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![Linus Torvalds](/assets/img/avatar_default.png)
This is another round of bug fixing and cleanup. This time the focus is on the driver pattern to use mmu notifiers to monitor a VA range. This code is lifted out of many drivers and hmm_mirror directly into the mmu_notifier core and written using the best ideas from all the driver implementations. This removes many bugs from the drivers and has a very pleasing diffstat. More drivers can still be converted, but that is for another cycle. - A shared branch with RDMA reworking the RDMA ODP implementation - New mmu_interval_notifier API. This is focused on the use case of monitoring a VA and simplifies the process for drivers - A common seq-count locking scheme built into the mmu_interval_notifier API usable by drivers that call get_user_pages() or hmm_range_fault() with the VA range - Conversion of mlx5 ODP, hfi1, radeon, nouveau, AMD GPU, and Xen GntDev drivers to the new API. This deletes a lot of wonky driver code. - Two improvements for hmm_range_fault(), from testing done by Ralph -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEfB7FMLh+8QxL+6i3OG33FX4gmxoFAl3cCjQACgkQOG33FX4g mxpp8xAAiR9iOdT28m/tx1GF31XludrMhRZVIiz0vmCIxIiAkWekWEfAEVm9PDnh wdrxTJohSs+B65AK3sfToOM3AIuNCuFVWmbbHI5qmOO76vaSvcZa905Z++pNsawO Bn8mgRCprYoFHcxWLvTvnA5U0g1S2BSSOwBSZI43CbEnVvHjYAR6MnvRqfGMk+NF bf8fTk/x+fl0DCemhynlBLuJkogzoE2Hgl0yPY5bFna4PktOxdpa1yPaQsiqZ7e6 2s2NtM3pbMBJk0W42q5BU+aPhiqfxFFszasPSLBduXrD2xDsG76HJdHj5VydKmfL nelG4BvqJozXTEZWvTEePYhCqaZ41eJZ7Asw8BXtmacVqE5mDlTXo/Zdgbz7yEOR mI5MVyjD5rauZJldUOWXbwrPoWVFRvboauehiSgqvxvT9HvlFp9GKObSuu4gubBQ mzxs4t48tPhA7bswLmw0/pETSogFuVDfaB7hsyY0gi8EwxMFMpw2qFypm1PEEF+C BuUxCSShzvNKrraNe5PWaNNFd3AzIwAOWJHE+poH4bCoXQVr5nA+rq2gnHkdY5vq /xrBCyxkf0U05YoFGYembPVCInMehzp9Xjy8V+SueSvCg2/TYwGDCgGfsbe9dNOP Bc40JpS7BDn5w9nyLUJmOx7jfruNV6kx1QslA7NDDrB/rzOlsEc= =Hj8a -----END PGP SIGNATURE----- Merge tag 'for-linus-hmm' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma Pull hmm updates from Jason Gunthorpe: "This is another round of bug fixing and cleanup. This time the focus is on the driver pattern to use mmu notifiers to monitor a VA range. This code is lifted out of many drivers and hmm_mirror directly into the mmu_notifier core and written using the best ideas from all the driver implementations. This removes many bugs from the drivers and has a very pleasing diffstat. More drivers can still be converted, but that is for another cycle. - A shared branch with RDMA reworking the RDMA ODP implementation - New mmu_interval_notifier API. This is focused on the use case of monitoring a VA and simplifies the process for drivers - A common seq-count locking scheme built into the mmu_interval_notifier API usable by drivers that call get_user_pages() or hmm_range_fault() with the VA range - Conversion of mlx5 ODP, hfi1, radeon, nouveau, AMD GPU, and Xen GntDev drivers to the new API. This deletes a lot of wonky driver code. - Two improvements for hmm_range_fault(), from testing done by Ralph" * tag 'for-linus-hmm' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma: mm/hmm: remove hmm_range_dma_map and hmm_range_dma_unmap mm/hmm: make full use of walk_page_range() xen/gntdev: use mmu_interval_notifier_insert mm/hmm: remove hmm_mirror and related drm/amdgpu: Use mmu_interval_notifier instead of hmm_mirror drm/amdgpu: Use mmu_interval_insert instead of hmm_mirror drm/amdgpu: Call find_vma under mmap_sem nouveau: use mmu_interval_notifier instead of hmm_mirror nouveau: use mmu_notifier directly for invalidate_range_start drm/radeon: use mmu_interval_notifier_insert RDMA/hfi1: Use mmu_interval_notifier_insert for user_exp_rcv RDMA/odp: Use mmu_interval_notifier_insert() mm/hmm: define the pre-processor related parts of hmm.h even if disabled mm/hmm: allow hmm_range to be used with a mmu_interval_notifier or hmm_mirror mm/mmu_notifier: add an interval tree notifier mm/mmu_notifier: define the header pre-processor parts even if disabled mm/hmm: allow snapshot of the special zero page
1051 lines
31 KiB
C
1051 lines
31 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* linux/mm/mmu_notifier.c
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*
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* Copyright (C) 2008 Qumranet, Inc.
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* Copyright (C) 2008 SGI
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* Christoph Lameter <cl@linux.com>
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*/
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#include <linux/rculist.h>
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#include <linux/mmu_notifier.h>
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#include <linux/export.h>
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#include <linux/mm.h>
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#include <linux/err.h>
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#include <linux/interval_tree.h>
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#include <linux/srcu.h>
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#include <linux/rcupdate.h>
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#include <linux/sched.h>
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#include <linux/sched/mm.h>
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#include <linux/slab.h>
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/* global SRCU for all MMs */
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DEFINE_STATIC_SRCU(srcu);
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#ifdef CONFIG_LOCKDEP
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struct lockdep_map __mmu_notifier_invalidate_range_start_map = {
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.name = "mmu_notifier_invalidate_range_start"
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};
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#endif
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/*
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* The mmu notifier_mm structure is allocated and installed in
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* mm->mmu_notifier_mm inside the mm_take_all_locks() protected
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* critical section and it's released only when mm_count reaches zero
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* in mmdrop().
