virt/kvm/arm/vgic/vgic-v4.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 2017 ARM Ltd.
  * Author: Marc Zyngier <marc.zyngier@arm.com>
  */

 #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"

 /*
  * How KVM uses GICv4 (insert rude comments here):
  *
  * The vgic-v4 layer acts as a bridge between several entities:
  * - The GICv4 ITS representation offered by the ITS driver
  * - VFIO, which is in charge of the PCI endpoint
  * - The virtual ITS, which is the only thing the guest sees
  *
  * The configuration of VLPIs is triggered by a callback from VFIO,
  * instructing KVM that a PCI device has been configured to deliver
  * MSIs to a vITS.
  *
  * kvm_vgic_v4_set_forwarding() is thus called with the routing entry,
  * and this is used to find the corresponding vITS data structures
  * (ITS instance, device, event and irq) using a process that is
  * extremely similar to the injection of an MSI.
  *
  * At this stage, we can link the guest's view of an LPI (uniquely
  * identified by the routing entry) and the host irq, using the GICv4
  * driver mapping operation. Should the mapping succeed, we've then
  * successfully upgraded the guest's LPI to a VLPI. We can then start
  * with updating GICv4's view of the property table and generating an
  * INValidation in order to kickstart the delivery of this VLPI to the
  * guest directly, without software intervention. Well, almost.
  *
  * When the PCI endpoint is deconfigured, this operation is reversed
  * with VFIO calling kvm_vgic_v4_unset_forwarding().
  *
  * Once the VLPI has been mapped, it needs to follow any change the
  * guest performs on its LPI through the vITS. For that, a number of
  * command handlers have hooks to communicate these changes to the HW:
  * - Any invalidation triggers a call to its_prop_update_vlpi()
  * - The INT command results in a irq_set_irqchip_state(), which
  *   generates an INT on the corresponding VLPI.
  * - The CLEAR command results in a irq_set_irqchip_state(), which
  *   generates an CLEAR on the corresponding VLPI.
  * - DISCARD translates into an unmap, similar to a call to
  *   kvm_vgic_v4_unset_forwarding().
  * - MOVI is translated by an update of the existing mapping, changing
  *   the target vcpu, resulting in a VMOVI being generated.
  * - MOVALL is translated by a string of mapping updates (similar to
  *   the handling of MOVI). MOVALL is horrible.
  *
  * Note that a DISCARD/MAPTI sequence emitted from the guest without
  * reprogramming the PCI endpoint after MAPTI does not result in a
  * VLPI being mapped, as there is no callback from VFIO (the guest
  * will get the interrupt via the normal SW injection). Fixing this is
  * not trivial, and requires some horrible messing with the VFIO
  * internals. Not fun. Don't do that.
  *
  * Then there is the scheduling. Each time a vcpu is about to run on a
  * physical CPU, KVM must tell the corresponding redistributor about
  * it. And if we've migrated our vcpu from one CPU to another, we must
  * tell the ITS (so that the messages reach the right redistributor).
  * This is done in two steps: first issue a irq_set_affinity() on the
  * irq corresponding to the vcpu, then call its_schedule_vpe(). You
  * must be in a non-preemptible context. On exit, another call to
  * its_schedule_vpe() tells the redistributor that we're done with the
  * vcpu.
  *
  * Finally, the doorbell handling: Each vcpu is allocated an interrupt
  * which will fire each time a VLPI is made pending whilst the vcpu is
  * not running. Each time the vcpu gets blocked, the doorbell
  * interrupt gets enabled. When the vcpu is unblocked (for whatever
  * reason), the doorbell interrupt is disabled.
  */

 #define DB_IRQ_FLAGS	(IRQ_NOAUTOEN | IRQ_DISABLE_UNLAZY | IRQ_NO_BALANCING)

 static irqreturn_t vgic_v4_doorbell_handler(int irq, void *info)
 {
 	struct kvm_vcpu *vcpu = info;

 	/* We got the message, no need to fire again */
 	if (!irqd_irq_disabled(&irq_to_desc(irq)->irq_data))
 		disable_irq_nosync(irq);

