linux-kernel - Re: [PATCH v2 1/3] KVM: SVM: Refactor AVIC hardware setup logic into helper function

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Date:   Fri, 03 Dec 2021 09:39:40 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org, x86@...nel.org
Cc:     pbonzini@...hat.com, joro@...tes.org, seanjc@...gle.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        peterz@...radead.org, hpa@...or.com, thomas.lendacky@....com,
        jon.grimm@....com
Subject: Re: [PATCH v2 1/3] KVM: SVM: Refactor AVIC hardware setup logic
 into helper function

On Thu, 2021-12-02 at 17:58 -0600, Suravee Suthikulpanit wrote:
> To prepare for upcoming AVIC changes. There is no functional change.
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>  arch/x86/kvm/svm/avic.c | 10 ++++++++++
>  arch/x86/kvm/svm/svm.c  |  8 +-------
>  arch/x86/kvm/svm/svm.h  |  1 +
>  3 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index 8052d92069e0..6aca1682f4b7 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -1011,3 +1011,13 @@ void svm_vcpu_unblocking(struct kvm_vcpu *vcpu)
>  		kvm_vcpu_update_apicv(vcpu);
>  	avic_set_running(vcpu, true);
>  }
> +
> +bool avic_hardware_setup(bool avic, bool npt)
> +{
> +	if (!avic || !npt || !boot_cpu_has(X86_FEATURE_AVIC))
> +		return false;
Nitpick: Why to pass these as local variables? npt_enabled for example is
used in many places directly.

> +
> +	pr_info("AVIC enabled\n");
> +	amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
> +	return true;
> +}
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 989685098b3e..d23bc7a7c48e 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -1031,13 +1031,7 @@ static __init int svm_hardware_setup(void)
>  			nrips = false;
>  	}
>  
> -	enable_apicv = avic = avic && npt_enabled && boot_cpu_has(X86_FEATURE_AVIC);
> -
> -	if (enable_apicv) {
> -		pr_info("AVIC enabled\n");
> -
> -		amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
> -	}
> +	enable_apicv = avic = avic_hardware_setup(avic, npt_enabled);
>  
>  	if (vls) {
>  		if (!npt_enabled ||
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 5d30db599e10..1d2d72e56dd1 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -515,6 +515,7 @@ static inline bool avic_vcpu_is_running(struct kvm_vcpu *vcpu)
>  	return (READ_ONCE(*entry) & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK);
>  }
>  
> +bool avic_hardware_setup(bool avic, bool npt);
>  int avic_ga_log_notifier(u32 ga_tag);
>  void avic_vm_destroy(struct kvm *kvm);
>  int avic_vm_init(struct kvm *kvm);

Best regards,
	Maxim Levitsky