[Mesa-dev] [PATCH 2/2] winsys/amdgpu: disable CE preamble until the kernel is fixed

Christian König deathsimple at vodafone.de
Fri May 27 09:12:04 UTC 2016

Am 27.05.2016 um 00:19 schrieb Marek Olšák:
> On Fri, May 27, 2016 at 12:13 AM, Alex Deucher <alexdeucher at gmail.com> wrote:
>> On Thu, May 26, 2016 at 5:51 PM, Marek Olšák <maraeo at gmail.com> wrote:
>>> From: Marek Olšák <marek.olsak at amd.com>
>>> SDMA submission somehow interacts with the skipping CE preamble logic.
>>> This is a workaround for current kernels which have the bug.
>>> Sadly, I can't see what's wrong with the kernel driver. The CE preamble
>>> handling there looks good to me.
>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95545
>> What exactly is going wrong?  Is the kernel not scheduling the
>> preamble or is the ordering wrong or something else?
> There are VM faults for addresses that are too far away from memory
> allocated by the process.
> It looks like the contents of CE RAM come from a different process,
> which suggests that the CE preamble IB was skipped.
> Disabling the CE preamble IB means that the preamble packets are added
> to the main CE IB instead, which makes the problem go away.

Just a guess, but does commit 9f8fb5a2b339ba83493991ca8f1173a939a696d3 
in Alex drm-next-4.7 tree helps with the problem?

commit 9f8fb5a2b339ba83493991ca8f1173a939a696d3
Author: Christian König <christian.koenig at amd.com>
Date:   Fri May 6 14:52:57 2016 +0200

     drm/amdgpu: move preamble IB handling into common code

     This fixes the handling which was completely broken when you
     ad more than one preamble IB.


> Marek
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