 	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
  *
  * We may be called each time a vITS is created, or when the
  * vgic is initialized. This relies on kvm->lock to be
  * held. In both cases, the number of vcpus should now be
  * fixed.
  */
 int vgic_v4_init(struct kvm *kvm)
 {
 	struct vgic_dist *dist = &kvm->arch.vgic;
 	struct kvm_vcpu *vcpu;
 	int i, nr_vcpus, ret;

 	if (!kvm_vgic_global_state.has_gicv4)
 		return 0; /* Nothing to see here... move along. */

 	if (dist->its_vm.vpes)
 		return 0;

 	nr_vcpus = atomic_read(&kvm->online_vcpus);

 	dist->its_vm.vpes = kcalloc(nr_vcpus, sizeof(*dist->its_vm.vpes),
 				    GFP_KERNEL);
 	if (!dist->its_vm.vpes)
 		return -ENOMEM;

 	dist->its_vm.nr_vpes = nr_vcpus;

 	kvm_for_each_vcpu(i, vcpu, kvm)
 		dist->its_vm.vpes[i] = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;

 	ret = its_alloc_vcpu_irqs(&dist->its_vm);
 	if (ret < 0) {
 		kvm_err("VPE IRQ allocation failure\n");
 		kfree(dist->its_vm.vpes);
 		dist->its_vm.nr_vpes = 0;
 		dist->its_vm.vpes = NULL;
 		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, DB_IRQ_FLAGS);
 		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;
 }

 /**
  * vgic_v4_teardown - Free the GICv4 data structures
  * @kvm:	Pointer to the VM being destroyed
  *
  * Relies on kvm->lock to be held.
  */
 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, DB_IRQ_FLAGS);
 		free_irq(irq, vcpu);
 	}

 	its_free_vcpu_irqs(its_vm);
 	kfree(its_vm->vpes);
 	its_vm->nr_vpes = 0;
 	its_vm->vpes = NULL;
 }

 int vgic_v4_put(struct kvm_vcpu *vcpu, bool need_db)
 {
 	struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
 	struct irq_desc *desc = irq_to_desc(vpe->irq);

 	if (!vgic_supports_direct_msis(vcpu->kvm) || !vpe->resident)
 		return 0;

 	/*
 	 * If blocking, a doorbell is required. Undo the nested
 	 * disable_irq() calls...
 	 */
 	while (need_db && irqd_irq_disabled(&desc->irq_data))
 		enable_irq(vpe->irq);

 	return its_schedule_vpe(vpe, false);
 }

 int vgic_v4_load(struct kvm_vcpu *vcpu)
 {
 	struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
 	int err;

 	if (!vgic_supports_direct_msis(vcpu->kvm) || vpe->resident)
 		return 0;

 	/*
 	 * Before making the VPE resident, make sure the redistributor
 	 * corresponding to our current CPU expects us here. See the
 	 * doc in drivers/irqchip/irq-gic-v4.c to understand how this
 	 * turns into a VMOVP command at the ITS level.
 	 */
 	err = irq_set_affinity(vpe->irq, cpumask_of(smp_processor_id()));
 	if (err)
 		return err;

 	/* Disabled the doorbell, as we're about to enter the guest */
 	disable_irq_nosync(vpe->irq);

 	err = its_schedule_vpe(vpe, true);
 	if (err)
 		return err;

 	/*
 	 * Now that the VPE is resident, let's get rid of a potential
 	 * doorbell interrupt that would still be pending.
 	 */
 	return irq_set_irqchip_state(vpe->irq, IRQCHIP_STATE_PENDING, false);
 }

 static struct vgic_its *vgic_get_its(struct kvm *kvm,
 				     struct kvm_kernel_irq_routing_entry *irq_entry)
 {
 	struct kvm_msi msi  = (struct kvm_msi) {
 		.address_lo	= irq_entry->msi.address_lo,
 		.address_hi	= irq_entry->msi.address_hi,
 		.data		= irq_entry->msi.data,
 		.flags		= irq_entry->msi.flags,
 		.devid		= irq_entry->msi.devid,
 	};

 	return vgic_msi_to_its(kvm, &msi);
 }

 int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,
 			       struct kvm_kernel_irq_routing_entry *irq_entry)
 {
 	struct vgic_its *its;
 	struct vgic_irq *irq;
 	struct its_vlpi_map map;
 	int ret;

 	if (!vgic_supports_direct_msis(kvm))
 		return 0;

 	/*
 	 * Get the ITS, and escape early on error (not a valid
 	 * doorbell for any of our vITSs).
 	 */
 	its = vgic_get_its(kvm, irq_entry);
 	if (IS_ERR(its))
 		return 0;

 	mutex_lock(&its->its_lock);

