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c942fddf | 1 | /* SPDX-License-Identifier: GPL-2.0-or-later */ |
133ff0ea JG |
2 | /* |
3 | * Copyright 2013 Red Hat Inc. | |
4 | * | |
f813f219 | 5 | * Authors: Jérôme Glisse <jglisse@redhat.com> |
133ff0ea JG |
6 | */ |
7 | /* | |
8 | * Heterogeneous Memory Management (HMM) | |
9 | * | |
ad56b738 | 10 | * See Documentation/vm/hmm.rst for reasons and overview of what HMM is and it |
133ff0ea JG |
11 | * is for. Here we focus on the HMM API description, with some explanation of |
12 | * the underlying implementation. | |
13 | * | |
14 | * Short description: HMM provides a set of helpers to share a virtual address | |
15 | * space between CPU and a device, so that the device can access any valid | |
16 | * address of the process (while still obeying memory protection). HMM also | |
17 | * provides helpers to migrate process memory to device memory, and back. Each | |
18 | * set of functionality (address space mirroring, and migration to and from | |
19 | * device memory) can be used independently of the other. | |
20 | * | |
21 | * | |
22 | * HMM address space mirroring API: | |
23 | * | |
085ea250 RC |
24 | * Use HMM address space mirroring if you want to mirror a range of the CPU |
25 | * page tables of a process into a device page table. Here, "mirror" means "keep | |
133ff0ea JG |
26 | * synchronized". Prerequisites: the device must provide the ability to write- |
27 | * protect its page tables (at PAGE_SIZE granularity), and must be able to | |
28 | * recover from the resulting potential page faults. | |
29 | * | |
30 | * HMM guarantees that at any point in time, a given virtual address points to | |
31 | * either the same memory in both CPU and device page tables (that is: CPU and | |
32 | * device page tables each point to the same pages), or that one page table (CPU | |
33 | * or device) points to no entry, while the other still points to the old page | |
34 | * for the address. The latter case happens when the CPU page table update | |
35 | * happens first, and then the update is mirrored over to the device page table. | |
36 | * This does not cause any issue, because the CPU page table cannot start | |
37 | * pointing to a new page until the device page table is invalidated. | |
38 | * | |
39 | * HMM uses mmu_notifiers to monitor the CPU page tables, and forwards any | |
40 | * updates to each device driver that has registered a mirror. It also provides | |
41 | * some API calls to help with taking a snapshot of the CPU page table, and to | |
42 | * synchronize with any updates that might happen concurrently. | |
43 | * | |
44 | * | |
45 | * HMM migration to and from device memory: | |
46 | * | |
47 | * HMM provides a set of helpers to hotplug device memory as ZONE_DEVICE, with | |
48 | * a new MEMORY_DEVICE_PRIVATE type. This provides a struct page for each page | |
49 | * of the device memory, and allows the device driver to manage its memory | |
50 | * using those struct pages. Having struct pages for device memory makes | |
51 | * migration easier. Because that memory is not addressable by the CPU it must | |
52 | * never be pinned to the device; in other words, any CPU page fault can always | |
53 | * cause the device memory to be migrated (copied/moved) back to regular memory. | |
54 | * | |
55 | * A new migrate helper (migrate_vma()) has been added (see mm/migrate.c) that | |
56 | * allows use of a device DMA engine to perform the copy operation between | |
57 | * regular system memory and device memory. | |
58 | */ | |
59 | #ifndef LINUX_HMM_H | |
60 | #define LINUX_HMM_H | |
61 | ||
62 | #include <linux/kconfig.h> | |
063a7d1d | 63 | #include <asm/pgtable.h> |
133ff0ea | 64 | |
43535b0a | 65 | #ifdef CONFIG_HMM_MIRROR |
