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

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

On Thu, Jun 26, 2014 at 12:03:58PM +0200, Paolo Bonzini wrote:
> Il 26/06/2014 11:18, Chen, Tiejun ha scritto:
> >
> >>
> >>- offsets 0x0000..0x0fff map to configuration space of the host MCH
> >>
> >
> >Are you saying the config space in the video device?
> 
> No, I am saying in a new BAR, or at some magic offset of an existing MMIO
> BAR.
> 
> Paolo

I think v5 goes a bit overboard and overrides too many registers,
driver likely needs much less.

But IMHO retro-fitting this into PIIX is where the problem is.
We could invent 1000 ways to do this, all of varying levels of
ugliness.

But why don't we start by more or less cleanly emulating what the driver
needs?  If we start with Q35 - it shouldn't be hard to tweak it's MCH to
add the necessary config space, right?

I know xen doesn't support q35 now but it's opensource :)

I think that's a good step 1. We can do PV hacks on top if we
decide they aren't too painful.

-- 
MST