h-688-#endif\n--\narch/x86/virt/svm/sev.c=526=int snp_prepare(void)\n--\narch/x86/virt/svm/sev.c-541-\t * No CPU may come online without SnpEn while SNP is active; disable\narch/x86/virt/svm/sev.c:542:\t * hotplug here and re-enable it in snp_shutdown().\narch/x86/virt/svm/sev.c-543-\t */\n--\narch/x86/virt/svm/sev.c=570=static void rmpopt_disable(void)\n--\narch/x86/virt/svm/sev.c-595-\narch/x86/virt/svm/sev.c:596:void snp_shutdown(void)\narch/x86/virt/svm/sev.c-597-{\n--\narch/x86/virt/svm/sev.c-615-}\narch/x86/virt/svm/sev.c:616:EXPORT_SYMBOL_FOR_MODULES(snp_shutdown, \"ccp\");\narch/x86/virt/svm/sev.c-617-\n--\narch/x86/virt/svm/sev.c=689=void snp_setup_rmpopt(void)\n--\narch/x86/virt/svm/sev.c-700-\t * On re-initialization after a legacy SNP shutdown (SNP_SHUTDOWN_EX\narch/x86/virt/svm/sev.c:701:\t * with x86_snp_shutdown=0), snp_shutdown() and thus rmpopt_disable() are\narch/x86/virt/svm/sev.c-702-\t * skipped, so the workqueue, delayed work and per-CPU RMPOPT_BASE MSRs\n--\ndrivers/crypto/ccp/sev-dev.c=130=static void __sev_firmware_shutdown(struct sev_device *sev, bool panic);\ndrivers/crypto/ccp/sev-dev.c-131-\ndrivers/crypto/ccp/sev-dev.c:132:static int snp_shutdown_on_panic(struct notifier_block *nb,\ndrivers/crypto/ccp/sev-dev.c-133-\t\t\t\t unsigned long reason, void *arg);\n--\ndrivers/crypto/ccp/sev-dev.c=135=static struct notifier_block snp_panic_notifier = {\ndrivers/crypto/ccp/sev-dev.c:136:\t.notifier_call = snp_shutdown_on_panic,\ndrivers/crypto/ccp/sev-dev.c-137-};\n--\ndrivers/crypto/ccp/sev-dev.c=203=static int sev_cmd_buffer_len(int cmd)\n--\ndrivers/crypto/ccp/sev-dev.c-207-\tcase SEV_CMD_INIT_EX:                   return sizeof(struct sev_data_init_ex);\ndrivers/crypto/ccp/sev-dev.c:208:\tcase SEV_CMD_SNP_SHUTDOWN_EX:\t\treturn sizeof(struct sev_data_snp_shutdown_ex);\ndrivers/crypto/ccp/sev-dev.c-209-\tcase SEV_CMD_SNP_INIT_EX:\t\treturn sizeof(struct sev_data_snp_init_ex);\n--\ndrivers/crypto/ccp/sev-dev.c=2136=static int sev_update_firmware(struct device *dev)\n--\ndrivers/crypto/ccp/sev-dev.c-2190-\ndrivers/crypto/ccp/sev-dev.c:2191:static int __sev_snp_shutdown_locked(int *error, bool panic)\ndrivers/crypto/ccp/sev-dev.c-2192-{\n--\ndrivers/crypto/ccp/sev-dev.c-2194-\tstruct sev_device *sev;\ndrivers/crypto/ccp/sev-dev.c:2195:\tstruct sev_data_snp_shutdown_ex