1 // SPDX-License-Identifier: GPL-2.0-only
3 * linux/mm/mmu_notifier.c
5 * Copyright (C) 2008 Qumranet, Inc.
6 * Copyright (C) 2008 SGI
7 * Christoph Lameter <cl@linux.com>
10 #include <linux/rculist.h>
11 #include <linux/mmu_notifier.h>
12 #include <linux/export.h>
14 #include <linux/err.h>
15 #include <linux/interval_tree.h>
16 #include <linux/srcu.h>
17 #include <linux/rcupdate.h>
18 #include <linux/sched.h>
19 #include <linux/sched/mm.h>
20 #include <linux/slab.h>
22 /* global SRCU for all MMs */
23 DEFINE_STATIC_SRCU(srcu);
26 struct lockdep_map __mmu_notifier_invalidate_range_start_map = {
27 .name = "mmu_notifier_invalidate_range_start"
32 * The mmu_notifier_subscriptions structure is allocated and installed in
33 * mm->notifier_subscriptions inside the mm_take_all_locks() protected
34 * critical section and it's released only when mm_count reaches zero
37 struct mmu_notifier_subscriptions {
38 /* all mmu notifiers registered in this mm are queued in this list */
39 struct hlist_head list;
41 /* to serialize the list modifications and hlist_unhashed */
43 unsigned long invalidate_seq;
44 unsigned long active_invalidate_ranges;
45 struct rb_root_cached itree;
47 struct hlist_head deferred_list;
51 * This is a collision-retry read-side/write-side 'lock', a lot like a
52 * seqcount, however this allows multiple write-sides to hold it at
53 * once. Conceptually the write side is protecting the values of the PTEs in
54 * this mm, such that PTES cannot be read into SPTEs (shadow PTEs) while any
57 * Note that the core mm creates nested invalidate_range_start()/end() regions
58 * within the same thread, and runs invalidate_range_start()/end() in parallel
59 * on multiple CPUs. This is designed to not reduce concurrency or block
60 * progress on the mm side.
62 * As a secondary function, holding the full write side also serves to prevent
63 * writers for the itree, this is an optimization to avoid extra locking
64 * during invalidate_range_start/end notifiers.
66 * The write side has two states, fully excluded:
67 * - mm->active_invalidate_ranges != 0
68 * - subscriptions->invalidate_seq & 1 == True (odd)
69 * - some range on the mm_struct is being invalidated
70 * - the itree is not allowed to change
72 * And partially excluded:
73 * - mm->active_invalidate_ranges != 0
74 * - subscriptions->invalidate_seq & 1 == False (even)
75 * - some range on the mm_struct is being invalidated
76 * - the itree is allowed to change
78 * Operations on notifier_subscriptions->invalidate_seq (under spinlock):
79 * seq |= 1 # Begin writing
80 * seq++ # Release the writing state
81 * seq & 1 # True if a writer exists
83 * The later state avoids some expensive work on inv_end in the common case of
84 * no mmu_interval_notifier monitoring the VA.
87 mn_itree_is_invalidating(struct mmu_notifier_subscriptions *subscriptions)
89 lockdep_assert_held(&subscriptions->lock);
90 return subscriptions->invalidate_seq & 1;
93 static struct mmu_interval_notifier *
94 mn_itree_inv_start_range(struct mmu_notifier_subscriptions *subscriptions,
95 const struct mmu_notifier_range *range,
98 struct interval_tree_node *node;
99 struct mmu_interval_notifier *res = NULL;
101 spin_lock(&subscriptions->lock);
102 subscriptions->active_invalidate_ranges++;
103 node = interval_tree_iter_first(&subscriptions->itree, range->start,
106 subscriptions->invalidate_seq |= 1;
107 res = container_of(node, struct mmu_interval_notifier,
111 *seq = subscriptions->invalidate_seq;
112 spin_unlock(&subscriptions->lock);
116 static struct mmu_interval_notifier *
117 mn_itree_inv_next(struct mmu_interval_notifier *interval_sub,
118 const struct mmu_notifier_range *range)
120 struct interval_tree_node *node;
122 node = interval_tree_iter_next(&interval_sub->interval_tree,
123 range->start, range->end - 1);
126 return container_of(node, struct mmu_interval_notifier, interval_tree);
129 static void mn_itree_inv_end(struct mmu_notifier_subscriptions *subscriptions)
131 struct mmu_interval_notifier *interval_sub;
132 struct hlist_node *next;
134 spin_lock(&subscriptions->lock);
135 if (--subscriptions->active_invalidate_ranges ||
136 !mn_itree_is_invalidating(subscriptions)) {
137 spin_unlock(&subscriptions->lock);
141 /* Make invalidate_seq even */
142 subscriptions->invalidate_seq++;
145 * The inv_end incorporates a deferred mechanism like rtnl_unlock().
