[libvirt] Exposing qemu support for SDL via capabilities

Adam Litke agl at us.ibm.com
Fri Jul 8 15:56:07 UTC 2011

On 07/08/2011 10:14 AM, Richard W.M. Jones wrote:
> On Fri, Jul 08, 2011 at 09:19:46AM -0500, Adam Litke wrote:
>> Hi all,
>> In order to nicely support domains that use qemu's SDL support,
>> libvirt-cim is looking for a way to confirm if the underlying qemu
>> emulator can support SDL.  Libvirt already knows this information
>> internally.  It seems to me that the best way to provide this
>> information is by reporting it as a guest feature via the capabilities
>> API call.  I was thinking the node '/capabilities/guest/features/sdl'
>> could be added when qemu supports SDL.
>> Is this a good idea?
> Seems like clearly a good idea to me.  (Although I don't have
> to code it :-)

Don't worry :)  I think we have a motivated party.

> Would it be worth having a separate <graphics> element underneath
> features, so the path would be /capabilities/guest/features/graphics/sdl ?

I only think this would be needed if we are going to add other
graphics-related features.  Can you think of other features that would
fit?  I think libvirt always assumes some form of vnc support so there
may not be a need to enumerate graphics types.  We might want to
advertise spice support, but that wouldn't fit strictly under graphics
because spice affects much more than the graphics device.

Is there a desire to eventually add support for enumerating the
different models of devices that qemu can emulate?  For example,
[ne2k_pci, i82551, i82557b, i82559er, rtl8139, e1000, pcnet, virtio] for
network models?  If so, we may want to place this information in a more
structured hierarchy /capabilities/guest/devices/net/models/.  Either
way, SDL support isn't part of the device model so it would probably
make sense to place it directly under 'features' IMO.

Adam Litke
IBM Linux Technology Center

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