[Intel-gfx] [PATCH v12 8/9] drm/i915: Support LRC context single submission

[Zhi Wang]

This patch introduces the support of LRC context single submission.
As GVT context may come from different guests, which require different
configuration of render registers. It can't be combined into a dual ELSP
submission combo.

Only GVT-g will create this kinds of GEM context currently.

v8:

- Rename the data member in struct i915_gem_context. (Chris)

v7:

- Fix typos in commit message. (Joonas)

v6:
- Make GVT code as dead code when !CONFIG_DRM_I915_GVT. (Chris)

v5:

- Only compile this feature when CONFIG_DRM_I915_GVT=y. (Tvrtko)

Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h  |  1 +
 drivers/gpu/drm/i915/intel_lrc.c | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 85b92b2..34a1c18 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -883,6 +883,7 @@ struct i915_gem_context {
 	u32 ring_size;
 	u32 desc_template;
 	struct atomic_notifier_head status_notifier;
+	bool execlists_force_single_submission;
 
 	struct list_head link;
 
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 4eed9247..81d9caf 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -444,6 +444,21 @@ static void execlists_context_unqueue(struct intel_engine_cs *engine)
 			i915_gem_request_unreference(req0);
 			req0 = cursor;
 		} else {
+			/* Compiler will do the dead-code elimination */
+			if (IS_ENABLED(CONFIG_DRM_I915_GVT)) {
+				/*
+				 * req0 (after merged) ctx requires single
+				 * submission, stop picking
+				 */
+				if (req0->ctx->execlists_force_single_submission)
+					break;
+				/*
+				 * req0 ctx doesn't require single submission,
+				 * but next req ctx requires, stop picking
+				 */
+				if (cursor->ctx->execlists_force_single_submission)
+					break;
+			}
 			req1 = cursor;
 			WARN_ON(req1->elsp_submitted);
 			break;
-- 
1.9.1