Messages in this thread Patch in this message | | | From | Paolo Bonzini <> | Subject | [PATCH v2 2/2] KVM: VMX: mark RDMSR path as unlikely | Date | Thu, 22 Feb 2018 16:43:18 +0100 |
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vmx_vcpu_run and svm_vcpu_run are large functions, and this can actually make a substantial cycle difference by keeping the fast path contiguous in memory. Without it, the retpoline guest/retpoline host case is about 50 cycles slower.
Cc: x86@kernel.org Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: KarimAllah Ahmed <karahmed@amazon.de> Cc: David Woodhouse <dwmw@amazon.co.uk> Cc: Jim Mattson <jmattson@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: stable@vger.kernel.org Reviewed-by: Jim Mattson <jmattson@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- arch/x86/kvm/svm.c | 2 +- arch/x86/kvm/vmx.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 1598beeda11c..24c9521ebc24 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -5465,7 +5465,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) * If the L02 MSR bitmap does not intercept the MSR, then we need to * save it. */ - if (!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL)) + if (unlikely(!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL))) svm->spec_ctrl = native_read_msr(MSR_IA32_SPEC_CTRL); if (svm->spec_ctrl) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index af89d377681d..e13fd2a833c4 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -9589,7 +9589,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) * If the L02 MSR bitmap does not intercept the MSR, then we need to * save it. */ - if (!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL)) + if (unlikely(!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL))) vmx->spec_ctrl = native_read_msr(MSR_IA32_SPEC_CTRL); if (vmx->spec_ctrl) -- 1.8.3.1
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