[PATCH 1/2] kvm: fix spurious interrupt with irqfd

From: Michael S. Tsirkin
Date: Wed Jan 13 2010 - 12:15:35 EST

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@xxxxxxxxxx>
virt/kvm/eventfd.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

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

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