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

[Michael S. Tsirkin]

On Wed, Jun 25, 2014 at 06:06:50PM +0800, Chen, Tiejun wrote:
> On 2014/6/25 17:59, Paolo Bonzini wrote:
> >Il 25/06/2014 11:55, Michael S. Tsirkin ha scritto:
> >>> You're saying we will reserve a free BAR to address those
> >>information to
> >>> expose to guest, but which device does this free BAR belong to? The
> >>video
> >>> device? Or PCH/MCH?
> >>
> >>If you just want to pass a couple of IDs, then don't, it's a waste.
> >>But I still don't know what problem you are trying to solve,
> >>looking at guest driver did not help.
> >
> >It's not just a couple of IDs, it's also random fields of the MCH
> >configuration space.  Grep drivers/gpu/drm/i915 for bridge_dev.
> >
> 
> Paolo,
> 
> No, we're not pointing the bridge_dev here, which is a host bridge at
> 00:00.0.
> 
> Here it should be a ISA bridge at 00:1f.0. Please see intel_detect_pch() to
> know why we need this.
> 
> Thanks
> Tiejun
> 

So what if you dont?

        if (!pch)
                DRM_DEBUG_KMS("No PCH found.\n");

Is that all? Seems harmless enough.