On 01/19/2011 11:01 AM, Daniel P. Berrange wrote:
The reason we specify 'bus' is that we wanted to be flexible wrt upgrades of libvirt, without needing restarts of QEMU instances it manages. That way we can introduce new functionality into libvirt that relies on it having previously set 'bus' on all active QEMUs. If QEMU adds PCI-to-PCI bridges, then I wouldn't expect QEMU to be adding the extra bridges. I'd expect that QEMU provided just the first bridge and then libvirt would specify how many more bridges to create at boot or hotplug them later. So it wouldn't ever need to parse topology.
Yeah, but replacing the main chipset will certainly change the PCI topology such that if you're specifying bus=X and addr=X and then also using -M pc, unless you're parsing the default topology to come up with the addressing, it will break in the future.
That's why I think something simpler like a linear index that QEMU maps to a static location in the topology is probably the best future proof interface.
Regards, Anthony Liguori
Regards, Daniel
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