kvm: x86: Use AMD CPUID semantics for AMD vCPUs

When the guest CPUID information represents an AMD vCPU, return all
zeroes for queries of undefined CPUID leaves, whether or not they are
in range.

Signed-off-by: Jim Mattson <[email protected]>
Fixes: bd22f5c ("KVM: move and fix substitue search for missing CPUID entries")
Reviewed-by: Marc Orr <[email protected]>
Reviewed-by: Peter Shier <[email protected]>
Reviewed-by: Jacob Xu <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

Author: jsmattsonjr

arch/x86/kvm/cpuid.c

@@ -998,9 +998,11 @@ bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
 	/*
 	 * Intel CPUID semantics treats any query for an out-of-range
 	 * leaf as if the highest basic leaf (i.e. CPUID.0H:EAX) were
-	 * requested.
+	 * requested. AMD CPUID semantics returns all zeroes for any
+	 * undefined leaf, whether or not the leaf is in range.
 	 */
-	if (!entry && check_limit && !cpuid_function_in_range(vcpu, function)) {
+	if (!entry && check_limit && !guest_cpuid_is_amd(vcpu) &&
+	    !cpuid_function_in_range(vcpu, function)) {
 		max = kvm_find_cpuid_entry(vcpu, 0, 0);
 		if (max) {
 			function = max->eax;