133ff0ea | 66 | |
858b54da | 67 | #include <linux/device.h> |
4ef589dc JG |
68 | #include <linux/migrate.h> |
69 | #include <linux/memremap.h> | |
70 | #include <linux/completion.h> | |
a3e0d41c | 71 | #include <linux/mmu_notifier.h> |
4ef589dc | 72 | |
a3e0d41c JG |
73 | |
74 | /* | |
75 | * struct hmm - HMM per mm struct | |
76 | * | |
77 | * @mm: mm struct this HMM struct is bound to | |
78 | * @lock: lock protecting ranges list | |
79 | * @ranges: list of range being snapshotted | |
80 | * @mirrors: list of mirrors for this mm | |
81 | * @mmu_notifier: mmu notifier to track updates to CPU page table | |
82 | * @mirrors_sem: read/write semaphore protecting the mirrors list | |
83 | * @wq: wait queue for user waiting on a range invalidation | |
84 | * @notifiers: count of active mmu notifiers | |
a3e0d41c JG |
85 | */ |
86 | struct hmm { | |
87 | struct mm_struct *mm; | |
88 | struct kref kref; | |
5a136b4a | 89 | spinlock_t ranges_lock; |
a3e0d41c JG |
90 | struct list_head ranges; |
91 | struct list_head mirrors; | |
92 | struct mmu_notifier mmu_notifier; | |
93 | struct rw_semaphore mirrors_sem; | |
94 | wait_queue_head_t wq; | |
6d7c3cde | 95 | struct rcu_head rcu; |
a3e0d41c | 96 | long notifiers; |
a3e0d41c | 97 | }; |
133ff0ea JG |
98 | |
99 | /* | |
f88a1e90 JG |
100 | * hmm_pfn_flag_e - HMM flag enums |
101 | * | |
133ff0ea | 102 | * Flags: |
86586a41 | 103 | * HMM_PFN_VALID: pfn is valid. It has, at least, read permission. |
133ff0ea | 104 | * HMM_PFN_WRITE: CPU page table has write permission set |
f88a1e90 JG |
105 | * HMM_PFN_DEVICE_PRIVATE: private device memory (ZONE_DEVICE) |
106 | * | |
085ea250 RC |
107 | * The driver provides a flags array for mapping page protections to device |
108 | * PTE bits. If the driver valid bit for an entry is bit 3, | |
109 | * i.e., (entry & (1 << 3)), then the driver must provide | |
f88a1e90 | 110 | * an array in hmm_range.flags with hmm_range.flags[HMM_PFN_VALID] == 1 << 3. |
085ea250 | 111 | * Same logic apply to all flags. This is the same idea as vm_page_prot in vma |
f88a1e90 JG |
112 | * except that this is per device driver rather than per architecture. |
113 | */ | |
114 | enum hmm_pfn_flag_e { | |
115 | HMM_PFN_VALID = 0, | |
116 | HMM_PFN_WRITE, | |
117 | HMM_PFN_DEVICE_PRIVATE, | |
118 | HMM_PFN_FLAG_MAX | |
119 | }; | |
120 | ||
121 | /* | |
122 | * hmm_pfn_value_e - HMM pfn special value | |
123 | * | |
124 | * Flags: | |
da4c3c73 | 125 | * HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned memory |
f88a1e90 | 126 | * HMM_PFN_NONE: corresponding CPU page table entry is pte_none() |
da4c3c73 | 127 | * HMM_PFN_SPECIAL: corresponding CPU page table entry is special; i.e., the |
67fa1666 | 128 | * result of vmf_insert_pfn() or vm_insert_page(). Therefore, it should not |
da4c3c73 JG |
129 | * be mirrored by a device, because the entry will never have HMM_PFN_VALID |
130 | * set and the pfn value is undefined. | |
f88a1e90 | 131 | * |
085ea250 RC |
132 | * Driver provides values for none entry, error entry, and special entry. |
133 | * Driver can alias (i.e., use same value) error and special, but | |
134 | * it should not alias none with error or special. | |
f88a1e90 JG |
135 | * |
136 | * HMM pfn value returned by hmm_vma_get_pfns() or hmm_vma_fault() will be: | |
137 | * hmm_range.values[HMM_PFN_ERROR] if CPU page table entry is poisonous, | |
085ea250 | 138 | * hmm_range.values[HMM_PFN_NONE] if there is no CPU page table entry, |
f88a1e90 | 139 | * hmm_range.values[HMM_PFN_SPECIAL] if CPU page table entry is a special one |
133ff0ea | 140 | */ |
f88a1e90 JG |
141 | enum hmm_pfn_value_e { |
142 | HMM_PFN_ERROR, | |
143 | HMM_PFN_NONE, | |
144 | HMM_PFN_SPECIAL, | |
145 | HMM_PFN_VALUE_MAX | |
146 | }; | |
