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.
BR,
Jani.
> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre
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--
Jani Nikula, Intel Open Source Technology Center
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