AI Trajectory

null

{
  "EnableConfigs": [
    "KVM",
    "KVM_AMD_SEV",
    "KVM_SW_PROTECTED_VM"
  ],
  "FocusSymbols": [
    "kvm_gmem_get_pfn",
    "sev_handle_rmp_fault"
  ],
  "KMSANReasoning": "The patch modifies `kvm_gmem_get_pfn` to no longer return a `struct page` pointer to the caller, instead dropping the folio reference immediately within the function. It updates various callers across arm64 and x86 KVM code to remove the `page` argument and associated cleanup calls (e.g., `kvm_release_faultin_page`, `kvm_release_page_clean`). Additionally, it adds MMU sequence checking (`mmu_invalidate_retry_gfn`) in `sev_handle_rmp_fault` to fix a race condition during RMP faults.\n\nThese changes are purely refactoring of page reference management and concurrency fixes. They do not introduce new data structures sent to user space, do not add conditional logic depending on uninitialized variables, and do not alter bounds checking in a way that exposes uninitialized memory. Any potential bugs introduced by these changes (such as premature page freeing or race conditions) would manifest as use-after-free, NULL pointer dereferences, or memory corruption, which are effectively caught by standard KASAN and LOCKDEP. There is no risk of uninitialized memory usage or info-leaks that would necessitate a dedicated KMSAN fuzzing session.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch modifies the memory management of KVM guest_memfd by dropping the folio reference inside `kvm_gmem_get_pfn` instead of returning the page to the caller to be released later. It updates the callers in x86 (MMU and SEV-SNP) and ARM64 (MMU and nested) to accommodate this signature change and adds MMU sequence counter checks in `sev_handle_rmp_fault` to handle invalidation races. These are functional changes to core KVM and confidential computing memory management, which are reachable from userspace by running a KVM guest utilizing guest_memfd.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 8c7d409071d310bcf22a130824d2685dae024314\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Thu Aug 20 23:49:58 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c\nindex 6c941aaa10c63..d5aa197d2cbfd 100644\n--- a/arch/arm64/kvm/mmu.c\n+++ b/arch/arm64/kvm/mmu.c\n@@ -1613,7 +1613,6 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)\n \tenum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;\n \tstruct kvm_pgtable *pgt = s2fd-\u003evcpu-\u003earch.hw_mmu-\u003epgt;\n \tunsigned long mmu_seq;\n-\tstruct page *page;\n \tstruct kvm *kvm = s2fd-\u003evcpu-\u003ekvm;\n \tvoid *memcache = NULL;\n \tkvm_pfn_t pfn;\n@@ -1641,7 +1640,7 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)\n \t/* Pairs with the smp_wmb() in kvm_mmu_invalidate_end(). */\n \tsmp_rmb();\n \n-\tret = kvm_gmem_get_pfn(kvm, s2fd-\u003ememslot, gfn, \u0026pfn, \u0026page, NULL);\n+\tret = kvm_gmem_get_pfn(kvm, s2fd-\u003ememslot, gfn, \u0026pfn, NULL);\n \tif (ret) {\n \t\tkvm_prepare_memory_fault_exit(s2fd-\u003evcpu, s2fd-\u003efault_ipa, PAGE_SIZE,\n \t\t\t\t\t      write_fault, exec_fault, false);\n@@ -1681,7 +1680,6 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)\n \t}\n \n out_unlock:\n-\tkvm_release_faultin_page(kvm, page, !!ret, prot \u0026 KVM_PGTABLE_PROT_W);\n \tkvm_fault_unlock(kvm);\n \n \tif ((prot \u0026 KVM_PGTABLE_PROT_W) \u0026\u0026 !ret)\ndiff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c\nindex fb54f6dad995c..43523bb17621a 100644\n--- a/arch/arm64/kvm/nested.c\n+++ b/arch/arm64/kvm/nested.c\n@@ -1360,7 +1360,7 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)\n \tbool write_fault, writable;\n \tunsigned long mmu_seq;\n \tstruct vncr_tlb *vt;\n-\tstruct page *page;\n+\tstruct page *page = NULL;\n \tu64 va, pfn, gfn;\n \tint ret;\n \n@@ -1411,7 +1411,7 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)\n \t\tif (is_error_noslot_pfn(pfn) || (write_fault \u0026\u0026 !writable))\n \t\t\treturn -EFAULT;\n \t} else {\n-\t\tret = kvm_gmem_get_pfn(vcpu-\u003ekvm, memslot, gfn, \u0026pfn, \u0026page, NULL);\n+\t\tret = kvm_gmem_get_pfn(vcpu-\u003ekvm, memslot, gfn, \u0026pfn, NULL);\n \t\tif (ret) {\n \t\t\tkvm_prepare_memory_fault_exit(vcpu, vt-\u003ewr.pa, PAGE_SIZE,\n \t\t\t\t\t      write_fault, false, false);\ndiff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c\nindex c519e8e8d646f..129d403308051 100644\n--- a/arch/x86/kvm/mmu/mmu.c\n+++ b/arch/x86/kvm/mmu/mmu.c\n@@ -4604,7 +4604,7 @@ static int kvm_mmu_faultin_pfn_gmem(struct kvm_vcpu *vcpu,\n \t}\n \n \tr = kvm_gmem_get_pfn(vcpu-\u003ekvm, fault-\u003eslot, fault-\u003egfn, \u0026fault-\u003epfn,\n-\t\t\t     \u0026fault-\u003erefcounted_page, \u0026max_order);\n+\t\t\t     \u0026max_order);\n \tif (r) {\n \t\tkvm_mmu_prepare_memory_fault_exit(vcpu, fault);\n \t\treturn r;\ndiff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c\nindex fcb41dfde4c02..0c91c904573cc 100644\n--- a/arch/x86/kvm/svm/sev.c\n+++ b/arch/x86/kvm/svm/sev.c\n@@ -4016,7 +4016,6 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)\n \tstruct kvm *kvm = vcpu-\u003ekvm;\n \tgfn_t gfn = gpa_to_gfn(gpa);\n \tunsigned long mmu_seq;\n-\tstruct page *page;\n \tkvm_pfn_t pfn;\n \n \tlockdep_assert_held(\u0026svm-\u003esev_es.snp_vmsa_mutex);\n@@ -4060,7 +4059,7 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)\n \t * The new VMSA will be private memory guest memory, so retrieve the\n \t * PFN from the gmem backend.\n \t */\n-\tif (kvm_gmem_get_pfn(vcpu-\u003ekvm, slot, gfn, \u0026pfn, \u0026page, NULL))\n+\tif (kvm_gmem_get_pfn(vcpu-\u003ekvm, slot, gfn, \u0026pfn, NULL))\n \t\treturn;\n \n \tread_lock(\u0026kvm-\u003emmu_lock);\n@@ -4076,8 +4075,6 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)\n \telse\n \t\tsvm-\u003evmcb-\u003econtrol.vmsa_pa = pfn_to_hpa(pfn);\n \tread_unlock(\u0026kvm-\u003emmu_lock);\n-\n-\tkvm_release_page_clean(page);\n }\n \n /*\n@@ -5003,7 +5000,7 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)\n \tstruct kvm_memory_slot *slot;\n \tstruct kvm *kvm = vcpu-\u003ekvm;\n \tint order, rmp_level, ret;\n-\tstruct page *page;\n+\tunsigned long mmu_seq;\n \tbool assigned;\n \tkvm_pfn_t pfn;\n \tgfn_t gfn;\n@@ -5030,7 +5027,10 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)\n \t\treturn;\n \t}\n \n-\tret = kvm_gmem_get_pfn(kvm, slot, gfn, \u0026pfn, \u0026page, \u0026order);\n+\tmmu_seq = kvm-\u003emmu_invalidate_seq;\n+\tsmp_rmb();\n+\n+\tret = kvm_gmem_get_pfn(kvm, slot, gfn, \u0026pfn, \u0026order);\n \tif (ret) {\n \t\tpr_warn_ratelimited(\"SEV: Unexpected RMP fault, no backing page for private GPA 0x%llx\\n\",\n \t\t\t\t    gpa);\n@@ -5039,9 +5039,13 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)\n \n \tret = snp_lookup_rmpentry(pfn, \u0026assigned, \u0026rmp_level);\n \tif (ret || !assigned) {\n-\t\tpr_warn_ratelimited(\"SEV: Unexpected RMP fault, no assigned RMP entry found for GPA 0x%llx PFN 0x%llx error %d\\n\",\n-\t\t\t\t    gpa, pfn, ret);\n-\t\tgoto out_no_trace;\n+\t\tguard(read_lock)(\u0026kvm-\u003emmu_lock);\n+\n+\t\tif (!mmu_invalidate_retry_gfn(kvm, mmu_seq, gfn))\n+\t\t\tpr_warn_ratelimited(\"SEV: Unexpected RMP fault, no assigned RMP entry found for GPA 0x%llx PFN 0x%llx error %d\\n\",\n+\t\t\t\t\t    gpa, pfn, ret);\n+\n+\t\treturn;\n \t}\n \n \t/*\n@@ -5069,26 +5073,31 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)\n \tif (rmp_level == PG_LEVEL_4K)\n \t\tgoto out;\n \n-\tret = snp_rmptable_psmash(pfn);\n-\tif (ret) {\n-\t\t/*\n-\t\t * Look it up again. If it's 4K now then the PSMASH may have\n-\t\t * raced with another process and the issue has already resolved\n-\t\t * itself.\n-\t\t */\n-\t\tif (!snp_lookup_rmpentry(pfn, \u0026assigned, \u0026rmp_level) \u0026\u0026\n-\t\t    assigned \u0026\u0026 rmp_level == PG_LEVEL_4K)\n+\tscoped_guard(read_lock, \u0026kvm-\u003emmu_lock) {\n+\t\tif (mmu_invalidate_retry_gfn(kvm, mmu_seq, gfn))\n \t\t\tgoto out;\n \n-\t\tpr_warn_ratelimited(\"SEV: Unable to split RMP entry for GPA 0x%llx PFN 0x%llx ret %d\\n\",\n-\t\t\t\t    gpa, pfn, ret);\n+\t\tret = snp_rmptable_psmash(pfn);\n+\t\tif (ret) {\n+\t\t\t/*\n+\t\t\t * Look it up again. If it's 4K now then the PSMASH may\n+\t\t\t * have raced with another process and the issue has\n+\t\t\t * already resolved itself. If it's not assigned, then\n+\t\t\t * this must have raced with another process that made\n+\t\t\t * this page shared.\n+\t\t\t */\n+\t\t\tif (!snp_lookup_rmpentry(pfn, \u0026assigned, \u0026rmp_level) \u0026\u0026\n+\t\t\t    ((assigned \u0026\u0026 rmp_level == PG_LEVEL_4K) || !assigned))\n+\t\t\t\tgoto out;\n+\n+\t\t\tpr_warn_ratelimited(\"SEV: Unable to split RMP entry for GPA 0x%llx PFN 0x%llx ret %d\\n\",\n+\t\t\t\t\t    gpa, pfn, ret);\n+\t\t}\n \t}\n \n \tkvm_zap_gfn_range(kvm, gfn, gfn + PTRS_PER_PMD);\n out:\n \ttrace_kvm_rmp_fault(vcpu, gpa, pfn, error_code, rmp_level, ret);\n-out_no_trace:\n-\tkvm_release_page_unused(page);\n }\n \n static bool is_pfn_range_shared(kvm_pfn_t start, kvm_pfn_t end)\ndiff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h\nindex 03bfc92864b6e..502465119ca0c 100644\n--- a/include/linux/kvm_host.h\n+++ b/include/linux/kvm_host.h\n@@ -2586,13 +2586,11 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)\n \n #ifdef CONFIG_KVM_GUEST_MEMFD\n int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,\n-\t\t     gfn_t gfn, kvm_pfn_t *pfn, struct page **page,\n-\t\t     int *max_order);\n+\t\t     gfn_t gfn, kvm_pfn_t *pfn, int *max_order);\n #else\n static inline int kvm_gmem_get_pfn(struct kvm *kvm,\n \t\t\t\t   struct kvm_memory_slot *slot, gfn_t gfn,\n-\t\t\t\t   kvm_pfn_t *pfn, struct page **page,\n-\t\t\t\t   int *max_order)\n+\t\t\t\t   kvm_pfn_t *pfn, int *max_order)\n {\n \tKVM_BUG_ON(1, kvm);\n \treturn -EIO;\ndiff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c\nindex b596486d184ca..589762140c3ef 100644\n--- a/virt/kvm/guest_memfd.c\n+++ b/virt/kvm/guest_memfd.c\n@@ -751,8 +751,7 @@ static struct folio *__kvm_gmem_get_pfn(struct file *file,\n }\n \n int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,\n-\t\t     gfn_t gfn, kvm_pfn_t *pfn, struct page **page,\n-\t\t     int *max_order)\n+\t\t     gfn_t gfn, kvm_pfn_t *pfn, int *max_order)\n {\n \tpgoff_t index = kvm_gmem_get_index(slot, gfn);\n \tstruct folio *folio;\n@@ -780,11 +779,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,\n #endif\n \n \tfolio_unlock(folio);\n-\n-\tif (!r)\n-\t\t*page = folio_file_page(folio, index);\n-\telse\n-\t\tfolio_put(folio);\n+\tfolio_put(folio);\n \n \treturn r;\n }\n"
}