data;\ndrivers/crypto/ccp/sev-dev.c-2196-\tint ret;\n--\ndrivers/crypto/ccp/sev-dev.c-2207-\tdata.len = sizeof(data);\ndrivers/crypto/ccp/sev-dev.c:2208:\tdata.iommu_snp_shutdown = 1;\ndrivers/crypto/ccp/sev-dev.c-2209-\tif (sev-\u003esnp_feat_info_0.ecx \u0026 SNP_X86_SHUTDOWN_SUPPORTED)\ndrivers/crypto/ccp/sev-dev.c:2210:\t\tdata.x86_snp_shutdown = 1;\ndrivers/crypto/ccp/sev-dev.c-2211-\n--\ndrivers/crypto/ccp/sev-dev.c-2243-\ndrivers/crypto/ccp/sev-dev.c:2244:\tif (data.x86_snp_shutdown) {\ndrivers/crypto/ccp/sev-dev.c-2245-\t\tif (!panic)\ndrivers/crypto/ccp/sev-dev.c:2246:\t\t\tsnp_shutdown();\ndrivers/crypto/ccp/sev-dev.c-2247-\t\tsnp_hv_fixed_pages_state_update(sev, ALLOCATED);\n--\ndrivers/crypto/ccp/sev-dev.c-2273-\t/*\ndrivers/crypto/ccp/sev-dev.c:2274:\t * __sev_snp_shutdown_locked() deadlocks when it tries to unregister\ndrivers/crypto/ccp/sev-dev.c-2275-\t * itself during panic as the panic notifier is called with RCU read\n--\ndrivers/crypto/ccp/sev-dev.c=2905=static void __sev_firmware_shutdown(struct sev_device *sev, bool panic)\n--\ndrivers/crypto/ccp/sev-dev.c-2936-\ndrivers/crypto/ccp/sev-dev.c:2937:\t__sev_snp_shutdown_locked(\u0026error, panic);\ndrivers/crypto/ccp/sev-dev.c-2938-}\n--\ndrivers/crypto/ccp/sev-dev.c=3014=void sev_dev_destroy(struct psp_device *psp)\n--\ndrivers/crypto/ccp/sev-dev.c-3028-\ndrivers/crypto/ccp/sev-dev.c:3029:static int snp_shutdown_on_panic(struct notifier_block *nb,\ndrivers/crypto/ccp/sev-dev.c-3030-\t\t\t\t unsigned long reason, void *arg)\n--\ninclude/linux/psp-sev.h=822=struct sev_data_range_list {\n--\ninclude/linux/psp-sev.h-828-/**\ninclude/linux/psp-sev.h:829: * struct sev_data_snp_shutdown_ex - SNP_SHUTDOWN_EX structure\ninclude/linux/psp-sev.h-830- *\ninclude/linux/psp-sev.h-831- * @len: length of the command buffer read by the PSP\ninclude/linux/psp-sev.h:832: * @iommu_snp_shutdown: Disable enforcement of SNP in the IOMMU\ninclude/linux/psp-sev.h:833: * @x86_snp_shutdown: Disable SNP on all cores\ninclude/linux/psp-sev.h-834- * @rsvd1: reserved\ninclude/linux/psp-sev.h-835- */\ninclude/linux/psp-sev.h:836:struct sev_data_snp_shutdown_ex {\ninclude/linux/psp-sev.h-837-\tu32 len;\ninclude/linux/psp-sev.h:838:\tu32 iommu_snp_shutdown:1;\ninclude/linux/psp-sev.h:839:\tu32 x86_snp_shutdown:1;\ninclude/linux/psp-sev.h-840-\tu32 rsvd1:30;\n"
}

