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Date: Tue, 23 Mar 2010 12:40:05 +0100
Message-ID: <ca2dc2821003230440w3d96612aja0d4e083d3cc8c02@mail.gmail.com>
Subject: Re: [PATCH] intel-agp.c: Fix crash when accessing nonexistent GTT 
	entries in i915
From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
To: Christian Kujau <lists@nerdbynature.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Zhenyu Wang <zhenyuw@linux.intel.com>,
       LKML <linux-kernel@vger.kernel.org>, David.Woodhouse@intel.com,
       dwmw2@infradead.org, eric@anholt.net, ben@decadent.org.uk,
       gregkh@suse.de
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On Tue, Mar 23, 2010 at 5:14 AM, Christian Kujau <lists@nerdbynature.de> wrote:
> 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@gmail.com> wrote:
>> > I bisected in order to find the commit 5877960869333e42ebeb733e8d9d5630ff96d350.
>
> I believe this[0] is fc61901373987ad61851ed001fe971f3ee8d96a3 upstream:

Indeed. Also in

http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.32.y.git;a=commit;h=fc61901373987ad61851ed001fe971f3ee8d96a3

>
> --------
>  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@intel.com>
>  [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@anholt.net>
> --------
>
> Christian.
>
> [0] http://github.com/pfactum/pf-kernel/commit/5877960869333e42ebeb733e8d9d5630ff96d350
> --
> BOFH excuse #384:
>
> it's an ID-10-T error
>