147 | ||
148 | /* | |
149 | * struct hmm_range - track invalidation lock on virtual address range | |
150 | * | |
704f3f2c | 151 | * @hmm: the core HMM structure this range is active against |
f88a1e90 JG |
152 | * @vma: the vm area struct for the range |
153 | * @list: all range lock are on a list | |
154 | * @start: range virtual start address (inclusive) | |
155 | * @end: range virtual end address (exclusive) | |
156 | * @pfns: array of pfns (big enough for the range) | |
157 | * @flags: pfn flags to match device driver page table | |
158 | * @values: pfn value for some special case (none, special, error, ...) | |
023a019a JG |
159 | * @default_flags: default flags for the range (write, read, ... see hmm doc) |
160 | * @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter | |
085ea250 | 161 | * @page_shift: device virtual address shift value (should be >= PAGE_SHIFT) |
f88a1e90 JG |
162 | * @pfn_shifts: pfn shift value (should be <= PAGE_SHIFT) |
163 | * @valid: pfns array did not change since it has been fill by an HMM function | |
164 | */ | |
165 | struct hmm_range { | |
704f3f2c | 166 | struct hmm *hmm; |
f88a1e90 JG |
167 | struct vm_area_struct *vma; |
168 | struct list_head list; | |
169 | unsigned long start; | |
170 | unsigned long end; | |
171 | uint64_t *pfns; | |
172 | const uint64_t *flags; | |
173 | const uint64_t *values; | |
023a019a JG |
174 | uint64_t default_flags; |
175 | uint64_t pfn_flags_mask; | |
63d5066f | 176 | uint8_t page_shift; |
f88a1e90 JG |
177 | uint8_t pfn_shift; |
178 | bool valid; | |
179 | }; | |
133ff0ea | 180 | |
63d5066f JG |
181 | /* |
182 | * hmm_range_page_shift() - return the page shift for the range | |
183 | * @range: range being queried | |
085ea250 | 184 | * Return: page shift (page size = 1 << page shift) for the range |
63d5066f JG |
185 | */ |
186 | static inline unsigned hmm_range_page_shift(const struct hmm_range *range) | |
187 | { | |
188 | return range->page_shift; | |
189 | } | |
190 | ||
191 | /* | |
192 | * hmm_range_page_size() - return the page size for the range | |
193 | * @range: range being queried | |
085ea250 | 194 | * Return: page size for the range in bytes |
63d5066f JG |
195 | */ |
196 | static inline unsigned long hmm_range_page_size(const struct hmm_range *range) | |
197 | { | |
198 | return 1UL << hmm_range_page_shift(range); | |
199 | } | |
200 | ||
a3e0d41c JG |
201 | /* |
202 | * hmm_range_wait_until_valid() - wait for range to be valid | |
203 | * @range: range affected by invalidation to wait on | |
204 | * @timeout: time out for wait in ms (ie abort wait after that period of time) | |
085ea250 | 205 | * Return: true if the range is valid, false otherwise. |
a3e0d41c JG |
206 | */ |
207 | static inline bool hmm_range_wait_until_valid(struct hmm_range *range, | |
208 | unsigned long timeout) | |
209 | { | |
378a6040 JG |
210 | return wait_event_timeout(range->hmm->wq, range->valid, |
211 | msecs_to_jiffies(timeout)) != 0; | |
a3e0d41c JG |
212 | } |
213 | ||
214 | /* | |
215 | * hmm_range_valid() - test if a range is valid or not | |
216 | * @range: range | |
085ea250 | 217 | * Return: true if the range is valid, false otherwise. |
a3e0d41c JG |
218 | */ |
219 | static inline bool hmm_range_valid(struct hmm_range *range) | |
220 | { | |
221 | return range->valid; | |
222 | } | |
223 | ||
133ff0ea | 224 | /* |
391aab11 JG |
225 | * hmm_device_entry_to_page() - return struct page pointed to by a device entry |
226 | * @range: range use to decode device entry value | |
227 | * @entry: device entry value to get corresponding struct page from | |
085ea250 | 228 | * Return: struct page pointer if entry is a valid, NULL otherwise |
133ff0ea | 229 | * |
391aab11 JG |
