On 10/08/2017 23:41, Michael S. Tsirkin wrote: >>> Then we probably should fail probe if vq size is too small. >> What does this mean? > > We must prevent driver from submitting s/g lists > vq size to device. What is the rationale for the limit? It makes no sense if indirect descriptors are available, especially because... > Either tell linux to avoid s/g lists that are too long, or > simply fail request if this happens, or refuse to attach driver to device. > > Later option would look something like this within probe: > > for (i = VIRTIO_SCSI_VQ_BASE; i < num_vqs; i++) > if (vqs[i]->num < MAX_SG_USED_BY_LINUX) > goto err; > > > I don't know what's MAX_SG_USED_BY_LINUX though. > ... both virtio-blk and virtio-scsi transmit their own value for the maximum sg list size (max_seg in virtio-scsi, seg_max in virtio-blk). Paolo
