Re: [Qemu-devel] [PATCH 5/8] pci: Replace pci_find_domain() with more general pci_root_bus_path()

[Paolo Bonzini <pbonzini@redhat.com>]

Il 23/05/2013 13:04, Michael S. Tsirkin ha scritto:
>> > Most current uses of pci_find_domain() are for error or informational
>> > messages, so the change in identifiers should be harmless.  The exception
>> > is pci_get_dev_path(), whose results form part of migration streams.  To
>> > maintain compatibility with old migration streams, the PIIX PCI host is
>> > altered to always supply "0000" for this path, which matches the old domain
>> > number (since the code didn't actually support domains other than 0).
>> > 
>> > For the pseries (spapr) PCI bridge we use a different platform-unique
>> > identifier (pseries machines can routinely have dozens of PCI host
>> > bridges).  Theoretically that breaks migration streams, but given that we
>> > don't yet have migration support for pseries, it doesn't matter.
>> > 
>> > Any other machines that have working migration support including PCI
>> > devices will need to be updated to maintain migration stream compatibility.
>> > 
>> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> AFAIK PC is the only one with working migration, yes, but
> we have Q35 as well which can be migrated.

Are we already supporting backwards/forwards migration with Q35?

Paolo