[Intel-gfx] [PATCH v4 2/2] drm/i915/perf: fix ctx_id read with GuC & ICL

[Lionel Landwerlin]

On 02/06/18 12:52, Chris Wilson wrote:
> Quoting Lionel Landwerlin (2018-06-02 12:29:46)
>> One thing we didn't really understand about the OA report is that the
>> ContextID field (dword 2) is copy of the context descriptor (dword 1).
>>
>> On Gen8->10 and without using GuC we didn't notice the issue because
>> we only checked the 21bits of the ContextID field in the OA reports
>> which matches exactly the hw_id stored into the context descriptor.
>>
>> When using GuC submission we have an issue of a non matching hw_id
>> because GuC uses bit 20 of the hw_id to signal proxy submission. This
>> change introduces a mask to compare only the relevant bits.
>>
>> On ICL the context descriptor format has changed and we failed to
>> address this. On top of using a mask we also need to shift the bits
>> properly.
>>
>> v2: Reuse lrc_desc rather than recomputing part of it (Chris/Michel)
>>
>> v3: Always pin the context we're filtering with (Chris)
>>
>> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
>> Fixes: 1de401c08fa805 ("drm/i915/perf: enable perf support on ICL")
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104252
>> BSpec: 1237
>> Testcase: igt/perf/gen8-unprivileged-single-ctx-counters
> Acked-by: Chris Wilson <chris at chris-wilson.co.uk>
>
> Please ping Michel for an r-b confirmation on using the lrca for the guc
> ctx_id.
> -Chris
>
Got the information from Michel initially ;)
Will wait for his Rb on the last version.
Cheers,

-
Lionel