best-expensive

null

{
  "EnableConfigs": [
    "KVM",
    "KVM_AMD_SEV",
    "KVM_SW_PROTECTED_VM"
  ],
  "FocusSymbols": [
    "kvm_gmem_get_pfn",
    "sev_handle_rmp_fault"
  ],
  "Reasoning": "The patch modifies the memory management of KVM guest_memfd by dropping the folio reference inside `kvm_gmem_get_pfn` instead of returning the page to the caller to be released later. It updates the callers in x86 (MMU and SEV-SNP) and ARM64 (MMU and nested) to accommodate this signature change and adds MMU sequence counter checks in `sev_handle_rmp_fault` to handle invalidation races. These are functional changes to core KVM and confidential computing memory management, which are reachable from userspace by running a KVM guest utilizing guest_memfd.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
  even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).
- Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed,
  ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU.
- Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove)
  that are executed only during PCI hot-unplug or sysfs driver unbind operations.

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
   Prefer non-static, non-inlined API entrypoint functions over internal static helper functions
   (which are inlined by the compiler and do not have distinct symbol addresses).
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs
   needed for Kbuild to compile the code statically into vmlinux. List them in the EnableConfigs
   output array, and DO NOT add a '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.

For your convenience, here is the diff of the changes:
commit 8c7d409071d310bcf22a130824d2685dae024314
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Aug 20 23:49:58 2026 +0000

    syz-cluster: applied patch under review

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 6c941aaa10c63..d5aa197d2cbfd 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1613,7 +1613,6 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)
 	enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
 	struct kvm_pgtable *pgt = s2fd->vcpu->arch.hw_mmu->pgt;
 	unsigned long mmu_seq;
-	struct page *page;
 	struct kvm *kvm = s2fd->vcpu->kvm;
 	void *memcache = NULL;
 	kvm_pfn_t pfn;
@@ -1641,7 +1640,7 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)
 	/* Pairs with the smp_wmb() in kvm_mmu_invalidate_end(). */
 	smp_rmb();
 
-	ret = kvm_gmem_get_pfn(kvm, s2fd->memslot, gfn, &pfn, &page, NULL);
+	ret = kvm_gmem_get_pfn(kvm, s2fd->memslot, gfn, &pfn, NULL);
 	if (ret) {
 		kvm_prepare_memory_fault_exit(s2fd->vcpu, s2fd->fault_ipa, PAGE_SIZE,
 					      write_fault, exec_fault, false);
@@ -1681,7 +1680,6 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)
 	}
 
 out_unlock:
-	kvm_release_faultin_page(kvm, page, !!ret, prot & KVM_PGTABLE_PROT_W);
 	kvm_fault_unlock(kvm);
 
 	if ((prot & KVM_PGTABLE_PROT_W) && !ret)
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index fb54f6dad995c..43523bb17621a 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -1360,7 +1360,7 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)
 	bool write_fault, writable;
 	unsigned long mmu_seq;
 	struct vncr_tlb *vt;
-	struct page *page;
+	struct page *page = NULL;
 	u64 va, pfn, gfn;
 	int ret;
 
@@ -1411,7 +1411,7 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)
 		if (is_error_noslot_pfn(pfn) || (write_fault && !writable))
 			return -EFAULT;
 	} else {
-		ret = kvm_gmem_get_pfn(vcpu->kvm, memslot, gfn, &pfn, &page, NULL);
+		ret = kvm_gmem_get_pfn(vcpu->kvm, memslot, gfn, &pfn, NULL);
 		if (ret) {
 			kvm_prepare_memory_fault_exit(vcpu, vt->wr.pa, PAGE_SIZE,
 					      write_fault, false, false);
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index c519e8e8d646f..129d403308051 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4604,7 +4604,7 @@ static int kvm_mmu_faultin_pfn_gmem(struct kvm_vcpu *vcpu,
 	}
 
 	r = kvm_gmem_get_pfn(vcpu->kvm, fault->slot, fault->gfn, &fault->pfn,
-			     &fault->refcounted_page, &max_order);
+			     &max_order);
 	if (r) {
 		kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
 		return r;
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index fcb41dfde4c02..0c91c904573cc 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4016,7 +4016,6 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)
 	struct kvm *kvm = vcpu->kvm;
 	gfn_t gfn = gpa_to_gfn(gpa);
 	unsigned long mmu_seq;
-	struct page *page;
 	kvm_pfn_t pfn;
 
 	lockdep_assert_held(&svm->sev_es.snp_vmsa_mutex);
@@ -4060,7 +4059,7 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)
 	 * The new VMSA will be private memory guest memory, so retrieve the
 	 * PFN from the gmem backend.
 	 */
-	if (kvm_gmem_get_pfn(vcpu->kvm, slot, gfn, &pfn, &page, NULL))
+	if (kvm_gmem_get_pfn(vcpu->kvm, slot, gfn, &pfn, NULL))
 		return;
 
 	read_lock(&kvm->mmu_lock);
@@ -4076,8 +4075,6 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)
 	else
 		svm->vmcb->control.vmsa_pa = pfn_to_hpa(pfn);
 	read_unlock(&kvm->mmu_lock);
-
-	kvm_release_page_clean(page);
 }
 
 /*
@@ -5003,7 +5000,7 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
 	struct kvm_memory_slot *slot;
 	struct kvm *kvm = vcpu->kvm;
 	int order, rmp_level, ret;
-	struct page *page;
+	unsigned long mmu_seq;
 	bool assigned;
 	kvm_pfn_t pfn;
 	gfn_t gfn;
@@ -5030,7 +5027,10 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
 		return;
 	}
 
-	ret = kvm_gmem_get_pfn(kvm, slot, gfn, &pfn, &page, &order);
+	mmu_seq = kvm->mmu_invalidate_seq;
+	smp_rmb();
+
+	ret = kvm_gmem_get_pfn(kvm, slot, gfn, &pfn, &order);
 	if (ret) {
 		pr_warn_ratelimited("SEV: Unexpected RMP fault, no backing page for private GPA 0x%llx\n",
 				    gpa);
@@ -5039,9 +5039,13 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
 
 	ret = snp_lookup_rmpentry(pfn, &assigned, &rmp_level);
 	if (ret || !assigned) {
-		pr_warn_ratelimited("SEV: Unexpected RMP fault, no assigned RMP entry found for GPA 0x%llx PFN 0x%llx error %d\n",
-				    gpa, pfn, ret);
-		goto out_no_trace;
+		guard(read_lock)(&kvm->mmu_lock);
+
+		if (!mmu_invalidate_retry_gfn(kvm, mmu_seq, gfn))
+			pr_warn_ratelimited("SEV: Unexpected RMP fault, no assigned RMP entry found for GPA 0x%llx PFN 0x%llx error %d\n",
+					    gpa, pfn, ret);
+
+		return;
 	}
 
 	/*
@@ -5069,26 +5073,31 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
 	if (rmp_level == PG_LEVEL_4K)
 		goto out;
 
-	ret = snp_rmptable_psmash(pfn);
-	if (ret) {
-		/*
-		 * Look it up again. If it's 4K now then the PSMASH may have
-		 * raced with another process and the issue has already resolved
-		 * itself.
-		 */
-		if (!snp_lookup_rmpentry(pfn, &assigned, &rmp_level) &&
-		    assigned && rmp_level == PG_LEVEL_4K)
+	scoped_guard(read_lock, &kvm->mmu_lock) {
+		if (mmu_invalidate_retry_gfn(kvm, mmu_seq, gfn))
 			goto out;
 
