> I recall our original code is virtio_wmb().
> Use store fence to ensure all updates to entries before updating the index.
> Why do we need virtio_rmb() here and add virtio_wmb after
> vq_update_avail_idx()?
Store fence is unnecessary, Intel CPU's are cache coherent, please read
the virtio Linux ring header file for explanation. A full fence WMB
is more expensive and causes CPU stall
> > vq->vq_ring.avail->idx = vq->vq_avail_idx;
> > }
> >
> > @@ -255,7 +264,7 @@ static inline void
> > virtqueue_notify(struct virtqueue *vq)
> > {
> > /*
> > - * Ensure updated avail->idx is visible to host. mb() necessary?
> > + * Ensure updated avail->idx is visible to host.
> > * For virtio on IA, the notificaiton is through io port operation
> > * which is a serialization instruction itself.
> > */
> > --
> > 1.8.4.2
>