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*/
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struct mmu_notifier_mm {
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/* all mmu notifiers registered in this mm are queued in this list */
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struct hlist_head list;
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bool has_itree;
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/* to serialize the list modifications and hlist_unhashed */
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spinlock_t lock;
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unsigned long invalidate_seq;
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unsigned long active_invalidate_ranges;
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struct rb_root_cached itree;
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wait_queue_head_t wq;
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struct hlist_head deferred_list;
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};
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/*
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* This is a collision-retry read-side/write-side 'lock', a lot like a
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* seqcount, however this allows multiple write-sides to hold it at
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* once. Conceptually the write side is protecting the values of the PTEs in
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* this mm, such that PTES cannot be read into SPTEs (shadow PTEs) while any
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* writer exists.
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*
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* Note that the core mm creates nested invalidate_range_start()/end() regions
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* within the same thread, and runs invalidate_range_start()/end() in parallel
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* on multiple CPUs. This is designed to not reduce concurrency or block
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* progress on the mm side.
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*
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* As a secondary function, holding the full write side also serves to prevent
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* writers for the itree, this is an optimization to avoid extra locking
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* during invalidate_range_start/end notifiers.
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*
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* The write side has two states, fully excluded:
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* - mm->active_invalidate_ranges != 0
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* - mnn->invalidate_seq & 1 == True (odd)
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* - some range on the mm_struct is being invalidated
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* - the itree is not allowed to change
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*
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* And partially excluded:
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* - mm->active_invalidate_ranges != 0
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* - mnn->invalidate_seq & 1 == False (even)
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* - some range on the mm_struct is being invalidated
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* - the itree is allowed to change
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*
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* Operations on mmu_notifier_mm->invalidate_seq (under spinlock):
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* seq |= 1 # Begin writing
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* seq++ # Release the writing state
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* seq & 1 # True if a writer exists
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*
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* The later state avoids some expensive work on inv_end in the common case of
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* no mni monitoring the VA.
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*/
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static bool mn_itree_is_invalidating(struct mmu_notifier_mm *mmn_mm)
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{
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lockdep_assert_held(&mmn_mm->lock);
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return mmn_mm->invalidate_seq & 1;
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}
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static struct mmu_interval_notifier *
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mn_itree_inv_start_range(struct mmu_notifier_mm *mmn_mm,
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const struct mmu_notifier_range *range,
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unsigned long *seq)
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{
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struct interval_tree_node *node;
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struct mmu_interval_notifier *res = NULL;
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spin_lock(&mmn_mm->lock);
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mmn_mm->active_invalidate_ranges++;
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node = interval_tree_iter_first(&mmn_mm->itree, range->start,
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range->end - 1);
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if (node) {
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mmn_mm->invalidate_seq |= 1;
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res = container_of(node, struct mmu_interval_notifier,
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interval_tree);
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}
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*seq = mmn_mm->invalidate_seq;
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spin_unlock(&mmn_mm->lock);
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return res;
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}
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static struct mmu_interval_notifier *
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mn_itree_inv_next(struct mmu_interval_notifier *mni,
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const struct mmu_notifier_range *range)
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{
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struct interval_tree_node *node;
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node = interval_tree_iter_next(&mni->interval_tree, range->start,
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range->end - 1);
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if (!node)
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return NULL;
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return container_of(node, struct mmu_interval_notifier, interval_tree);
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}
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static void mn_itree_inv_end(struct mmu_notifier_mm *mmn_mm)
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{
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struct mmu_interval_notifier *mni;
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struct hlist_node *next;
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spin_lock(&mmn_mm->lock);
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if (--mmn_mm->active_invalidate_ranges ||
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!mn_itree_is_invalidating(mmn_mm)) {
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spin_unlock(&mmn_mm->lock);
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return;
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}
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/* Make invalidate_seq even */
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mmn_mm->invalidate_seq++;
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/*
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* The inv_end incorporates a deferred mechanism like rtnl_unlock().
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* Adds and removes are queued until the final inv_end happens then
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* they are progressed. This arrangement for tree updates is used to
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* avoid using a blocking lock during invalidate_range_start.
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*/
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hlist_for_each_entry_safe(mni, next, &mmn_mm->deferred_list,
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deferred_item) {
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if (RB_EMPTY_NODE(&mni->interval_tree.rb))
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interval_tree_insert(&mni->interval_tree,
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&mmn_mm->itree);
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else
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interval_tree_remove(&mni->interval_tree,
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&mmn_mm->itree);
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hlist_del(&mni->deferred_item);
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}
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spin_unlock(&mmn_mm->lock);
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wake_up_all(&mmn_mm->wq);
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}
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/**
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* mmu_interval_read_begin - Begin a read side critical section against a VA
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* range
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* mni: The range to use
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*
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* mmu_iterval_read_begin()/mmu_iterval_read_retry() implement a
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* collision-retry scheme similar to seqcount for the VA range under mni. If
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* the mm invokes invalidation during the critical section then
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* mmu_interval_read_retry() will return true.
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*
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* This is useful to obtain shadow PTEs where teardown or setup of the SPTEs
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* require a blocking context. The critical region formed by this can sleep,
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* and the required 'user_lock' can also be a sleeping lock.
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*
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* The caller is required to provide a 'user_lock' to serialize both teardown
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* and setup.
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*
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* The return value should be passed to mmu_interval_read_retry().