-		pr_warn_ratelimited("SEV: Unable to split RMP entry for GPA 0x%llx PFN 0x%llx ret %d\n",
-				    gpa, pfn, ret);
+		ret = snp_rmptable_psmash(pfn);
+		if (ret) {
+			/*
+			 * Look it up again. If it's 4K now then the PSMASH may
+			 * have raced with another process and the issue has
+			 * already resolved itself. If it's not assigned, then
+			 * this must have raced with another process that made
+			 * this page shared.
+			 */
+			if (!snp_lookup_rmpentry(pfn, &assigned, &rmp_level) &&
+			    ((assigned && rmp_level == PG_LEVEL_4K) || !assigned))
+				goto out;
+
+			pr_warn_ratelimited("SEV: Unable to split RMP entry for GPA 0x%llx PFN 0x%llx ret %d\n",
+					    gpa, pfn, ret);
+		}
 	}
 
 	kvm_zap_gfn_range(kvm, gfn, gfn + PTRS_PER_PMD);
 out:
 	trace_kvm_rmp_fault(vcpu, gpa, pfn, error_code, rmp_level, ret);
-out_no_trace:
-	kvm_release_page_unused(page);
 }
 
 static bool is_pfn_range_shared(kvm_pfn_t start, kvm_pfn_t end)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 03bfc92864b6e..502465119ca0c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2586,13 +2586,11 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
 
 #ifdef CONFIG_KVM_GUEST_MEMFD
 int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
-		     gfn_t gfn, kvm_pfn_t *pfn, struct page **page,
-		     int *max_order);
+		     gfn_t gfn, kvm_pfn_t *pfn, int *max_order);
 #else
 static inline int kvm_gmem_get_pfn(struct kvm *kvm,
 				   struct kvm_memory_slot *slot, gfn_t gfn,
-				   kvm_pfn_t *pfn, struct page **page,
-				   int *max_order)
+				   kvm_pfn_t *pfn, int *max_order)
 {
 	KVM_BUG_ON(1, kvm);
 	return -EIO;
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index b596486d184ca..589762140c3ef 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -751,8 +751,7 @@ static struct folio *__kvm_gmem_get_pfn(struct file *file,
 }
 
 int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
-		     gfn_t gfn, kvm_pfn_t *pfn, struct page **page,
-		     int *max_order)
+		     gfn_t gfn, kvm_pfn_t *pfn, int *max_order)
 {
 	pgoff_t index = kvm_gmem_get_index(slot, gfn);
 	struct folio *folio;
@@ -780,11 +779,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
 #endif
 
 	folio_unlock(folio);
-
-	if (!r)
-		*page = folio_file_page(folio, index);
-	else
-		folio_put(folio);
+	folio_put(folio);
 
 	return r;
 }

gemini-3.1-pro-preview

null

null

							input: 5611
							output: 23
							thoughts: 771
						

**Analyzing the kvm_gmem_get_pfn Patch**

Okay, so this patch is a pretty significant change to `kvm_gmem_get_pfn`. It's removing the `struct page **page` parameter, which is a classic indicator of a reference count change. Essentially, the code used to take a reference to the `struct page` (folio, in modern terms) and release it later using `kvm_release_faultin_page`, `kvm_release_page_clean`, or `kvm_release_page_unused`. Now, `kvm_gmem_get_pfn` is responsible for calling `folio_put()` directly after `folio_unlock()`, right in `virt/kvm/guest_memfd.c`.

My initial thought is, this needs a thorough check for reachability and fuzzability. This is core guest_memfd functionality, directly involved in confidential computing contexts like SEV-SNP, TDX, and ARM CCA. This function is triggered during page faults for private memory, so the impact is potentially high.

The core of the change is how the folio's reference count is managed. Previously, the caller held a reference, which gave them control over the page's lifecycle. Now, `kvm_gmem_get_pfn` *immediately* releases that reference. This begs the question: how does the caller safely *use* the physical frame number (PFN) it gets back? If the function immediately drops the reference, there has to be some other mechanism to ensure the backing memory doesn't get prematurely freed while the PFN is in use.

Ah, right, the memory is pinned or managed by guest_memfd. The reference might be implicitly held by the file mapping itself, or the PFN might just be used to populate the RMP/EPT (or equivalent) tables, and the page's lifetime is bound to the guest_memfd file's. In the case of guest_memfd, those pages are unevictable and not mapped to userspace, meaning they are only freed when the guest_memfd file is truncated or closed. Truncation does trigger MMU notifiers (or the `kvm_gmem_invalidate_begin/end` equivalents in guest_memfd) to zap the SPTEs. So holding a reference *during* the page fault might not be necessary if they're relying on the MMU lock and sequence counter being used correctly.

Let's look at a concrete example to see how this is used. In `arch/x86/kvm/svm/sev.c`, specifically `sev_handle_rmp_fault`, I see they've added `mmu_seq` checking.

```c
@@ -5030,7 +5027,10 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
 		return;
 	}
 
-	ret = kvm_gmem_get_pfn(kvm, slot, gfn, &pfn, &page, &order);
+	mmu_seq = kvm->mmu_invalidate_seq;
+	smp_rmb();
+
+	ret = kvm_gmem_get_pfn(kvm, slot, gfn, &pfn, &order);
```

This confirms that the patch impacts RMP faults within SEV-enabled guests, and there's a strong likelihood it's relying on the MMU's sequence number to handle any race conditions.

Now, I need to check whether `KVM_GUEST_MEMFD` is enabled in any of our syzkaller configurations, or if it's something that can be easily enabled for testing. Since it's typically tied to `KVM_SW_PROTECTED_VM`, `KVM_AMD_SEV`, or `KVM_INTEL_TDX`, it shouldn't be too difficult to get it enabled for testing purposes. I'll need to do a quick search in the Kconfig to confirm how these flags interact. This needs to be fuzzed very thoroughly.

{
  "Expression": "config KVM_GUEST_MEMFD"
}

{
  "Output": "virt/kvm/Kconfig=103=config KVM_GENERIC_MEMORY_ATTRIBUTES\n--\nvirt/kvm/Kconfig-105-\nvirt/kvm/Kconfig:106:config KVM_GUEST_MEMFD\nvirt/kvm/Kconfig-107-       select XARRAY_MULTI\n"
}

gemini-3.1-pro-preview

null

null

							input: 7412
							output: 23
							thoughts: 15
						

Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person:

**Investigating the KVM_GUEST_MEMFD Selection**

Alright, my internal radar is pinging on `KVM_GUEST_MEMFD`. I need to understand the contexts within which this is being selected. I'm going to start by looking for the points of use. What are the relevant source files and code paths that are making this specific selection? Is it a configuration option, a conditional compilation flag based on the architecture or a kernel module loaded state, a feature enabled by some specific setting, or something else entirely? Understanding the selection process itself is key here. I'm after the "why," not just the "what." This is likely the best initial approach to understand the bigger picture. After that I can then understand what this is tied to and where it might be useful, or where an issue might occur. I need to quickly identify the upstream code, and then its direct dependencies and its indirect dependencies so I can determine where I need to focus for maximum value in this deep dive. Let's start digging.

{
  "Expression": "select KVM_GUEST_MEMFD"
}

{
  "Output": "arch/arm64/kvm/Kconfig=20=menuconfig KVM\n--\narch/arm64/kvm/Kconfig-38-\tselect GUEST_PERF_EVENTS if PERF_EVENTS\narch/arm64/kvm/Kconfig:39:\tselect KVM_GUEST_MEMFD\narch/arm64/kvm/Kconfig-40-\thelp\n--\narch/x86/kvm/Kconfig=20=config KVM_X86\n--\narch/x86/kvm/Kconfig-49-\tselect KVM_WERROR if WERROR\narch/x86/kvm/Kconfig:50:\tselect KVM_GUEST_MEMFD if X86_64\narch/x86/kvm/Kconfig-51-\n"
}

gemini-3.1-pro-preview

null

null

							input: 7900
							output: 28
							thoughts: 225
						

**My Assessment of the KVM Patch**

Okay, so this patch is clearly targeting the `guest_memfd` functionality, as it's being selected for both ARM64 with KVM and x86\_64 with KVM\_X86. That tells me that the core concept of using `guest_memfd` is present and accessible within the target systems.

The changes are distributed across several key KVM modules. The fact that it touches `gmem_abort` in `arch/arm64/kvm/mmu.c`, `kvm_translate_vncr` in `arch/arm64/kvm/nested.c`, and `kvm_mmu_faultin_pfn_gmem` in `arch/x86/kvm/mmu/mmu.c` makes sense. These are all intimately involved with memory management and translation, which would be the expected areas for modifications related to `guest_memfd`. The presence of modifications to `__sev_snp_reload_vmsa` and `sev_handle_rmp_fault` in `arch/x86/kvm/svm/sev.c` suggests potential implications for Secure Encrypted Virtualization (SEV) environments, perhaps in how `guest_memfd` interacts with memory protection features.

Now, hold on. `kvm_mmu_faultin_pfn_gmem` is in `arch/x86/kvm/mmu/mmu.c`. I need to understand that function better to determine what those changes entail and to connect the memory fault aspect to the guest memfd. Let's delve into that function and understand its purpose and how the patch alters it.

{
  "Expression": "kvm_mmu_faultin_pfn_gmem"
}

{
  "Output": "arch/x86/kvm/mmu/mmu.c=4589=static void kvm_mmu_finish_page_fault(struct kvm_vcpu *vcpu,\n--\narch/x86/kvm/mmu/mmu.c-4595-\narch/x86/kvm/mmu/mmu.c:4596:static int kvm_mmu_faultin_pfn_gmem(struct kvm_vcpu *vcpu,\narch/x86/kvm/mmu/mmu.c-4597-\t\t\t\t    struct kvm_page_fault *fault)\n--\narch/x86/kvm/mmu/mmu.c=4619=static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu,\n--\narch/x86/kvm/mmu/mmu.c-4624-\tif (fault-\u003eis_private || kvm_memslot_is_gmem_only(fault-\u003eslot))\narch/x86/kvm/mmu/mmu.c:4625:\t\treturn kvm_mmu_faultin_pfn_gmem(vcpu, fault);\narch/x86/kvm/mmu/mmu.c-4626-\n"
}

gemini-3.1-pro-preview

null

null

							input: 8863
							output: 24
							thoughts: 107
						

**My Initial Assessment of the Patch**

Okay, this looks like we've stumbled onto something potentially significant within the core KVM MMU code. My initial impression is that this patch is addressing how references to guest_memfd folios are managed. The key change appears to be the point at which a reference is dropped; instead of returning the reference to the caller in `kvm_gmem_get_pfn`, it's now being dropped internally. This represents a functional alteration in KVM's memory management, which always warrants close scrutiny. Given that we're talking about fundamental memory handling, fuzzing is absolutely the right next step. I need to take a closer look at `kvm_gmem_get_pfn` within `virt/kvm/guest_memfd.c` to understand the full implications.

