AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/09/18 15:57	flow	patch-triage	8m Args: null Results: { "EnableConfigs": null, "FocusSymbols": [], "KMSANReasoning": "", "NeedsKMSAN": false, "Reasoning": "The patch series adds support for the AMD RMPOPT CPU feature/instruction and manages RMP optimizations during AMD SEV-SNP host operations. These code paths are structurally unreachable in standard virtualized fuzzing environments (QEMU / GCE): SEV-SNP host support requires physical AMD hardware with Platform Security Processor (PSP/CCP) and firmware-configured RMP tables, and the kernel explicitly skips enabling SEV-SNP host capabilities (CC_ATTR_HOST_SEV_SNP) whenever running under a hypervisor (X86_FEATURE_HYPERVISOR). Furthermore, the RMPOPT CPU feature (CPUID 0x80000025) and instruction are not emulated by QEMU. Consequently, all modified functions and branches (including snp_enable_rmpopt, rmpopt_init, snp_prepare, snp_shutdown, and KVM SNP destruction hooks) cannot be reached or exercised during fuzzing.", "WorthFuzzing": false }
1/1	2026/09/18 15:57	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit bd08ef8c485e8913c723a962a2e3d049e8babdd2\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Fri Sep 18 15:57:25 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( 332+ 4) / Opteron, Athlon64 /\n #define X86_FEATURE_ZEN5\t\t( 332+ 5) /* CPU based on Zen5 microarchitecture /\n #define X86_FEATURE_ZEN6\t\t( 332+ 6) /* CPU based on Zen6 microarchitecture /\n-/ Free ( 332+ 7) /\n+#define X86_FEATURE_RMPOPT\t\t( 332+ 7) / Support for AMD RMPOPT instruction /\n #define X86_FEATURE_CONSTANT_TSC\t( 332+ 8) /* \"constant_tsc\" TSC ticks at a constant rate /\n / free: was #define X86_FEATURE_UP\t( 332+ 9) \"up\" SMP kernel running on UP /\n #define X86_FEATURE_ART\t\t\t( 332+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..fa81aa004e8bf 100644\n--- a/arch/x86/include/asm/sev.h\n+++ b/arch/x86/include/asm/sev.h\n@@ -662,6 +662,7 @@ 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_enable_rmpopt(void);\n void snp_shutdown(void);\n #else\n static inline bool snp_probe_rmptable_info(void) { return false; }\n@@ -680,6 +681,7 @@ 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_enable_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..4d5e30af1adea 100644\n--- a/arch/x86/kvm/svm/sev.c\n+++ b/arch/x86/kvm/svm/sev.c\n@@ -3032,6 +3032,8 @@ void sev_vm_destroy(struct kvm kvm)\n \t\t /\n \t\tif (snp_decommission_context(kvm))\n \t\t\treturn;\n+\n+\t\tsnp_enable_rmpopt();\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..13d9acb319aa1 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 +125,26 @@ 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 bool rmpopt_enabled;\n+\n+/\n+ * Delay, in milliseconds, before the RMP re-optimization pass runs after an SNP\n+ * guest is torn down, passed as the delay to mod_delayed_work(). This coalesces\n+ * a burst of teardowns into a single scan and gives each guest's pages time to\n+ * be converted back to the shared, hypervisor-owned state. The 10 second value\n+ * is a heuristic trading re-optimization latency against scanning too eagerly.\n+ /\n+#define RMPOPT_WORK_TIMEOUT\t(10 MSEC_PER_SEC)\n+\n static LIST_HEAD(snp_leaked_pages_list);\n static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);\n \n@@ -513,7 +534,6 @@ 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 +546,18 @@ 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@@ -548,15 +572,16 @@ 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-\n-unlock:\n-\tcpus_read_unlock();\n-\n-\treturn ret;\n+\treturn 0;\n }\n EXPORT_SYMBOL_FOR_MODULES(snp_prepare, \"ccp\");\n \n+static void rmpopt_disable(void)\n+{\n+\tif (rmpopt_wq)\n+\t\tcancel_delayed_work_sync(\u0026rmpopt_delayed_work);\n+}\n+\n void snp_shutdown(void)\n {\n \tu64 syscfg;\n@@ -565,11 +590,120 @@ 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) \u0026\u0026 rmpopt_enabled;\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+\t/ Supported by binutils 2.48+ /\n+\tasm volatile(\".byte 0xf2, 0x0f, 0x01, 0xfc\"\n+\t\t :: \"a\" (pa_start), \"c\" (op)\n+\t\t : \"memory\", \"cc\");\n+}\n+\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 * Warm up the RMPOPT cache on this pinned per-CPU worker with interrupts\n+\t * enabled, so the IRQ-disabled fan-out below only issues cache-hit RMPOPTs.\n+\t /\n+\trmpopt_scan_range(NULL);\n+\n+\ton_each_cpu_mask(cpu_primary_thread_mask, rmpopt_scan_range, NULL, true);\n+}\n+\n+static int __init rmpopt_init(void)\n+{\n+\tif (!cpu_feature_enabled(X86_FEATURE_RMPOPT))\n+\t\treturn 0;\n+\n+\trmpopt_wq = alloc_workqueue(\"rmpopt_wq\", WQ_PERCPU, 1);\n+\tif (!rmpopt_wq) {\n+\t\tpr_err(\"Failed to allocate RMPOPT workqueue\\n\");\n+\t\treturn 0;\n+\t}\n+\n+\tINIT_DELAYED_WORK(\u0026rmpopt_delayed_work, do_rmpopt_work);\n+\n+\t/ The optimization range is fixed at boot; compute it once. /\n+\trmpopt_pa_start = ALIGN_DOWN(PFN_PHYS(min_low_pfn), SZ_1G);\n+\trmpopt_pa_end = ALIGN(PFN_PHYS(max_pfn), SZ_1G);\n+\tif ((rmpopt_pa_end - rmpopt_pa_start) \u003e SZ_2T)\n+\t\trmpopt_pa_end = rmpopt_pa_start + SZ_2T;\n+\n+\trmpopt_enabled = true;\n+\n+\treturn 0;\n+}\n+device_initcall(rmpopt_init);\n+\n+void snp_enable_rmpopt(void)\n+{\n+\tu64 base;\n+\tint cpu;\n+\n+\tif (!rmpopt_capable())\n+\t\treturn;\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. The MSR\n+\t * can only be written after SNP is enabled, so this runs from the ccp\n+\t * SNP init path (and again on guest teardown) rather than an initcall.\n+\t \n+\t The loop below programs RMPOPT_BASE on all primary threads. RMPOPT_EN\n+\t * cannot be cleared while SNP is enabled, and CPU hotplug is disabled\n+\t * while SNP is active, so once programmed the MSRs stay set on all CPUs\n+\t * until SNP is disabled. A set RMPOPT_EN on the local CPU therefore\n+\t * means the programming has already been done, so skip it.\n+\t /\n+\trdmsrq(MSR_AMD64_RMPOPT_BASE, base);\n+\tif (!(base \u0026 MSR_AMD64_RMPOPT_ENABLE))\n+\t\tfor_each_cpu(cpu, cpu_primary_thread_mask)\n+\t\t\twrmsrq_on_cpu(cpu, MSR_AMD64_RMPOPT_BASE,\n+\t\t\t\t rmpopt_pa_start \| MSR_AMD64_RMPOPT_ENABLE);\n+\n+\tmod_delayed_work(rmpopt_wq, \u0026rmpopt_delayed_work,\n+\t\t\t msecs_to_jiffies(RMPOPT_WORK_TIMEOUT));\n+\n+\tpr_info_once(\"RMPOPT optimizations enabled\\n\");\n+}\n+EXPORT_SYMBOL_FOR_MODULES(snp_enable_rmpopt, \"ccp,kvm-amd\");\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 +711,8 @@ 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 +722,15 @@ 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 +828,31 @@ 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\tif (probe_segmented_rmptable_info())\n+\t\t\t\treturn true;\n+\n+\t\t\t/\n+\t\t\t Segmented RMP is enabled but misconfigured; RMPOPT is\n+\t\t\t * unusable, so drop the capability before it reaches the\n+\t\t\t * initcall.\n+\t\t\t /\n+\t\t\tsetup_clear_cpu_cap(X86_FEATURE_RMPOPT);\n+\t\t\treturn false;\n+\t\t}\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..5c996ab638959 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_enable_rmpopt();\n+\n \treturn 0;\n }\n \n" }
