1 files changed, 25 insertions, 6 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4a1ba05f7af..934b4c6b0bf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4958,12 +4958,6 @@ struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
                         best = e;
                         break;
                 }
-                /*
-                 * Both basic or both extended?
-                 */
-                if (((e->function ^ function) & 0x80000000) == 0)
-                        if (!best || e->function > best->function)
-                                best = e;
         }
         return best;
 }
@@ -4983,6 +4977,27 @@ not_found:
         return 36;
 }
 
+/*
+ * If no match is found, check whether we exceed the vCPU's limit
+ * and return the content of the highest valid _standard_ leaf instead.
+ * This is to satisfy the CPUID specification.
+ */
+static struct kvm_cpuid_entry2* check_cpuid_limit(struct kvm_vcpu *vcpu,
+                                                  u32 function, u32 index)
+{
+        struct kvm_cpuid_entry2 *maxlevel;
+
+        maxlevel = kvm_find_cpuid_entry(vcpu, function & 0x80000000, 0);
+        if (!maxlevel || maxlevel->eax >= function)
+                return NULL;
+        if (function & 0x80000000) {
+                maxlevel = kvm_find_cpuid_entry(vcpu, 0, 0);
+                if (!maxlevel)
+                        return NULL;
+        }
+        return kvm_find_cpuid_entry(vcpu, maxlevel->eax, index);
+}
+
 void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
 {
         u32 function, index;
@@ -4995,6 +5010,10 @@ void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
         kvm_register_write(vcpu, VCPU_REGS_RCX, 0);
         kvm_register_write(vcpu, VCPU_REGS_RDX, 0);
         best = kvm_find_cpuid_entry(vcpu, function, index);
+
+        if (!best)
+                best = check_cpuid_limit(vcpu, function, index);
+
         if (best) {
                 kvm_register_write(vcpu, VCPU_REGS_RAX, best->eax);
                 kvm_register_write(vcpu, VCPU_REGS_RBX, best->ebx);