On 16/11/2015 10:52, Marcel Apfelbaum wrote: > On 11/16/2015 10:40 AM, Paolo Bonzini wrote: >> >> >> On 15/11/2015 16:39, Marcel Apfelbaum wrote: >>> Addressed Gerd Hoffmann comments: >>> - Added x-enable-internal-bridge compat property to keep the PCI >>> bridge for older machine to avoid breaking migration. >> >> This will break PXB command lines written for "-M pc" in QEMU <= 2.5. >> Technically there's no prohibition against doing so, but we've never >> done it; I'm not sure why we should start doing so now. > > Hi Paolo, > > Can you please explain how does it break the command line? > > For QEMU < 2.5 we automatically have the x-enable-internal-bridge > compat property "on" > so the command line remains the same. > > For QEMU >= 2.5 is "off" by default and the bridge disappear, without > command line changes.
If you were using "-M pc", and you expected "-device" to place things under the PCI-to-PCI bridge, that command line will not work anymore I think. Management tools can work around it. They can always set the new property to off---which by the way means it should not be "x" prefixed---and assume the PCI-to-PCI bridge is there if the property doesn't exist. But it's inconvenient, and we try to avoid lockstep changes to QEMU and management. Paolo >> Can we have two devices, on for a PCI expander bridge and one for a PCIe >> expander bridge? > > Gerd also asked for this, OK, I am going for it. > > Thanks, > Marcel > >> >> Paolo >> >
