On 11/08/2017 19:23, Michael S. Tsirkin wrote: > On Fri, Aug 11, 2017 at 04:09:26PM +0200, Paolo Bonzini wrote: >> 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? > > So the host knows what it needs to support. > >> 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). > > No other device has it, and it seemed like a good idea to > limit it generally at the time. > > we can fix the spec to relax the requirement for blk and scsi - > want to submit a proposal? Alternatively, add a generic field > for that. Yes, I can submit a proposal. blk and scsi are the ones that are most likely to have very long sg lists. When I was designing scsi I just copied that field from blk. :) Paolo
