Re: [Xen-devel] [Qemu-devel] [PATCH v3 11/11] igd: move igd-passthrough-isa-bridge creation to machine init

[Gerd Hoffmann <kraxel@xxxxxxxxxx>]

  Hi,

> > That is true. Given that the only qemu-xen codebase with igd support is
> > 4.7 and 4.7 hasn't been released yet, I am OK with changing the guest
> > visible PCI layout. I might ask for your help in backporting the patches
> > ;-)

What are the 4.7 release plans btw?

> One thing that I forgot to consider is that QEMU 2.5 has been released
> with igd passthrough too and Xen 4.6 + QEMU 2.5 is a combination we
> should support.
> 
> However QEMU 2.5 has a serious bug
> (http://marc.info/?l=qemu-devel&m=145172165010604) which probably
> prevents igd passthrough from working at all.

Stumbled over that one too, so my series has a (different) fix for it as
well.

> I asked Xudong to investigate.  I am thinking that if the feature
> works in 2.5, we need to support it, therefore we cannot break
> migration by changing the PCI layout.

I'd expect it is broken (at least for older guests).  In case 2.5 works
fine as-is we should be able to ditch
TYPE_IGD_PASSTHROUGH_I440FX_PCI_DEVICE altogether b/c it is a no-op in
2.5 because of the bug.

But lets wait for the test results ...

> Otherwise if the feature doesn't work, we could take the liberty to
> make the change.  Do you agree?

Yes.

cheers,
  Gerd


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