Commit 05b9405f authored by Oliver Upton's avatar Oliver Upton Committed by Marc Zyngier
Browse files

KVM: arm64: Resolve vLPI by host IRQ in vgic_v4_unset_forwarding() 



The virtual mapping and "GSI" routing of a particular vLPI is subject to
change in response to the guest / userspace. This can be pretty annoying
to deal with when KVM needs to track the physical state that's managed
for vLPI direct injection.

Make vgic_v4_unset_forwarding() resilient by using the host IRQ to
resolve the vgic IRQ. Since this uses the LPI xarray directly, finding
the ITS by doorbell address + grabbing it's its_lock is no longer
necessary. Note that matching the right ITS / ITE is already handled in
vgic_v4_set_forwarding(), and unless there's a bug in KVM's VGIC ITS
emulation the virtual mapping that should remain stable for the lifetime
of the vLPI mapping.

Tested-by: default avatarSweet Tea Dorminy <sweettea-kernel@dorminy.me>
Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20250523194722.4066715-4-oliver.upton@linux.dev


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent fc4dafe8

arch/arm64/kvm/arm.c

+1 −2
Original line number Diff line number Diff line
@@ -2800,8 +2800,7 @@ void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons, 
	if (irq_entry->type != KVM_IRQ_ROUTING_MSI)

		return;



	kvm_vgic_v4_unset_forwarding(irqfd->kvm, prod->irq,

				     &irqfd->irq_entry);

	kvm_vgic_v4_unset_forwarding(irqfd->kvm, prod->irq);

}



void kvm_arch_irq_bypass_stop(struct irq_bypass_consumer *cons)

arch/arm64/kvm/vgic/vgic-v4.c

+25 −20
Original line number Diff line number Diff line
@@ -508,10 +508,27 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq, 
	return ret;

}



int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int virq,

				 struct kvm_kernel_irq_routing_entry *irq_entry)

static struct vgic_irq *__vgic_host_irq_get_vlpi(struct kvm *kvm, int host_irq)

{

	struct vgic_irq *irq;

	unsigned long idx;



	guard(rcu)();

	xa_for_each(&kvm->arch.vgic.lpi_xa, idx, irq) {

		if (!irq->hw || irq->host_irq != host_irq)

			continue;



		if (!vgic_try_get_irq_kref(irq))

			return NULL;



		return irq;

	}



	return NULL;

}



int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int host_irq)

{

	struct vgic_its *its;

	struct vgic_irq *irq;

	unsigned long flags;

	int ret = 0;
@@ -519,31 +536,19 @@ int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int virq, 
	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))

	irq = __vgic_host_irq_get_vlpi(kvm, host_irq);

	if (!irq)

		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;



	raw_spin_lock_irqsave(&irq->irq_lock, flags);

	WARN_ON(irq->hw && irq->host_irq != virq);

	WARN_ON(irq->hw && irq->host_irq != host_irq);

	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);

		ret = its_unmap_vlpi(host_irq);

	}



	raw_spin_unlock_irqrestore(&irq->irq_lock, flags);

out:

	mutex_unlock(&its->its_lock);

	vgic_put_irq(kvm, irq);

	return ret;

}

include/kvm/arm_vgic.h

+1 −2
Original line number Diff line number Diff line
@@ -434,8 +434,7 @@ struct kvm_kernel_irq_routing_entry; 
int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int irq,

			       struct kvm_kernel_irq_routing_entry *irq_entry);



int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int irq,

				 struct kvm_kernel_irq_routing_entry *irq_entry);

int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int host_irq);



int vgic_v4_load(struct kvm_vcpu *vcpu);

void vgic_v4_commit(struct kvm_vcpu *vcpu);