AI Trajectory

null

{
  "EnableConfigs": [
    "KVM",
    "KVM_AMD_SEV",
    "KVM_SW_PROTECTED_VM"
  ],
  "FocusSymbols": [
    "kvm_gmem_get_pfn",
    "sev_handle_rmp_fault",
    "sev_snp_reload_vmsa",
    "kvm_handle_vncr_abort"
  ],
  "KMSANReasoning": "The patch refactors `kvm_gmem_get_pfn()` to remove the `struct page **page` argument and drops the associated page reference counting (`kvm_release_faultin_page`, `kvm_release_page_clean`, etc.) across multiple architectures (arm64, x86). This is a memory management and refcounting change. There are no new structures sent to user space, no new uninitialized memory allocations, and no info-leaks. Any bugs introduced by this change would likely be use-after-free, memory leaks, or NULL pointer dereferences, which are effectively caught by KASAN and other standard debugging tools. Therefore, a dedicated KMSAN fuzzing session is not required.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch changes the signature and behavior of `kvm_gmem_get_pfn` by removing the `struct page **page` argument and dropping the folio reference before returning. This affects how KVM handles memory backing for guest_memfd, which is a core feature for confidential computing (SEV-SNP, TDX, ARM CCA). The changes are reachable via KVM ioctls and page faults when using guest_memfd.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 00fceae410c054105ee6e96a37b41661e3e2a1bf\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Aug 26 09:19:42 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 9ba86450fe4af..d57f8181f1b7d 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 17123f0b6daba..dd62840d36741 100644\n--- a/arch/arm64/kvm/nested.c\n+++ b/arch/arm64/kvm/nested.c\n@@ -1415,7 +1415,7 @@ 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@@ -1471,7 +1471,7 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)\n \t\t\treturn -EFAULT;\n \t\t}\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 064ecc33b9267..947c9cd843450 100644\n--- a/arch/x86/kvm/mmu/mmu.c\n+++ b/arch/x86/kvm/mmu/mmu.c\n@@ -4628,7 +4628,7 @@ 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 5705723f1f412..0a887f8e05d3a 100644\n--- a/arch/x86/kvm/svm/sev.c\n+++ b/arch/x86/kvm/svm/sev.c\n@@ -4032,7 +4032,6 @@ 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@@ -4076,7 +4075,7 @@ 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@@ -4092,8 +4091,6 @@ 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@@ -5019,7 +5016,7 @@ 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@@ -5046,7 +5043,10 @@ 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@@ -5055,9 +5055,13 @@ 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@@ -5085,26 +5089,31 @@ 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",
    "sev_snp_reload_vmsa",
    "kvm_handle_vncr_abort"
  ],
  "Reasoning": "The patch changes the signature and behavior of `kvm_gmem_get_pfn` by removing the `struct page **page` argument and dropping the folio reference before returning. This affects how KVM handles memory backing for guest_memfd, which is a core feature for confidential computing (SEV-SNP, TDX, ARM CCA). The changes are reachable via KVM ioctls and page faults when using 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 00fceae410c054105ee6e96a37b41661e3e2a1bf
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Aug 26 09:19:42 2026 +0000

    syz-cluster: applied patch under review

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 9ba86450fe4af..d57f8181f1b7d 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 17123f0b6daba..dd62840d36741 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -1415,7 +1415,7 @@ 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;
 
@@ -1471,7 +1471,7 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)
 			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 064ecc33b9267..947c9cd843450 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4628,7 +4628,7 @@ 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 5705723f1f412..0a887f8e05d3a 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4032,7 +4032,6 @@ 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);
@@ -4076,7 +4075,7 @@ 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);
@@ -4092,8 +4091,6 @@ 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);
 }
 
 /*
@@ -5019,7 +5016,7 @@ 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;
@@ -5046,7 +5043,10 @@ 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);
@@ -5055,9 +5055,13 @@ 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;
 	}
 
 	/*
@@ -5085,26 +5089,31 @@ 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: 5592
							output: 23
							thoughts: 428
						

**Analyzing the KVM Patch for Guest Memfd and Confidential Computing**

Okay, so I'm looking at this patch for KVM, and it's modifying `kvm_gmem_get_pfn`. It looks like they're dropping the `struct page **page` argument and, more significantly, no longer returning a referenced page. Instead, it's just the pfn, with the folio reference dropped before returning. Alright, that's a pretty significant change. The code affected includes some critical areas: `arch/arm64/kvm/mmu.c`, `arch/arm64/kvm/nested.c`, and the x86 equivalent, plus some other key files like the header and `virt/kvm/guest_memfd.c`.

