drivers/iommu/ioasid.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * I/O Address Space ID allocator. There is one global IOASID space, split into
   4  * subsets. Users create a subset with DECLARE_IOASID_SET, then allocate and
   5  * free IOASIDs with ioasid_alloc and ioasid_free.
   6  */
   7 #include <linux/ioasid.h>
   8 #include <linux/module.h>
   9 #include <linux/slab.h>
  10 #include <linux/spinlock.h>
  11 #include <linux/xarray.h>
  12
  13 struct ioasid_data {
  14         ioasid_t id;
  15         struct ioasid_set *set;
  16         void *private;
  17         struct rcu_head rcu;
  18 };
  19
  20 /*
  21  * struct ioasid_allocator_data - Internal data structure to hold information
  22  * about an allocator. There are two types of allocators:
  23  *
  24  * - Default allocator always has its own XArray to track the IOASIDs allocated.
  25  * - Custom allocators may share allocation helpers with different private data.
  26  *   Custom allocators that share the same helper functions also share the same
  27  *   XArray.
  28  * Rules:
  29  * 1. Default allocator is always available, not dynamically registered. This is
  30  *    to prevent race conditions with early boot code that want to register
  31  *    custom allocators or allocate IOASIDs.
  32  * 2. Custom allocators take precedence over the default allocator.
  33  * 3. When all custom allocators sharing the same helper functions are
  34  *    unregistered (e.g. due to hotplug), all outstanding IOASIDs must be
  35  *    freed. Otherwise, outstanding IOASIDs will be lost and orphaned.
  36  * 4. When switching between custom allocators sharing the same helper
  37  *    functions, outstanding IOASIDs are preserved.
  38  * 5. When switching between custom allocator and default allocator, all IOASIDs
  39  *    must be freed to ensure unadulterated space for the new allocator.
  40  *
  41  * @ops:        allocator helper functions and its data
  42  * @list:       registered custom allocators
  43  * @slist:      allocators share the same ops but different data
  44  * @flags:      attributes of the allocator
  45  * @xa:         xarray holds the IOASID space
  46  * @rcu:        used for kfree_rcu when unregistering allocator
  47  */
  48 struct ioasid_allocator_data {
  49         struct ioasid_allocator_ops *ops;
  50         struct list_head list;
  51         struct list_head slist;
  52 #define IOASID_ALLOCATOR_CUSTOM BIT(0) /* Needs framework to track results */
  53         unsigned long flags;
  54         struct xarray xa;
  55         struct rcu_head rcu;
  56 };
  57
  58 static DEFINE_SPINLOCK(ioasid_allocator_lock);
  59 static LIST_HEAD(allocators_list);
  60
  61 static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void *opaque);
  62 static void default_free(ioasid_t ioasid, void *opaque);
  63
  64 static struct ioasid_allocator_ops default_ops = {
  65         .alloc = default_alloc,
  66         .free = default_free,
  67 };
  68
  69 static struct ioasid_allocator_data default_allocator = {
  70         .ops = &default_ops,
  71         .flags = 0,
  72         .xa = XARRAY_INIT(ioasid_xa, XA_FLAGS_ALLOC),
  73 };
  74
  75 static struct ioasid_allocator_data *active_allocator = &default_allocator;
  76
  77 static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void *opaque)
  78 {
  79         ioasid_t id;
  80
  81         if (xa_alloc(&default_allocator.xa, &id, opaque, XA_LIMIT(min, max), GFP_ATOMIC)) {
  82                 pr_err("Failed to alloc ioasid from %d to %d\n", min, max);
  83                 return INVALID_IOASID;
  84         }
  85
  86         return id;
  87 }
  88
  89 static void default_free(ioasid_t ioasid, void *opaque)
  90 {
  91         struct ioasid_data *ioasid_data;
  92
  93         ioasid_data = xa_erase(&default_allocator.xa, ioasid);
  94         kfree_rcu(ioasid_data, rcu);
  95 }
  96
  97 /* Allocate and initialize a new custom allocator with its helper functions */
  98 static struct ioasid_allocator_data *ioasid_alloc_allocator(struct ioasid_allocator_ops *ops)
  99 {
 100         struct ioasid_allocator_data *ia_data;
 101
 102         ia_data = kzalloc(sizeof(*ia_data), GFP_ATOMIC);
 103         if (!ia_data)
 104                 return NULL;
 105
 106         xa_init_flags(&ia_data->xa, XA_FLAGS_ALLOC);
 107         INIT_LIST_HEAD(&ia_data->slist);
 108         ia_data->flags |= IOASID_ALLOCATOR_CUSTOM;
 109         ia_data->ops = ops;
 110
 111         /* For tracking custom allocators that share the same ops */
 112         list_add_tail(&ops->list, &ia_data->slist);
 113
 114         return ia_data;
 115 }
 116
 117 static bool use_same_ops(struct ioasid_allocator_ops *a, struct ioasid_allocator_ops *b)
 118 {
 119         return (a->free == b->free) && (a->alloc == b->alloc);
 120 }
 121
 122 /**
 123  * ioasid_register_allocator - register a custom allocator
 124  * @ops: the custom allocator ops to be registered
 125  *
 126  * Custom allocators take precedence over the default xarray based allocator.
