drm/panfrost: Add the panfrost_gem_mapping concept

With the introduction of per-FD address space, the same BO can be mapped
in different address space if the BO is globally visible (GEM_FLINK)
and opened in different context or if the dmabuf is self-imported. The
current implementation does not take case into account, and attaches the
mapping directly to the panfrost_gem_object.

Let's create a panfrost_gem_mapping struct and allow multiple mappings
per BO.

The mappings are refcounted which helps solve another problem where
mappings were torn down (GEM handle closed by userspace) while GPU
jobs accessing those BOs were still in-flight. Jobs now keep a
reference on the mappings they use.

v2 (robh):
- Minor review comment clean-ups from Steven
- Use list_is_singular helper
- Just WARN if we add a mapping when madvise state is not WILLNEED.
  With that, drop the use of object_name_lock.

v3 (robh):
- Revert returning list iterator in panfrost_gem_mapping_get()

Fixes: a5efb4c9a562 ("drm/panfrost: Restructure the GEM object creation")
Fixes: 7282f7645d06 ("drm/panfrost: Implement per FD address spaces")
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200116021554.15090-1-robh@kernel.org

1 files changed, 108 insertions, 16 deletions

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
index fd766b1395fb..17b654e1eb94 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
@@ -29,6 +29,12 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
 	list_del_init(&bo->base.madv_list);
 	mutex_unlock(&pfdev->shrinker_lock);
 
+	/*
+	 * If we still have mappings attached to the BO, there's a problem in
+	 * our refcounting.
+	 */
+	WARN_ON_ONCE(!list_empty(&bo->mappings.list));
+
 	if (bo->sgts) {
 		int i;
 		int n_sgt = bo->base.base.size / SZ_2M;
@@ -46,6 +52,69 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
 	drm_gem_shmem_free_object(obj);
 }
 
+struct panfrost_gem_mapping *
+panfrost_gem_mapping_get(struct panfrost_gem_object *bo,
+			 struct panfrost_file_priv *priv)
+{
+	struct panfrost_gem_mapping *iter, *mapping = NULL;
+
+	mutex_lock(&bo->mappings.lock);
+	list_for_each_entry(iter, &bo->mappings.list, node) {
+		if (iter->mmu == &priv->mmu) {
+			kref_get(&iter->refcount);
+			mapping = iter;
+			break;
+		}
+	}
+	mutex_unlock(&bo->mappings.lock);
+
+	return mapping;
+}
+
+static void
+panfrost_gem_teardown_mapping(struct panfrost_gem_mapping *mapping)
+{
+	struct panfrost_file_priv *priv;
+
+	if (mapping->active)
+		panfrost_mmu_unmap(mapping);
+
+	priv = container_of(mapping->mmu, struct panfrost_file_priv, mmu);
+	spin_lock(&priv->mm_lock);
+	if (drm_mm_node_allocated(&mapping->mmnode))
+		drm_mm_remove_node(&mapping->mmnode);
+	spin_unlock(&priv->mm_lock);
+}
+
+static void panfrost_gem_mapping_release(struct kref *kref)
+{
+	struct panfrost_gem_mapping *mapping;
+
+	mapping = container_of(kref, struct panfrost_gem_mapping, refcount);
+
+	panfrost_gem_teardown_mapping(mapping);
+	drm_gem_object_put_unlocked(&mapping->obj->base.base);
+	kfree(mapping);
+}
+
+void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping)
+{
+	if (!mapping)
+		return;
+
+	kref_put(&mapping->refcount, panfrost_gem_mapping_release);
+}
+
+void panfrost_gem_teardown_mappings(struct panfrost_gem_object *bo)
+{
+	struct panfrost_gem_mapping *mapping;
+
+	mutex_lock(&bo->mappings.lock);
+	list_for_each_entry(mapping, &bo->mappings.list, node)
+		panfrost_gem_teardown_mapping(mapping);
+	mutex_unlock(&bo->mappings.lock);
+}
+
 int panfrost_gem_open(struct drm_gem_object *obj, struct drm_file *file_priv)
 {
 	int ret;
@@ -54,6 +123,16 @@ int panfrost_gem_open(struct drm_gem_object *obj, struct drm_file *file_priv)
 	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
 	unsigned long color = bo->noexec ? PANFROST_BO_NOEXEC : 0;
 	struct panfrost_file_priv *priv = file_priv->driver_priv;
+	struct panfrost_gem_mapping *mapping;
+
+	mapping = kzalloc(sizeof(*mapping), GFP_KERNEL);
+	if (!mapping)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&mapping->node);
+	kref_init(&mapping->refcount);
+	drm_gem_object_get(obj);
+	mapping->obj = bo;
 
 	/*
 	 * Executable buffers cannot cross a 16MB boundary as the program
@@ -66,37 +145,48 @@ int panfrost_gem_open(struct drm_gem_object *obj, struct drm_file *file_priv)
 	else
 		align = size >= SZ_2M ? SZ_2M >> PAGE_SHIFT : 0;
 
-	bo->mmu = &priv->mmu;
+	mapping->mmu = &priv->mmu;
 	spin_lock(&priv->mm_lock);
-	ret = drm_mm_insert_node_generic(&priv->mm, &bo->node,
+	ret = drm_mm_insert_node_generic(&priv->mm, &mapping->mmnode,
 					 size >> PAGE_SHIFT, align, color, 0);
 	spin_unlock(&priv->mm_lock);
 	if (ret)
-		return ret;
+		goto err;
 
 	if (!bo->is_heap) {
-		ret = panfrost_mmu_map(bo);
-		if (ret) {
-			spin_lock(&priv->mm_lock);
-			drm_mm_remove_node(&bo->node);
-			spin_unlock(&priv->mm_lock);
-		}
+		ret = panfrost_mmu_map(mapping);
+		if (ret)
+			goto err;
 	}
+
+	mutex_lock(&bo->mappings.lock);
+	WARN_ON(bo->base.madv != PANFROST_MADV_WILLNEED);
+	list_add_tail(&mapping->node, &bo->mappings.list);
+	mutex_unlock(&bo->mappings.lock);
+
+err:
+	if (ret)
+		panfrost_gem_mapping_put(mapping);
 	return ret;
 }
 
 void panfrost_gem_close(struct drm_gem_object *obj, struct drm_file *file_priv)
 {
-	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
 	struct panfrost_file_priv *priv = file_priv->driver_priv;
+	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
+	struct panfrost_gem_mapping *mapping = NULL, *iter;
 
-	if (bo->is_mapped)
-		panfrost_mmu_unmap(bo);
+	mutex_lock(&bo->mappings.lock);
+	list_for_each_entry(iter, &bo->mappings.list, node) {
+		if (iter->mmu == &priv->mmu) {
+			mapping = iter;
+			list_del(&iter->node);
+			break;
+		}
+	}
+	mutex_unlock(&bo->mappings.lock);
 
-	spin_lock(&priv->mm_lock);
-	if (drm_mm_node_allocated(&bo->node))
-		drm_mm_remove_node(&bo->node);
-	spin_unlock(&priv->mm_lock);
+	panfrost_gem_mapping_put(mapping);
 }
 
 static int panfrost_gem_pin(struct drm_gem_object *obj)
@@ -136,6 +226,8 @@ struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t
 	if (!obj)
 		return NULL;
 
+	INIT_LIST_HEAD(&obj->mappings.list);
+	mutex_init(&obj->mappings.lock);
 	obj->base.base.funcs = &panfrost_gem_funcs;
 
 	return &obj->base.base;