My first thought is, how is the memory kept alive if they are dropping the reference? Ah, it looks like `guest_memfd` memory is managed through the file descriptor itself, and KVM's mmu_notifier-like mechanism, or rather the guest_memfd invalidation callbacks, handles the unmapping if the memory is freed. So, it appears this is a functional change for how KVM handles `guest_memfd` pages. They are no longer taking a page reference.

Given this is a core component, I should probably check if this is reachable and worth fuzzing. Okay, `KVM guest_memfd` is a key piece for confidential computing, right? SEV-SNP, TDX, and ARM CCA all use it. And, yes, it's reachable via KVM ioctls. I need to make sure this is reachable within a standard QEMU or GCE setup. I should check how these guest memfds are created. Ah, they're created with `KVM_CREATE_GUEST_MEMFD`. And yes, this is available if `CONFIG_KVM_GUEST_MEMFD` is enabled. Wait, and it looks like `CONFIG_KVM_GUEST_MEMFD` is selected by KVM_SW_PROTECTED_VM or other confidential computing configs. Perfect, let me just double-check that `CONFIG_KVM_GUEST_MEMFD` config.

{
  "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: 6608
							output: 23
							thoughts: 15
						

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

**Investigating KVM_GUEST_MEMFD**

Alright, let's dive into this `KVM_GUEST_MEMFD` selection. My initial thought process is to understand *why* it's being chosen or being considered. What's the context here? Is it related to a specific vulnerability, performance optimization, or new feature introduction within the KVM ecosystem? My expert intuition kicks in; I'm immediately running through possible use cases in my head: memory ballooning, secure guest memory management, potentially even shared memory implementations. I need to figure out the triggering event or condition that leads to the selection of this particular configuration. What other related options are potentially being considered? I will delve deeper into documentation, code, and related mailing list discussions. It's likely that it's being chosen for a reason, and there is certainly much for me to discover here.

{
  "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: 7064
							output: 18
							thoughts: 331
						

**My Fuzzing Target Identification**

Okay, so this is automatically enabled on both ARM64 and X86_64 KVM, which is good – definitely reachable. My first step is to identify the most promising functions for fuzzing.

Looking at the patch, I see modifications in a few key areas: `gmem_abort`, `kvm_translate_vncr`, `kvm_mmu_faultin_pfn_gmem`, `__sev_snp_reload_vmsa`, `sev_handle_rmp_fault`, and `kvm_gmem_get_pfn`. Now, I need to figure out their entry points and call chains.

`kvm_gmem_get_pfn` appears to be an API function, which is useful. Same goes for `sev_handle_rmp_fault`. I should investigate the callers and how the data flows into them to see how they're exposed to the guest. Now, `gmem_abort` is called by `user_mem_abort` or something similar, right? Let me double-check how that works.

{
  "Expression": "gmem_abort"
}

{
  "Output": "arch/arm64/kvm/mmu.c=1600=struct kvm_s2_fault_desc {\n--\narch/arm64/kvm/mmu.c-1607-\narch/arm64/kvm/mmu.c:1608:static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)\narch/arm64/kvm/mmu.c-1609-{\n--\narch/arm64/kvm/mmu.c=2248=int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)\n--\narch/arm64/kvm/mmu.c-2419-\t\tif (kvm_slot_has_gmem(memslot))\narch/arm64/kvm/mmu.c:2420:\t\t\tret = gmem_abort(\u0026s2fd);\narch/arm64/kvm/mmu.c-2421-\t\telse\n"
}

gemini-3.1-pro-preview

null

null

							input: 7917
							output: 28
							thoughts: 60
						

Here's my understanding, as an expert in this area:

**Analyzing KVM Entry Points: ARM64 vs. x86**

Okay, so I'm looking at how KVM handles guest aborts and memory faults. It looks like `kvm_handle_guest_abort` is the key entry point for ARM64 architectures. That makes sense, it's the specific function for dealing with those unexpected events. Now, for x86, it's not quite the same. It looks like the path is through `kvm_mmu_faultin_pfn_gmem`, which is used by functions like `kvm_mmu_faultin_pfn` or something similar, and maybe others, related to page faults and memory management. So it seems like ARM64 and x86 take different routes to handle these similar low-level issues, one with a dedicated abort handler and the other by working through the MMU fault handlers. I'll need to dig deeper into the x86 code to pinpoint the exact calling structure.

