Re: [PATCH v3] drm/i915/selftests: Check the context size

[Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>]

On 8/16/19 3:13 PM, Chris Wilson wrote:
> 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
> 

Fair enough. With the above written down as a comment in the code:

Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>

Daniele
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