drm_vma_manager.c

  1// SPDX-License-Identifier: GPL-2.0 OR MIT
  2/*
  3 * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
  4 * Copyright (c) 2012 David Airlie <airlied@linux.ie>
  5 * Copyright (c) 2013 David Herrmann <dh.herrmann@gmail.com>
  6 *
  7 * Permission is hereby granted, free of charge, to any person obtaining a
  8 * copy of this software and associated documentation files (the "Software"),
  9 * to deal in the Software without restriction, including without limitation
 10 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 11 * and/or sell copies of the Software, and to permit persons to whom the
 12 * Software is furnished to do so, subject to the following conditions:
 13 *
 14 * The above copyright notice and this permission notice shall be included in
 15 * all copies or substantial portions of the Software.
 16 *
 17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 20 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 21 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 22 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 23 * OTHER DEALINGS IN THE SOFTWARE.
 24 */
 25
 26#include <linux/export.h>
 27#include <linux/mm.h>
 28#include <linux/module.h>
 29#include <linux/rbtree.h>
 30#include <linux/slab.h>
 31#include <linux/spinlock.h>
 32#include <linux/types.h>
 33
 34#include <drm/drm_mm.h>
 35#include <drm/drm_vma_manager.h>
 36
 37/**
 38 * DOC: vma offset manager
 39 *
 40 * The vma-manager is responsible to map arbitrary driver-dependent memory
 41 * regions into the linear user address-space. It provides offsets to the
 42 * caller which can then be used on the address_space of the drm-device. It
 43 * takes care to not overlap regions, size them appropriately and to not
 44 * confuse mm-core by inconsistent fake vm_pgoff fields.
 45 * Drivers shouldn't use this for object placement in VMEM. This manager should
 46 * only be used to manage mappings into linear user-space VMs.
 47 *
 48 * We use drm_mm as backend to manage object allocations. But it is highly
 49 * optimized for alloc/free calls, not lookups. Hence, we use an rb-tree to
 50 * speed up offset lookups.
 51 *
 52 * You must not use multiple offset managers on a single address_space.
 53 * Otherwise, mm-core will be unable to tear down memory mappings as the VM will
 54 * no longer be linear.
 55 *
 56 * This offset manager works on page-based addresses. That is, every argument
 57 * and return code (with the exception of drm_vma_node_offset_addr()) is given
 58 * in number of pages, not number of bytes. That means, object sizes and offsets
 59 * must always be page-aligned (as usual).
 60 * If you want to get a valid byte-based user-space address for a given offset,
 61 * please see drm_vma_node_offset_addr().
 62 *
 63 * Additionally to offset management, the vma offset manager also handles access
 64 * management. For every open-file context that is allowed to access a given
 65 * node, you must call drm_vma_node_allow(). Otherwise, an mmap() call on this
 66 * open-file with the offset of the node will fail with -EACCES. To revoke
 67 * access again, use drm_vma_node_revoke(). However, the caller is responsible
 68 * for destroying already existing mappings, if required.
 69 */
 70
 71/**
 72 * drm_vma_offset_manager_init - Initialize new offset-manager
 73 * @mgr: Manager object
 74 * @page_offset: Offset of available memory area (page-based)
 75 * @size: Size of available address space range (page-based)
 76 *
 77 * Initialize a new offset-manager. The offset and area size available for the
 78 * manager are given as @page_offset and @size. Both are interpreted as
 79 * page-numbers, not bytes.
 80 *
 81 * Adding/removing nodes from the manager is locked internally and protected
 82 * against concurrent access. However, node allocation and destruction is left
 83 * for the caller. While calling into the vma-manager, a given node must
 84 * always be guaranteed to be referenced.
 85 */
 86void drm_vma_offset_manager_init(struct drm_vma_offset_manager *mgr,
 87				 unsigned long page_offset, unsigned long size)
 88{
 89	rwlock_init(&mgr->vm_lock);
 90	drm_mm_init(&mgr->vm_addr_space_mm, page_offset, size);
 91}
 92EXPORT_SYMBOL(drm_vma_offset_manager_init);
 93
 94/**
 95 * drm_vma_offset_manager_destroy() - Destroy offset manager
 96 * @mgr: Manager object
 97 *
 98 * Destroy an object manager which was previously created via
 99 * drm_vma_offset_manager_init(). The caller must remove all allocated nodes
100 * before destroying the manager. Otherwise, drm_mm will refuse to free the
101 * requested resources.
102 *
103 * The manager must not be accessed after this function is called.
104 */
105void drm_vma_offset_manager_destroy(struct drm_vma_offset_manager *mgr)
106{
107	drm_mm_takedown(&mgr->vm_addr_space_mm);
108}
109EXPORT_SYMBOL(drm_vma_offset_manager_destroy);
110
111/**
112 * drm_vma_offset_lookup_locked() - Find node in offset space
113 * @mgr: Manager object
114 * @start: Start address for object (page-based)
115 * @pages: Size of object (page-based)
116 *
117 * Find a node given a start address and object size. This returns the _best_
118 * match for the given node. That is, @start may point somewhere into a valid
119 * region and the given node will be returned, as long as the node spans the
120 * whole requested area (given the size in number of pages as @pages).
