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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_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
13struct 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 */
48struct 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
58static DEFINE_SPINLOCK(ioasid_allocator_lock);
59static LIST_HEAD(allocators_list);
60
61static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void *opaque);
62static void default_free(ioasid_t ioasid, void *opaque);
63
64static struct ioasid_allocator_ops default_ops = {
65 .alloc = default_alloc,
66 .free = default_free,
67};
68
69static struct ioasid_allocator_data default_allocator = {
70 .ops = &default_ops,
71 .flags = 0,
72 .xa = XARRAY_INIT(ioasid_xa, XA_FLAGS_ALLOC),
73};
74
75static struct ioasid_allocator_data *active_allocator = &default_allocator;
76
77static 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
89static 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 */
98static 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
117static 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 */
138int 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;
190out_free:
191 kfree(ia_data);
192out_unlock:
193 spin_unlock(&ioasid_allocator_lock);
194 return ret;
195}
196EXPORT_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 */
206void 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
255exit_unlock:
256 spin_unlock(&ioasid_allocator_lock);
257}
258EXPORT_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 */
268int 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}
290EXPORT_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 */
304ioasid_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;
341exit_free:
342 spin_unlock(&ioasid_allocator_lock);
343 kfree(data);
344 return INVALID_IOASID;
345}
346EXPORT_SYMBOL_GPL(ioasid_alloc);
347
348/**
349 * ioasid_free - Free an ioasid
350 * @ioasid: the ID to remove
351 */
352void 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
370exit_unlock:
371 spin_unlock(&ioasid_allocator_lock);
372}
373EXPORT_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 */
389void *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;
412unlock:
413 rcu_read_unlock();
414
415 return priv;
416}
417EXPORT_SYMBOL_GPL(ioasid_find);
418
419MODULE_AUTHOR("Jean-Philippe Brucker <jean-philippe.brucker@arm.com>");
420MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@linux.intel.com>");
421MODULE_DESCRIPTION("IO Address Space ID (IOASID) allocator");
422MODULE_LICENSE("GPL");