{
  "Expression": "kvm_mmu_faultin_pfn_gmem"
}

{
  "Output": "arch/x86/kvm/mmu/mmu.c=4613=static void kvm_mmu_finish_page_fault(struct kvm_vcpu *vcpu,\n--\narch/x86/kvm/mmu/mmu.c-4619-\narch/x86/kvm/mmu/mmu.c:4620:static int kvm_mmu_faultin_pfn_gmem(struct kvm_vcpu *vcpu,\narch/x86/kvm/mmu/mmu.c-4621-\t\t\t\t    struct kvm_page_fault *fault)\n--\narch/x86/kvm/mmu/mmu.c=4643=static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu,\n--\narch/x86/kvm/mmu/mmu.c-4648-\tif (fault-\u003eis_private || kvm_memslot_is_gmem_only(fault-\u003eslot))\narch/x86/kvm/mmu/mmu.c:4649:\t\treturn kvm_mmu_faultin_pfn_gmem(vcpu, fault);\narch/x86/kvm/mmu/mmu.c-4650-\n"
}

gemini-3.1-pro-preview

null

null

							input: 8570
							output: 25
							thoughts: 47
						

Okay, here's my interpretation of that thought process, assuming I'm already deep in KVM internals:

**Investigating the Page Fault Handling Path in KVM**

Alright, I'm tracing through this fault handling logic. I see that `__kvm_mmu_faultin_pfn` is called by `kvm_mmu_faultin_pfn`. That makes sense; it's the internal worker function for the initial fault-in operation. But this has made me think... what's the role of `kvm_mmu_do_page_fault` in this whole flow? Is it a higher-level entry point? Is it called before or after this `faultin` sequence, or is it a completely separate path? I need to understand the relationship between these functions, and how they relate to the overall handling of page faults within the KVM MMU. I really need to map out the entire call graph to be sure. There's a chance they are completely unrelated but it seems unusual. It would be valuable to understand whether it is a potential optimization, or if one calls the other. Let's see...

{
  "Expression": "kvm_mmu_faultin_pfn"
}

{
  "Output": "arch/x86/kvm/mmu/mmu.c=4613=static void kvm_mmu_finish_page_fault(struct kvm_vcpu *vcpu,\n--\narch/x86/kvm/mmu/mmu.c-4619-\narch/x86/kvm/mmu/mmu.c:4620:static int kvm_mmu_faultin_pfn_gmem(struct kvm_vcpu *vcpu,\narch/x86/kvm/mmu/mmu.c-4621-\t\t\t\t    struct kvm_page_fault *fault)\n--\narch/x86/kvm/mmu/mmu.c-4642-\narch/x86/kvm/mmu/mmu.c:4643:static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu,\narch/x86/kvm/mmu/mmu.c-4644-\t\t\t\t struct kvm_page_fault *fault)\n--\narch/x86/kvm/mmu/mmu.c-4648-\tif (fault-\u003eis_private || kvm_memslot_is_gmem_only(fault-\u003eslot))\narch/x86/kvm/mmu/mmu.c:4649:\t\treturn kvm_mmu_faultin_pfn_gmem(vcpu, fault);\narch/x86/kvm/mmu/mmu.c-4650-\n--\narch/x86/kvm/mmu/mmu.c-4687-\narch/x86/kvm/mmu/mmu.c:4688:static int kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu,\narch/x86/kvm/mmu/mmu.c-4689-\t\t\t       struct kvm_page_fault *fault, unsigned int access)\n--\narch/x86/kvm/mmu/mmu.c-4781-\narch/x86/kvm/mmu/mmu.c:4782:\tret = __kvm_mmu_faultin_pfn(vcpu, fault);\narch/x86/kvm/mmu/mmu.c-4783-\tif (ret != RET_PF_CONTINUE)\n--\narch/x86/kvm/mmu/mmu.c=4840=static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)\n--\narch/x86/kvm/mmu/mmu.c-4858-\narch/x86/kvm/mmu/mmu.c:4859:\tr = kvm_mmu_faultin_pfn(vcpu, fault, ACC_ALL);\narch/x86/kvm/mmu/mmu.c-4860-\tif (r != RET_PF_CONTINUE)\n--\narch/x86/kvm/mmu/mmu.c=4935=static int kvm_tdp_mmu_page_fault(struct kvm_vcpu *vcpu,\n--\narch/x86/kvm/mmu/mmu.c-4950-\narch/x86/kvm/mmu/mmu.c:4951:\tr = kvm_mmu_faultin_pfn(vcpu, fault, ACC_ALL);\narch/x86/kvm/mmu/mmu.c-4952-\tif (r != RET_PF_CONTINUE)\n--\narch/x86/kvm/mmu/mmu_internal.h=226=struct kvm_page_fault {\n--\narch/x86/kvm/mmu/mmu_internal.h-278-\narch/x86/kvm/mmu/mmu_internal.h:279:\t/* Outputs of kvm_mmu_faultin_pfn().  */\narch/x86/kvm/mmu/mmu_internal.h-280-\tunsigned long mmu_seq;\n--\narch/x86/kvm/mmu/paging_tmpl.h=804=static int FNAME(page_fault)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)\n--\narch/x86/kvm/mmu/paging_tmpl.h-841-\narch/x86/kvm/mmu/paging_tmpl.h:842:\tr = kvm_mmu_faultin_pfn(vcpu, fault, walker.pte_access);\narch/x86/kvm/mmu/paging_tmpl.h-843-\tif (r != RET_PF_CONTINUE)\n"
}

