Re: [PATCH RFC v8 02/11] vhost: use batched get_vq_desc version

[Jason Wang]

On 2020/6/23 äå3:00, Eugenio Perez Martin wrote:
> On Tue, Jun 23, 2020 at 4:51 AM Jason Wang <jasowang@xxxxxxxxxx> wrote:
> > On 2020/6/23 äå12:00, Michael S. Tsirkin wrote:
> > > On Wed, Jun 17, 2020 at 11:19:26AM +0800, Jason Wang wrote:
> > > > On 2020/6/11 äå7:34, Michael S. Tsirkin wrote:
> > > > >     static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
> > > > >     {
> > > > >      kfree(vq->descs);
> > > > > @@ -394,6 +400,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
> > > > >      for (i = 0; i < dev->nvqs; ++i) {
> > > > >              vq = dev->vqs[i];
> > > > >              vq->max_descs = dev->iov_limit;
> > > > > +           if (vhost_vq_num_batch_descs(vq) < 0) {
> > > > > +                   return -EINVAL;
> > > > > +           }
> > > > This check breaks vdpa which set iov_limit to zero. Consider iov_limit is
> > > > meaningless to vDPA, I wonder we can skip the test when device doesn't use
> > > > worker.
> > > >
> > > > Thanks
> > > It doesn't need iovecs at all, right?
> > >
> > > -- MST
> >
> > Yes, so we may choose to bypass the iovecs as well.
> >
> > Thanks
> I think that the kmalloc_array returns ZERO_SIZE_PTR for all of them
> in that case, so I didn't bother to skip the kmalloc_array parts.
> Would you prefer to skip them all and let them NULL? Or have I
> misunderstood what you mean?


I'm ok with either approach, but my understanding is that Michael wants 
to skip them all.

Thanks


> Thanks!