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

[Chen, Tiejun]

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