Re: [Qemu-devel] [PATCH V2 0/4] hw/pcie: Multi-root support for Q35

[Marcel Apfelbaum]

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.

> 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