2/1	2026/09/18 15:57	agent	patch-evaluator	8m Model: core Args: null Results: { "EnableConfigs": null, "FocusSymbols": [], "Reasoning": "The patch series adds support for the AMD RMPOPT CPU feature/instruction and manages RMP optimizations during AMD SEV-SNP host operations. These code paths are structurally unreachable in standard virtualized fuzzing environments (QEMU / GCE): SEV-SNP host support requires physical AMD hardware with Platform Security Processor (PSP/CCP) and firmware-configured RMP tables, and the kernel explicitly skips enabling SEV-SNP host capabilities (CC_ATTR_HOST_SEV_SNP) whenever running under a hypervisor (X86_FEATURE_HYPERVISOR). Furthermore, the RMPOPT CPU feature (CPUID 0x80000025) and instruction are not emulated by QEMU. Consequently, all modified functions and branches (including snp_enable_rmpopt, rmpopt_init, snp_prepare, snp_shutdown, and KVM SNP destruction hooks) cannot be reached or exercised during fuzzing.", "WorthFuzzing": false } Instruction: 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. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit bd08ef8c485e8913c723a962a2e3d049e8babdd2 Author: syz-cluster <triage@syzkaller.com> Date: Fri Sep 18 15:57:25 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 ( 332+ 4) / Opteron, Athlon64 / #define X86_FEATURE_ZEN5 ( 332+ 5) /* CPU based on Zen5 microarchitecture / #define X86_FEATURE_ZEN6 ( 332+ 6) /* CPU based on Zen6 microarchitecture / -/ Free ( 332+ 7) / +#define X86_FEATURE_RMPOPT ( 332+ 7) / Support for AMD RMPOPT instruction / #define X86_FEATURE_CONSTANT_TSC ( 332+ 8) /* "constant_tsc" TSC ticks at a constant rate / / free: was #define X86_FEATURE_UP ( 332+ 9) "up" SMP kernel running on UP / #define X86_FEATURE_ART ( 332+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..fa81aa004e8bf 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -662,6 +662,7 @@ static inline void snp_leak_pages(u64 pfn, unsigned int pages) __snp_leak_pages(pfn, pages, true); } int snp_prepare(void); +void snp_enable_rmpopt(void); void snp_shutdown(void); #else static inline bool snp_probe_rmptable_info(void) { return false; } @@ -680,6 +681,7 @@ 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_enable_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..4d5e30af1adea 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -3032,6 +3032,8 @@ void sev_vm_destroy(struct kvm kvm) / if (snp_decommission_context(kvm)) return; + + snp_enable_rmpopt(); } 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..13d9acb319aa1 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 +125,26 @@ 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 bool rmpopt_enabled; + +/ + * Delay, in milliseconds, before the RMP re-optimization pass runs after an SNP + * guest is torn down, passed as the delay to mod_delayed_work(). 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. The 10 second value + * is a heuristic trading re-optimization latency against scanning too eagerly. + / +#define RMPOPT_WORK_TIMEOUT (10 MSEC_PER_SEC) + static LIST_HEAD(snp_leaked_pages_list); static DEFINE_SPINLOCK(snp_leaked_pages_list_lock); @@ -513,7 +534,6 @@ static void clear_hsave_pa(void arg) int snp_prepare(void) { - int ret; u64 val; / @@ -526,14 +546,18 @@ 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(); @@ -548,15 +572,16 @@ 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; - -unlock: - cpus_read_unlock(); - - return ret; + return 0; } EXPORT_SYMBOL_FOR_MODULES(snp_prepare, "ccp"); +static void rmpopt_disable(void) +{ + if (rmpopt_wq) + cancel_delayed_work_sync(&rmpopt_delayed_work); +} + void snp_shutdown(void) { u64 syscfg; @@ -565,11 +590,120 @@ 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_enabled; +} + +/ + * 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); + + / Supported by binutils 2.48+ / + asm volatile(".byte 0xf2, 0x0f, 0x01, 0xfc" + :: "a" (pa_start), "c" (op) + : "memory", "cc"); +} + +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) +{ + / + * Warm up the RMPOPT cache on this pinned per-CPU worker with interrupts + * enabled, so the IRQ-disabled fan-out below only issues cache-hit RMPOPTs. + / + rmpopt_scan_range(NULL); + + on_each_cpu_mask(cpu_primary_thread_mask, rmpopt_scan_range, NULL, true); +} + +static int __init rmpopt_init(void) +{ + if (!cpu_feature_enabled(X86_FEATURE_RMPOPT)) + return 0; + + rmpopt_wq = alloc_workqueue("rmpopt_wq", WQ_PERCPU, 1); + if (!rmpopt_wq) { + pr_err("Failed to allocate RMPOPT workqueue\n"); + return 0; + } + + INIT_DELAYED_WORK(&rmpopt_delayed_work, do_rmpopt_work); + + / The optimization range is fixed at boot; compute it once. / + rmpopt_pa_start = ALIGN_DOWN(PFN_PHYS(min_low_pfn), SZ_1G); + rmpopt_pa_end = ALIGN(PFN_PHYS(max_pfn), SZ_1G); + if ((rmpopt_pa_end - rmpopt_pa_start) > SZ_2T) + rmpopt_pa_end = rmpopt_pa_start + SZ_2T; + + rmpopt_enabled = true; + + return 0; +} +device_initcall(rmpopt_init); + +void snp_enable_rmpopt(void) +{ + u64 base; + int cpu; + + if (!rmpopt_capable()) + return; + + / + * 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. The MSR + * can only be written after SNP is enabled, so this runs from the ccp + * SNP init path (and again on guest teardown) rather than an initcall. + * + * The loop below programs RMPOPT_BASE on all primary threads. RMPOPT_EN + * cannot be cleared while SNP is enabled, and CPU hotplug is disabled + * while SNP is active, so once programmed the MSRs stay set on all CPUs + * until SNP is disabled. A set RMPOPT_EN on the local CPU therefore + * means the programming has already been done, so skip it. + / + rdmsrq(MSR_AMD64_RMPOPT_BASE, base); + if (!(base & MSR_AMD64_RMPOPT_ENABLE)) + for_each_cpu(cpu, cpu_primary_thread_mask) + wrmsrq_on_cpu(cpu, MSR_AMD64_RMPOPT_BASE, + rmpopt_pa_start \| MSR_AMD64_RMPOPT_ENABLE); + + mod_delayed_work(rmpopt_wq, &rmpopt_delayed_work, + msecs_to_jiffies(RMPOPT_WORK_TIMEOUT)); + + pr_info_once("RMPOPT optimizations enabled\n"); +} +EXPORT_SYMBOL_FOR_MODULES(snp_enable_rmpopt, "ccp,kvm-amd"); + / * 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 +711,8 @@ 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 +722,15 @@ 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 +828,31 @@ 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) { + if (probe_segmented_rmptable_info()) + return true; + + /* + * Segmented RMP is enabled but misconfigured; RMPOPT is + * unusable, so drop the capability before it reaches the + * initcall. + / + setup_clear_cpu_cap(X86_FEATURE_RMPOPT); + return false; + } + } + + / + * 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..5c996ab638959 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_enable_rmpopt(); + return 0; }
3/2	2026/09/18 15:57	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 7682 output: 24 thoughts: 618 Thoughts: My Initial Assessment of This Patch Okay, let's dive into this patch and figure out if it's fuzzable. The target architecture is amd64, which is good. I need to keep the triage philosophy in mind: reachability is king. If this code is unreachable in a standard virtualized environment (GCE or QEMU with emulated devices), then we're not fuzzing it. Simple enough. First, I need to understand what this patch is even doing. The files touched are immediately telling: `cpufeatures.h`, `msr-index.h`, `sev.h`, then a few `.c` files dealing with scattering and AMD's Secure Encrypted Virtualization (SEV) features, specifically related to the KVM. And there is a driver related to the CCP, which is a component of SEV. That's a strong indicator. Now I'm focusing on the specifics. I see "RMPOPT" popping up everywhere, along with "X86_FEATURE_RMPOPT" and the mention of "SEV-SNP host". My immediate questions are: Does standard QEMU or GCE support the SEV-SNP host? And, what about this RMPOPT thing, is it something we can get to? Okay, the RMPOPT support is about "optimizations skip RMP checks at 1GB granularity if this range of memory does not contain any SNP guest memory." Hmm, the assembly looks like a custom instruction. I notice `MSR_AMD64_RMPOPT_BASE` and `X86_FEATURE_ZEN5 / ZEN6` references. I need to see what's required for `rmpopt_capable()` to return true. I need to look for `cc_platform_has(CC_ATTR_HOST_SEV_SNP)`, `snp_rmptable_init`, or `snp_probe_rmptable_info` in the kernel source. That's where the heart of the reachability question is likely to be. My expert instinct is telling me that RMPOPT may need a specific hardware configuration. Let me confirm my suspicion with a search...
