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![Alistair Popple](/assets/img/avatar_default.png)
There are two main use cases for mmu notifiers. One is by KVM which uses mmu_notifier_invalidate_range_start()/end() to manage a software TLB. The other is to manage hardware TLBs which need to use the invalidate_range() callback because HW can establish new TLB entries at any time. Hence using start/end() can lead to memory corruption as these callbacks happen too soon/late during page unmap. mmu notifier users should therefore either use the start()/end() callbacks or the invalidate_range() callbacks. To make this usage clearer rename the invalidate_range() callback to arch_invalidate_secondary_tlbs() and update documention. Link: https://lkml.kernel.org/r/6f77248cd25545c8020a54b4e567e8b72be4dca1.1690292440.git-series.apopple@nvidia.com Signed-off-by: Alistair Popple <apopple@nvidia.com> Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Cc: Andrew Donnellan <ajd@linux.ibm.com> Cc: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com> Cc: Frederic Barrat <fbarrat@linux.ibm.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Kevin Tian <kevin.tian@intel.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Nicolin Chen <nicolinc@nvidia.com> Cc: Robin Murphy <robin.murphy@arm.com> Cc: Sean Christopherson <seanjc@google.com> Cc: SeongJae Park <sj@kernel.org> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> Cc: Will Deacon <will@kernel.org> Cc: Zhi Wang <zhi.wang.linux@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
1114 lines
34 KiB
C
1114 lines
34 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_subscriptions structure is allocated and installed in
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* mm->notifier_subscriptions 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_subscriptions {
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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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* - subscriptions->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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* - subscriptions->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 notifier_subscriptions->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 mmu_interval_notifier monitoring the VA.
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*/
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static bool
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mn_itree_is_invalidating(struct mmu_notifier_subscriptions *subscriptions)
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{
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lockdep_assert_held(&subscriptions->lock);
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return subscriptions->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_subscriptions *subscriptions,
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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(&subscriptions->lock);
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subscriptions->active_invalidate_ranges++;
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node = interval_tree_iter_first(&subscriptions->itree, range->start,
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range->end - 1);
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if (node) {
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subscriptions->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 = subscriptions->invalidate_seq;
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spin_unlock(&subscriptions->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 *interval_sub,
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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(&interval_sub->interval_tree,
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range->start, 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_subscriptions *subscriptions)
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{
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struct mmu_interval_notifier *interval_sub;
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struct hlist_node *next;
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spin_lock(&subscriptions->lock);
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if (--subscriptions->active_invalidate_ranges ||
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!mn_itree_is_invalidating(subscriptions)) {
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spin_unlock(&subscriptions->lock);
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return;
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}
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/* Make invalidate_seq even */
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subscriptions->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(interval_sub, next,
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&subscriptions->deferred_list,
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deferred_item) {
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if (RB_EMPTY_NODE(&interval_sub->interval_tree.rb))
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interval_tree_insert(&interval_sub->interval_tree,
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&subscriptions->itree);
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else
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interval_tree_remove(&interval_sub->interval_tree,
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&subscriptions->itree);
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hlist_del(&interval_sub->deferred_item);
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}
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spin_unlock(&subscriptions->lock);
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wake_up_all(&subscriptions->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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* @interval_sub: The interval subscription
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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
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* subscription. If the mm invokes invalidation during the critical section
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* then 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
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mmu_interval_read_begin(struct mmu_interval_notifier *interval_sub)
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{
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struct mmu_notifier_subscriptions *subscriptions =
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interval_sub->mm->notifier_subscriptions;
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unsigned long seq;
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bool is_invalidating;
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/*
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* If the subscription has a different seq value under the user_lock
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* than we started with then it has collided.
