[PATCH 2/2] kvm: x86: Use AMD CPUID semantics for AMD vCPUs

[Jim Mattson <jmattson@google.com>]

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 <jmattson@google.com>
Fixes: bd22f5cfcfe8f6 ("KVM: move and fix substitue search for missing CPUID entries")
Reviewed-by: Marc Orr <marcorr@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Reviewed-by: Jacob Xu <jacobhxu@google.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/cpuid.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 35e2f930a4b79..0377d2820a7aa 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -988,9 +988,11 @@ 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;
-- 
2.23.0.351.gc4317032e6-goog