4/2	2026/09/18 15:57	tool	grepper	0m Args: { "Expression": "CC_ATTR_HOST_SEV_SNP" } Results: { "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=3088=void __init sev_hardware_setup(void)\n--\narch/x86/kvm/svm/sev.c-3192-\tsev_es_supported = true;\narch/x86/kvm/svm/sev.c:3193:\tsev_snp_supported = sev_snp_enabled \u0026\u0026 cc_platform_has(CC_ATTR_HOST_SEV_SNP);\narch/x86/kvm/svm/sev.c-3194-\n--\narch/x86/kvm/svm/sev.c=4987=struct page snp_safe_alloc_page_node(int node, gfp_t gfp)\n--\narch/x86/kvm/svm/sev.c-4991-\narch/x86/kvm/svm/sev.c:4992:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/kvm/svm/sev.c-4993-\t\treturn alloc_pages_node(node, gfp \| __GFP_ZERO, 0);\n--\narch/x86/kvm/svm/sev.c=5205=void sev_gmem_make_shared(kvm_pfn_t pfn, kvm_pfn_t nr_pages)\n--\narch/x86/kvm/svm/sev.c-5208-\narch/x86/kvm/svm/sev.c:5209:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/kvm/svm/sev.c-5210-\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=156=static void mfd_reconfigure(void arg)\narch/x86/virt/svm/sev.c-157-{\narch/x86/virt/svm/sev.c:158:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-159-\t\treturn;\n--\narch/x86/virt/svm/sev.c=167=static void snp_enable(void arg)\n--\narch/x86/virt/svm/sev.c-170-\narch/x86/virt/svm/sev.c:171:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-172-\t\treturn;\n--\narch/x86/virt/svm/sev.c=269=static void clear_rmp(void)\n--\narch/x86/virt/svm/sev.c-273-\narch/x86/virt/svm/sev.c:274:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-275-\t\treturn;\n--\narch/x86/virt/svm/sev.c=607=static bool rmpopt_capable(void)\n--\narch/x86/virt/svm/sev.c-609-\treturn cpu_feature_enabled(X86_FEATURE_RMPOPT) \u0026\u0026\narch/x86/virt/svm/sev.c:610:\t cc_platform_has(CC_ATTR_HOST_SEV_SNP) \u0026\u0026 rmpopt_enabled;\narch/x86/virt/svm/sev.c-611-}\n--\narch/x86/virt/svm/sev.c=712=int __init snp_rmptable_init(void)\n--\narch/x86/virt/svm/sev.c-715-\narch/x86/virt/svm/sev.c:716:\tif (WARN_ON_ONCE(!cc_platform_has(CC_ATTR_HOST_SEV_SNP)))\narch/x86/virt/svm/sev.c-717-\t\treturn -ENOSYS;\n--\narch/x86/virt/svm/sev.c=931=static int __snp_lookup_rmpentry(u64 pfn, struct rmpentry e, int level)\n--\narch/x86/virt/svm/sev.c-935-\narch/x86/virt/svm/sev.c:936:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-937-\t\treturn -ENODEV;\n--\narch/x86/virt/svm/sev.c=1057=int psmash(u64 pfn)\n--\narch/x86/virt/svm/sev.c-1061-\narch/x86/virt/svm/sev.c:1062:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-1063-\t\treturn -ENODEV;\n--\narch/x86/virt/svm/sev.c=1166=static int rmpupdate(u64 pfn, struct rmp_state state)\n--\narch/x86/virt/svm/sev.c-1170-\narch/x86/virt/svm/sev.c:1171:\tif (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-1172-\t\treturn -ENODEV;\n--\narch/x86/virt/svm/sev.c=1259=void kdump_sev_callback(void)\n--\narch/x86/virt/svm/sev.c-1264-\t /\narch/x86/virt/svm/sev.c:1265:\tif (cc_platform_has(CC_ATTR_HOST_SEV_SNP))\narch/x86/virt/svm/sev.c-1266-\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" }
5/2	2026/09/18 15:57	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 12833 output: 41 thoughts: 84 Thoughts: Here's my thought process, as it stands: Digging into the `CC_ATTR_HOST_SEV_SNP` Enabler Alright, so I need to figure out what's enabling `CC_ATTR_HOST_SEV_SNP`. Given my expertise, I'll start by assuming the likely location: the AMD-specific code, of course. So, where would I find that kind of logic? Let's check `arch/x86/kernel/cpu/amd.c`. That's usually the go-to place for anything AMD related within the x86 kernel. Now, within `amd.c`, I'll bet the function that determines SNP capabilities will be something like `bsp_determine_snp()`. I'll want to get a look at that function, so I'll go take a look at the file around line 356. I'll take a look at the implementation to see how the bit gets flipped.
6/2	2026/09/18 15:58	tool	read-file	0m Args: { "File": "arch/x86/kernel/cpu/amd.c", "FirstLine": 350, "LineCount": 40 } Results: { "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" }
7/2	2026/09/18 15:58	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 13906 output: 26 thoughts: 826 Thoughts: Analyzing the RMPOPT Feature in the Context of SNP Okay, let's break this down. Line 369 immediately catches my eye: it's checking for the absence of `X86_FEATURE_HYPERVISOR`, but also for a combination of Zen 3/4 or RMPREAD features and a probe for RMPTABLE information. The `!cpu_has(c, X86_FEATURE_HYPERVISOR)` condition is the key here. Normally, in any standard virtualized environment – GCE, QEMU, anything like that – `X86_FEATURE_HYPERVISOR` is set. It's a fundamental part of the CPUID enumeration in those setups. So, my initial thought is, this condition seems like a misconfiguration, or something specifically targeting a non-virtualized environment for AMD's SNP (Secure Nested Paging) technology. But, hang on, can SNP even run in a standard QEMU environment? No, that can't be right. SNP is specifically designed to be used with a hardware-based security root of trust (the AMD SEV platform). It's not supposed to be able to run in a QEMU type setup. This patch, specifically, is adding support for `X86_FEATURE_RMPOPT`, which is the "Support for AMD RMPOPT instruction". It's related to the RMP (Read/Modify/Protect) table and associated MSRs. The relevant bits here are, the RMPOPT instruction (`.byte 0xf2, 0x0f, 0x01, 0xfc`) and how it's handled in `rmpopt_capable()`, `rmpopt_init()`, and especially `snp_probe_rmptable_info()`. In `rmpopt_capable()`, RMPOPT is only considered capable if the `X86_FEATURE_RMPOPT` is enabled, and `CC_ATTR_HOST_SEV_SNP` is set, and finally if `rmpopt_enabled` is true. `rmpopt_init()` checks for `X86_FEATURE_RMPOPT` and returns early if it's not present. The crucial piece is `snp_probe_rmptable_info()`. This is where the feature gets configured: it first checks for `X86_FEATURE_SEGMENTED_RMP`. If that's enabled, it reads an MSR, checks a bit (`MSR_AMD64_SEG_RMP_ENABLED`). If `SEGMENTED_RMP` is misconfigured (enabled, but probe fails), or, critically, if `X86_FEATURE_SEGMENTED_RMP` is not enabled at all, or disabled by the firmware, then `setup_clear_cpu_cap(X86_FEATURE_RMPOPT)` is called. This function is important since it is only called in a very specific scenario, it means the RMPOPT functionality is disabled. This tells me that RMPOPT is contingent on `SEGMENTED_RMP` either being supported, or enabled by the firmware. It's an important configuration step. So, either it's explicitly disabled or just not present, and RMPOPT is removed. Now I need to check where `X86_FEATURE_SEGMENTED_RMP` is defined and used. I need to understand that dependency fully.
8/2	2026/09/18 15:59	tool	grepper	0m Args: { "Expression": "X86_FEATURE_SEGMENTED_RMP" } Results: { "Output": "arch/x86/include/asm/cpufeatures.h-470-#define X86_FEATURE_RMPREAD\t\t(1932+21) / RMPREAD instruction /\narch/x86/include/asm/cpufeatures.h:471:#define X86_FEATURE_SEGMENTED_RMP\t(1932+23) /* Segmented RMP support /\narch/x86/include/asm/cpufeatures.h-472-#define X86_FEATURE_ALLOWED_SEV_FEATURES (1932+27) /* Allowed SEV Features /\n--\narch/x86/virt/svm/sev.c=829=bool snp_probe_rmptable_info(void)\narch/x86/virt/svm/sev.c-830-{\narch/x86/virt/svm/sev.c:831:\tif (cpu_feature_enabled(X86_FEATURE_SEGMENTED_RMP)) {\narch/x86/virt/svm/sev.c-832-\t\trdmsrq(MSR_AMD64_RMP_CFG, rmp_cfg);\n--\ntools/arch/x86/include/asm/cpufeatures.h-458-#define X86_FEATURE_RMPREAD\t\t(1932+21) /* RMPREAD instruction /\ntools/arch/x86/include/asm/cpufeatures.h:459:#define X86_FEATURE_SEGMENTED_RMP\t(1932+23) /* Segmented RMP support /\ntools/arch/x86/include/asm/cpufeatures.h-460-#define X86_FEATURE_ALLOWED_SEV_FEATURES (1932+27) /* Allowed SEV Features */\n" }
