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Date: Tue, 1 Sep 2015 17:20:06 +0800
From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
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Subject: Re: [Qemu-devel] [snabb-devel] Re: [PATCH v6 1/2] vhost-user: add
 multi queue support
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: "snabb-devel@googlegroups.com" <snabb-devel@googlegroups.com>, "thibaut.collet@6wind.com" <thibaut.collet@6wind.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "n.nikolaev@virtualopensystems.com" <n.nikolaev@virtualopensystems.com>, "luke@snabb.co" <luke@snabb.co>, "Long,
	Thomas" <thomas.long@intel.com>, "Ouyang,
	Changchun" <changchun.ouyang@intel.com>

On Mon, Aug 31, 2015 at 02:30:06PM +0300, Michael S. Tsirkin wrote:
[snip..] 
> > Then how about the other case:
> > When startup the vhost backend, user specify 8 queues, like:
> > Vhost-user ...  -queues 8      # Y=8
> > When startup the guest, user specify 4 queues, like:
> > Qemu-kvm ... -queues 4      # X=4
> > 
> > Vhost backend CAN support the queues number as much as the guest/qemu requires,
> > And qemu don't want enable all of them(8 in the case), just part of them(only 4 from 8).
> > Will qemu exit or go forward(of course with 4 queues)? 
> 
> I think it must go forward since guest does not have to
> configure all queues anyway - and that's built in to virtio spec.
> 
> Note that # of queues in actual use in fact changes dynamically
> too, without restaring the device.

May I know how do you do that? I mean, is there a public interface, like
by some commands? Or, by sending vhost messages?

	--yliu