Re: [PATCH] drm/i915: disable cpu relocs on ilk and earlier

Daniel Vetter
2012-10-18T07:34:41Z

On Mon, Oct 15, 2012 at 5:11 PM, Greg KH <gregkh@linuxfoundation.org> wrote:
> On Mon, Oct 15, 2012 at 10:11:22AM +0200, Daniel Vetter wrote:
>> Hi Greg&stable-team,
>>
>> The below patch papers over a graphics corruption issue in 3.5/3.6. The
>> regression happened due to pwrite tunings in 3.5, which made cpu relocations
>> much more likely.
>>
>> The issue seems to have disappeared in 3.7-rc1, but it takes a few days to test
>> a patch, so we haven't figured out what exactly fixed things. Now users are
>> taking out their pitchforks already, so instead of wasting more days (maybe
>> weeks?) to fully understand the bug before backporting the fix, we've opted for
>> the below disable patch, which should have minimal impact (at most it undoes the
>> tuning improvements in 3.5).
>>
>> Patch is tested by reporters & acked by all relevant ppl, please apply to
>> 3.5/3.6 series kernels.
>
> No, I'd really like to wait until you figure out what is happening in
> 3.7-rc1 right now before applying the patch. We have the rule, "it must
> be in Linus's tree first" for a very good reason :)

Ok, the verdict is in (thanks a lot Dave for testing all these
different patches) and it seems like

commit 504c7267a1e84b157cbd7e9c1b805e1bc0c2c846
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu Aug 23 13:12:52 2012 +0100

drm/i915: Use cpu relocations if the object is in the GTT but not mappable

from upstream nicely papers over the issues. Please apply to 3.5/3.6
stable series (earlier kernels don't exhibit the problem).

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=852210
Tested-by: Dave Airlie <airlied@gmail.com>

Thanks, Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch