[Intel-gfx] [PATCH v6 7/9] drm/i915: Introduce execlist context status change notification

[Zhi Wang]

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. So GVT-g
has to know the status of the execlist context.

This function is configurable in the context creation service. Currently,
Only GVT-g will create the "status-change-notification" enabled GEM
context.

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)

Signed-off-by: Zhi Wang <zhi.a.wang at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h  |  2 ++
 drivers/gpu/drm/i915/intel_lrc.c | 24 ++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_lrc.h |  5 +++++
 3 files changed, 31 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index f6cb60a..dee72d3 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -877,9 +877,11 @@ struct i915_gem_context {
 		u64 lrc_desc;
 		int pin_count;
 		bool initialised;
+		struct atomic_notifier_head status_notifier;
 	} engine[I915_NUM_ENGINES];
 	u32 lrc_ring_buffer_size;
 	u32 lrc_addressing_mode_bits;
+	bool enable_lrc_status_change_notification;
 
 	struct list_head link;
 
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index ffb436c..96d20c8 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -404,6 +404,22 @@ static void execlists_submit_requests(struct drm_i915_gem_request *rq0,
 	spin_unlock_irq(&dev_priv->uncore.lock);
 }
 
+static inline void execlists_context_status_change(
+		struct drm_i915_gem_request *rq,
+		unsigned long status)
+{
+	/* The compiler should be fine with the dead-code elimination */
+	if (!IS_ENABLED(CONFIG_DRM_I915_GVT))
+		return;
+
+	if (!rq->ctx->enable_lrc_status_change_notification)
+		return;
+
+	atomic_notifier_call_chain(
+			&rq->ctx->engine[rq->engine->id].status_notifier,
+			status, rq);
+}
+
 static void execlists_context_unqueue(struct intel_engine_cs *engine)
 {
 	struct drm_i915_gem_request *req0 = NULL, *req1 = NULL;
@@ -439,6 +455,11 @@ static void execlists_context_unqueue(struct intel_engine_cs *engine)
 	if (unlikely(!req0))
 		return;
 
+	execlists_context_status_change(req0, CONTEXT_SCHEDULE_IN);
+
+	if (req1)
+		execlists_context_status_change(req1, CONTEXT_SCHEDULE_IN);
+
 	if (req0->elsp_submitted & engine->idle_lite_restore_wa) {
 		/*
 		 * WaIdleLiteRestore: make sure we never cause a lite restore
@@ -477,6 +498,8 @@ execlists_check_remove_request(struct intel_engine_cs *engine, u32 ctx_id)
 	if (--head_req->elsp_submitted > 0)
 		return 0;
 
+	execlists_context_status_change(head_req, CONTEXT_SCHEDULE_OUT);
+
 	list_del(&head_req->execlist_link);
 	i915_gem_request_unreference(head_req);
 
@@ -2489,6 +2512,7 @@ static int execlists_context_deferred_alloc(struct i915_gem_context *ctx,
 	ce->ringbuf = ringbuf;
 	ce->state = ctx_obj;
 	ce->initialised = engine->init_context == NULL;
+	ATOMIC_INIT_NOTIFIER_HEAD(&ce->status_notifier);
 
 	return 0;
 
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index e133c33..7a7ae8d 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -68,6 +68,11 @@ enum {
 #define GEN8_CSB_READ_PTR(csb_status) \
 	(((csb_status) & GEN8_CSB_READ_PTR_MASK) >> 8)
 
+enum {
+	CONTEXT_SCHEDULE_IN = 0,
+	CONTEXT_SCHEDULE_OUT,
+};
+
 /* Logical Rings */
 int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request);
 int intel_logical_ring_reserve_space(struct drm_i915_gem_request *request);
-- 
1.9.1