9/2	2026/09/18 15:59	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 15966 output: 24 thoughts: 3269 Thoughts: Analysis of SEV-SNP Reachability for Fuzzing Alright, let's break this down. My primary concern here is determining the reachability of this code within the context of fuzzing, specifically in environments like QEMU or Google Compute Engine (GCE). We're talking about code related to the `RMPOPT` instruction, which appears to be a hardware feature relevant to AMD's SEV-SNP (Secure Nested Paging) technology. My initial thought was, "Which CPUs even have `X86_FEATURE_RMPOPT`?". Seems like it's a Zen 5/Zen 6 thing. Then I went digging. I spotted it in `scattered.c`, associated with `CPUID_EDX`. I know that QEMU generally doesn't emulate these specialized features. Does it even emulate SEV-SNP? My understanding of SEV-SNP is that it's fundamentally a hardware security feature. It requires an AMD processor with SEV-SNP enabled in the BIOS/firmware, and crucially, the RMP (Reverse Map Table) needs to be configured by the firmware and the AMD Secure Processor (CCP). Standard QEMU, or even GCE, can't be an SEV-SNP host, and therefore, cannot run a nested SEV-SNP environment. This brings me to the core principle of my triage: Is this code actually executable in standard virtualized environments? Section 1 of the triage philosophy tells me that if the code is unreachable in standard environments, it's not worth fuzzing. I have to apply the negative criteria. Section 2 confirms that hardware-specific features that require physical hardware are out. Things like vendor-specific PCIe switches, SmartNICs, GPU drivers (like `amdgpu` in the examples), requiring PCIe cards or physical ASICs not emulated in QEMU, are automatically disqualified. So, the question shifts: Can KVM SEV host code be reached through syzkaller? I know that syzkaller fuzzes `/dev/kvm`, but can it actually exercise SEV-SNP host code? I examined the patch. Here's a quick overview of the relevant files and functions: 1. `arch/x86/include/asm/cpufeatures.h`: Defines `X86_FEATURE_RMPOPT`. 2. `arch/x86/include/asm/msr-index.h`: Defines MSRs related to RMPOPT. 3. `arch/x86/include/asm/sev.h`: Declares `snp_enable_rmpopt()`. 4. `arch/x86/kernel/cpu/scattered.c`: Associates `X86_FEATURE_RMPOPT` with `CPUID_EDX`. 5. `arch/x86/kvm/svm/sev.c`: Contains `snp_enable_rmpopt()` within `sev_vm_destroy()`. This is concerning. Is this ever reached? 6. `arch/x86/virt/svm/sev.c`: Contains the `rmpopt_wq` and `rmpopt_enabled` variables, and the `rmpopt()` function with the RMPOPT instruction. Also contains `snp_prepare()` and `snp_shutdown()`. 7. `drivers/crypto/ccp/sev-dev.c`: Calls `snp_enable_rmpopt()`. My goal is to determine if any of this code can execute in a standard fuzzing environment, which is QEMU or GCE. Let's carefully examine if this code path is even reachable. Let's see how SEV-SNP is initialized: The crucial piece of the puzzle is in `arch/x86/kernel/cpu/amd.c`. Specifically, the function `bsp_determine_snp()`. It checks for `X86_FEATURE_SEV_SNP`. But here's the kicker: `if (!cpu_has(c, X86_FEATURE_HYPERVISOR))`. This is problematic. Every time the kernel boots inside QEMU or GCE, the hypervisor bit is set in the CPUID. This means the condition is always true. Therefore, the code immediately executes `setup_clear_cpu_cap(X86_FEATURE_SEV_SNP)` and `cc_platform_clear(CC_ATTR_HOST_SEV_SNP)`. This means that `CC_ATTR_HOST_SEV_SNP` is NEVER set inside QEMU or GCE. Could QEMU be run with `-cpu host` to clear the hypervisor
10/2	2026/09/18 15:59	tool	grepper	0m Args: { "Expression": "KVM_X86_SNP_VM" } Results: { "Output": "Documentation/virt/kvm/api.rst=9512=means the VM type with value @n is supported. Possible values of @n are::\n--\nDocumentation/virt/kvm/api.rst-9517- #define KVM_X86_SEV_ES_VM\t3\nDocumentation/virt/kvm/api.rst:9518: #define KVM_X86_SNP_VM\t4\nDocumentation/virt/kvm/api.rst-9519- #define KVM_X86_TDX_VM\t5\n--\narch/x86/include/uapi/asm/kvm.h=927=struct kvm_hyperv_eventfd {\n--\narch/x86/include/uapi/asm/kvm.h-973-#define KVM_X86_SEV_ES_VM\t3\narch/x86/include/uapi/asm/kvm.h:974:#define KVM_X86_SNP_VM\t\t4\narch/x86/include/uapi/asm/kvm.h-975-#define KVM_X86_TDX_VM\t\t5\n--\narch/x86/kvm/svm/sev.c=265=static int sev_asid_new(struct kvm_sev_info sev, unsigned long vm_type)\n--\narch/x86/kvm/svm/sev.c-273-\narch/x86/kvm/svm/sev.c:274:\tif (vm_type == KVM_X86_SNP_VM) {\narch/x86/kvm/svm/sev.c-275-\t\tmin_asid = min_snp_asid;\n--\narch/x86/kvm/svm/sev.c=491=static int __sev_guest_init(struct kvm kvm, struct kvm_sev_cmd argp,\n--\narch/x86/kvm/svm/sev.c-497-\tbool es_active = vm_type != KVM_X86_SEV_VM;\narch/x86/kvm/svm/sev.c:498:\tbool snp_active = vm_type == KVM_X86_SNP_VM;\narch/x86/kvm/svm/sev.c-499-\tu64 valid_vmsa_features = es_active ? sev_supported_vmsa_features : 0;\n--\narch/x86/kvm/svm/sev.c=604=static int sev_guest_init2(struct kvm kvm, struct kvm_sev_cmd argp)\n--\narch/x86/kvm/svm/sev.c-612-\t kvm-\u003earch.vm_type != KVM_X86_SEV_ES_VM \u0026\u0026\narch/x86/kvm/svm/sev.c:613:\t kvm-\u003earch.vm_type != KVM_X86_SNP_VM)\narch/x86/kvm/svm/sev.c-614-\t\treturn -EINVAL;\n--\narch/x86/kvm/svm/sev.c=2955=void sev_vm_init(struct kvm kvm)\n--\narch/x86/kvm/svm/sev.c-2960-\t\tbreak;\narch/x86/kvm/svm/sev.c:2961:\tcase KVM_X86_SNP_VM:\narch/x86/kvm/svm/sev.c-2962-\t\tkvm-\u003earch.has_private_mem = true;\n--\narch/x86/kvm/svm/sev.c=3088=void __init sev_hardware_setup(void)\n--\narch/x86/kvm/svm/sev.c-3233-\tif (sev_snp_supported)\narch/x86/kvm/svm/sev.c:3234:\t\tvm_types \|= BIT(KVM_X86_SNP_VM);\narch/x86/kvm/svm/sev.c-3235-\tvm_types \u0026= sev_firmware_supported_vm_types();\n--\narch/x86/kvm/svm/sev.c-3248-\t\tpr_info(\"SEV-SNP %s (ASIDs %u - %u)\\n\",\narch/x86/kvm/svm/sev.c:3249:\t\t\tsev_str_feature_state(sev_snp_supported, vm_types \u0026 BIT(KVM_X86_SNP_VM)),\narch/x86/kvm/svm/sev.c-3250-\t\t\tmin_snp_asid, max_snp_asid);\n--\ndrivers/crypto/ccp/sev-dev.c=3147=int sev_firmware_supported_vm_types(void)\n--\ndrivers/crypto/ccp/sev-dev.c-3161-\ndrivers/crypto/ccp/sev-dev.c:3162:\tsupported_vm_types \|= BIT(KVM_X86_SNP_VM);\ndrivers/crypto/ccp/sev-dev.c-3163-\n--\ntools/arch/x86/include/uapi/asm/kvm.h=927=struct kvm_hyperv_eventfd {\n--\ntools/arch/x86/include/uapi/asm/kvm.h-973-#define KVM_X86_SEV_ES_VM\t3\ntools/arch/x86/include/uapi/asm/kvm.h:974:#define KVM_X86_SNP_VM\t\t4\ntools/arch/x86/include/uapi/asm/kvm.h-975-#define KVM_X86_TDX_VM\t\t5\n--\ntools/testing/selftests/kvm/include/x86/sev.h=34=static inline bool is_sev_snp_vm(struct kvm_vm vm)\ntools/testing/selftests/kvm/include/x86/sev.h-35-{\ntools/testing/selftests/kvm/include/x86/sev.h:36:\treturn vm-\u003etype == KVM_X86_SNP_VM;\ntools/testing/selftests/kvm/include/x86/sev.h-37-}\n--\ntools/testing/selftests/kvm/lib/kvm_util.c=478=static bool is_guest_memfd_required(struct vm_shape shape)\n--\ntools/testing/selftests/kvm/lib/kvm_util.c-480-#ifdef __x86_64__\ntools/testing/selftests/kvm/lib/kvm_util.c:481:\treturn shape.type == KVM_X86_SNP_VM;\ntools/testing/selftests/kvm/lib/kvm_util.c-482-#else\n--\ntools/testing/selftests/kvm/lib/x86/sev.c=74=void snp_vm_init(struct kvm_vm