mm/hmm: convert to use vm_fault_t
[muen/linux.git] / mm / hmm.c
1 /*
2  * Copyright 2013 Red Hat Inc.
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License as published by
6  * the Free Software Foundation; either version 2 of the License, or
7  * (at your option) any later version.
8  *
9  * This program is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  * GNU General Public License for more details.
13  *
14  * Authors: Jérôme Glisse <jglisse@redhat.com>
15  */
16 /*
17  * Refer to include/linux/hmm.h for information about heterogeneous memory
18  * management or HMM for short.
19  */
20 #include <linux/mm.h>
21 #include <linux/hmm.h>
22 #include <linux/init.h>
23 #include <linux/rmap.h>
24 #include <linux/swap.h>
25 #include <linux/slab.h>
26 #include <linux/sched.h>
27 #include <linux/mmzone.h>
28 #include <linux/pagemap.h>
29 #include <linux/swapops.h>
30 #include <linux/hugetlb.h>
31 #include <linux/memremap.h>
32 #include <linux/jump_label.h>
33 #include <linux/mmu_notifier.h>
34 #include <linux/memory_hotplug.h>
35
36 #define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT)
37
38 #if IS_ENABLED(CONFIG_HMM_MIRROR)
39 static const struct mmu_notifier_ops hmm_mmu_notifier_ops;
40
41 /*
42  * struct hmm - HMM per mm struct
43  *
44  * @mm: mm struct this HMM struct is bound to
45  * @lock: lock protecting ranges list
46  * @ranges: list of range being snapshotted
47  * @mirrors: list of mirrors for this mm
48  * @mmu_notifier: mmu notifier to track updates to CPU page table
49  * @mirrors_sem: read/write semaphore protecting the mirrors list
50  */
51 struct hmm {
52         struct mm_struct        *mm;
53         spinlock_t              lock;
54         struct list_head        ranges;
55         struct list_head        mirrors;
56         struct mmu_notifier     mmu_notifier;
57         struct rw_semaphore     mirrors_sem;
58 };
59
60 /*
61  * hmm_register - register HMM against an mm (HMM internal)
62  *
63  * @mm: mm struct to attach to
64  *
65  * This is not intended to be used directly by device drivers. It allocates an
66  * HMM struct if mm does not have one, and initializes it.
67  */
68 static struct hmm *hmm_register(struct mm_struct *mm)
69 {
70         struct hmm *hmm = READ_ONCE(mm->hmm);
71         bool cleanup = false;
72
73         /*
74          * The hmm struct can only be freed once the mm_struct goes away,
75          * hence we should always have pre-allocated an new hmm struct
76          * above.
77          */
78         if (hmm)
79                 return hmm;
80
81         hmm = kmalloc(sizeof(*hmm), GFP_KERNEL);
82         if (!hmm)
83                 return NULL;
84         INIT_LIST_HEAD(&hmm->mirrors);
85         init_rwsem(&hmm->mirrors_sem);
86         hmm->mmu_notifier.ops = NULL;
87         INIT_LIST_HEAD(&hmm->ranges);
88         spin_lock_init(&hmm->lock);
89         hmm->mm = mm;
90
91         spin_lock(&mm->page_table_lock);
92         if (!mm->hmm)
93                 mm->hmm = hmm;
94         else
95                 cleanup = true;
96         spin_unlock(&mm->page_table_lock);
97
98         if (cleanup)
99                 goto error;
100
101         /*
102          * We should only get here if hold the mmap_sem in write mode ie on
103          * registration of first mirror through hmm_mirror_register()
104          */
105         hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops;
106         if (__mmu_notifier_register(&hmm->mmu_notifier, mm))
107                 goto error_mm;
108
109         return mm->hmm;
110
111 error_mm:
112         spin_lock(&mm->page_table_lock);
113         if (mm->hmm == hmm)
114                 mm->hmm = NULL;
115         spin_unlock(&mm->page_table_lock);
116 error:
117         kfree(hmm);
118         return NULL;
119 }
120
121 void hmm_mm_destroy(struct mm_struct *mm)
122 {
123         kfree(mm->hmm);
124 }
125
126 static int hmm_invalidate_range(struct hmm *hmm, bool device,
127                                 const struct hmm_update *update)