{
  "Expression": "kvm_gmem_get_pfn"
}

{
  "Output": "arch/arm64/kvm/mmu.c=1608=static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)\n--\narch/arm64/kvm/mmu.c-1642-\narch/arm64/kvm/mmu.c:1643:\tret = kvm_gmem_get_pfn(kvm, s2fd-\u003ememslot, gfn, \u0026pfn, NULL);\narch/arm64/kvm/mmu.c-1644-\tif (ret) {\n--\narch/arm64/kvm/nested.c=1357=static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)\n--\narch/arm64/kvm/nested.c-1413-\t} else {\narch/arm64/kvm/nested.c:1414:\t\tret = kvm_gmem_get_pfn(vcpu-\u003ekvm, memslot, gfn, \u0026pfn, NULL);\narch/arm64/kvm/nested.c-1415-\t\tif (ret) {\n--\narch/x86/kvm/mmu/mmu.c=4596=static int kvm_mmu_faultin_pfn_gmem(struct kvm_vcpu *vcpu,\n--\narch/x86/kvm/mmu/mmu.c-4605-\narch/x86/kvm/mmu/mmu.c:4606:\tr = kvm_gmem_get_pfn(vcpu-\u003ekvm, fault-\u003eslot, fault-\u003egfn, \u0026fault-\u003epfn,\narch/x86/kvm/mmu/mmu.c-4607-\t\t\t     \u0026max_order);\n--\narch/x86/kvm/svm/sev.c=4012=static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)\n--\narch/x86/kvm/svm/sev.c-4061-\t */\narch/x86/kvm/svm/sev.c:4062:\tif (kvm_gmem_get_pfn(vcpu-\u003ekvm, slot, gfn, \u0026pfn, NULL))\narch/x86/kvm/svm/sev.c-4063-\t\treturn;\n--\narch/x86/kvm/svm/sev.c=4998=void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)\n--\narch/x86/kvm/svm/sev.c-5032-\narch/x86/kvm/svm/sev.c:5033:\tret = kvm_gmem_get_pfn(kvm, slot, gfn, \u0026pfn, \u0026order);\narch/x86/kvm/svm/sev.c-5034-\tif (ret) {\n--\ninclude/linux/kvm_host.h=2581=static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)\n--\ninclude/linux/kvm_host.h-2587-#ifdef CONFIG_KVM_GUEST_MEMFD\ninclude/linux/kvm_host.h:2588:int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,\ninclude/linux/kvm_host.h-2589-\t\t     gfn_t gfn, kvm_pfn_t *pfn, int *max_order);\ninclude/linux/kvm_host.h-2590-#else\ninclude/linux/kvm_host.h:2591:static inline int kvm_gmem_get_pfn(struct kvm *kvm,\ninclude/linux/kvm_host.h-2592-\t\t\t\t   struct kvm_memory_slot *slot, gfn_t gfn,\n--\nvirt/kvm/guest_memfd.c=83=static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index)\n--\nvirt/kvm/guest_memfd.c-103-\t/*\nvirt/kvm/guest_memfd.c:104:\t * External interfaces like kvm_gmem_get_pfn() support dealing\nvirt/kvm/guest_memfd.c-105-\t * with hugepages to a degree, but internally, guest_memfd currently\n--\nvirt/kvm/guest_memfd.c=290=static int kvm_gmem_release(struct inode *inode, struct file *file)\n--\nvirt/kvm/guest_memfd.c-305-\t * after which file_ref_get() and get_file_active() fail,\nvirt/kvm/guest_memfd.c:306:\t * kvm_gmem_get_pfn() cannot be using the file concurrently.\nvirt/kvm/guest_memfd.c-307-\t * file_ref_put() provides a full barrier, and get_file_active() the\n--\nvirt/kvm/guest_memfd.c=466=static int kvm_gmem_error_folio(struct address_space *mapping, struct folio *folio)\n--\nvirt/kvm/guest_memfd.c-480-\t * gracefully handling memory errors).  If/when the guest attempts to\nvirt/kvm/guest_memfd.c:481:\t * access a poisoned page, kvm_gmem_get_pfn() will return -EHWPOISON,\nvirt/kvm/guest_memfd.c-482-\t * at which point KVM can either terminate the VM or propagate the\n--\nvirt/kvm/guest_memfd.c=606=int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot,\n--\nvirt/kvm/guest_memfd.c-649-\t * kvm_gmem_bind() must occur on a new memslot.  Because the memslot\nvirt/kvm/guest_memfd.c:650:\t * is not visible yet, kvm_gmem_get_pfn() is guaranteed to see the file.\nvirt/kvm/guest_memfd.c-651-\t */\n--\nvirt/kvm/guest_memfd.c=671=static void __kvm_gmem_unbind(struct kvm_memory_slot *slot, struct gmem_file *f)\n--\nvirt/kvm/guest_memfd.c-678-\t/*\nvirt/kvm/guest_memfd.c:679:\t * synchronize_srcu(\u0026kvm-\u003esrcu) ensured that kvm_gmem_get_pfn()\nvirt/kvm/guest_memfd.c-680-\t * cannot see this memslot.\n--\nvirt/kvm/guest_memfd.c=685=void kvm_gmem_unbind(struct kvm_memory_slot *slot)\n--\nvirt/kvm/guest_memfd.c-716-/* Returns a locked folio on success.  */\nvirt/kvm/guest_memfd.c:717:static struct folio *__kvm_gmem_get_pfn(struct file *file,\nvirt/kvm/guest_memfd.c-718-\t\t\t\t\tstruct kvm_memory_slot *slot,\n--\nvirt/kvm/guest_memfd.c-752-\nvirt/kvm/guest_memfd.c:753:int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,\nvirt/kvm/guest_memfd.c-754-\t\t     gfn_t gfn, kvm_pfn_t *pfn, int *max_order)\n--\nvirt/kvm/guest_memfd.c-765-\nvirt/kvm/guest_memfd.c:766:\tfolio = __kvm_gmem_get_pfn(file, slot, index, pfn, max_order);\nvirt/kvm/guest_memfd.c-767-\tif (IS_ERR(folio))\n--\nvirt/kvm/guest_memfd.c-785-}\nvirt/kvm/guest_memfd.c:786:EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn);\nvirt/kvm/guest_memfd.c-787-\n--\nvirt/kvm/guest_memfd.c=790=static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot,\n--\nvirt/kvm/guest_memfd.c-800-\nvirt/kvm/guest_memfd.c:801:\tfolio = __kvm_gmem_get_pfn(file, slot, index, \u0026pfn, NULL);\nvirt/kvm/guest_memfd.c-802-\tif (IS_ERR(folio)) {\n"
}

gemini-3.1-pro-preview

null

null

							input: 11474
							output: 24
							thoughts: 476
						

**Fuzzing Target Identification**

Okay, so this patch is touching `kvm_gmem_get_pfn` in `virt/kvm/guest_memfd.c`—definitely a good candidate for fuzzing. I can see this is something reachable and potentially interesting, so I should focus my attention on this area.

The functions that seem most relevant and should be the initial targets are: `kvm_gmem_get_pfn`, `sev_handle_rmp_fault`, `__sev_snp_reload_vmsa`, `kvm_mmu_faultin_pfn_gmem`, `gmem_abort`, and `kvm_translate_vncr`. I should make sure I understand the call paths to these to determine where best to apply fuzzing strategies.

Hold on a second, though. I need to note where these functions are defined and if they are static or not, since that will affect my fuzzing approach. Looking closer, I see that `gmem_abort` is static in `arch/arm64/kvm/mmu.c`, `kvm_translate_vncr` is static in `arch/arm64/kvm/nested.c`, `kvm_mmu_faultin_pfn_gmem` is static in `arch/x86/kvm/mmu/mmu.c`, and `__sev_snp_reload_vmsa` is also static, this time in `arch/x86/kvm/svm/sev.c`. `sev_handle_rmp_fault` is non-static in `arch/x86/kvm/svm/sev.c`. `kvm_gmem_get_pfn` is non-static and in `virt/kvm/guest_memfd.c`, as mentioned before.

Okay, let's verify if `sev_handle_rmp_fault` is exported or just non-static, since that dictates how easily I can interact with it. Ah, it's just non-static, which I'll keep in mind for access. Good, and `kvm_gmem_get_pfn` *is* exported: `EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn)`. That's extremely useful; I can leverage that to broaden my coverage.

Regarding configuration, I'll need `KVM` enabled, of course. `KVM_GUEST_MEMFD` is *selected* - ah, that means I don't need to specify that directly. But, just to be thorough and to make sure I am covering all the bases, enabling `KVM_AMD_SEV` or `KVM_SW_PROTECTED_VM` to ensure the memfd code is used might be worthwhile. I should verify what selects `KVM_GUEST_MEMFD`, just to solidify my understanding of the dependencies.

{
  "Expression": "config KVM_SW_PROTECTED_VM"
}

{
  "Output": "arch/x86/kvm/Kconfig=69=config KVM_WERROR\n--\narch/x86/kvm/Kconfig-82-\narch/x86/kvm/Kconfig:83:config KVM_SW_PROTECTED_VM\narch/x86/kvm/Kconfig-84-\tbool \"Enable support for KVM software-protected VMs\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 12722
							output: 22
							thoughts: 13
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Investigating `KVM_AMD_SEV`**

Okay, let's dive into this `KVM_AMD_SEV` thing. My initial thought is to immediately consider the implications for memory encryption and secure virtualization on AMD platforms. We're talking about Secure Encrypted Virtualization (SEV) here, right? So, I'm already mentally running through the architectural aspects – the interplay between the guest OS, the hypervisor, and the AMD Secure Processor. I'm recalling the potential performance overhead associated with the encryption/decryption, and I'm wondering what mitigations are in place to minimize that impact. I want to know about key management and how it's handled, particularly whether it's software-managed, hardware-managed, or a hybrid approach. I'm also considering the security boundaries this establishes – is the hypervisor now untrusted with respect to guest memory, or is there a trust relationship at play? What about DMA attacks; are we using IOMMU to secure those? And of course, I need to check the exact implementation details, so I should see the code.

{
  "Expression": "config KVM_AMD_SEV"
}

{
  "Output": "arch/x86/kvm/Kconfig=146=config KVM_AMD\n--\narch/x86/kvm/Kconfig-155-\narch/x86/kvm/Kconfig:156:config KVM_AMD_SEV\narch/x86/kvm/Kconfig-157-\tbool \"AMD Secure Encrypted Virtualization (SEV) support\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 13118
							output: 23
							thoughts: 14
						

Okay, let's dive into this. Here's my thought process on checking `KVM_INTEL_TDX`:

**Analyzing KVM_INTEL_TDX**

Alright, time to focus. I need to get a clear picture of what's going on with `KVM_INTEL_TDX`. Immediately, the first thing I'm doing is checking its status. Is it enabled? What are the dependencies? I'm already mentally running through the implications of this. Is the hardware present and capable? What's the kernel version looking like? Are the necessary modules loaded? Are there any obvious conflicts? I'm also thinking about potential performance impacts, security considerations, and known issues. I need to quickly establish a baseline understanding, and identify any red flags immediately. Is this feature behaving as I expect it to? Is it providing the anticipated functionality? Are there any obvious issues or unexpected behaviors that need further investigation?

