[Intel-gfx] [PATCH] drm/i915: Use Graphics Base of Stolen Memory on all gen3+

[Chris Wilson]

On Thu, Jul 04, 2013 at 01:38:05AM +0200, Daniel Vetter wrote:
> On Thu, Jul 4, 2013 at 1:33 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > On Thu, Jul 04, 2013 at 01:26:03AM +0200, Daniel Vetter wrote:
> >> On Thu, Jul 4, 2013 at 1:23 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> >> > So I made the mistake of missing that the desktop and mobile chipsets
> >> > have different layouts in their PCI configurations, and we were
> >> > incorrectly setting the wrong physical address for stolen memory on
> >> > mobile chipsets.
> >> >
> >> > Since all gen3+ are actually consistent in the location of the GBSM
> >> > register in the PCI configuration space on device 2 (the GPU), use it.
> >> >
> >> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> >> > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> >> > Cc: stable at vger.kernel.org
> >>
> >> Nope, not cc: stable since the last time around the overlay blew up in
> >> flames ...
> >
> > You can comment out gen3, but the dangerous part is that we are
> > overwriting random physical addresses.
> 
> Hm, should we do a request_region on the stolen range to double-check
> that? Just for paranoia and in case the BIOS does something terrible
> ...

Afaict, request_region() is only being used to reserve and check for
conflicting io ranges. I don't know if that will give us protection
against overwriting user/kernel memory. Maybe it does - I haven't found
the documentation for it yet.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre