[PATCH] UBUNTU: SAUCE: i915: ubreak G33 GTT size calculation

[Kees Cook]

Hi Andy,

On Fri, Jul 02, 2010 at 10:15:57AM +0100, Andy Whitcroft wrote:
> On Thu, Jul 01, 2010 at 01:19:25PM -0700, Kees Cook wrote:
> > Upstream fixed https://bugzilla.kernel.org/show_bug.cgi?id=15733
> > by correctly calculating the GTT size using aperture size
> > on non-G33 hardware.  In the process, the G33 case was
> > also changed, which lead to the regression documented in
> > https://bugzilla.kernel.org/show_bug.cgi?id=16294
> > 
> > This patch reverts the G33 logic without re-breaking the non-G33 logic.
> > 
> > Signed-off-by: Kees Cook <kees.cook at canonical.com>
> > ---
> >  drivers/char/agp/intel-gtt.c |    7 +++++++
> >  1 files changed, 7 insertions(+), 0 deletions(-)
> > 
> > diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c
> > index 9344216..472d9f7 100644
> > --- a/drivers/char/agp/intel-gtt.c
> > +++ b/drivers/char/agp/intel-gtt.c
> > @@ -1229,6 +1229,13 @@ static int intel_i915_get_gtt_size(void)
> >  				(gmch_ctrl & G33_PGETBL_SIZE_MASK));
> >  			size = 512;
> >  		}
> > +		/* revert the G33 logic changes due to
> > +		   https://bugzilla.kernel.org/show_bug.cgi?id=16294
> > +		   without re-breaking the non-G33 case which motivated
> > +		   the change from
> > +		   https://bugzilla.kernel.org/show_bug.cgi?id=15733
> > +		 */
> > +		size = 1024;
> 
> This seems to just slam the size to 1024 having spent some effort to
> calculate it.  I assume therefore that this is not an upstream ready
> patch?

Correct.  And my system (as well as any other G33 Intel system) is
unbootable without this correction.  Upstream basically said, "oh, yeah, I
guess that calculation isn't correct, we'll have to find someone who know
the hardware better."  In the meantime, I'm proposing this as a compromise
-- it restores the Lucid behavior (unconditionally size=1024) for G33
hardware, and retains the Maverick behavior (size=aperture) for non-G33
hardware.

-Kees

-- 
Kees Cook
Ubuntu Security Team