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

Oliver Upton
2024-01-24T20:49:42Z

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 <oliver.upton@linux.dev>
---
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(-)

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);
--
2.43.0.429.g432eaa2c6b-goog