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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_put.
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
13struct ioasid_data {
14 ioasid_t id;
15 struct ioasid_set *set;
16 void *private;
17 struct rcu_head rcu;
18 refcount_t refs;
19};
20
21/*
22 * struct ioasid_allocator_data - Internal data structure to hold information
23 * about an allocator. There are two types of allocators:
24 *
25 * - Default allocator always has its own XArray to track the IOASIDs allocated.
26 * - Custom allocators may share allocation helpers with different private data.
27 * Custom allocators that share the same helper functions also share the same
28 * XArray.
29 * Rules:
30 * 1. Default allocator is always available, not dynamically registered. This is
31 * to prevent race conditions with early boot code that want to register
32 * custom allocators or allocate IOASIDs.
33 * 2. Custom allocators take precedence over the default allocator.
34 * 3. When all custom allocators sharing the same helper functions are
35 * unregistered (e.g. due to hotplug), all outstanding IOASIDs must be
36 * freed. Otherwise, outstanding IOASIDs will be lost and orphaned.
37 * 4. When switching between custom allocators sharing the same helper
38 * functions, outstanding IOASIDs are preserved.
39 * 5. When switching between custom allocator and default allocator, all IOASIDs
40 * must be freed to ensure unadulterated space for the new allocator.
41 *
42 * @ops: allocator helper functions and its data
43 * @list: registered custom allocators
44 * @slist: allocators share the same ops but different data
45 * @flags: attributes of the allocator
46 * @xa: xarray holds the IOASID space
47 * @rcu: used for kfree_rcu when unregistering allocator
48 */
49struct ioasid_allocator_data {
50 struct ioasid_allocator_ops *ops;
51 struct list_head list;
52 struct list_head slist;
53#define IOASID_ALLOCATOR_CUSTOM BIT(0) /* Needs framework to track results */
54 unsigned long flags;
55 struct xarray xa;
56 struct rcu_head rcu;
57};
58
59static DEFINE_SPINLOCK(ioasid_allocator_lock);
60static LIST_HEAD(allocators_list);
61
62static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void *opaque);
63static void default_free(ioasid_t ioasid, void *opaque);
64
65static struct ioasid_allocator_ops default_ops = {
66 .alloc = default_alloc,
67 .free = default_free,
68};
69
70static struct ioasid_allocator_data default_allocator = {
71 .ops = &default_ops,
72 .flags = 0,
73 .xa = XARRAY_INIT(ioasid_xa, XA_FLAGS_ALLOC),
74};
75
76static struct ioasid_allocator_data *active_allocator = &default_allocator;
77
78static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void *opaque)
79{
80 ioasid_t id;
81
82 if (xa_alloc(&default_allocator.xa, &id, opaque, XA_LIMIT(min, max), GFP_ATOMIC)) {
83 pr_err("Failed to alloc ioasid from %d to %d\n", min, max);
84 return INVALID_IOASID;
85 }
86
87 return id;
88}
89
90static void default_free(ioasid_t ioasid, void *opaque)
91{
92 struct ioasid_data *ioasid_data;
93
94 ioasid_data = xa_erase(&default_allocator.xa, ioasid);
95 kfree_rcu(ioasid_data, rcu);
96}
97
98/* Allocate and initialize a new custom allocator with its helper functions */
99static struct ioasid_allocator_data *ioasid_alloc_allocator(struct ioasid_allocator_ops *ops)
100{
101 struct ioasid_allocator_data *ia_data;
102
103 ia_data = kzalloc(sizeof(*ia_data), GFP_ATOMIC);
104 if (!ia_data)
105 return NULL;
106
107 xa_init_flags(&ia_data->xa, XA_FLAGS_ALLOC);
108 INIT_LIST_HEAD(&ia_data->slist);
109 ia_data->flags |= IOASID_ALLOCATOR_CUSTOM;
110 ia_data->ops = ops;
111
112 /* For tracking custom allocators that share the same ops */
113 list_add_tail(&ops->list, &ia_data->slist);
114
115 return ia_data;
116}
117
118static bool use_same_ops(struct ioasid_allocator_ops *a, struct ioasid_allocator_ops *b)
119{
120 return (a->free == b->free) && (a->alloc == b->alloc);
121}
122
123/**
124 * ioasid_register_allocator - register a custom allocator
125 * @ops: the custom allocator ops to be registered
126 *
127 * Custom allocators take precedence over the default xarray based allocator.
