linux-kernel - Re: [PATCH v2 06/11] KVM: SVM: add wrappers to enable/disable IRET interception

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Date:   Mon, 5 Dec 2022 21:11:21 +0530
From:   Santosh Shukla <santosh.shukla@....com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     Sandipan Das <sandipan.das@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        Jiaxi Chen <jiaxi.chen@...ux.intel.com>,
        Babu Moger <babu.moger@....com>, linux-kernel@...r.kernel.org,
        Jing Liu <jing2.liu@...el.com>,
        Wyes Karny <wyes.karny@....com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <seanjc@...gle.com>, santosh.shukla@....com
Subject: Re: [PATCH v2 06/11] KVM: SVM: add wrappers to enable/disable IRET
 interception

On 11/30/2022 1:07 AM, Maxim Levitsky wrote:
> SEV-ES guests don't use IRET interception for the detection of
> an end of a NMI.
> 
> Therefore it makes sense to create a wrapper to avoid repeating
> the check for the SEV-ES.
> 
> No functional change is intended.
> 
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---
>  arch/x86/kvm/svm/svm.c | 28 +++++++++++++++++++---------
>  1 file changed, 19 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 512b2aa21137e2..cfed6ab29c839a 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -2468,16 +2468,29 @@ static int task_switch_interception(struct kvm_vcpu *vcpu)
>  			       has_error_code, error_code);
>  }
>  
> +static void svm_disable_iret_interception(struct vcpu_svm *svm)
> +{
> +	if (!sev_es_guest(svm->vcpu.kvm))
> +		svm_clr_intercept(svm, INTERCEPT_IRET);
> +}
> +
> +static void svm_enable_iret_interception(struct vcpu_svm *svm)
> +{
> +	if (!sev_es_guest(svm->vcpu.kvm))
> +		svm_set_intercept(svm, INTERCEPT_IRET);
> +}
> +

nits:
s/_iret_interception / _iret_intercept
does that make sense?

Thanks,
Santosh

>  static int iret_interception(struct kvm_vcpu *vcpu)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  
>  	++vcpu->stat.nmi_window_exits;
>  	svm->awaiting_iret_completion = true;
> -	if (!sev_es_guest(vcpu->kvm)) {
> -		svm_clr_intercept(svm, INTERCEPT_IRET);
> +
> +	svm_disable_iret_interception(svm);
> +	if (!sev_es_guest(vcpu->kvm))
>  		svm->nmi_iret_rip = kvm_rip_read(vcpu);
> -	}
> +
>  	kvm_make_request(KVM_REQ_EVENT, vcpu);
>  	return 1;
>  }
> @@ -3470,8 +3483,7 @@ static void svm_inject_nmi(struct kvm_vcpu *vcpu)
>  		return;
>  
>  	svm->nmi_masked = true;
> -	if (!sev_es_guest(vcpu->kvm))
> -		svm_set_intercept(svm, INTERCEPT_IRET);
> +	svm_enable_iret_interception(svm);
>  	++vcpu->stat.nmi_injections;
>  }
>  
> @@ -3614,12 +3626,10 @@ static void svm_set_nmi_mask(struct kvm_vcpu *vcpu, bool masked)
>  
>  	if (masked) {
>  		svm->nmi_masked = true;
> -		if (!sev_es_guest(vcpu->kvm))
> -			svm_set_intercept(svm, INTERCEPT_IRET);
> +		svm_enable_iret_interception(svm);
>  	} else {
>  		svm->nmi_masked = false;
> -		if (!sev_es_guest(vcpu->kvm))
> -			svm_clr_intercept(svm, INTERCEPT_IRET);
> +		svm_disable_iret_interception(svm);
>  	}
>  }
>