gemini-3.1-pro-preview

null

null

							input: 10110
							output: 21
							thoughts: 302
						

**Fuzzing KVM Memory Management - Initial Thoughts**

Okay, so I've spotted a potential vulnerability with `kvm_gmem_get_pfn`. It's reachable from KVM page faults when `guest_memfd` is in use, which immediately flags it as a prime candidate for fuzzing. The key functions to investigate are: `kvm_gmem_get_pfn`, definitely. Also, I'll need to look closely at `sev_handle_rmp_fault`, and for ARM64, `kvm_handle_guest_abort`. Then, on x86, `kvm_mmu_do_page_fault` looks like a good entry point to trace from. Actually, wait - `kvm_gmem_get_pfn` is *the* API function, so that's where I need to start.

I'll check `kvm_gmem_get_pfn` in `virt/kvm/guest_memfd.c` first. Then I'll check `sev_handle_rmp_fault` in `arch/x86/kvm/svm/sev.c`. And I should also consider `kvm_translate_vncr`, which is in `arch/arm64/kvm/nested.c` to see if there's similar logic there.

To be precise, I will focus on these key functions:

*   `kvm_gmem_get_pfn`
*   `sev_handle_rmp_fault`
*   `kvm_translate_vncr`

Wait, `kvm_translate_vncr` is static, which makes me wonder if it's inlined. I need to be sure to check that.

{
  "Expression": "kvm_translate_vncr"
}

{
  "Output": "arch/arm64/kvm/nested.c=1407=static u64 read_vncr_el2(struct kvm_vcpu *vcpu)\n--\narch/arm64/kvm/nested.c-1411-\narch/arm64/kvm/nested.c:1412:static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)\narch/arm64/kvm/nested.c-1413-{\n--\narch/arm64/kvm/nested.c=1542=int kvm_handle_vncr_abort(struct kvm_vcpu *vcpu)\n--\narch/arm64/kvm/nested.c-1567-\narch/arm64/kvm/nested.c:1568:\tret = kvm_translate_vncr(vcpu, \u0026is_gmem);\narch/arm64/kvm/nested.c-1569-\tif (ret) {\n"
}

gemini-3.1-pro-preview

null

null

							input: 11082
							output: 24
							thoughts: 90
						

Here's my analysis of what I'm looking at, from my expert perspective:

**Debugging KVM/SEV-SNP Interactions**

Okay, so I'm diving into some KVM code and specifically focusing on the virtual NMI handling for SEV-SNP. The `kvm_handle_vncr_abort` function is the crucial entry point for `kvm_translate_vncr`, which is where I'll begin my investigation. My immediate next step is to examine the `gmem_abort` function. I know it's invoked by `kvm_handle_guest_abort`, which is likely where the abort signal is originating from. I suspect the issue could be related to memory access issues or some kind of guest-side interruption or exception that's triggering the abort. Next, I need to check the `__sev_snp_reload_vmsa` and the flow that invokes it – it appears to be called by `sev_snp_reload_vmsa` or a related function, which suggests a possible interaction with the VM state save/restore mechanism during an SEV-SNP protected operation. My hypothesis is that there might be a problem with the way we're handling the VMSA reload, possibly a race condition or a state mismatch that's triggering the abort. I need to trace the data flow through all of these calls to fully understand what's happening.

{
  "Expression": "__sev_snp_reload_vmsa"
}

{
  "Output": "arch/x86/kvm/svm/sev.c=3988=static int snp_begin_psc(struct vcpu_svm *svm)\n--\narch/x86/kvm/svm/sev.c-4027-\narch/x86/kvm/svm/sev.c:4028:static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)\narch/x86/kvm/svm/sev.c-4029-{\n--\narch/x86/kvm/svm/sev.c=4099=static void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu)\n--\narch/x86/kvm/svm/sev.c-4117-\narch/x86/kvm/svm/sev.c:4118:\t__sev_snp_reload_vmsa(vcpu, gpa);\narch/x86/kvm/svm/sev.c-4119-\n--\narch/x86/kvm/svm/sev.c=4130=void sev_snp_reload_vmsa(struct kvm_vcpu *vcpu)\n--\narch/x86/kvm/svm/sev.c-4135-\narch/x86/kvm/svm/sev.c:4136:\t__sev_snp_reload_vmsa(vcpu, sev_es-\u003esnp_guest_vmsa_gpa);\narch/x86/kvm/svm/sev.c-4137-}\n"
}

gemini-3.1-pro-preview

null

null

							input: 11905
							output: 25
							thoughts: 148
						

**My Initial Assessment of the Non-Static Entry Points**

Okay, so I'm diving into this code, and the first thing that jumps out is that `sev_snp_reload_vmsa` is the non-static entry point. That's my starting point. Now, I need a good understanding of what else is exposed. Let's get the lay of the land and list out the other non-static entry points so I can see the scope of what we're working with here.

