linux/mm/mmu_notifier.c
Linus Torvalds aa32f11691 hmm related patches for 5.5
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
2019-11-30 10:33:14 -08:00

1052 lines
31 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/mm/mmu_notifier.c
*
* Copyright (C) 2008 Qumranet, Inc.
* Copyright (C) 2008 SGI
* Christoph Lameter <cl@linux.com>
*/
#include <linux/rculist.h>
#include <linux/mmu_notifier.h>
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/interval_tree.h>
#include <linux/srcu.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/slab.h>
/* global SRCU for all MMs */
DEFINE_STATIC_SRCU(srcu);
#ifdef CONFIG_LOCKDEP
struct lockdep_map __mmu_notifier_invalidate_range_start_map = {
.name = "mmu_notifier_invalidate_range_start"
};
#endif
/*
* The mmu notifier_mm structure is allocated and installed in
* mm->mmu_notifier_mm inside the mm_take_all_locks() protected
* critical section and it's released only when mm_count reaches zero
* in mmdrop().
*/
struct mmu_notifier_mm {
/* all mmu notifiers registered in this mm are queued in this list */
struct hlist_head list;
bool has_itree;
/* to serialize the list modifications and hlist_unhashed */
spinlock_t lock;
unsigned long invalidate_seq;
unsigned long active_invalidate_ranges;
struct rb_root_cached itree;
wait_queue_head_t wq;
struct hlist_head deferred_list;
};
/*
* This is a collision-retry read-side/write-side 'lock', a lot like a
* seqcount, however this allows multiple write-sides to hold it at
* once. Conceptually the write side is protecting the values of the PTEs in
* this mm, such that PTES cannot be read into SPTEs (shadow PTEs) while any
* writer exists.
*
* Note that the core mm creates nested invalidate_range_start()/end() regions
* within the same thread, and runs invalidate_range_start()/end() in parallel
* on multiple CPUs. This is designed to not reduce concurrency or block
* progress on the mm side.
*
* As a secondary function, holding the full write side also serves to prevent
* writers for the itree, this is an optimization to avoid extra locking
* during invalidate_range_start/end notifiers.
*
* The write side has two states, fully excluded:
* - mm->active_invalidate_ranges != 0
* - mnn->invalidate_seq & 1 == True (odd)
* - some range on the mm_struct is being invalidated
* - the itree is not allowed to change
*
* And partially excluded:
* - mm->active_invalidate_ranges != 0
* - mnn->invalidate_seq & 1 == False (even)
* - some range on the mm_struct is being invalidated
* - the itree is allowed to change
*
* Operations on mmu_notifier_mm->invalidate_seq (under spinlock):
* seq |= 1 # Begin writing
* seq++ # Release the writing state
* seq & 1 # True if a writer exists
*
* The later state avoids some expensive work on inv_end in the common case of
* no mni monitoring the VA.
*/
static bool mn_itree_is_invalidating(struct mmu_notifier_mm *mmn_mm)
{
lockdep_assert_held(&mmn_mm->lock);
return mmn_mm->invalidate_seq & 1;
}
static struct mmu_interval_notifier *
mn_itree_inv_start_range(struct mmu_notifier_mm *mmn_mm,
const struct mmu_notifier_range *range,
unsigned long *seq)
{
struct interval_tree_node *node;
struct mmu_interval_notifier *res = NULL;
spin_lock(&mmn_mm->lock);
mmn_mm->active_invalidate_ranges++;
node = interval_tree_iter_first(&mmn_mm->itree, range->start,
range->end - 1);
if (node) {
mmn_mm->invalidate_seq |= 1;
res = container_of(node, struct mmu_interval_notifier,
interval_tree);
}
*seq = mmn_mm->invalidate_seq;
spin_unlock(&mmn_mm->lock);
return res;
}
static struct mmu_interval_notifier *
mn_itree_inv_next(struct mmu_interval_notifier *mni,
const struct mmu_notifier_range *range)
{
struct interval_tree_node *node;
node = interval_tree_iter_next(&mni->interval_tree, range->start,
range->end - 1);
if (!node)
return NULL;
return container_of(node, struct mmu_interval_notifier, interval_tree);
}
static void mn_itree_inv_end(struct mmu_notifier_mm *mmn_mm)
{
struct mmu_interval_notifier *mni;
struct hlist_node *next;
spin_lock(&mmn_mm->lock);
if (--mmn_mm->active_invalidate_ranges ||
!mn_itree_is_invalidating(mmn_mm)) {
spin_unlock(&mmn_mm->lock);
return;
}
/* Make invalidate_seq even */
mmn_mm->invalidate_seq++;
/*
* The inv_end incorporates a deferred mechanism like rtnl_unlock().
