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KVM: arm64: vgic: Rely on RCU protection in vgic_get_lpi()

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Stop acquiring the lpi_list_lock in favor of RCU for protecting
the read-side critical section in vgic_get_lpi(). In order for this to
be safe, we also need to be careful not to take a reference on an irq
with a refcount of 0, as it is about to be freed.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240221054253.3848076-9-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Oliver Upton 2024-02-21 05:42:51 +00:00
parent a5c7f011cb
commit 864d4304ec
2 changed files with 16 additions and 9 deletions
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9
arch/arm64/kvm/vgic/vgic.c
View File

@ -63,15 +63,14 @@ static struct vgic_irq *vgic_get_lpi(struct kvm *kvm, u32 intid)
{
struct vgic_dist *dist = &kvm->arch.vgic;
struct vgic_irq *irq = NULL;
unsigned long flags;
raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
rcu_read_lock();
irq = xa_load(&dist->lpi_xa, intid);
if (irq)
vgic_get_irq_kref(irq);
if (!vgic_try_get_irq_kref(irq))
irq = NULL;
raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
rcu_read_unlock();
return irq;
}

16
arch/arm64/kvm/vgic/vgic.h
View File

@ -220,12 +220,20 @@ void vgic_v2_vmcr_sync(struct kvm_vcpu *vcpu);
void vgic_v2_save_state(struct kvm_vcpu *vcpu);
void vgic_v2_restore_state(struct kvm_vcpu *vcpu);
static inline bool vgic_try_get_irq_kref(struct vgic_irq *irq)
{
if (!irq)
return false;
if (irq->intid < VGIC_MIN_LPI)
return true;
return kref_get_unless_zero(&irq->refcount);
}
static inline void vgic_get_irq_kref(struct vgic_irq *irq)
{
if (irq->intid < VGIC_MIN_LPI)
return;
kref_get(&irq->refcount);
WARN_ON_ONCE(!vgic_try_get_irq_kref(irq));
}
void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu);