summaryrefslogtreecommitdiff
path: root/include/linux/mmu_notifier.h
blob: c8672c366f675094f4083d9f99c6f8d32f935cad (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_MMU_NOTIFIER_H
#define _LINUX_MMU_NOTIFIER_H

#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/mm_types.h>
#include <linux/srcu.h>

struct mmu_notifier;
struct mmu_notifier_ops;

#ifdef CONFIG_MMU_NOTIFIER

/*
 * 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 registerd in this mm are queued in this list */
	struct hlist_head list;
	/* to serialize the list modifications and hlist_unhashed */
	spinlock_t lock;
};

#define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)

struct mmu_notifier_range {
	struct mm_struct *mm;
	unsigned long start;
	unsigned long end;
	unsigned flags;
};

struct mmu_notifier_ops {
	/*
	 * Called either by mmu_notifier_unregister or when the mm is
	 * being destroyed by exit_mmap, always before all pages are
	 * freed. This can run concurrently with other mmu notifier
	 * methods (the ones invoked outside the mm context) and it
	 * should tear down all secondary mmu mappings and freeze the
	 * secondary mmu. If this method isn't implemented you've to
	 * be sure that nothing could possibly write to the pages
	 * through the secondary mmu by the time the last thread with
	 * tsk->mm == mm exits.
	 *
	 * As side note: the pages freed after ->release returns could
	 * be immediately reallocated by the gart at an alias physical
	 * address with a different cache model, so if ->release isn't
	 * implemented because all _software_ driven memory accesses
	 * through the secondary mmu are terminated by the time the
	 * last thread of this mm quits, you've also to be sure that
	 * speculative _hardware_ operations can't allocate dirty
	 * cachelines in the cpu that could not be snooped and made
	 * coherent with the other read and write operations happening
	 * through the gart alias address, so leading to memory
	 * corruption.
	 */
	void (*release)(struct mmu_notifier *mn,
			struct mm_struct *mm);

	/*
	 * clear_flush_young is called after the VM is
	 * test-and-clearing the young/accessed bitflag in the
	 * pte. This way the VM will provide proper aging to the
	 * accesses to the page through the secondary MMUs and not
	 * only to the ones through the Linux pte.
	 * Start-end is necessary in case the secondary MMU is mapping the page
	 * at a smaller granularity than the primary MMU.
	 */
	int (*clear_flush_young)(struct mmu_notifier *mn,
				 struct mm_struct *mm,
				 unsigned long start,
				 unsigned long end);

	/*
	 * clear_young is a lightweight version of clear_flush_young. Like the
	 * latter, it is supposed to test-and-clear the young/accessed bitflag
	 * in the secondary pte, but it may omit flushing the secondary tlb.
	 */
	int (*clear_young)(struct mmu_notifier *mn,
			   struct mm_struct *mm,
			   unsigned long start,
			   unsigned long end);

	/*
	 * test_young is called to check the young/accessed bitflag in
	 * the secondary pte. This is used to know if the page is
	 * frequently used without actually clearing the flag or tearing
	 * down the secondary mapping on the page.
	 */
	int (*test_young)(struct mmu_notifier *mn,
			  struct mm_struct *mm,
			  unsigned long address);

	/*
	 * change_pte is called in cases that pte mapping to page is changed:
	 * for example, when ksm remaps pte to point to a new shared page.
	 */
	void (*change_pte)(struct mmu_notifier *mn,
			   struct mm_struct *mm,
			   unsigned long address,
			   pte_t pte);

