Re: [Qemu-devel] [PULL 18/33] vhost-user-scsi: Introduce vhost-user-scsi host device

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jun 07, 2017 at 02:22:24PM -0400, Paolo Bonzini wrote:
> > > How, since there is no synchronization point between the vhost-user
> > > server on the source and the destination?
> > 
> > The idea is that the backend should both stop picking up new requests and
> > also quiesce outstanding requests upon a GET_VRING_BASE vhost message.
> 
> This could be documented,

It is documented AFAIK. Pls take a look at the spec documentation.

> but perhaps it's best to add a START_STOP
> feature and message to the vhost-user protocol?

We just never need to GET_VRING_BASE if ring keeps going -
makes no sense since base gets invalidated immediately.



> The feature then can be optional for vhost-user-net and mandatory for
> vhost-user-scsi.  When this is done we can remove .unmigratable.
> 
> Thanks,
> 
> Paolo

If vhost-user-scsi does not stop the ring after responding to
GET_VRING_BASE, it's just a bug that needs to be fixed.

> > > 
> > > Can you please send a version of your patch that uses .unmigratable?
> > 
> > Sure I can do that. We can work on the migration later on.
> > 
> > > 
> > > I'll send a v6 that momentarily drops vhost-scsi, but I intend to
> > > include it again in the next pull request.
> > 
> > Sounds good to me.
> > 
> > Felipe
> > 
> > > 
> > > Thanks,
> > > 
> > > Paolo
> > 
> >