Re: [Qemu-devel] virtio scsi host draft specification, v3

[Michael S. Tsirkin]

On Wed, Jun 29, 2011 at 10:23:26AM +0200, Paolo Bonzini wrote:
> On 06/12/2011 09:51 AM, Michael S. Tsirkin wrote:
> >>>
> >>>  If a device uses more than one queue it is the responsibility of the
> >>>  device to ensure strict request ordering.
> >Maybe I misunderstand - how can this be the responsibility of
> >the device if the device does not get the information about
> >the original ordering of the requests?
> >
> >For example, if the driver is crazy enough to put
> >all write requests on one queue and all barriers
> >on another one, how is the device supposed to ensure
> >ordering?
> 
> I agree here, in fact I misread Hannes's comment as "if a driver
> uses more than one queue it is responsibility of the driver to
> ensure strict request ordering".  If you send requests to different
> queues, you know that those requests are independent.  I don't think
> anything else is feasible in the virtio framework.
> 
> Paolo

Like this then?

  If a driver uses more than one queue it is the responsibility of the
  driver to ensure strict request ordering: the device does not
  supply any guarantees about the ordering of requests between different
  virtqueues.