From: Sean Christopherson Date: Thu, 28 Nov 2024 01:33:28 +0000 (-0800) Subject: KVM: x86: Use feature_bit() to clear CONSTANT_TSC when emulating CPUID X-Git-Tag: v6.14-rc1~94^2~4^2~67 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ccf4c1d15d5a593bb3a50911ce3e8bb373feddc5;p=thirdparty%2Fkernel%2Flinux.git KVM: x86: Use feature_bit() to clear CONSTANT_TSC when emulating CPUID 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 Reviewed-by: Vitaly Kuznetsov Link: https://lore.kernel.org/r/20241128013424.4096668-2-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index ae0b438a2c991..701bbbf581243 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -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;