linux-kernel - Re: [PATCH v2 3/5] KVM: x86: Use common 'enable

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Message-ID: <YKQmG3rMpwSI3WrV@google.com>
Date:   Tue, 18 May 2021 20:39:55 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Kechen Lu <kechenl@...dia.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] KVM: x86: Use common 'enable_apicv' variable for
 both APICv and AVIC

On Tue, May 18, 2021, Vitaly Kuznetsov wrote:
> Unify VMX and SVM code by moving APICv/AVIC enablement tracking to common
> 'enable_apicv' variable. Note: unlike APICv, AVIC is disabled by default.
> 
> No functional change intended.
> 
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---

...

> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 8c3918a11826..0d6ec34d1e4b 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -185,6 +185,10 @@ module_param(vls, int, 0444);
>  static int vgif = true;
>  module_param(vgif, int, 0444);
>  
> +/* enable / disable AVIC */
> +static int avic;
> +module_param(avic, int, 0444);

We should opportunistically make avic a "bool".

> +
>  bool __read_mostly dump_invalid_vmcb;
>  module_param(dump_invalid_vmcb, bool, 0644);
>  
> @@ -1009,14 +1013,15 @@ static __init int svm_hardware_setup(void)
>  			nrips = false;
>  	}
>  
> -	if (avic) {
> -		if (!npt_enabled || !boot_cpu_has(X86_FEATURE_AVIC)) {
> -			avic = false;
> -		} else {
> -			pr_info("AVIC enabled\n");
> +	if (!npt_enabled || !boot_cpu_has(X86_FEATURE_AVIC))
> +		avic = false;
>  
> -			amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
> -		}
> +	/* 'enable_apicv' is common between VMX/SVM but the defaults differ */

-1 for not throwing Jim under the bus :-)

Nits aside,

Reviewed-by: Sean Christopherson <seanjc@...gle.com>