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

[Chris Wilson]

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