Re: [PATCH] intel-agp.c: Fix crash when accessing nonexistent GTTentries in i915

From: Christian Kujau
Date: Tue Mar 23 2010 - 00:16:02 EST


On Mon, 22 Mar 2010 at 20:57, Andrew Morton wrote:
> On Sun, 21 Mar 2010 16:30:20 +0100 Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx> wrote:
> > I bisected in order to find the commit 5877960869333e42ebeb733e8d9d5630ff96d350.

I believe this[0] is fc61901373987ad61851ed001fe971f3ee8d96a3 upstream:

--------
agp/intel-agp: Clear entire GTT on startup

Some BIOSes fail to initialise the GTT, which will cause DMA faults when
the IOMMU is enabled. We need to clear the whole thing to point at the
scratch page, not just the part that Linux is going to use.

Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
[anholt: Note that this may also help with stability in the presence of
driver bugs, by not drawing to memory we don't own]
Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
--------

Christian.

[0] http://github.com/pfactum/pf-kernel/commit/5877960869333e42ebeb733e8d9d5630ff96d350
--
BOFH excuse #384:

it's an ID-10-T error
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