gemini-3.7-flash

null

null

							input: 18948
							output: 17
							thoughts: 480
						

**Analyzing the SEV-SNP RMP Table Initialization**

Okay, let's dive into this `snp_rmptable_init()` function. The very first thing that jumps out is that it's gated behind `cc_platform_has(CC_ATTR_HOST_SEV_SNP)`. And, it seems like *everything* in the changes is guarded by that or `X86_FEATURE_RMPOPT`, which is a Zen6 CPU feature. My immediate concern is, are there any code paths introduced by this that *could* potentially be reached without the SEV-SNP feature? It's easy to make assumptions, but the devil's in the details, so let's verify.

I need to meticulously review each modified file. The first few (`arch/x86/include/...`) seem straightforward: definitions for the feature flag, MSRs, and function declarations. Nothing that jumps out as an issue there.

Now, `arch/x86/kernel/cpu/scattered.c` just adds the `X86_FEATURE_RMPOPT` bit to the `cpuid_bits` table. That's fine.

But `arch/x86/kvm/svm/sev.c` is where it gets interesting. I see `sev_vm_destroy()` calls `snp_rmpopt_all_physmem()`. *That's* the trigger, because `snp_rmpopt_all_physmem()` is the function we are initializing in the initial check. So, the question becomes: can `sev->snp_context` (within the `sev_vm_destroy()` context) be non-NULL without SEV-SNP host hardware? *That's* the critical piece of the puzzle. I need to trace back where `sev->snp_context` is set to ensure we are not creating an out-of-bounds issue.

{
  "Expression": "snp_context"
}

{
  "Output": "arch/x86/kvm/svm/sev.c=2216=int sev_dev_get_attr(u32 group, u64 attr, u64 *val)\n--\narch/x86/kvm/svm/sev.c-2243- */\narch/x86/kvm/svm/sev.c:2244:static void *snp_context_create(struct kvm *kvm, struct kvm_sev_cmd *argp)\narch/x86/kvm/svm/sev.c-2245-{\n--\narch/x86/kvm/svm/sev.c=2267=static int snp_bind_asid(struct kvm *kvm, int *error)\n--\narch/x86/kvm/svm/sev.c-2271-\narch/x86/kvm/svm/sev.c:2272:\tdata.gctx_paddr = __psp_pa(sev-\u003esnp_context);\narch/x86/kvm/svm/sev.c-2273-\tdata.asid = sev_get_asid(kvm);\n--\narch/x86/kvm/svm/sev.c=2277=static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)\n--\narch/x86/kvm/svm/sev.c-2290-\t/* Don't allow userspace to allocate memory for more than 1 SNP context. */\narch/x86/kvm/svm/sev.c:2291:\tif (sev-\u003esnp_context)\narch/x86/kvm/svm/sev.c-2292-\t\treturn -EINVAL;\n--\narch/x86/kvm/svm/sev.c-2310-\narch/x86/kvm/svm/sev.c:2311:\tsev-\u003esnp_context = snp_context_create(kvm, argp);\narch/x86/kvm/svm/sev.c:2312:\tif (!sev-\u003esnp_context)\narch/x86/kvm/svm/sev.c-2313-\t\treturn -ENOTTY;\narch/x86/kvm/svm/sev.c-2314-\narch/x86/kvm/svm/sev.c:2315:\tstart.gctx_paddr = __psp_pa(sev-\u003esnp_context);\narch/x86/kvm/svm/sev.c-2316-\tstart.policy = params.policy;\n--\narch/x86/kvm/svm/sev.c=2349=static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,\n--\narch/x86/kvm/svm/sev.c-2381-\narch/x86/kvm/svm/sev.c:2382:\tfw_args.gctx_paddr = __psp_pa(sev-\u003esnp_context);\narch/x86/kvm/svm/sev.c-2383-\tfw_args.address = __sme_set(pfn_to_hpa(pfn));\n--\narch/x86/kvm/svm/sev.c=2421=static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)\n--\narch/x86/kvm/svm/sev.c-2429-\narch/x86/kvm/svm/sev.c:2430:\tif (!sev_snp_guest(kvm) || !sev-\u003esnp_context)\narch/x86/kvm/svm/sev.c-2431-\t\treturn -EINVAL;\n--\narch/x86/kvm/svm/sev.c=2505=static int snp_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)\n--\narch/x86/kvm/svm/sev.c-2519-\narch/x86/kvm/svm/sev.c:2520:\tdata.gctx_paddr = __psp_pa(sev-\u003esnp_context);\narch/x86/kvm/svm/sev.c-2521-\tdata.page_type = SNP_PAGE_TYPE_VMSA;\n--\narch/x86/kvm/svm/sev.c=2562=static int snp_launch_finish(struct kvm *kvm, struct kvm_sev_cmd *argp)\n--\narch/x86/kvm/svm/sev.c-2572-\narch/x86/kvm/svm/sev.c:2573:\tif (!sev-\u003esnp_context)\narch/x86/kvm/svm/sev.c-2574-\t\treturn -EINVAL;\n--\narch/x86/kvm/svm/sev.c-2615-\tmemcpy(data-\u003ehost_data, params.host_data, KVM_SEV_SNP_FINISH_DATA_SIZE);\narch/x86/kvm/svm/sev.c:2616:\tdata-\u003egctx_paddr = __psp_pa(sev-\u003esnp_context);\narch/x86/kvm/svm/sev.c-2617-\tret = sev_issue_cmd(kvm, SEV_CMD_SNP_LAUNCH_FINISH, data, \u0026argp-\u003eerror);\n--\narch/x86/kvm/svm/sev.c=2930=static int snp_decommission_context(struct kvm *kvm)\n--\narch/x86/kvm/svm/sev.c-2936-\t/* If context is not created then do nothing */\narch/x86/kvm/svm/sev.c:2937:\tif (!sev-\u003esnp_context)\narch/x86/kvm/svm/sev.c-2938-\t\treturn 0;\n--\narch/x86/kvm/svm/sev.c-2940-\t/* Do the decommision, which will unbind the ASID from the SNP context */\narch/x86/kvm/svm/sev.c:2941:\tdata.address = __sme_pa(sev-\u003esnp_context);\narch/x86/kvm/svm/sev.c-2942-\tdown_write(\u0026sev_deactivate_lock);\n--\narch/x86/kvm/svm/sev.c-2948-\narch/x86/kvm/svm/sev.c:2949:\tsnp_free_firmware_page(sev-\u003esnp_context);\narch/x86/kvm/svm/sev.c:2950:\tsev-\u003esnp_context = NULL;\narch/x86/kvm/svm/sev.c-2951-\n--\narch/x86/kvm/svm/sev.c=4228=static int snp_handle_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_gpa)\n--\narch/x86/kvm/svm/sev.c-4243-\narch/x86/kvm/svm/sev.c:4244:\tdata.gctx_paddr = __psp_pa(sev-\u003esnp_context);\narch/x86/kvm/svm/sev.c-4245-\tdata.req_paddr = __psp_pa(sev-\u003eguest_req_buf);\n--\narch/x86/kvm/svm/sev.c=5326=struct vmcb_save_area *sev_decrypt_vmsa(struct kvm_vcpu *vcpu)\n--\narch/x86/kvm/svm/sev.c-5361-\narch/x86/kvm/svm/sev.c:5362:\t\tdbg.gctx_paddr = __psp_pa(sev-\u003esnp_context);\narch/x86/kvm/svm/sev.c-5363-\t\tdbg.src_addr = svm-\u003evmcb-\u003econtrol.vmsa_pa;\n--\narch/x86/kvm/svm/svm.h=99=struct kvm_sev_info {\n--\narch/x86/kvm/svm/svm.h-117-\tatomic_t migration_in_progress;\narch/x86/kvm/svm/svm.h:118:\tvoid *snp_context;      /* SNP guest context page */\narch/x86/kvm/svm/svm.h-119-\tvoid *guest_req_buf;    /* Bounce buffer for SNP Guest Request input */\n"
}

