Commit 3a08a6ca authored by Oliver Upton's avatar Oliver Upton
Browse files

KVM: arm64: vgic-v3: Use bare refcount for VGIC LPIs 



KVM's use of krefs to manage LPIs isn't adding much, especially
considering vgic_irq_release() is a noop due to the lack of sufficient
context.

Switch to using a regular refcount in anticipation of adding a
meaningful release concept for LPIs.

Reviewed-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250905100531.282980-3-oliver.upton@linux.dev


Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent 7d6ca84a

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

+1 −1
Original line number Diff line number Diff line
@@ -69,7 +69,7 @@ static int iter_mark_lpis(struct kvm *kvm) 
	int nr_lpis = 0;



	xa_for_each(&dist->lpi_xa, intid, irq) {

		if (!vgic_try_get_irq_kref(irq))

		if (!vgic_try_get_irq_ref(irq))

			continue;



		xa_set_mark(&dist->lpi_xa, intid, LPI_XA_MARK_DEBUG_ITER);

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

+2 −2
Original line number Diff line number Diff line
@@ -208,7 +208,7 @@ static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis) 
		raw_spin_lock_init(&irq->irq_lock);

		irq->vcpu = NULL;

		irq->target_vcpu = vcpu0;

		kref_init(&irq->refcount);

		refcount_set(&irq->refcount, 0);

		switch (dist->vgic_model) {

		case KVM_DEV_TYPE_ARM_VGIC_V2:

			irq->targets = 0;
@@ -277,7 +277,7 @@ static int vgic_allocate_private_irqs_locked(struct kvm_vcpu *vcpu, u32 type) 
		irq->intid = i;

		irq->vcpu = NULL;

		irq->target_vcpu = vcpu;

		kref_init(&irq->refcount);

		refcount_set(&irq->refcount, 0);

		if (vgic_irq_is_sgi(i)) {

			/* SGIs */

			irq->enabled = 1;

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

+4 −4
Original line number Diff line number Diff line
@@ -99,7 +99,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid, 
	raw_spin_lock_init(&irq->irq_lock);



	irq->config = VGIC_CONFIG_EDGE;

	kref_init(&irq->refcount);

	refcount_set(&irq->refcount, 1);

	irq->intid = intid;

	irq->target_vcpu = vcpu;

	irq->group = 1;
@@ -111,7 +111,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid, 
	 * check that we don't add a second list entry with the same LPI.

	 */

	oldirq = xa_load(&dist->lpi_xa, intid);

	if (vgic_try_get_irq_kref(oldirq)) {

	if (vgic_try_get_irq_ref(oldirq)) {

		/* Someone was faster with adding this LPI, lets use that. */

		kfree(irq);

		irq = oldirq;
@@ -547,7 +547,7 @@ static struct vgic_irq *vgic_its_check_cache(struct kvm *kvm, phys_addr_t db, 
	rcu_read_lock();



	irq = xa_load(&its->translation_cache, cache_key);

	if (!vgic_try_get_irq_kref(irq))

	if (!vgic_try_get_irq_ref(irq))

		irq = NULL;



	rcu_read_unlock();
@@ -571,7 +571,7 @@ static void vgic_its_cache_translation(struct kvm *kvm, struct vgic_its *its, 
	 * its_lock, as the ITE (and the reference it holds) cannot be freed.

	 */

	lockdep_assert_held(&its->its_lock);

	vgic_get_irq_kref(irq);

	vgic_get_irq_ref(irq);



	old = xa_store(&its->translation_cache, cache_key, irq, GFP_KERNEL_ACCOUNT);

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

+1 −1
Original line number Diff line number Diff line
@@ -518,7 +518,7 @@ static struct vgic_irq *__vgic_host_irq_get_vlpi(struct kvm *kvm, int host_irq) 
		if (!irq->hw || irq->host_irq != host_irq)

			continue;



		if (!vgic_try_get_irq_kref(irq))

		if (!vgic_try_get_irq_ref(irq))

			return NULL;



		return irq;

arch/arm64/kvm/vgic/vgic.c

+4 −13
Original line number Diff line number Diff line
@@ -71,7 +71,7 @@ static struct vgic_irq *vgic_get_lpi(struct kvm *kvm, u32 intid) 
	rcu_read_lock();



	irq = xa_load(&dist->lpi_xa, intid);

	if (!vgic_try_get_irq_kref(irq))

	if (!vgic_try_get_irq_ref(irq))

		irq = NULL;



	rcu_read_unlock();
@@ -114,15 +114,6 @@ struct vgic_irq *vgic_get_vcpu_irq(struct kvm_vcpu *vcpu, u32 intid) 
	return vgic_get_irq(vcpu->kvm, intid);

}



/*

 * We can't do anything in here, because we lack the kvm pointer to

 * lock and remove the item from the lpi_list. So we keep this function

 * empty and use the return value of kref_put() to trigger the freeing.

 */

static void vgic_irq_release(struct kref *ref)

{

}



void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)

{

	struct vgic_dist *dist = &kvm->arch.vgic;
@@ -131,7 +122,7 @@ void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq) 
	if (irq->intid < VGIC_MIN_LPI)

		return;



	if (!kref_put(&irq->refcount, vgic_irq_release))

	if (!refcount_dec_and_test(&irq->refcount))

		return;



	xa_lock_irqsave(&dist->lpi_xa, flags);
@@ -399,7 +390,7 @@ bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq, 
	 * now in the ap_list. This is safe as the caller must already hold a

	 * reference on the irq.

	 */

	vgic_get_irq_kref(irq);

	vgic_get_irq_ref(irq);

	list_add_tail(&irq->ap_list, &vcpu->arch.vgic_cpu.ap_list_head);

	irq->vcpu = vcpu;
@@ -657,7 +648,7 @@ static void vgic_prune_ap_list(struct kvm_vcpu *vcpu) 


			/*

			 * This vgic_put_irq call matches the

			 * vgic_get_irq_kref in vgic_queue_irq_unlock,

			 * vgic_get_irq_ref in vgic_queue_irq_unlock,

			 * where we added the LPI to the ap_list. As

			 * we remove the irq from the list, we drop

			 * also drop the refcount.