[Intel-gfx] [PATCH v2, 1/4] drm/i915: remove intel_context::file_priv, add flag for default context

[Dave Gordon]

The file_priv member was used in only one place, where we already had
the file_priv and therefore didn't need to derive it from the context
(in fact, we just found the context by reference to the file_priv).
So by fixing up that one use, we can drop file_priv entirely.

OTOH sometimes we need to identify the global (default) context, which
belongs to the driver as whole and is not associated with any user file
descriptor, so here we add a flag for that specific purpose. This will
then be used instead of the current unsafe practice of check each engine
to see whether its default_context pointer refers back to the context
being operated on. In a subsequent patch, these backpointers will go
away too :)

Signed-off-by: Dave Gordon <david.s.gordon at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h         |  3 ++-
 drivers/gpu/drm/i915/i915_gem_context.c | 22 ++++++++++++----------
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 9b82c45..4fb15f5 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -854,6 +854,7 @@ struct i915_ctx_hang_stats {
  * @ref: reference count.
  * @user_handle: userspace tracking identity for this context.
  * @remap_slice: l3 row remapping information.
+ * @is_default: true iff this is the global default context
  * @flags: context specific flags:
  *         CONTEXT_NO_ZEROMAP: do not allow mapping things to page 0.
  * @file_priv: filp associated with this context (NULL for global default
@@ -872,9 +873,9 @@ struct intel_context {
 	struct kref ref;
 	int user_handle;
 	uint8_t remap_slice;
+	uint8_t is_global_default;
 	struct drm_i915_private *i915;
 	int flags;
-	struct drm_i915_file_private *file_priv;
 	struct i915_ctx_hang_stats hang_stats;
 	struct i915_hw_ppgtt *ppgtt;
 
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 900ffd0..43437af 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -236,16 +236,17 @@ __create_hw_context(struct drm_device *dev,
 	}
 
 	/* Default context will never have a file_priv */
-	if (file_priv != NULL) {
+	if (file_priv == NULL) {
+		ctx->is_global_default = true;
+		ret = DEFAULT_CONTEXT_HANDLE;
+	} else {
 		ret = idr_alloc(&file_priv->context_idr, ctx,
 				DEFAULT_CONTEXT_HANDLE, 0, GFP_KERNEL);
 		if (ret < 0)
 			goto err_out;
-	} else
-		ret = DEFAULT_CONTEXT_HANDLE;
-
-	ctx->file_priv = file_priv;
+	}
 	ctx->user_handle = 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. */
@@ -269,7 +270,6 @@ static struct intel_context *
 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 intel_context *ctx;
 	int ret = 0;
 
@@ -279,8 +279,9 @@ i915_gem_create_context(struct drm_device *dev,
 	if (IS_ERR(ctx))
 		return ctx;
 
-	if (is_global_default_ctx && ctx->legacy_hw_ctx.rcs_state) {
-		/* We may need to do things with the shrinker which
+	if (ctx->is_global_default && ctx->legacy_hw_ctx.rcs_state) {
+		/*
+		 * We may need to do things with the shrinker which
 		 * require us to immediately switch back to the default
 		 * context. This can cause a problem as pinning the
 		 * default context also requires GTT space which may not
@@ -313,7 +314,7 @@ i915_gem_create_context(struct drm_device *dev,
 	return ctx;
 
 err_unpin:
-	if (is_global_default_ctx && ctx->legacy_hw_ctx.rcs_state)
+	if (ctx->is_global_default && ctx->legacy_hw_ctx.rcs_state)
 		i915_gem_object_ggtt_unpin(ctx->legacy_hw_ctx.rcs_state);
 err_destroy:
 	idr_remove(&file_priv->context_idr, ctx->user_handle);
@@ -381,6 +382,7 @@ int i915_gem_context_init(struct drm_device *dev)
 		}
 	}
 
+	/* NULL second parameter indicates this is the global default context */
 	ctx = i915_gem_create_context(dev, NULL);
 	if (IS_ERR(ctx)) {
 		DRM_ERROR("Failed to create default global context (error %ld)\n",
@@ -896,7 +898,7 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
 		return PTR_ERR(ctx);
 	}
 
-	idr_remove(&ctx->file_priv->context_idr, ctx->user_handle);
+	idr_remove(&file_priv->context_idr, ctx->user_handle);
 	i915_gem_context_unreference(ctx);
 	mutex_unlock(&dev->struct_mutex);
 
-- 
1.9.1