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*
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* If the subscription currently has the same seq value as the
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* subscriptions seq, then it is currently between
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* 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_itree_inv_start(): mmu_interval_read_begin():
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* spin_lock
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* seq = READ_ONCE(interval_sub->invalidate_seq);
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* seq == subs->invalidate_seq
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* spin_unlock
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* spin_lock
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* seq = ++subscriptions->invalidate_seq
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* spin_unlock
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* op->invalidate():
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* user_lock
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* mmu_interval_set_seq()
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* interval_sub->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 = ++subscriptions->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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* interval_sub->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(&subscriptions->lock);
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/* Pairs with the WRITE_ONCE in mmu_interval_set_seq() */
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seq = READ_ONCE(interval_sub->invalidate_seq);
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is_invalidating = seq == subscriptions->invalidate_seq;
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spin_unlock(&subscriptions->lock);
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/*
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* interval_sub->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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* subscriptions->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(subscriptions->wq,
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READ_ONCE(subscriptions->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_subscriptions *subscriptions,
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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 *interval_sub;
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unsigned long cur_seq;
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bool ret;
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for (interval_sub =
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mn_itree_inv_start_range(subscriptions, &range, &cur_seq);
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interval_sub;
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interval_sub = mn_itree_inv_next(interval_sub, &range)) {
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ret = interval_sub->ops->invalidate(interval_sub, &range,
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cur_seq);
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WARN_ON(!ret);
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}
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mn_itree_inv_end(subscriptions);
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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 notifier_subscriptions->lock in addition to SRCU and it serializes
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* against the other mmu notifiers with SRCU. struct mmu_notifier_subscriptions
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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_subscriptions *subscriptions,
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struct mm_struct *mm)
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{
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struct mmu_notifier *subscription;
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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(subscription, &subscriptions->list, hlist,
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srcu_read_lock_held(&srcu))
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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 (subscription->ops->release)
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subscription->ops->release(subscription, mm);
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spin_lock(&subscriptions->lock);
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while (unlikely(!hlist_empty(&subscriptions->list))) {
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subscription = hlist_entry(subscriptions->list.first,
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struct mmu_notifier, 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(&subscription->hlist);
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}
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spin_unlock(&subscriptions->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 notifier_subscriptions can't go away from under us because
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* one mm_count 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_subscriptions *subscriptions =
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mm->notifier_subscriptions;
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if (subscriptions->has_itree)
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mn_itree_release(subscriptions, mm);
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if (!hlist_empty(&subscriptions->list))
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mn_hlist_release(subscriptions, 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 *subscription;
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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(subscription,
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&mm->notifier_subscriptions->list, hlist,
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srcu_read_lock_held(&srcu)) {
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if (subscription->ops->clear_flush_young)
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young |= subscription->ops->clear_flush_young(
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subscription, 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 *subscription;
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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(subscription,
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&mm->notifier_subscriptions->list, hlist,
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srcu_read_lock_held(&srcu)) {
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if (subscription->ops->clear_young)
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young |= subscription->ops->clear_young(subscription,
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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 *subscription;
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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(subscription,
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&mm->notifier_subscriptions->list, hlist,
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srcu_read_lock_held(&srcu)) {
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if (subscription->ops->test_young) {
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young = subscription->ops->test_young(subscription, mm,
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address);
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if (young)
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break;
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}
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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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void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
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pte_t pte)
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{
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struct mmu_notifier *subscription;
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int id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(subscription,
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&mm->notifier_subscriptions->list, hlist,
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srcu_read_lock_held(&srcu)) {
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if (subscription->ops->change_pte)
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subscription->ops->change_pte(subscription, mm, address,
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pte);
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}
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srcu_read_unlock(&srcu, id);
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}
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static int mn_itree_invalidate(struct mmu_notifier_subscriptions *subscriptions,
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const struct mmu_notifier_range *range)
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{
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struct mmu_interval_notifier *interval_sub;
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unsigned long cur_seq;
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for (interval_sub =
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mn_itree_inv_start_range(subscriptions, range, &cur_seq);
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interval_sub;
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interval_sub = mn_itree_inv_next(interval_sub, range)) {
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bool ret;
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ret = interval_sub->ops->invalidate(interval_sub, range,
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cur_seq);
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|
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(subscriptions);
|
|
return -EAGAIN;
|
|
}
|
|
|
|
static int mn_hlist_invalidate_range_start(
|
|
struct mmu_notifier_subscriptions *subscriptions,
|
|
struct mmu_notifier_range *range)
|
|
{
|
|
struct mmu_notifier *subscription;
|
|
int ret = 0;
|
|
int id;
|
|
|
|
id = srcu_read_lock(&srcu);
|
|
hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist,
|
|
srcu_read_lock_held(&srcu)) {
|
|
const struct mmu_notifier_ops *ops = subscription->ops;
|
|
|
|
if (ops->invalidate_range_start) {
|
|
int _ret;
|
|
|
|
if (!mmu_notifier_range_blockable(range))
|
|
non_block_start();
|
|
_ret = ops->invalidate_range_start(subscription, range);
|
|
if (!mmu_notifier_range_blockable(range))
|
|
non_block_end();
|
|
if (_ret) {
|
|
pr_info("%pS callback failed with %d in %sblockable context.\n",
|
|
ops->invalidate_range_start, _ret,
|
|
!mmu_notifier_range_blockable(range) ?
