[PATCH v3 52/59] KVM: arm/arm64: GICv4: Use the doorbell interrupt as an unblocking source

Marc Zyngier
2017-07-31T17:27:29Z

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.

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 | 32 +++++++++++++++++++++++++++++++-
3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 050f78d4fb42..7b1cc7ff5b42 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -375,4 +375,7 @@ 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 6803ea27c47d..5dbc8dc8fbf4 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 6af3cde6d7d4..50721c4e3da5 100644
--- a/virt/kvm/arm/vgic/vgic-v4.c
+++ b/virt/kvm/arm/vgic/vgic-v4.c
@@ -16,6 +16,7 @@
*/

#include <linux/interrupt.h>
+#include <linux/irq.h>
#include <linux/irqdomain.h>
#include <linux/kvm_host.h>

@@ -73,6 +74,14 @@ int vgic_v4_init(struct kvm *kvm)
kvm_for_each_vcpu(i, vcpu, kvm) {
int irq = dist->its_vm.vpes[i]->irq;

+ /*
+ * Don't automatically enable the doorbell, as we're
+ * flipping it back and forth when the vcpu gets
+ * blocked. Also disable the lazy disabling, as the
+ * doorbell could kick us out of the guest too
+ * early...
+ */
+ irq_set_status_flags(irq, IRQ_NOAUTOEN | IRQ_DISABLE_UNLAZY);
ret = request_irq(irq, vgic_v4_doorbell_handler,
0, "vcpu", vcpu);
if (ret) {
@@ -98,7 +107,10 @@ void vgic_v4_teardown(struct kvm *kvm)

for (i = 0; i < its_vm->nr_vpes; i++) {
struct kvm_vcpu *vcpu = kvm_get_vcpu(kvm, i);
- free_irq(its_vm->vpes[i]->irq, vcpu);
+ int irq = its_vm->vpes[i]->irq;
+
+ irq_clear_status_flags(irq, IRQ_NOAUTOEN | IRQ_DISABLE_UNLAZY);
+ free_irq(irq, vcpu);
}

its_free_vcpu_irqs(its_vm);
@@ -211,3 +223,21 @@ 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_is_v4_capable(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_is_v4_capable(vcpu->kvm)) {
+ int irq = vcpu->arch.vgic_cpu.vgic_v3.its_vpe.irq;
+ if (irq)
+ disable_irq(irq);
+ }
+}
--
2.11.0