[Intel-gfx] [PATCH v3] drm/i915/selftests: Check the context size

[Chris Wilson]

Quoting Daniele Ceraolo Spurio (2019-08-16 22:50:43)
> 
> 
> On 8/16/19 12:17 PM, Chris Wilson wrote:
> > +static int live_context_size(void *arg)
> > +{
> > +             /*
> > +              * Hide the old default state -- we lie about the context size
> > +              * and get confused when the default state is smaller than
> > +              * expected. For our do nothing request, inheriting the
> > +              * active state is sufficient, we are only checking that we
> > +              * don't use more than we planned.
> > +              */
> > +             saved.state = fetch_and_zero(&engine->default_state);
> > +             saved.pinned = fetch_and_zero(&engine->pinned_default_state);
> > +
> > +             engine->context_size += I915_GTT_PAGE_SIZE;
> 
> if CONFIG_DRM_I915_DEBUG_GEM is set we already bump the size inside the 
> context_alloc(), do we need to bump it again here?

No, it comes out in the wash as we apply the same redzone twice. At least,
adding and checking a second page after what we believe to be the end of
the context image does not help sensitivity (so makes a worse test imo).

The benefit of this selftest is that we check all submission modes, and
can set up any execution pattern we think might be required (within
reason). So, I think it still has a use even if we need to remind
ourselves of the overlap.
-Chris