|
|
"non-" :
|
|
"");
|
|
WARN_ON(mmu_notifier_range_blockable(range) ||
|
|
_ret != -EAGAIN);
|
|
/*
|
|
* We call all the notifiers on any EAGAIN,
|
|
* there is no way for a notifier to know if
|
|
* its start method failed, thus a start that
|
|
* does EAGAIN can't also do end.
|
|
*/
|
|
WARN_ON(ops->invalidate_range_end);
|
|
ret = _ret;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (ret) {
|
|
/*
|
|
* Must be non-blocking to get here. If there are multiple
|
|
* notifiers and one or more failed start, any that succeeded
|
|
* start are expecting their end to be called. Do so now.
|
|
*/
|
|
hlist_for_each_entry_rcu(subscription, &subscriptions->list,
|
|
hlist, srcu_read_lock_held(&srcu)) {
|
|
if (!subscription->ops->invalidate_range_end)
|
|
continue;
|
|
|
|
subscription->ops->invalidate_range_end(subscription,
|
|
range);
|
|
}
|
|
}
|
|
srcu_read_unlock(&srcu, id);
|
|
|
|
return ret;
|
|
}
|
|
|
|
int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
|
|
{
|
|
struct mmu_notifier_subscriptions *subscriptions =
|
|
range->mm->notifier_subscriptions;
|
|
int ret;
|
|
|
|
if (subscriptions->has_itree) {
|
|
ret = mn_itree_invalidate(subscriptions, range);
|
|
if (ret)
|
|
return ret;
|
|
}
|
|
if (!hlist_empty(&subscriptions->list))
|
|
return mn_hlist_invalidate_range_start(subscriptions, range);
|
|
return 0;
|
|
}
|
|
|
|
static void
|
|
mn_hlist_invalidate_end(struct mmu_notifier_subscriptions *subscriptions,
|
|
struct mmu_notifier_range *range)
|
|
{
|
|
struct mmu_notifier *subscription;
|
|
int id;
|
|
|
|
id = srcu_read_lock(&srcu);
|
|
hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist,
|
|
srcu_read_lock_held(&srcu)) {
|
|
if (subscription->ops->invalidate_range_end) {
|
|
if (!mmu_notifier_range_blockable(range))
|
|
non_block_start();
|
|
subscription->ops->invalidate_range_end(subscription,
|
|
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)
|
|
{
|
|
struct mmu_notifier_subscriptions *subscriptions =
|
|
range->mm->notifier_subscriptions;
|
|
|
|
lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
|
|
if (subscriptions->has_itree)
|
|
mn_itree_inv_end(subscriptions);
|
|
|
|
if (!hlist_empty(&subscriptions->list))
|
|
mn_hlist_invalidate_end(subscriptions, range);
|
|
lock_map_release(&__mmu_notifier_invalidate_range_start_map);
|
|
}
|
|
|
|
void __mmu_notifier_arch_invalidate_secondary_tlbs(struct mm_struct *mm,
|
|
unsigned long start, unsigned long end)
|
|
{
|
|
struct mmu_notifier *subscription;
|
|
int id;
|
|
|
|
id = srcu_read_lock(&srcu);
|
|
hlist_for_each_entry_rcu(subscription,
|
|
&mm->notifier_subscriptions->list, hlist,
|
|
srcu_read_lock_held(&srcu)) {
|
|
if (subscription->ops->arch_invalidate_secondary_tlbs)
|
|
subscription->ops->arch_invalidate_secondary_tlbs(
|
|
subscription, mm,
|
|
start, end);
|
|
}
|
|
srcu_read_unlock(&srcu, id);
|
|
}
|
|
|
|
/*
|
|
* Same as mmu_notifier_register but here the caller must hold the mmap_lock in
|
|
* write mode. A NULL mn signals the notifier is being registered for itree
|
|
* mode.
