[RFC 1/8] drm/i915: Introduce global id for contexts

[sourab.gupta@intel.com]

From: Sourab Gupta <sourab.gupta@intel.com>

The current context user handles are specific to drm file instance.
There are some usecases, which may require a global id for the contexts.
For e.g. a system level GPU profiler tool may lean upon the global context
ids to associate the performance snapshots with individual contexts.

This global id may also be used further in order to provide a unique
context id to hw.

In this patch, the global ids are allocated from a separate cyclic idr and
can be further utilized for any usecase described above.

v2: According to Chris' suggestion, implemented a separate idr for holding
global ids for contexts, as opposed to overloading the file specific
ctx->user_handle for this purpose. This global id can also further be used
wherever hw has to be programmed with ctx unique id, though this patch just
introduces the hw global id as such.

Signed-off-by: Sourab Gupta <sourab.gupta@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h         |  3 +++
 drivers/gpu/drm/i915/i915_gem_context.c | 19 +++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 50977f0..3436f3b 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -861,6 +861,7 @@ struct i915_ctx_hang_stats {
 struct intel_context {
 	struct kref ref;
 	int user_handle;
+	int global_id;
 	uint8_t remap_slice;
 	int flags;
 	struct drm_i915_file_private *file_priv;
@@ -1756,6 +1757,8 @@ struct drm_i915_private {
 
 	bool preserve_bios_swizzle;
 
+	struct idr global_ctx_idr;
+
 	/* overlay */
 	struct intel_overlay *overlay;
 
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index d9ccad5..51ec420 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -246,6 +246,18 @@ __create_hw_context(struct drm_device *dev,
 
 	ctx->file_priv = file_priv;
 	ctx->user_handle = ret;
+
+	/* TODO: If required, this global id can be used for programming the hw
+	 * fields too. In that case, we'll have take care of hw restrictions
+	 * while allocating idr. e.g. for some hw, we may not have full 32 bits
+	 * available.
+	 */
+	ret = idr_alloc_cyclic(&dev_priv->global_ctx_idr,
+				ctx, 0, 0, GFP_KERNEL);
+	if (ret < 0)
+		goto err_out;
+
+	ctx->global_id = ret;
 	/* NB: Mark all slices as needing a remap so that when the context first
 	 * loads it will restore whatever remap state already exists. If there
 	 * is no remap info, it will be a NOP. */
@@ -270,6 +282,7 @@ i915_gem_create_context(struct drm_device *dev,
 			struct drm_i915_file_private *file_priv)
 {
 	const bool is_global_default_ctx = file_priv == NULL;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_context *ctx;
 	int ret = 0;
 
@@ -315,6 +328,7 @@ err_unpin:
 	if (is_global_default_ctx && ctx->legacy_hw_ctx.rcs_state)
 		i915_gem_context_unpin_state(dev, ctx);
 err_destroy:
+	idr_remove(&dev_priv->global_ctx_idr, ctx->global_id);
 	i915_gem_context_unreference(ctx);
 	return ERR_PTR(ret);
 }
@@ -371,6 +385,7 @@ int i915_gem_context_init(struct drm_device *dev)
 			dev_priv->hw_context_size = 0;
 		}
 	}
+	idr_init(&dev_priv->global_ctx_idr);
 
 	ctx = i915_gem_create_context(dev, NULL);
 	if (IS_ERR(ctx)) {
@@ -398,6 +413,8 @@ void i915_gem_context_fini(struct drm_device *dev)
 	struct intel_context *dctx = dev_priv->ring[RCS].default_context;
 	int i;
 
+	idr_destroy(&dev_priv->global_ctx_idr);
+
 	if (dctx->legacy_hw_ctx.rcs_state) {
 		/* The only known way to stop the gpu from accessing the hw context is
 		 * to reset it. Do this as the very last operation to avoid confusing
@@ -878,6 +895,7 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
 {
 	struct drm_i915_gem_context_destroy *args = data;
 	struct drm_i915_file_private *file_priv = file->driver_priv;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_context *ctx;
 	int ret;
 
@@ -895,6 +913,7 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
 	}
 
 	idr_remove(&ctx->file_priv->context_idr, ctx->user_handle);
+	idr_remove(&dev_priv->global_ctx_idr, ctx->global_id);
 	i915_gem_context_unreference(ctx);
 	mutex_unlock(&dev->struct_mutex);
 
-- 
1.8.5.1

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