[libvirt] docs: Document the new hostdev and address type 'mdev'

[Erik Skultety]

On Mon, Feb 27, 2017 at 09:33:51AM +0100, Martin Polednik wrote:
> On 20/02/17 15:28 +0100, Erik Skultety wrote:
> > Signed-off-by: Erik Skultety <eskultet at redhat.com>
> > ---
> > docs/formatdomain.html.in | 48 +++++++++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 44 insertions(+), 4 deletions(-)
> > 
> > diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> > index b69bd4c..13cb767 100644
> > --- a/docs/formatdomain.html.in
> > +++ b/docs/formatdomain.html.in
> > @@ -3277,8 +3277,20 @@
> >         attributes: <code>iobase</code> and <code>irq</code>.
> >         <span class="since">Since 1.2.1</span>
> >       </dd>
> > +      <dt><code>mdev</code></dt>
> > +      <dd>Mediated devices' addresses have so far only one mandatory attribute
> > +        <code>uuid</code> (<span class="since">since 3.1.0</span>) which
> > +        uniquely identifies a mediated device under the syfs file system.
> > +      </dd>
> >     </dl>
> > 
> > +    <p>
> > +        Note: Due to nature of mediated devices, being only software devices
> > +        defining an allocation of resources on the physical parent device, the
> > +        address type <code>mdev</code> is supposed to be used to identify a
> > +        device on the host only, rather than identifying it in the guest.
> > +    </p>
> > +
> >     <h4><a name="elementsControllers">Controllers</a></h4>
> > 
> >     <p>
> > @@ -3774,6 +3786,19 @@
> >   </devices>
> >   ...</pre>
> > 
> > +    <p>or:</p>
> > +
> > +<pre>
> > +  ...
> > +  <devices>
> > +    <hostdev mode='subsystem' type='mdev' model='vfio-pci'>
> > +    <source>
> > +      <address type='mdev' uuid='c2177883-f1bb-47f0-914d-32a22e3a8804'>
> > +    </source>
> > +    </hostdev>
> > +  </devices>
> > +  ...</pre>
> 
> Can't really test it yet, but from the docs/code seems to be OK for
> oVirt.
> 

Actually you can, with kernel 4.10, I don't know how the distro-packaged
kernels are configured, so my honest guess just would be to try modprobe mtty
and see what happens. Anyway, you can build your own kernel and just make sure
the vfio mediated devices framework is either included or modularized and the
CONFIG_SAMPLE_VFIO_MDEV_MTTY sample driver is checked and you're good to go.

Erik