gemini-3.7-flash

null

null

							input: 22063
							output: 43
							thoughts: 24
						

Okay, here's my interpretation of that thought process, assuming I'm deep in my code and thinking about a specific function:

**Analyzing the `snp_context_create` Function**

Alright, time to get my head around `snp_context_create`. First things first, I need to understand what this function does and how it works. Let me just pull up its definition and start reading the code. This will allow me to grasp the intention of the code. I'll need to step through this slowly and carefully to make sure I don't miss anything.

{
  "File": "arch/x86/kvm/svm/sev.c",
  "FirstLine": 2240,
  "LineCount": 35
}

{
  "Contents": "2240:\t * associated with the guest that the firmware tracks to implement SEV\n2241:\t * and SNP features. The firmware stores the guest context in hypervisor\n2242:\t * provide page via the SNP_GCTX_CREATE command.\n2243:\t */\n2244:\tstatic void *snp_context_create(struct kvm *kvm, struct kvm_sev_cmd *argp)\n2245:\t{\n2246:\t\tstruct sev_data_snp_addr data = {};\n2247:\t\tvoid *context;\n2248:\t\tint rc;\n2249:\t\n2250:\t\t/* Allocate memory for context page */\n2251:\t\tcontext = snp_alloc_firmware_page(GFP_KERNEL_ACCOUNT);\n2252:\t\tif (!context)\n2253:\t\t\treturn NULL;\n2254:\t\n2255:\t\tdata.address = __psp_pa(context);\n2256:\t\trc = __sev_issue_cmd(argp-\u003esev_fd, SEV_CMD_SNP_GCTX_CREATE, \u0026data, \u0026argp-\u003eerror);\n2257:\t\tif (rc) {\n2258:\t\t\tpr_warn(\"Failed to create SEV-SNP context, rc %d fw_error %d\",\n2259:\t\t\t\trc, argp-\u003eerror);\n2260:\t\t\tsnp_free_firmware_page(context);\n2261:\t\t\treturn NULL;\n2262:\t\t}\n2263:\t\n2264:\t\treturn context;\n2265:\t}\n2266:\t\n2267:\tstatic int snp_bind_asid(struct kvm *kvm, int *error)\n2268:\t{\n2269:\t\tstruct kvm_sev_info *sev = to_kvm_sev_info(kvm);\n2270:\t\tstruct sev_data_snp_activate data = {0};\n2271:\t\n2272:\t\tdata.gctx_paddr = __psp_pa(sev-\u003esnp_context);\n2273:\t\tdata.asid = sev_get_asid(kvm);\n2274:\t\treturn sev_issue_cmd(kvm, SEV_CMD_SNP_ACTIVATE, \u0026data, error);\n"
}

gemini-3.7-flash

null

null

							input: 22844
							output: 22
							thoughts: 13
						

Okay, here's my interpretation of "And look at `snp_alloc_firmware_page`," summarized as a first-person thought process, keeping in mind my expertise:

**Diving Deep into `snp_alloc_firmware_page`**

Alright, let's zero in on `snp_alloc_firmware_page`. My first thought? "Why are we looking at this specific function *now*?" Context is everything. Is this part of a debugging session? Are we tracking down a memory allocation issue? Or are we reviewing the security implications? Knowing the "why" is crucial for a productive analysis.

Regardless, I'm already mentally running through my mental checklist: memory management strategies, potential race conditions within this code, and interactions with the Secure Nested Paging (SNP) implementation. I'm immediately interested in:

*   **Error handling:** Is it robust? Does it check return values properly, especially in a potentially sensitive area like firmware page allocation? I want to see if this is all guarded.
*   **Contiguity:** Is this memory allocation contiguous, or is it scattered? This can dramatically affect performance and security implications, potentially impacting how the guest virtual machine (VM) behaves.
*   **Privilege Levels:** What level of privilege is this function operating under? Is it running in the hypervisor, or the guest? The answer will provide insight into the attack surface.
*   **Concurrency:** Any locks? Any potential for concurrent access and race conditions? This is critical in a multi-threaded or multi-VM environment.
*   **Interaction with SNP:** How exactly does this function interface with the SNP framework? Is it correctly setting the appropriate flags, handling attestation, and ensuring the confidentiality and integrity of the firmware page? This is the core area of investigation.

Now, my mind is already starting to piece together a rough understanding of the function's scope. Ultimately, the next step is going to be analyzing the actual code itself. Let's see how well my initial assumptions hold up.