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*/
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unsigned long mmu_interval_read_begin(struct mmu_interval_notifier *mni)
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{
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struct mmu_notifier_mm *mmn_mm = mni->mm->mmu_notifier_mm;
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unsigned long seq;
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bool is_invalidating;
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/*
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* If the mni has a different seq value under the user_lock than we
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* started with then it has collided.
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*
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* If the mni currently has the same seq value as the mmn_mm seq, then
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* it is currently between invalidate_start/end and is colliding.
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*
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* The locking looks broadly like this:
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* mn_tree_invalidate_start(): mmu_interval_read_begin():
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* spin_lock
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* seq = READ_ONCE(mni->invalidate_seq);
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* seq == mmn_mm->invalidate_seq
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* spin_unlock
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* spin_lock
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* seq = ++mmn_mm->invalidate_seq
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* spin_unlock
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* op->invalidate_range():
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* user_lock
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* mmu_interval_set_seq()
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* mni->invalidate_seq = seq
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* user_unlock
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*
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* [Required: mmu_interval_read_retry() == true]
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*
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* mn_itree_inv_end():
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* spin_lock
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* seq = ++mmn_mm->invalidate_seq
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* spin_unlock
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*
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* user_lock
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* mmu_interval_read_retry():
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* mni->invalidate_seq != seq
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* user_unlock
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*
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* Barriers are not needed here as any races here are closed by an
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* eventual mmu_interval_read_retry(), which provides a barrier via the
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* user_lock.
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*/
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spin_lock(&mmn_mm->lock);
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/* Pairs with the WRITE_ONCE in mmu_interval_set_seq() */
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seq = READ_ONCE(mni->invalidate_seq);
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is_invalidating = seq == mmn_mm->invalidate_seq;
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spin_unlock(&mmn_mm->lock);
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/*
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* mni->invalidate_seq must always be set to an odd value via
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* mmu_interval_set_seq() using the provided cur_seq from
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* mn_itree_inv_start_range(). This ensures that if seq does wrap we
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* will always clear the below sleep in some reasonable time as
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* mmn_mm->invalidate_seq is even in the idle state.
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*/
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lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
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lock_map_release(&__mmu_notifier_invalidate_range_start_map);
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if (is_invalidating)
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wait_event(mmn_mm->wq,
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READ_ONCE(mmn_mm->invalidate_seq) != seq);
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/*
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* Notice that mmu_interval_read_retry() can already be true at this
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* point, avoiding loops here allows the caller to provide a global
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* time bound.
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*/
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return seq;
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}
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EXPORT_SYMBOL_GPL(mmu_interval_read_begin);
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static void mn_itree_release(struct mmu_notifier_mm *mmn_mm,
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struct mm_struct *mm)
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{
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struct mmu_notifier_range range = {
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.flags = MMU_NOTIFIER_RANGE_BLOCKABLE,
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.event = MMU_NOTIFY_RELEASE,
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.mm = mm,
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.start = 0,
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.end = ULONG_MAX,
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};
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struct mmu_interval_notifier *mni;
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unsigned long cur_seq;
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bool ret;
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for (mni = mn_itree_inv_start_range(mmn_mm, &range, &cur_seq); mni;
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mni = mn_itree_inv_next(mni, &range)) {
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ret = mni->ops->invalidate(mni, &range, cur_seq);
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WARN_ON(!ret);
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}
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mn_itree_inv_end(mmn_mm);
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}
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/*
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* This function can't run concurrently against mmu_notifier_register
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* because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
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* runs with mm_users == 0. Other tasks may still invoke mmu notifiers
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* in parallel despite there being no task using this mm any more,
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* through the vmas outside of the exit_mmap context, such as with
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* vmtruncate. This serializes against mmu_notifier_unregister with
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* the mmu_notifier_mm->lock in addition to SRCU and it serializes
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* against the other mmu notifiers with SRCU. struct mmu_notifier_mm
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* can't go away from under us as exit_mmap holds an mm_count pin
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* itself.
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*/
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static void mn_hlist_release(struct mmu_notifier_mm *mmn_mm,
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struct mm_struct *mm)
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{
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struct mmu_notifier *mn;
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int id;
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/*
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* SRCU here will block mmu_notifier_unregister until
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* ->release returns.
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*/
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mmn_mm->list, hlist)
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/*
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* If ->release runs before mmu_notifier_unregister it must be
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* handled, as it's the only way for the driver to flush all
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* existing sptes and stop the driver from establishing any more
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* sptes before all the pages in the mm are freed.
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*/
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if (mn->ops->release)
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mn->ops->release(mn, mm);
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spin_lock(&mmn_mm->lock);
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while (unlikely(!hlist_empty(&mmn_mm->list))) {
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mn = hlist_entry(mmn_mm->list.first, struct mmu_notifier,
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hlist);
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/*
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* We arrived before mmu_notifier_unregister so
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* mmu_notifier_unregister will do nothing other than to wait
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* for ->release to finish and for mmu_notifier_unregister to
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* return.
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*/
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hlist_del_init_rcu(&mn->hlist);
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}
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spin_unlock(&mmn_mm->lock);
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srcu_read_unlock(&srcu, id);
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/*
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* synchronize_srcu here prevents mmu_notifier_release from returning to
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* exit_mmap (which would proceed with freeing all pages in the mm)
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* until the ->release method returns, if it was invoked by
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* mmu_notifier_unregister.
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*
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* The mmu_notifier_mm can't go away from under us because one mm_count
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* is held by exit_mmap.
