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

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

> -----Original Message-----
> From: Gerd Hoffmann [mailto:kraxel@xxxxxxxxxx]
> Sent: Thursday, May 22, 2014 1:40 PM
> To: Chen, Tiejun
> Cc: Anthony PERARD; Daniel P. Berrange; peter.maydell@xxxxxxxxxx;
> xen-devel@xxxxxxxxxxxxxxxxxxx; mst@xxxxxxxxxx;
> stefano.stabellini@xxxxxxxxxxxxx; Kay, Allen M; Kelly.Zytaruk@xxxxxxx;
> qemu-devel@xxxxxxxxxx; Zhang, Yang Z; anthony@xxxxxxxxxxxxx
> Subject: Re: [Qemu-devel] [v2][PATCH 4/8] xen, gfx passthrough: reserve
> 00:02.0 for INTEL IGD
> 
>   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 ?

Yes, this is exactly what I did as Anthony told me to add these two lines:

> xen_platform_pci=0
> device_model_args_hvm = [ '-device', 'xen-platform,addr=0x3' ]

But also as I already reply to Anthony yesterday, this doesn't work

http://lists.gnu.org/archive/html/qemu-devel/2014-05/msg04101.html

I think this only work with some legacy xen/qemu which don't introduce to 
support ACPI pcihp.

> 
> 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, ...).
> 

Currently looks 'xen-platform' itself can't be created, not those devices 
existed on that.

Thanks
Tiejun
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