128 * Private data associated with the IOASID allocated by the custom allocators
129 * are managed by IOASID framework similar to data stored in xa by default
130 * allocator.
131 *
132 * There can be multiple allocators registered but only one is active. In case
133 * of runtime removal of a custom allocator, the next one is activated based
134 * on the registration ordering.
135 *
136 * Multiple allocators can share the same alloc() function, in this case the
137 * IOASID space is shared.
138 */
139int ioasid_register_allocator(struct ioasid_allocator_ops *ops)
140{
141 struct ioasid_allocator_data *ia_data;
142 struct ioasid_allocator_data *pallocator;
143 int ret = 0;
144
145 spin_lock(&ioasid_allocator_lock);
146
147 ia_data = ioasid_alloc_allocator(ops);
148 if (!ia_data) {
149 ret = -ENOMEM;
150 goto out_unlock;
151 }
152
153 /*
154 * No particular preference, we activate the first one and keep
155 * the later registered allocators in a list in case the first one gets
156 * removed due to hotplug.
157 */
158 if (list_empty(&allocators_list)) {
159 WARN_ON(active_allocator != &default_allocator);
160 /* Use this new allocator if default is not active */
161 if (xa_empty(&active_allocator->xa)) {
162 rcu_assign_pointer(active_allocator, ia_data);
163 list_add_tail(&ia_data->list, &allocators_list);
164 goto out_unlock;
165 }
166 pr_warn("Default allocator active with outstanding IOASID\n");
167 ret = -EAGAIN;
168 goto out_free;
169 }
170
171 /* Check if the allocator is already registered */
172 list_for_each_entry(pallocator, &allocators_list, list) {
173 if (pallocator->ops == ops) {
174 pr_err("IOASID allocator already registered\n");
175 ret = -EEXIST;
176 goto out_free;
177 } else if (use_same_ops(pallocator->ops, ops)) {
178 /*
179 * If the new allocator shares the same ops,
180 * then they will share the same IOASID space.
181 * We should put them under the same xarray.
182 */
183 list_add_tail(&ops->list, &pallocator->slist);
184 goto out_free;
185 }
186 }
187 list_add_tail(&ia_data->list, &allocators_list);
188
189 spin_unlock(&ioasid_allocator_lock);
190 return 0;
191out_free:
192 kfree(ia_data);
193out_unlock:
194 spin_unlock(&ioasid_allocator_lock);
195 return ret;
196}
197EXPORT_SYMBOL_GPL(ioasid_register_allocator);
198
199/**
200 * ioasid_unregister_allocator - Remove a custom IOASID allocator ops
201 * @ops: the custom allocator to be removed
202 *
203 * Remove an allocator from the list, activate the next allocator in
204 * the order it was registered. Or revert to default allocator if all
205 * custom allocators are unregistered without outstanding IOASIDs.
206 */
207void ioasid_unregister_allocator(struct ioasid_allocator_ops *ops)
208{
209 struct ioasid_allocator_data *pallocator;
210 struct ioasid_allocator_ops *sops;
211
212 spin_lock(&ioasid_allocator_lock);
213 if (list_empty(&allocators_list)) {
214 pr_warn("No custom IOASID allocators active!\n");
215 goto exit_unlock;
216 }
217
218 list_for_each_entry(pallocator, &allocators_list, list) {
219 if (!use_same_ops(pallocator->ops, ops))
220 continue;
221
222 if (list_is_singular(&pallocator->slist)) {
223 /* No shared helper functions */
224 list_del(&pallocator->list);
225 /*
226 * All IOASIDs should have been freed before
227 * the last allocator that shares the same ops
228 * is unregistered.