 127  * Private data associated with the IOASID allocated by the custom allocators
 128  * are managed by IOASID framework similar to data stored in xa by default
 129  * allocator.
 130  *
 131  * There can be multiple allocators registered but only one is active. In case
 132  * of runtime removal of a custom allocator, the next one is activated based
 133  * on the registration ordering.
 134  *
 135  * Multiple allocators can share the same alloc() function, in this case the
 136  * IOASID space is shared.
 137  */
 138 int ioasid_register_allocator(struct ioasid_allocator_ops *ops)
 139 {
 140         struct ioasid_allocator_data *ia_data;
 141         struct ioasid_allocator_data *pallocator;
 142         int ret = 0;
 143
 144         spin_lock(&ioasid_allocator_lock);
 145
 146         ia_data = ioasid_alloc_allocator(ops);
 147         if (!ia_data) {
 148                 ret = -ENOMEM;
 149                 goto out_unlock;
 150         }
 151
 152         /*
 153          * No particular preference, we activate the first one and keep
 154          * the later registered allocators in a list in case the first one gets
 155          * removed due to hotplug.
 156          */
 157         if (list_empty(&allocators_list)) {
 158                 WARN_ON(active_allocator != &default_allocator);
 159                 /* Use this new allocator if default is not active */
 160                 if (xa_empty(&active_allocator->xa)) {
 161                         rcu_assign_pointer(active_allocator, ia_data);
 162                         list_add_tail(&ia_data->list, &allocators_list);
 163                         goto out_unlock;
 164                 }
 165                 pr_warn("Default allocator active with outstanding IOASID\n");
 166                 ret = -EAGAIN;
 167                 goto out_free;
 168         }
 169
 170         /* Check if the allocator is already registered */
 171         list_for_each_entry(pallocator, &allocators_list, list) {
 172                 if (pallocator->ops == ops) {
 173                         pr_err("IOASID allocator already registered\n");
 174                         ret = -EEXIST;
 175                         goto out_free;
 176                 } else if (use_same_ops(pallocator->ops, ops)) {
 177                         /*
 178                          * If the new allocator shares the same ops,
 179                          * then they will share the same IOASID space.
 180                          * We should put them under the same xarray.
 181                          */
 182                         list_add_tail(&ops->list, &pallocator->slist);
 183                         goto out_free;
 184                 }
 185         }
 186         list_add_tail(&ia_data->list, &allocators_list);
 187
 188         spin_unlock(&ioasid_allocator_lock);
 189         return 0;
 190 out_free:
 191         kfree(ia_data);
 192 out_unlock:
 193         spin_unlock(&ioasid_allocator_lock);
 194         return ret;
 195 }
 196 EXPORT_SYMBOL_GPL(ioasid_register_allocator);
 197
 198 /**
 199  * ioasid_unregister_allocator - Remove a custom IOASID allocator ops
 200  * @ops: the custom allocator to be removed
 201  *
 202  * Remove an allocator from the list, activate the next allocator in
 203  * the order it was registered. Or revert to default allocator if all
 204  * custom allocators are unregistered without outstanding IOASIDs.
