The kernel context exists simply as a placeholder and should never be
executed with a render context. It does not need the golden render
state, as that will always be applied to a user context. By skipping the
initialisation we can avoid issues in attempting to program the golden
render context when trying to make the hardware idle.

v2: Rebase

Testcase: igt/drm_module_reload_basic #byt
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95634
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 14 +++++++++-----
 drivers/gpu/drm/i915/intel_ringbuffer.c | 10 ++++++++++
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c 
b/drivers/gpu/drm/i915/i915_gem_context.c
index c620fe6c9d96..60967b935d72 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -434,13 +434,17 @@ void i915_gem_context_lost(struct drm_i915_private 
*dev_priv)
                        i915_gem_context_unpin(engine->last_context, engine);
                        engine->last_context = NULL;
                }
-
-               /* Force the GPU state to be reinitialised on enabling */
-               dev_priv->kernel_context->engine[engine->id].initialised =
-                       engine->init_context == NULL;
        }
 
-       /* Force the GPU state to be reinitialised on enabling */
+       /* Force the GPU state to be restored on enabling */
+       if (!i915.enable_execlists) {
+               for_each_engine(engine, dev_priv) {
+                       struct intel_context *kce =
+                               &dev_priv->kernel_context->engine[engine->id];
+
+                       kce->initialised = true;
+               }
+       }
        dev_priv->kernel_context->remap_slice = ALL_L3_SLICES(dev_priv);
 }
 
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c 
b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 86b80b4727fb..04a2d141e690 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2338,6 +2338,16 @@ static int intel_ring_context_pin(struct 
i915_gem_context *ctx,
                        goto error;
        }
 
+       /* The kernel context is only used as a placeholder for flushing the
+        * active context. It is never used for submitting user rendering and
+        * as such never requires the golden render context, and so we can skip
+        * emitting it when we switch to the kernel context. This is required
+        * as during eviction we cannot allocate and pin the renderstate in
+        * order to initialise the context.
+        */
+       if (ctx == ctx->i915->kernel_context)
+               ce->initialised = true;
+
        i915_gem_context_reference(ctx);
        return 0;
 
-- 
2.8.1

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