linux-kernel - Re: [PATCH 08/12] kvm/svm: cache nested intercepts

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Date:	Wed, 29 Jul 2009 16:13:35 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	Alexander Graf <agraf@...e.de>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/12] kvm/svm: cache nested intercepts

On 07/29/2009 03:56 PM, Joerg Roedel wrote:
> Signed-off-by: Joerg Roedel<joerg.roedel@....com>
> ---
>   arch/x86/kvm/svm.c |   30 +++++++++++++++++++++++-------
>   1 files changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 31467b1..9192c9a 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -86,6 +86,15 @@ struct nested_state {
>
>   	/* gpa pointers to the real vectors */
>   	u64 vmcb_msrpm;
> +
> +	/* cache for intercepts of the guest */
> +	u16 intercept_cr_read;
> +	u16 intercept_cr_write;
> +	u16 intercept_dr_read;
> +	u16 intercept_dr_write;
> +	u32 intercept_exceptions;
> +	u64 intercept;
> +
>   };
>
>   struct vcpu_svm {
> @@ -1459,7 +1468,6 @@ static int nested_svm_exit_handled_real(struct vcpu_svm *svm,
>   					void *arg2,
>   					void *opaque)
>   {
> -	struct vmcb *nested_vmcb = (struct vmcb *)arg1;
>   	bool kvm_overrides = *(bool *)opaque;
>   	u32 exit_code = svm->vmcb->control.exit_code;
>
> @@ -1486,38 +1494,38 @@ static int nested_svm_exit_handled_real(struct vcpu_svm *svm,
>   	switch (exit_code) {
>   	case SVM_EXIT_READ_CR0 ... SVM_EXIT_READ_CR8: {
>   		u32 cr_bits = 1<<  (exit_code - SVM_EXIT_READ_CR0);
> -		if (nested_vmcb->control.intercept_cr_read&  cr_bits)
> +		if (svm->nested.intercept_cr_read&  cr_bits)
>   			return 1;
>   		break;
>   	}
>   	case SVM_EXIT_WRITE_CR0 ... SVM_EXIT_WRITE_CR8: {
>   		u32 cr_bits = 1<<  (exit_code - SVM_EXIT_WRITE_CR0);
> -		if (nested_vmcb->control.intercept_cr_write&  cr_bits)
> +		if (svm->nested.intercept_cr_write&  cr_bits)
>   			return 1;
>   		break;
>   	}
>   	case SVM_EXIT_READ_DR0 ... SVM_EXIT_READ_DR7: {
>   		u32 dr_bits = 1<<  (exit_code - SVM_EXIT_READ_DR0);
> -		if (nested_vmcb->control.intercept_dr_read&  dr_bits)
> +		if (svm->nested.intercept_dr_read&  dr_bits)
>   			return 1;
>   		break;
>   	}
>   	case SVM_EXIT_WRITE_DR0 ... SVM_EXIT_WRITE_DR7: {
>   		u32 dr_bits = 1<<  (exit_code - SVM_EXIT_WRITE_DR0);
> -		if (nested_vmcb->control.intercept_dr_write&  dr_bits)
> +		if (svm->nested.intercept_dr_write&  dr_bits)
>   			return 1;
>   		break;
>   	}
>   	case SVM_EXIT_EXCP_BASE ... SVM_EXIT_EXCP_BASE + 0x1f: {
>   		u32 excp_bits = 1<<  (exit_code - SVM_EXIT_EXCP_BASE);
> -		if (nested_vmcb->control.intercept_exceptions&  excp_bits)
> +		if (svm->nested.intercept_exceptions&  excp_bits)
>   			return 1;
>   		break;
>   	}
>   	default: {
>   		u64 exit_bits = 1ULL<<  (exit_code - SVM_EXIT_INTR);
>   		nsvm_printk("exit code: 0x%x\n", exit_code);
> -		if (nested_vmcb->control.intercept&  exit_bits)
> +		if (svm->nested.intercept&  exit_bits)
>   			return 1;
>   	}
>   	}
> @@ -1808,6 +1816,14 @@ static int nested_svm_vmrun(struct vcpu_svm *svm, void *arg1,
>
>   	svm->nested.vmcb_msrpm = nested_vmcb->control.msrpm_base_pa;
>
> +	/* cache intercepts */
> +	svm->nested.intercept_cr_read    = nested_vmcb->control.intercept_cr_read;
> +	svm->nested.intercept_cr_write   = nested_vmcb->control.intercept_cr_write;
> +	svm->nested.intercept_dr_read    = nested_vmcb->control.intercept_dr_read;
> +	svm->nested.intercept_dr_write   = nested_vmcb->control.intercept_dr_write;
> +	svm->nested.intercept_exceptions = nested_vmcb->control.intercept_exceptions;
> +	svm->nested.intercept            = nested_vmcb->control.intercept;
> +
>   	force_new_asid(&svm->vcpu);
>   	svm->vmcb->control.exit_int_info = nested_vmcb->control.exit_int_info;
>   	svm->vmcb->control.exit_int_info_err = nested_vmcb->control.exit_int_info_err;
>    

I don't see the benefit of this patch.  Accessing the cache is just as 
expensive as accessing the real vmcb.

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

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