linux-kernel - Re: [PATCH 8/8] KVM: x86: SVM: remove vgif

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Date:   Wed, 30 Mar 2022 00:20:35 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Borislav Petkov <bp@...en8.de>, Joerg Roedel <joro@...tes.org>,
        Ingo Molnar <mingo@...hat.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 8/8] KVM: x86: SVM: remove vgif_enabled()

On Tue, Mar 22, 2022, Maxim Levitsky wrote:
> KVM always uses vgif when allowed, thus there is
> no need to query current vmcb for it

It'd be helpful to explicitly call out that KVM always takes V_GIF_ENABLE_MASK
from vmcs01, otherwise this looks like it does unintentend things when KVM is
runing vmcb02.

> Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---
>  arch/x86/kvm/svm/svm.c | 12 ++++++------
>  arch/x86/kvm/svm/svm.h | 12 ++++--------
>  2 files changed, 10 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index acf04cf4ed2a..70fc5897f5f2 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -172,7 +172,7 @@ static int vls = true;
>  module_param(vls, int, 0444);
>  
>  /* enable/disable Virtual GIF */
> -static int vgif = true;
> +int vgif = true;
>  module_param(vgif, int, 0444);

...

> @@ -453,14 +454,9 @@ static inline bool svm_is_intercept(struct vcpu_svm *svm, int bit)
>  	return vmcb_is_intercept(&svm->vmcb->control, bit);
>  }
>  
> -static inline bool vgif_enabled(struct vcpu_svm *svm)
> -{
> -	return !!(svm->vmcb->control.int_ctl & V_GIF_ENABLE_MASK);