KVM: arm64: vgic-its: Get rid of vgic_copy_lpi_list()

The last user has been transitioned to walking the LPI xarray directly.
Cut the wart off, and get rid of the now unneeded lpi_count while doing
so.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240422200158.2606761-7-oliver.upton@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: oupton

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

@@ -86,11 +86,8 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
 	if (ret) {
 		xa_release(&dist->lpi_xa, intid);
 		kfree(irq);
-		goto out_unlock;
 	}
 
-	atomic_inc(&dist->lpi_count);
-
 out_unlock:
 	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
 
@@ -316,51 +313,6 @@ static int update_lpi_config(struct kvm *kvm, struct vgic_irq *irq,
 	return 0;
 }
 
-/*
- * Create a snapshot of the current LPIs targeting @vcpu, so that we can
- * enumerate those LPIs without holding any lock.
- * Returns their number and puts the kmalloc'ed array into intid_ptr.
- */
-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;
-	int irq_count, i = 0;
-
-	/*
-	 * There is an obvious race between allocating the array and LPIs
-	 * being mapped/unmapped. If we ended up here as a result of a
-	 * command, we're safe (locks are held, preventing another
-	 * command). If coming from another path (such as enabling LPIs),
-	 * we must be careful not to overrun the array.
-	 */
-	irq_count = atomic_read(&dist->lpi_count);
-	intids = kmalloc_array(irq_count, sizeof(intids[0]), GFP_KERNEL_ACCOUNT);
-	if (!intids)
-		return -ENOMEM;
-
-	raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
-	rcu_read_lock();
-
-	xas_for_each(&xas, irq, VGIC_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;
-	return i;
-}
-
 static int update_affinity(struct vgic_irq *irq, struct kvm_vcpu *vcpu)
 {
 	int ret = 0;

arch/arm64/kvm/vgic/vgic.c

@@ -126,7 +126,6 @@ void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
 	__xa_erase(&dist->lpi_xa, irq->intid);
 	xa_unlock_irqrestore(&dist->lpi_xa, flags);
 
-	atomic_dec(&dist->lpi_count);
 	kfree_rcu(irq, rcu);
 }
 

arch/arm64/kvm/vgic/vgic.h

@@ -331,7 +331,6 @@ static inline bool vgic_dist_overlap(struct kvm *kvm, gpa_t base, size_t size)
 }
 
 bool vgic_lpis_enabled(struct kvm_vcpu *vcpu);
-int vgic_copy_lpi_list(struct kvm *kvm, struct kvm_vcpu *vcpu, u32 **intid_ptr);
 int vgic_its_resolve_lpi(struct kvm *kvm, struct vgic_its *its,
 			 u32 devid, u32 eventid, struct vgic_irq **irq);
 struct vgic_its *vgic_msi_to_its(struct kvm *kvm, struct kvm_msi *msi);

include/kvm/arm_vgic.h

@@ -279,7 +279,6 @@ struct vgic_dist {
 
 #define LPI_XA_MARK_DEBUG_ITER	XA_MARK_0
 	struct xarray		lpi_xa;
-	atomic_t		lpi_count;
 
 	/* LPI translation cache */
 	struct list_head	lpi_translation_cache;