drm: add unified vma offset manager

If we want to map GPU memory into user-space, we need to linearize the
addresses to not confuse mm-core. Currently, GEM and TTM both implement
their own offset-managers to assign a pgoff to each object for user-space
CPU access. GEM uses a hash-table, TTM uses an rbtree.

This patch provides a unified implementation that can be used to replace
both. TTM allows partial mmaps with a given offset, so we cannot use
hashtables as the start address may not be known at mmap time. Hence, we
use the rbtree-implementation of TTM.

We could easily update drm_mm to use an rbtree instead of a linked list
for it's object list and thus drop the rbtree from the vma-manager.
However, this would slow down drm_mm object allocation for all other
use-cases (rbtree insertion) and add another 4-8 bytes to each mm node.
Hence, use the separate tree but allow for later migration.

This is a rewrite of the 2012-proposal by David Airlie <airlied@linux.ie>

v2:
 - fix Docbook integration
 - drop drm_mm_node_linked() and use drm_mm_node_allocated()
 - remove unjustified likely/unlikely usage (but keep for rbtree paths)
 - remove BUG_ON() as drm_mm already does that
 - clarify page-based vs. byte-based addresses
 - use drm_vma_node_reset() for initialization, too
v4:
 - allow external locking via drm_vma_offset_un/lock_lookup()
 - add locked lookup helper drm_vma_offset_lookup_locked()
v5:
 - fix drm_vma_offset_lookup() to correctly validate range-mismatches
   (fix (offset > start + pages))
 - fix drm_vma_offset_exact_lookup() to actually do what it says
 - remove redundant vm_pages member (add drm_vma_node_size() helper)
 - remove unneeded goto
 - fix documentation

