[10/15] KVM: arm64: vgic: Don't acquire the lpi_list_lock in vgic_put_irq()

Commit Message

Oliver Upton Jan. 24, 2024, 8:49 p.m. UTC

The LPI xarray's xa_lock is sufficient for synchronizing writers when
freeing a given LPI. Furthermore, readers can only take a new reference
on an IRQ if it was already nonzero.

Stop taking the lpi_list_lock unnecessarily and get rid of
__vgic_put_lpi_locked().

Signed-off-by: Oliver Upton <[e-mail]>
---
 arch/arm64/kvm/vgic/vgic-its.c |  4 ++--
 arch/arm64/kvm/vgic/vgic.c     | 21 ++++-----------------
 arch/arm64/kvm/vgic/vgic.h     |  1 -
 3 files changed, 6 insertions(+), 20 deletions(-)

Patch

diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index 7219f4a0a93d..8c026a530018 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -645,7 +645,7 @@  static void vgic_its_cache_translation(struct kvm *kvm, struct vgic_its *its,
 	 * was in the cache, and increment it on the new interrupt.
 	 */
 	if (cte->irq)
-		__vgic_put_lpi_locked(kvm, cte->irq);
+		vgic_put_irq(kvm, cte->irq);
 
 	/*
 	 * The irq refcount is guaranteed to be nonzero while holding the
@@ -682,7 +682,7 @@  void vgic_its_invalidate_cache(struct kvm *kvm)
 		if (!cte->irq)
 			break;
 
-		__vgic_put_lpi_locked(kvm, cte->irq);
+		vgic_put_irq(kvm, cte->irq);
 		cte->irq = NULL;
 	}
 
diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index 7e0d84906a12..6b8f440ca0fd 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -110,13 +110,13 @@  static void vgic_irq_release(struct kref *ref)
 {
 }
 
-/*
- * Drop the refcount on the LPI. Must be called with lpi_list_lock held.
- */
-void __vgic_put_lpi_locked(struct kvm *kvm, struct vgic_irq *irq)
+void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
 {
 	struct vgic_dist *dist = &kvm->arch.vgic;
 
+	if (irq->intid < VGIC_MIN_LPI)
+		return;
+
 	if (!kref_put(&irq->refcount, vgic_irq_release))
 		return;
 
@@ -126,19 +126,6 @@  void __vgic_put_lpi_locked(struct kvm *kvm, struct vgic_irq *irq)
 	kfree_rcu(irq, rcu);
 }
 
-void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
-{
-	struct vgic_dist *dist = &kvm->arch.vgic;
-	unsigned long flags;
-
-	if (irq->intid < VGIC_MIN_LPI)
-		return;
-
-	raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
-	__vgic_put_lpi_locked(kvm, irq);
-	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
-}
-
 void vgic_flush_pending_lpis(struct kvm_vcpu *vcpu)
 {
 	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
diff --git a/arch/arm64/kvm/vgic/vgic.h b/arch/arm64/kvm/vgic/vgic.h
index 20886f57416a..b0a2754eae93 100644
--- a/arch/arm64/kvm/vgic/vgic.h
+++ b/arch/arm64/kvm/vgic/vgic.h
@@ -180,7 +180,6 @@  vgic_get_mmio_region(struct kvm_vcpu *vcpu, struct vgic_io_device *iodev,
 		     gpa_t addr, int len);
 struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
 			      u32 intid);
-void __vgic_put_lpi_locked(struct kvm *kvm, struct vgic_irq *irq);
 void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq);
 bool vgic_get_phys_line_level(struct vgic_irq *irq);
 void vgic_irq_set_phys_pending(struct vgic_irq *irq, bool pending);