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

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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: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20250523194722.4066715-4-oliver.upton@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Oliver Upton 2025-05-23 12:47:20 -07:00 • committed by Marc Zyngier
parent fc4dafe87b
commit 05b9405f2f
3 changed files with 27 additions and 24 deletions
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3
arch/arm64/kvm/arm.c
View file

@ -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)

45
arch/arm64/kvm/vgic/vgic-v4.c
View file

@ -508,10 +508,27 @@ out_unlock_irq:
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;
}

3
include/kvm/arm_vgic.h
View file

@ -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);