linux-kernel - Re: [PATCH v3 08/14] KVM: SVM: Update AVIC settings when changing APIC mode

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Date:   Wed, 04 May 2022 15:19:30 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     pbonzini@...hat.com, seanjc@...gle.com, joro@...tes.org,
        jon.grimm@....com, wei.huang2@....com, terry.bowman@....com
Subject: Re: [PATCH v3 08/14] KVM: SVM: Update AVIC settings when changing
 APIC mode

On Wed, 2022-05-04 at 02:31 -0500, Suravee Suthikulpanit wrote:
> Update and refresh AVIC settings when guest APIC mode is updated
> (e.g. changing between disabled, xAPIC, or x2APIC).
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>  arch/x86/kvm/svm/avic.c | 16 ++++++++++++++++
>  arch/x86/kvm/svm/svm.c  |  1 +
>  2 files changed, 17 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index 3ebeea19b487..d185dd8ddf17 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -691,6 +691,22 @@ void avic_apicv_post_state_restore(struct kvm_vcpu *vcpu)
>  	avic_handle_ldr_update(vcpu);
>  }
>  
> +void avic_set_virtual_apic_mode(struct kvm_vcpu *vcpu)
> +{
> +	struct vcpu_svm *svm = to_svm(vcpu);
> +
> +	if (!lapic_in_kernel(vcpu) || (avic_mode == AVIC_MODE_NONE))
> +		return;
> +
> +	if (kvm_get_apic_mode(vcpu) == LAPIC_MODE_INVALID) {
> +		WARN_ONCE(true, "Invalid local APIC state (vcpu_id=%d)", vcpu->vcpu_id);
> +		return;
> +	}
> +
> +	kvm_vcpu_update_apicv(&svm->vcpu);

Why to have this call? I think that all that is needed is only to call the
avic_refresh_apicv_exec_ctrl.

Best regards,
	Maxim Levitsky


> +	avic_refresh_apicv_exec_ctrl(&svm->vcpu);
> +}
> +
>  static int avic_set_pi_irte_mode(struct kvm_vcpu *vcpu, bool activate)
>  {
>  	int ret = 0;
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 314628b6bff4..9066568fd19d 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4692,6 +4692,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
>  	.enable_nmi_window = svm_enable_nmi_window,
>  	.enable_irq_window = svm_enable_irq_window,
>  	.update_cr8_intercept = svm_update_cr8_intercept,
> +	.set_virtual_apic_mode = avic_set_virtual_apic_mode,
>  	.refresh_apicv_exec_ctrl = avic_refresh_apicv_exec_ctrl,
>  	.check_apicv_inhibit_reasons = avic_check_apicv_inhibit_reasons,
>  	.apicv_post_state_restore = avic_apicv_post_state_restore,