[PATCH v2 12/19] KVM: arm64: vgic-its: Get rid of the lpi_list_lock

[Oliver Upton <oliver.upton@linux.dev>]

The last genuine use case for the lpi_list_lock was the global LPI
translation cache, which has been removed in favor of a per-ITS xarray.
Remove a layer from the locking puzzle by getting rid of it.

vgic_add_lpi() still has a critical section that needs to protect
against the insertion of other LPIs; change it to take the LPI xarray's
xa_lock to retain this property.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 arch/arm64/kvm/vgic/vgic-init.c |  1 -
 arch/arm64/kvm/vgic/vgic-its.c  | 17 ++++++-----------
 arch/arm64/kvm/vgic/vgic.c      |  5 ++---
 include/kvm/arm_vgic.h          |  3 ---
 4 files changed, 8 insertions(+), 18 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
index 6ee42f395253..aee6083d0da6 100644
--- a/arch/arm64/kvm/vgic/vgic-init.c
+++ b/arch/arm64/kvm/vgic/vgic-init.c
@@ -53,7 +53,6 @@ void kvm_vgic_early_init(struct kvm *kvm)
 {
 	struct vgic_dist *dist = &kvm->arch.vgic;
 
-	raw_spin_lock_init(&dist->lpi_list_lock);
 	xa_init_flags(&dist->lpi_xa, XA_FLAGS_LOCK_IRQ);
 }
 
diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index f0287414fa75..be364a8d14a6 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -69,7 +69,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
 	irq->target_vcpu = vcpu;
 	irq->group = 1;
 
-	raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
+	xa_lock_irqsave(&dist->lpi_xa, flags);
 
 	/*
 	 * There could be a race with another vgic_add_lpi(), so we need to
@@ -84,14 +84,14 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
 		goto out_unlock;
 	}
 
-	ret = xa_err(xa_store(&dist->lpi_xa, intid, irq, 0));
+	ret = xa_err(__xa_store(&dist->lpi_xa, intid, irq, 0));
 	if (ret) {
 		xa_release(&dist->lpi_xa, intid);
 		kfree(irq);
 	}
 
 out_unlock:
-	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
+	xa_unlock_irqrestore(&dist->lpi_xa, flags);
 
 	if (ret)
 		return ERR_PTR(ret);
@@ -543,11 +543,8 @@ static struct vgic_irq *__vgic_its_check_cache(struct kvm *kvm, phys_addr_t db,
 static struct vgic_irq *vgic_its_check_cache(struct kvm *kvm, phys_addr_t db,
 					     u32 devid, u32 eventid)
 {
-	struct vgic_dist *dist = &kvm->arch.vgic;
 	struct vgic_irq *irq;
-	unsigned long flags;
 
-	raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
 	rcu_read_lock();
 
 	irq = __vgic_its_check_cache(kvm, db, devid, eventid);
@@ -555,7 +552,6 @@ static struct vgic_irq *vgic_its_check_cache(struct kvm *kvm, phys_addr_t db,
 		irq = NULL;
 
 	rcu_read_unlock();
-	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
 
 	return irq;
 }
@@ -565,7 +561,6 @@ static void vgic_its_cache_translation(struct kvm *kvm, struct vgic_its *its,
 				       struct vgic_irq *irq)
 {
 	unsigned long cache_key = vgic_its_cache_key(devid, eventid);
-	struct vgic_dist *dist = &kvm->arch.vgic;
 	unsigned long flags;
 	phys_addr_t db;
 
@@ -576,7 +571,7 @@ static void vgic_its_cache_translation(struct kvm *kvm, struct vgic_its *its,
 	if (xa_reserve_irq(&its->translation_cache, cache_key, GFP_KERNEL_ACCOUNT))
 		return;
 
-	raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
+	xa_lock_irqsave(&its->translation_cache, flags);
 	rcu_read_lock();
 
 	/*
@@ -595,10 +590,10 @@ static void vgic_its_cache_translation(struct kvm *kvm, struct vgic_its *its,
 	lockdep_assert_held(&its->its_lock);
 	vgic_get_irq_kref(irq);
 
-	xa_store(&its->translation_cache, cache_key, irq, 0);
+	__xa_store(&its->translation_cache, cache_key, irq, 0);
 out:
 	rcu_read_unlock();
-	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
+	xa_unlock_irqrestore(&its->translation_cache, flags);
 }
 
 static void vgic_its_invalidate_cache(struct vgic_its *its)
diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index e3ee1bc1214a..d0c59b51a6b0 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -29,9 +29,8 @@ struct vgic_global kvm_vgic_global_state __ro_after_init = {
  *       its->cmd_lock (mutex)
  *         its->its_lock (mutex)
  *           vgic_cpu->ap_list_lock		must be taken with IRQs disabled
- *             kvm->lpi_list_lock		must be taken with IRQs disabled
- *               vgic_dist->lpi_xa.xa_lock	must be taken with IRQs disabled
- *                 vgic_irq->irq_lock		must be taken with IRQs disabled
+ *             vgic_dist->lpi_xa.xa_lock	must be taken with IRQs disabled
+ *               vgic_irq->irq_lock		must be taken with IRQs disabled
  *
  * As the ap_list_lock might be taken from the timer interrupt handler,
  * we have to disable IRQs before taking this lock and everything lower
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 276082db9ae6..493b1f1c6bf7 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -280,9 +280,6 @@ struct vgic_dist {
 	 */
 	u64			propbaser;
 
-	/* Protects the lpi_list. */
-	raw_spinlock_t		lpi_list_lock;
-
 #define LPI_XA_MARK_DEBUG_ITER	XA_MARK_0
 	struct xarray		lpi_xa;
 
-- 
2.44.0.769.g3c40516874-goog