Re: [Qemu-devel] [v5][PATCH 0/5] xen: add Intel IGD passthrough support

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jun 25, 2014 at 02:11:45PM +0200, Paolo Bonzini wrote:
> Il 25/06/2014 12:21, Michael S. Tsirkin ha scritto:
> >So what if you dont?
> >
> >        if (!pch)
> >                DRM_DEBUG_KMS("No PCH found.\n");
> >
> >Is that all? Seems harmless enough.
> >
> 
> The switch statement above sets dev_priv->pch_type.  If it is set wrong,
> everything goes wrong.  grep for HAS_PCH_.
> 
> Paolo

OK, so how about doing this: either for the ISA
bridge, or for the VGA card itself:

    set subsystem vendor id to PCI_VENDOR_ID_XEN,
    set subsystem device id to PCH device id

Your patch seems to emulate revision as well
but I don't see driver using that anywhere.
I would then just update driver with that info.

If you feel the need to support old guests without such a patch, we
could add some generic hook where users supply
device vendor revision id and class, and we create a dummy
device. Let xen management worry about making that match
PCH ISA bridge, or whatever, but let's also create a
clean path going forward.


-- 
MST