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KVM: fix spurious interrupt with irqfd

kvm didn't clear irqfd counter on deassign, as a result we could get a
spurious interrupt when irqfd is assigned back. this leads to poor
performance and, in theory, guest crash.

Signed-off-by: Michael S. Tsirkin <>
Signed-off-by: Avi Kivity <>
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1 parent cb289d6 commit b6a114d27273c37cd0107b0f49af208168498f05 @mstsirkin mstsirkin committed with Marcelo Tosatti Jan 13, 2010
Showing with 2 additions and 1 deletion.
  1. +2 −1 virt/kvm/eventfd.c
3 virt/kvm/eventfd.c
@@ -72,12 +72,13 @@ static void
irqfd_shutdown(struct work_struct *work)
struct _irqfd *irqfd = container_of(work, struct _irqfd, shutdown);
+ u64 cnt;
* Synchronize with the wait-queue and unhook ourselves to prevent
* further events.
- remove_wait_queue(irqfd->wqh, &irqfd->wait);
+ eventfd_ctx_remove_wait_queue(irqfd->eventfd, &irqfd->wait, &cnt);
* We know no new events will be scheduled at this point, so block

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