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

[Paolo Bonzini]

Il 03/07/2014 21:09, Jesse Barnes ha scritto:
> Practically speaking, we could probably assume specific CPU/PCH combos,
> as I don't think they're generally mixed across generations, though SNB
> and IVB did have compatible sockets, so there is the possibility of
> mixing CPT and PPT PCHs, but those are register identical as far as the
> graphics driver is concerned, so even that should be safe.

I guess the driver could do that if it finds an unknown PCH device ID. 
But encoding it in the subsystem device ID could also work and it would 
be easy to do in the hypervisor.

> Beyond that, the other MCH data we need to look at is mirrored into the
> GPU's MMIO space on current gens.

Heh, that's exactly the same as the paravirtualized solution we were 
suggesting. ;)

Paolo

> On older gens, we do need to poke at
> the memory controller a bit to get some info (see
> intel_setup_mchbar()), but that's not true of newer stuff.  Looks like
> we only short circuit that on VLV though; we could probably do it on
> SNB+.