|
|
*/
|
|
int __mmu_notifier_register(struct mmu_notifier *subscription,
|
|
struct mm_struct *mm)
|
|
{
|
|
struct mmu_notifier_subscriptions *subscriptions = NULL;
|
|
int ret;
|
|
|
|
mmap_assert_write_locked(mm);
|
|
BUG_ON(atomic_read(&mm->mm_users) <= 0);
|
|
|
|
/*
|
|
* Subsystems should only register for invalidate_secondary_tlbs() or
|
|
* invalidate_range_start()/end() callbacks, not both.
|
|
*/
|
|
if (WARN_ON_ONCE(subscription &&
|
|
(subscription->ops->arch_invalidate_secondary_tlbs &&
|
|
(subscription->ops->invalidate_range_start ||
|
|
subscription->ops->invalidate_range_end))))
|
|
return -EINVAL;
|
|
|
|
if (!mm->notifier_subscriptions) {
|
|
/*
|
|
* kmalloc cannot be called under mm_take_all_locks(), but we
|
|
* know that mm->notifier_subscriptions can't change while we
|
|
* hold the write side of the mmap_lock.
|
|
*/
|
|
subscriptions = kzalloc(
|
|
sizeof(struct mmu_notifier_subscriptions), GFP_KERNEL);
|
|
if (!subscriptions)
|
|
return -ENOMEM;
|
|
|
|
INIT_HLIST_HEAD(&subscriptions->list);
|
|
spin_lock_init(&subscriptions->lock);
|
|
subscriptions->invalidate_seq = 2;
|
|
subscriptions->itree = RB_ROOT_CACHED;
|
|
init_waitqueue_head(&subscriptions->wq);
|
|
INIT_HLIST_HEAD(&subscriptions->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_subscriptions'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_notifier_subscriptions is not freed until the mm is destroyed.
|
|
* As above, users holding the mmap_lock or one of the
|
|
* mm_take_all_locks() do not need to use acquire semantics.
|
|
*/
|
|
if (subscriptions)
|
|
smp_store_release(&mm->notifier_subscriptions, subscriptions);
|
|
|
|
if (subscription) {
|
|
/* Pairs with the mmdrop in mmu_notifier_unregister_* */
|
|
mmgrab(mm);
|
|
subscription->mm = mm;
|
|
subscription->users = 1;
|
|
|
|
spin_lock(&mm->notifier_subscriptions->lock);
|
|
hlist_add_head_rcu(&subscription->hlist,
|
|
&mm->notifier_subscriptions->list);
|
|
spin_unlock(&mm->notifier_subscriptions->lock);
|
|
} else
|
|
mm->notifier_subscriptions->has_itree = true;
|
|
|
|
mm_drop_all_locks(mm);
|
|
BUG_ON(atomic_read(&mm->mm_users) <= 0);
|
|
return 0;
|
|
|
|
out_clean:
|
|
kfree(subscriptions);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__mmu_notifier_register);
|
|
|
|
/**
|
|
* mmu_notifier_register - Register a notifier on a mm
|
|
* @subscription: The notifier to attach
|
|
* @mm: The mm to attach the notifier to
|
|
*
|
|
* Must not hold mmap_lock 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 subscription->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 *subscription,
|
|
struct mm_struct *mm)
|
|
{
|
|
int ret;
|
|
|
|
mmap_write_lock(mm);
|
|
ret = __mmu_notifier_register(subscription, mm);
|
|
mmap_write_unlock(mm);
|
|
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 *subscription;
|
|
|
|
spin_lock(&mm->notifier_subscriptions->lock);
|
|
hlist_for_each_entry_rcu(subscription,
|
|
&mm->notifier_subscriptions->list, hlist,
|
|
lockdep_is_held(&mm->notifier_subscriptions->lock)) {
|
|
if (subscription->ops != ops)
|
|
continue;
|
|
|
|
if (likely(subscription->users != UINT_MAX))
|
|
subscription->users++;
|
|
else
|
|
subscription = ERR_PTR(-EOVERFLOW);
|
|
spin_unlock(&mm->notifier_subscriptions->lock);
|
|
return subscription;
|
|
}
|
|
spin_unlock(&mm->notifier_subscriptions->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_lock.