229 */
230 WARN_ON(!xa_empty(&pallocator->xa));
231 if (list_empty(&allocators_list)) {
232 pr_info("No custom IOASID allocators, switch to default.\n");
233 rcu_assign_pointer(active_allocator, &default_allocator);
234 } else if (pallocator == active_allocator) {
235 rcu_assign_pointer(active_allocator,
236 list_first_entry(&allocators_list,
237 struct ioasid_allocator_data, list));
238 pr_info("IOASID allocator changed");
239 }
240 kfree_rcu(pallocator, rcu);
241 break;
242 }
243 /*
244 * Find the matching shared ops to delete,
245 * but keep outstanding IOASIDs
246 */
247 list_for_each_entry(sops, &pallocator->slist, list) {
248 if (sops == ops) {
249 list_del(&ops->list);
250 break;
251 }
252 }
253 break;
254 }
255
256exit_unlock:
257 spin_unlock(&ioasid_allocator_lock);
258}
259EXPORT_SYMBOL_GPL(ioasid_unregister_allocator);
260
261/**
262 * ioasid_set_data - Set private data for an allocated ioasid
263 * @ioasid: the ID to set data
264 * @data: the private data
265 *
266 * For IOASID that is already allocated, private data can be set
267 * via this API. Future lookup can be done via ioasid_find.
268 */
269int ioasid_set_data(ioasid_t ioasid, void *data)
270{
271 struct ioasid_data *ioasid_data;
272 int ret = 0;
273
274 spin_lock(&ioasid_allocator_lock);
275 ioasid_data = xa_load(&active_allocator->xa, ioasid);
276 if (ioasid_data)
277 rcu_assign_pointer(ioasid_data->private, data);
278 else
279 ret = -ENOENT;
280 spin_unlock(&ioasid_allocator_lock);
281
282 /*
283 * Wait for readers to stop accessing the old private data, so the
284 * caller can free it.
285 */
286 if (!ret)
287 synchronize_rcu();
288
289 return ret;
290}
291EXPORT_SYMBOL_GPL(ioasid_set_data);
292
293/**
294 * ioasid_alloc - Allocate an IOASID
295 * @set: the IOASID set
296 * @min: the minimum ID (inclusive)
297 * @max: the maximum ID (inclusive)
298 * @private: data private to the caller
299 *
300 * Allocate an ID between @min and @max. The @private pointer is stored
301 * internally and can be retrieved with ioasid_find().
302 *
303 * Return: the allocated ID on success, or %INVALID_IOASID on failure.
304 */
305ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
306 void *private)
307{
308 struct ioasid_data *data;
309 void *adata;
310 ioasid_t id;
311
312 data = kzalloc(sizeof(*data), GFP_ATOMIC);
313 if (!data)
314 return INVALID_IOASID;
315
316 data->set = set;
317 data->private = private;
318 refcount_set(&data->refs, 1);
319
320 /*
321 * Custom allocator needs allocator data to perform platform specific
322 * operations.
