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KVM: x86: Use feature_bit() to clear CONSTANT_TSC when emulating CPUID

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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>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-11-27 17:33:28 -08:00
parent 9af04539d4
commit ccf4c1d15d
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kvm/cpuid.c
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@ -1651,7 +1651,7 @@ 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;