vm)\n--\ntools/testing/selftests/kvm/lib/x86/sev.c-77-\ntools/testing/selftests/kvm/lib/x86/sev.c:78:\tTEST_ASSERT_EQ(vm-\u003etype, KVM_X86_SNP_VM);\ntools/testing/selftests/kvm/lib/x86/sev.c-79-\tvm_sev_ioctl(vm, KVM_SEV_INIT2, \u0026init);\n--\ntools/testing/selftests/kvm/x86/sev_init2_tests.c=76=void test_vm_types(void)\n--\ntools/testing/selftests/kvm/x86/sev_init2_tests.c-83-\tif (have_snp)\ntools/testing/selftests/kvm/x86/sev_init2_tests.c:84:\t\ttest_init2(KVM_X86_SNP_VM, \u0026(struct kvm_sev_init){});\ntools/testing/selftests/kvm/x86/sev_init2_tests.c-85-\n--\ntools/testing/selftests/kvm/x86/sev_init2_tests.c=118=int main(int argc, char argv[])\n--\ntools/testing/selftests/kvm/x86/sev_init2_tests.c-145-\ntools/testing/selftests/kvm/x86/sev_init2_tests.c:146:\thave_snp = kvm_check_cap(KVM_CAP_VM_TYPES) \u0026 BIT(KVM_X86_SNP_VM);\ntools/testing/selftests/kvm/x86/sev_init2_tests.c-147-\tTEST_ASSERT(!have_snp \|\| kvm_cpu_has(X86_FEATURE_SEV_SNP),\n--\ntools/testing/selftests/kvm/x86/sev_init2_tests.c-155-\tif (have_snp)\ntools/testing/selftests/kvm/x86/sev_init2_tests.c:156:\t\ttest_flags(KVM_X86_SNP_VM);\ntools/testing/selftests/kvm/x86/sev_init2_tests.c-157-\n--\ntools/testing/selftests/kvm/x86/sev_init2_tests.c-161-\tif (have_snp)\ntools/testing/selftests/kvm/x86/sev_init2_tests.c:162:\t\ttest_features(KVM_X86_SNP_VM, supported_vmsa_features);\ntools/testing/selftests/kvm/x86/sev_init2_tests.c-163-\n--\ntools/testing/selftests/kvm/x86/sev_migrate_tests.c=316=static void test_sev_snp_migrate_reject(void)\n--\ntools/testing/selftests/kvm/x86/sev_migrate_tests.c-320-\ntools/testing/selftests/kvm/x86/sev_migrate_tests.c:321:\tsrc_vm = vm_create_barebones_type(KVM_X86_SNP_VM);\ntools/testing/selftests/kvm/x86/sev_migrate_tests.c-322-\tsnp_vm_init(src_vm);\n--\ntools/testing/selftests/kvm/x86/sev_migrate_tests.c-325-\ntools/testing/selftests/kvm/x86/sev_migrate_tests.c:326:\tdst_vm = vm_create_barebones_type(KVM_X86_SNP_VM);\ntools/testing/selftests/kvm/x86/sev_migrate_tests.c-327-\t__vm_vcpu_add(dst_vm, 0);\n--\ntools/testing/selftests/kvm/x86/sev_migrate_tests.c=338=static void test_sev_snp_mirror_reject(void)\n--\ntools/testing/selftests/kvm/x86/sev_migrate_tests.c-342-\ntools/testing/selftests/kvm/x86/sev_migrate_tests.c:343:\tsrc_vm = vm_create_barebones_type(KVM_X86_SNP_VM);\ntools/testing/selftests/kvm/x86/sev_migrate_tests.c-344-\tsnp_vm_init(src_vm);\n--\ntools/testing/selftests/kvm/x86/sev_smoke_test.c=221=static void test_sev_smoke(void guest, u32 type, u64 policy)\n--\ntools/testing/selftests/kvm/x86/sev_smoke_test.c-224-\ntools/testing/selftests/kvm/x86/sev_smoke_test.c:225:\tif (type == KVM_X86_SNP_VM)\ntools/testing/selftests/kvm/x86/sev_smoke_test.c-226-\t\ttest_sev(guest, type, policy \| SNP_POLICY_DBG);\n--\ntools/testing/selftests/kvm/x86/sev_smoke_test.c-238-\t\ttest_sync_vmsa(type, policy);\ntools/testing/selftests/kvm/x86/sev_smoke_test.c:239:\t\tif (type == KVM_X86_SNP_VM)\ntools/testing/selftests/kvm/x86/sev_smoke_test.c-240-\t\t\ttest_sync_vmsa(type, policy \| SNP_POLICY_DBG);\n--\ntools/testing/selftests/kvm/x86/sev_smoke_test.c=246=int main(int argc, char *argv[])\n--\ntools/testing/selftests/kvm/x86/sev_smoke_test.c-261-\ntools/testing/selftests/kvm/x86/sev_smoke_test.c:262:\tif (kvm_check_cap(KVM_CAP_VM_TYPES) \u0026 BIT(KVM_X86_SNP_VM))\ntools/testing/selftests/kvm/x86/sev_smoke_test.c:263:\t\ttest_sev_smoke(guest_snp_code, KVM_X86_SNP_VM, snp_default_policy());\ntools/testing/selftests/kvm/x86/sev_smoke_test.c-264-\n" }
11/2	2026/09/18 15:59	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 23765 output: 38 thoughts: 145 Thoughts: Analyzing KVM-SVM-SEV Support Okay, let's break this down. I'm looking at `arch/x86/kvm/svm/sev.c` right now. My first observation is the key check: `sev_snp_supported = sev_snp_enabled && cc_platform_has(CC_ATTR_HOST_SEV_SNP);`. This makes sense; we need both SEV-SNP enabled and the platform to actually support it at the hardware level, as indicated by `cc_platform_has(CC_ATTR_HOST_SEV_SNP)`. That's the baseline. Next, I'm checking how this `sev_snp_supported` variable is utilized within the `vm_types` bitmask. I see that if SNP is supported, then the `KVM_X86_SNP_VM` bit gets set in `vm_types`. However, and this is important, `vm_types` is then ANDed with the result of `sev_firmware_supported_vm_types()`. So, the firmware configuration acts as a filter on top of the hardware capability. Very good. This provides a software mechanism to limit things even if the CPU supports SEV-SNP. Now, I need to understand where `kvm->arch.vm_type` gets used. I need to find the specific places in the code where it is set and where it is checked to get a complete picture. Let's see how `kvm_arch_init_vm` uses `vm_type`. Where else is this value accessed? I need to trace this variable.
12/2	2026/09/18 16:00	tool	grepper	0m Args: { "Expression": "KVM_X86_SNP_VM", "PathPrefix": "arch/x86/kvm" } Results: { "Output": "arch/x86/kvm/svm/sev.c=265=static int sev_asid_new(struct kvm_sev_info sev, unsigned long vm_type)\n--\narch/x86/kvm/svm/sev.c-273-\narch/x86/kvm/svm/sev.c:274:\tif (vm_type == KVM_X86_SNP_VM) {\narch/x86/kvm/svm/sev.c-275-\t\tmin_asid = min_snp_asid;\n--\narch/x86/kvm/svm/sev.c=491=static int __sev_guest_init(struct kvm kvm, struct kvm_sev_cmd argp,\n--\narch/x86/kvm/svm/sev.c-497-\tbool es_active = vm_type != KVM_X86_SEV_VM;\narch/x86/kvm/svm/sev.c:498:\tbool snp_active = vm_type == KVM_X86_SNP_VM;\narch/x86/kvm/svm/sev.c-499-\tu64 valid_vmsa_features = es_active ? sev_supported_vmsa_features : 0;\n--\narch/x86/kvm/svm/sev.c=604=static int sev_guest_init2(struct kvm kvm, struct kvm_sev_cmd argp)\n--\narch/x86/kvm/svm/sev.c-612-\t kvm-\u003earch.vm_type != KVM_X86_SEV_ES_VM \u0026\u0026\narch/x86/kvm/svm/sev.c:613:\t kvm-\u003earch.vm_type != KVM_X86_SNP_VM)\narch/x86/kvm/svm/sev.c-614-\t\treturn -EINVAL;\n--\narch/x86/kvm/svm/sev.c=2955=void sev_vm_init(struct kvm kvm)\n--\narch/x86/kvm/svm/sev.c-2960-\t\tbreak;\narch/x86/kvm/svm/sev.c:2961:\tcase KVM_X86_SNP_VM:\narch/x86/kvm/svm/sev.c-2962-\t\tkvm-\u003earch.has_private_mem = true;\n--\narch/x86/kvm/svm/sev.c=3088=void __init sev_hardware_setup(void)\n--\narch/x86/kvm/svm/sev.c-3233-\tif (sev_snp_supported)\narch/x86/kvm/svm/sev.c:3234:\t\tvm_types \|= BIT(KVM_X86_SNP_VM);\narch/x86/kvm/svm/sev.c-3235-\tvm_types \u0026= sev_firmware_supported_vm_types();\n--\narch/x86/kvm/svm/sev.c-3248-\t\tpr_info(\"SEV-SNP %s (ASIDs %u - %u)\\n\",\narch/x86/kvm/svm/sev.c:3249:\t\t\tsev_str_feature_state(sev_snp_supported, vm_types \u0026 BIT(KVM_X86_SNP_VM)),\narch/x86/kvm/svm/sev.c-3250-\t\t\tmin_snp_asid, max_snp_asid);\n" }
13/2	2026/09/18 16:00	llm	patch-evaluator	1m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 25207 output: 31 thoughts: 34 Thoughts: Here's a summary of my thought process, as requested: Diving into KVM/SVM SEV VM Validation Okay, so I need to understand how the VM type validation works in the context of AMD Secure Encrypted Virtualization (SEV) within the KVM/x86 environment. My first thought is to pinpoint where this validation actually happens. The prompt directs me to `arch/x86/kvm/svm/sev.c`, which makes sense; this is the area handling the Secure Virtual Machine functionality. Specifically, I need to check how the code validates the VM type, so I will start by looking at how a VM creation call is managed. I'm focusing on the logic around that specific function, and specifically where the `vm_type` variable is processed. Let's see what's happening around that line of code.
