[PATCH 39/88] drm/i915: Assign every HW context a unique ID

[Chris Wilson]

The hardware tracks contexts and expects all live contexts (those active
on the hardware) to have a unique identifier. This is used by the
hardware to assign pagefaults and the like to a particular context.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_debugfs.c     |  2 +-
 drivers/gpu/drm/i915/i915_drv.h         |  4 ++++
 drivers/gpu/drm/i915/i915_gem_context.c | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index ffc4734cb2dc..cacbe45b7938 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2014,7 +2014,7 @@ static int i915_context_status(struct seq_file *m, void *unused)
 		    ctx->legacy_hw_ctx.rcs_state == NULL)
 			continue;
 
-		seq_puts(m, "HW context ");
+		seq_printf(m, "HW context %d ", ctx->hw_id);
 		describe_ctx(m, ctx);
 		if (ctx == dev_priv->kernel_context)
 			seq_printf(m, "(kernel context) ");
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index dc3bb5c10957..368fd7090189 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -851,6 +851,7 @@ struct intel_context {
 	struct i915_ctx_hang_stats hang_stats;
 	struct i915_hw_ppgtt *ppgtt;
 
+	unsigned hw_id;
 	unsigned flags;
 #define CONTEXT_NO_ZEROMAP		(1<<0)
 #define CONTEXT_NO_ERROR_CAPTURE	(1<<1)
@@ -1810,6 +1811,9 @@ struct drm_i915_private {
 	DECLARE_HASHTABLE(mm_structs, 7);
 	struct mutex mm_lock;
 
+	struct ida context_hw_ida;
+#define MAX_CONTEXT_HW_ID (1<<20)
+
 	/* Kernel Modesetting */
 
 	struct drm_crtc *plane_to_crtc_mapping[I915_MAX_PIPES];
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index d7d9763a9818..db53d811370d 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -169,6 +169,8 @@ void i915_gem_context_free(struct kref *ctx_ref)
 	if (ctx->legacy_hw_ctx.rcs_state)
 		drm_gem_object_unreference(&ctx->legacy_hw_ctx.rcs_state->base);
 	list_del(&ctx->link);
+
+	ida_simple_remove(&ctx->i915->context_hw_ida, ctx->hw_id);
 	kfree(ctx);
 }
 
@@ -209,6 +211,28 @@ i915_gem_alloc_context_obj(struct drm_device *dev, size_t size)
 	return obj;
 }
 
+static int assign_hw_id(struct drm_i915_private *dev_priv, unsigned *out)
+{
+	int ret;
+
+	ret = ida_simple_get(&dev_priv->context_hw_ida,
+			     0, MAX_CONTEXT_HW_ID, GFP_KERNEL);
+	if (ret < 0) {
+		/* Contexts are only released when no longer active.
+		 * Flush any pending retires to hopefully release some
+		 * stale contexts and try again.
+		 */
+		i915_gem_retire_requests(dev_priv->dev);
+		ret = ida_simple_get(&dev_priv->context_hw_ida,
+				     0, MAX_CONTEXT_HW_ID, GFP_KERNEL);
+		if (ret < 0)
+			return ret;
+	}
+
+	*out = ret;
+	return 0;
+}
+
 static struct intel_context *
 __create_hw_context(struct drm_device *dev,
 		    struct drm_i915_file_private *file_priv)
@@ -225,6 +249,12 @@ __create_hw_context(struct drm_device *dev,
 	list_add_tail(&ctx->link, &dev_priv->context_list);
 	ctx->i915 = dev_priv;
 
+	ret = assign_hw_id(dev_priv, &ctx->hw_id);
+	if (ret) {
+		kfree(ctx);
+		return ERR_PTR(ret);
+	}
+
 	if (dev_priv->hw_context_size) {
 		struct drm_i915_gem_object *obj =
 				i915_gem_alloc_context_obj(dev, dev_priv->hw_context_size);
@@ -375,6 +405,8 @@ int i915_gem_context_init(struct drm_device *dev)
 		}
 	}
 
+	ida_init(&dev_priv->context_hw_ida);
+
 	if (i915.enable_execlists) {
 		/* NB: intentionally left blank. We will allocate our own
 		 * backing objects as we need them, thank you very much */
-- 
2.8.0.rc3