323 */
324 spin_lock(&ioasid_allocator_lock);
325 adata = active_allocator->flags & IOASID_ALLOCATOR_CUSTOM ? active_allocator->ops->pdata : data;
326 id = active_allocator->ops->alloc(min, max, adata);
327 if (id == INVALID_IOASID) {
328 pr_err("Failed ASID allocation %lu\n", active_allocator->flags);
329 goto exit_free;
330 }
331
332 if ((active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) &&
333 xa_alloc(&active_allocator->xa, &id, data, XA_LIMIT(id, id), GFP_ATOMIC)) {
334 /* Custom allocator needs framework to store and track allocation results */
335 pr_err("Failed to alloc ioasid from %d\n", id);
336 active_allocator->ops->free(id, active_allocator->ops->pdata);
337 goto exit_free;
338 }
339 data->id = id;
340
341 spin_unlock(&ioasid_allocator_lock);
342 return id;
343exit_free:
344 spin_unlock(&ioasid_allocator_lock);
345 kfree(data);
346 return INVALID_IOASID;
347}
348EXPORT_SYMBOL_GPL(ioasid_alloc);
349
350/**
351 * ioasid_get - obtain a reference to the IOASID
352 */
353void ioasid_get(ioasid_t ioasid)
354{
355 struct ioasid_data *ioasid_data;
356
357 spin_lock(&ioasid_allocator_lock);
358 ioasid_data = xa_load(&active_allocator->xa, ioasid);
359 if (ioasid_data)
360 refcount_inc(&ioasid_data->refs);
361 else
362 WARN_ON(1);
363 spin_unlock(&ioasid_allocator_lock);
364}
365EXPORT_SYMBOL_GPL(ioasid_get);
366
367/**
368 * ioasid_put - Release a reference to an ioasid
369 * @ioasid: the ID to remove
370 *
371 * Put a reference to the IOASID, free it when the number of references drops to
372 * zero.
373 *
374 * Return: %true if the IOASID was freed, %false otherwise.
375 */
376bool ioasid_put(ioasid_t ioasid)
377{
378 bool free = false;
379 struct ioasid_data *ioasid_data;
380
381 spin_lock(&ioasid_allocator_lock);
382 ioasid_data = xa_load(&active_allocator->xa, ioasid);
383 if (!ioasid_data) {
384 pr_err("Trying to free unknown IOASID %u\n", ioasid);
385 goto exit_unlock;
386 }
387
388 free = refcount_dec_and_test(&ioasid_data->refs);
389 if (!free)
390 goto exit_unlock;
391
392 active_allocator->ops->free(ioasid, active_allocator->ops->pdata);
393 /* Custom allocator needs additional steps to free the xa element */
394 if (active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) {
395 ioasid_data = xa_erase(&active_allocator->xa, ioasid);
396 kfree_rcu(ioasid_data, rcu);
397 }
398
399exit_unlock:
400 spin_unlock(&ioasid_allocator_lock);
401 return free;
402}
403EXPORT_SYMBOL_GPL(ioasid_put);
404
405/**
406 * ioasid_find - Find IOASID data
407 * @set: the IOASID set
408 * @ioasid: the IOASID to find
409 * @getter: function to call on the found object
410 *
411 * The optional getter function allows to take a reference to the found object
412 * under the rcu lock. The function can also check if the object is still valid:
413 * if @getter returns false, then the object is invalid and NULL is returned.
414 *
415 * If the IOASID exists, return the private pointer passed to ioasid_alloc.
416 * Private data can be NULL if not set. Return an error if the IOASID is not
417 * found, or if @set is not NULL and the IOASID does not belong to the set.
418 */
419void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
420 bool (*getter)(void *))
421{
422 void *priv;
423 struct ioasid_data *ioasid_data;
424 struct ioasid_allocator_data *idata;
425
426 rcu_read_lock();
427 idata = rcu_dereference(active_allocator);
428 ioasid_data = xa_load(&idata->xa, ioasid);
429 if (!ioasid_data) {
430 priv = ERR_PTR(-ENOENT);
431 goto unlock;
432 }
433 if (set && ioasid_data->set != set) {
434 /* data found but does not belong to the set */
435 priv = ERR_PTR(-EACCES);
436 goto unlock;
437 }
438 /* Now IOASID and its set is verified, we can return the private data */
439 priv = rcu_dereference(ioasid_data->private);
440 if (getter && !getter(priv))
441 priv = NULL;
442unlock:
443 rcu_read_unlock();
444
445 return priv;
446}
447EXPORT_SYMBOL_GPL(ioasid_find);
448
449MODULE_AUTHOR("Jean-Philippe Brucker <jean-philippe.brucker@arm.com>");
450MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@linux.intel.com>");
451MODULE_DESCRIPTION("IO Address Space ID (IOASID) allocator");
452MODULE_LICENSE("GPL");