146 * Adds and removes are queued until the final inv_end happens then
147 * they are progressed. This arrangement for tree updates is used to
148 * avoid using a blocking lock during invalidate_range_start.
150 hlist_for_each_entry_safe(interval_sub, next,
151 &subscriptions->deferred_list,
153 if (RB_EMPTY_NODE(&interval_sub->interval_tree.rb))
154 interval_tree_insert(&interval_sub->interval_tree,
155 &subscriptions->itree);
157 interval_tree_remove(&interval_sub->interval_tree,
158 &subscriptions->itree);
159 hlist_del(&interval_sub->deferred_item);
161 spin_unlock(&subscriptions->lock);
163 wake_up_all(&subscriptions->wq);
167 * mmu_interval_read_begin - Begin a read side critical section against a VA
169 * @interval_sub: The interval subscription
171 * mmu_iterval_read_begin()/mmu_iterval_read_retry() implement a
172 * collision-retry scheme similar to seqcount for the VA range under
173 * subscription. If the mm invokes invalidation during the critical section
174 * then mmu_interval_read_retry() will return true.
176 * This is useful to obtain shadow PTEs where teardown or setup of the SPTEs
177 * require a blocking context. The critical region formed by this can sleep,
178 * and the required 'user_lock' can also be a sleeping lock.
180 * The caller is required to provide a 'user_lock' to serialize both teardown
183 * The return value should be passed to mmu_interval_read_retry().
186 mmu_interval_read_begin(struct mmu_interval_notifier *interval_sub)
188 struct mmu_notifier_subscriptions *subscriptions =
189 interval_sub->mm->notifier_subscriptions;
191 bool is_invalidating;
194 * If the subscription has a different seq value under the user_lock
195 * than we started with then it has collided.
197 * If the subscription currently has the same seq value as the
198 * subscriptions seq, then it is currently between
199 * invalidate_start/end and is colliding.
201 * The locking looks broadly like this:
202 * mn_itree_inv_start(): mmu_interval_read_begin():
204 * seq = READ_ONCE(interval_sub->invalidate_seq);
205 * seq == subs->invalidate_seq
208 * seq = ++subscriptions->invalidate_seq
212 * mmu_interval_set_seq()
213 * interval_sub->invalidate_seq = seq
216 * [Required: mmu_interval_read_retry() == true]
218 * mn_itree_inv_end():
220 * seq = ++subscriptions->invalidate_seq
224 * mmu_interval_read_retry():
225 * interval_sub->invalidate_seq != seq
228 * Barriers are not needed here as any races here are closed by an
229 * eventual mmu_interval_read_retry(), which provides a barrier via the
232 spin_lock(&subscriptions->lock);
233 /* Pairs with the WRITE_ONCE in mmu_interval_set_seq() */
234 seq = READ_ONCE(interval_sub->invalidate_seq);
235 is_invalidating = seq == subscriptions->invalidate_seq;
236 spin_unlock(&subscriptions->lock);
239 * interval_sub->invalidate_seq must always be set to an odd value via
240 * mmu_interval_set_seq() using the provided cur_seq from
241 * mn_itree_inv_start_range(). This ensures that if seq does wrap we
242 * will always clear the below sleep in some reasonable time as
243 * subscriptions->invalidate_seq is even in the idle state.
