KVM: x86/mmu: Print SPTEs on unexpected #VE

Print the SPTEs that correspond to the faulting GPA on an unexpected EPT
Violation #VE to help the user debug failures, e.g. to pinpoint which SPTE
didn't have SUPPRESS_VE set.

Opportunistically assert that the underlying exit reason was indeed an EPT
Violation, as the CPU has *really* gone off the rails if a #VE occurs due
to a completely unexpected exit reason.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240518000430.1118488-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: sean-jc

arch/x86/include/asm/kvm_host.h

@@ -2154,6 +2154,7 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu);
 
 int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code,
 		       void *insn, int insn_len);
+void kvm_mmu_print_sptes(struct kvm_vcpu *vcpu, gpa_t gpa, const char *msg);
 void kvm_mmu_invlpg(struct kvm_vcpu *vcpu, gva_t gva);
 void kvm_mmu_invalidate_addr(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
 			     u64 addr, unsigned long roots);

arch/x86/kvm/mmu/mmu.c

@@ -4104,23 +4104,31 @@ static int get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, int *root_level
 	return leaf;
 }
 
-/* return true if reserved bit(s) are detected on a valid, non-MMIO SPTE. */
-static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
+static int get_sptes_lockless(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes,
+			      int *root_level)
 {
-	u64 sptes[PT64_ROOT_MAX_LEVEL + 1];
-	struct rsvd_bits_validate *rsvd_check;
-	int root, leaf, level;
-	bool reserved = false;
+	int leaf;
 
 	walk_shadow_page_lockless_begin(vcpu);
 
 	if (is_tdp_mmu_active(vcpu))
-		leaf = kvm_tdp_mmu_get_walk(vcpu, addr, sptes, &root);
+		leaf = kvm_tdp_mmu_get_walk(vcpu, addr, sptes, root_level);
 	else
-		leaf = get_walk(vcpu, addr, sptes, &root);
+		leaf = get_walk(vcpu, addr, sptes, root_level);
 
 	walk_shadow_page_lockless_end(vcpu);
+	return leaf;
+}
 
+/* return true if reserved bit(s) are detected on a valid, non-MMIO SPTE. */
+static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
+{
+	u64 sptes[PT64_ROOT_MAX_LEVEL + 1];
+	struct rsvd_bits_validate *rsvd_check;
+	int root, leaf, level;
+	bool reserved = false;
+
+	leaf = get_sptes_lockless(vcpu, addr, sptes, &root);
 	if (unlikely(leaf < 0)) {
 		*sptep = 0ull;
 		return reserved;
@@ -5924,6 +5932,22 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_page_fault);
 
+void kvm_mmu_print_sptes(struct kvm_vcpu *vcpu, gpa_t gpa, const char *msg)
+{
+	u64 sptes[PT64_ROOT_MAX_LEVEL + 1];
+	int root_level, leaf, level;
+
+	leaf = get_sptes_lockless(vcpu, gpa, sptes, &root_level);
+	if (unlikely(leaf < 0))
+		return;
+
+	pr_err("%s %llx", msg, gpa);
+	for (level = root_level; level >= leaf; level--)
+		pr_cont(", spte[%d] = 0x%llx", level, sptes[level]);
+	pr_cont("\n");
+}
+EXPORT_SYMBOL_GPL(kvm_mmu_print_sptes);
+
 static void __kvm_mmu_invalidate_addr(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
 				      u64 addr, hpa_t root_hpa)
 {

arch/x86/kvm/vmx/vmx.c

@@ -5218,7 +5218,12 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
 		return handle_ud(vcpu);
 
 	if (WARN_ON_ONCE(is_ve_fault(intr_info))) {
+		struct vmx_ve_information *ve_info = vmx->ve_info;
+
+		WARN_ONCE(ve_info->exit_reason != EXIT_REASON_EPT_VIOLATION,
+			  "Unexpected #VE on VM-Exit reason 0x%x", ve_info->exit_reason);
 		dump_vmcs(vcpu);
+		kvm_mmu_print_sptes(vcpu, ve_info->guest_physical_address, "#VE");
 		return 1;
 	}