 	/* Perform the actual DevID/EventID -> LPI translation. */
 	ret = vgic_its_resolve_lpi(kvm, its, irq_entry->msi.devid,
 				   irq_entry->msi.data, &irq);
 	if (ret)
 		goto out;

 	/*
 	 * Emit the mapping request. If it fails, the ITS probably
 	 * isn't v4 compatible, so let's silently bail out. Holding
 	 * the ITS lock should ensure that nothing can modify the
 	 * target vcpu.
 	 */
 	map = (struct its_vlpi_map) {
 		.vm		= &kvm->arch.vgic.its_vm,
 		.vpe		= &irq->target_vcpu->arch.vgic_cpu.vgic_v3.its_vpe,
 		.vintid		= irq->intid,
 		.properties	= ((irq->priority & 0xfc) |
 				   (irq->enabled ? LPI_PROP_ENABLED : 0) |
 				   LPI_PROP_GROUP1),
 		.db_enabled	= true,
 	};

 	ret = its_map_vlpi(virq, &map);
 	if (ret)
 		goto out;

 	irq->hw		= true;
 	irq->host_irq	= virq;
 	atomic_inc(&map.vpe->vlpi_count);

 out:
 	mutex_unlock(&its->its_lock);
 	return ret;
 }

 int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int virq,
 				 struct kvm_kernel_irq_routing_entry *irq_entry)
 {
 	struct vgic_its *its;
 	struct vgic_irq *irq;
 	int ret;

 	if (!vgic_supports_direct_msis(kvm))
 		return 0;

 	/*
 	 * Get the ITS, and escape early on error (not a valid
 	 * doorbell for any of our vITSs).
 	 */
 	its = vgic_get_its(kvm, irq_entry);
 	if (IS_ERR(its))
 		return 0;

 	mutex_lock(&its->its_lock);

 	ret = vgic_its_resolve_lpi(kvm, its, irq_entry->msi.devid,
 				   irq_entry->msi.data, &irq);
 	if (ret)
 		goto out;

 	WARN_ON(!(irq->hw && irq->host_irq == virq));
 	if (irq->hw) {
 		atomic_dec(&irq->target_vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count);
 		irq->hw = false;
 		ret = its_unmap_vlpi(virq);
 	}

 out:
 	mutex_unlock(&its->its_lock);
 	return ret;
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (C) 2017 ARM Ltd.
	* Author: Marc Zyngier <marc.zyngier@arm.com>
	*/

	#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"

	/*
	* How KVM uses GICv4 (insert rude comments here):
	*
	* The vgic-v4 layer acts as a bridge between several entities:
	* - The GICv4 ITS representation offered by the ITS driver
	* - VFIO, which is in charge of the PCI endpoint
	* - The virtual ITS, which is the only thing the guest sees
	*
	* The configuration of VLPIs is triggered by a callback from VFIO,
	* instructing KVM that a PCI device has been configured to deliver
	* MSIs to a vITS.
	*
	* kvm_vgic_v4_set_forwarding() is thus called with the routing entry,
	* and this is used to find the corresponding vITS data structures
	* (ITS instance, device, event and irq) using a process that is
	* extremely similar to the injection of an MSI.
	*
	* At this stage, we can link the guest's view of an LPI (uniquely
	* identified by the routing entry) and the host irq, using the GICv4
	* driver mapping operation. Should the mapping succeed, we've then
	* successfully upgraded the guest's LPI to a VLPI. We can then start
	* with updating GICv4's view of the property table and generating an
	* INValidation in order to kickstart the delivery of this VLPI to the
	* guest directly, without software intervention. Well, almost.
	*
	* When the PCI endpoint is deconfigured, this operation is reversed
	* with VFIO calling kvm_vgic_v4_unset_forwarding().
	*
	* Once the VLPI has been mapped, it needs to follow any change the
	* guest performs on its LPI through the vITS. For that, a number of
	* command handlers have hooks to communicate these changes to the HW:
	* - Any invalidation triggers a call to its_prop_update_vlpi()
	* - The INT command results in a irq_set_irqchip_state(), which
	* generates an INT on the corresponding VLPI.
	* - The CLEAR command results in a irq_set_irqchip_state(), which
	* generates an CLEAR on the corresponding VLPI.
	* - DISCARD translates into an unmap, similar to a call to
	* kvm_vgic_v4_unset_forwarding().
	* - MOVI is translated by an update of the existing mapping, changing
	* the target vcpu, resulting in a VMOVI being generated.
	* - MOVALL is translated by a string of mapping updates (similar to
	* the handling of MOVI). MOVALL is horrible.
	*
	* Note that a DISCARD/MAPTI sequence emitted from the guest without
	* reprogramming the PCI endpoint after MAPTI does not result in a
	* VLPI being mapped, as there is no callback from VFIO (the guest
	* will get the interrupt via the normal SW injection). Fixing this is
	* not trivial, and requires some horrible messing with the VFIO
	* internals. Not fun. Don't do that.
	*
	* Then there is the scheduling. Each time a vcpu is about to run on a
	* physical CPU, KVM must tell the corresponding redistributor about
	* it. And if we've migrated our vcpu from one CPU to another, we must
	* tell the ITS (so that the messages reach the right redistributor).
	* This is done in two steps: first issue a irq_set_affinity() on the
	* irq corresponding to the vcpu, then call its_schedule_vpe(). You
	* must be in a non-preemptible context. On exit, another call to
	* its_schedule_vpe() tells the redistributor that we're done with the
	* vcpu.
	*
	* Finally, the doorbell handling: Each vcpu is allocated an interrupt
	* which will fire each time a VLPI is made pending whilst the vcpu is
	* not running. Each time the vcpu gets blocked, the doorbell
	* interrupt gets enabled. When the vcpu is unblocked (for whatever
	* reason), the doorbell interrupt is disabled.
	*/

