From: Sean Christopherson Date: Wed, 11 Dec 2024 01:33:00 +0000 (-0800) Subject: KVM: x86: Apply TSX_CTRL_CPUID_CLEAR if and only if the vCPU has RTM or HLE X-Git-Tag: v6.15-rc1~195^2~10^2~18 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7e9f735e7ac4b95207e108ec67d04a9c4cb9cced;p=thirdparty%2Fkernel%2Flinux.git KVM: x86: Apply TSX_CTRL_CPUID_CLEAR if and only if the vCPU has RTM or HLE When emulating CPUID, retrieve MSR_IA32_TSX_CTRL.TSX_CTRL_CPUID_CLEAR if and only if RTM and/or HLE feature bits need to be cleared. Getting the MSR value is unnecessary if neither bit is set, and avoiding the lookup saves ~80 cycles for vCPUs without RTM or HLE. Cc: Jim Mattson Reviewed-by: Jim Mattson Link: https://lore.kernel.org/r/20241211013302.1347853-4-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index a57fa0123c773..0de3f581ef124 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -1999,7 +1999,8 @@ bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, *edx = entry->edx; if (function == 7 && index == 0) { u64 data; - if (!__kvm_get_msr(vcpu, MSR_IA32_TSX_CTRL, &data, true) && + if ((*ebx & (feature_bit(RTM) | feature_bit(HLE))) && + !__kvm_get_msr(vcpu, MSR_IA32_TSX_CTRL, &data, true) && (data & TSX_CTRL_CPUID_CLEAR)) *ebx &= ~(feature_bit(RTM) | feature_bit(HLE)); } else if (function == 0x80000007) {