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virtio: always use handle_aio_output if registered 

Commit ad07cd6 ("virtio-scsi: always use dataplane path if ioeventfd is
active", 2016-10-30) and 9ffe337 ("virtio-blk: always use dataplane
path if ioeventfd is active", 2016-10-30) broke the virtio 1.0
indirect access registers.

The indirect access registers bypass the ioeventfd, so that virtio-blk
and virtio-scsi now repeatedly try to initialize dataplane instead of
triggering the guest->host EventNotifier.  Detect the situation by
checking vq->handle_aio_output; if it is not NULL, trigger the
EventNotifier, which is how the device expects to get notifications
and in fact the only thread-safe manner to deliver them.

Fixes: ad07cd6
Fixes: 9ffe337
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
master
Paolo Bonzini 2017-02-28 14:21:32 +01:00 committed by Michael S. Tsirkin
parent a77690c41d
commit e49a661840
1 changed files with 12 additions and 1 deletions
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13
hw/virtio/virtio.c
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@ -1528,7 +1528,18 @@ static void virtio_queue_notify_vq(VirtQueue *vq)
void virtio_queue_notify(VirtIODevice *vdev, int n)
{
virtio_queue_notify_vq(&vdev->vq[n]);
VirtQueue *vq = &vdev->vq[n];
if (unlikely(!vq->vring.desc || vdev->broken)) {
return;
}
trace_virtio_queue_notify(vdev, vq - vdev->vq, vq);
if (vq->handle_aio_output) {
event_notifier_set(&vq->host_notifier);
} else if (vq->handle_output) {
vq->handle_output(vdev, vq);
}
}
uint16_t virtio_queue_vector(VirtIODevice *vdev, int n)