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*/
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synchronize_srcu(&srcu);
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}
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void __mmu_notifier_release(struct mm_struct *mm)
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{
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struct mmu_notifier_mm *mmn_mm = mm->mmu_notifier_mm;
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if (mmn_mm->has_itree)
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mn_itree_release(mmn_mm, mm);
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if (!hlist_empty(&mmn_mm->list))
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mn_hlist_release(mmn_mm, mm);
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}
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/*
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* If no young bitflag is supported by the hardware, ->clear_flush_young can
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* unmap the address and return 1 or 0 depending if the mapping previously
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* existed or not.
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*/
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int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
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unsigned long start,
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unsigned long end)
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{
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struct mmu_notifier *mn;
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int young = 0, id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->clear_flush_young)
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young |= mn->ops->clear_flush_young(mn, mm, start, end);
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}
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srcu_read_unlock(&srcu, id);
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return young;
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}
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int __mmu_notifier_clear_young(struct mm_struct *mm,
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unsigned long start,
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unsigned long end)
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{
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struct mmu_notifier *mn;
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int young = 0, id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->clear_young)
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young |= mn->ops->clear_young(mn, mm, start, end);
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}
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srcu_read_unlock(&srcu, id);
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return young;
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}
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int __mmu_notifier_test_young(struct mm_struct *mm,
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unsigned long address)
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{
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struct mmu_notifier *mn;
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int young = 0, id;
|
|
|
|
id = srcu_read_lock(&srcu);
|
|
hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
|
|
if (mn->ops->test_young) {
|
|
young = mn->ops->test_young(mn, mm, address);
|
|
if (young)
|
|
break;
|
|
}
|
|
}
|
|
srcu_read_unlock(&srcu, id);
|
|
|
|
return young;
|
|
}
|
|
|
|
void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
|
|
pte_t pte)
|
|
{
|
|
struct mmu_notifier *mn;
|
|
int id;
|
|
|
|
id = srcu_read_lock(&srcu);
|
|
hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
|
|
if (mn->ops->change_pte)
|
|
mn->ops->change_pte(mn, mm, address, pte);
|
|
}
|
|
srcu_read_unlock(&srcu, id);
|
|
}
|
|
|
|
static int mn_itree_invalidate(struct mmu_notifier_mm *mmn_mm,
|
|
const struct mmu_notifier_range *range)
|
|
{
|
|
struct mmu_interval_notifier *mni;
|
|
unsigned long cur_seq;
|
|
|
|
for (mni = mn_itree_inv_start_range(mmn_mm, range, &cur_seq); mni;
|
|
mni = mn_itree_inv_next(mni, range)) {
|
|
bool ret;
|
|
|
|
ret = mni->ops->invalidate(mni, range, cur_seq);
|
|
if (!ret) {
|
|
if (WARN_ON(mmu_notifier_range_blockable(range)))
|
|
continue;
|
|
goto out_would_block;
|
|
}
|
|
}
|
|
return 0;
|
|
|
|
out_would_block:
|
|
/*
|
|
* On -EAGAIN the non-blocking caller is not allowed to call
|
|
* invalidate_range_end()
|
|
*/
|
|
mn_itree_inv_end(mmn_mm);
|
|
return -EAGAIN;
|
|
}
|
|
|
|
static int mn_hlist_invalidate_range_start(struct mmu_notifier_mm *mmn_mm,
|
|
struct mmu_notifier_range *range)
|
|
{
|
|
struct mmu_notifier *mn;
|
|
int ret = 0;
|
|
int id;
|
|
|
|
id = srcu_read_lock(&srcu);
|
|
hlist_for_each_entry_rcu(mn, &mmn_mm->list, hlist) {
|
|
if (mn->ops->invalidate_range_start) {
|
|
int _ret;
|
|
|
|
if (!mmu_notifier_range_blockable(range))
|
|
non_block_start();
|
|
_ret = mn->ops->invalidate_range_start(mn, range);
|
|
if (!mmu_notifier_range_blockable(range))
|
|
non_block_end();
|
|
if (_ret) {
|
|
pr_info("%pS callback failed with %d in %sblockable context.\n",
|
|
mn->ops->invalidate_range_start, _ret,
|
|
!mmu_notifier_range_blockable(range) ? "non-" : "");
|
|
WARN_ON(mmu_notifier_range_blockable(range) ||
|
|
_ret != -EAGAIN);
|
|
ret = _ret;
|
|
}
|
|
}
|
|
}
|
|
srcu_read_unlock(&srcu, id);
|
|
|
|
return ret;
|
|
}
|
|
|
|
int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
|
|
{
|
|
struct mmu_notifier_mm *mmn_mm = range->mm->mmu_notifier_mm;
|
|
int ret;
|
|
|
|
if (mmn_mm->has_itree) {
|
|
ret = mn_itree_invalidate(mmn_mm, range);
|
|
if (ret)
|
|
return ret;
|
|
}
|
|
if (!hlist_empty(&mmn_mm->list))
|
|
return mn_hlist_invalidate_range_start(mmn_mm, range);
|
|
return 0;
|
|
}
|
|
|
|
static void mn_hlist_invalidate_end(struct mmu_notifier_mm *mmn_mm,
|
|
struct mmu_notifier_range *range,
|
|
bool only_end)
|
|
{
|
|
struct mmu_notifier *mn;
|
|
int id;
|
|
|
|
id = srcu_read_lock(&srcu);
|
|
hlist_for_each_entry_rcu(mn, &mmn_mm->list, hlist) {
|
|
/*
|
|
* Call invalidate_range here too to avoid the need for the
|
|
* subsystem of having to register an invalidate_range_end
|
|
* call-back when there is invalidate_range already. Usually a
|
|
* subsystem registers either invalidate_range_start()/end() or
|
|
* invalidate_range(), so this will be no additional overhead
|
|
* (besides the pointer check).
