[libvirt-users] <qemu:commandline> domain XML tag is not working?

[Kashyap Chamarthy]

On Tue, Apr 21, 2015 at 09:54:57AM +0800, Chengyuan Li wrote:
> Hi Kashyap,
> 
> Here I want to test and see how much I/O performance could be improved
> by virtio-blk data plane feature.  Yes, this is a dirty way to enable
> it :-),

> You mentioned using newer libvirt, is there parameter similar
> "x-data-plane=on" in new version libvirt?

Sorry, I didn't mean there's a specific version with this attribute
turned 'on'. In fact, from my 'grep'ing in the source tree, it is not
the case. I merely mentioned it as there have been numerous fixes in
various areas over the year and if you're in a test environment, it's
preferabl to use the newest versions.

-- 
/kashyap

> On Mon, Apr 20, 2015 at 10:51 PM, Kashyap Chamarthy <kchamart at redhat.com>
> wrote:
> 
> > On Mon, Apr 20, 2015 at 10:37:13PM +0800, Chengyuan Li wrote:
> > > Hi,
> > >
> > > I tried to enable virtio-blk data plane feature for VMs in my openstack
> > > environment,  the hypervisor is ubuntu 14.04, libvirt 1.2.2
> >
> > [I haven't tested the virtio-blk data plane myself.]
> >
> > This libvirt version seems a little old (from March 2014), you might
> > want to move to a bit newer.
> >
> > > and QEMU 2.0.
> > > As nova doesn't support that parameter yet, I did belows
> > >
> > > 1. nova boot a VM with raw disk image.
> > > 2. nova stop the VM.
> > > 3. run "virsh edit <instance-id>" on the hyprvisor node, and adding below
> > > into instance xml just before </domain>.
> >
> > You're modifying the guest definition behind Nova's back, so you get to
> > keep all the pieces if something breaks. :-)
> >
> > > However, the <qemu:commandline> part is ignored and not saved after
> > closing
> > > virsh edit, seems that libvirt rejected these changes. Is there any XML
> > > syntax error here? Or libvirt doesn't support <qemu:commandline> tag?
> > >
> > > <qemu:commandline>
> > >     <qemu:arg value='-set'/>
> > >     <qemu:arg value='device.drive-virtio-disk0.x-data-plane=on'/>
> > > </qemu:commandline>
> >