Alright, here's what I've got:

*   `kvm_gmem_get_pfn`
*   `sev_handle_rmp_fault`
*   `sev_snp_reload_vmsa`
*   `kvm_handle_vncr_abort`
*   `kvm_handle_guest_abort` (specifically for ARM64, noted)
*   And finally, `kvm_mmu_do_page_fault` (for x86). Hmm... `kvm_mmu_do_page_fault`... I need to double-check that; I'm betting that's either a macro or a function, but I need to confirm whether this is a macro or function.

{
  "Expression": "kvm_mmu_do_page_fault"
}

{
  "Output": "arch/x86/kvm/mmu/mmu.c=4970=static int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)\n--\narch/x86/kvm/mmu/mmu.c-4979-\narch/x86/kvm/mmu/mmu.c:4980:static int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,\narch/x86/kvm/mmu/mmu.c-4981-\t\t\t\t u64 err, bool prefetch, int *emulation_type,\n--\narch/x86/kvm/mmu/mmu.c=5045=static int kvm_tdp_page_prefault(struct kvm_vcpu *vcpu, gpa_t gpa,\n--\narch/x86/kvm/mmu/mmu.c-5064-\t\tcond_resched();\narch/x86/kvm/mmu/mmu.c:5065:\t\tr = kvm_mmu_do_page_fault(vcpu, gpa, error_code, true, NULL, level);\narch/x86/kvm/mmu/mmu.c-5066-\t} while (r == RET_PF_RETRY);\n--\narch/x86/kvm/mmu/mmu.c=5135=void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)\n--\narch/x86/kvm/mmu/mmu.c-5153-\narch/x86/kvm/mmu/mmu.c:5154:\tr = kvm_mmu_do_page_fault(vcpu, work-\u003ecr2_or_gpa, work-\u003earch.error_code,\narch/x86/kvm/mmu/mmu.c-5155-\t\t\t\t  true, NULL, NULL);\n--\narch/x86/kvm/mmu/mmu.c=6567=int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code,\n--\narch/x86/kvm/mmu/mmu.c-6602-\narch/x86/kvm/mmu/mmu.c:6603:\t\tr = kvm_mmu_do_page_fault(vcpu, cr2_or_gpa, error_code, false,\narch/x86/kvm/mmu/mmu.c-6604-\t\t\t\t\t  \u0026emulation_type, NULL);\n--\narch/x86/kvm/mmu/mmu.c-6623-\t/*\narch/x86/kvm/mmu/mmu.c:6624:\t * None of handle_mmio_page_fault(), kvm_mmu_do_page_fault(), or\narch/x86/kvm/mmu/mmu.c-6625-\t * kvm_mmu_write_protect_fault() return RET_PF_CONTINUE.\narch/x86/kvm/mmu/mmu.c:6626:\t * kvm_mmu_do_page_fault() only uses RET_PF_CONTINUE internally to\narch/x86/kvm/mmu/mmu.c-6627-\t * indicate continuing the page fault handling until to the final\n--\narch/x86/kvm/mmu/mmu_internal.h=226=struct kvm_page_fault {\narch/x86/kvm/mmu/mmu_internal.h:227:\t/* arguments to kvm_mmu_do_page_fault.  */\narch/x86/kvm/mmu/mmu_internal.h-228-\tconst gpa_t addr;\n--\narch/x86/kvm/mmu/mmu_internal.h-294- * Return values of handle_mmio_page_fault(), mmu.page_fault(), fast_page_fault(),\narch/x86/kvm/mmu/mmu_internal.h:295: * and of course kvm_mmu_do_page_fault().\narch/x86/kvm/mmu/mmu_internal.h-296- *\n--\narch/x86/kvm/mmu/mmu_internal.h=312=enum {\n--\narch/x86/kvm/mmu/mmu_internal.h-325- *   \"TEST %rax, %rax, JNZ\", as all \"stop!\" values are non-zero,\narch/x86/kvm/mmu/mmu_internal.h:326: * - kvm_mmu_do_page_fault() to return other RET_PF_* as a positive value.\narch/x86/kvm/mmu/mmu_internal.h-327- */\n"
}

gemini-3.1-pro-preview

null

null

							input: 13649
							output: 24
							thoughts: 278
						

**Analyzing the x86 Page Fault Handler**

Okay, so I'm diving into `kvm_mmu_page_fault`, which is the entry point for handling page faults on x86, the core of the issue. That immediately points me to a specific set of functions I need to scrutinize more closely: `kvm_gmem_get_pfn`, `sev_handle_rmp_fault`, `sev_snp_reload_vmsa`, `kvm_handle_vncr_abort`, `kvm_handle_guest_abort`, and of course, the handler itself, `kvm_mmu_page_fault`. These are the key players in this fault handling scenario.