|
|
*
|
|
* We skip call to invalidate_range() if we know it is safe ie
|
|
* call site use mmu_notifier_invalidate_range_only_end() which
|
|
* is safe to do when we know that a call to invalidate_range()
|
|
* already happen under page table lock.
|
|
*/
|
|
if (!only_end && mn->ops->invalidate_range)
|
|
mn->ops->invalidate_range(mn, range->mm,
|
|
range->start,
|
|
range->end);
|
|
if (mn->ops->invalidate_range_end) {
|
|
if (!mmu_notifier_range_blockable(range))
|
|
non_block_start();
|
|
mn->ops->invalidate_range_end(mn, range);
|
|
if (!mmu_notifier_range_blockable(range))
|
|
non_block_end();
|
|
}
|
|
}
|
|
srcu_read_unlock(&srcu, id);
|
|
}
|
|
|
|
void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range,
|
|
bool only_end)
|
|
{
|
|
struct mmu_notifier_mm *mmn_mm = range->mm->mmu_notifier_mm;
|
|
|
|
lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
|
|
if (mmn_mm->has_itree)
|
|
mn_itree_inv_end(mmn_mm);
|
|
|
|
if (!hlist_empty(&mmn_mm->list))
|
|
mn_hlist_invalidate_end(mmn_mm, range, only_end);
|
|
lock_map_release(&__mmu_notifier_invalidate_range_start_map);
|
|
}
|
|
|
|
void __mmu_notifier_invalidate_range(struct mm_struct *mm,
|
|
unsigned long start, unsigned long end)
|
|
{
|
|
struct mmu_notifier *mn;
|
|
int id;
|
|
|
|
id = srcu_read_lock(&srcu);
|
|
hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
|
|
if (mn->ops->invalidate_range)
|
|
mn->ops->invalidate_range(mn, mm, start, end);
|
|
}
|
|
srcu_read_unlock(&srcu, id);
|
|
}
|
|
|
|
/*
|
|
* Same as mmu_notifier_register but here the caller must hold the mmap_sem in
|
|
* write mode. A NULL mn signals the notifier is being registered for itree
|
|
* mode.
|
|
*/
|
|
int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
|
|
{
|
|
struct mmu_notifier_mm *mmu_notifier_mm = NULL;
|
|
int ret;
|
|
|
|
lockdep_assert_held_write(&mm->mmap_sem);
|
|
BUG_ON(atomic_read(&mm->mm_users) <= 0);
|
|
|
|
if (IS_ENABLED(CONFIG_LOCKDEP)) {
|
|
fs_reclaim_acquire(GFP_KERNEL);
|
|
lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
|
|
lock_map_release(&__mmu_notifier_invalidate_range_start_map);
|
|
fs_reclaim_release(GFP_KERNEL);
|
|
}
|
|
|
|
if (!mm->mmu_notifier_mm) {
|
|
/*
|
|
* kmalloc cannot be called under mm_take_all_locks(), but we
|
|
* know that mm->mmu_notifier_mm can't change while we hold
|
|
* the write side of the mmap_sem.
|
|
*/
|
|
mmu_notifier_mm =
|
|
kzalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
|
|
if (!mmu_notifier_mm)
|
|
return -ENOMEM;
|
|
|
|
INIT_HLIST_HEAD(&mmu_notifier_mm->list);
|
|
spin_lock_init(&mmu_notifier_mm->lock);
|
|
mmu_notifier_mm->invalidate_seq = 2;
|
|
mmu_notifier_mm->itree = RB_ROOT_CACHED;
|
|
init_waitqueue_head(&mmu_notifier_mm->wq);
|
|
INIT_HLIST_HEAD(&mmu_notifier_mm->deferred_list);
|
|
}
|
|
|
|
ret = mm_take_all_locks(mm);
|
|
if (unlikely(ret))
|
|
goto out_clean;
|
|
|
|
/*
|
|
* Serialize the update against mmu_notifier_unregister. A
|
|
* side note: mmu_notifier_release can't run concurrently with
|
|
* us because we hold the mm_users pin (either implicitly as
|
|
* current->mm or explicitly with get_task_mm() or similar).
|
|
* We can't race against any other mmu notifier method either
|
|
* thanks to mm_take_all_locks().
|
|
*
|
|
* release semantics on the initialization of the mmu_notifier_mm's
|
|
* contents are provided for unlocked readers. acquire can only be
|
|
* used while holding the mmgrab or mmget, and is safe because once
|
|
* created the mmu_notififer_mm is not freed until the mm is
|
|
* destroyed. As above, users holding the mmap_sem or one of the
|
|
* mm_take_all_locks() do not need to use acquire semantics.
|
|
*/
|
|
if (mmu_notifier_mm)
|
|
smp_store_release(&mm->mmu_notifier_mm, mmu_notifier_mm);
|
|
|
|
if (mn) {
|
|
/* Pairs with the mmdrop in mmu_notifier_unregister_* */
|
|
mmgrab(mm);
|
|
mn->mm = mm;
|
|
mn->users = 1;
|
|
|
|
spin_lock(&mm->mmu_notifier_mm->lock);
|
|
hlist_add_head_rcu(&mn->hlist, &mm->mmu_notifier_mm->list);
|
|
spin_unlock(&mm->mmu_notifier_mm->lock);
|
|
} else
|
|
mm->mmu_notifier_mm->has_itree = true;
|
|
|
|
mm_drop_all_locks(mm);
|
|
BUG_ON(atomic_read(&mm->mm_users) <= 0);
|
|
return 0;
|
|
|
|
out_clean:
|
|
kfree(mmu_notifier_mm);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__mmu_notifier_register);
|
|
|
|
/**
|
|
* mmu_notifier_register - Register a notifier on a mm
|
|
* @mn: The notifier to attach
|
|
* @mm: The mm to attach the notifier to
|
|
*
|
|
* Must not hold mmap_sem nor any other VM related lock when calling
|
|
* this registration function. Must also ensure mm_users can't go down
|
|
* to zero while this runs to avoid races with mmu_notifier_release,
|
|
* so mm has to be current->mm or the mm should be pinned safely such
|
|
* as with get_task_mm(). If the mm is not current->mm, the mm_users
|
|
* pin should be released by calling mmput after mmu_notifier_register
|
|
* returns.