{
  "Expression": "snp_alloc_firmware_page"
}

{
  "Output": "arch/x86/kvm/svm/sev.c=456=static int snp_guest_req_init(struct kvm *kvm)\n--\narch/x86/kvm/svm/sev.c-464-\narch/x86/kvm/svm/sev.c:465:\tsev-\u003eguest_resp_buf = snp_alloc_firmware_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);\narch/x86/kvm/svm/sev.c-466-\tif (!sev-\u003eguest_resp_buf) {\n--\narch/x86/kvm/svm/sev.c=2244=static void *snp_context_create(struct kvm *kvm, struct kvm_sev_cmd *argp)\n--\narch/x86/kvm/svm/sev.c-2250-\t/* Allocate memory for context page */\narch/x86/kvm/svm/sev.c:2251:\tcontext = snp_alloc_firmware_page(GFP_KERNEL_ACCOUNT);\narch/x86/kvm/svm/sev.c-2252-\tif (!context)\n--\narch/x86/kvm/svm/sev.c=3064=static bool is_sev_snp_initialized(void)\n--\narch/x86/kvm/svm/sev.c-3070-\narch/x86/kvm/svm/sev.c:3071:\tstatus = snp_alloc_firmware_page(GFP_KERNEL | __GFP_ZERO);\narch/x86/kvm/svm/sev.c-3072-\tif (!status)\n--\narch/x86/kvm/svm/sev.c=5326=struct vmcb_save_area *sev_decrypt_vmsa(struct kvm_vcpu *vcpu)\n--\narch/x86/kvm/svm/sev.c-5357-\narch/x86/kvm/svm/sev.c:5358:\t\tvmsa = snp_alloc_firmware_page(__GFP_ZERO);\narch/x86/kvm/svm/sev.c-5359-\t\tif (!vmsa)\n--\ndrivers/crypto/ccp/sev-dev-tio.c=741=int sev_tio_dev_create(struct tsm_dsm_tio *dev_data, u16 device_id,\n--\ndrivers/crypto/ccp/sev-dev-tio.c-757-\ndrivers/crypto/ccp/sev-dev-tio.c:758:\tdata_pg = snp_alloc_firmware_page(GFP_KERNEL_ACCOUNT);\ndrivers/crypto/ccp/sev-dev-tio.c-759-\tif (!data_pg) {\n--\ndrivers/crypto/ccp/sev-dev.c=417=static int rmp_mark_pages_firmware(unsigned long paddr, unsigned int npages, bool locked)\n--\ndrivers/crypto/ccp/sev-dev.c-440-\ndrivers/crypto/ccp/sev-dev.c:441:static struct page *__snp_alloc_firmware_pages(gfp_t gfp_mask, int order, bool locked)\ndrivers/crypto/ccp/sev-dev.c-442-{\n--\ndrivers/crypto/ccp/sev-dev.c-465-\ndrivers/crypto/ccp/sev-dev.c:466:void *snp_alloc_firmware_page(gfp_t gfp_mask)\ndrivers/crypto/ccp/sev-dev.c-467-{\n--\ndrivers/crypto/ccp/sev-dev.c-469-\ndrivers/crypto/ccp/sev-dev.c:470:\tpage = __snp_alloc_firmware_pages(gfp_mask, 0, false);\ndrivers/crypto/ccp/sev-dev.c-471-\n--\ndrivers/crypto/ccp/sev-dev.c-473-}\ndrivers/crypto/ccp/sev-dev.c:474:EXPORT_SYMBOL_GPL(snp_alloc_firmware_page);\ndrivers/crypto/ccp/sev-dev.c-475-\n--\ndrivers/crypto/ccp/sev-dev.c=501=static void *sev_fw_alloc(unsigned long len)\n--\ndrivers/crypto/ccp/sev-dev.c-504-\ndrivers/crypto/ccp/sev-dev.c:505:\tpage = __snp_alloc_firmware_pages(GFP_KERNEL, get_order(len), true);\ndrivers/crypto/ccp/sev-dev.c-506-\tif (!page)\n--\ndrivers/crypto/ccp/sev-dev.c=1353=static int snp_verify_mitigation(u16 command, u64 vector,\n--\ndrivers/crypto/ccp/sev-dev.c-1360-\ndrivers/crypto/ccp/sev-dev.c:1361:\tmit_dst = snp_alloc_firmware_page(GFP_KERNEL | __GFP_ZERO);\ndrivers/crypto/ccp/sev-dev.c-1362-\tif (!mit_dst)\n--\ndrivers/crypto/ccp/sev-dev.c=1508=static int __sev_snp_init_locked(int *error, unsigned int max_snp_asid)\n--\ndrivers/crypto/ccp/sev-dev.c-1649-\t\t * unlikely) but will cause a deadlock.\ndrivers/crypto/ccp/sev-dev.c:1650:\t\t * Instead of exporting __snp_alloc_firmware_pages(), allocate a page\ndrivers/crypto/ccp/sev-dev.c-1651-\t\t * for this one call here.\ndrivers/crypto/ccp/sev-dev.c-1652-\t\t */\ndrivers/crypto/ccp/sev-dev.c:1653:\t\tpage = __snp_alloc_firmware_pages(GFP_KERNEL_ACCOUNT | __GFP_ZERO,\ndrivers/crypto/ccp/sev-dev.c-1654-\t\t\t\t\t\t  0, true);\n--\ninclude/linux/psp-sev.h=1131=void *psp_copy_user_blob(u64 uaddr, u32 len);\ninclude/linux/psp-sev.h:1132:void *snp_alloc_firmware_page(gfp_t mask);\ninclude/linux/psp-sev.h-1133-int snp_reclaim_pages(unsigned long paddr, unsigned int npages, bool locked);\n--\ninclude/linux/psp-sev.h=1164=static inline void *psp_copy_user_blob(u64 __user uaddr, u32 len) { return ERR_PTR(-EINVAL); }\ninclude/linux/psp-sev.h-1165-\ninclude/linux/psp-sev.h:1166:static inline void *snp_alloc_firmware_page(gfp_t mask)\ninclude/linux/psp-sev.h-1167-{\n"
}

