Re: [PATCH v5 20/26] KVM: arm/arm64: GICv4: Use the doorbell interrupt as an unblocking source

Auger Eric
2017-11-07T21:45:58Z

Hi,

On 27/10/2017 16:28, Marc Zyngier wrote:
> The doorbell interrupt is only useful if the vcpu is blocked on WFI.
> In all other cases, recieving a doorbell interrupt is just a waste
> of cycles.
>
> So let's only enable the doorbell if a vcpu is getting blocked,
> and disable it when it is unblocked. This is very similar to
> what we're doing for the background timer.
>
> Reviewed-by: Christoffer Dall <cdall@linaro.org>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
> include/kvm/arm_vgic.h | 3 +++
> virt/kvm/arm/arm.c | 2 ++
> virt/kvm/arm/vgic/vgic-v4.c | 18 ++++++++++++++++++
> 3 files changed, 23 insertions(+)
>
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index 2f750c770bf2..8c896540a72c 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -381,4 +381,7 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int irq,
> int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int irq,
> struct kvm_kernel_irq_routing_entry *irq_entry);
>
> +void kvm_vgic_v4_enable_doorbell(struct kvm_vcpu *vcpu);
> +void kvm_vgic_v4_disable_doorbell(struct kvm_vcpu *vcpu);
> +
> #endif /* __KVM_ARM_VGIC_H */
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index 8388c1cc23f6..092a4ec03e57 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -316,11 +316,13 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
> void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)
> {
> kvm_timer_schedule(vcpu);
> + kvm_vgic_v4_enable_doorbell(vcpu);
> }
>
> void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu)
> {
> kvm_timer_unschedule(vcpu);
> + kvm_vgic_v4_disable_doorbell(vcpu);
> }
>
> int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
> index ea898af1a7a9..1a2f2fcdfa67 100644
> --- a/virt/kvm/arm/vgic/vgic-v4.c
> +++ b/virt/kvm/arm/vgic/vgic-v4.c
> @@ -237,3 +237,21 @@ int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int virq,
> mutex_unlock(&its->its_lock);
> return ret;
> }
> +
> +void kvm_vgic_v4_enable_doorbell(struct kvm_vcpu *vcpu)
> +{
> + if (vgic_supports_direct_msis(vcpu->kvm)) {
> + int irq = vcpu->arch.vgic_cpu.vgic_v3.its_vpe.irq;
> + if (irq)
> + enable_irq(irq);
> + }
> +}
> +
> +void kvm_vgic_v4_disable_doorbell(struct kvm_vcpu *vcpu)
> +{
> + if (vgic_supports_direct_msis(vcpu->kvm)) {
> + int irq = vcpu->arch.vgic_cpu.vgic_v3.its_vpe.irq;
> + if (irq)
> + disable_irq(irq);
> + }
> +}
>