	/*
	 * invalidate_range_start() and invalidate_range_end() must be
	 * paired and are called only when the mmap_sem and/or the
	 * locks protecting the reverse maps are held. If the subsystem
	 * can't guarantee that no additional references are taken to
	 * the pages in the range, it has to implement the
	 * invalidate_range() notifier to remove any references taken
	 * after invalidate_range_start().
	 *
	 * Invalidation of multiple concurrent ranges may be
	 * optionally permitted by the driver. Either way the
	 * establishment of sptes is forbidden in the range passed to
	 * invalidate_range_begin/end for the whole duration of the
	 * invalidate_range_begin/end critical section.
	 *
	 * invalidate_range_start() is called when all pages in the
	 * range are still mapped and have at least a refcount of one.
	 *
	 * invalidate_range_end() is called when all pages in the
	 * range have been unmapped and the pages have been freed by
	 * the VM.
	 *
	 * The VM will remove the page table entries and potentially
	 * the page between invalidate_range_start() and
	 * invalidate_range_end(). If the page must not be freed
	 * because of pending I/O or other circumstances then the
	 * invalidate_range_start() callback (or the initial mapping
	 * by the driver) must make sure that the refcount is kept
	 * elevated.
	 *
	 * If the driver increases the refcount when the pages are
	 * initially mapped into an address space then either
	 * invalidate_range_start() or invalidate_range_end() may
	 * decrease the refcount. If the refcount is decreased on
	 * invalidate_range_start() then the VM can free pages as page
	 * table entries are removed.  If the refcount is only
	 * droppped on invalidate_range_end() then the driver itself
	 * will drop the last refcount but it must take care to flush
	 * any secondary tlb before doing the final free on the
	 * page. Pages will no longer be referenced by the linux
	 * address space but may still be referenced by sptes until
	 * the last refcount is dropped.
	 *
	 * If blockable argument is set to false then the callback cannot
	 * sleep and has to return with -EAGAIN. 0 should be returned
	 * otherwise. Please note that if invalidate_range_start approves
	 * a non-blocking behavior then the same applies to
	 * invalidate_range_end.
	 *
	 */
	int (*invalidate_range_start)(struct mmu_notifier *mn,
				      const struct mmu_notifier_range *range);
	void (*invalidate_range_end)(struct mmu_notifier *mn,
				     const struct mmu_notifier_range *range);

	/*
	 * invalidate_range() is either called between
	 * invalidate_range_start() and invalidate_range_end() when the
	 * VM has to free pages that where unmapped, but before the
	 * pages are actually freed, or outside of _start()/_end() when
	 * a (remote) TLB is necessary.
	 *
	 * If invalidate_range() is used to manage a non-CPU TLB with
	 * shared page-tables, it not necessary to implement the
	 * invalidate_range_start()/end() notifiers, as
	 * invalidate_range() alread catches the points in time when an
	 * external TLB range needs to be flushed. For more in depth
	 * discussion on this see Documentation/vm/mmu_notifier.rst
	 *
	 * Note that this function might be called with just a sub-range
	 * of what was passed to invalidate_range_start()/end(), if
	 * called between those functions.
	 */
	void (*invalidate_range)(struct mmu_notifier *mn, struct mm_struct *mm,
				 unsigned long start, unsigned long end);
};

/*
 * The notifier chains are protected by mmap_sem and/or the reverse map
 * semaphores. Notifier chains are only changed when all reverse maps and
 * the mmap_sem locks are taken.
 *
 * Therefore notifier chains can only be traversed when either
 *
 * 1. mmap_sem is held.
 * 2. One of the reverse map locks is held (i_mmap_rwsem or anon_vma->rwsem).
 * 3. No other concurrent thread can access the list (release)
 */
struct mmu_notifier {
	struct hlist_node hlist;
	const struct mmu_notifier_ops *ops;
};

static inline int mm_has_notifiers(struct mm_struct *mm)
{
	return unlikely(mm->mmu_notifier_mm);
}

extern int mmu_notifier_register(struct mmu_notifier *mn,
				 struct mm_struct *mm);
extern int __mmu_notifier_register(struct mmu_notifier *mn,
				   struct mm_struct *mm);
extern void mmu_notifier_unregister(struct mmu_notifier *mn,
				    struct mm_struct *mm);
extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
					       struct mm_struct *mm);
extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
extern void __mmu_notifier_release(struct mm_struct *mm);
extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
					  unsigned long start,
					  unsigned long end);
extern int __mmu_notifier_clear_young(struct mm_struct *mm,
				      unsigned long start,
				      unsigned long end);
extern int __mmu_notifier_test_young(struct mm_struct *mm,
				     unsigned long address);
extern void __mmu_notifier_change_pte(struct mm_struct *mm,
				      unsigned long address, pte_t pte);
extern int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *r);
extern void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *r,
				  bool only_end);
extern void __mmu_notifier_invalidate_range(struct mm_struct *mm,
				  unsigned long start, unsigned long end);

static inline bool
mmu_notifier_range_blockable(const struct mmu_notifier_range *range)
{
	return (range->flags & MMU_NOTIFIER_RANGE_BLOCKABLE);
}

static inline void mmu_notifier_release(struct mm_struct *mm)
{
	if (mm_has_notifiers(mm))
		__mmu_notifier_release(mm);
}

static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
					  unsigned long start,
					  unsigned long end)
{
	if (mm_has_notifiers(mm))
		return __mmu_notifier_clear_flush_young(mm, start, end);
	return 0;
}

