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

[Michael S. Tsirkin]

On Wed, Jun 25, 2014 at 05:50:16PM +0800, Chen, Tiejun wrote:
> On 2014/6/25 17:31, Paolo Bonzini wrote:
> >Il 25/06/2014 11:21, Chen, Tiejun ha scritto:
> >>>Adding a vendor-specific capability or BAR
> >>>in an existing device is painful - hard to find
> >>>free space for it.
> >>
> >>Yes, this is a potential risk as well since we can't guarantee current
> >>free space is always valid for ever.
> >
> >For past devices, we know which BARs they use.  For future devices, it
> >would be nice if the PCH/MCH backdoor was specified so that we know they
> >will leave a free BAR for virtualization.
> >
> 
> Now I'm a bit confused about BAR here.
> 
> 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?
> 
> Thanks
> Tiejun

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.

-- 
MST