linux-kernel - [PATCH 04/10] KVM: x86: Apply Intel's TSC_AUX reserved-bit behavior to Intel compat vCPUs

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Date: Fri,  5 Apr 2024 16:55:57 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Sandipan Das <sandipan.das@....com>, Jim Mattson <jmattson@...gle.com>, 
	Like Xu <like.xu.linux@...il.com>
Subject: [PATCH 04/10] KVM: x86: Apply Intel's TSC_AUX reserved-bit behavior
 to Intel compat vCPUs

Extend Intel's check on MSR_TSC_AUX[63:32] to all vCPU models that are
Intel compatible, i.e. aren't AMD or Hygon in KVM's world, as the behavior
is architectural, i.e. applies to any CPU that is compatible with Intel's
architecture.  Applying the behavior strictly to Intel wasn't intentional,
KVM simply didn't have a concept of "Intel compatible" as of commit
61a05d444d2c ("KVM: x86: Tie Intel and AMD behavior for MSR_TSC_AUX to
guest CPU model").

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/x86.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ebcc12d1e1de..d9719141502a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1883,11 +1883,11 @@ static int __kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data,
 		 * incomplete and conflicting architectural behavior.  Current
 		 * AMD CPUs completely ignore bits 63:32, i.e. they aren't
 		 * reserved and always read as zeros.  Enforce Intel's reserved
-		 * bits check if and only if the guest CPU is Intel, and clear
-		 * the bits in all other cases.  This ensures cross-vendor
-		 * migration will provide consistent behavior for the guest.
+		 * bits check if the guest CPU is Intel compatible, otherwise
+		 * clear the bits.  This ensures cross-vendor migration will
+		 * provide consistent behavior for the guest.
 		 */
-		if (guest_cpuid_is_intel(vcpu) && (data >> 32) != 0)
+		if (guest_cpuid_is_intel_compatible(vcpu) && (data >> 32) != 0)
 			return 1;
 
 		data = (u32)data;
-- 
2.44.0.478.gd926399ef9-goog