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Re: [libvirt] [PATCH 12/12] Detect PCI addresses at QEMU startup



On Fri, Dec 18, 2009 at 02:04:04PM +0000, Mark McLoughlin wrote:
> On Fri, 2009-12-18 at 13:59 +0000, Daniel P. Berrange wrote:
> > > The plan we had to future proof this was that libvirt would assign an id
> > > (using -device foo,id=bar) and 'info pci' would include the device id in
> > > its output.
> > > 
> > > Once you have that, you no longer need to make assumptions about what
> > > product:vendor is used for each device or what order addresses are
> > > allocated. It's a simple addition to qemu and a simple addition to your
> > > 'info pci' parsing code, but I think we'd rest easier wrt. future
> > > compatibility.
> > 
> > That would be preferable, but the trouble is that will only work with
> > QEMU >= 0.12. Using the 'info pci' output works for all QEMUs. By 'works'
> > I mean it lets us handle unplug even of devices present at startup. It
> > obviously doesn't allow for static PCI addresing, since that requires
> > the new -device arg.
> 
> Yep, I didn't mean to suggest that you shouldn't go ahead with your
> approach.
> 
> Just that if qemu had the id listed in 'info pci', libvirt could use
> that with versions of qemu that supply it and we'd then be less exposed
> to future changes.

For QEMU >= 0.12, it might also be possible to use the 'info qtree' data
instead of 'info pci' 

Daniel
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