|
|
*
|
|
* mmu_notifier_unregister() or mmu_notifier_put() must be always called to
|
|
* unregister the notifier.
|
|
*
|
|
* While the caller has a mmu_notifier get the mn->mm pointer will remain
|
|
* valid, and can be converted to an active mm pointer via mmget_not_zero().
|
|
*/
|
|
int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
|
|
{
|
|
int ret;
|
|
|
|
down_write(&mm->mmap_sem);
|
|
ret = __mmu_notifier_register(mn, mm);
|
|
up_write(&mm->mmap_sem);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_notifier_register);
|
|
|
|
static struct mmu_notifier *
|
|
find_get_mmu_notifier(struct mm_struct *mm, const struct mmu_notifier_ops *ops)
|
|
{
|
|
struct mmu_notifier *mn;
|
|
|
|
spin_lock(&mm->mmu_notifier_mm->lock);
|
|
hlist_for_each_entry_rcu (mn, &mm->mmu_notifier_mm->list, hlist) {
|
|
if (mn->ops != ops)
|
|
continue;
|
|
|
|
if (likely(mn->users != UINT_MAX))
|
|
mn->users++;
|
|
else
|
|
mn = ERR_PTR(-EOVERFLOW);
|
|
spin_unlock(&mm->mmu_notifier_mm->lock);
|
|
return mn;
|
|
}
|
|
spin_unlock(&mm->mmu_notifier_mm->lock);
|
|
return NULL;
|
|
}
|
|
|
|
/**
|
|
* mmu_notifier_get_locked - Return the single struct mmu_notifier for
|
|
* the mm & ops
|
|
* @ops: The operations struct being subscribe with
|
|
* @mm : The mm to attach notifiers too
|
|
*
|
|
* This function either allocates a new mmu_notifier via
|
|
* ops->alloc_notifier(), or returns an already existing notifier on the
|
|
* list. The value of the ops pointer is used to determine when two notifiers
|
|
* are the same.
|
|
*
|
|
* Each call to mmu_notifier_get() must be paired with a call to
|
|
* mmu_notifier_put(). The caller must hold the write side of mm->mmap_sem.
|
|
*
|
|
* While the caller has a mmu_notifier get the mm pointer will remain valid,
|
|
* and can be converted to an active mm pointer via mmget_not_zero().
|
|
*/
|
|
struct mmu_notifier *mmu_notifier_get_locked(const struct mmu_notifier_ops *ops,
|
|
struct mm_struct *mm)
|
|
{
|
|
struct mmu_notifier *mn;
|
|
int ret;
|
|
|
|
lockdep_assert_held_write(&mm->mmap_sem);
|
|
|
|
if (mm->mmu_notifier_mm) {
|
|
mn = find_get_mmu_notifier(mm, ops);
|
|
if (mn)
|
|
return mn;
|
|
}
|
|
|
|
mn = ops->alloc_notifier(mm);
|
|
if (IS_ERR(mn))
|
|
return mn;
|
|
mn->ops = ops;
|
|
ret = __mmu_notifier_register(mn, mm);
|
|
if (ret)
|
|
goto out_free;
|
|
return mn;
|
|
out_free:
|
|
mn->ops->free_notifier(mn);
|
|
return ERR_PTR(ret);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_notifier_get_locked);
|
|
|
|
/* this is called after the last mmu_notifier_unregister() returned */
|
|
void __mmu_notifier_mm_destroy(struct mm_struct *mm)
|
|
{
|
|
BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list));
|
|
kfree(mm->mmu_notifier_mm);
|
|
mm->mmu_notifier_mm = LIST_POISON1; /* debug */
|
|
}
|
|
|
|
/*
|
|
* This releases the mm_count pin automatically and frees the mm
|
|
* structure if it was the last user of it. It serializes against
|
|
* running mmu notifiers with SRCU and against mmu_notifier_unregister
|
|
* with the unregister lock + SRCU. All sptes must be dropped before
|
|
* calling mmu_notifier_unregister. ->release or any other notifier
|
|
* method may be invoked concurrently with mmu_notifier_unregister,
|
|
* and only after mmu_notifier_unregister returned we're guaranteed
|
|
* that ->release or any other method can't run anymore.
|
|
*/
|
|
void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
|
|
{
|
|
BUG_ON(atomic_read(&mm->mm_count) <= 0);
|
|
|
|
if (!hlist_unhashed(&mn->hlist)) {
|
|
/*
|
|
* SRCU here will force exit_mmap to wait for ->release to
|
|
* finish before freeing the pages.
|
|
*/
|
|
int id;
|
|
|
|
id = srcu_read_lock(&srcu);
|
|
/*
|
|
* exit_mmap will block in mmu_notifier_release to guarantee
|
|
* that ->release is called before freeing the pages.
|
|
*/
|
|
if (mn->ops->release)
|
|
mn->ops->release(mn, mm);
|
|
srcu_read_unlock(&srcu, id);
|
|
|
|
spin_lock(&mm->mmu_notifier_mm->lock);
|
|
/*
|
|
* Can not use list_del_rcu() since __mmu_notifier_release
|
|
* can delete it before we hold the lock.