gemini-3.7-flash

null

null

							input: 25081
							output: 40
							thoughts: 58
						

**Analyzing the Firmware Page Allocation Function**

Okay, let's dive in. I need to understand how firmware pages are being allocated within this crypto context. My starting point is `snp_alloc_firmware_page`, which I suspect is a wrapper function. Let's trace it down, and it looks like it calls `__snp_alloc_firmware_pages`. That's a good lead. Now I should check the implementation of `__snp_alloc_firmware_pages` directly. A quick file system search and I see it's defined within `drivers/crypto/ccp/sev-dev.c`. Alright, time to open that file and get a handle on the specifics of this allocation process. I need to know the memory regions being used, the allocation strategies in place, and what error checking is being performed. This is where the real work begins.

{
  "File": "drivers/crypto/ccp/sev-dev.c",
  "FirstLine": 440,
  "LineCount": 35
}

{
  "Contents": " 440:\t\n 441:\tstatic struct page *__snp_alloc_firmware_pages(gfp_t gfp_mask, int order, bool locked)\n 442:\t{\n 443:\t\tunsigned long npages = 1ul \u003c\u003c order, paddr;\n 444:\t\tstruct sev_device *sev;\n 445:\t\tstruct page *page;\n 446:\t\n 447:\t\tif (!psp_master || !psp_master-\u003esev_data)\n 448:\t\t\treturn NULL;\n 449:\t\n 450:\t\tpage = alloc_pages(gfp_mask, order);\n 451:\t\tif (!page)\n 452:\t\t\treturn NULL;\n 453:\t\n 454:\t\t/* If SEV-SNP is initialized then add the page in RMP table. */\n 455:\t\tsev = psp_master-\u003esev_data;\n 456:\t\tif (!sev-\u003esnp_initialized)\n 457:\t\t\treturn page;\n 458:\t\n 459:\t\tpaddr = __pa((unsigned long)page_address(page));\n 460:\t\tif (rmp_mark_pages_firmware(paddr, npages, locked))\n 461:\t\t\treturn NULL;\n 462:\t\n 463:\t\treturn page;\n 464:\t}\n 465:\t\n 466:\tvoid *snp_alloc_firmware_page(gfp_t gfp_mask)\n 467:\t{\n 468:\t\tstruct page *page;\n 469:\t\n 470:\t\tpage = __snp_alloc_firmware_pages(gfp_mask, 0, false);\n 471:\t\n 472:\t\treturn page ? page_address(page) : NULL;\n 473:\t}\n 474:\tEXPORT_SYMBOL_GPL(snp_alloc_firmware_page);\n"
}

gemini-3.7-flash

null

null

							input: 25874
							output: 135
							thoughts: 1350
						

**Analysis of Code Changes and Fuzzing Suitability**

Okay, here's what I've determined after reviewing the code modifications. My initial focus was on understanding the interaction with the PSP device, `/dev/sev`, via the `SEV_CMD_SNP_GCTX_CREATE` ioctl. This, as we know, interacts with the AMD Platform Security Processor, or PSP, which is a hardware component present on AMD Zen CPUs. The call to `__sev_issue_cmd()` is the key.