14/2	2026/09/18 16:01	tool	grepper	0m Args: { "Expression": "vm_types", "PathPrefix": "arch/x86/kvm" } Results: { "Output": "arch/x86/kvm/svm/avic.c-16-\narch/x86/kvm/svm/avic.c:17:#include \u003clinux/kvm_types.h\u003e\narch/x86/kvm/svm/avic.c-18-#include \u003clinux/hashtable.h\u003e\n--\narch/x86/kvm/svm/nested.c-16-\narch/x86/kvm/svm/nested.c:17:#include \u003clinux/kvm_types.h\u003e\narch/x86/kvm/svm/nested.c-18-#include \u003clinux/kvm_host.h\u003e\n--\narch/x86/kvm/svm/sev.c-10-\narch/x86/kvm/svm/sev.c:11:#include \u003clinux/kvm_types.h\u003e\narch/x86/kvm/svm/sev.c-12-#include \u003clinux/kvm_host.h\u003e\n--\narch/x86/kvm/svm/sev.c=3088=void __init sev_hardware_setup(void)\n--\narch/x86/kvm/svm/sev.c-3094-\tbool sev_supported = false;\narch/x86/kvm/svm/sev.c:3095:\tu32 vm_types = 0;\narch/x86/kvm/svm/sev.c-3096-\n--\narch/x86/kvm/svm/sev.c-3229-\tif (sev_supported \u0026\u0026 min_sev_asid \u003c= max_sev_asid)\narch/x86/kvm/svm/sev.c:3230:\t\tvm_types \|= BIT(KVM_X86_SEV_VM);\narch/x86/kvm/svm/sev.c-3231-\tif (sev_es_supported \u0026\u0026 min_sev_es_asid \u003c= max_sev_es_asid)\narch/x86/kvm/svm/sev.c:3232:\t\tvm_types \|= BIT(KVM_X86_SEV_ES_VM);\narch/x86/kvm/svm/sev.c-3233-\tif (sev_snp_supported)\narch/x86/kvm/svm/sev.c:3234:\t\tvm_types \|= BIT(KVM_X86_SNP_VM);\narch/x86/kvm/svm/sev.c:3235:\tvm_types \u0026= sev_firmware_supported_vm_types();\narch/x86/kvm/svm/sev.c-3236-\narch/x86/kvm/svm/sev.c:3237:\tkvm_caps.supported_vm_types \|= vm_types;\narch/x86/kvm/svm/sev.c-3238-\n--\narch/x86/kvm/svm/sev.c-3240-\t\tpr_info(\"SEV %s (ASIDs %u - %u)\\n\",\narch/x86/kvm/svm/sev.c:3241:\t\t\tsev_str_feature_state(sev_supported, vm_types \u0026 BIT(KVM_X86_SEV_VM)),\narch/x86/kvm/svm/sev.c-3242-\t\t\tmin_sev_asid, max_sev_asid);\n--\narch/x86/kvm/svm/sev.c-3244-\t\tpr_info(\"SEV-ES %s (ASIDs %u - %u)\\n\",\narch/x86/kvm/svm/sev.c:3245:\t\t\tsev_str_feature_state(sev_es_supported, vm_types \u0026 BIT(KVM_X86_SEV_ES_VM)),\narch/x86/kvm/svm/sev.c-3246-\t\t\tmin_sev_es_asid, max_sev_es_asid);\n--\narch/x86/kvm/svm/sev.c-3248-\t\tpr_info(\"SEV-SNP %s (ASIDs %u - %u)\\n\",\narch/x86/kvm/svm/sev.c:3249:\t\t\tsev_str_feature_state(sev_snp_supported, vm_types \u0026 BIT(KVM_X86_SNP_VM)),\narch/x86/kvm/svm/sev.c-3250-\t\t\tmin_snp_asid, max_snp_asid);\n--\narch/x86/kvm/svm/svm.h-17-\narch/x86/kvm/svm/svm.h:18:#include \u003clinux/kvm_types.h\u003e\narch/x86/kvm/svm/svm.h-19-#include \u003clinux/kvm_host.h\u003e\n--\narch/x86/kvm/vmx/main.c=1058=static int __init vt_init(void)\n--\narch/x86/kvm/vmx/main.c-1078-\t\t\t\t__alignof__(struct vcpu_tdx));\narch/x86/kvm/vmx/main.c:1079:\t\tkvm_caps.supported_vm_types \|= BIT(KVM_X86_TDX_VM);\narch/x86/kvm/vmx/main.c-1080-\t}\n--\narch/x86/kvm/x86.c=2193=static bool kvm_is_vm_type_supported(unsigned long type)\narch/x86/kvm/x86.c-2194-{\narch/x86/kvm/x86.c:2195:\treturn type \u003c 32 \u0026\u0026 (kvm_caps.supported_vm_types \u0026 BIT(type));\narch/x86/kvm/x86.c-2196-}\n--\narch/x86/kvm/x86.c=2203=int kvm_vm_ioctl_check_extension(struct kvm kvm, long ext)\n--\narch/x86/kvm/x86.c-2404-\tcase KVM_CAP_VM_TYPES:\narch/x86/kvm/x86.c:2405:\t\tr = kvm_caps.supported_vm_types;\narch/x86/kvm/x86.c-2406-\t\tbreak;\n--\narch/x86/kvm/x86.c=6999=int kvm_x86_vendor_init(struct kvm_x86_init_ops ops)\n--\narch/x86/kvm/x86.c-7062-\narch/x86/kvm/x86.c:7063:\tkvm_caps.supported_vm_types = BIT(KVM_X86_DEFAULT_VM);\narch/x86/kvm/x86.c-7064-\tkvm_caps.supported_mce_cap = MCG_CTL_P \| MCG_SER_P;\n--\narch/x86/kvm/x86.c-7124-\tif (IS_ENABLED(CONFIG_KVM_SW_PROTECTED_VM) \u0026\u0026 tdp_mmu_enabled)\narch/x86/kvm/x86.c:7125:\t\tkvm_caps.supported_vm_types \|= BIT(KVM_X86_SW_PROTECTED_VM);\narch/x86/kvm/x86.c-7126-\n" }
15/2	2026/09/18 16:01	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27362 output: 18 thoughts: 605 Thoughts: My Analysis of KVM SEV-SNP Support Okay, let's break this down systematically. I need to understand the path KVM takes to determine if SEV-SNP is supported, and specifically, why RMPOPT might not be enabled. First, I see the function `kvm_is_vm_type_supported()`. It boils down to checking a bit in `kvm_caps.supported_vm_types`. This bit, `BIT(KVM_X86_SNP_VM)`, is set only if `sev_snp_supported` is true. Now, `sev_snp_supported` has a few crucial dependencies. The most interesting for my purposes are: * `cpu_has(c, X86_FEATURE_SEV_SNP)`: This is basic hardware capability - it's expected. * `!cpu_has(c, X86_FEATURE_HYPERVISOR)`: Ah-ha! *This means SEV-SNP is not* supposed to work within a virtual machine.** That's important to remember. * The system must be running on Zen3/Zen4 hardware (cpu\_feature\_enabled(X86\_FEATURE\_ZEN3) \|\| cpu\_feature\_enabled(X86\_FEATURE\_ZEN4)) or have RMPREAD (cpu\_feature\_enabled(X86\_FEATURE\_RMPREAD)) enabled. * `snp_probe_rmptable_info()` returns true. So, let's dig into `snp_probe_rmptable_info()`. I can see it checks MSRs (Model Specific Registers) like RMP\_BASE, RMP\_END and RMP\_CFG. It's essentially probing for the AMD hardware features required for RMP tables. Fine, expected for AMD hardware. Next I see `rmpopt_capable()`. This is interesting; I need to understand it. It checks a few things. Critically, it checks `cpu_feature_enabled(X86_FEATURE_RMPOPT)` and also `cc_platform_has(CC_ATTR_HOST_SEV_SNP)` which reinforces the platform requirement for SEV-SNP and it has `rmpopt_enabled` Now, I look at `snp_enable_rmpopt()` and it checks `rmpopt_capable()`. If not, it simply returns. This is potentially important because I want to ensure RMPOPT is enabled. My key question is where are `snp_prepare()` or `snp_shutdown()` called, to understand the flow and to ensure that RMPOPT is actually enabled. I need to track those calls to see what could potentially cause issues. My next step is to search for these functions in the code base to better understand how RMPOPT is enabled or disabled.
16/2	2026/09/18 16:02	tool	grepper	0m Args: { "Expression": "snp_prepare\\(" } Results: { "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_enable_rmpopt(void);\n--\narch/x86/include/asm/sev.h=682=static inline void snp_fixup_e820_tables(void) {}\narch/x86/include/asm/sev.h:683:static inline int snp_prepare(void) { return -ENODEV; }\narch/x86/include/asm/sev.h-684-static inline void snp_enable_rmpopt(void) {}\n--\narch/x86/virt/svm/sev.c=530=static void clear_hsave_pa(void arg)\n--\narch/x86/virt/svm/sev.c-534-\narch/x86/virt/svm/sev.c:535:int snp_prepare(void)\narch/x86/virt/svm/sev.c-536-{\n--\narch/x86/virt/svm/sev.c=712=int __init snp_rmptable_init(void)\n--\narch/x86/virt/svm/sev.c-726-\t On a kexec boot SNP may already be enabled (legacy firmware leaves\narch/x86/virt/svm/sev.c:727:\t * SnpEn set across shutdown), in which case snp_prepare() bails without\narch/x86/virt/svm/sev.c-728-\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" }
17/2	2026/09/18 16:02	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29195 output: 18 thoughts: 106 Thoughts: Here's my analysis of the provided code snippet: Investigating `snp_prepare()` and Its Context Okay, so `snp_prepare()` is apparently only called within `drivers/crypto/ccp/sev-dev.c`. I need to figure out the exact call location. Specifically, I see it's used inside the `__sev_snp_init_locked()` function, which is interesting. This looks like some initialization routine for SEV-SNP functionality. I should note the check at line 1517 which is essentially a feature detection check. It's using `cc_platform_has(CC_ATTR_HOST_SEV_SNP)` to ensure the host system has SEV-SNP capabilities before proceeding. This makes sense; it's a good practice to avoid errors when trying to use hardware features that are not present. Now, the important thing for me to understand this code base, is where `snp_shutdown()` is being called to pair the logic. Since `snp_prepare()` is called, its counterpart must also exist. Time to leverage `grep` to quickly locate the calls to `snp_shutdown()` and get a fuller picture of the lifecycle.