|
|
*/
|
|
hlist_del_init_rcu(&mn->hlist);
|
|
spin_unlock(&mm->mmu_notifier_mm->lock);
|
|
}
|
|
|
|
/*
|
|
* Wait for any running method to finish, of course including
|
|
* ->release if it was run by mmu_notifier_release instead of us.
|
|
*/
|
|
synchronize_srcu(&srcu);
|
|
|
|
BUG_ON(atomic_read(&mm->mm_count) <= 0);
|
|
|
|
mmdrop(mm);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_notifier_unregister);
|
|
|
|
static void mmu_notifier_free_rcu(struct rcu_head *rcu)
|
|
{
|
|
struct mmu_notifier *mn = container_of(rcu, struct mmu_notifier, rcu);
|
|
struct mm_struct *mm = mn->mm;
|
|
|
|
mn->ops->free_notifier(mn);
|
|
/* Pairs with the get in __mmu_notifier_register() */
|
|
mmdrop(mm);
|
|
}
|
|
|
|
/**
|
|
* mmu_notifier_put - Release the reference on the notifier
|
|
* @mn: The notifier to act on
|
|
*
|
|
* This function must be paired with each mmu_notifier_get(), it releases the
|
|
* reference obtained by the get. If this is the last reference then process
|
|
* to free the notifier will be run asynchronously.
|
|
*
|
|
* Unlike mmu_notifier_unregister() the get/put flow only calls ops->release
|
|
* when the mm_struct is destroyed. Instead free_notifier is always called to
|
|
* release any resources held by the user.
|
|
*
|
|
* As ops->release is not guaranteed to be called, the user must ensure that
|
|
* all sptes are dropped, and no new sptes can be established before
|
|
* mmu_notifier_put() is called.
|
|
*
|
|
* This function can be called from the ops->release callback, however the
|
|
* caller must still ensure it is called pairwise with mmu_notifier_get().
|
|
*
|
|
* Modules calling this function must call mmu_notifier_synchronize() in
|
|
* their __exit functions to ensure the async work is completed.
|
|
*/
|
|
void mmu_notifier_put(struct mmu_notifier *mn)
|
|
{
|
|
struct mm_struct *mm = mn->mm;
|
|
|
|
spin_lock(&mm->mmu_notifier_mm->lock);
|
|
if (WARN_ON(!mn->users) || --mn->users)
|
|
goto out_unlock;
|
|
hlist_del_init_rcu(&mn->hlist);
|
|
spin_unlock(&mm->mmu_notifier_mm->lock);
|
|
|
|
call_srcu(&srcu, &mn->rcu, mmu_notifier_free_rcu);
|
|
return;
|
|
|
|
out_unlock:
|
|
spin_unlock(&mm->mmu_notifier_mm->lock);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_notifier_put);
|
|
|
|
static int __mmu_interval_notifier_insert(
|
|
struct mmu_interval_notifier *mni, struct mm_struct *mm,
|
|
struct mmu_notifier_mm *mmn_mm, unsigned long start,
|
|
unsigned long length, const struct mmu_interval_notifier_ops *ops)
|
|
{
|
|
mni->mm = mm;
|
|
mni->ops = ops;
|
|
RB_CLEAR_NODE(&mni->interval_tree.rb);
|
|
mni->interval_tree.start = start;
|
|
/*
|
|
* Note that the representation of the intervals in the interval tree
|
|
* considers the ending point as contained in the interval.
|
|
*/
|
|
if (length == 0 ||
|
|
check_add_overflow(start, length - 1, &mni->interval_tree.last))
|
|
return -EOVERFLOW;
|
|
|
|
/* Must call with a mmget() held */
|
|
if (WARN_ON(atomic_read(&mm->mm_count) <= 0))
|
|
return -EINVAL;
|
|
|
|
/* pairs with mmdrop in mmu_interval_notifier_remove() */
|
|
mmgrab(mm);
|
|
|
|
/*
|
|
* If some invalidate_range_start/end region is going on in parallel
|
|
* we don't know what VA ranges are affected, so we must assume this
|
|
* new range is included.
|
|
*
|
|
* If the itree is invalidating then we are not allowed to change
|
|
* it. Retrying until invalidation is done is tricky due to the
|
|
* possibility for live lock, instead defer the add to
|
|
* mn_itree_inv_end() so this algorithm is deterministic.
|
|
*
|
|
* In all cases the value for the mni->invalidate_seq should be
|
|
* odd, see mmu_interval_read_begin()
|
|
*/
|
|
spin_lock(&mmn_mm->lock);
|
|
if (mmn_mm->active_invalidate_ranges) {
|
|
if (mn_itree_is_invalidating(mmn_mm))
|
|
hlist_add_head(&mni->deferred_item,
|
|
&mmn_mm->deferred_list);
|
|
else {
|
|
mmn_mm->invalidate_seq |= 1;
|
|
interval_tree_insert(&mni->interval_tree,
|
|
&mmn_mm->itree);
|
|
}
|
|
mni->invalidate_seq = mmn_mm->invalidate_seq;
|
|
} else {
|
|
WARN_ON(mn_itree_is_invalidating(mmn_mm));
|
|
/*
|
|
* The starting seq for a mni not under invalidation should be
|
|
* odd, not equal to the current invalidate_seq and
|
|
* invalidate_seq should not 'wrap' to the new seq any time
|
|
* soon.
|
|
*/
|
|
mni->invalidate_seq = mmn_mm->invalidate_seq - 1;
|
|
interval_tree_insert(&mni->interval_tree, &mmn_mm->itree);
|
|
}
|
|
spin_unlock(&mmn_mm->lock);
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* mmu_interval_notifier_insert - Insert an interval notifier
|
|
* @mni: Interval notifier to register
|
|
* @start: Starting virtual address to monitor
|
|
* @length: Length of the range to monitor
|
|
* @mm : mm_struct to attach to
|
|
*
|
|
* This function subscribes the interval notifier for notifications from the
|
|
* mm. Upon return the ops related to mmu_interval_notifier will be called
|
|
* whenever an event that intersects with the given range occurs.
