linux-kernel - Re: [PATCH 09/10] KVM: SVM: Make lazy FPU switching work with nested svm

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Message-ID: <4B7D4F62.3010903@redhat.com>
Date:	Thu, 18 Feb 2010 16:32:02 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/10] KVM: SVM: Make lazy FPU switching work with nested
 svm

On 02/18/2010 01:38 PM, Joerg Roedel wrote:
> TDB.
>
>    

...

> @@ -973,6 +973,7 @@ static void svm_decache_cr4_guest_bits(struct kvm_vcpu *vcpu)
>
>   static void update_cr0_intercept(struct vcpu_svm *svm)
>   {
> +	struct vmcb *vmcb = svm->vmcb;
>   	ulong gcr0 = svm->vcpu.arch.cr0;
>   	u64 *hcr0 =&svm->vmcb->save.cr0;
>
> @@ -984,11 +985,25 @@ static void update_cr0_intercept(struct vcpu_svm *svm)
>
>
>   	if (gcr0 == *hcr0&&  svm->vcpu.fpu_active) {
> -		svm->vmcb->control.intercept_cr_read&= ~INTERCEPT_CR0_MASK;
> -		svm->vmcb->control.intercept_cr_write&= ~INTERCEPT_CR0_MASK;
> +		vmcb->control.intercept_cr_read&= ~INTERCEPT_CR0_MASK;
> +		vmcb->control.intercept_cr_write&= ~INTERCEPT_CR0_MASK;
> +		if (is_nested(svm)) {
> +			struct vmcb *hsave = svm->nested.hsave;
> +
> +			hsave->control.intercept_cr_read&= ~INTERCEPT_CR0_MASK;
> +			hsave->control.intercept_cr_write&= ~INTERCEPT_CR0_MASK;
> +			vmcb->control.intercept_cr_read  |= svm->nested.intercept_cr_read;
> +			vmcb->control.intercept_cr_write |= svm->nested.intercept_cr_write;
>    

Why are the last two lines needed?

> +		}
>   	} else {
>   		svm->vmcb->control.intercept_cr_read |= INTERCEPT_CR0_MASK;
>   		svm->vmcb->control.intercept_cr_write |= INTERCEPT_CR0_MASK;
> +		if (is_nested(svm)) {
> +			struct vmcb *hsave = svm->nested.hsave;
> +
> +			hsave->control.intercept_cr_read |= INTERCEPT_CR0_MASK;
> +			hsave->control.intercept_cr_write |= INTERCEPT_CR0_MASK;
> +		}
>   	}
>   }
>    

Maybe it's better to call update_cr0_intercept() after a vmexit instead, 
to avoid this repetition, and since the if () may take a different 
branch for the nested guest and guest cr0.


-- 
error compiling committee.c: too many arguments to function

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