Re: [Qemu-devel] [v2][PATCH 4/8] xen, gfx passthrough: reserve 00:02.0 for INTEL IGD

[Gerd Hoffmann <kraxel@redhat.com>]

  Hi,

> > According to our discussions, I realize we may have some plans or policies
> > dedicated to how to assign devfn, but to support GFX passthrough for XEN, I
> > think currently it may be a better solution to adopt #1 simply like this:
> > 
> > diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c index eaf3e61..500b3c2
> > 100644
> > --- a/hw/i386/pc_piix.c
> > +++ b/hw/i386/pc_piix.c
> > @@ -386,7 +386,7 @@ static void pc_xen_hvm_init(QEMUMachineInitArgs
> > *args)
> > 
> >      bus = pci_find_primary_bus();
> >      if (bus != NULL) {
> > -        pci_create_simple(bus, -1, "xen-platform");
> > +        pci_create_simple(bus, PCI_DEVFN(3,0), "xen-platform");
> >      }
> >  }
> >  #endif
> > 
> > Then we can go out to plan how to assign devfn in common, is this fine?

Somewhere else in the thread someone listed a libxl config file snippet
which is supposed to disable the xen platform device.  Which doesn't
work with upstream qemu for some reason.

Searching ...   ah, here:
http://lists.gnu.org/archive/html/qemu-devel/2014-05/msg03996.html

So, how about making "xen_platform_pci=0" working correctly ?

Another useful thing would be to not create the xen platform device in
case "-nodefaults" was specified on the command line (that switch turns
off a bunch of other devices present by default: vga, nic, cdrom, ...).

cheers,
  Gerd