245 lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
246 lock_map_release(&__mmu_notifier_invalidate_range_start_map);
248 wait_event(subscriptions->wq,
249 READ_ONCE(subscriptions->invalidate_seq) != seq);
252 * Notice that mmu_interval_read_retry() can already be true at this
253 * point, avoiding loops here allows the caller to provide a global
259 EXPORT_SYMBOL_GPL(mmu_interval_read_begin);
261 static void mn_itree_release(struct mmu_notifier_subscriptions *subscriptions,
262 struct mm_struct *mm)
264 struct mmu_notifier_range range = {
265 .flags = MMU_NOTIFIER_RANGE_BLOCKABLE,
266 .event = MMU_NOTIFY_RELEASE,
271 struct mmu_interval_notifier *interval_sub;
272 unsigned long cur_seq;
276 mn_itree_inv_start_range(subscriptions, &range, &cur_seq);
278 interval_sub = mn_itree_inv_next(interval_sub, &range)) {
279 ret = interval_sub->ops->invalidate(interval_sub, &range,
284 mn_itree_inv_end(subscriptions);
288 * This function can't run concurrently against mmu_notifier_register
289 * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
290 * runs with mm_users == 0. Other tasks may still invoke mmu notifiers
291 * in parallel despite there being no task using this mm any more,
292 * through the vmas outside of the exit_mmap context, such as with
293 * vmtruncate. This serializes against mmu_notifier_unregister with
294 * the notifier_subscriptions->lock in addition to SRCU and it serializes
295 * against the other mmu notifiers with SRCU. struct mmu_notifier_subscriptions
296 * can't go away from under us as exit_mmap holds an mm_count pin
299 static void mn_hlist_release(struct mmu_notifier_subscriptions *subscriptions,
300 struct mm_struct *mm)
302 struct mmu_notifier *subscription;
306 * SRCU here will block mmu_notifier_unregister until
309 id = srcu_read_lock(&srcu);
310 hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist,
311 srcu_read_lock_held(&srcu))
313 * If ->release runs before mmu_notifier_unregister it must be
314 * handled, as it's the only way for the driver to flush all
315 * existing sptes and stop the driver from establishing any more
316 * sptes before all the pages in the mm are freed.
318 if (subscription->ops->release)
319 subscription->ops->release(subscription, mm);
321 spin_lock(&subscriptions->lock);
322 while (unlikely(!hlist_empty(&subscriptions->list))) {
323 subscription = hlist_entry(subscriptions->list.first,
324 struct mmu_notifier, hlist);
326 * We arrived before mmu_notifier_unregister so
327 * mmu_notifier_unregister will do nothing other than to wait
328 * for ->release to finish and for mmu_notifier_unregister to
331 hlist_del_init_rcu(&subscription->hlist);
333 spin_unlock(&subscriptions->lock);
334 srcu_read_unlock(&srcu, id);
337 * synchronize_srcu here prevents mmu_notifier_release from returning to
338 * exit_mmap (which would proceed with freeing all pages in the mm)
339 * until the ->release method returns, if it was invoked by
340 * mmu_notifier_unregister.
342 * The notifier_subscriptions can't go away from under us because
343 * one mm_count is held by exit_mmap.
345 synchronize_srcu(&srcu);
348 void __mmu_notifier_release(struct mm_struct *mm)
350 struct mmu_notifier_subscriptions *subscriptions =
351 mm->notifier_subscriptions;
353 if (subscriptions->has_itree)
354 mn_itree_release(subscriptions, mm);
356 if (!hlist_empty(&subscriptions->list))
357 mn_hlist_release(subscriptions, mm);
361 * If no young bitflag is supported by the hardware, ->clear_flush_young can
362 * unmap the address and return 1 or 0 depending if the mapping previously
365 int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
369 struct mmu_notifier *subscription;
372 id = srcu_read_lock(&srcu);
373 hlist_for_each_entry_rcu(subscription,
374 &mm->notifier_subscriptions->list, hlist,
375 srcu_read_lock_held(&srcu)) {
376 if (subscription->ops->clear_flush_young)
377 young |= subscription->ops->clear_flush_young(
378 subscription, mm, start, end);
380 srcu_read_unlock(&srcu, id);
385 int __mmu_notifier_clear_young(struct mm_struct *mm,
389 struct mmu_notifier *subscription;
392 id = srcu_read_lock(&srcu);
393 hlist_for_each_entry_rcu(subscription,
394 &mm->notifier_subscriptions->list, hlist,
395 srcu_read_lock_held(&srcu)) {
396 if (subscription->ops->clear_young)
397 young |= subscription->ops->clear_young(subscription,
400 srcu_read_unlock(&srcu, id);
405 int __mmu_notifier_test_young(struct mm_struct *mm,
406 unsigned long address)
408 struct mmu_notifier *subscription;
411 id = srcu_read_lock(&srcu);
412 hlist_for_each_entry_rcu(subscription,
413 &mm->notifier_subscriptions->list, hlist,
414 srcu_read_lock_held(&srcu)) {
415 if (subscription->ops->test_young) {
416 young = subscription->ops->test_young(subscription, mm,
422 srcu_read_unlock(&srcu, id);