	#define DB_IRQ_FLAGS (IRQ_NOAUTOEN \| IRQ_DISABLE_UNLAZY \| IRQ_NO_BALANCING)

	static irqreturn_t vgic_v4_doorbell_handler(int irq, void *info)
	{
	struct kvm_vcpu *vcpu = info;

	/* We got the message, no need to fire again */
	if (!irqd_irq_disabled(&irq_to_desc(irq)->irq_data))
	disable_irq_nosync(irq);

	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
	*
	* We may be called each time a vITS is created, or when the
	* vgic is initialized. This relies on kvm->lock to be
	* held. In both cases, the number of vcpus should now be
	* fixed.
	*/
	int vgic_v4_init(struct kvm *kvm)
	{
	struct vgic_dist *dist = &kvm->arch.vgic;
	struct kvm_vcpu *vcpu;
	int i, nr_vcpus, ret;

	if (!kvm_vgic_global_state.has_gicv4)
	return 0; /* Nothing to see here... move along. */

	if (dist->its_vm.vpes)
	return 0;

	nr_vcpus = atomic_read(&kvm->online_vcpus);

	dist->its_vm.vpes = kcalloc(nr_vcpus, sizeof(*dist->its_vm.vpes),
	GFP_KERNEL);
	if (!dist->its_vm.vpes)
	return -ENOMEM;

	dist->its_vm.nr_vpes = nr_vcpus;

	kvm_for_each_vcpu(i, vcpu, kvm)
	dist->its_vm.vpes[i] = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;

	ret = its_alloc_vcpu_irqs(&dist->its_vm);
	if (ret < 0) {
	kvm_err("VPE IRQ allocation failure\n");
	kfree(dist->its_vm.vpes);
	dist->its_vm.nr_vpes = 0;
	dist->its_vm.vpes = NULL;
	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, DB_IRQ_FLAGS);
	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;
	}

	/**
	* vgic_v4_teardown - Free the GICv4 data structures
	* @kvm: Pointer to the VM being destroyed
	*
	* Relies on kvm->lock to be held.
	*/
	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, DB_IRQ_FLAGS);
	free_irq(irq, vcpu);
	}

	its_free_vcpu_irqs(its_vm);
	kfree(its_vm->vpes);
	its_vm->nr_vpes = 0;
	its_vm->vpes = NULL;
	}

	int vgic_v4_put(struct kvm_vcpu *vcpu, bool need_db)
	{
	struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
	struct irq_desc *desc = irq_to_desc(vpe->irq);

	if (!vgic_supports_direct_msis(vcpu->kvm) \|\| !vpe->resident)
	return 0;