 205  */
 206 void ioasid_unregister_allocator(struct ioasid_allocator_ops *ops)
 207 {
 208         struct ioasid_allocator_data *pallocator;
 209         struct ioasid_allocator_ops *sops;
 210
 211         spin_lock(&ioasid_allocator_lock);
 212         if (list_empty(&allocators_list)) {
 213                 pr_warn("No custom IOASID allocators active!\n");
 214                 goto exit_unlock;
 215         }
 216
 217         list_for_each_entry(pallocator, &allocators_list, list) {
 218                 if (!use_same_ops(pallocator->ops, ops))
 219                         continue;
 220
 221                 if (list_is_singular(&pallocator->slist)) {
 222                         /* No shared helper functions */
 223                         list_del(&pallocator->list);
 224                         /*
 225                          * All IOASIDs should have been freed before
 226                          * the last allocator that shares the same ops
 227                          * is unregistered.
 228                          */
 229                         WARN_ON(!xa_empty(&pallocator->xa));
 230                         if (list_empty(&allocators_list)) {
 231                                 pr_info("No custom IOASID allocators, switch to default.\n");
 232                                 rcu_assign_pointer(active_allocator, &default_allocator);
 233                         } else if (pallocator == active_allocator) {
 234                                 rcu_assign_pointer(active_allocator,
 235                                                 list_first_entry(&allocators_list,
 236                                                                 struct ioasid_allocator_data, list));
 237                                 pr_info("IOASID allocator changed");
 238                         }
 239                         kfree_rcu(pallocator, rcu);
 240                         break;
 241                 }
 242                 /*
 243                  * Find the matching shared ops to delete,
 244                  * but keep outstanding IOASIDs
 245                  */
 246                 list_for_each_entry(sops, &pallocator->slist, list) {
 247                         if (sops == ops) {
 248                                 list_del(&ops->list);
 249                                 break;
 250                         }
 251                 }
 252                 break;
 253         }
 254
 255 exit_unlock:
 256         spin_unlock(&ioasid_allocator_lock);
 257 }
 258 EXPORT_SYMBOL_GPL(ioasid_unregister_allocator);
 259
 260 /**
 261  * ioasid_set_data - Set private data for an allocated ioasid
 262  * @ioasid: the ID to set data
 263  * @data:   the private data
 264  *
 265  * For IOASID that is already allocated, private data can be set
 266  * via this API. Future lookup can be done via ioasid_find.
 267  */
 268 int ioasid_set_data(ioasid_t ioasid, void *data)
 269 {
 270         struct ioasid_data *ioasid_data;
 271         int ret = 0;
 272
 273         spin_lock(&ioasid_allocator_lock);
 274         ioasid_data = xa_load(&active_allocator->xa, ioasid);
 275         if (ioasid_data)
 276                 rcu_assign_pointer(ioasid_data->private, data);
 277         else
 278                 ret = -ENOENT;
 279         spin_unlock(&ioasid_allocator_lock);
 280
 281         /*
 282          * Wait for readers to stop accessing the old private data, so the
 283          * caller can free it.
 284          */
 285         if (!ret)
 286                 synchronize_rcu();
 287
 288         return ret;
 289 }
 290 EXPORT_SYMBOL_GPL(ioasid_set_data);
 291
 292 /**
 293  * ioasid_alloc - Allocate an IOASID
 294  * @set: the IOASID set
 295  * @min: the minimum ID (inclusive)
 296  * @max: the maximum ID (inclusive)
 297  * @private: data private to the caller
 298  *
 299  * Allocate an ID between @min and @max. The @private pointer is stored
 300  * internally and can be retrieved with ioasid_find().
 301  *
 302  * Return: the allocated ID on success, or %INVALID_IOASID on failure.
 303  */
 304 ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
 305                       void *private)
 306 {
 307         struct ioasid_data *data;
 308         void *adata;
 309         ioasid_t id;
 310
 311         data = kzalloc(sizeof(*data), GFP_ATOMIC);
 312         if (!data)
 313                 return INVALID_IOASID;
 314
 315         data->set = set;
 316         data->private = private;
 317
 318         /*
 319          * Custom allocator needs allocator data to perform platform specific
 320          * operations.