* Adds and removes are queued until the final inv_end happens then
* they are progressed. This arrangement for tree updates is used to
* avoid using a blocking lock during invalidate_range_start.
*/
hlist_for_each_entry_safe(mni, next, &mmn_mm->deferred_list,
deferred_item) {
if (RB_EMPTY_NODE(&mni->interval_tree.rb))
interval_tree_insert(&mni->interval_tree,
&mmn_mm->itree);
else
interval_tree_remove(&mni->interval_tree,
&mmn_mm->itree);
hlist_del(&mni->deferred_item);
}
spin_unlock(&mmn_mm->lock);
wake_up_all(&mmn_mm->wq);
}
/**
* mmu_interval_read_begin - Begin a read side critical section against a VA
* range
* mni: The range to use
*
* mmu_iterval_read_begin()/mmu_iterval_read_retry() implement a
* collision-retry scheme similar to seqcount for the VA range under mni. If
* the mm invokes invalidation during the critical section then
* mmu_interval_read_retry() will return true.
*
* This is useful to obtain shadow PTEs where teardown or setup of the SPTEs
* require a blocking context. The critical region formed by this can sleep,
* and the required 'user_lock' can also be a sleeping lock.
*
* The caller is required to provide a 'user_lock' to serialize both teardown
* and setup.
*
* The return value should be passed to mmu_interval_read_retry().
*/
unsigned long mmu_interval_read_begin(struct mmu_interval_notifier *mni)
{
struct mmu_notifier_mm *mmn_mm = mni->mm->mmu_notifier_mm;
unsigned long seq;
bool is_invalidating;
/*
* If the mni has a different seq value under the user_lock than we
* started with then it has collided.
*
* If the mni currently has the same seq value as the mmn_mm seq, then
* it is currently between invalidate_start/end and is colliding.
*
* The locking looks broadly like this:
* mn_tree_invalidate_start(): mmu_interval_read_begin():
* spin_lock
* seq = READ_ONCE(mni->invalidate_seq);
* seq == mmn_mm->invalidate_seq
* spin_unlock
* spin_lock
* seq = ++mmn_mm->invalidate_seq
* spin_unlock
* op->invalidate_range():
* user_lock
* mmu_interval_set_seq()
* mni->invalidate_seq = seq
* user_unlock
*
* [Required: mmu_interval_read_retry() == true]
*
* mn_itree_inv_end():
* spin_lock
* seq = ++mmn_mm->invalidate_seq
* spin_unlock
*
* user_lock
* mmu_interval_read_retry():
* mni->invalidate_seq != seq
* user_unlock
*
* Barriers are not needed here as any races here are closed by an
* eventual mmu_interval_read_retry(), which provides a barrier via the
* user_lock.
*/
spin_lock(&mmn_mm->lock);
/* Pairs with the WRITE_ONCE in mmu_interval_set_seq() */
seq = READ_ONCE(mni->invalidate_seq);
is_invalidating = seq == mmn_mm->invalidate_seq;
spin_unlock(&mmn_mm->lock);
/*
* mni->invalidate_seq must always be set to an odd value via
* mmu_interval_set_seq() using the provided cur_seq from
* mn_itree_inv_start_range(). This ensures that if seq does wrap we
* will always clear the below sleep in some reasonable time as
* mmn_mm->invalidate_seq is even in the idle state.
*/
lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
lock_map_release(&__mmu_notifier_invalidate_range_start_map);
if (is_invalidating)
wait_event(mmn_mm->wq,
READ_ONCE(mmn_mm->invalidate_seq) != seq);
/*
* Notice that mmu_interval_read_retry() can already be true at this
* point, avoiding loops here allows the caller to provide a global
* time bound.