{
  "Expression": "config KVM_INTEL_TDX"
}

{
  "Output": "arch/x86/kvm/Kconfig=122=config X86_SGX_KVM\n--\narch/x86/kvm/Kconfig-133-\narch/x86/kvm/Kconfig:134:config KVM_INTEL_TDX\narch/x86/kvm/Kconfig-135-\tbool \"Intel Trust Domain Extensions (TDX) support\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 13466
							output: 28
							thoughts: 528
						

**My Analysis of KVM and SEV-SNP Guest Memory Management**

Okay, let's break this down. First, I'm checking a hunch. Is `KVM_GUEST_MEMFD` simply selected by `KVM` on arm64 and `KVM_X86` on x86?  The config confirms it:

```
arch/arm64/kvm/Kconfig:39:	select KVM_GUEST_MEMFD
arch/x86/kvm/Kconfig:50:	select KVM_GUEST_MEMFD if X86_64
```

So enabling `KVM` and `KVM_AMD_SEV` is definitely on the right track.

Now, let's dive into the code. Specifically, the patch touches several functions across architectures, so I should be familiar with them all. I see modifications to `sev_handle_rmp_fault` in `arch/x86/kvm/svm/sev.c`. This is where RMP faults for SEV-SNP guests are handled, so that's a key area to understand the changes. The patch is probably modifying how the PFN is retrieved and potentially how the `mmu_seq` is handled. It's also modifying `__sev_snp_reload_vmsa` for context updates.

Additionally, I see changes to `kvm_mmu_faultin_pfn_gmem` in `arch/x86/kvm/mmu/mmu.c`. On ARM64, the changes involve `gmem_abort` in `arch/arm64/kvm/mmu.c` and `kvm_translate_vncr` in `arch/arm64/kvm/nested.c`.

Based on this, the central symbols to focus on are:

-   `kvm_gmem_get_pfn`
-   `sev_handle_rmp_fault`
-   `kvm_mmu_faultin_pfn_gmem`
-   `gmem_abort`
-   `kvm_translate_vncr`

Wait, a small question. It seems that `gmem_abort` and `kvm_translate_vncr` are static, though clearly not trivial, hot-path functions (they're page fault handlers for specific cases). However, the guidelines I usually follow are to favor non-static, non-inlined API entrypoint functions over static helper functions. This is important to note since `kvm_mmu_faultin_pfn_gmem` is a static function. I'll need to double-check if that one is inlined, or if there is a particular reason for its statis declaration. `kvm_gmem_get_pfn` is a non-static API entrypoint, as is `sev_handle_rmp_fault`.

{
  "Expression": "kvm_mmu_faultin_pfn_gmem"
}

{
  "Output": "arch/x86/kvm/mmu/mmu.c=4589=static void kvm_mmu_finish_page_fault(struct kvm_vcpu *vcpu,\n--\narch/x86/kvm/mmu/mmu.c-4595-\narch/x86/kvm/mmu/mmu.c:4596:static int kvm_mmu_faultin_pfn_gmem(struct kvm_vcpu *vcpu,\narch/x86/kvm/mmu/mmu.c-4597-\t\t\t\t    struct kvm_page_fault *fault)\n--\narch/x86/kvm/mmu/mmu.c=4619=static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu,\n--\narch/x86/kvm/mmu/mmu.c-4624-\tif (fault-\u003eis_private || kvm_memslot_is_gmem_only(fault-\u003eslot))\narch/x86/kvm/mmu/mmu.c:4625:\t\treturn kvm_mmu_faultin_pfn_gmem(vcpu, fault);\narch/x86/kvm/mmu/mmu.c-4626-\n"
}

gemini-3.1-pro-preview

null

null

							input: 15000
							output: 24
							thoughts: 327
						

**My Analysis of This KVM Patch**

Okay, so I'm looking at this patch and the first thing I notice is that it deals with memory management, specifically concerning `guest_memfd` within KVM. The code is static, but it's not directly inlined, so I'll go straight to `kvm_gmem_get_pfn` and `sev_handle_rmp_fault`. I need to figure out how these functions are being used and if they're exposed to userspace.

Alright, `kvm_gmem_get_pfn` is definitely reachable from userspace. It's triggered during KVM page faults when the guest attempts to access private memory, and this happens when running a VM using `guest_memfd` and accessing the memory. That makes things a bit more interesting, a userspace dependency, definitely something to consider.

Now, let me put together the reasoning behind the changes. The patch alters how folio references are handled within `kvm_gmem_get_pfn`. Instead of returning the page to the caller to be released, it's dropping the reference directly within that function. This is a significant change, I have to consider the implications on the caller. The patch also updates the callers in both x86 (specifically within the MMU and SEV-SNP code) and ARM64 (MMU and nested virtualization) to accommodate this new signature. Additionally, it introduces MMU sequence counter checks in `sev_handle_rmp_fault` to address potential invalidation races.

Essentially, these are functional changes to core KVM and confidential computing memory management which are directly reachable from userspace because it impacts anyone running a KVM guest that leverages `guest_memfd`.

I need to confirm that these configurations are relevant: `KVM`, `KVM_AMD_SEV`, and `KVM_SW_PROTECTED_VM`.

I'll be paying close attention to these symbols: `kvm_gmem_get_pfn` and `sev_handle_rmp_fault`.
I'm also going to double-check that `KVM_SW_PROTECTED_VM` is the appropriate configuration setting here.

{
  "Expression": "config KVM_SW_PROTECTED_VM"
}

{
  "Output": "arch/x86/kvm/Kconfig=69=config KVM_WERROR\n--\narch/x86/kvm/Kconfig-82-\narch/x86/kvm/Kconfig:83:config KVM_SW_PROTECTED_VM\narch/x86/kvm/Kconfig-84-\tbool \"Enable support for KVM software-protected VMs\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 15928
							output: 22
							thoughts: 45
						

Okay, here's my take on those thoughts, tailored for an expert audience:

**Analyzing the KVM/AMD-SEV Landscape**

Alright, so the core function here is enabling software-protected VMs that leverage `guest_memfd`. I need to ensure the configuration and the supporting kernel features are in place, which means validating my understanding of the system's architecture.

My focus is to ensure `sev_handle_rmp_fault` is correctly configured in this environment. I'm going to determine if `KVM_AMD_SEV` is the correct configuration option to enable these `guest_memfd` secured virtual machines with the appropriate RMP fault handling.

{
  "Expression": "sev_handle_rmp_fault"
}

{
  "Output": "arch/x86/kvm/svm/sev.c=4966=struct page *snp_safe_alloc_page_node(int node, gfp_t gfp)\n--\narch/x86/kvm/svm/sev.c-4997-\narch/x86/kvm/svm/sev.c:4998:void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)\narch/x86/kvm/svm/sev.c-4999-{\n--\narch/x86/kvm/svm/svm.c=1969=static int npf_interception(struct kvm_vcpu *vcpu)\n--\narch/x86/kvm/svm/svm.c-2025-\tif (rc \u003e 0 \u0026\u0026 error_code \u0026 PFERR_GUEST_RMP_MASK)\narch/x86/kvm/svm/svm.c:2026:\t\tsev_handle_rmp_fault(vcpu, gpa, error_code);\narch/x86/kvm/svm/svm.c-2027-\n--\narch/x86/kvm/svm/svm.h=1011=extern unsigned int max_sev_asid;\narch/x86/kvm/svm/svm.h:1012:void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code);\narch/x86/kvm/svm/svm.h-1013-int sev_gmem_make_private(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, kvm_pfn_t nr_pages);\n--\narch/x86/kvm/svm/svm.h=1038=static inline int sev_dev_get_attr(u32 group, u64 attr, u64 *val) { return -ENXIO; }\narch/x86/kvm/svm/svm.h-1039-#define max_sev_asid 0\narch/x86/kvm/svm/svm.h:1040:static inline void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code) {}\narch/x86/kvm/svm/svm.h-1041-static inline struct vmcb_save_area *sev_decrypt_vmsa(struct kvm_vcpu *vcpu)\n"
}

gemini-3.1-pro-preview

null

null

							input: 16793
							output: 212
							thoughts: 57
						

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

**Navigating the SEV Codebase**

Okay, so I'm looking into this `sev_handle_rmp_fault` function. Right, it's pretty clear that this thing is *actually* defined within the `arch/x86/kvm/svm/sev.c` file. Nothing too surprising there. And it only gets compiled when the `KVM_AMD_SEV` option is enabled. That helps narrow down when I'll encounter it. Now, what's next... I think I'll need to call `set-results` to record what I've found so far.

{
  "EnableConfigs": [
    "KVM",
    "KVM_AMD_SEV",
    "KVM_SW_PROTECTED_VM"
  ],
  "FocusSymbols": [
    "kvm_gmem_get_pfn",
    "sev_handle_rmp_fault"
  ],
  "Reasoning": "The patch modifies the memory management of KVM guest_memfd by dropping the folio reference inside `kvm_gmem_get_pfn` instead of returning the page to the caller to be released later. It updates the callers in x86 (MMU and SEV-SNP) and ARM64 (MMU and nested) to accommodate this signature change and adds MMU sequence counter checks in `sev_handle_rmp_fault` to handle invalidation races. These are functional changes to core KVM and confidential computing memory management, which are reachable from userspace by running a KVM guest utilizing guest_memfd.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "KVM",
    "KVM_AMD_SEV",
    "KVM_SW_PROTECTED_VM"
  ],
  "FocusSymbols": [
    "kvm_gmem_get_pfn",
    "sev_handle_rmp_fault"
  ],
  "Reasoning": "The patch modifies the memory management of KVM guest_memfd by dropping the folio reference inside `kvm_gmem_get_pfn` instead of returning the page to the caller to be released later. It updates the callers in x86 (MMU and SEV-SNP) and ARM64 (MMU and nested) to accommodate this signature change and adds MMU sequence counter checks in `sev_handle_rmp_fault` to handle invalidation races. These are functional changes to core KVM and confidential computing memory management, which are reachable from userspace by running a KVM guest utilizing guest_memfd.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

best-expensive

null

{
  "KMSANReasoning": "The patch modifies `kvm_gmem_get_pfn` to no longer return a `struct page` pointer to the caller, instead dropping the folio reference immediately within the function. It updates various callers across arm64 and x86 KVM code to remove the `page` argument and associated cleanup calls (e.g., `kvm_release_faultin_page`, `kvm_release_page_clean`). Additionally, it adds MMU sequence checking (`mmu_invalidate_retry_gfn`) in `sev_handle_rmp_fault` to fix a race condition during RMP faults.\n\nThese changes are purely refactoring of page reference management and concurrency fixes. They do not introduce new data structures sent to user space, do not add conditional logic depending on uninitialized variables, and do not alter bounds checking in a way that exposes uninitialized memory. Any potential bugs introduced by these changes (such as premature page freeing or race conditions) would manifest as use-after-free, NULL pointer dereferences, or memory corruption, which are effectively caught by standard KASAN and LOCKDEP. There is no risk of uninitialized memory usage or info-leaks that would necessitate a dedicated KMSAN fuzzing session.",
  "NeedsKMSAN": false
}