 321          */
 322         spin_lock(&ioasid_allocator_lock);
 323         adata = active_allocator->flags & IOASID_ALLOCATOR_CUSTOM ? active_allocator->ops->pdata : data;
 324         id = active_allocator->ops->alloc(min, max, adata);
 325         if (id == INVALID_IOASID) {
 326                 pr_err("Failed ASID allocation %lu\n", active_allocator->flags);
 327                 goto exit_free;
 328         }
 329
 330         if ((active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) &&
 331              xa_alloc(&active_allocator->xa, &id, data, XA_LIMIT(id, id), GFP_ATOMIC)) {
 332                 /* Custom allocator needs framework to store and track allocation results */
 333                 pr_err("Failed to alloc ioasid from %d\n", id);
 334                 active_allocator->ops->free(id, active_allocator->ops->pdata);
 335                 goto exit_free;
 336         }
 337         data->id = id;
 338
 339         spin_unlock(&ioasid_allocator_lock);
 340         return id;
 341 exit_free:
 342         spin_unlock(&ioasid_allocator_lock);
 343         kfree(data);
 344         return INVALID_IOASID;
 345 }
 346 EXPORT_SYMBOL_GPL(ioasid_alloc);
 347
 348 /**
 349  * ioasid_free - Free an IOASID
 350  * @ioasid: the ID to remove
 351  */
 352 void ioasid_free(ioasid_t ioasid)
 353 {
 354         struct ioasid_data *ioasid_data;
 355
 356         spin_lock(&ioasid_allocator_lock);
 357         ioasid_data = xa_load(&active_allocator->xa, ioasid);
 358         if (!ioasid_data) {
 359                 pr_err("Trying to free unknown IOASID %u\n", ioasid);
 360                 goto exit_unlock;
 361         }
 362
 363         active_allocator->ops->free(ioasid, active_allocator->ops->pdata);
 364         /* Custom allocator needs additional steps to free the xa element */
 365         if (active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) {
 366                 ioasid_data = xa_erase(&active_allocator->xa, ioasid);
 367                 kfree_rcu(ioasid_data, rcu);
 368         }
 369
 370 exit_unlock:
 371         spin_unlock(&ioasid_allocator_lock);
 372 }
 373 EXPORT_SYMBOL_GPL(ioasid_free);
 374
 375 /**
 376  * ioasid_find - Find IOASID data
 377  * @set: the IOASID set
 378  * @ioasid: the IOASID to find
 379  * @getter: function to call on the found object
 380  *
 381  * The optional getter function allows to take a reference to the found object
 382  * under the rcu lock. The function can also check if the object is still valid:
 383  * if @getter returns false, then the object is invalid and NULL is returned.
 384  *
 385  * If the IOASID exists, return the private pointer passed to ioasid_alloc.
 386  * Private data can be NULL if not set. Return an error if the IOASID is not
 387  * found, or if @set is not NULL and the IOASID does not belong to the set.
 388  */
 389 void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
 390                   bool (*getter)(void *))
 391 {
 392         void *priv;
 393         struct ioasid_data *ioasid_data;
 394         struct ioasid_allocator_data *idata;
 395
 396         rcu_read_lock();
 397         idata = rcu_dereference(active_allocator);
 398         ioasid_data = xa_load(&idata->xa, ioasid);
 399         if (!ioasid_data) {
 400                 priv = ERR_PTR(-ENOENT);
 401                 goto unlock;
 402         }
 403         if (set && ioasid_data->set != set) {
 404                 /* data found but does not belong to the set */
 405                 priv = ERR_PTR(-EACCES);
 406                 goto unlock;
 407         }
 408         /* Now IOASID and its set is verified, we can return the private data */
 409         priv = rcu_dereference(ioasid_data->private);
 410         if (getter && !getter(priv))
 411                 priv = NULL;
 412 unlock:
 413         rcu_read_unlock();
 414
 415         return priv;
 416 }
 417 EXPORT_SYMBOL_GPL(ioasid_find);
 418
 419 MODULE_AUTHOR("Jean-Philippe Brucker <jean-philippe.brucker@arm.com>");
 420 MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@linux.intel.com>");
 421 MODULE_DESCRIPTION("IO Address Space ID (IOASID) allocator");
 422 MODULE_LICENSE("GPL");