My first check is to verify if `kvm_gmem_get_pfn` is static or exported. Ah, good, it's non-static and resides within `virt/kvm/guest_memfd.c`, meaning I can readily access and examine it.

Now, let's circle back to the configurations surrounding this. I need to understand the dependencies. I see that `KVM_GUEST_MEMFD` is selected for both ARM64 and x86_64, but it's not a user-selectable option, which is important to remember. It's actually selected through `KVM_GENERIC_MEMORY_ATTRIBUTES`, or `KVM_SW_PROTECTED_VM`, or just `KVM` itself for those architectures. I need to now determine if `KVM_SW_PROTECTED_VM` is a necessary configuration, as this would impact my understanding of the system's behavior and this page fault's context.

{
  "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: 14420
							output: 23
							thoughts: 78
						

Here's my summary, as I see it:

**Examining KVM and Guest Memory Protection on x86**

Okay, so I'm digging into how guest memory is handled, specifically within the x86 architecture and KVM. I'm focusing on software-protected VMs, and I see that `KVM_SW_PROTECTED_VM` is the flag that enables `guest_memfd` for these VMs. But then I'm thinking, isn't `KVM_GUEST_MEMFD` already implicitly selected by `KVM_X86` if we're on `X86_64`? That seems potentially redundant or maybe there's a specific nuance I'm missing. Time to go right to the source. I need to check the Kconfig file for the x86 architecture, specifically `arch/x86/kvm/Kconfig`, to clarify the dependencies and relationships between these configuration options. I need to understand what's *really* going on.

{
  "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: 14948
							output: 22
							thoughts: 67
						

**KVM Configuration for SEV**

Okay, so looking at this, it seems that if we're on an x86-64 system, `KVM_GUEST_MEMFD` is automatically included by `KVM_X86`. That simplifies things. We can assume that if `X86_64` is set correctly, then `KVM_GUEST_MEMFD` will be configured as part of the existing `KVM_X86` configuration.

Therefore, for Secure Encrypted Virtualization (SEV) to work, we really just need `KVM` enabled, and then `KVM_AMD` as that seems to be the critical dependency for our AMD hardware.

Now, the next thing to verify is that `KVM_AMD_SEV` is also properly configured and enabled. I need to make sure that the SEV-specific pieces are also taken care of properly. Let's dig into that and confirm the `KVM_AMD_SEV` setting.

{
  "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: 15365
							output: 32
							thoughts: 498
						

**My Thought Process on KVM Configuration and Function Selection**

Okay, so I'm thinking about the optimal configuration and key functions to include here. `KVM_AMD_SEV` is definitely a good choice, and of course, the base `KVM` configuration itself.

So, let's list those out:
Configs:
- `KVM`
- `KVM_AMD_SEV`

Wait, just to clarify, `KVM` will cover ARM64, so that's all I need there.

Now, let's move on to the functions. I've got a few: `kvm_gmem_get_pfn`, `sev_handle_rmp_fault`, `sev_snp_reload_vmsa`, `kvm_handle_vncr_abort`, `kvm_handle_guest_abort`, and `kvm_mmu_page_fault`.

Hmm, hold on. I remember the instructions, "Avoid listing generic hot-path functions to prevent skewed test distributions." Right, `kvm_handle_guest_abort` and `kvm_mmu_page_fault` are *very* hot paths, so those are out.

Okay, let's re-evaluate. I can list the remaining functions: `kvm_gmem_get_pfn`, `sev_handle_rmp_fault`, `sev_snp_reload_vmsa`, `kvm_handle_vncr_abort`. Those should be specific enough.

Now, I should double-check that those remaining functions aren't overly general. `kvm_handle_vncr_abort` handles nested virtualization VNCR aborts – that's specific. `sev_handle_rmp_fault` handles RMP faults, also not a generic hot path. `sev_snp_reload_vmsa` is for SEV-SNP VMSA reload, again, specific. And `kvm_gmem_get_pfn` is the core function I modified, called when faulting in guest_memfd pages. It's perfectly specific to that.