230 | * If the device entry is valid (ie valid flag set) then return the struct page |
231 | * matching the entry value. Otherwise return NULL. | |
133ff0ea | 232 | */ |
391aab11 JG |
233 | static inline struct page *hmm_device_entry_to_page(const struct hmm_range *range, |
234 | uint64_t entry) | |
133ff0ea | 235 | { |
391aab11 | 236 | if (entry == range->values[HMM_PFN_NONE]) |
f88a1e90 | 237 | return NULL; |
391aab11 | 238 | if (entry == range->values[HMM_PFN_ERROR]) |
f88a1e90 | 239 | return NULL; |
391aab11 | 240 | if (entry == range->values[HMM_PFN_SPECIAL]) |
133ff0ea | 241 | return NULL; |
391aab11 | 242 | if (!(entry & range->flags[HMM_PFN_VALID])) |
f88a1e90 | 243 | return NULL; |
391aab11 | 244 | return pfn_to_page(entry >> range->pfn_shift); |
133ff0ea JG |
245 | } |
246 | ||
247 | /* | |
391aab11 JG |
248 | * hmm_device_entry_to_pfn() - return pfn value store in a device entry |
249 | * @range: range use to decode device entry value | |
250 | * @entry: device entry to extract pfn from | |
085ea250 | 251 | * Return: pfn value if device entry is valid, -1UL otherwise |
133ff0ea | 252 | */ |
391aab11 JG |
253 | static inline unsigned long |
254 | hmm_device_entry_to_pfn(const struct hmm_range *range, uint64_t pfn) | |
133ff0ea | 255 | { |
f88a1e90 JG |
256 | if (pfn == range->values[HMM_PFN_NONE]) |
257 | return -1UL; | |
258 | if (pfn == range->values[HMM_PFN_ERROR]) | |
259 | return -1UL; | |
260 | if (pfn == range->values[HMM_PFN_SPECIAL]) | |
133ff0ea | 261 | return -1UL; |
f88a1e90 JG |
262 | if (!(pfn & range->flags[HMM_PFN_VALID])) |
263 | return -1UL; | |
264 | return (pfn >> range->pfn_shift); | |
133ff0ea JG |
265 | } |
266 | ||
267 | /* | |
391aab11 | 268 | * hmm_device_entry_from_page() - create a valid device entry for a page |
f88a1e90 | 269 | * @range: range use to encode HMM pfn value |
391aab11 | 270 | * @page: page for which to create the device entry |
085ea250 | 271 | * Return: valid device entry for the page |
133ff0ea | 272 | */ |
391aab11 JG |
273 | static inline uint64_t hmm_device_entry_from_page(const struct hmm_range *range, |
274 | struct page *page) | |
133ff0ea | 275 | { |
f88a1e90 JG |
276 | return (page_to_pfn(page) << range->pfn_shift) | |
277 | range->flags[HMM_PFN_VALID]; | |
133ff0ea JG |
278 | } |
279 | ||
280 | /* | |
391aab11 | 281 | * hmm_device_entry_from_pfn() - create a valid device entry value from pfn |
f88a1e90 | 282 | * @range: range use to encode HMM pfn value |
391aab11 | 283 | * @pfn: pfn value for which to create the device entry |
085ea250 | 284 | * Return: valid device entry for the pfn |
133ff0ea | 285 | */ |
391aab11 JG |
286 | static inline uint64_t hmm_device_entry_from_pfn(const struct hmm_range *range, |
287 | unsigned long pfn) | |
133ff0ea | 288 | { |
f88a1e90 JG |
289 | return (pfn << range->pfn_shift) | |
290 | range->flags[HMM_PFN_VALID]; | |
133ff0ea JG |
291 | } |
292 | ||
391aab11 JG |
293 | /* |
294 | * Old API: | |
295 | * hmm_pfn_to_page() | |
296 | * hmm_pfn_to_pfn() | |
297 | * hmm_pfn_from_page() | |
298 | * hmm_pfn_from_pfn() | |
299 | * | |
300 | * This are the OLD API please use new API, it is here to avoid cross-tree | |
301 | * merge painfullness ie we convert things to new API in stages. | |
302 | */ | |
303 | static inline struct page *hmm_pfn_to_page(const struct hmm_range *range, | |
304 | uint64_t pfn) | |
305 | { | |
306 | return hmm_device_entry_to_page(range, pfn); | |
307 | } | |
308 | ||
309 | static inline unsigned long hmm_pfn_to_pfn(const struct hmm_range *range, | |
310 | uint64_t pfn) | |
311 | { | |
312 | return hmm_device_entry_to_pfn(range, pfn); | |
313 | } | |
314 | ||
315 | static inline uint64_t hmm_pfn_from_page(const struct hmm_range *range, | |
316 | struct page *page) | |
317 | { | |