427 void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
430 struct mmu_notifier *subscription;
433 id = srcu_read_lock(&srcu);
434 hlist_for_each_entry_rcu(subscription,
435 &mm->notifier_subscriptions->list, hlist,
436 srcu_read_lock_held(&srcu)) {
437 if (subscription->ops->change_pte)
438 subscription->ops->change_pte(subscription, mm, address,
441 srcu_read_unlock(&srcu, id);
444 static int mn_itree_invalidate(struct mmu_notifier_subscriptions *subscriptions,
445 const struct mmu_notifier_range *range)
447 struct mmu_interval_notifier *interval_sub;
448 unsigned long cur_seq;
451 mn_itree_inv_start_range(subscriptions, range, &cur_seq);
453 interval_sub = mn_itree_inv_next(interval_sub, range)) {
456 ret = interval_sub->ops->invalidate(interval_sub, range,
459 if (WARN_ON(mmu_notifier_range_blockable(range)))
461 goto out_would_block;
468 * On -EAGAIN the non-blocking caller is not allowed to call
469 * invalidate_range_end()
471 mn_itree_inv_end(subscriptions);
475 static int mn_hlist_invalidate_range_start(
476 struct mmu_notifier_subscriptions *subscriptions,
477 struct mmu_notifier_range *range)
479 struct mmu_notifier *subscription;
483 id = srcu_read_lock(&srcu);
484 hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist,
485 srcu_read_lock_held(&srcu)) {
486 const struct mmu_notifier_ops *ops = subscription->ops;
488 if (ops->invalidate_range_start) {
491 if (!mmu_notifier_range_blockable(range))
493 _ret = ops->invalidate_range_start(subscription, range);
494 if (!mmu_notifier_range_blockable(range))
497 pr_info("%pS callback failed with %d in %sblockable context.\n",
498 ops->invalidate_range_start, _ret,
499 !mmu_notifier_range_blockable(range) ?
502 WARN_ON(mmu_notifier_range_blockable(range) ||
505 * We call all the notifiers on any EAGAIN,
506 * there is no way for a notifier to know if
507 * its start method failed, thus a start that
508 * does EAGAIN can't also do end.
510 WARN_ON(ops->invalidate_range_end);
518 * Must be non-blocking to get here. If there are multiple
519 * notifiers and one or more failed start, any that succeeded
520 * start are expecting their end to be called. Do so now.
522 hlist_for_each_entry_rcu(subscription, &subscriptions->list,
523 hlist, srcu_read_lock_held(&srcu)) {
524 if (!subscription->ops->invalidate_range_end)
527 subscription->ops->invalidate_range_end(subscription,
531 srcu_read_unlock(&srcu, id);
536 int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
538 struct mmu_notifier_subscriptions *subscriptions =
539 range->mm->notifier_subscriptions;
542 if (subscriptions->has_itree) {
543 ret = mn_itree_invalidate(subscriptions, range);
547 if (!hlist_empty(&subscriptions->list))
548 return mn_hlist_invalidate_range_start(subscriptions, range);
553 mn_hlist_invalidate_end(struct mmu_notifier_subscriptions *subscriptions,
554 struct mmu_notifier_range *range)
556 struct mmu_notifier *subscription;
559 id = srcu_read_lock(&srcu);
560 hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist,
561 srcu_read_lock_held(&srcu)) {
562 if (subscription->ops->invalidate_range_end) {
563 if (!mmu_notifier_range_blockable(range))
565 subscription->ops->invalidate_range_end(subscription,
567 if (!mmu_notifier_range_blockable(range))
571 srcu_read_unlock(&srcu, id);
574 void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)
576 struct mmu_notifier_subscriptions *subscriptions =
577 range->mm->notifier_subscriptions;
579 lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
580 if (subscriptions->has_itree)
581 mn_itree_inv_end(subscriptions);
583 if (!hlist_empty(&subscriptions->list))
584 mn_hlist_invalidate_end(subscriptions, range);
585 lock_map_release(&__mmu_notifier_invalidate_range_start_map);
588 void __mmu_notifier_invalidate_range(struct mm_struct *mm,
589 unsigned long start, unsigned long end)
591 struct mmu_notifier *subscription;
594 id = srcu_read_lock(&srcu);
595 hlist_for_each_entry_rcu(subscription,
596 &mm->notifier_subscriptions->list, hlist,
597 srcu_read_lock_held(&srcu)) {
598 if (subscription->ops->invalidate_range)
599 subscription->ops->invalidate_range(subscription, mm,
602 srcu_read_unlock(&srcu, id);
606 * Same as mmu_notifier_register but here the caller must hold the mmap_lock in
607 * write mode. A NULL mn signals the notifier is being registered for itree
610 int __mmu_notifier_register(struct mmu_notifier *subscription,
611 struct mm_struct *mm)
613 struct mmu_notifier_subscriptions *subscriptions = NULL;
616 mmap_assert_write_locked(mm);
617 BUG_ON(atomic_read(&mm->mm_users) <= 0);
619 if (!mm->notifier_subscriptions) {
621 * kmalloc cannot be called under mm_take_all_locks(), but we
622 * know that mm->notifier_subscriptions can't change while we
623 * hold the write side of the mmap_lock.
