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KVM: x86: avoid unnecessary XSETBV on guest entry

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xsetbv can be expensive when running on nested virtualization, try to
avoid it.

Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Wanpeng Li <wanpeng.li@hotmail.com>
Reviewed-by: Quan Xu <quan.xu0@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Paolo Bonzini 2017-12-13 13:51:32 +01:00 committed by Radim Krčmář
parent efdab99281
commit 476b7adaa3
1 changed files with 2 additions and 1 deletions
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3
arch/x86/kvm/x86.c
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@ -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;
}
}