static inline int mmu_notifier_clear_young(struct mm_struct *mm,
					   unsigned long start,
					   unsigned long end)
{
	if (mm_has_notifiers(mm))
		return __mmu_notifier_clear_young(mm, start, end);
	return 0;
}

static inline int mmu_notifier_test_young(struct mm_struct *mm,
					  unsigned long address)
{
	if (mm_has_notifiers(mm))
		return __mmu_notifier_test_young(mm, address);
	return 0;
}

static inline void mmu_notifier_change_pte(struct mm_struct *mm,
					   unsigned long address, pte_t pte)
{
	if (mm_has_notifiers(mm))
		__mmu_notifier_change_pte(mm, address, pte);
}

static inline void
mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
{
	if (mm_has_notifiers(range->mm)) {
		range->flags |= MMU_NOTIFIER_RANGE_BLOCKABLE;
		__mmu_notifier_invalidate_range_start(range);
	}
}

static inline int
mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)
{
	if (mm_has_notifiers(range->mm)) {
		range->flags &= ~MMU_NOTIFIER_RANGE_BLOCKABLE;
		return __mmu_notifier_invalidate_range_start(range);
	}
	return 0;
}

static inline void
mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)
{
	if (mm_has_notifiers(range->mm))
		__mmu_notifier_invalidate_range_end(range, false);
}

static inline void
mmu_notifier_invalidate_range_only_end(struct mmu_notifier_range *range)
{
	if (mm_has_notifiers(range->mm))
		__mmu_notifier_invalidate_range_end(range, true);
}

static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
				  unsigned long start, unsigned long end)
{
	if (mm_has_notifiers(mm))
		__mmu_notifier_invalidate_range(mm, start, end);
}

static inline void mmu_notifier_mm_init(struct mm_struct *mm)
{
	mm->mmu_notifier_mm = NULL;
}

static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
{
	if (mm_has_notifiers(mm))
		__mmu_notifier_mm_destroy(mm);
}


static inline void mmu_notifier_range_init(struct mmu_notifier_range *range,
					   struct mm_struct *mm,
					   unsigned long start,
					   unsigned long end)
{
	range->mm = mm;
	range->start = start;
	range->end = end;
	range->flags = 0;
}

#define ptep_clear_flush_young_notify(__vma, __address, __ptep)		\
({									\
	int __young;							\
	struct vm_area_struct *___vma = __vma;				\
	unsigned long ___address = __address;				\
	__young = ptep_clear_flush_young(___vma, ___address, __ptep);	\
	__young |= mmu_notifier_clear_flush_young(___vma->vm_mm,	\
						  ___address,		\
						  ___address +		\
							PAGE_SIZE);	\
	__young;							\
})

#define pmdp_clear_flush_young_notify(__vma, __address, __pmdp)		\
({									\
	int __young;							\
	struct vm_area_struct *___vma = __vma;				\
	unsigned long ___address = __address;				\
	__young = pmdp_clear_flush_young(___vma, ___address, __pmdp);	\
	__young |= mmu_notifier_clear_flush_young(___vma->vm_mm,	\
						  ___address,		\
						  ___address +		\
							PMD_SIZE);	\
	__young;							\
})

#define ptep_clear_young_notify(__vma, __address, __ptep)		\
({									\
	int __young;							\
	struct vm_area_struct *___vma = __vma;				\
	unsigned long ___address = __address;				\
	__young = ptep_test_and_clear_young(___vma, ___address, __ptep);\
	__young |= mmu_notifier_clear_young(___vma->vm_mm, ___address,	\
					    ___address + PAGE_SIZE);	\
	__young;							\
})

#define pmdp_clear_young_notify(__vma, __address, __pmdp)		\
({									\
	int __young;							\
	struct vm_area_struct *___vma = __vma;				\
	unsigned long ___address = __address;				\
	__young = pmdp_test_and_clear_young(___vma, ___address, __pmdp);\
	__young |= mmu_notifier_clear_young(___vma->vm_mm, ___address,	\
					    ___address + PMD_SIZE);	\
	__young;							\
})

#define	ptep_clear_flush_notify(__vma, __address, __ptep)		\
({									\
	unsigned long ___addr = __address & PAGE_MASK;			\
	struct mm_struct *___mm = (__vma)->vm_mm;			\
	pte_t ___pte;							\
									\
	___pte = ptep_clear_flush(__vma, __address, __ptep);		\
	mmu_notifier_invalidate_range(___mm, ___addr,			\
					___addr + PAGE_SIZE);		\
									\
	___pte;								\
})