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

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

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

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

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

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

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


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

For your convenience, here is the diff of the changes:
commit 8c7d409071d310bcf22a130824d2685dae024314
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Aug 20 23:49:58 2026 +0000

    syz-cluster: applied patch under review

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 6c941aaa10c63..d5aa197d2cbfd 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1613,7 +1613,6 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)
 	enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
 	struct kvm_pgtable *pgt = s2fd->vcpu->arch.hw_mmu->pgt;
 	unsigned long mmu_seq;
-	struct page *page;
 	struct kvm *kvm = s2fd->vcpu->kvm;
 	void *memcache = NULL;
 	kvm_pfn_t pfn;
@@ -1641,7 +1640,7 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)
 	/* Pairs with the smp_wmb() in kvm_mmu_invalidate_end(). */
 	smp_rmb();
 
-	ret = kvm_gmem_get_pfn(kvm, s2fd->memslot, gfn, &pfn, &page, NULL);
+	ret = kvm_gmem_get_pfn(kvm, s2fd->memslot, gfn, &pfn, NULL);
 	if (ret) {
 		kvm_prepare_memory_fault_exit(s2fd->vcpu, s2fd->fault_ipa, PAGE_SIZE,
 					      write_fault, exec_fault, false);
@@ -1681,7 +1680,6 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)
 	}
 
 out_unlock:
-	kvm_release_faultin_page(kvm, page, !!ret, prot & KVM_PGTABLE_PROT_W);
 	kvm_fault_unlock(kvm);
 
 	if ((prot & KVM_PGTABLE_PROT_W) && !ret)
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index fb54f6dad995c..43523bb17621a 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -1360,7 +1360,7 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)
 	bool write_fault, writable;
 	unsigned long mmu_seq;
 	struct vncr_tlb *vt;
-	struct page *page;
+	struct page *page = NULL;
 	u64 va, pfn, gfn;
 	int ret;
 
@@ -1411,7 +1411,7 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)
 		if (is_error_noslot_pfn(pfn) || (write_fault && !writable))
 			return -EFAULT;
 	} else {
-		ret = kvm_gmem_get_pfn(vcpu->kvm, memslot, gfn, &pfn, &page, NULL);
+		ret = kvm_gmem_get_pfn(vcpu->kvm, memslot, gfn, &pfn, NULL);
 		if (ret) {
 			kvm_prepare_memory_fault_exit(vcpu, vt->wr.pa, PAGE_SIZE,
 					      write_fault, false, false);
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index c519e8e8d646f..129d403308051 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4604,7 +4604,7 @@ static int kvm_mmu_faultin_pfn_gmem(struct kvm_vcpu *vcpu,
 	}
 
 	r = kvm_gmem_get_pfn(vcpu->kvm, fault->slot, fault->gfn, &fault->pfn,
-			     &fault->refcounted_page, &max_order);
+			     &max_order);
 	if (r) {
 		kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
 		return r;
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index fcb41dfde4c02..0c91c904573cc 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4016,7 +4016,6 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)
 	struct kvm *kvm = vcpu->kvm;
 	gfn_t gfn = gpa_to_gfn(gpa);
 	unsigned long mmu_seq;
-	struct page *page;
 	kvm_pfn_t pfn;
 
 	lockdep_assert_held(&svm->sev_es.snp_vmsa_mutex);
@@ -4060,7 +4059,7 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)
 	 * The new VMSA will be private memory guest memory, so retrieve the
 	 * PFN from the gmem backend.
 	 */
-	if (kvm_gmem_get_pfn(vcpu->kvm, slot, gfn, &pfn, &page, NULL))
+	if (kvm_gmem_get_pfn(vcpu->kvm, slot, gfn, &pfn, NULL))
 		return;
 
 	read_lock(&kvm->mmu_lock);
@@ -4076,8 +4075,6 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)
 	else
 		svm->vmcb->control.vmsa_pa = pfn_to_hpa(pfn);
 	read_unlock(&kvm->mmu_lock);
-
-	kvm_release_page_clean(page);
 }
 
 /*
@@ -5003,7 +5000,7 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
 	struct kvm_memory_slot *slot;
 	struct kvm *kvm = vcpu->kvm;
 	int order, rmp_level, ret;
-	struct page *page;
+	unsigned long mmu_seq;
 	bool assigned;
 	kvm_pfn_t pfn;
 	gfn_t gfn;
@@ -5030,7 +5027,10 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
 		return;
 	}
 
-	ret = kvm_gmem_get_pfn(kvm, slot, gfn, &pfn, &page, &order);
+	mmu_seq = kvm->mmu_invalidate_seq;
+	smp_rmb();
+
+	ret = kvm_gmem_get_pfn(kvm, slot, gfn, &pfn, &order);
 	if (ret) {
 		pr_warn_ratelimited("SEV: Unexpected RMP fault, no backing page for private GPA 0x%llx\n",
 				    gpa);
@@ -5039,9 +5039,13 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
 
 	ret = snp_lookup_rmpentry(pfn, &assigned, &rmp_level);
 	if (ret || !assigned) {
-		pr_warn_ratelimited("SEV: Unexpected RMP fault, no assigned RMP entry found for GPA 0x%llx PFN 0x%llx error %d\n",
-				    gpa, pfn, ret);
-		goto out_no_trace;
+		guard(read_lock)(&kvm->mmu_lock);
+
+		if (!mmu_invalidate_retry_gfn(kvm, mmu_seq, gfn))
+			pr_warn_ratelimited("SEV: Unexpected RMP fault, no assigned RMP entry found for GPA 0x%llx PFN 0x%llx error %d\n",
+					    gpa, pfn, ret);
+
+		return;
 	}
 
 	/*
@@ -5069,26 +5073,31 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
 	if (rmp_level == PG_LEVEL_4K)
 		goto out;
 
-	ret = snp_rmptable_psmash(pfn);
-	if (ret) {
-		/*
-		 * Look it up again. If it's 4K now then the PSMASH may have
-		 * raced with another process and the issue has already resolved
-		 * itself.
-		 */
-		if (!snp_lookup_rmpentry(pfn, &assigned, &rmp_level) &&
-		    assigned && rmp_level == PG_LEVEL_4K)
+	scoped_guard(read_lock, &kvm->mmu_lock) {
+		if (mmu_invalidate_retry_gfn(kvm, mmu_seq, gfn))
 			goto out;
 
-		pr_warn_ratelimited("SEV: Unable to split RMP entry for GPA 0x%llx PFN 0x%llx ret %d\n",
-				    gpa, pfn, ret);
+		ret = snp_rmptable_psmash(pfn);
+		if (ret) {
+			/*
+			 * Look it up again. If it's 4K now then the PSMASH may
+			 * have raced with another process and the issue has
+			 * already resolved itself. If it's not assigned, then
+			 * this must have raced with another process that made
+			 * this page shared.
+			 */
+			if (!snp_lookup_rmpentry(pfn, &assigned, &rmp_level) &&
+			    ((assigned && rmp_level == PG_LEVEL_4K) || !assigned))
+				goto out;
+
+			pr_warn_ratelimited("SEV: Unable to split RMP entry for GPA 0x%llx PFN 0x%llx ret %d\n",
+					    gpa, pfn, ret);
+		}
 	}
 
 	kvm_zap_gfn_range(kvm, gfn, gfn + PTRS_PER_PMD);
 out:
 	trace_kvm_rmp_fault(vcpu, gpa, pfn, error_code, rmp_level, ret);
-out_no_trace:
-	kvm_release_page_unused(page);
 }
 
 static bool is_pfn_range_shared(kvm_pfn_t start, kvm_pfn_t end)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 03bfc92864b6e..502465119ca0c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2586,13 +2586,11 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
 
 #ifdef CONFIG_KVM_GUEST_MEMFD
 int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
-		     gfn_t gfn, kvm_pfn_t *pfn, struct page **page,
-		     int *max_order);
+		     gfn_t gfn, kvm_pfn_t *pfn, int *max_order);
 #else
 static inline int kvm_gmem_get_pfn(struct kvm *kvm,
 				   struct kvm_memory_slot *slot, gfn_t gfn,
-				   kvm_pfn_t *pfn, struct page **page,
-				   int *max_order)
+				   kvm_pfn_t *pfn, int *max_order)
 {
 	KVM_BUG_ON(1, kvm);
 	return -EIO;
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index b596486d184ca..589762140c3ef 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -751,8 +751,7 @@ static struct folio *__kvm_gmem_get_pfn(struct file *file,
 }
 
 int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
-		     gfn_t gfn, kvm_pfn_t *pfn, struct page **page,
-		     int *max_order)
+		     gfn_t gfn, kvm_pfn_t *pfn, int *max_order)
 {
 	pgoff_t index = kvm_gmem_get_index(slot, gfn);
 	struct folio *folio;
@@ -780,11 +779,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
 #endif
 
 	folio_unlock(folio);
-
-	if (!r)
-		*page = folio_file_page(folio, index);
-	else
-		folio_put(folio);
+	folio_put(folio);
 
 	return r;
 }

gemini-3.1-pro-preview

null

null

							input: 5608
							output: 36
							thoughts: 721
						

**KVM Guest Memory Refactoring Analysis**

Okay, so this patch is cleaning up the `kvm_gmem_get_pfn` function. The core change is the removal of the `struct page **page` argument, which is a significant shift in how page references are handled. It's affecting several files: `arch/arm64/kvm/mmu.c`, `arch/arm64/kvm/nested.c`, `arch/x86/kvm/mmu/mmu.c`, `arch/x86/kvm/svm/sev.c`, and `virt/kvm/guest_memfd.c`. The main implication is that the caller no longer receives a pointer to the page; the reference is effectively dropped immediately within `kvm_gmem_get_pfn` using `folio_put(folio)`.