121 *
122 * Note that before lookup the vma offset manager lookup lock must be acquired
123 * with drm_vma_offset_lock_lookup(). See there for an example. This can then be
124 * used to implement weakly referenced lookups using kref_get_unless_zero().
125 *
126 * Example:
127 *
128 * ::
129 *
130 *     drm_vma_offset_lock_lookup(mgr);
131 *     node = drm_vma_offset_lookup_locked(mgr);
132 *     if (node)
133 *         kref_get_unless_zero(container_of(node, sth, entr));
134 *     drm_vma_offset_unlock_lookup(mgr);
135 *
136 * RETURNS:
137 * Returns NULL if no suitable node can be found. Otherwise, the best match
138 * is returned. It's the caller's responsibility to make sure the node doesn't
139 * get destroyed before the caller can access it.
140 */
141struct drm_vma_offset_node *drm_vma_offset_lookup_locked(struct drm_vma_offset_manager *mgr,
142							 unsigned long start,
143							 unsigned long pages)
144{
145	struct drm_mm_node *node, *best;
146	struct rb_node *iter;
147	unsigned long offset;
148
149	iter = mgr->vm_addr_space_mm.interval_tree.rb_root.rb_node;
150	best = NULL;
151
152	while (likely(iter)) {
153		node = rb_entry(iter, struct drm_mm_node, rb);
154		offset = node->start;
155		if (start >= offset) {
156			iter = iter->rb_right;
157			best = node;
158			if (start == offset)
159				break;
160		} else {
161			iter = iter->rb_left;
162		}
163	}
164
165	/* verify that the node spans the requested area */
166	if (best) {
167		offset = best->start + best->size;
168		if (offset < start + pages)
169			best = NULL;
170	}
171
172	if (!best)
173		return NULL;
174
175	return container_of(best, struct drm_vma_offset_node, vm_node);
176}
177EXPORT_SYMBOL(drm_vma_offset_lookup_locked);
178
179/**
180 * drm_vma_offset_add() - Add offset node to manager
181 * @mgr: Manager object
182 * @node: Node to be added
183 * @pages: Allocation size visible to user-space (in number of pages)
184 *
185 * Add a node to the offset-manager. If the node was already added, this does
186 * nothing and return 0. @pages is the size of the object given in number of
187 * pages.
188 * After this call succeeds, you can access the offset of the node until it
189 * is removed again.
190 *
191 * If this call fails, it is safe to retry the operation or call
192 * drm_vma_offset_remove(), anyway. However, no cleanup is required in that
193 * case.
194 *
195 * @pages is not required to be the same size as the underlying memory object
196 * that you want to map. It only limits the size that user-space can map into
197 * their address space.
198 *
199 * RETURNS:
200 * 0 on success, negative error code on failure.
201 */
202int drm_vma_offset_add(struct drm_vma_offset_manager *mgr,
203		       struct drm_vma_offset_node *node, unsigned long pages)
204{
205	int ret = 0;
206
207	write_lock(&mgr->vm_lock);
208
209	if (!drm_mm_node_allocated(&node->vm_node))
210		ret = drm_mm_insert_node(&mgr->vm_addr_space_mm,
211					 &node->vm_node, pages);
212
213	write_unlock(&mgr->vm_lock);
214
215	return ret;
216}
217EXPORT_SYMBOL(drm_vma_offset_add);
218
219/**
220 * drm_vma_offset_remove() - Remove offset node from manager
221 * @mgr: Manager object
222 * @node: Node to be removed
223 *
224 * Remove a node from the offset manager. If the node wasn't added before, this
225 * does nothing. After this call returns, the offset and size will be 0 until a
226 * new offset is allocated via drm_vma_offset_add() again. Helper functions like
227 * drm_vma_node_start() and drm_vma_node_offset_addr() will return 0 if no
228 * offset is allocated.
229 */
230void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
231			   struct drm_vma_offset_node *node)
232{
233	write_lock(&mgr->vm_lock);
234
235	if (drm_mm_node_allocated(&node->vm_node)) {
236		drm_mm_remove_node(&node->vm_node);
237		memset(&node->vm_node, 0, sizeof(node->vm_node));
238	}
239
240	write_unlock(&mgr->vm_lock);
241}
242EXPORT_SYMBOL(drm_vma_offset_remove);
243
244static int vma_node_allow(struct drm_vma_offset_node *node,
245			  struct drm_file *tag, bool ref_counted)
246{
247	struct rb_node **iter;
248	struct rb_node *parent = NULL;
249	struct drm_vma_offset_file *new, *entry;
250	int ret = 0;
251
252	/* Preallocate entry to avoid atomic allocations below. It is quite
253	 * unlikely that an open-file is added twice to a single node so we
254	 * don't optimize for this case. OOM is checked below only if the entry
255	 * is actually used. */
256	new = kmalloc(sizeof(*entry), GFP_KERNEL);
257
258	write_lock(&node->vm_lock);
259
260	iter = &node->vm_files.rb_node;
261
262	while (likely(*iter)) {
263		parent = *iter;
264		entry = rb_entry(*iter, struct drm_vma_offset_file, vm_rb);
265
266		if (tag == entry->vm_tag) {
267			if (ref_counted)
268				entry->vm_count++;
269			goto unlock;
270		} else if (tag > entry->vm_tag) {
271			iter = &(*iter)->rb_right;
272		} else {
273			iter = &(*iter)->rb_left;
274		}
275	}
276
277	if (!new) {
278		ret = -ENOMEM;
279		goto unlock;
280	}
281
282	new->vm_tag = tag;
283	new->vm_count = 1;
284	rb_link_node(&new->vm_rb, parent, iter);
285	rb_insert_color(&new->vm_rb, &node->vm_files);
286	new = NULL;
287
288unlock:
289	write_unlock(&node->vm_lock);
290	kfree(new);
291	return ret;
292}
293
294/**
295 * drm_vma_node_allow - Add open-file to list of allowed users
296 * @node: Node to modify
297 * @tag: Tag of file to remove
298 *
299 * Add @tag to the list of allowed open-files for this node. If @tag is
300 * already on this list, the ref-count is incremented.
