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 <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 62e4cd9..a9d3fc6 100644 (file)
--- a/virt/kvm/eventfd.c
+++ b/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