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: x...@kernel.org
Cc: Radim Krčmář <rkrc...@redhat.com>
Cc: KarimAllah Ahmed <karah...@amazon.de>
Cc: David Woodhouse <d...@amazon.co.uk>
Cc: Jim Mattson <jmatt...@google.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: sta...@vger.kernel.org
Reviewed-by: Jim Mattson <jmatt...@google.com>
Signed-off-by: Paolo Bonzini <pbonz...@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