128 {
129         struct hmm_mirror *mirror;
130         struct hmm_range *range;
131
132         spin_lock(&hmm->lock);
133         list_for_each_entry(range, &hmm->ranges, list) {
134                 unsigned long addr, idx, npages;
135
136                 if (update->end < range->start || update->start >= range->end)
137                         continue;
138
139                 range->valid = false;
140                 addr = max(update->start, range->start);
141                 idx = (addr - range->start) >> PAGE_SHIFT;
142                 npages = (min(range->end, update->end) - addr) >> PAGE_SHIFT;
143                 memset(&range->pfns[idx], 0, sizeof(*range->pfns) * npages);
144         }
145         spin_unlock(&hmm->lock);
146
147         if (!device)
148                 return 0;
149
150         down_read(&hmm->mirrors_sem);
151         list_for_each_entry(mirror, &hmm->mirrors, list) {
152                 int ret;
153
154                 ret = mirror->ops->sync_cpu_device_pagetables(mirror, update);
155                 if (!update->blockable && ret == -EAGAIN) {
156                         up_read(&hmm->mirrors_sem);
157                         return -EAGAIN;
158                 }
159         }
160         up_read(&hmm->mirrors_sem);
161
162         return 0;
163 }
164
165 static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
166 {
167         struct hmm_mirror *mirror;
168         struct hmm *hmm = mm->hmm;
169
170         down_write(&hmm->mirrors_sem);
171         mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror,
172                                           list);
173         while (mirror) {
174                 list_del_init(&mirror->list);
175                 if (mirror->ops->release) {
176                         /*
177                          * Drop mirrors_sem so callback can wait on any pending
178                          * work that might itself trigger mmu_notifier callback
179                          * and thus would deadlock with us.
180                          */
181                         up_write(&hmm->mirrors_sem);
182                         mirror->ops->release(mirror);
183                         down_write(&hmm->mirrors_sem);
184                 }
185                 mirror = list_first_entry_or_null(&hmm->mirrors,
186                                                   struct hmm_mirror, list);
187         }
188         up_write(&hmm->mirrors_sem);
189 }
190
191 static int hmm_invalidate_range_start(struct mmu_notifier *mn,
192                         const struct mmu_notifier_range *range)
193 {
194         struct hmm_update update;
195         struct hmm *hmm = range->mm->hmm;
196
197         VM_BUG_ON(!hmm);
198
199         update.start = range->start;
200         update.end = range->end;
201         update.event = HMM_UPDATE_INVALIDATE;
202         update.blockable = range->blockable;
203         return hmm_invalidate_range(hmm, true, &update);
204 }
205
206 static void hmm_invalidate_range_end(struct mmu_notifier *mn,
207                         const struct mmu_notifier_range *range)
208 {
209         struct hmm_update update;
210         struct hmm *hmm = range->mm->hmm;
211
212         VM_BUG_ON(!hmm);
213
214         update.start = range->start;
215         update.end = range->end;
216         update.event = HMM_UPDATE_INVALIDATE;
217         update.blockable = true;
218         hmm_invalidate_range(hmm, false, &update);
219 }
220
221 static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
222         .release                = hmm_release,
223         .invalidate_range_start = hmm_invalidate_range_start,
224         .invalidate_range_end   = hmm_invalidate_range_end,
225 };
226
227 /*
228  * hmm_mirror_register() - register a mirror against an mm
229  *
230  * @mirror: new mirror struct to register
231  * @mm: mm to register against
232  *
233  * To start mirroring a process address space, the device driver must register
234  * an HMM mirror struct.
