Re: [PATCH] KVM: x86: avoid unnecessary XSETBV on guest entry

2017-12-13 Thread Quan Xu 



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 
---
  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

Re: [PATCH] KVM: x86: avoid unnecessary XSETBV on guest entry

2017-12-13 Thread Wanpeng Li 
2017-12-13 20:51 GMT+08:00 Paolo Bonzini :
> xsetbv can be expensive when running on nested virtualization, try to
> avoid it.
>
> Signed-off-by: Paolo Bonzini 

Reviewed-by: Wanpeng Li 

> ---
>  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
>

Re: [PATCH] KVM: x86: avoid unnecessary XSETBV on guest entry

2017-12-13 Thread Jim Mattson 
Reviewed-by: Jim Mattson 

On Wed, Dec 13, 2017 at 4:51 AM, Paolo Bonzini  wrote:
> xsetbv can be expensive when running on nested virtualization, try to
> avoid it.
>
> Signed-off-by: Paolo Bonzini 
> ---
>  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
>

[PATCH] KVM: x86: avoid unnecessary XSETBV on guest entry

2017-12-13 Thread Paolo Bonzini 
xsetbv can be expensive when running on nested virtualization, try to
avoid it.

Signed-off-by: Paolo Bonzini 
---
 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