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SubjectRe: [PATCH v3 11/12] KVM: SVM: call avic_vcpu_load/avic_vcpu_put when enabling/disabling AVIC
Date
On 02/08/21 20:33, Maxim Levitsky wrote:
> @@ -651,6 +673,7 @@ void svm_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
> }
> vmcb_mark_dirty(vmcb, VMCB_AVIC);
>
> + __avic_set_running(vcpu, activated);
> svm_set_pi_irte_mode(vcpu, activated);
> }
>

I'd rather have calls to avic_vcpu_load/avic_vcpu_put directly inside
the "if (activated)", and leaving avic_set_running to its current
implementation. That way you don't need __avic_set_running (which is a
confusing name, because it does more than just setting the running bit).

> void kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu)
> {
> + bool activate;
> +
> if (!lapic_in_kernel(vcpu))
> return;
>
> mutex_lock(&vcpu->kvm->arch.apicv_update_lock);
>
> - vcpu->arch.apicv_active = kvm_apicv_activated(vcpu->kvm);
> + activate = kvm_apicv_activated(vcpu->kvm);
> + if (vcpu->arch.apicv_active == activate)
> + goto out;
> +
> + vcpu->arch.apicv_active = activate;
> kvm_apic_update_apicv(vcpu);
> static_call(kvm_x86_refresh_apicv_exec_ctrl)(vcpu);
>
> @@ -9257,6 +9263,7 @@ void kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu)
> if (!vcpu->arch.apicv_active)
> kvm_make_request(KVM_REQ_EVENT, vcpu);
>
> +out:
> mutex_unlock(&vcpu->kvm->arch.apicv_update_lock);
> }
> EXPORT_SYMBOL_GPL(kvm_vcpu_update_apicv);

Should this be a separate patch?

As an aside, we have

static inline bool kvm_vcpu_apicv_active(struct kvm_vcpu *vcpu)
{
return vcpu->arch.apic && vcpu->arch.apicv_active;
}

but really vcpu->arch.apicv_active should never be true if
vcpu->arch.apic is. So it should be possible to change this to "return
vcpu->arch.apicv_active" with a comment that the serialization between
apicv_inhibit_reasons and apicv_active happens via apicv_update_lock.

Thanks,
Paolo

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