KVM: arm/arm64: GICv4: Add doorbell interrupt handling

When a vPE is not running, a VLPI being made pending results in a
doorbell interrupt being delivered. Let's handle this interrupt
and update the pending_last flag that indicates that VLPIs are
pending. The corresponding vcpu is also kicked into action.

Special care is taken to prevent the doorbell from being enabled
at request time (this is controlled separately), and to make
the disabling on the interrupt non-lazy.

Reviewed-by: Christoffer Dall <christoffer.dall@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>

virt/kvm/arm/vgic/vgic-v4.c

@@ -16,12 +16,24 @@
  */
 
 #include <linux/interrupt.h>
+#include <linux/irq.h>
 #include <linux/irqdomain.h>
 #include <linux/kvm_host.h>
 #include <linux/irqchip/arm-gic-v3.h>
 
 #include "vgic.h"
 
+static irqreturn_t vgic_v4_doorbell_handler(int irq, void *info)
+{
+	struct kvm_vcpu *vcpu = info;
+
+	vcpu->arch.vgic_cpu.vgic_v3.its_vpe.pending_last = true;
+	kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
+	kvm_vcpu_kick(vcpu);
+
+	return IRQ_HANDLED;
+}
+
 /**
  * vgic_v4_init - Initialize the GICv4 data structures
  * @kvm:	Pointer to the VM being initialized
@@ -61,6 +73,33 @@ int vgic_v4_init(struct kvm *kvm)
 		return ret;
 	}
 
+	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) {
+			kvm_err("failed to allocate vcpu IRQ%d\n", irq);
+			/*
+			 * Trick: adjust the number of vpes so we know
+			 * how many to nuke on teardown...
+			 */
+			dist->its_vm.nr_vpes = i;
+			break;
+		}
+	}
+
+	if (ret)
+		vgic_v4_teardown(kvm);
+
 	return ret;
 }
 
@@ -73,10 +112,19 @@ int vgic_v4_init(struct kvm *kvm)
 void vgic_v4_teardown(struct kvm *kvm)
 {
 	struct its_vm *its_vm = &kvm->arch.vgic.its_vm;
+	int i;
 
 	if (!its_vm->vpes)
 		return;
 
+	for (i = 0; i < its_vm->nr_vpes; i++) {
+		struct kvm_vcpu *vcpu = kvm_get_vcpu(kvm, i);
+		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);
 	kfree(its_vm->vpes);
 	its_vm->nr_vpes = 0;