On Tue, Oct 28, 2014 at 02:13:02AM +0000, Bin Wu wrote: > The event idx in virtio is an effective way to reduce the number of > interrupts and exits of the guest. When the guest puts an request > into the virtio ring, it doesn't exit immediately to inform the > backend. Instead, the guest checks the "avail" event idx to determine > the notification. > > In virtqueue_pop, when a request is poped, the current avail event > idx should be set to the number of vq->last_avail_idx. > > Signed-off-by: Bin Wu <wu.wu...@huawei.com>
Does this fix some observable bug? Improve efficiency for some workload? > --- > hw/virtio/virtio.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index 2c236bf..013979a 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -469,7 +469,7 @@ int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem) > > i = head = virtqueue_get_head(vq, vq->last_avail_idx++); > if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) { > - vring_avail_event(vq, vring_avail_idx(vq)); > + vring_avail_event(vq, vq->last_avail_idx); > } > > if (vring_desc_flags(vdev, desc_pa, i) & VRING_DESC_F_INDIRECT) { > -- > 1.7.12.4