So, my final FocusSymbols should be:

- `kvm_gmem_get_pfn`
- `sev_handle_rmp_fault`
- `sev_snp_reload_vmsa`
- `kvm_handle_vncr_abort`

Let me just quickly check that `kvm_gmem_get_pfn` is exported.

no matches

{
  "Expression": "EXPORT_SYMBOL_GPL\\(kvm_gmem_get_pfn\\)"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 16450
							output: 25
							thoughts: 45
						

Okay, here's my interpretation of those thoughts, presented as my own mental process, given my expertise:

**Examining the Guest Memfd Implementation in KVM**

Alright, so the clue is that whatever this relates to isn't *exported*, which is important context. The fact that it's *non-static* in `virt/kvm/guest_memfd.c` is significant. That strongly suggests it's a file, but something local to the KVM virtualisation, and there's definitely some local variable interaction there. My immediate action is to dive into `virt/kvm/guest_memfd.c`. I need to understand what this non-static element is, how it's being used, and what its relationship is to any external interfaces, considering it's not exported. Time to go spelunking in the code! Let's see what's actually going on in that specific file.

{
  "Expression": "int kvm_gmem_get_pfn"
}

{
  "Output": "include/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=717=static struct folio *__kvm_gmem_get_pfn(struct file *file,\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"
}

gemini-3.1-pro-preview

null

null

							input: 17132
							output: 24
							thoughts: 106
						

**Analyzing the Configuration Landscape**

Okay, so this is definitely a global function, got it. Let me see... the current configuration options are `KVM` and `KVM_AMD_SEV`. Hmm, but wait a second. I think `KVM_SW_PROTECTED_VM` could actually be incredibly useful for testing `guest_memfd` on x86 architectures, even without SEV or TDX. That would open up a whole new avenue for experimentation and validation.

Right, so let's add `KVM_SW_PROTECTED_VM` to the `EnableConfigs` list. I need to make sure this is actually a valid config, though. Gotta double-check that this is a recognized and supported option before I get too carried away. I don't want to chase a dead end.

{
  "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: 17544
							output: 196
							thoughts: 146
						

**My Assessment of the KVM Patch**

Okay, yes, I've got it. This is a significant change. So, the key here is these EnableConfigs: `KVM`, `KVM_AMD_SEV`, and `KVM_SW_PROTECTED_VM`. The patch fundamentally alters how `kvm_gmem_get_pfn` functions. Specifically, it's ditching the `struct page **page` argument and, crucially, it's dropping the folio reference prior to returning. I can immediately see the implications.

This affects how KVM manages memory backing specifically for `guest_memfd`. And we all know `guest_memfd` is foundational for confidential computing. We're talking SEV-SNP, TDX, and ARM CCA – all of the big players. The changes are triggered through KVM ioctls and page faults when utilizing `guest_memfd`. I need to ensure this is handled correctly. Let's call set-results.

{
  "EnableConfigs": [
    "KVM",
    "KVM_AMD_SEV",
    "KVM_SW_PROTECTED_VM"
  ],
  "FocusSymbols": [
    "kvm_gmem_get_pfn",
    "sev_handle_rmp_fault",
    "sev_snp_reload_vmsa",
    "kvm_handle_vncr_abort"
  ],
  "Reasoning": "The patch changes the signature and behavior of `kvm_gmem_get_pfn` by removing the `struct page **page` argument and dropping the folio reference before returning. This affects how KVM handles memory backing for guest_memfd, which is a core feature for confidential computing (SEV-SNP, TDX, ARM CCA). The changes are reachable via KVM ioctls and page faults when using guest_memfd.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "KVM",
    "KVM_AMD_SEV",
    "KVM_SW_PROTECTED_VM"
  ],
  "FocusSymbols": [
    "kvm_gmem_get_pfn",
    "sev_handle_rmp_fault",
    "sev_snp_reload_vmsa",
    "kvm_handle_vncr_abort"
  ],
  "Reasoning": "The patch changes the signature and behavior of `kvm_gmem_get_pfn` by removing the `struct page **page` argument and dropping the folio reference before returning. This affects how KVM handles memory backing for guest_memfd, which is a core feature for confidential computing (SEV-SNP, TDX, ARM CCA). The changes are reachable via KVM ioctls and page faults when using guest_memfd.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

best-expensive

null

{
  "KMSANReasoning": "The patch refactors `kvm_gmem_get_pfn()` to remove the `struct page **page` argument and drops the associated page reference counting (`kvm_release_faultin_page`, `kvm_release_page_clean`, etc.) across multiple architectures (arm64, x86). This is a memory management and refcounting change. There are no new structures sent to user space, no new uninitialized memory allocations, and no info-leaks. Any bugs introduced by this change would likely be use-after-free, memory leaks, or NULL pointer dereferences, which are effectively caught by KASAN and other standard debugging tools. Therefore, a dedicated KMSAN fuzzing session is not required.",
  "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 00fceae410c054105ee6e96a37b41661e3e2a1bf
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Aug 26 09:19:42 2026 +0000

    syz-cluster: applied patch under review

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 9ba86450fe4af..d57f8181f1b7d 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 17123f0b6daba..dd62840d36741 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -1415,7 +1415,7 @@ 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;
 