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@gmail.com>

1 files changed, 202 insertions, 0 deletions

diff --git a/include/drm/drm_vma_manager.h b/include/drm/drm_vma_manager.h
new file mode 100644
index 000000000000..7ee8c4babeb9
--- /dev/null
+++ b/include/drm/drm_vma_manager.h
@@ -0,0 +1,202 @@
+#ifndef __DRM_VMA_MANAGER_H__
+#define __DRM_VMA_MANAGER_H__
+
+/*
+ * Copyright (c) 2013 David Herrmann <dh.herrmann@gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <drm/drm_mm.h>
+#include <linux/module.h>
+#include <linux/rbtree.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+struct drm_vma_offset_node {
+	struct drm_mm_node vm_node;
+	struct rb_node vm_rb;
+};
+
+struct drm_vma_offset_manager {
+	rwlock_t vm_lock;
+	struct rb_root vm_addr_space_rb;
+	struct drm_mm vm_addr_space_mm;
+};
+
+void drm_vma_offset_manager_init(struct drm_vma_offset_manager *mgr,
+				 unsigned long page_offset, unsigned long size);
+void drm_vma_offset_manager_destroy(struct drm_vma_offset_manager *mgr);
+
+struct drm_vma_offset_node *drm_vma_offset_lookup(struct drm_vma_offset_manager *mgr,
+						  unsigned long start,
+						  unsigned long pages);
+struct drm_vma_offset_node *drm_vma_offset_lookup_locked(struct drm_vma_offset_manager *mgr,
+							   unsigned long start,
+							   unsigned long pages);
+int drm_vma_offset_add(struct drm_vma_offset_manager *mgr,
+		       struct drm_vma_offset_node *node, unsigned long pages);
+void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
+			   struct drm_vma_offset_node *node);
+
+/**
+ * drm_vma_offset_exact_lookup() - Look up node by exact address
+ * @mgr: Manager object
+ * @start: Start address (page-based, not byte-based)
+ * @pages: Size of object (page-based)
+ *
+ * Same as drm_vma_offset_lookup() but does not allow any offset into the node.
+ * It only returns the exact object with the given start address.
+ *
+ * RETURNS:
+ * Node at exact start address @start.
+ */
+static inline struct drm_vma_offset_node *
+drm_vma_offset_exact_lookup(struct drm_vma_offset_manager *mgr,
+			    unsigned long start,
+			    unsigned long pages)
+{
+	struct drm_vma_offset_node *node;
+
+	node = drm_vma_offset_lookup(mgr, start, pages);
+	return (node && node->vm_node.start == start) ? node : NULL;
+}
+
+/**
+ * drm_vma_offset_lock_lookup() - Lock lookup for extended private use
+ * @mgr: Manager object
+ *
+ * Lock VMA manager for extended lookups. Only *_locked() VMA function calls
+ * are allowed while holding this lock. All other contexts are blocked from VMA
+ * until the lock is released via drm_vma_offset_unlock_lookup().
+ *
+ * Use this if you need to take a reference to the objects returned by
+ * drm_vma_offset_lookup_locked() before releasing this lock again.
+ *
+ * This lock must not be used for anything else than extended lookups. You must
+ * not call any other VMA helpers while holding this lock.
+ *
+ * Note: You're in atomic-context while holding this lock!
+ *
+ * Example:
+ *   drm_vma_offset_lock_lookup(mgr);
+ *   node = drm_vma_offset_lookup_locked(mgr);
+ *   if (node)
+ *       kref_get_unless_zero(container_of(node, sth, entr));
+ *   drm_vma_offset_unlock_lookup(mgr);
+ */
+static inline void drm_vma_offset_lock_lookup(struct drm_vma_offset_manager *mgr)
+{
+	read_lock(&mgr->vm_lock);
+}
+
+/**
+ * drm_vma_offset_unlock_lookup() - Unlock lookup for extended private use
+ * @mgr: Manager object
+ *
+ * Release lookup-lock. See drm_vma_offset_lock_lookup() for more information.
+ */
+static inline void drm_vma_offset_unlock_lookup(struct drm_vma_offset_manager *mgr)
+{
+	read_unlock(&mgr->vm_lock);
+}
+
+/**
+ * drm_vma_node_reset() - Initialize or reset node object
+ * @node: Node to initialize or reset
+ *
+ * Reset a node to its initial state. This must be called if @node isn't
+ * already cleared (eg., via kzalloc) before using it with any VMA offset
+ * manager.
+ *
+ * This must not be called on an already allocated node, or you will leak
+ * memory.
+ */
+static inline void drm_vma_node_reset(struct drm_vma_offset_node *node)
+{
+	memset(node, 0, sizeof(*node));
+}
+
+/**
+ * drm_vma_node_start() - Return start address for page-based addressing
+ * @node: Node to inspect
+ *
+ * Return the start address of the given node. This can be used as offset into
+ * the linear VM space that is provided by the VMA offset manager. Note that
+ * this can only be used for page-based addressing. If you need a proper offset
+ * for user-space mappings, you must apply "<< PAGE_SHIFT" or use the
+ * drm_vma_node_offset_addr() helper instead.
+ *
+ * RETURNS:
+ * Start address of @node for page-based addressing. 0 if the node does not
+ * have an offset allocated.
+ */
+static inline unsigned long drm_vma_node_start(struct drm_vma_offset_node *node)
+{
+	return node->vm_node.start;
+}
+
+/**
+ * drm_vma_node_size() - Return size (page-based)
+ * @node: Node to inspect
+ *
+ * Return the size as number of pages for the given node. This is the same size
+ * that was passed to drm_vma_offset_add(). If no offset is allocated for the
+ * node, this is 0.
+ *
+ * RETURNS:
+ * Size of @node as number of pages. 0 if the node does not have an offset
+ * allocated.
+ */
+static inline unsigned long drm_vma_node_size(struct drm_vma_offset_node *node)
+{
+	return node->vm_node.size;
+}
+
+/**
+ * drm_vma_node_has_offset() - Check whether node is added to offset manager
+ * @node: Node to be checked
+ *
+ * RETURNS:
+ * true iff the node was previously allocated an offset and added to
+ * an vma offset manager.
+ */
+static inline bool drm_vma_node_has_offset(struct drm_vma_offset_node *node)
+{
+	return drm_mm_node_allocated(&node->vm_node);
+}
+
+/**
+ * drm_vma_node_offset_addr() - Return sanitized offset for user-space mmaps
+ * @node: Linked offset node
+ *
+ * Same as drm_vma_node_start() but returns the address as a valid offset that
+ * can be used for user-space mappings during mmap().
+ * This must not be called on unlinked nodes.
+ *
+ * RETURNS:
+ * Offset of @node for byte-based addressing. 0 if the node does not have an
+ * object allocated.
+ */
+static inline __u64 drm_vma_node_offset_addr(struct drm_vma_offset_node *node)
+{
+	return ((__u64)node->vm_node.start) << PAGE_SHIFT;
+}
+
+#endif /* __DRM_VMA_MANAGER_H__ */