drivers/gpu/drm/drm_vma_manager.c

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