I then dug into how the code determines SEV-SNP host capabilities.  `bsp_determine_snp()` in `amd.c` explicitly disables `CC_ATTR_HOST_SEV_SNP` if the hypervisor feature, `X86_FEATURE_HYPERVISOR`, is detected. This is a very important point! Furthermore, to enable RMPOPT, we *require* both `CC_ATTR_HOST_SEV_SNP` *and* the Zen6 instruction set feature, `X86_FEATURE_RMPOPT`.  RMPOPT is specific to AMD Zen6 and SEV-SNP.

Now, let's circle back to the criteria for *not* fuzzing (negative criteria) as per the prompt.  Specifically, the category "Structurally unreachable hardware."  What does SEV-SNP host support *require*? Let's break it down:

1.  A bare metal AMD Zen3/Zen4/Zen5/Zen6 CPU.
2.  An AMD PSP (or CCP) *physical* hardware device.
3.  RMPOPT is tied to Zen6 with the relevant CPU feature.
4.  In virtualized environments (QEMU/KVM, GCE), which is the standard fuzzing environment, `X86_FEATURE_HYPERVISOR` is always set on the amd64 guest kernel. This causes `bsp_determine_snp()` to clear `cc_flags.host_sev_snp` and `X86_FEATURE_SEV_SNP`.

Without the `CC_ATTR_HOST_SEV_SNP` set, the relevant code paths are *never* reached. `snp_rmpopt_all_physmem()`, `snp_setup_rmpopt()`, and calls in `snp_prepare()` / `snp_shutdown()` become no-ops or early returns. `snp_rmptable_init()` just returns an error. `snp_probe_rmptable_info()` is either short-circuited or does nothing. The changes to `scattered.c` are simply adding the cpuid bit to a table which isn't used due to lack of the hardware configuration.

I re-examined all the modified lines of code.  We're looking at:

1.  CPU feature definitions.
2.  MSR index definitions.
3.  SEV declarations and stub implementations.
4.  CPUID feature table.
5.  Calls in `sev_vm_destroy()` and support logic like `rmpopt_capable()`, `snp_setup_rmpopt()`, etc.
6. A call to `snp_setup_rmpopt()` in `__sev_snp_init_locked()`.

The important point is that *all* these changes are within the AMD SEV-SNP host support logic, which includes the RMPOPT feature that is specific to AMD Zen6 bare-metal processors. In the vast majority of fuzzing environments - specifically QEMU/KVM, which the documentation specifies is the standard setup - `CC_ATTR_HOST_SEV_SNP` is never set. This is because we don't have AMD PSP hardware and due to the `X86_FEATURE_HYPERVISOR` check. This makes the RMPOPT mechanism and the entire SEV-SNP host lifecycle *structurally unreachable* during standard fuzzing.  This means these areas are not worth fuzzing.

Therefore:

*   `WorthFuzzing: false`
*   `EnableConfigs: []`
*   `FocusSymbols: []`

I'm confident in these findings.

{
  "EnableConfigs": [],
  "FocusSymbols": [],
  "Reasoning": "The patch series adds support for AMD SEV-SNP RMPOPT (RMP Optimization) instructions and management for AMD Zen6+ host processors. These code paths require physical AMD hardware supporting SEV-SNP host features and the AMD Platform Security Processor (PSP), and are disabled when running inside virtualized environments (X86_FEATURE_HYPERVISOR disables CC_ATTR_HOST_SEV_SNP during boot). Consequently, the modified code paths are structurally unreachable in standard virtualized fuzzing environments.",
  "WorthFuzzing": false
}

{
  "EnableConfigs": null,
  "FocusSymbols": [],
  "Reasoning": "The patch series adds support for AMD SEV-SNP RMPOPT (RMP Optimization) instructions and management for AMD Zen6+ host processors. These code paths require physical AMD hardware supporting SEV-SNP host features and the AMD Platform Security Processor (PSP), and are disabled when running inside virtualized environments (X86_FEATURE_HYPERVISOR disables CC_ATTR_HOST_SEV_SNP during boot). Consequently, the modified code paths are structurally unreachable in standard virtualized fuzzing environments.",
  "WorthFuzzing": false
}

{
  "WorthFuzzing": false
}

null