My initial thought is that this is likely a refactoring effort to either prevent potential page reference leaks or simplify the API by changing how gmem pages are managed. Either these pages don't need to be pinned by the caller in the same way, or maybe the file itself takes responsibility for pinning.

My immediate concern is always with memory safety. I need to make sure this doesn't introduce any uninitialized memory risks. Looking at the changes, it's removing a pointer and associated cleanup, not introducing anything new to userspace. No new data structures, no new conditional logic based on potentially uninitialized variables, and no modifications to bounds checks. It looks like a pure refactoring and cleanup of the KVM guest_memfd API and I don't see any obvious risk of uninitialized memory. Moreover, any potential use-after-free scenarios due to premature page release will be caught by KASAN/LOCKDEP/etc. I don't think I need to bring KMSAN into the analysis.

Now, I need to double-check a specific point. In `arch/x86/kvm/mmu/mmu.c`, `kvm_mmu_faultin_pfn_gmem` is being updated. The critical part is that `fault->refcounted_page` is no longer set. This *is* a point of concern. The original implementation called:

```c
 	r = kvm_gmem_get_pfn(vcpu->kvm, fault->slot, fault->gfn, &fault->pfn,
-			     &fault->refcounted_page, &max_order);
+			     &max_order);
```

Since `fault->refcounted_page` is no longer populated by `kvm_gmem_get_pfn`, what's going to happen with it? Does it remain uninitialized, and is it used later? I'll need to check the initialization of `struct kvm_page_fault` and where `refcounted_page` is used to understand the complete impact of this change. I'll need to use my grepper to analyze this.

{
  "Expression": "refcounted_page",
  "PathPrefix": "arch/x86/kvm/mmu/"
}

{
  "Output": "arch/x86/kvm/mmu/mmu.c=4589=static void kvm_mmu_finish_page_fault(struct kvm_vcpu *vcpu,\n--\narch/x86/kvm/mmu/mmu.c-4591-{\narch/x86/kvm/mmu/mmu.c:4592:\tkvm_release_faultin_page(vcpu-\u003ekvm, fault-\u003erefcounted_page,\narch/x86/kvm/mmu/mmu.c-4593-\t\t\t\t r == RET_PF_RETRY, fault-\u003emap_writable);\n--\narch/x86/kvm/mmu/mmu.c=4619=static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu,\n--\narch/x86/kvm/mmu/mmu.c-4628-\tfault-\u003epfn = __kvm_faultin_pfn(fault-\u003eslot, fault-\u003egfn, foll,\narch/x86/kvm/mmu/mmu.c:4629:\t\t\t\t       \u0026fault-\u003emap_writable, \u0026fault-\u003erefcounted_page);\narch/x86/kvm/mmu/mmu.c-4630-\n--\narch/x86/kvm/mmu/mmu.c-4658-\tfault-\u003epfn = __kvm_faultin_pfn(fault-\u003eslot, fault-\u003egfn, foll,\narch/x86/kvm/mmu/mmu.c:4659:\t\t\t\t       \u0026fault-\u003emap_writable, \u0026fault-\u003erefcounted_page);\narch/x86/kvm/mmu/mmu.c-4660-\n--\narch/x86/kvm/mmu/mmu_internal.h=226=struct kvm_page_fault {\n--\narch/x86/kvm/mmu/mmu_internal.h-281-\tkvm_pfn_t pfn;\narch/x86/kvm/mmu/mmu_internal.h:282:\tstruct page *refcounted_page;\narch/x86/kvm/mmu/mmu_internal.h-283-\tbool map_writable;\n"
}

gemini-3.1-pro-preview

null

null

							input: 7597
							output: 41
							thoughts: 11
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Tracing the Genesis of "fault"**

Alright, let's dive in. The first logical step is to pinpoint the origin of the variable, `fault`. Where does this guy pop into existence? I need to understand its initialization, its initial value (or lack thereof), and how that initial state shapes the subsequent flow of the code. Is it assigned directly? Is it a member of a structure or class? Is it dynamically allocated? Understanding the "why" behind the initialization is key; it'll influence everything down the line. Is there some default state assumed? Are there preconditions that must be met before this thing is even considered valid? Gotta know this stuff. Digging into this initialization should give me a solid foundation for understanding the context within which `fault` operates.

{
  "Expression": "struct kvm_page_fault .*=",
  "PathPrefix": "arch/x86/kvm/mmu/"
}

{
  "Output": "arch/x86/kvm/mmu/mmu.c=4955=static int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,\n--\narch/x86/kvm/mmu/mmu.c-4958-{\narch/x86/kvm/mmu/mmu.c:4959:\tstruct kvm_page_fault fault = {\narch/x86/kvm/mmu/mmu.c-4960-\t\t.addr = cr2_or_gpa,\n--\narch/x86/kvm/mmu/mmu.c=5154=int kvm_tdp_mmu_map_private_pfn(struct kvm_vcpu *vcpu, gfn_t gfn, kvm_pfn_t pfn)\narch/x86/kvm/mmu/mmu.c-5155-{\narch/x86/kvm/mmu/mmu.c:5156:\tstruct kvm_page_fault fault = {\narch/x86/kvm/mmu/mmu.c-5157-\t\t.addr = gfn_to_gpa(gfn),\n"
}

gemini-3.1-pro-preview

null

null

							input: 8155
							output: 39
							thoughts: 124
						

**Analyzing the Potential Null Pointer in Fault Handling**

Okay, so I'm looking at this `fault` struct, and the initialization `fault = { ... }` is key here. That means anything *not* explicitly listed within that curly brace list will be zero-initialized. I need to be sure about this assumption. I believe, implicitly, this means `refcounted_page` will be NULL if not assigned a specific value during the process.

Now, if `kvm_gmem_get_pfn` *doesn't* set `fault->refcounted_page` – and this is the crux of the problem – then it'll remain that zero-initialized NULL value. That’s potentially problematic, as this field could be read later.

The following call is: `kvm_release_faultin_page(vcpu->kvm, fault->refcounted_page, ...)`. If `fault->refcounted_page` is indeed NULL, calling this will be fine and a no-op. It should be handled correctly by that function. However, I want to be 100% certain of that and not just assume that is the case. So the next step is to examine `kvm_release_faultin_page` and determine the actions it will take on a NULL pointer.

{
  "Expression": "kvm_release_faultin_page",
  "PathPrefix": "include/linux/kvm_host.h"
}

{
  "Output": "include/linux/kvm_host.h=1291=void kvm_release_page_dirty(struct page *page);\ninclude/linux/kvm_host.h-1292-\ninclude/linux/kvm_host.h:1293:static inline void kvm_release_faultin_page(struct kvm *kvm, struct page *page,\ninclude/linux/kvm_host.h-1294-\t\t\t\t\t    bool unused, bool dirty)\n"
}

gemini-3.1-pro-preview

null

null

							input: 8724
							output: 42
							thoughts: 17
						

Okay, let's dive into this `kvm_release_faultin_page` implementation. I'm going to walk through this function, thinking like I'm debugging a tricky memory issue. I need to understand exactly what happens here, especially when it comes to releasing the fault-in page. Let's start with the basics, what are the key data structures and how does it relate to the memory management of a KVM guest? It seems like this function has significant implications for overall performance and stability of the system. I also need to understand how this interacts with any other memory management functions that could be called concurrently. Let's see how the release process works at a low level.

{
  "Expression": "static inline void kvm_release_faultin_page",
  "PathPrefix": "include/linux/kvm_host.h"
}

{
  "Output": "include/linux/kvm_host.h=1291=void kvm_release_page_dirty(struct page *page);\ninclude/linux/kvm_host.h-1292-\ninclude/linux/kvm_host.h:1293:static inline void kvm_release_faultin_page(struct kvm *kvm, struct page *page,\ninclude/linux/kvm_host.h-1294-\t\t\t\t\t    bool unused, bool dirty)\n"
}

gemini-3.1-pro-preview

null

null

							input: 9055
							output: 39
							thoughts: 15
						

Okay, let's dive into this `kvm_release_faultin_page` function. I've seen this one before, of course, but it's always good to refresh my memory on the intricacies, especially in the context of KVM's memory management. This is critical for understanding performance bottlenecks and potential vulnerabilities.

**My Perspective on `kvm_release_faultin_page`**

Right, so this function is, essentially, a cleanup routine. It's the mechanism by which KVM gracefully relinquishes a page that was brought in for a fault. That "fault" could be due to a variety of reasons – a guest wanting to access a page that wasn't resident, a copy-on-write event, or perhaps even a page being reclaimed from a swap device. My immediate questions are always: what are the conditions that trigger the call to this function? Is it a heavily trafficked part of the code, or more of an edge case?

I need to understand the implications of this release. Is the page simply being freed back to the host's page allocator? Or are there more subtle considerations, like invalidating TLB entries, updating page tables, or ensuring coherency across different CPU cores? It's essential to trace the dependencies. Are there any other data structures that refer to this page that *must* be updated or invalidated as part of this process? This is where potential race conditions can become a nightmare. I want to look closely at synchronization primitives used here: locks, atomic operations, and how they relate to other functions accessing the same data.

From an optimization standpoint, I'll be looking at the efficiency of this release process. Is it optimized for common scenarios? Are there any opportunities for batching operations or employing more efficient data structures to improve throughput? Given KVM's critical role in virtualization, any performance improvement in this function can have a significant cascading effect on overall system performance. I need to be aware of the interplay between this function and the hardware architecture, particularly any cache-related effects.

Finally, I'll pay close attention to the error handling. What happens if the release fails? Does the system gracefully recover, or could this lead to crashes or memory leaks? I need to understand the failure modes and the implications for both the guest and the host. Security is paramount so any potential for a double-free or memory corruption is a red flag. Let's see how they handled any such scenarios. Okay, let's start digging into the code.

{
  "File": "include/linux/kvm_host.h",
  "FirstLine": 1290,
  "LineCount": 20
}

{
  "Contents": "1290:\tvoid kvm_release_page_clean(struct page *page);\n1291:\tvoid kvm_release_page_dirty(struct page *page);\n1292:\t\n1293:\tstatic inline void kvm_release_faultin_page(struct kvm *kvm, struct page *page,\n1294:\t\t\t\t\t\t    bool unused, bool dirty)\n1295:\t{\n1296:\t\tlockdep_assert_once(lockdep_is_held(\u0026kvm-\u003emmu_lock) || unused);\n1297:\t\n1298:\t\tif (!page)\n1299:\t\t\treturn;\n1300:\t\n1301:\t\t/*\n1302:\t\t * If the page that KVM got from the *primary MMU* is writable, and KVM\n1303:\t\t * installed or reused a SPTE, mark the page/folio dirty.  Note, this\n1304:\t\t * may mark a folio dirty even if KVM created a read-only SPTE, e.g. if\n1305:\t\t * the GFN is write-protected.  Folios can't be safely marked dirty\n1306:\t\t * outside of mmu_lock as doing so could race with writeback on the\n1307:\t\t * folio.  As a result, KVM can't mark folios dirty in the fast page\n1308:\t\t * fault handler, and so KVM must (somewhat) speculatively mark the\n1309:\t\t * folio dirty if KVM could locklessly make the SPTE writable.\n"
}

gemini-3.1-pro-preview

null

null

							input: 10031
							output: 33
							thoughts: 114
						

**Analyzing Potential Null Pointer Issues**

Okay, so I see `if (!page) return;` at the beginning, which seems to handle the case where `page` might be NULL. Good, that's a basic check. Now, let's dive into `kvm_translate_vncr` in `arch/arm64/kvm/nested.c` and take a closer look at that function.

