linux-kernel - Re: [PATCH 12/13] KVM: nSVM: emulate VMEXIT

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Date:   Thu, 17 Nov 2022 20:18:18 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sandipan Das <sandipan.das@....com>,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        Jing Liu <jing2.liu@...el.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Wyes Karny <wyes.karny@....com>,
        Borislav Petkov <bp@...en8.de>,
        Babu Moger <babu.moger@....com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Jim Mattson <jmattson@...gle.com>, x86@...nel.org,
        Santosh Shukla <santosh.shukla@....com>
Subject: Re: [PATCH 12/13] KVM: nSVM: emulate VMEXIT_INVALID case for nested
 VNMI

On Thu, Nov 17, 2022, Maxim Levitsky wrote:
> From: Santosh Shukla <santosh.shukla@....com>
> 
> If NMI virtualization enabled and NMI_INTERCEPT is unset then next vm
> entry will exit with #INVALID exit reason.
> 
> In order to emulate above (VMEXIT(#INVALID)) scenario for nested
> environment, extending check for V_NMI_ENABLE, NMI_INTERCEPT bit in func
> __nested_vmcb_check_controls.

This belongs in the previous patch, no?  I don't see how this isn't just a
natural part of supporting nested vNMI.

> Signed-off-by: Santosh Shukla <santosh.shukla@....com>
> Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---
>  arch/x86/kvm/svm/nested.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index c9fcdd691bb5a1..3ef7e1971a4709 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -275,6 +275,11 @@ static bool __nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
>  	if (CC(!nested_svm_check_tlb_ctl(vcpu, control->tlb_ctl)))
>  		return false;
>  
> +	if (CC((control->int_ctl & V_NMI_ENABLE) &&
> +		!vmcb12_is_intercept(control, INTERCEPT_NMI))) {

Alignment is off by one:

	if (CC((control->int_ctl & V_NMI_ENABLE) &&
	       !vmcb12_is_intercept(control, INTERCEPT_NMI))) {
		return false;
	}

> +		return false;
> +	}
> +
>  	return true;
>  }
>  
> -- 
> 2.34.3
>