18/2	2026/09/18 16:02	tool	grepper	0m Args: { "Expression": "snp_shutdown\\(" } Results: { "Output": "arch/x86/include/asm/sev.h=665=void snp_enable_rmpopt(void);\narch/x86/include/asm/sev.h:666:void snp_shutdown(void);\narch/x86/include/asm/sev.h-667-#else\n--\narch/x86/include/asm/sev.h=684=static inline void snp_enable_rmpopt(void) {}\narch/x86/include/asm/sev.h:685:static inline void snp_shutdown(void) {}\narch/x86/include/asm/sev.h-686-#endif\n--\narch/x86/virt/svm/sev.c=535=int snp_prepare(void)\n--\narch/x86/virt/svm/sev.c-550-\t * No CPU may come online without SnpEn while SNP is active; disable\narch/x86/virt/svm/sev.c:551:\t * hotplug here and re-enable it in snp_shutdown().\narch/x86/virt/svm/sev.c-552-\t /\n--\narch/x86/virt/svm/sev.c=579=static void rmpopt_disable(void)\n--\narch/x86/virt/svm/sev.c-584-\narch/x86/virt/svm/sev.c:585:void snp_shutdown(void)\narch/x86/virt/svm/sev.c-586-{\n--\ndrivers/crypto/ccp/sev-dev.c=2191=static int __sev_snp_shutdown_locked(int error, bool panic)\n--\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" }
19/2	2026/09/18 16:02	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30095 output: 23 thoughts: 77 Thoughts: Investigating the AMD Secure Processor (CCP) in QEMU Okay, so I'm looking at this `__sev_snp_shutdown_locked` function, and it's located in `sev-dev.c`. Right, that's part of the AMD Secure Processor driver, which is basically the CCP or the AMD PSP. My immediate question is: can I actually probe this thing in a QEMU environment? I need to get in there and see how the CCP interacts within a virtualized setup. My next step is to examine the CCP driver in QEMU specifically. I need to search for either the PCI IDs associated with the CCP or investigate how the driver registers itself within the system. That'll give me the initial foothold I need.
20/2	2026/09/18 16:02	tool	grepper	0m Error: no matches Args: { "Expression": "pci_register_driver.ccp" } Results:* { "error": "no matches" }
21/2	2026/09/18 16:02	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30369 output: 32 thoughts: 19 Thoughts: Here's a summary of my immediate thought process: Diving into the CCP Driver Okay, time to dig in. I need to get familiar with the CCP driver, specifically the `sp-pci.c` file within the `drivers/crypto/ccp` directory. This is where the PCI-specific implementation likely resides. I'm probably looking for initialization sequences, interrupt handling, or the actual communication routines with the CCP hardware on the PCI bus. Given the context, this is most likely the critical file to understand how the system interacts with the crypto hardware. Let's see what's in there.
22/2	2026/09/18 16:03	tool	grepper	0m Args: { "Expression": "pci_register_driver", "PathPrefix": "drivers/crypto/ccp" } Results: { "Output": "drivers/crypto/ccp/sp-pci.c=592=int sp_pci_init(void)\ndrivers/crypto/ccp/sp-pci.c-593-{\ndrivers/crypto/ccp/sp-pci.c:594:\treturn pci_register_driver(\u0026sp_pci_driver);\ndrivers/crypto/ccp/sp-pci.c-595-}\n" }
23/2	2026/09/18 16:03	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30665 output: 41 thoughts: 49 Thoughts: Okay, let's break this down. Investigating the `sp_pci_driver` Right, so `sp_pci_driver`… that's got to be for dealing with AMD PCI devices. Specifically, the AMD Cryptographic Coprocessor and the Platform Security Processor. Given my experience, the naming convention feels right, and those are common targets for a PCI driver like this. Where do I even start looking for information about how this driver works? Time to dive into the kernel source tree. Let me check the obvious place, since it is a PCI driver: `drivers/crypto/ccp/sp-pci.c`. Hopefully, that file will give me the lowdown on how the driver interfaces with those devices.
24/2	2026/09/18 16:03	tool	read-file	0m Args: { "File": "drivers/crypto/ccp/sp-pci.c", "FirstLine": 480, "LineCount": 40 } Results: { "Contents": " 480:\t#endif\n 481:\t\n 482:\tstatic const struct sp_dev_vdata dev_vdata[] = {\n 483:\t\t{\t/* 0 /\n 484:\t\t\t.bar = 2,\n 485:\t#ifdef CONFIG_CRYPTO_DEV_SP_CCP\n 486:\t\t\t.ccp_vdata = \u0026ccpv3,\n 487:\t#endif\n 488:\t\t},\n 489:\t\t{\t/ 1 /\n 490:\t\t\t.bar = 2,\n 491:\t#ifdef CONFIG_CRYPTO_DEV_SP_CCP\n 492:\t\t\t.ccp_vdata = \u0026ccpv5a,\n 493:\t#endif\n 494:\t#ifdef CONFIG_CRYPTO_DEV_SP_PSP\n 495:\t\t\t.psp_vdata = \u0026pspv1,\n 496:\t#endif\n 497:\t\t},\n 498:\t\t{\t/ 2 /\n 499:\t\t\t.bar = 2,\n 500:\t#ifdef CONFIG_CRYPTO_DEV_SP_CCP\n 501:\t\t\t.ccp_vdata = \u0026ccpv5b,\n 502:\t#endif\n 503:\t\t},\n 504:\t\t{\t/ 3 /\n 505:\t\t\t.bar = 2,\n 506:\t#ifdef CONFIG_CRYPTO_DEV_SP_CCP\n 507:\t\t\t.ccp_vdata = \u0026ccpv5a,\n 508:\t#endif\n 509:\t#ifdef CONFIG_CRYPTO_DEV_SP_PSP\n 510:\t\t\t.psp_vdata = \u0026pspv2,\n 511:\t#endif\n 512:\t\t},\n 513:\t\t{\t/ 4 */\n 514:\t\t\t.bar = 2,\n 515:\t#ifdef CONFIG_CRYPTO_DEV_SP_CCP\n 516:\t\t\t.ccp_vdata = \u0026ccpv5a,\n 517:\t#endif\n 518:\t#ifdef CONFIG_CRYPTO_DEV_SP_PSP\n 519:\t\t\t.psp_vdata = \u0026pspv3,\n" }
25/2	2026/09/18 16:03	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 31494 output: 21 thoughts: 1162 Thoughts: Analyzing SEV-SNP Support in Virtualized Environments Okay, let's break this down from a kernel perspective. I'm focusing on SEV-SNP (Secure Encrypted Virtualization with Secure Nested Paging) on AMD processors, specifically how it's handled when virtualized, as opposed to running natively. The core issue revolves around the presence, or lack thereof, of the AMD Platform Security Processor (PSP) or Control Co-Processor (CCP) hardware, and its implications on the Linux kernel's initialization. First, QEMU, as far as I know, doesn't emulate the necessary AMD PSP/CCP PCI device. Even if it did, the function calls `snp_probe_rmptable_info` and `bsp_determine_snp` would encounter roadblocks. Let's trace it through the relevant code in `arch/x86/kernel/cpu/amd.c`. The key conditional here hinges on `!cpu_has(c, X86_FEATURE_HYPERVISOR)`. In a virtual environment, this is always going to evaluate to false because the hypervisor feature flag is set. Consequently, the `CC_ATTR_HOST_SEV_SNP` attribute is cleared. This has a cascading effect: * The `rmpopt_capable()` function becomes false. * `snp_enable_rmpopt()` essentially does nothing. * `__sev_snp_init_locked` returns `-ENODEV` (device not found). * `snp_prepare()` and `snp_shutdown()` are never called. * In KVM, `sev_snp_supported` is evaluated as `false` because `cc_platform_has(CC_ATTR_HOST_SEV_SNP)` is false. This means I can't even create SNP VMs in this virtualized context. * The `rmpopt_init()` function can't run, because `cpu_feature_enabled(X86_FEATURE_RMPOPT)` evaluates to false. This is because RMPOPT is a Zen 5/6 instruction, which is not emulated in the virtualized environment. Now, let's dig into RMPOPT and CPUID leaf 0x80000025. It looks like RMPOPT is a new instruction for Zen 5/6 CPUs that is not emulated or even supported by the current standard virtualization layers. But even if QEMU or some other virtual machine did set the necessary CPUID leaf, the `snp_probe_rmptable_info()` function includes a crucial check at boot time for segmented RMP (Remote Memory Partitioning) support in the firmware MSRs. If the firmware doesn't support segmented RMP, or if it's disabled, the code explicitly clears the `X86_FEATURE_RMPOPT` feature flag using `setup_clear_cpu_cap(X86_FEATURE_RMPOPT)`. This effectively disables RMPOPT before `rmpopt_init` even gets a chance to run. Finally, consider `snp_rmptable_init()`. This is an `__init` function called at boot time. The function itself also depends on `cc_platform_has(CC_ATTR_HOST_SEV_SNP)`. This check is performed, and results in `-ENOSYS` being returned. This all points to a fundamental issue: SEV-SNP relies on specific hardware (PSP/CCP) features that are not emulated and that the kernel actively disables when running in a standard virtualized environment. The RMPOPT instruction and related functionality are currently beyond the scope of emulation, and the configuration and boot-time checks ensure that these features are not activated. Now, where is `snp_rmptable_init()` called? That is something I'd need to confirm, but this all seems quite consistent with the architecture of SEV-SNP.