	/*
	* If blocking, a doorbell is required. Undo the nested
	* disable_irq() calls...
	*/
	while (need_db && irqd_irq_disabled(&desc->irq_data))
	enable_irq(vpe->irq);

	return its_schedule_vpe(vpe, false);
	}

	int vgic_v4_load(struct kvm_vcpu *vcpu)
	{
	struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
	int err;

	if (!vgic_supports_direct_msis(vcpu->kvm) \|\| vpe->resident)
	return 0;

	/*
	* Before making the VPE resident, make sure the redistributor
	* corresponding to our current CPU expects us here. See the
	* doc in drivers/irqchip/irq-gic-v4.c to understand how this
	* turns into a VMOVP command at the ITS level.
	*/
	err = irq_set_affinity(vpe->irq, cpumask_of(smp_processor_id()));
	if (err)
	return err;

	/* Disabled the doorbell, as we're about to enter the guest */
	disable_irq_nosync(vpe->irq);

	err = its_schedule_vpe(vpe, true);
	if (err)
	return err;

	/*
	* Now that the VPE is resident, let's get rid of a potential
	* doorbell interrupt that would still be pending.
	*/
	return irq_set_irqchip_state(vpe->irq, IRQCHIP_STATE_PENDING, false);
	}

	static struct vgic_its vgic_get_its(struct kvm kvm,
	struct kvm_kernel_irq_routing_entry *irq_entry)
	{
	struct kvm_msi msi = (struct kvm_msi) {
	.address_lo = irq_entry->msi.address_lo,
	.address_hi = irq_entry->msi.address_hi,
	.data = irq_entry->msi.data,
	.flags = irq_entry->msi.flags,
	.devid = irq_entry->msi.devid,
	};

	return vgic_msi_to_its(kvm, &msi);
	}

	int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,
	struct kvm_kernel_irq_routing_entry *irq_entry)
	{
	struct vgic_its *its;
	struct vgic_irq *irq;
	struct its_vlpi_map map;
	int ret;

	if (!vgic_supports_direct_msis(kvm))
	return 0;

	/*
	* Get the ITS, and escape early on error (not a valid
	* doorbell for any of our vITSs).
	*/
	its = vgic_get_its(kvm, irq_entry);
	if (IS_ERR(its))
	return 0;

	mutex_lock(&its->its_lock);

	/* Perform the actual DevID/EventID -> LPI translation. */
	ret = vgic_its_resolve_lpi(kvm, its, irq_entry->msi.devid,
	irq_entry->msi.data, &irq);
	if (ret)
	goto out;

	/*
	* Emit the mapping request. If it fails, the ITS probably
	* isn't v4 compatible, so let's silently bail out. Holding
	* the ITS lock should ensure that nothing can modify the
	* target vcpu.
	*/
	map = (struct its_vlpi_map) {
	.vm = &kvm->arch.vgic.its_vm,
	.vpe = &irq->target_vcpu->arch.vgic_cpu.vgic_v3.its_vpe,
	.vintid = irq->intid,
	.properties = ((irq->priority & 0xfc) \|
	(irq->enabled ? LPI_PROP_ENABLED : 0) \|
	LPI_PROP_GROUP1),
	.db_enabled = true,
	};

	ret = its_map_vlpi(virq, &map);
	if (ret)
	goto out;

	irq->hw = true;
	irq->host_irq = virq;
	atomic_inc(&map.vpe->vlpi_count);

	out:
	mutex_unlock(&its->its_lock);
	return ret;
	}

	int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int virq,
	struct kvm_kernel_irq_routing_entry *irq_entry)
	{
	struct vgic_its *its;
	struct vgic_irq *irq;
	int ret;

	if (!vgic_supports_direct_msis(kvm))
	return 0;

	/*
	* Get the ITS, and escape early on error (not a valid
	* doorbell for any of our vITSs).
	*/
	its = vgic_get_its(kvm, irq_entry);
	if (IS_ERR(its))
	return 0;

	mutex_lock(&its->its_lock);

	ret = vgic_its_resolve_lpi(kvm, its, irq_entry->msi.devid,
	irq_entry->msi.data, &irq);
	if (ret)
	goto out;

	WARN_ON(!(irq->hw && irq->host_irq == virq));
	if (irq->hw) {
	atomic_dec(&irq->target_vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count);
	irq->hw = false;
	ret = its_unmap_vlpi(virq);
	}

	out:
	mutex_unlock(&its->its_lock);
	return ret;
	}