The commits 03de2f527 "virtio-blk: do not use vring in dataplane" and
9ffe337c08 "virtio-blk: always use dataplane path if ioeventfd is active"
changed how notifications are done for virtio-blk substantially. Due to a
race condition interrupts are lost when irqfd is torn down after
notify_guest_bh was scheduled but before it actually runs. Furthermore
virtio_notify_irqfd ignores the value returned by event_notifier_set
which correctly indicates that notification has failed due to bad file
descriptor.
Let's fix this by making virtio_notify_irqfd fall back to the non-irqfd
notification mechanism if event_notifier_set fails.
Signed-off-by: Halil Pasic <pa...@linux.vnet.ibm.com>
---
This is probably not the only way to fix this: suggestions welcome. I
did not use a fixes tag because I'm not sure yet where exactly things got
broken. Maybe guys more familiar with dataplane an coroutines can help
(Paolo, Stefan).
---
hw/virtio/virtio.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 23483c7..8e1c1e9 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1581,7 +1581,9 @@ void virtio_notify_irqfd(VirtIODevice *vdev, VirtQueue
*vq)
* to an atomic operation.
*/
virtio_set_isr(vq->vdev, 0x1);
- event_notifier_set(&vq->guest_notifier);
+ if (event_notifier_set(&vq->guest_notifier)) {
+ virtio_notify_vector(vdev, vq->vector);
+ }
}
static void virtio_irq(VirtQueue *vq)
--
2.8.4