318 | return hmm_device_entry_from_page(range, page); | |
319 | } | |
320 | ||
321 | static inline uint64_t hmm_pfn_from_pfn(const struct hmm_range *range, | |
322 | unsigned long pfn) | |
323 | { | |
324 | return hmm_device_entry_from_pfn(range, pfn); | |
325 | } | |
326 | ||
c0b12405 JG |
327 | /* |
328 | * Mirroring: how to synchronize device page table with CPU page table. | |
329 | * | |
330 | * A device driver that is participating in HMM mirroring must always | |
331 | * synchronize with CPU page table updates. For this, device drivers can either | |
332 | * directly use mmu_notifier APIs or they can use the hmm_mirror API. Device | |
333 | * drivers can decide to register one mirror per device per process, or just | |
334 | * one mirror per process for a group of devices. The pattern is: | |
335 | * | |
336 | * int device_bind_address_space(..., struct mm_struct *mm, ...) | |
337 | * { | |
338 | * struct device_address_space *das; | |
339 | * | |
340 | * // Device driver specific initialization, and allocation of das | |
341 | * // which contains an hmm_mirror struct as one of its fields. | |
342 | * ... | |
343 | * | |
344 | * ret = hmm_mirror_register(&das->mirror, mm, &device_mirror_ops); | |
345 | * if (ret) { | |
346 | * // Cleanup on error | |
347 | * return ret; | |
348 | * } | |
349 | * | |
350 | * // Other device driver specific initialization | |
351 | * ... | |
352 | * } | |
353 | * | |
354 | * Once an hmm_mirror is registered for an address space, the device driver | |
355 | * will get callbacks through sync_cpu_device_pagetables() operation (see | |
356 | * hmm_mirror_ops struct). | |
357 | * | |
358 | * Device driver must not free the struct containing the hmm_mirror struct | |
359 | * before calling hmm_mirror_unregister(). The expected usage is to do that when | |
360 | * the device driver is unbinding from an address space. | |
361 | * | |
362 | * | |
363 | * void device_unbind_address_space(struct device_address_space *das) | |
364 | * { | |
365 | * // Device driver specific cleanup | |
366 | * ... | |
367 | * | |
368 | * hmm_mirror_unregister(&das->mirror); | |
369 | * | |
370 | * // Other device driver specific cleanup, and now das can be freed | |
371 | * ... | |
372 | * } | |
373 | */ | |
374 | ||
375 | struct hmm_mirror; | |
376 | ||
377 | /* | |
44532d4c | 378 | * enum hmm_update_event - type of update |
c0b12405 JG |
379 | * @HMM_UPDATE_INVALIDATE: invalidate range (no indication as to why) |
380 | */ | |
44532d4c | 381 | enum hmm_update_event { |
c0b12405 JG |
382 | HMM_UPDATE_INVALIDATE, |
383 | }; | |
384 | ||
44532d4c | 385 | /* |
085ea250 | 386 | * struct hmm_update - HMM update information for callback |
44532d4c JG |
387 | * |
388 | * @start: virtual start address of the range to update | |
389 | * @end: virtual end address of the range to update | |
390 | * @event: event triggering the update (what is happening) | |
391 | * @blockable: can the callback block/sleep ? | |
392 | */ | |
393 | struct hmm_update { | |
394 | unsigned long start; | |
395 | unsigned long end; | |
396 | enum hmm_update_event event; | |
397 | bool blockable; | |
398 | }; | |
399 | ||
c0b12405 JG |
400 | /* |
401 | * struct hmm_mirror_ops - HMM mirror device operations callback | |
402 | * | |
403 | * @update: callback to update range on a device | |
404 | */ | |
405 | struct hmm_mirror_ops { | |
e1401513 RC |
406 | /* release() - release hmm_mirror |
407 | * | |
408 | * @mirror: pointer to struct hmm_mirror | |
409 | * | |
2076e5c0 RC |
410 | * This is called when the mm_struct is being released. The callback |
411 | * must ensure that all access to any pages obtained from this mirror | |
412 | * is halted before the callback returns. All future access should | |
413 | * fault. | |