|
|
*
|
|
* 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 *subscription;
|
|
int ret;
|
|
|
|
mmap_assert_write_locked(mm);
|
|
|
|
if (mm->notifier_subscriptions) {
|
|
subscription = find_get_mmu_notifier(mm, ops);
|
|
if (subscription)
|
|
return subscription;
|
|
}
|
|
|
|
subscription = ops->alloc_notifier(mm);
|
|
if (IS_ERR(subscription))
|
|
return subscription;
|
|
subscription->ops = ops;
|
|
ret = __mmu_notifier_register(subscription, mm);
|
|
if (ret)
|
|
goto out_free;
|
|
return subscription;
|
|
out_free:
|
|
subscription->ops->free_notifier(subscription);
|
|
return ERR_PTR(ret);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_notifier_get_locked);
|
|
|
|
/* this is called after the last mmu_notifier_unregister() returned */
|
|
void __mmu_notifier_subscriptions_destroy(struct mm_struct *mm)
|
|
{
|
|
BUG_ON(!hlist_empty(&mm->notifier_subscriptions->list));
|
|
kfree(mm->notifier_subscriptions);
|
|
mm->notifier_subscriptions = 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 *subscription,
|
|
struct mm_struct *mm)
|
|
{
|
|
BUG_ON(atomic_read(&mm->mm_count) <= 0);
|
|
|
|
if (!hlist_unhashed(&subscription->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 (subscription->ops->release)
|
|
subscription->ops->release(subscription, mm);
|
|
srcu_read_unlock(&srcu, id);
|
|
|
|
spin_lock(&mm->notifier_subscriptions->lock);
|
|
/*
|
|
* Can not use list_del_rcu() since __mmu_notifier_release
|
|
* can delete it before we hold the lock.
|
|
*/
|
|
hlist_del_init_rcu(&subscription->hlist);
|
|
spin_unlock(&mm->notifier_subscriptions->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 *subscription =
|
|
container_of(rcu, struct mmu_notifier, rcu);
|
|
struct mm_struct *mm = subscription->mm;
|
|
|
|
subscription->ops->free_notifier(subscription);
|
|
/* Pairs with the get in __mmu_notifier_register() */
|
|
mmdrop(mm);
|
|
}
|
|
|
|
/**
|
|
* mmu_notifier_put - Release the reference on the notifier
|
|
* @subscription: 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 *subscription)
|
|
{
|
|
struct mm_struct *mm = subscription->mm;
|
|
|
|
spin_lock(&mm->notifier_subscriptions->lock);
|
|
if (WARN_ON(!subscription->users) || --subscription->users)
|
|
goto out_unlock;
|
|
hlist_del_init_rcu(&subscription->hlist);
|
|
spin_unlock(&mm->notifier_subscriptions->lock);
|
|
|
|
call_srcu(&srcu, &subscription->rcu, mmu_notifier_free_rcu);
|
|
return;
|
|
|
|
out_unlock:
|
|
spin_unlock(&mm->notifier_subscriptions->lock);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_notifier_put);
|
|
|
|
static int __mmu_interval_notifier_insert(
|
|
struct mmu_interval_notifier *interval_sub, struct mm_struct *mm,
|
|
struct mmu_notifier_subscriptions *subscriptions, unsigned long start,
|
|
unsigned long length, const struct mmu_interval_notifier_ops *ops)
|
|
{
|
|
interval_sub->mm = mm;
|
|
interval_sub->ops = ops;
|
|
RB_CLEAR_NODE(&interval_sub->interval_tree.rb);
|
|
interval_sub->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,
|
|
&interval_sub->interval_tree.last))
|
|
return -EOVERFLOW;
|
|
|
|
/* Must call with a mmget() held */
|
|
if (WARN_ON(atomic_read(&mm->mm_users) <= 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 interval_sub->invalidate_seq should be
|
|
* odd, see mmu_interval_read_begin()
|
|
*/
|
|
spin_lock(&subscriptions->lock);
|
|
if (subscriptions->active_invalidate_ranges) {
|
|
if (mn_itree_is_invalidating(subscriptions))
|
|
hlist_add_head(&interval_sub->deferred_item,
|
|
&subscriptions->deferred_list);
|
|
else {
|
|
subscriptions->invalidate_seq |= 1;
|
|
interval_tree_insert(&interval_sub->interval_tree,
|
|
&subscriptions->itree);
|
|
}
|
|
interval_sub->invalidate_seq = subscriptions->invalidate_seq;
|
|
} else {
|
|
WARN_ON(mn_itree_is_invalidating(subscriptions));
|
|
/*
|
|
* The starting seq for a subscription 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.
