On Wed, 21 Jan 2015, Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote:
> On Wed, 21 Jan 2015, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
>> On Wed, Jan 21, 2015 at 10:35:58AM +0100, Daniel Vetter wrote:
>>> On Tue, Jan 20, 2015 at 05:21:42PM +0000, David Woodhouse wrote:
>>> > Commit 82460d972 ("drm/i915: Rework ppgtt init to no require an aliasing
>>> > ppgtt") introduced a regression on Broadwell, triggering the following
>>> > IOMMU fault at startup:
>>> >
>>> > vgaarb: device changed decodes: PCI:0000:00:02.0,olddecodes=io+mem,decodes=io+mem:owns=io+mem
>>> > dmar: DRHD: handling fault status reg 2
>>> > dmar: DMAR:[DMA Write] Request device [00:02.0] fault addr 880000
>>> > DMAR:[fault reason 23] Unknown
>>> > fbcon: inteldrmfb (fb0) is primary device
>>> >
>>> > Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
>>> > Cc: stable@xxxxxxxxxxxxxxx
>>>
>>> I sugggested this change to David after staring at the offending patch for
>>> a while. I have no idea and theory whatsoever why this would upset the gpu
>>> less than the other way round. But it seems to work. David promised to
>>> chase hw people a bit more to get a more meaningful answer.
>>
>> The issue is likely the execution of the golden render state batch
>> concurrently with the flip over to ppgtt. The GPU throws a pagefault and
>> we get an ERROR reported.
>>
>> http://patchwork.freedesktop.org/patch/38270/
>> http://patchwork.freedesktop.org/patch/38269/
>
> Pushed the revert to drm-intel-fixes, it's cc: stable and it's getting
> late in the rc's too. Thanks for the patch and review.
s/revert/David's patch/ to be clear.
BR,
Jani.
>
> BR,
> Jani.
>
>
>> -Chris
>>
>> --
>> Chris Wilson, Intel Open Source Technology Centre
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>
> --
> Jani Nikula, Intel Open Source Technology Center
--
Jani Nikula, Intel Open Source Technology Center
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