diff options
| author | Paolo Bonzini <pbonzini@redhat.com> | 2018-02-22 16:43:18 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-03-08 22:47:48 -0800 |
| commit | 100b8cbd68b1239656d83d27c2d49195e1a15795 (patch) | |
| tree | e37e2e16bba40f43fc524d7c3d37ec9768e6cc85 | |
| parent | 16f7730b611a675a23eb0b0f3690f3f60c386989 (diff) | |
KVM/VMX: Optimize vmx_vcpu_run() and svm_vcpu_run() by marking the RDMSR path as unlikely()
commit 946fbbc13dce68902f64515b610eeb2a6c3d7a64 upstream.
vmx_vcpu_run() and svm_vcpu_run() are large functions, and giving
branch hints to the compiler can actually make a substantial cycle
difference by keeping the fast path contiguous in memory.
With this optimization, the retpoline-guest/retpoline-host case is
about 50 cycles faster.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: KarimAllah Ahmed <karahmed@amazon.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm@vger.kernel.org
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20180222154318.20361-3-pbonzini@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/kvm/svm.c | 2 | ||||
| -rw-r--r-- | 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 426c816657d0..3505afabce5d 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -5139,7 +5139,7 @@ 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 5b29df629c3f..87b453eeae40 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -9579,7 +9579,7 @@ 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) |