625 subscriptions = kzalloc(
626 sizeof(struct mmu_notifier_subscriptions), GFP_KERNEL);
630 INIT_HLIST_HEAD(&subscriptions->list);
631 spin_lock_init(&subscriptions->lock);
632 subscriptions->invalidate_seq = 2;
633 subscriptions->itree = RB_ROOT_CACHED;
634 init_waitqueue_head(&subscriptions->wq);
635 INIT_HLIST_HEAD(&subscriptions->deferred_list);
638 ret = mm_take_all_locks(mm);
643 * Serialize the update against mmu_notifier_unregister. A
644 * side note: mmu_notifier_release can't run concurrently with
645 * us because we hold the mm_users pin (either implicitly as
646 * current->mm or explicitly with get_task_mm() or similar).
647 * We can't race against any other mmu notifier method either
648 * thanks to mm_take_all_locks().
650 * release semantics on the initialization of the
651 * mmu_notifier_subscriptions's contents are provided for unlocked
652 * readers. acquire can only be used while holding the mmgrab or
653 * mmget, and is safe because once created the
654 * mmu_notifier_subscriptions is not freed until the mm is destroyed.
655 * As above, users holding the mmap_lock or one of the
656 * mm_take_all_locks() do not need to use acquire semantics.
659 smp_store_release(&mm->notifier_subscriptions, subscriptions);
662 /* Pairs with the mmdrop in mmu_notifier_unregister_* */
664 subscription->mm = mm;
665 subscription->users = 1;
667 spin_lock(&mm->notifier_subscriptions->lock);
668 hlist_add_head_rcu(&subscription->hlist,
669 &mm->notifier_subscriptions->list);
670 spin_unlock(&mm->notifier_subscriptions->lock);
672 mm->notifier_subscriptions->has_itree = true;
674 mm_drop_all_locks(mm);
675 BUG_ON(atomic_read(&mm->mm_users) <= 0);
679 kfree(subscriptions);
682 EXPORT_SYMBOL_GPL(__mmu_notifier_register);
685 * mmu_notifier_register - Register a notifier on a mm
686 * @subscription: The notifier to attach
687 * @mm: The mm to attach the notifier to
689 * Must not hold mmap_lock nor any other VM related lock when calling
690 * this registration function. Must also ensure mm_users can't go down
691 * to zero while this runs to avoid races with mmu_notifier_release,
692 * so mm has to be current->mm or the mm should be pinned safely such
693 * as with get_task_mm(). If the mm is not current->mm, the mm_users
694 * pin should be released by calling mmput after mmu_notifier_register
697 * mmu_notifier_unregister() or mmu_notifier_put() must be always called to
698 * unregister the notifier.
700 * While the caller has a mmu_notifier get the subscription->mm pointer will remain
701 * valid, and can be converted to an active mm pointer via mmget_not_zero().
