linux-kernel - [PATCH AUTOSEL 4.14 07/21] kvm: x86: Use AMD CPUID semantics for AMD vCPUs

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Date:   Wed,  9 Oct 2019 13:06:00 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jim Mattson <jmattson@...gle.com>, Marc Orr <marcorr@...gle.com>,
        Peter Shier <pshier@...gle.com>,
        Jacob Xu <jacobhxu@...gle.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>, kvm@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 07/21] kvm: x86: Use AMD CPUID semantics for AMD vCPUs

From: Jim Mattson <jmattson@...gle.com>

[ Upstream commit 5f41a37b151f6459e0b650a2f4d1d59b6c02d1ab ]

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@...gle.com>
Fixes: bd22f5cfcfe8f6 ("KVM: move and fix substitue search for missing CPUID entries")
Reviewed-by: Marc Orr <marcorr@...gle.com>
Reviewed-by: Peter Shier <pshier@...gle.com>
Reviewed-by: Jacob Xu <jacobhxu@...gle.com>
Cc: Sean Christopherson <sean.j.christopherson@...el.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 f3c49dc423895..3d480ec143284 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -893,9 +893,11 @@ 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;
-- 
2.20.1