drm/i915: Introduce execlist context status change notification

This patch introduces an approach to track the execlist context status
change.

GVT-g uses GVT context as the "shadow context". The content inside GVT
context will be copied back to guest after the context is idle. And GVT-g
has to know the status of the execlist context.

This function is configurable when creating a new GEM context. Currently,
Only GVT-g will create the "status-change-notification" enabled GEM
context.

v10:

- Fix the identation. (Joonas)

v8:

- Remove the boolean flag in struct i915_gem_context. (Joonas)

v7:

- Remove per-engine ctx status notifiers. Use one status notifier for all
engines. (Joonas)
- Add prefix "INTEL_" for related definitions. (Joonas)
- Refine the comments in execlists_context_status_change(). (Joonas)

v6:

- When !CONFIG_DRM_I915_GVT, make GVT code as dead code then compiler
could automatically eliminate them for us. (Chris)
- Always initialize the notifier header, so it could be switched on/off
at runtime. (Chris)

v5:

- Only compile this feature when CONFIG_DRM_I915_GVT is enabled.(Tvrtko)

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> (v8)
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466078825-6662-8-git-send-email-zhi.a.wang@intel.com
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index bd1360259ac5..d9e30e111067 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -298,6 +298,7 @@ __create_hw_context(struct drm_device *dev,
 	ctx->ring_size = 4 * PAGE_SIZE;
 	ctx->desc_template = GEN8_CTX_ADDRESSING_MODE(dev_priv) <<
 			     GEN8_CTX_ADDRESSING_MODE_SHIFT;
+	ATOMIC_INIT_NOTIFIER_HEAD(&ctx->status_notifier);
 
 	return ctx;