301 *
302 * The list of allowed-users is preserved across drm_vma_offset_add() and
303 * drm_vma_offset_remove() calls. You may even call it if the node is currently
304 * not added to any offset-manager.
305 *
306 * You must remove all open-files the same number of times as you added them
307 * before destroying the node. Otherwise, you will leak memory.
308 *
309 * This is locked against concurrent access internally.
310 *
311 * RETURNS:
312 * 0 on success, negative error code on internal failure (out-of-mem)
313 */
314int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag)
315{
316	return vma_node_allow(node, tag, true);
317}
318EXPORT_SYMBOL(drm_vma_node_allow);
319
320/**
321 * drm_vma_node_allow_once - Add open-file to list of allowed users
322 * @node: Node to modify
323 * @tag: Tag of file to remove
324 *
325 * Add @tag to the list of allowed open-files for this node.
326 *
327 * The list of allowed-users is preserved across drm_vma_offset_add() and
328 * drm_vma_offset_remove() calls. You may even call it if the node is currently
329 * not added to any offset-manager.
330 *
331 * This is not ref-counted unlike drm_vma_node_allow() hence drm_vma_node_revoke()
332 * should only be called once after this.
333 *
334 * This is locked against concurrent access internally.
335 *
336 * RETURNS:
337 * 0 on success, negative error code on internal failure (out-of-mem)
338 */
339int drm_vma_node_allow_once(struct drm_vma_offset_node *node, struct drm_file *tag)
340{
341	return vma_node_allow(node, tag, false);
342}
343EXPORT_SYMBOL(drm_vma_node_allow_once);
344
345/**
346 * drm_vma_node_revoke - Remove open-file from list of allowed users
347 * @node: Node to modify
348 * @tag: Tag of file to remove
349 *
350 * Decrement the ref-count of @tag in the list of allowed open-files on @node.
351 * If the ref-count drops to zero, remove @tag from the list. You must call
352 * this once for every drm_vma_node_allow() on @tag.
353 *
354 * This is locked against concurrent access internally.
355 *
356 * If @tag is not on the list, nothing is done.
357 */
358void drm_vma_node_revoke(struct drm_vma_offset_node *node,
359			 struct drm_file *tag)
360{
361	struct drm_vma_offset_file *entry;
362	struct rb_node *iter;
363
364	write_lock(&node->vm_lock);
365
366	iter = node->vm_files.rb_node;
367	while (likely(iter)) {
368		entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
369		if (tag == entry->vm_tag) {
370			if (!--entry->vm_count) {
371				rb_erase(&entry->vm_rb, &node->vm_files);
372				kfree(entry);
373			}
374			break;
375		} else if (tag > entry->vm_tag) {
376			iter = iter->rb_right;
377		} else {
378			iter = iter->rb_left;
379		}
380	}
381
382	write_unlock(&node->vm_lock);
383}
384EXPORT_SYMBOL(drm_vma_node_revoke);
385
386/**
387 * drm_vma_node_is_allowed - Check whether an open-file is granted access
388 * @node: Node to check
389 * @tag: Tag of file to remove
390 *
391 * Search the list in @node whether @tag is currently on the list of allowed
392 * open-files (see drm_vma_node_allow()).
393 *
394 * This is locked against concurrent access internally.
395 *
396 * RETURNS:
397 * true if @filp is on the list
398 */
399bool drm_vma_node_is_allowed(struct drm_vma_offset_node *node,
400			     struct drm_file *tag)
401{
402	struct drm_vma_offset_file *entry;
403	struct rb_node *iter;
404
405	read_lock(&node->vm_lock);
406
407	iter = node->vm_files.rb_node;
408	while (likely(iter)) {
409		entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
410		if (tag == entry->vm_tag)
411			break;
412		else if (tag > entry->vm_tag)
413			iter = iter->rb_right;
414		else
415			iter = iter->rb_left;
416	}
417
418	read_unlock(&node->vm_lock);
419
420	return iter;
421}
422EXPORT_SYMBOL(drm_vma_node_is_allowed);