KVM/VMX: Optimize vmx_vcpu_run() and svm_vcpu_run() by marking the RDMSR path as...
authorPaolo Bonzini <pbonzini@redhat.com>
Thu, 22 Feb 2018 15:43:18 +0000 (16:43 +0100)
committerIngo Molnar <mingo@kernel.org>
Fri, 23 Feb 2018 07:24:36 +0000 (08:24 +0100)
commit946fbbc13dce68902f64515b610eeb2a6c3d7a64
treeed811ec9d486d9a589fd3d4ef3bd04620a3ab75f
parentecb586bd29c99fb4de599dec388658e74388daad
KVM/VMX: Optimize vmx_vcpu_run() and svm_vcpu_run() by marking the RDMSR path as unlikely()

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>
arch/x86/kvm/svm.c
arch/x86/kvm/vmx.c