KVM: arm64: vgic-its: Walk the LPI xarray in vgic_copy_lpi_list()

Start iterating the LPI xarray in anticipation of removing the LPI
linked-list.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240221054253.3848076-5-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Author: oupton

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

@@ -327,6 +327,8 @@ static int update_lpi_config(struct kvm *kvm, struct vgic_irq *irq,
 	return 0;
 }
 
+#define GIC_LPI_MAX_INTID	((1 << INTERRUPT_ID_BITS_ITS) - 1)
+
 /*
  * Create a snapshot of the current LPIs targeting @vcpu, so that we can
  * enumerate those LPIs without holding any lock.
@@ -335,6 +337,7 @@ static int update_lpi_config(struct kvm *kvm, struct vgic_irq *irq,
 int vgic_copy_lpi_list(struct kvm *kvm, struct kvm_vcpu *vcpu, u32 **intid_ptr)
 {
 	struct vgic_dist *dist = &kvm->arch.vgic;
+	XA_STATE(xas, &dist->lpi_xa, GIC_LPI_OFFSET);
 	struct vgic_irq *irq;
 	unsigned long flags;
 	u32 *intids;
@@ -353,14 +356,18 @@ int vgic_copy_lpi_list(struct kvm *kvm, struct kvm_vcpu *vcpu, u32 **intid_ptr)
 		return -ENOMEM;
 
 	raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
-	list_for_each_entry(irq, &dist->lpi_list_head, lpi_list) {
+	rcu_read_lock();
+
+	xas_for_each(&xas, irq, GIC_LPI_MAX_INTID) {
 		if (i == irq_count)
 			break;
 		/* We don't need to "get" the IRQ, as we hold the list lock. */
 		if (vcpu && irq->target_vcpu != vcpu)
 			continue;
 		intids[i++] = irq->intid;
 	}
+
+	rcu_read_unlock();
 	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
 
 	*intid_ptr = intids;