703 int mmu_notifier_register(struct mmu_notifier *subscription,
704 struct mm_struct *mm)
709 ret = __mmu_notifier_register(subscription, mm);
710 mmap_write_unlock(mm);
713 EXPORT_SYMBOL_GPL(mmu_notifier_register);
715 static struct mmu_notifier *
716 find_get_mmu_notifier(struct mm_struct *mm, const struct mmu_notifier_ops *ops)
718 struct mmu_notifier *subscription;
720 spin_lock(&mm->notifier_subscriptions->lock);
721 hlist_for_each_entry_rcu(subscription,
722 &mm->notifier_subscriptions->list, hlist,
723 lockdep_is_held(&mm->notifier_subscriptions->lock)) {
724 if (subscription->ops != ops)
727 if (likely(subscription->users != UINT_MAX))
728 subscription->users++;
730 subscription = ERR_PTR(-EOVERFLOW);
731 spin_unlock(&mm->notifier_subscriptions->lock);
734 spin_unlock(&mm->notifier_subscriptions->lock);
739 * mmu_notifier_get_locked - Return the single struct mmu_notifier for
741 * @ops: The operations struct being subscribe with
742 * @mm : The mm to attach notifiers too
744 * This function either allocates a new mmu_notifier via
745 * ops->alloc_notifier(), or returns an already existing notifier on the
746 * list. The value of the ops pointer is used to determine when two notifiers
749 * Each call to mmu_notifier_get() must be paired with a call to
750 * mmu_notifier_put(). The caller must hold the write side of mm->mmap_lock.
752 * While the caller has a mmu_notifier get the mm pointer will remain valid,
753 * and can be converted to an active mm pointer via mmget_not_zero().
755 struct mmu_notifier *mmu_notifier_get_locked(const struct mmu_notifier_ops *ops,
756 struct mm_struct *mm)
758 struct mmu_notifier *subscription;
761 mmap_assert_write_locked(mm);
763 if (mm->notifier_subscriptions) {
764 subscription = find_get_mmu_notifier(mm, ops);
769 subscription = ops->alloc_notifier(mm);
770 if (IS_ERR(subscription))
772 subscription->ops = ops;
773 ret = __mmu_notifier_register(subscription, mm);
778 subscription->ops->free_notifier(subscription);
781 EXPORT_SYMBOL_GPL(mmu_notifier_get_locked);
783 /* this is called after the last mmu_notifier_unregister() returned */
784 void __mmu_notifier_subscriptions_destroy(struct mm_struct *mm)
786 BUG_ON(!hlist_empty(&mm->notifier_subscriptions->list));
787 kfree(mm->notifier_subscriptions);
788 mm->notifier_subscriptions = LIST_POISON1; /* debug */
792 * This releases the mm_count pin automatically and frees the mm
793 * structure if it was the last user of it. It serializes against
794 * running mmu notifiers with SRCU and against mmu_notifier_unregister
795 * with the unregister lock + SRCU. All sptes must be dropped before
796 * calling mmu_notifier_unregister. ->release or any other notifier
797 * method may be invoked concurrently with mmu_notifier_unregister,
798 * and only after mmu_notifier_unregister returned we're guaranteed
799 * that ->release or any other method can't run anymore.
801 void mmu_notifier_unregister(struct mmu_notifier *subscription,
802 struct mm_struct *mm)
804 BUG_ON(atomic_read(&mm->mm_count) <= 0);
806 if (!hlist_unhashed(&subscription->hlist)) {
808 * SRCU here will force exit_mmap to wait for ->release to
809 * finish before freeing the pages.
813 id = srcu_read_lock(&srcu);
815 * exit_mmap will block in mmu_notifier_release to guarantee
816 * that ->release is called before freeing the pages.
818 if (subscription->ops->release)
819 subscription->ops->release(subscription, mm);
820 srcu_read_unlock(&srcu, id);
822 spin_lock(&mm->notifier_subscriptions->lock);
824 * Can not use list_del_rcu() since __mmu_notifier_release
825 * can delete it before we hold the lock.
827 hlist_del_init_rcu(&subscription->hlist);
828 spin_unlock(&mm->notifier_subscriptions->lock);
832 * Wait for any running method to finish, of course including
833 * ->release if it was run by mmu_notifier_release instead of us.
835 synchronize_srcu(&srcu);
837 BUG_ON(atomic_read(&mm->mm_count) <= 0);
841 EXPORT_SYMBOL_GPL(mmu_notifier_unregister);
843 static void mmu_notifier_free_rcu(struct rcu_head *rcu)
845 struct mmu_notifier *subscription =
846 container_of(rcu, struct mmu_notifier, rcu);
847 struct mm_struct *mm = subscription->mm;
849 subscription->ops->free_notifier(subscription);
850 /* Pairs with the get in __mmu_notifier_register() */
855 * mmu_notifier_put - Release the reference on the notifier
856 * @subscription: The notifier to act on
858 * This function must be paired with each mmu_notifier_get(), it releases the
859 * reference obtained by the get. If this is the last reference then process
860 * to free the notifier will be run asynchronously.