Aha, `struct vncr_tlb *vt;` and the crucial line: `struct page *page = NULL;`. Wait, `page` *is* initialized to NULL. That's a good practice, preventing potential uninitialized memory issues. But, I'm noticing it's not actually passed to `kvm_gmem_get_pfn` anymore. I need to be sure the removal of the call is not a problem.

The question then becomes: is `page` used *anywhere* else down the line? If it isn't, and it's not being dereferenced, that null initialization is somewhat redundant, but harmless. But, if it *is* used further down the code path without being assigned a valid pointer, that's where we've got a potential NULL pointer dereference, and we'll need to dig deeper.

{
  "Expression": "page",
  "PathPrefix": "arch/arm64/kvm/nested.c"
}

{
  "Output": "arch/arm64/kvm/nested.c=68=int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu)\n--\narch/arm64/kvm/nested.c-78-\tif (!vcpu-\u003earch.ctxt.vncr_array)\narch/arm64/kvm/nested.c:79:\t\tvcpu-\u003earch.ctxt.vncr_array = (u64 *)__get_free_page(GFP_KERNEL_ACCOUNT |\narch/arm64/kvm/nested.c-80-\t\t\t\t\t\t\t\t    __GFP_ZERO);\n--\narch/arm64/kvm/nested.c-121-\narch/arm64/kvm/nested.c:122:\t\tfree_page((unsigned long)vcpu-\u003earch.ctxt.vncr_array);\narch/arm64/kvm/nested.c-123-\t\tvcpu-\u003earch.ctxt.vncr_array = NULL;\n--\narch/arm64/kvm/nested.c=251=static int walk_nested_s2_pgd(struct kvm_vcpu *vcpu, phys_addr_t ipa,\n--\narch/arm64/kvm/nested.c-256-\tunsigned int addr_top, addr_bottom;\narch/arm64/kvm/nested.c:257:\tu64 desc, new_desc;  /* page table entry */\narch/arm64/kvm/nested.c-258-\tint ret;\n--\narch/arm64/kvm/nested.c=1270=void kvm_arch_flush_shadow_all(struct kvm *kvm)\n--\narch/arm64/kvm/nested.c-1303- *   (unless we are preempted), so the resolution of a translation fault\narch/arm64/kvm/nested.c:1304: *   must go via a request that will map the VNCR page in the fixmap.\narch/arm64/kvm/nested.c-1305- *   vcpu_load() might as well use the same mechanism.\n--\narch/arm64/kvm/nested.c-1314- * - On any TLBI for the EL2\u00260 translation regime, we must find any TLB that\narch/arm64/kvm/nested.c:1315: *   intersects with the TLBI request, invalidate it, and unmap the page\narch/arm64/kvm/nested.c-1316- *   from the fixmap. Because we need to look at all the vcpu-private TLBs,\n--\narch/arm64/kvm/nested.c-1322- *   looking at the IPA instead. The funny part is that there may not be a\narch/arm64/kvm/nested.c:1323: *   stage-2 mapping for this page if L1 hasn't accessed it using LD/ST\narch/arm64/kvm/nested.c-1324- *   instructions.\n--\narch/arm64/kvm/nested.c=1357=static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)\n--\narch/arm64/kvm/nested.c-1362-\tstruct vncr_tlb *vt;\narch/arm64/kvm/nested.c:1363:\tstruct page *page = NULL;\narch/arm64/kvm/nested.c-1364-\tu64 va, pfn, gfn;\n--\narch/arm64/kvm/nested.c-1409-\t\tpfn = __kvm_faultin_pfn(memslot, gfn, write_fault ? FOLL_WRITE : 0,\narch/arm64/kvm/nested.c:1410:\t\t\t\t\t\u0026writable, \u0026page);\narch/arm64/kvm/nested.c-1411-\t\tif (is_error_noslot_pfn(pfn) || (write_fault \u0026\u0026 !writable))\n--\narch/arm64/kvm/nested.c-1423-\t\tif (mmu_invalidate_retry(vcpu-\u003ekvm, mmu_seq)) {\narch/arm64/kvm/nested.c:1424:\t\t\tkvm_release_faultin_page(vcpu-\u003ekvm, page, true, false);\narch/arm64/kvm/nested.c-1425-\t\t\treturn -EAGAIN;\n--\narch/arm64/kvm/nested.c-1433-\t\tkvm_make_request(KVM_REQ_MAP_L1_VNCR_EL2, vcpu);\narch/arm64/kvm/nested.c:1434:\t\tkvm_release_faultin_page(vcpu-\u003ekvm, page, false, vt-\u003ewr.pw);\narch/arm64/kvm/nested.c-1435-\t}\n--\narch/arm64/kvm/nested.c-1437-\tif (vt-\u003ewr.pw)\narch/arm64/kvm/nested.c:1438:\t\tmark_page_dirty(vcpu-\u003ekvm, gfn);\narch/arm64/kvm/nested.c-1439-\n--\narch/arm64/kvm/nested.c=1604=u64 limit_nv_id_reg(struct kvm *kvm, u32 reg, u64 val)\n--\narch/arm64/kvm/nested.c-1661-\narch/arm64/kvm/nested.c:1662:\t\t/* Disallow unsupported S2 page sizes */\narch/arm64/kvm/nested.c-1663-\t\tswitch (PAGE_SIZE) {\n--\narch/arm64/kvm/nested.c-1675-\t\t/*\narch/arm64/kvm/nested.c:1676:\t\t * Since we can't support a guest S2 page size smaller\narch/arm64/kvm/nested.c:1677:\t\t * than the host's own page size (due to KVM only\narch/arm64/kvm/nested.c:1678:\t\t * populating its own S2 using the kernel's page\narch/arm64/kvm/nested.c-1679-\t\t * size), advertise the limitation using FEAT_GTG.\n"
}

gemini-3.1-pro-preview

null

null

							input: 12063
							output: 283
							thoughts: 949
						

**KMSAN Assessment: No Risk of Uninitialized Memory**

Okay, let's break this down. First, I noticed that `page` is still in use within `kvm_translate_vncr` when it's *not* a gmem case. It's properly handled, though, with `kvm_release_faultin_page` handling the release when `page` is valid. If it *is* gmem, `page` is NULL, and `kvm_release_faultin_page` correctly handles the NULL case. That's fine.

Then I checked `sev_handle_rmp_fault` and saw the addition of `mmu_seq` and `mmu_invalidate_retry_gfn`. This is classic KVM concurrency handling for RMP faults – it's all about checking if the MMU sequence has changed to avoid race conditions. No concerns there; it's robust and standard practice. No uninitialized memory issues.

Next, I drilled into `virt/kvm/guest_memfd.c` and `kvm_gmem_get_pfn`. Here's the core change. The function *used* to return a `struct page` pointer to the caller, but now it drops the folio reference immediately within the function. This means the caller *doesn't* hold a reference to the page anymore. Is this safe? I thought through it, and I believe it is. The page is pinned because of the `guest_memfd` file, and KVM holds a reference to that file. Even if there's a bug here (like a use-after-free), it's a UAF, and KASAN should easily detect that. Crucially, it's *not* an uninitialized memory issue.

So, the patch is really just refactoring and concurrency fixes. The updates across the code that removed `page` and associated cleanup calls simply reflect the change in `kvm_gmem_get_pfn`. The addition of the MMU sequence checks in the RMP fault handler addresses a known race condition. These changes don't introduce any new data sent to user space, don't depend on uninitialized variables in any conditional logic, and don't change how bounds checking works in a way that would expose uninitialized memory. Any bugs introduced would present as UAFs, null pointer dereferences, or memory corruption. These issues are very likely to be detected by KASAN and/or LOCKDEP. No uninitialized memory is at risk, so a dedicated KMSAN session isn't needed here. I'm going to write that down.

{
  "KMSANReasoning": "The patch modifies `kvm_gmem_get_pfn` to no longer return a `struct page` pointer to the caller, instead dropping the folio reference immediately within the function. It updates various callers across arm64 and x86 KVM code to remove the `page` argument and associated cleanup calls (e.g., `kvm_release_faultin_page`, `kvm_release_page_clean`). Additionally, it adds MMU sequence checking (`mmu_invalidate_retry_gfn`) in `sev_handle_rmp_fault` to fix a race condition during RMP faults.\n\nThese changes are purely refactoring of page reference management and concurrency fixes. They do not introduce new data structures sent to user space, do not add conditional logic depending on uninitialized variables, and do not alter bounds checking in a way that exposes uninitialized memory. Any potential bugs introduced by these changes (such as premature page freeing or race conditions) would manifest as use-after-free, NULL pointer dereferences, or memory corruption, which are effectively caught by standard KASAN and LOCKDEP. There is no risk of uninitialized memory usage or info-leaks that would necessitate a dedicated KMSAN fuzzing session.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch modifies `kvm_gmem_get_pfn` to no longer return a `struct page` pointer to the caller, instead dropping the folio reference immediately within the function. It updates various callers across arm64 and x86 KVM code to remove the `page` argument and associated cleanup calls (e.g., `kvm_release_faultin_page`, `kvm_release_page_clean`). Additionally, it adds MMU sequence checking (`mmu_invalidate_retry_gfn`) in `sev_handle_rmp_fault` to fix a race condition during RMP faults.\n\nThese changes are purely refactoring of page reference management and concurrency fixes. They do not introduce new data structures sent to user space, do not add conditional logic depending on uninitialized variables, and do not alter bounds checking in a way that exposes uninitialized memory. Any potential bugs introduced by these changes (such as premature page freeing or race conditions) would manifest as use-after-free, NULL pointer dereferences, or memory corruption, which are effectively caught by standard KASAN and LOCKDEP. There is no risk of uninitialized memory usage or info-leaks that would necessitate a dedicated KMSAN fuzzing session.",
  "NeedsKMSAN": false
}