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         drm_mm_init(&mgr->vm_addr_space_mm, page_offset, size);
  90 }
  91 EXPORT_SYMBOL(drm_vma_offset_manager_init);
  92
  93 /**
  94  * drm_vma_offset_manager_destroy() - Destroy offset manager
  95  * @mgr: Manager object
  96  *
  97  * Destroy an object manager which was previously created via
  98  * drm_vma_offset_manager_init(). The caller must remove all allocated nodes
  99  * before destroying the manager. Otherwise, drm_mm will refuse to free the
 100  * requested resources.
 101  *
 102  * The manager must not be accessed after this function is called.
 103  */
 104 void drm_vma_offset_manager_destroy(struct drm_vma_offset_manager *mgr)
 105 {
 106         /* take the lock to protect against buggy drivers */
 107         write_lock(&mgr->vm_lock);
 108         drm_mm_takedown(&mgr->vm_addr_space_mm);
 109         write_unlock(&mgr->vm_lock);
 110 }
 111 EXPORT_SYMBOL(drm_vma_offset_manager_destroy);
 112
 113 /**
 114  * drm_vma_offset_lookup_locked() - Find node in offset space
 115  * @mgr: Manager object
 116  * @start: Start address for object (page-based)
 117  * @pages: Size of object (page-based)
 118  *
 119  * Find a node given a start address and object size. This returns the _best_
 120  * match for the given node. That is, @start may point somewhere into a valid
 121  * region and the given node will be returned, as long as the node spans the
 122  * whole requested area (given the size in number of pages as @pages).
 123  *
 124  * Note that before lookup the vma offset manager lookup lock must be acquired
 125  * with drm_vma_offset_lock_lookup(). See there for an example. This can then be
 126  * used to implement weakly referenced lookups using kref_get_unless_zero().
 127  *
 128  * Example:
 129  *
 130  * ::
 131  *
 132  *     drm_vma_offset_lock_lookup(mgr);
 133  *     node = drm_vma_offset_lookup_locked(mgr);
 134  *     if (node)
 135  *         kref_get_unless_zero(container_of(node, sth, entr));
 136  *     drm_vma_offset_unlock_lookup(mgr);
 137  *
 138  * RETURNS:
 139  * Returns NULL if no suitable node can be found. Otherwise, the best match
 140  * is returned. It's the caller's responsibility to make sure the node doesn't
 141  * get destroyed before the caller can access it.
 142  */
 143 struct drm_vma_offset_node *drm_vma_offset_lookup_locked(struct drm_vma_offset_manager *mgr,
 144                                                          unsigned long start,
 145                                                          unsigned long pages)
 146 {
 147         struct drm_mm_node *node, *best;
 148         struct rb_node *iter;
 149         unsigned long offset;
 150
 151         iter = mgr->vm_addr_space_mm.interval_tree.rb_node;
 152         best = NULL;
 153
 154         while (likely(iter)) {
 155                 node = rb_entry(iter, struct drm_mm_node, rb);
 156                 offset = node->start;
 157                 if (start >= offset) {
 158                         iter = iter->rb_right;
 159                         best = node;
 160                         if (start == offset)
 161                                 break;
 162                 } else {
 163                         iter = iter->rb_left;
 164                 }
 165         }
 166
 167         /* verify that the node spans the requested area */
 168         if (best) {
 169                 offset = best->start + best->size;
 170                 if (offset < start + pages)
 171                         best = NULL;
 172         }
 173
 174         if (!best)
 175                 return NULL;
 176
 177         return container_of(best, struct drm_vma_offset_node, vm_node);
 178 }
 179 EXPORT_SYMBOL(drm_vma_offset_lookup_locked);
 180
 181 /**
 182  * drm_vma_offset_add() - Add offset node to manager
 183  * @mgr: Manager object
 184  * @node: Node to be added
 185  * @pages: Allocation size visible to user-space (in number of pages)
 186  *
 187  * Add a node to the offset-manager. If the node was already added, this does
 188  * nothing and return 0. @pages is the size of the object given in number of
 189  * pages.