|
|
*/
|
|
interval_sub->invalidate_seq =
|
|
subscriptions->invalidate_seq - 1;
|
|
interval_tree_insert(&interval_sub->interval_tree,
|
|
&subscriptions->itree);
|
|
}
|
|
spin_unlock(&subscriptions->lock);
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* mmu_interval_notifier_insert - Insert an interval notifier
|
|
* @interval_sub: Interval subscription to register
|
|
* @start: Starting virtual address to monitor
|
|
* @length: Length of the range to monitor
|
|
* @mm: mm_struct to attach to
|
|
* @ops: Interval notifier operations to be called on matching events
|
|
*
|
|
* 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 *interval_sub,
|
|
struct mm_struct *mm, unsigned long start,
|
|
unsigned long length,
|
|
const struct mmu_interval_notifier_ops *ops)
|
|
{
|
|
struct mmu_notifier_subscriptions *subscriptions;
|
|
int ret;
|
|
|
|
might_lock(&mm->mmap_lock);
|
|
|
|
subscriptions = smp_load_acquire(&mm->notifier_subscriptions);
|
|
if (!subscriptions || !subscriptions->has_itree) {
|
|
ret = mmu_notifier_register(NULL, mm);
|
|
if (ret)
|
|
return ret;
|
|
subscriptions = mm->notifier_subscriptions;
|
|
}
|
|
return __mmu_interval_notifier_insert(interval_sub, mm, subscriptions,
|
|
start, length, ops);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert);
|
|
|
|
int mmu_interval_notifier_insert_locked(
|
|
struct mmu_interval_notifier *interval_sub, struct mm_struct *mm,
|
|
unsigned long start, unsigned long length,
|
|
const struct mmu_interval_notifier_ops *ops)
|
|
{
|
|
struct mmu_notifier_subscriptions *subscriptions =
|
|
mm->notifier_subscriptions;
|
|
int ret;
|
|
|
|
mmap_assert_write_locked(mm);
|
|
|
|
if (!subscriptions || !subscriptions->has_itree) {
|
|
ret = __mmu_notifier_register(NULL, mm);
|
|
if (ret)
|
|
return ret;
|
|
subscriptions = mm->notifier_subscriptions;
|
|
}
|
|
return __mmu_interval_notifier_insert(interval_sub, mm, subscriptions,
|
|
start, length, ops);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert_locked);
|
|
|
|
static bool
|
|
mmu_interval_seq_released(struct mmu_notifier_subscriptions *subscriptions,
|
|
unsigned long seq)
|
|
{
|
|
bool ret;
|
|
|
|
spin_lock(&subscriptions->lock);
|
|
ret = subscriptions->invalidate_seq != seq;
|
|
spin_unlock(&subscriptions->lock);
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* mmu_interval_notifier_remove - Remove a interval notifier
|
|
* @interval_sub: Interval subscription 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 *interval_sub)
|
|
{
|
|
struct mm_struct *mm = interval_sub->mm;
|
|
struct mmu_notifier_subscriptions *subscriptions =
|
|
mm->notifier_subscriptions;
|
|
unsigned long seq = 0;
|
|
|
|
might_sleep();
|
|
|
|
spin_lock(&subscriptions->lock);
|
|
if (mn_itree_is_invalidating(subscriptions)) {
|
|
/*
|
|
* remove is being called after insert put this on the
|
|
* deferred list, but before the deferred list was processed.
|
|
*/
|
|
if (RB_EMPTY_NODE(&interval_sub->interval_tree.rb)) {
|
|
hlist_del(&interval_sub->deferred_item);
|
|
} else {
|
|
hlist_add_head(&interval_sub->deferred_item,
|
|
&subscriptions->deferred_list);
|
|
seq = subscriptions->invalidate_seq;
|
|
}
|
|
} else {
|
|
WARN_ON(RB_EMPTY_NODE(&interval_sub->interval_tree.rb));
|
|
interval_tree_remove(&interval_sub->interval_tree,
|
|
&subscriptions->itree);
|
|
}
|
|
spin_unlock(&subscriptions->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(subscriptions->wq,
|
|
mmu_interval_seq_released(subscriptions, 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);
|