26/2	2026/09/18 16:03	tool	grepper	0m Args: { "Expression": "snp_rmptable_init" } Results: { "Output": "arch/x86/include/asm/sev.h=650=bool snp_probe_rmptable_info(void);\narch/x86/include/asm/sev.h:651:int snp_rmptable_init(void);\narch/x86/include/asm/sev.h-652-int snp_lookup_rmpentry(u64 pfn, bool assigned, int level);\n--\narch/x86/include/asm/sev.h=668=static inline bool snp_probe_rmptable_info(void) { return false; }\narch/x86/include/asm/sev.h:669:static inline int snp_rmptable_init(void) { return -ENOSYS; }\narch/x86/include/asm/sev.h-670-static inline int snp_lookup_rmpentry(u64 pfn, bool assigned, int level) { return -ENODEV; }\n--\narch/x86/virt/svm/sev.c=705=EXPORT_SYMBOL_FOR_MODULES(snp_enable_rmpopt, \"ccp,kvm-amd\");\n--\narch/x86/virt/svm/sev.c-711- /\narch/x86/virt/svm/sev.c:712:int __init snp_rmptable_init(void)\narch/x86/virt/svm/sev.c-713-{\n--\ndrivers/iommu/amd/init.c=3395=static __init void iommu_snp_enable(void)\n--\ndrivers/iommu/amd/init.c-3432-\t /\ndrivers/iommu/amd/init.c:3433:\tif (snp_rmptable_init()) {\ndrivers/iommu/amd/init.c-3434-\t\tpr_warn(\"SNP: RMP initialization failed, SNP cannot be supported.\\n\");\n" }
27/2	2026/09/18 16:03	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 34030 output: 23 thoughts: 506 Thoughts: Analyzing the SNP RMP Table Initialization Okay, so I'm digging into this SNP RMP table initialization, specifically how `snp_rmptable_init()` gets called. I see it's triggered within `iommu_snp_enable()`, which is in `drivers/iommu/amd/init.c`. The first thing that jumps out is the conditional check using `cc_platform_has(CC_ATTR_HOST_SEV_SNP)`. If that check fails, the function immediately returns. Seems straightforward, a simple gatekeeper for systems without the necessary SEV-SNP support. But then, my expert mind kicks in. I need to be thorough. I recall that `snp_rmptable_init()` contains a call to `cpu_hotplug_disable()`. I need to figure out when this is called. I need to know where I can prevent it from happening. I see that this call is guarded by a check for the `MSR_AMD64_SYSCFG_SNP_EN` bit. And before that, there's another check for `cc_platform_has(CC_ATTR_HOST_SEV_SNP)` in `snp_rmptable_init()`. The way it's written now, this code path will never be reached because of the earlier guard in `iommu_snp_enable()`. Alright, I need to zoom out. Let's trace `snp_probe_rmptable_info()` because that must be the starting point for all this. Where is that called? Ah, it's called inside `bsp_determine_snp()`. The conditional there is interesting: it only calls `snp_probe_rmptable_info()` if the CPU doesn't have the `X86_FEATURE_HYPERVISOR` feature AND it has either Zen3, Zen4, or RMPREAD features. So, the presence of a hypervisor immediately short-circuits the call to `snp_probe_rmptable_info()`. I need to check to see if there are other callers though!
28/2	2026/09/18 16:03	tool	grepper	0m Args: { "Expression": "snp_probe_rmptable_info" } Results: { "Output": "arch/x86/include/asm/sev.h=645=static inline u64 savic_ghcb_msr_read(u32 reg) { return 0; }\n--\narch/x86/include/asm/sev.h-649-#ifdef CONFIG_KVM_AMD_SEV\narch/x86/include/asm/sev.h:650:bool snp_probe_rmptable_info(void);\narch/x86/include/asm/sev.h-651-int snp_rmptable_init(void);\n--\narch/x86/include/asm/sev.h=666=void snp_shutdown(void);\narch/x86/include/asm/sev.h-667-#else\narch/x86/include/asm/sev.h:668:static inline bool snp_probe_rmptable_info(void) { return false; }\narch/x86/include/asm/sev.h-669-static inline int snp_rmptable_init(void) { return -ENOSYS; }\n--\narch/x86/kernel/cpu/amd.c=356=static void bsp_determine_snp(struct cpuinfo_x86 *c)\n--\narch/x86/kernel/cpu/amd.c-372-\t\t cpu_feature_enabled(X86_FEATURE_RMPREAD)) \u0026\u0026\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);\n--\narch/x86/virt/svm/sev.c=785=static bool probe_segmented_rmptable_info(void)\n--\narch/x86/virt/svm/sev.c-828-\narch/x86/virt/svm/sev.c:829:bool snp_probe_rmptable_info(void)\narch/x86/virt/svm/sev.c-830-{\n" }
29/2	2026/09/18 16:03	llm	patch-evaluator	2m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 35555 output: 234 thoughts: 959 Thoughts: SEV-SNP Host Code Unreachability in Standard Virtualized Environments Okay, let's break this down. My analysis indicates that the `snp_probe_rmptable_info()` function is solely called within `bsp_determine_snp()`. Crucially, this call is protected by a check for `X86_FEATURE_HYPERVISOR`. In any virtualized environment I'm familiar with, like QEMU, KVM, or GCE, `cpu_has(c, X86_FEATURE_HYPERVISOR)` will always evaluate to true. Therefore, `snp_probe_rmptable_info()` never executes under these circumstances. This has a cascading effect. Because the initial function does not execute, the following never get called: `CC_ATTR_HOST_SEV_SNP` is never set, `snp_rmptable_init()`, `snp_prepare()`, and `snp_shutdown()` are never executed. `snp_enable_rmpopt()` either won't be called, or will immediately return, as `sev_vm_destroy()` will always evaluate to `false`, and `__sev_snp_init_locked()` will never be reached. Furthermore, `rmpopt_init()` checks for `X86_FEATURE_RMPOPT`, which is not supported in these emulated environments and returns 0 without doing anything, and the functions `do_rmpopt_work()`, `rmpopt_scan_range()`, and `rmpopt()` are never executed. So, the next question is if any SEV-SNP host code is ever executed through syzkaller or standard QEMU. Analyzing section 2 of the prompt confirms that specific AMD SEV-SNP host operations require bare-metal hardware with SEV-SNP enabled by the firmware and the AMD Secure Processor. This includes support for the AMD RMPOPT instruction and host-side RMP optimization. In standard virtualized fuzzing environments (QEMU or GCE), this is not possible: 1. `X86_FEATURE_HYPERVISOR` is always active in QEMU/GCE, disabling SEV-SNP host support by preventing `CC_ATTR_HOST_SEV_SNP` from being set. 2. The RMPOPT feature, segmented RMP, and the AMD Secure Processor (PSP) are physical processor features not emulated by QEMU or nested virtualization in GCE. 3. Every entry point modified by the patch series is guarded either by `X86_FEATURE_RMPOPT`, `CC_ATTR_HOST_SEV_SNP`, or `KVM_X86_SNP_VM`, all of which are structurally unreachable in QEMU/GCE. Therefore, this code path is functionally dead in the target fuzzing environments. My conclusion is that this is not worth fuzzing. I've double-checked all relevant details: WorthFuzzing: false, FocusSymbols: [], EnableConfigs: []. This aligns with my understanding and the kernel source code. I'm ready to `set-results`.
30/2	2026/09/18 16:06	tool	set-results	0m Args: { "EnableConfigs": [], "FocusSymbols": [], "Reasoning": "The patch series adds support for the AMD RMPOPT CPU feature/instruction and manages RMP optimizations during AMD SEV-SNP host operations. These code paths are structurally unreachable in standard virtualized fuzzing environments (QEMU / GCE): SEV-SNP host support requires physical AMD hardware with Platform Security Processor (PSP/CCP) and firmware-configured RMP tables, and the kernel explicitly skips enabling SEV-SNP host capabilities (CC_ATTR_HOST_SEV_SNP) whenever running under a hypervisor (X86_FEATURE_HYPERVISOR). Furthermore, the RMPOPT CPU feature (CPUID 0x80000025) and instruction are not emulated by QEMU. Consequently, all modified functions and branches (including snp_enable_rmpopt, rmpopt_init, snp_prepare, snp_shutdown, and KVM SNP destruction hooks) cannot be reached or exercised during fuzzing.", "WorthFuzzing": false } Results: { "EnableConfigs": null, "FocusSymbols": [], "Reasoning": "The patch series adds support for the AMD RMPOPT CPU feature/instruction and manages RMP optimizations during AMD SEV-SNP host operations. These code paths are structurally unreachable in standard virtualized fuzzing environments (QEMU / GCE): SEV-SNP host support requires physical AMD hardware with Platform Security Processor (PSP/CCP) and firmware-configured RMP tables, and the kernel explicitly skips enabling SEV-SNP host capabilities (CC_ATTR_HOST_SEV_SNP) whenever running under a hypervisor (X86_FEATURE_HYPERVISOR). Furthermore, the RMPOPT CPU feature (CPUID 0x80000025) and instruction are not emulated by QEMU. Consequently, all modified functions and branches (including snp_enable_rmpopt, rmpopt_init, snp_prepare, snp_shutdown, and KVM SNP destruction hooks) cannot be reached or exercised during fuzzing.", "WorthFuzzing": false }
31/1	2026/09/18 16:06	action	If	0m Args: { "WorthFuzzing": false } Results: null

LLM Calls Summary:
Total Calls	Total Tokens	Avg Tokens	Total Duration (Seconds)	Avg Duration (Seconds)

Tool Calls Summary:
Total Calls	Total Duration (Seconds)	Avg Duration (Seconds)