 190  * After this call succeeds, you can access the offset of the node until it
 191  * is removed again.
 192  *
 193  * If this call fails, it is safe to retry the operation or call
 194  * drm_vma_offset_remove(), anyway. However, no cleanup is required in that
 195  * case.
 196  *
 197  * @pages is not required to be the same size as the underlying memory object
 198  * that you want to map. It only limits the size that user-space can map into
 199  * their address space.
 200  *
 201  * RETURNS:
 202  * 0 on success, negative error code on failure.
 203  */
 204 int drm_vma_offset_add(struct drm_vma_offset_manager *mgr,
 205                        struct drm_vma_offset_node *node, unsigned long pages)
 206 {
 207         int ret;
 208
 209         write_lock(&mgr->vm_lock);
 210
 211         if (drm_mm_node_allocated(&node->vm_node)) {
 212                 ret = 0;
 213                 goto out_unlock;
 214         }
 215
 216         ret = drm_mm_insert_node(&mgr->vm_addr_space_mm, &node->vm_node,
 217                                  pages, 0, DRM_MM_SEARCH_DEFAULT);
 218         if (ret)
 219                 goto out_unlock;
 220
 221 out_unlock:
 222         write_unlock(&mgr->vm_lock);
 223         return ret;
 224 }
 225 EXPORT_SYMBOL(drm_vma_offset_add);
 226
 227 /**
 228  * drm_vma_offset_remove() - Remove offset node from manager
 229  * @mgr: Manager object
 230  * @node: Node to be removed
 231  *
 232  * Remove a node from the offset manager. If the node wasn't added before, this
 233  * does nothing. After this call returns, the offset and size will be 0 until a
 234  * new offset is allocated via drm_vma_offset_add() again. Helper functions like
 235  * drm_vma_node_start() and drm_vma_node_offset_addr() will return 0 if no
 236  * offset is allocated.
 237  */
 238 void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
 239                            struct drm_vma_offset_node *node)
 240 {
 241         write_lock(&mgr->vm_lock);
 242
 243         if (drm_mm_node_allocated(&node->vm_node)) {
 244                 drm_mm_remove_node(&node->vm_node);
 245                 memset(&node->vm_node, 0, sizeof(node->vm_node));
 246         }
 247
 248         write_unlock(&mgr->vm_lock);
 249 }
 250 EXPORT_SYMBOL(drm_vma_offset_remove);
 251
 252 /**
 253  * drm_vma_node_allow - Add open-file to list of allowed users
 254  * @node: Node to modify
 255  * @filp: Open file to add
 256  *
 257  * Add @filp to the list of allowed open-files for this node. If @filp is
 258  * already on this list, the ref-count is incremented.
 259  *
 260  * The list of allowed-users is preserved across drm_vma_offset_add() and
 261  * drm_vma_offset_remove() calls. You may even call it if the node is currently
 262  * not added to any offset-manager.
 263  *
 264  * You must remove all open-files the same number of times as you added them
 265  * before destroying the node. Otherwise, you will leak memory.
 266  *
 267  * This is locked against concurrent access internally.
