[libvirt] [PATCH] allow memballoon type of none to desactivate it

[Daniel Veillard]

On Mon, Aug 09, 2010 at 06:53:34PM +0100, Daniel P. Berrange wrote:
> On Mon, Aug 09, 2010 at 06:38:27PM +0200, Daniel Veillard wrote:
> >   The balloon device is automatically added to qemu guests if supported,
> > but it may be useful to desactivate it. The simplest to not change the
> > existing behaviour is to allow
> >   <memballoon type="none"/>
> > as an extra option to desactivate it (it is automatically added if the
> > memballoon construct is missing for the domain).
> > The following simple patch just adds the extra option and does not
> > change the default behaviour but avoid creating a balloon device if
> > type="none" is used.
>  
> I really don't like the idea of 'type=none' devices in general.

Since we automagically add the devices to describe an internal policy
I think we're at fault here.

> I don't	think we should	have an	element	insides <devices> that
> doesn't	actually represent a device.
> 
> If we want to disable the balloon, then	I think	we should aim
> for an element or attribute elsewhere to toggle it.
> 
> eg, perhaps the	earlier <memory> element can indicate whether it
> supports ballooning. eg
> 
>   <memory ballonable='yes|no'>2423423432</memory>
> 
> Thus if	ballooning is not enabled, the <memballoon> device would
> never need to appear within <devices>

  Grumpf ... that mean at the internal stucture level we need to add an
extra field, that is detected at a completely different time in parsing
too ... more complex in general, but I can understand the purity POV.

Daniel

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