linux-kernel - Re: [PATCH] x86: svm: make wbinvd faster

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Message-ID: <20150309232846.GB12125@amt.cnet>
Date:	Mon, 9 Mar 2015 20:28:46 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Joel Schopp <joel.schopp@....com>
Cc:	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
	David Kaplan <David.Kaplan@....com>, rkrcmar@...hat.com,
	Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86: svm: make wbinvd faster

On Fri, Feb 27, 2015 at 06:19:18PM -0600, Joel Schopp wrote:
> From: David Kaplan <David.Kaplan@....com>
> No need to re-decode WBINVD since we know what it is from the intercept.
> 
> Signed-off-by: David Kaplan <David.Kaplan@....com>
> [extracted from larger unlrelated patch, forward ported, tested]
> Signed-off-by: Joel Schopp <joel.schopp@....com>

Can't you disable the intercept if need_emulate_wbinvd(vcpu) == false? 

> ---
>  arch/x86/kvm/svm.c |   10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index d319e0c..86ecd21 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2776,6 +2776,14 @@ static int skinit_interception(struct vcpu_svm *svm)
>  	return 1;
>  }
>  
> +static int wbinvd_interception(struct vcpu_svm *svm)
> +{
> +	kvm_emulate_wbinvd(&svm->vcpu);
> +	skip_emulated_instruction(&svm->vcpu);
> +	return 1;
> +}
> +
> +
>  static int xsetbv_interception(struct vcpu_svm *svm)
>  {
>  	u64 new_bv = kvm_read_edx_eax(&svm->vcpu);
> @@ -3376,7 +3384,7 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
>  	[SVM_EXIT_STGI]				= stgi_interception,
>  	[SVM_EXIT_CLGI]				= clgi_interception,
>  	[SVM_EXIT_SKINIT]			= skinit_interception,
> -	[SVM_EXIT_WBINVD]                       = emulate_on_interception,
> +	[SVM_EXIT_WBINVD]                       = wbinvd_interception,
>  	[SVM_EXIT_MONITOR]			= monitor_interception,
>  	[SVM_EXIT_MWAIT]			= mwait_interception,
>  	[SVM_EXIT_XSETBV]			= xsetbv_interception,
> 
> --
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