diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index 0e8b5277be3b..a369b20d47f0 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -157,21 +157,28 @@ irqfd_shutdown(struct work_struct *work) } -/* assumes kvm->irqfds.lock is held */ -static bool -irqfd_is_active(struct kvm_kernel_irqfd *irqfd) +static bool irqfd_is_active(struct kvm_kernel_irqfd *irqfd) { + /* + * Assert that either irqfds.lock or SRCU is held, as irqfds.lock must + * be held to prevent false positives (on the irqfd being active), and + * while false negatives are impossible as irqfds are never added back + * to the list once they're deactivated, the caller must at least hold + * SRCU to guard against routing changes if the irqfd is deactivated. + */ + lockdep_assert_once(lockdep_is_held(&irqfd->kvm->irqfds.lock) || + srcu_read_lock_held(&irqfd->kvm->irq_srcu)); + return list_empty(&irqfd->list) ? false : true; } /* * Mark the irqfd as inactive and schedule it for removal - * - * assumes kvm->irqfds.lock is held */ -static void -irqfd_deactivate(struct kvm_kernel_irqfd *irqfd) +static void irqfd_deactivate(struct kvm_kernel_irqfd *irqfd) { + lockdep_assert_held(&irqfd->kvm->irqfds.lock); + BUG_ON(!irqfd_is_active(irqfd)); list_del_init(&irqfd->list); @@ -217,8 +224,15 @@ irqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) seq = read_seqcount_begin(&irqfd->irq_entry_sc); irq = irqfd->irq_entry; } while (read_seqcount_retry(&irqfd->irq_entry_sc, seq)); - /* An event has been signaled, inject an interrupt */ - if (kvm_arch_set_irq_inatomic(&irq, kvm, + + /* + * An event has been signaled, inject an interrupt unless the + * irqfd is being deassigned (isn't active), in which case the + * routing information may be stale (once the irqfd is removed + * from the list, it will stop receiving routing updates). + */ + if (unlikely(!irqfd_is_active(irqfd)) || + kvm_arch_set_irq_inatomic(&irq, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1, false) == -EWOULDBLOCK) schedule_work(&irqfd->inject); @@ -585,18 +599,8 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args) spin_lock_irq(&kvm->irqfds.lock); list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) { - if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi) { - /* - * This clearing of irq_entry.type is needed for when - * another thread calls kvm_irq_routing_update before - * we flush workqueue below (we synchronize with - * kvm_irq_routing_update using irqfds.lock). - */ - write_seqcount_begin(&irqfd->irq_entry_sc); - irqfd->irq_entry.type = 0; - write_seqcount_end(&irqfd->irq_entry_sc); + if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi) irqfd_deactivate(irqfd); - } } spin_unlock_irq(&kvm->irqfds.lock);