Re: [PATCH v4 09/15] KVM: SVM: Refresh AVIC configuration when changing APIC mode

From: Maxim Levitsky
Date: Mon May 09 2022 - 06:23:47 EST


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@xxxxxxx>
> ---
> 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@xxxxxxxxxx>


Best regards,
Maxim Levitsky