drm/i915/context: switch contexts with execbuf2

Use the rsvd1 field in execbuf2 to specify the context ID associated
with the workload. This will allow the driver to do the proper context
switch when/if needed.

v2: Add checks for context switches on rings not supporting contexts.
Before the code would silently ignore such requests.
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -1044,6 +1044,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	struct drm_i915_gem_object *batch_obj;
 	struct drm_clip_rect *cliprects = NULL;
 	struct intel_ring_buffer *ring;
+	u32 ctx_id = i915_execbuffer2_get_context_id(*args);
 	u32 exec_start, exec_len;
 	u32 seqno;
 	u32 mask;
@@ -1065,9 +1066,19 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 		break;
 	case I915_EXEC_BSD:
 		ring = &dev_priv->ring[VCS];
+		if (ctx_id != 0) {
+			DRM_DEBUG("Ring %s doesn't support contexts\n",
+				  ring->name);
+			return -EPERM;
+		}
 		break;
 	case I915_EXEC_BLT:
 		ring = &dev_priv->ring[BCS];
+		if (ctx_id != 0) {
+			DRM_DEBUG("Ring %s doesn't support contexts\n",
+				  ring->name);
+			return -EPERM;
+		}
 		break;
 	default:
 		DRM_DEBUG("execbuf with unknown ring: %d\n",
@@ -1261,6 +1272,10 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 			goto err;
 	}
 
+	ret = i915_switch_context(ring, file, ctx_id);
+	if (ret)
+		goto err;
+
 	trace_i915_gem_ring_dispatch(ring, seqno);
 
 	exec_start = batch_obj->gtt_offset + args->batch_start_offset;
@@ -1367,6 +1382,7 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
 	exec2.num_cliprects = args->num_cliprects;
 	exec2.cliprects_ptr = args->cliprects_ptr;
 	exec2.flags = I915_EXEC_RENDER;
+	i915_execbuffer2_set_context_id(exec2, 0);
 
 	ret = i915_gem_do_execbuffer(dev, data, file, &exec2, exec2_list);
 	if (!ret) {

include/drm/i915_drm.h

@@ -663,13 +663,19 @@ struct drm_i915_gem_execbuffer2 {
 #define I915_EXEC_CONSTANTS_ABSOLUTE 	(1<<6)
 #define I915_EXEC_CONSTANTS_REL_SURFACE (2<<6) /* gen4/5 only */
 	__u64 flags;
-	__u64 rsvd1;
+	__u64 rsvd1; /* now used for context info */
 	__u64 rsvd2;
 };
 
 /** Resets the SO write offset registers for transform feedback on gen7. */
 #define I915_EXEC_GEN7_SOL_RESET	(1<<8)
 
+#define I915_EXEC_CONTEXT_ID_MASK	(0xffffffff)
+#define i915_execbuffer2_set_context_id(eb2, context) \
+	(eb2).rsvd1 = context & I915_EXEC_CONTEXT_ID_MASK
+#define i915_execbuffer2_get_context_id(eb2) \
+	((eb2).rsvd1 & I915_EXEC_CONTEXT_ID_MASK)
+
 struct drm_i915_gem_pin {
 	/** Handle of the buffer to be pinned. */
 	__u32 handle;