On Thu, 2017-11-02 at 12:42 +0000, Chris Wilson wrote:
> In the next few patches, we will have a hard requirement that we emit a
> context-switch to the perma-pinned i915->kernel_context (so that we can
> save the HW state using that context-switch). As the first context
> itself may be classed as a kernel context, we want to be explicit in our
> comparison. For an extra-layer of finesse, we can check the last
> unretired context on the engine; as well as the last retired context
> when idle.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
<SNIP>
> @@ -1587,8 +1587,20 @@ bool intel_engines_are_idle(struct drm_i915_private *dev_priv)
>
> bool intel_engine_has_kernel_context(const struct intel_engine_cs *engine)
> {
> - return (!engine->last_retired_context ||
> - i915_gem_context_is_kernel(engine->last_retired_context));
> + const struct i915_gem_context *kctx = engine->i915->kernel_context;
*kernel_context = ...
> + struct drm_i915_gem_request *rq;
> +
> + lockdep_assert_held(&engine->i915->drm.struct_mutex);
> +
> + /* An unretired request? */
> + rq = __i915_gem_active_peek(&engine->timeline->last_request);
> + if (rq)
> + return rq->ctx == kctx;
> +
> + if (!engine->last_retired_context)
> + return true;
> +
> + return engine->last_retired_context == kctx;
It might be worthy dropping a comment that a nonexistent context is
considered kernel context to the *cough*nonexistent*cough* kerneldoc.
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Regards, Joonas
--
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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