Re: [virtio-dev] Re: [PATCH v3 5/7] vhost-user: VHOST_USER_SET_VHOST_PCI msg

[Wei Wang <wei.w.wang@intel.com>]

On 12/06/2017 12:00 AM, Stefan Hajnoczi wrote:
> On Tue, Dec 05, 2017 at 11:33:14AM +0800, Wei Wang wrote:
> > Add a new vhost-uer protocol msg, VHOST_USER_SET_VHOST_PCI. This msg is
> > used to signal the vhost-pci device to start/stop working.
> >
> > Signed-off-by: Wei Wang <wei.w.wang@intel.com>
> > ---
> >   hw/net/vhost_net.c                | 37 +++++++++++++++++++++++++++++++++++++
> >   hw/virtio/vhost-pci-slave.c       |  2 +-
> >   hw/virtio/vhost-user.c            | 17 +++++++++++++++++
> >   hw/virtio/vhost.c                 |  7 +++++++
> >   include/hw/virtio/vhost-backend.h |  2 ++
> >   include/hw/virtio/vhost-user.h    |  2 ++
> >   include/hw/virtio/vhost.h         |  2 ++
> >   include/net/vhost_net.h           |  2 ++
> >   8 files changed, 70 insertions(+), 1 deletion(-)
> New protocol messages must be documented in docs/interop/vhost-user.txt.

OK, I'll add it to the doc after the discussion.

> Why is a new message needed?  I'm not sure why it is specific to
> vhost-pci.

Yes, it might be useful for other vhost-user slave implementations. 
Probably we can name it "VHOST_USER_SET_SLAVE"?
The message is used to "link up" or "link down" the slave device. For 
example, when virtio-net leaves, it sends a "VHOST_USER_SET_SLAVE" msg 
to the salve to link down the slave device.
(a similar msg is VHOST_USER_SET_VRING_ENABLE, but that is for virtqueue 
enable/disable, not for a device level enable/disable)

Best,
Wei