|
|
*
|
|
* Upon return the range_notifier may not be present in the interval tree yet.
|
|
* The caller must use the normal interval notifier read flow via
|
|
* mmu_interval_read_begin() to establish SPTEs for this range.
|
|
*/
|
|
int mmu_interval_notifier_insert(struct mmu_interval_notifier *mni,
|
|
struct mm_struct *mm, unsigned long start,
|
|
unsigned long length,
|
|
const struct mmu_interval_notifier_ops *ops)
|
|
{
|
|
struct mmu_notifier_mm *mmn_mm;
|
|
int ret;
|
|
|
|
might_lock(&mm->mmap_sem);
|
|
|
|
mmn_mm = smp_load_acquire(&mm->mmu_notifier_mm);
|
|
if (!mmn_mm || !mmn_mm->has_itree) {
|
|
ret = mmu_notifier_register(NULL, mm);
|
|
if (ret)
|
|
return ret;
|
|
mmn_mm = mm->mmu_notifier_mm;
|
|
}
|
|
return __mmu_interval_notifier_insert(mni, mm, mmn_mm, start, length,
|
|
ops);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert);
|
|
|
|
int mmu_interval_notifier_insert_locked(
|
|
struct mmu_interval_notifier *mni, struct mm_struct *mm,
|
|
unsigned long start, unsigned long length,
|
|
const struct mmu_interval_notifier_ops *ops)
|
|
{
|
|
struct mmu_notifier_mm *mmn_mm;
|
|
int ret;
|
|
|
|
lockdep_assert_held_write(&mm->mmap_sem);
|
|
|
|
mmn_mm = mm->mmu_notifier_mm;
|
|
if (!mmn_mm || !mmn_mm->has_itree) {
|
|
ret = __mmu_notifier_register(NULL, mm);
|
|
if (ret)
|
|
return ret;
|
|
mmn_mm = mm->mmu_notifier_mm;
|
|
}
|
|
return __mmu_interval_notifier_insert(mni, mm, mmn_mm, start, length,
|
|
ops);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert_locked);
|
|
|
|
/**
|
|
* mmu_interval_notifier_remove - Remove a interval notifier
|
|
* @mni: Interval notifier to unregister
|
|
*
|
|
* This function must be paired with mmu_interval_notifier_insert(). It cannot
|
|
* be called from any ops callback.
|
|
*
|
|
* Once this returns ops callbacks are no longer running on other CPUs and
|
|
* will not be called in future.
|
|
*/
|
|
void mmu_interval_notifier_remove(struct mmu_interval_notifier *mni)
|
|
{
|
|
struct mm_struct *mm = mni->mm;
|
|
struct mmu_notifier_mm *mmn_mm = mm->mmu_notifier_mm;
|
|
unsigned long seq = 0;
|
|
|
|
might_sleep();
|
|
|
|
spin_lock(&mmn_mm->lock);
|
|
if (mn_itree_is_invalidating(mmn_mm)) {
|
|
/*
|
|
* remove is being called after insert put this on the
|
|
* deferred list, but before the deferred list was processed.
|
|
*/
|
|
if (RB_EMPTY_NODE(&mni->interval_tree.rb)) {
|
|
hlist_del(&mni->deferred_item);
|
|
} else {
|
|
hlist_add_head(&mni->deferred_item,
|
|
&mmn_mm->deferred_list);
|
|
seq = mmn_mm->invalidate_seq;
|
|
}
|
|
} else {
|
|
WARN_ON(RB_EMPTY_NODE(&mni->interval_tree.rb));
|
|
interval_tree_remove(&mni->interval_tree, &mmn_mm->itree);
|
|
}
|
|
spin_unlock(&mmn_mm->lock);
|
|
|
|
/*
|
|
* The possible sleep on progress in the invalidation requires the
|
|
* caller not hold any locks held by invalidation callbacks.
|
|
*/
|
|
lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
|
|
lock_map_release(&__mmu_notifier_invalidate_range_start_map);
|
|
if (seq)
|
|
wait_event(mmn_mm->wq,
|
|
READ_ONCE(mmn_mm->invalidate_seq) != seq);
|
|
|
|
/* pairs with mmgrab in mmu_interval_notifier_insert() */
|
|
mmdrop(mm);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_interval_notifier_remove);
|
|
|
|
/**
|
|
* mmu_notifier_synchronize - Ensure all mmu_notifiers are freed
|
|
*
|
|
* This function ensures that all outstanding async SRU work from
|
|
* mmu_notifier_put() is completed. After it returns any mmu_notifier_ops
|
|
* associated with an unused mmu_notifier will no longer be called.
|
|
*
|
|
* Before using the caller must ensure that all of its mmu_notifiers have been
|
|
* fully released via mmu_notifier_put().
|
|
*
|
|
* Modules using the mmu_notifier_put() API should call this in their __exit
|
|
* function to avoid module unloading races.
|
|
*/
|
|
void mmu_notifier_synchronize(void)
|
|
{
|
|
synchronize_srcu(&srcu);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_notifier_synchronize);
|
|
|
|
bool
|
|
mmu_notifier_range_update_to_read_only(const struct mmu_notifier_range *range)
|
|
{
|
|
if (!range->vma || range->event != MMU_NOTIFY_PROTECTION_VMA)
|
|
return false;
|
|
/* Return true if the vma still have the read flag set. */
|
|
return range->vma->vm_flags & VM_READ;
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_notifier_range_update_to_read_only);
|