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Message-ID: <916f8d9c18d264d120d4ed7101583f4f22f66622.camel@redhat.com>
Subject: Re: [PATCH v4 09/15] KVM: SVM: Refresh AVIC configuration when
 changing APIC mode
From:   Maxim Levitsky <mlevitsk@redhat.com>
To:     Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc:     pbonzini@redhat.com, seanjc@google.com, joro@8bytes.org,
        jon.grimm@amd.com, wei.huang2@amd.com, terry.bowman@amd.com
Date:   Mon, 09 May 2022 13:22:17 +0300
In-Reply-To: <20220508023930.12881-10-suravee.suthikulpanit@amd.com>
References: <20220508023930.12881-1-suravee.suthikulpanit@amd.com>
         <20220508023930.12881-10-suravee.suthikulpanit@amd.com>
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On Sat, 2022-05-07 at 21:39 -0500, Suravee Suthikulpanit wrote:
> AMD AVIC can support xAPIC and x2APIC virtualization,
> which requires changing x2APIC bit VMCB and MSR intercepton
> for x2APIC MSRs. Therefore, call avic_refresh_apicv_exec_ctrl()
> to refresh configuration accordingly.
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> ---
>  arch/x86/kvm/svm/avic.c | 12 ++++++++++++
>  arch/x86/kvm/svm/svm.c  |  1 +
>  2 files changed, 13 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index 16ce2d50efac..a82981722018 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -691,6 +691,18 @@ 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)
> +{
> +	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;
> +	}
> +	avic_refresh_apicv_exec_ctrl(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,

Looks good as well!

This code can also be removed in the future as optimization,a
and do everything in avic_refresh_apicv_exec_ctrl instead.
No need to do this now though.

I need to understand the APICv KVM's code better to understand if
this is worth it.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>


Best regards,
	Maxim Levitsky