[PATCH v4 20/26] KVM: arm/arm64: GICv4: Use the doorbell interrupt as an unblocking source

Marc Zyngier
2017-10-06T15:34:19Z

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>
---
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 2c250ee37878..5ee69aec990a 100644
--- a/virt/kvm/arm/vgic/vgic-v4.c
+++ b/virt/kvm/arm/vgic/vgic-v4.c
@@ -235,3 +235,21 @@ 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);
+ }
+}
--
2.14.1