 268  *
 269  * RETURNS:
 270  * 0 on success, negative error code on internal failure (out-of-mem)
 271  */
 272 int drm_vma_node_allow(struct drm_vma_offset_node *node, struct file *filp)
 273 {
 274         struct rb_node **iter;
 275         struct rb_node *parent = NULL;
 276         struct drm_vma_offset_file *new, *entry;
 277         int ret = 0;
 278
 279         /* Preallocate entry to avoid atomic allocations below. It is quite
 280          * unlikely that an open-file is added twice to a single node so we
 281          * don't optimize for this case. OOM is checked below only if the entry
 282          * is actually used. */
 283         new = kmalloc(sizeof(*entry), GFP_KERNEL);
 284
 285         write_lock(&node->vm_lock);
 286
 287         iter = &node->vm_files.rb_node;
 288
 289         while (likely(*iter)) {
 290                 parent = *iter;
 291                 entry = rb_entry(*iter, struct drm_vma_offset_file, vm_rb);
 292
 293                 if (filp == entry->vm_filp) {
 294                         entry->vm_count++;
 295                         goto unlock;
 296                 } else if (filp > entry->vm_filp) {
 297                         iter = &(*iter)->rb_right;
 298                 } else {
 299                         iter = &(*iter)->rb_left;
 300                 }
 301         }
 302
 303         if (!new) {
 304                 ret = -ENOMEM;
 305                 goto unlock;
 306         }
 307
 308         new->vm_filp = filp;
 309         new->vm_count = 1;
 310         rb_link_node(&new->vm_rb, parent, iter);
 311         rb_insert_color(&new->vm_rb, &node->vm_files);
 312         new = NULL;
 313
 314 unlock:
 315         write_unlock(&node->vm_lock);
 316         kfree(new);
 317         return ret;
 318 }
 319 EXPORT_SYMBOL(drm_vma_node_allow);
 320
 321 /**
 322  * drm_vma_node_revoke - Remove open-file from list of allowed users
 323  * @node: Node to modify
 324  * @filp: Open file to remove
 325  *
 326  * Decrement the ref-count of @filp in the list of allowed open-files on @node.
 327  * If the ref-count drops to zero, remove @filp from the list. You must call
 328  * this once for every drm_vma_node_allow() on @filp.
 329  *
 330  * This is locked against concurrent access internally.
 331  *
 332  * If @filp is not on the list, nothing is done.
 333  */
 334 void drm_vma_node_revoke(struct drm_vma_offset_node *node, struct file *filp)
 335 {
 336         struct drm_vma_offset_file *entry;
 337         struct rb_node *iter;
 338
 339         write_lock(&node->vm_lock);
 340
 341         iter = node->vm_files.rb_node;
 342         while (likely(iter)) {
 343                 entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
 344                 if (filp == entry->vm_filp) {
 345                         if (!--entry->vm_count) {
 346                                 rb_erase(&entry->vm_rb, &node->vm_files);
 347                                 kfree(entry);
 348                         }
 349                         break;
 350                 } else if (filp > entry->vm_filp) {
 351                         iter = iter->rb_right;
 352                 } else {
 353                         iter = iter->rb_left;
 354                 }
 355         }
 356
 357         write_unlock(&node->vm_lock);
 358 }
 359 EXPORT_SYMBOL(drm_vma_node_revoke);
 360
 361 /**
 362  * drm_vma_node_is_allowed - Check whether an open-file is granted access
 363  * @node: Node to check
 364  * @filp: Open-file to check for
 365  *
 366  * Search the list in @node whether @filp is currently on the list of allowed
 367  * open-files (see drm_vma_node_allow()).
 368  *
 369  * This is locked against concurrent access internally.
 370  *
 371  * RETURNS:
 372  * true iff @filp is on the list
 373  */
 374 bool drm_vma_node_is_allowed(struct drm_vma_offset_node *node,
 375                              struct file *filp)
 376 {
 377         struct drm_vma_offset_file *entry;
 378         struct rb_node *iter;
 379
 380         read_lock(&node->vm_lock);
 381
 382         iter = node->vm_files.rb_node;
 383         while (likely(iter)) {
 384                 entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
 385                 if (filp == entry->vm_filp)
 386                         break;
 387                 else if (filp > entry->vm_filp)
 388                         iter = iter->rb_right;
 389                 else
 390                         iter = iter->rb_left;
 391         }
 392
 393         read_unlock(&node->vm_lock);
 394
 395         return iter;
 396 }
 397 EXPORT_SYMBOL(drm_vma_node_is_allowed);