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KVM: arm64: vgic: Don't acquire the lpi_list_lock in vgic_put_irq()

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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().

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240221054253.3848076-11-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Oliver Upton
2024-02-21 05:42:53 +00:00
parent 50ac89bb70
commit e27f2d561f
3 changed files with 11 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
arch/arm64/kvm/vgic/vgic-its.c
View File

@@ -649,7 +649,7 @@ 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
@@ -686,7 +686,7 @@ 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;
}

28
arch/arm64/kvm/vgic/vgic.c
View File

@@ -111,22 +111,6 @@ 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)
{
struct vgic_dist *dist = &kvm->arch.vgic;
if (!kref_put(&irq->refcount, vgic_irq_release))
return;
xa_erase(&dist->lpi_xa, irq->intid);
atomic_dec(&dist->lpi_count);
kfree_rcu(irq, rcu);
}
void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
{
struct vgic_dist *dist = &kvm->arch.vgic;
@@ -135,9 +119,15 @@ void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
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);
if (!kref_put(&irq->refcount, vgic_irq_release))
return;
xa_lock_irqsave(&dist->lpi_xa, flags);
__xa_erase(&dist->lpi_xa, irq->intid);
xa_unlock_irqrestore(&dist->lpi_xa, flags);
atomic_dec(&dist->lpi_count);
kfree_rcu(irq, rcu);
}
void vgic_flush_pending_lpis(struct kvm_vcpu *vcpu)

1
arch/arm64/kvm/vgic/vgic.h
View File

@@ -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);