Re: [PATCH] drm/i915/oa: Disable OA on Haswell

[Lionel Landwerlin <lionel.g.landwerlin@intel.com>]

On 11/05/18 15:34, Chris Wilson wrote:
> Quoting Lionel Landwerlin (2018-05-11 15:28:24)
>> On 11/05/18 15:18, Chris Wilson wrote:
>>> Quoting Lionel Landwerlin (2018-05-11 15:14:13)
>>>> My understanding of the virtual memory addressing from the GPU is limited...
>>>> But how can the GPU poke at the kernel's allocated data?
>>>> I thought we mapped into the GPU's address space only what is allocated
>>>> through gem.
>>> Correct. The HW should only be accessing the pages through the GTT and
>>> the GTT should only contain known pages (or a pointer to the scratch
>>> page). There is maybe a hole where we are freeing the memory before
>>> the HW has finished using it (still writing through stale TLB and
>>> whatnot even though the system has reallocated the pages), but other
>>> than that quite, quite scary. Hence this awooga.
>>>
>> Oh right...
>>
>> So this patch is a backup if you previous one won't fix the issue we see
>> on CI?
> Yes. Try to fix, it we can't, we disable until we can. It may also be
> purely coincidental that we've seen this bug a few times around the same
> test only on this machine... ;)
> -Chris
>
Trying on a laptop.