e1401513 RC |
414 | */ |
415 | void (*release)(struct hmm_mirror *mirror); | |
416 | ||
c0b12405 JG |
417 | /* sync_cpu_device_pagetables() - synchronize page tables |
418 | * | |
419 | * @mirror: pointer to struct hmm_mirror | |
085ea250 RC |
420 | * @update: update information (see struct hmm_update) |
421 | * Return: -EAGAIN if update.blockable false and callback need to | |
44532d4c | 422 | * block, 0 otherwise. |
c0b12405 JG |
423 | * |
424 | * This callback ultimately originates from mmu_notifiers when the CPU | |
425 | * page table is updated. The device driver must update its page table | |
426 | * in response to this callback. The update argument tells what action | |
427 | * to perform. | |
428 | * | |
429 | * The device driver must not return from this callback until the device | |
430 | * page tables are completely updated (TLBs flushed, etc); this is a | |
431 | * synchronous call. | |
432 | */ | |
44532d4c JG |
433 | int (*sync_cpu_device_pagetables)(struct hmm_mirror *mirror, |
434 | const struct hmm_update *update); | |
c0b12405 JG |
435 | }; |
436 | ||
437 | /* | |
438 | * struct hmm_mirror - mirror struct for a device driver | |
439 | * | |
440 | * @hmm: pointer to struct hmm (which is unique per mm_struct) | |
441 | * @ops: device driver callback for HMM mirror operations | |
442 | * @list: for list of mirrors of a given mm | |
443 | * | |
444 | * Each address space (mm_struct) being mirrored by a device must register one | |
445 | * instance of an hmm_mirror struct with HMM. HMM will track the list of all | |
446 | * mirrors for each mm_struct. | |
447 | */ | |
448 | struct hmm_mirror { | |
449 | struct hmm *hmm; | |
450 | const struct hmm_mirror_ops *ops; | |
451 | struct list_head list; | |
452 | }; | |
453 | ||
454 | int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm); | |
455 | void hmm_mirror_unregister(struct hmm_mirror *mirror); | |
da4c3c73 | 456 | |
da4c3c73 | 457 | /* |
a3e0d41c | 458 | * Please see Documentation/vm/hmm.rst for how to use the range API. |
da4c3c73 | 459 | */ |
a3e0d41c | 460 | int hmm_range_register(struct hmm_range *range, |
e36acfe6 | 461 | struct hmm_mirror *mirror, |
a3e0d41c | 462 | unsigned long start, |
63d5066f JG |
463 | unsigned long end, |
464 | unsigned page_shift); | |
a3e0d41c | 465 | void hmm_range_unregister(struct hmm_range *range); |
25f23a0c | 466 | long hmm_range_snapshot(struct hmm_range *range); |
a3e0d41c | 467 | long hmm_range_fault(struct hmm_range *range, bool block); |
55c0ece8 JG |
468 | long hmm_range_dma_map(struct hmm_range *range, |
469 | struct device *device, | |
470 | dma_addr_t *daddrs, | |
471 | bool block); | |
472 | long hmm_range_dma_unmap(struct hmm_range *range, | |
473 | struct vm_area_struct *vma, | |
474 | struct device *device, | |
475 | dma_addr_t *daddrs, | |
476 | bool dirty); | |
74eee180 JG |
477 | |
478 | /* | |
a3e0d41c | 479 | * HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range |
74eee180 | 480 | * |
a3e0d41c JG |
481 | * When waiting for mmu notifiers we need some kind of time out otherwise we |
482 | * could potentialy wait for ever, 1000ms ie 1s sounds like a long time to | |
483 | * wait already. | |
74eee180 | 484 | */ |
a3e0d41c JG |
485 | #define HMM_RANGE_DEFAULT_TIMEOUT 1000 |
486 | ||
9d8a463a | 487 | /* Below are for HMM internal use only! Not to be used by device driver! */ |
9d8a463a AB |
488 | static inline void hmm_mm_init(struct mm_struct *mm) |
489 | { | |
490 | mm->hmm = NULL; | |
491 | } | |
492 | #else /* IS_ENABLED(CONFIG_HMM_MIRROR) */ | |
9d8a463a AB |
493 | static inline void hmm_mm_init(struct mm_struct *mm) {} |
494 | #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */ | |
c0b12405 | 495 | |
133ff0ea | 496 | #endif /* LINUX_HMM_H */ |