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

[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.

Marek