[libvirt] [PATCH 3/4] Explicitly represent balloon device in XML and handle PCI address

[Daniel P. Berrange]

On Tue, Jul 20, 2010 at 08:59:29AM -0600, Eric Blake wrote:
> On 07/20/2010 08:49 AM, Daniel P. Berrange wrote:
> > On Tue, Jul 20, 2010 at 10:39:01AM -0400, Cole Robinson wrote:
> >> On 07/20/2010 09:09 AM, Daniel P. Berrange wrote:
> >>> From: Daniel P. Berrange <dan at berrange.com>
> >>>
> >>> To allow compatability with older QEMU PCI device slot assignment
> >>> it is neccessary to explicitly track the balloon device in the
> >>> XML. This introduces a new device
> >>>
> >>>    <memballoon model='virtio|xen'/>
> >>>
> >>> It can also have a PCI address, auto-assigned if neccessary.
> >>>
> >>> The memballoon will be automatically added to all Xen and QEMU
> >>> guests by default.
> >>>
> >>
> >> Is there a way for users to remove/disable the balloon device? Certainly
> >> doesn't block this patch, but someone is going to ask for it eventually.
> > 
> > There isn't an easy way to allow for this without breaking back
> > compatability. We have always enabled the balloon driver, even 
> > though nothing was in the XML. Thus we can't simply leave out
> > the '<memballoon>' element and expect the balloon to go away
> > as that would break compat.
> 
> You are correct that we can't remove XML to remove the feature, but we
> can add some.  What about using <memballoon model='none'/> as a way to
> explicitly request that it be excluded?

Sure, but that's what I meant by not easy - that kind of thing is really
disgusting.


Daniel
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