862 * Unlike mmu_notifier_unregister() the get/put flow only calls ops->release
863 * when the mm_struct is destroyed. Instead free_notifier is always called to
864 * release any resources held by the user.
866 * As ops->release is not guaranteed to be called, the user must ensure that
867 * all sptes are dropped, and no new sptes can be established before
868 * mmu_notifier_put() is called.
870 * This function can be called from the ops->release callback, however the
871 * caller must still ensure it is called pairwise with mmu_notifier_get().
873 * Modules calling this function must call mmu_notifier_synchronize() in
874 * their __exit functions to ensure the async work is completed.
876 void mmu_notifier_put(struct mmu_notifier *subscription)
878 struct mm_struct *mm = subscription->mm;
880 spin_lock(&mm->notifier_subscriptions->lock);
881 if (WARN_ON(!subscription->users) || --subscription->users)
883 hlist_del_init_rcu(&subscription->hlist);
884 spin_unlock(&mm->notifier_subscriptions->lock);
886 call_srcu(&srcu, &subscription->rcu, mmu_notifier_free_rcu);
890 spin_unlock(&mm->notifier_subscriptions->lock);
892 EXPORT_SYMBOL_GPL(mmu_notifier_put);
894 static int __mmu_interval_notifier_insert(
895 struct mmu_interval_notifier *interval_sub, struct mm_struct *mm,
896 struct mmu_notifier_subscriptions *subscriptions, unsigned long start,
897 unsigned long length, const struct mmu_interval_notifier_ops *ops)
899 interval_sub->mm = mm;
900 interval_sub->ops = ops;
901 RB_CLEAR_NODE(&interval_sub->interval_tree.rb);
902 interval_sub->interval_tree.start = start;
904 * Note that the representation of the intervals in the interval tree
905 * considers the ending point as contained in the interval.
908 check_add_overflow(start, length - 1,
909 &interval_sub->interval_tree.last))
912 /* Must call with a mmget() held */
913 if (WARN_ON(atomic_read(&mm->mm_users) <= 0))
916 /* pairs with mmdrop in mmu_interval_notifier_remove() */
920 * If some invalidate_range_start/end region is going on in parallel
921 * we don't know what VA ranges are affected, so we must assume this
922 * new range is included.
924 * If the itree is invalidating then we are not allowed to change
925 * it. Retrying until invalidation is done is tricky due to the
926 * possibility for live lock, instead defer the add to
927 * mn_itree_inv_end() so this algorithm is deterministic.
929 * In all cases the value for the interval_sub->invalidate_seq should be
930 * odd, see mmu_interval_read_begin()
932 spin_lock(&subscriptions->lock);
933 if (subscriptions->active_invalidate_ranges) {
934 if (mn_itree_is_invalidating(subscriptions))
935 hlist_add_head(&interval_sub->deferred_item,
936 &subscriptions->deferred_list);
938 subscriptions->invalidate_seq |= 1;
939 interval_tree_insert(&interval_sub->interval_tree,
940 &subscriptions->itree);
942 interval_sub->invalidate_seq = subscriptions->invalidate_seq;
944 WARN_ON(mn_itree_is_invalidating(subscriptions));
946 * The starting seq for a subscription not under invalidation
947 * should be odd, not equal to the current invalidate_seq and
948 * invalidate_seq should not 'wrap' to the new seq any time
951 interval_sub->invalidate_seq =
952 subscriptions->invalidate_seq - 1;
953 interval_tree_insert(&interval_sub->interval_tree,
954 &subscriptions->itree);
956 spin_unlock(&subscriptions->lock);
961 * mmu_interval_notifier_insert - Insert an interval notifier
962 * @interval_sub: Interval subscription to register
963 * @start: Starting virtual address to monitor
964 * @length: Length of the range to monitor
965 * @mm: mm_struct to attach to
966 * @ops: Interval notifier operations to be called on matching events
968 * This function subscribes the interval notifier for notifications from the
969 * mm. Upon return the ops related to mmu_interval_notifier will be called
970 * whenever an event that intersects with the given range occurs.
972 * Upon return the range_notifier may not be present in the interval tree yet.