@@ -1471,7 +1471,7 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)
 			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 064ecc33b9267..947c9cd843450 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4628,7 +4628,7 @@ 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 5705723f1f412..0a887f8e05d3a 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4032,7 +4032,6 @@ 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);
@@ -4076,7 +4075,7 @@ 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);
@@ -4092,8 +4091,6 @@ 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);
 }
 
 /*
@@ -5019,7 +5016,7 @@ 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;
@@ -5046,7 +5043,10 @@ 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);
@@ -5055,9 +5055,13 @@ 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;
 	}
 
 	/*
@@ -5085,26 +5089,31 @@ 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: 5589
							output: 179
							thoughts: 1270
						

**Refactoring KVM Guest Memory Page Handling**

Okay, so this patch is clearly refactoring how KVM manages guest memory pages. My initial observation is that `kvm_gmem_get_pfn()` is the target, specifically the removal of the `struct page **page` argument. This impacts several architectures (arm64, x86). It seems like the core idea is to change how the page reference is handled, moving away from returning it directly from `kvm_gmem_get_pfn()` and instead using `folio_put(folio);` within the function itself. This likely means the calling functions no longer need to explicitly release the page.

My primary concern, as always, is uninitialized memory. With this kind of change, I need to ensure there are no unintended information leaks or uninitialized memory use as a result of the refactoring. Looking at the changes, there aren't any new structures being sent to userspace. There's no indication of any new allocations that might introduce uninitialized data. This is squarely a memory management and refcounting change. The most likely risks are use-after-free or refcount bugs, so this is where I need to focus. I'm relying on KASAN to catch these.

Let's do a quick code review of the diff. The function signature changes are pretty straightforward: the `page` argument is gone. Okay, I see where this `page` argument was previously being populated, `folio_file_page(folio, index)`. Now, that call site is replaced with the `folio_put(folio)` call. The corresponding `kvm_release_page_*` calls are gone, which makes sense. I see these changes in `arch/arm64/kvm/mmu.c`, `arch/arm64/kvm/nested.c` and in various x86 files such as `arch/x86/kvm/mmu/mmu.c`, and `arch/x86/kvm/svm/sev.c`.

A key thing is that in x86, there was a `fault->refcounted_page` variable that was being passed. But now the function doesn't return the page, so is `fault->refcounted_page` properly handled? If it's NULL, then the `kvm_release_faultin_page` will just do nothing, so this looks safe, even if it leads to an issue in terms of a leak.  It should be initialized to NULL in `kvm_mmu_do_page_fault`. No deep dive is necessary here, even if it introduces a bug, it's just a NULL pointer dereference or memory leak and KASAN should handle. The same thing for the rest of the cases where `kvm_release_page_*` calls were removed.

Finally, looking at `virt/kvm/guest_memfd.c`, it confirms the refactoring is about how `guest_memfd` manages page references. Instead of checking if `r` and assigning the page, the patch calls `folio_put(folio);` directly.

Overall, this is a clean refactoring, specifically in page reference counting for guest memory, especially for `guest_memfd`. There's no evidence of uninitialized memory exposure or usage from this patch. Based on this analysis, I'm confident KASAN and kmemleak are sufficient to catch any issues related to use-after-free or memory leaks. So, I will set `NeedsKMSAN=false` and provide the reasoning.

{
  "KMSANReasoning": "The patch refactors `kvm_gmem_get_pfn()` to remove the `struct page **page` argument and drops the associated page reference counting (`kvm_release_faultin_page`, `kvm_release_page_clean`, etc.) across multiple architectures (arm64, x86). This is a memory management and refcounting change. There are no new structures sent to user space, no new uninitialized memory allocations, and no info-leaks. Any bugs introduced by this change would likely be use-after-free, memory leaks, or NULL pointer dereferences, which are effectively caught by KASAN and other standard debugging tools. Therefore, a dedicated KMSAN fuzzing session is not required.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch refactors `kvm_gmem_get_pfn()` to remove the `struct page **page` argument and drops the associated page reference counting (`kvm_release_faultin_page`, `kvm_release_page_clean`, etc.) across multiple architectures (arm64, x86). This is a memory management and refcounting change. There are no new structures sent to user space, no new uninitialized memory allocations, and no info-leaks. Any bugs introduced by this change would likely be use-after-free, memory leaks, or NULL pointer dereferences, which are effectively caught by KASAN and other standard debugging tools. Therefore, a dedicated KMSAN fuzzing session is not required.",
  "NeedsKMSAN": false
}