> -----Original Message-----
> From: Stefan Hajnoczi [mailto:stefa...@gmail.com]
> Sent: Monday, December 11, 2017 10:33 PM
> To: Liu, Changpeng <changpeng....@intel.com>
> Cc: qemu-devel@nongnu.org; pbonz...@redhat.com; m...@redhat.com;
> marcandre.lur...@redhat.com; fel...@nutanix.com; Harris, James R
> <james.r.har...@intel.com>
> Subject: Re: [PATCH v6 4/4] contrib/vhost-user-blk: introduce a vhost-user-blk
> sample application
>
> > +static int vub_virtio_process_req(VubDev *vdev_blk,
> > + VuVirtq *vq)
> > +{
> > + VugDev *gdev = &vdev_blk->parent;
> > + VuDev *vu_dev = &gdev->parent;
> > + VuVirtqElement *elem;
> > + uint32_t type;
> > + unsigned in_num;
> > + unsigned out_num;
> > + VubReq *req;
> > +
> > + elem = vu_queue_pop(vu_dev, vq, sizeof(VuVirtqElement));
> > + if (!elem) {
> > + return -1;
> > + }
> > +
> > + /* refer to hw/block/virtio_blk.c */
> > + if (elem->out_num < 1 || elem->in_num < 1) {
> > + fprintf(stderr, "virtio-blk request missing headers\n");
> > + free(elem);
> > + return -1;
> > + }
> > +
> > + req = g_new0(VubReq, 1);
> > + req->vdev_blk = vdev_blk;
> > + req->vq = vq;
> > + req->elem = elem;
> > +
> > + in_num = elem->in_num;
> > + out_num = elem->out_num;
> > +
> > + /* don't support VIRTIO_F_ANY_LAYOUT and virtio 1.0 only */
> > + if (elem->out_sg[0].iov_len < sizeof(struct virtio_blk_outhdr)) {
> > + fprintf(stderr, "Invalid outhdr size\n");
> > + goto err;
> > + }
>
> QEMU has iov_discard_front() and iov_discard_back(). They make it
> pretty easy to support VIRTIO_F_ANY_LAYOUT. If you have time, please
> consider adding it to libvhost-user, but it's not a requirement for this
> patch series.
>
> > + req->out = (struct virtio_blk_outhdr *)elem->out_sg[0].iov_base;
> > + out_num--;
> > +
> > + if (elem->in_sg[in_num - 1].iov_len < sizeof(struct virtio_blk_inhdr))
> > {
> > + fprintf(stderr, "Invalid inhdr size\n");
> > + goto err;
> > + }
> > + req->in = (struct virtio_blk_inhdr *)elem->in_sg[in_num - 1].iov_base;
> > + in_num--;
> > +
> > + type = le32toh(req->out->type);
>
> Endianness is more complicated if you want to support both VIRTIO 1.0
> and Legacy (0.9.7). I guess it's okay to make libvhost-user code only
> support VIRTIO 1.0.
> > +static void vub_queue_set_started(VuDev *vu_dev, int idx, bool started)
> > +{
> > + VuVirtq *vq;
> > +
> > + assert(vu_dev);
> > +
> > + if ((idx < 0) || (idx >= VHOST_MAX_NR_VIRTQUEUE)) {
> > + fprintf(stderr, "VQ Index out of range: %d\n", idx);
> > + vub_panic_cb(vu_dev, NULL);
> > + return;
> > + }
>
> Is it necessary to check num_queues? The vhost-user master should not
> be able to enable idx >= num_queues.
Yes, this part of code can be removed.
