Messages in this thread | | | Subject | Re: [PATCH] KVM: x86: avoid unnecessary XSETBV on guest entry | From | Quan Xu <> | Date | Thu, 14 Dec 2017 11:27:27 +0800 |
| |
On 2017/12/13 20:51, Paolo Bonzini wrote: > xsetbv can be expensive when running on nested virtualization, try to > avoid it. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > arch/x86/kvm/x86.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 0f82e2cbf64c..daa1918031df 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -702,7 +702,8 @@ static void kvm_load_guest_xcr0(struct kvm_vcpu *vcpu) > if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) && > !vcpu->guest_xcr0_loaded) { > /* kvm_set_xcr() also depends on this */ > - xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0); > + if (vcpu->arch.xcr0 != host_xcr0) > + xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0); > vcpu->guest_xcr0_loaded = 1; > } > }
Reviewed-by: Quan Xu <quan.xu0@gmail.com>
| |