2017-12-13 20:51 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>:
> xsetbv can be expensive when running on nested virtualization, try to
> avoid it.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Reviewed-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---
> 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;
> }
> }
> --
> 1.8.3.1
>