#define pmdp_huge_clear_flush_notify(__vma, __haddr, __pmd)		\
({									\
	unsigned long ___haddr = __haddr & HPAGE_PMD_MASK;		\
	struct mm_struct *___mm = (__vma)->vm_mm;			\
	pmd_t ___pmd;							\
									\
	___pmd = pmdp_huge_clear_flush(__vma, __haddr, __pmd);		\
	mmu_notifier_invalidate_range(___mm, ___haddr,			\
				      ___haddr + HPAGE_PMD_SIZE);	\
									\
	___pmd;								\
})

#define pudp_huge_clear_flush_notify(__vma, __haddr, __pud)		\
({									\
	unsigned long ___haddr = __haddr & HPAGE_PUD_MASK;		\
	struct mm_struct *___mm = (__vma)->vm_mm;			\
	pud_t ___pud;							\
									\
	___pud = pudp_huge_clear_flush(__vma, __haddr, __pud);		\
	mmu_notifier_invalidate_range(___mm, ___haddr,			\
				      ___haddr + HPAGE_PUD_SIZE);	\
									\
	___pud;								\
})

/*
 * set_pte_at_notify() sets the pte _after_ running the notifier.
 * This is safe to start by updating the secondary MMUs, because the primary MMU
 * pte invalidate must have already happened with a ptep_clear_flush() before
 * set_pte_at_notify() has been invoked.  Updating the secondary MMUs first is
 * required when we change both the protection of the mapping from read-only to
 * read-write and the pfn (like during copy on write page faults). Otherwise the
 * old page would remain mapped readonly in the secondary MMUs after the new
 * page is already writable by some CPU through the primary MMU.
 */
#define set_pte_at_notify(__mm, __address, __ptep, __pte)		\
({									\
	struct mm_struct *___mm = __mm;					\
	unsigned long ___address = __address;				\
	pte_t ___pte = __pte;						\
									\
	mmu_notifier_change_pte(___mm, ___address, ___pte);		\
	set_pte_at(___mm, ___address, __ptep, ___pte);			\
})

extern void mmu_notifier_call_srcu(struct rcu_head *rcu,
				   void (*func)(struct rcu_head *rcu));

#else /* CONFIG_MMU_NOTIFIER */

struct mmu_notifier_range {
	unsigned long start;
	unsigned long end;
};

static inline void _mmu_notifier_range_init(struct mmu_notifier_range *range,
					    unsigned long start,
					    unsigned long end)
{
	range->start = start;
	range->end = end;
}

#define mmu_notifier_range_init(range, mm, start, end) \
	_mmu_notifier_range_init(range, start, end)

static inline bool
mmu_notifier_range_blockable(const struct mmu_notifier_range *range)
{
	return true;
}

static inline int mm_has_notifiers(struct mm_struct *mm)
{
	return 0;
}

static inline void mmu_notifier_release(struct mm_struct *mm)
{
}

static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
					  unsigned long start,
					  unsigned long end)
{
	return 0;
}

static inline int mmu_notifier_test_young(struct mm_struct *mm,
					  unsigned long address)
{
	return 0;
}

static inline void mmu_notifier_change_pte(struct mm_struct *mm,
					   unsigned long address, pte_t pte)
{
}

static inline void
mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
{
}

static inline int
mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)
{
	return 0;
}

static inline
void mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)
{
}

static inline void
mmu_notifier_invalidate_range_only_end(struct mmu_notifier_range *range)
{
}

static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
				  unsigned long start, unsigned long end)
{
}

static inline void mmu_notifier_mm_init(struct mm_struct *mm)
{
}

static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
{
}

#define ptep_clear_flush_young_notify ptep_clear_flush_young
#define pmdp_clear_flush_young_notify pmdp_clear_flush_young
#define ptep_clear_young_notify ptep_test_and_clear_young
#define pmdp_clear_young_notify pmdp_test_and_clear_young
#define	ptep_clear_flush_notify ptep_clear_flush
#define pmdp_huge_clear_flush_notify pmdp_huge_clear_flush
#define pudp_huge_clear_flush_notify pudp_huge_clear_flush
#define set_pte_at_notify set_pte_at

#endif /* CONFIG_MMU_NOTIFIER */

#endif /* _LINUX_MMU_NOTIFIER_H */