From: Marc Zyngier <marc.zyngier@arm.com>
Date: Fri, 27 Oct 2017 15:28:49 +0100
Subject: KVM: arm/arm64: GICv4: Use the doorbell interrupt as an unblocking
 source
Patch-mainline: v4.15-rc1
Git-commit: df9ba95993b9d59e077aa4613f7a4edd20a4064c
References: bsc#1077761

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>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Acked-by: Alexander Graf <agraf@suse.de>
---
 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(+)

--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -381,4 +381,7 @@
 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 */
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -315,11 +315,13 @@
 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)
--- a/virt/kvm/arm/vgic/vgic-v4.c
+++ b/virt/kvm/arm/vgic/vgic-v4.c
@@ -233,3 +233,21 @@
 	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);
+	}
+}