973 * The caller must use the normal interval notifier read flow via
974 * mmu_interval_read_begin() to establish SPTEs for this range.
976 int mmu_interval_notifier_insert(struct mmu_interval_notifier *interval_sub,
977 struct mm_struct *mm, unsigned long start,
978 unsigned long length,
979 const struct mmu_interval_notifier_ops *ops)
981 struct mmu_notifier_subscriptions *subscriptions;
984 might_lock(&mm->mmap_lock);
986 subscriptions = smp_load_acquire(&mm->notifier_subscriptions);
987 if (!subscriptions || !subscriptions->has_itree) {
988 ret = mmu_notifier_register(NULL, mm);
991 subscriptions = mm->notifier_subscriptions;
993 return __mmu_interval_notifier_insert(interval_sub, mm, subscriptions,
996 EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert);
998 int mmu_interval_notifier_insert_locked(
999 struct mmu_interval_notifier *interval_sub, struct mm_struct *mm,
1000 unsigned long start, unsigned long length,
1001 const struct mmu_interval_notifier_ops *ops)
1003 struct mmu_notifier_subscriptions *subscriptions =
1004 mm->notifier_subscriptions;
1007 mmap_assert_write_locked(mm);
1009 if (!subscriptions || !subscriptions->has_itree) {
1010 ret = __mmu_notifier_register(NULL, mm);
1013 subscriptions = mm->notifier_subscriptions;
1015 return __mmu_interval_notifier_insert(interval_sub, mm, subscriptions,
1016 start, length, ops);
1018 EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert_locked);
1021 mmu_interval_seq_released(struct mmu_notifier_subscriptions *subscriptions,
1026 spin_lock(&subscriptions->lock);
1027 ret = subscriptions->invalidate_seq != seq;
1028 spin_unlock(&subscriptions->lock);
1033 * mmu_interval_notifier_remove - Remove a interval notifier
1034 * @interval_sub: Interval subscription to unregister
1036 * This function must be paired with mmu_interval_notifier_insert(). It cannot
1037 * be called from any ops callback.
1039 * Once this returns ops callbacks are no longer running on other CPUs and
1040 * will not be called in future.
1042 void mmu_interval_notifier_remove(struct mmu_interval_notifier *interval_sub)
1044 struct mm_struct *mm = interval_sub->mm;
1045 struct mmu_notifier_subscriptions *subscriptions =
1046 mm->notifier_subscriptions;
1047 unsigned long seq = 0;
1051 spin_lock(&subscriptions->lock);
1052 if (mn_itree_is_invalidating(subscriptions)) {
1054 * remove is being called after insert put this on the
1055 * deferred list, but before the deferred list was processed.
1057 if (RB_EMPTY_NODE(&interval_sub->interval_tree.rb)) {
1058 hlist_del(&interval_sub->deferred_item);
1060 hlist_add_head(&interval_sub->deferred_item,
1061 &subscriptions->deferred_list);
1062 seq = subscriptions->invalidate_seq;
1065 WARN_ON(RB_EMPTY_NODE(&interval_sub->interval_tree.rb));
1066 interval_tree_remove(&interval_sub->interval_tree,
1067 &subscriptions->itree);
1069 spin_unlock(&subscriptions->lock);
1072 * The possible sleep on progress in the invalidation requires the
1073 * caller not hold any locks held by invalidation callbacks.
1075 lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
1076 lock_map_release(&__mmu_notifier_invalidate_range_start_map);
1078 wait_event(subscriptions->wq,
1079 mmu_interval_seq_released(subscriptions, seq));
1081 /* pairs with mmgrab in mmu_interval_notifier_insert() */
1084 EXPORT_SYMBOL_GPL(mmu_interval_notifier_remove);
1087 * mmu_notifier_synchronize - Ensure all mmu_notifiers are freed
1089 * This function ensures that all outstanding async SRU work from
1090 * mmu_notifier_put() is completed. After it returns any mmu_notifier_ops
1091 * associated with an unused mmu_notifier will no longer be called.
1093 * Before using the caller must ensure that all of its mmu_notifiers have been
1094 * fully released via mmu_notifier_put().
1096 * Modules using the mmu_notifier_put() API should call this in their __exit
1097 * function to avoid module unloading races.
1099 void mmu_notifier_synchronize(void)
1101 synchronize_srcu(&srcu);
1103 EXPORT_SYMBOL_GPL(mmu_notifier_synchronize);