[Intel-gfx] [PATCH 9/9] drm/i915: Introduce GVT context creation API

[Zhi Wang]

GVT workload scheduler needs special host LRC contexts, the so called
"shadow LRC context" to submit guest workload to host i915. During the
guest workload submission, GVT fills the shadow LRC context with the
content of guest LRC context: engine context is copied without changes,
ring context is mostly owned by host i915.

The GVT-g workload scheduler flow:

         +-----------+                   +-----------+
         | GVT Guest |                   | GVT Guest |
         +-+-----^---+                   +-+-----^---+
           |     |                         |     |
           |     | GVT-g                   |     | GVT-g
vELSP write|     | emulates     vELSP write|     | emulates
           |     | Execlist/CSB            |     | Execlist/CSB
           |     | Status                  |     | Status
           |     |                         |     |
    +------v-----+-------------------------v-----+---------+
    |           GVT Virtual Execlist Submission            |
    +------+-------------------------------+---------------+
           |                               |
           | Per-VM/Ring Workoad Q         | Per-VM/Ring Workload Q
   +---------------------+--+      +------------------------+
       +---v--------+    ^             +---v--------+
       |GVT Workload|... |             |GVT Workload|...
       +------------+    |             +------------+
                         |
                         | Pick Workload from Q
    +--------------------+---------------------------------+
    |                GVT Workload Scheduler                |
    +--------------------+---------------------------------+
                         |         * Shadow guest LRC context
                  +------v------+  * Shadow guest ring buffer
                  | GVT Context |  * Scan/Patch guest RB instructions
                  +------+------+
                         |
                         v
              Host i915 GEM Submission
v5:
- Only compile this feature when CONFIG_DRM_I915_GVT is enabled.
- Rebase the code into new repo.
- Add a comment about the ring buffer size.

v2:

Mostly based on Daniel's idea. Call the refactored core logic of GEM
context creation service and LRC context creation service to create the GVT
context.

Signed-off-by: Zhi Wang <zhi.a.wang at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h         |  1 +
 drivers/gpu/drm/i915/i915_gem_context.c | 31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b8f1e9a..7e5a506 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3398,6 +3398,7 @@ i915_gem_context_get(struct drm_i915_file_private *file_priv, u32 id);
 void i915_gem_context_free(struct kref *ctx_ref);
 struct drm_i915_gem_object *
 i915_gem_alloc_context_obj(struct drm_device *dev, size_t size);
+struct intel_context *i915_gem_create_gvt_context(struct drm_device *dev);
 static inline void i915_gem_context_reference(struct intel_context *ctx)
 {
 	kref_get(&ctx->ref);
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 057e2fe..a69bb86 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -354,6 +354,37 @@ err_destroy:
 	return ERR_PTR(ret);
 }
 
+#if IS_ENABLED(CONFIG_DRM_I915_GVT)
+/**
+ * i915_gem_create_gvt_context - create a GVT GEM context
+ * @dev: drm device *
+ *
+ * This function is used to create a GVT specific GEM context.
+ *
+ * Returns:
+ * pointer to intel_context on success, NULL if failed
+ *
+ */
+struct intel_context *
+i915_gem_create_gvt_context(struct drm_device *dev)
+{
+	struct intel_context *ctx;
+
+	mutex_lock(&dev->struct_mutex);
+
+	ctx = i915_gem_create_context(dev, NULL);
+	if (IS_ERR(ctx))
+		goto out;
+
+	ctx->enable_status_change_notification = true;
+	ctx->ring_buffer_size = 512 * PAGE_SIZE; /* Max ring buffer size */
+	ctx->single_submission = true;
+out:
+	mutex_unlock(&dev->struct_mutex);
+	return ctx;
+}
+#endif
+
 static void i915_gem_context_unpin(struct intel_context *ctx,
 				   struct intel_engine_cs *engine)
 {
-- 
1.9.1