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).


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