Re: [Qemu-devel] [PATCH v10 7/7] vhost-user: add a new message to disable/enable a specific virt queue.

[Yuanhan Liu]

On Tue, Sep 22, 2015 at 08:06:58PM -0600, Eric Blake wrote:
> On 09/22/2015 08:05 PM, Yuanhan Liu wrote:
> 
> >>> + * VHOST_USER_SET_VRING_ENABLE
> >>> +
> >>> +      Id: 18
> >>> +      Equivalent ioctl: N/A
> >>> +      Master payload: vring state description
> >>> +
> >>> +      Signal slave to enable or disable corresponding vring.
> >>
> >> Does there need to be any QMP control to manually change a given queue,
> >> or is it all used under the hood with no need for management apps to
> >> care other than their initial request of max queues?
> > 
> > TBH, I don't know. As far as I know, there is only one queue pair will
> > be enabled by default, and it's user's job to enable (or disable) more
> > queue pairs, say, by ethtool:
> > 
> >     # ethtool -L eth0 combined <queue pair number>
> > 
> > Which ends up sending the VHOST_USER_SET_VRING_ENABLE to actually enable
> > (or disable) a specific queue pairs.
> 
> So if I'm understanding, it is ethtool, not qemu, that is used to turn
> on additional queues, and therefore we don't need a QMP command in qemu
> to control things.

I guess so, and that's what Michael told me before.

> > Does that answer your question?
> 
> I think so, but I'll let other reviewers more familiar with this area of
> code give a final say.

Michael?

        --yliu