[Intel-gfx] [PATCH 2/2] drm/i915/execlists: Verify we don't submit two identical CCIDs

[Chris Wilson]

Quoting Mika Kuoppala (2020-04-27 18:31:37)
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> 
> > Check that we do not submit two contexts into ELSP with the same CCID
> > [upper portion of the descriptor].
> >
> > References: https://gitlab.freedesktop.org/drm/intel/-/issues/1793
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_lrc.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> > index d68a04f2a9d5..f8a8cd72f227 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> > @@ -1621,6 +1621,7 @@ assert_pending_valid(const struct intel_engine_execlists *execlists,
> >       struct i915_request * const *port, *rq;
> >       struct intel_context *ce = NULL;
> >       bool sentinel = false;
> > +     u32 ccid = -1;
> >  
> >       trace_ports(execlists, msg, execlists->pending);
> >  
> > @@ -1654,6 +1655,14 @@ assert_pending_valid(const struct intel_engine_execlists *execlists,
> >               }
> >               ce = rq->context;
> >  
> > +             if (ccid == upper_32_bits(ce->lrc_desc)) {
> > +                     GEM_TRACE_ERR("Dup ccid:%x context:%llx in pending[%zd]\n",
> > +                                   ccid, ce->timeline->fence_context,
> > +                                   port - execlists->pending);
> 
> The trace was lost, atleast from me, on the previous logs I looked
> and thus the value. trace buffer overflowed? But if it
> was reader error, then perhaps putting this explicitly in dmesg
> is not necessary.

The trick is to look at the pstores. Or to reproduce it locally where
you can remotely capture the full trace.
-Chris