[PATCH] SVM: do not intercept task switch with NPT

[PATCH] SVM: do not intercept task switch with NPT

[Joerg Roedel]

When KVM uses NPT there is no reason to intercept task switches. This patch
removes the intercept for it in that case.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
---
 arch/x86/kvm/svm.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ad27346..51defe6 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -590,6 +590,7 @@ static void init_vmcb(struct vcpu_svm *svm)
 	if (npt_enabled) {
 		/* Setup VMCB for Nested Paging */
 		control->nested_ctl = 1;
+		control->intercept &= ~(1ULL << INTERCEPT_TASK_SWITCH);
 		control->intercept_exceptions &= ~(1 << PF_VECTOR);
 		control->intercept_cr_read &= ~(INTERCEPT_CR0_MASK|
 						INTERCEPT_CR3_MASK);
-- 
1.5.3.7



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Re: [PATCH] SVM: do not intercept task switch with NPT

[Avi Kivity]

Joerg Roedel wrote:
> When KVM uses NPT there is no reason to intercept task switches. This patch
> removes the intercept for it in that case.
>   

Applied, thanks.  I didn't know task switch and npt were related under svm.

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Re: [PATCH] SVM: do not intercept task switch with NPT

[Joerg Roedel]

On Fri, Apr 11, 2008 at 03:36:57PM +0300, Avi Kivity wrote:
> Joerg Roedel wrote:
> >When KVM uses NPT there is no reason to intercept task switches. This patch
> >removes the intercept for it in that case.
> >  
> 
> Applied, thanks.  I didn't know task switch and npt were related under svm.

The only reason why task switch is intercepted is the cr3 switch it
involves. But with NPT we don't intercept cr3 switches anymore so we can
disable task switch intercept too.

Joerg

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Re: [PATCH] SVM: do not intercept task switch with NPT

[Avi Kivity]

Joerg Roedel wrote:

 

>> Applied, thanks.  I didn't know task switch and npt were related under svm.
>>     
>
> The only reason why task switch is intercepted is the cr3 switch it
> involves. But with NPT we don't intercept cr3 switches anymore so we can
> disable task switch intercept too.
>   

Ah!  Of course.  Thanks.

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