diff mbox series

[v3,01/57] KVM: x86: Use feature_bit() to clear CONSTANT_TSC when emulating CPUID

Message ID 20241128013424.4096668-2-seanjc@google.com (mailing list archive)
State New
Headers show
Series KVM: x86: CPUID overhaul, fixes, and caching | expand

Commit Message

Sean Christopherson Nov. 28, 2024, 1:33 a.m. UTC 
When clearing CONSTANT_TSC during CPUID emulation due to a Hyper-V quirk,
use feature_bit() instead of SF() to ensure the bit is actually cleared.
SF() evaluates to zero if the _host_ doesn't support the feature.  I.e.
KVM could keep the bit set if userspace advertised CONSTANT_TSC despite
it not being supported in hardware.

Note, translating from a scattered feature to a the hardware version is
done by __feature_translate(), not SF().  The sole purpose of SF() is to
check kernel support for the scattered feature, *before* translation.

Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/cpuid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 097bdc022d0f..776f24408fa3 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1630,7 +1630,7 @@  bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
 				*ebx &= ~(F(RTM) | F(HLE));
 		} else if (function == 0x80000007) {
 			if (kvm_hv_invtsc_suppressed(vcpu))
-				*edx &= ~SF(CONSTANT_TSC);
+				*edx &= ~feature_bit(CONSTANT_TSC);
 		}
 	} else {
 		*eax = *ebx = *ecx = *edx = 0;