*/
return seq;
}
EXPORT_SYMBOL_GPL(mmu_interval_read_begin);
static void mn_itree_release(struct mmu_notifier_mm *mmn_mm,
struct mm_struct *mm)
{
struct mmu_notifier_range range = {
.flags = MMU_NOTIFIER_RANGE_BLOCKABLE,
.event = MMU_NOTIFY_RELEASE,
.mm = mm,
.start = 0,
.end = ULONG_MAX,
};
struct mmu_interval_notifier *mni;
unsigned long cur_seq;
bool ret;
for (mni = mn_itree_inv_start_range(mmn_mm, &range, &cur_seq); mni;
mni = mn_itree_inv_next(mni, &range)) {
ret = mni->ops->invalidate(mni, &range, cur_seq);
WARN_ON(!ret);
}
mn_itree_inv_end(mmn_mm);
}
/*
* This function can't run concurrently against mmu_notifier_register
* because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
* runs with mm_users == 0. Other tasks may still invoke mmu notifiers
* in parallel despite there being no task using this mm any more,
* through the vmas outside of the exit_mmap context, such as with
* vmtruncate. This serializes against mmu_notifier_unregister with
* the mmu_notifier_mm->lock in addition to SRCU and it serializes
* against the other mmu notifiers with SRCU. struct mmu_notifier_mm
* can't go away from under us as exit_mmap holds an mm_count pin
* itself.
*/
static void mn_hlist_release(struct mmu_notifier_mm *mmn_mm,
struct mm_struct *mm)
{
struct mmu_notifier *mn;
int id;
/*
* SRCU here will block mmu_notifier_unregister until
* ->release returns.
*/
id = srcu_read_lock(&srcu);
hlist_for_each_entry_rcu(mn, &mmn_mm->list, hlist)
/*
* If ->release runs before mmu_notifier_unregister it must be
* handled, as it's the only way for the driver to flush all
* existing sptes and stop the driver from establishing any more
* sptes before all the pages in the mm are freed.
*/
if (mn->ops->release)
mn->ops->release(mn, mm);
spin_lock(&mmn_mm->lock);
while (unlikely(!hlist_empty(&mmn_mm->list))) {
mn = hlist_entry(mmn_mm->list.first, struct mmu_notifier,
hlist);
/*
* We arrived before mmu_notifier_unregister so
* mmu_notifier_unregister will do nothing other than to wait
* for ->release to finish and for mmu_notifier_unregister to
* return.
*/
hlist_del_init_rcu(&mn->hlist);
}
spin_unlock(&mmn_mm->lock);
srcu_read_unlock(&srcu, id);
/*
* synchronize_srcu here prevents mmu_notifier_release from returning to
* exit_mmap (which would proceed with freeing all pages in the mm)
* until the ->release method returns, if it was invoked by
* mmu_notifier_unregister.
*
* The mmu_notifier_mm can't go away from under us because one mm_count
* is held by exit_mmap.
*/
synchronize_srcu(&srcu);
}
void __mmu_notifier_release(struct mm_struct *mm)
{
struct mmu_notifier_mm *mmn_mm = mm->mmu_notifier_mm;
if (mmn_mm->has_itree)
mn_itree_release(mmn_mm, mm);
if (!hlist_empty(&mmn_mm->list))
mn_hlist_release(mmn_mm, mm);
}
/*
* If no young bitflag is supported by the hardware, ->clear_flush_young can
* unmap the address and return 1 or 0 depending if the mapping previously
* existed or not.
*/
int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
unsigned long start,
unsigned long end)
{
struct mmu_notifier *mn;
int young = 0, id;
id = srcu_read_lock(&srcu);
hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
if (mn->ops->clear_flush_young)
young |= mn->ops->clear_flush_young(mn, mm, start, end);
}
srcu_read_unlock(&srcu, id);
return young;
}
int __mmu_notifier_clear_young(struct mm_struct *mm,
unsigned long start,
unsigned long end)
{
struct mmu_notifier *mn;
int young = 0, id;
id = srcu_read_lock(&srcu);
hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
if (mn->ops->clear_young)
young |= mn->ops->clear_young(mn, mm, start, end);
}
srcu_read_unlock(&srcu, id);
return young;
}
int __mmu_notifier_test_young(struct mm_struct *mm,
unsigned long address)
{
struct mmu_notifier *mn;
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);