[libvirt] [PATCH] qemu: Use legacy USB on ppc64

[Andrea Bolognani]

On Wed, 2016-07-20 at 16:09 +0200, Andrea Bolognani wrote:
> > It seems that we could solve this by just changing the logic in
> > qemuDomainAssignDevicePCISlots() so that when it is auto-assigning
> > addresses, it always uses 00:00.0 for the USB controller when guest
> > arch is ppc64.
> >  
> > Existing guests deployed from a libvirt version using -device won't
> > be affected, because we'll have recorded a PCI address for that
> > in the XML and continue to use that. ie the auto-allocation logic
> > won't run for them.
> >  
> > Existing guests deployed from a libvirt version using -usb should
> > then get the fixed PCI address of 00:00.0 when they upgrade to the
> > fix libvirt (assuming they didn't get run with a broken libvirt
> > in between).
> 
> Mh, that could actually work! Thanks :)
> 
> I'll try to cook up a patch tomorrow.

Unfortunately Martin pointed out a problem with this plan:
even though they're not actually using it, old guests have
been assigned a PCI address for the USB controller. Which
means we can't tell whether

  <controller type='usb' index='0'>
    <address type='pci' domain='0x0000' bus='0x00'
             slot='0x03' function='0x0'/>
  </controller

is an old guest that should be assigned the 00:00.0 address
or a new guest that should keep using the 00:03.0 address :(

-- 
Andrea Bolognani / Red Hat / Virtualization