235  *
236  * THE mm->mmap_sem MUST BE HELD IN WRITE MODE !
237  */
238 int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
239 {
240         /* Sanity check */
241         if (!mm || !mirror || !mirror->ops)
242                 return -EINVAL;
243
244 again:
245         mirror->hmm = hmm_register(mm);
246         if (!mirror->hmm)
247                 return -ENOMEM;
248
249         down_write(&mirror->hmm->mirrors_sem);
250         if (mirror->hmm->mm == NULL) {
251                 /*
252                  * A racing hmm_mirror_unregister() is about to destroy the hmm
253                  * struct. Try again to allocate a new one.
254                  */
255                 up_write(&mirror->hmm->mirrors_sem);
256                 mirror->hmm = NULL;
257                 goto again;
258         } else {
259                 list_add(&mirror->list, &mirror->hmm->mirrors);
260                 up_write(&mirror->hmm->mirrors_sem);
261         }
262
263         return 0;
264 }
265 EXPORT_SYMBOL(hmm_mirror_register);
266
267 /*
268  * hmm_mirror_unregister() - unregister a mirror
269  *
270  * @mirror: new mirror struct to register
271  *
272  * Stop mirroring a process address space, and cleanup.
273  */
274 void hmm_mirror_unregister(struct hmm_mirror *mirror)
275 {
276         bool should_unregister = false;
277         struct mm_struct *mm;
278         struct hmm *hmm;
279
280         if (mirror->hmm == NULL)
281                 return;
282
283         hmm = mirror->hmm;
284         down_write(&hmm->mirrors_sem);
285         list_del_init(&mirror->list);
286         should_unregister = list_empty(&hmm->mirrors);
287         mirror->hmm = NULL;
288         mm = hmm->mm;
289         hmm->mm = NULL;
290         up_write(&hmm->mirrors_sem);
291
292         if (!should_unregister || mm == NULL)
293                 return;
294
295         mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm);
296
297         spin_lock(&mm->page_table_lock);
298         if (mm->hmm == hmm)
299                 mm->hmm = NULL;
300         spin_unlock(&mm->page_table_lock);
301
302         kfree(hmm);
303 }
304 EXPORT_SYMBOL(hmm_mirror_unregister);
305
306 struct hmm_vma_walk {
307         struct hmm_range        *range;
308         unsigned long           last;
309         bool                    fault;
310         bool                    block;
311 };
312
313 static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
314                             bool write_fault, uint64_t *pfn)
315 {
316         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
317         struct hmm_vma_walk *hmm_vma_walk = walk->private;
318         struct hmm_range *range = hmm_vma_walk->range;
319         struct vm_area_struct *vma = walk->vma;
320         vm_fault_t ret;
321
322         flags |= hmm_vma_walk->block ? 0 : FAULT_FLAG_ALLOW_RETRY;
323         flags |= write_fault ? FAULT_FLAG_WRITE : 0;
324         ret = handle_mm_fault(vma, addr, flags);
325         if (ret & VM_FAULT_RETRY)
326                 return -EBUSY;
327         if (ret & VM_FAULT_ERROR) {
328                 *pfn = range->values[HMM_PFN_ERROR];
329                 return -EFAULT;
330         }
331
332         return -EAGAIN;
333 }
334
335 static int hmm_pfns_bad(unsigned long addr,
336                         unsigned long end,
337                         struct mm_walk *walk)
338 {
339         struct hmm_vma_walk *hmm_vma_walk = walk->private;
340         struct hmm_range *range = hmm_vma_walk->range;
341         uint64_t *pfns = range->pfns;
342         unsigned long i;
343
344         i = (addr - range->start) >> PAGE_SHIFT;
345         for (; addr < end; addr += PAGE_SIZE, i++)
346                 pfns[i] = range->values[HMM_PFN_ERROR];
347
348         return 0;
349 }
350
351 /*
352  * hmm_vma_walk_hole() - handle a range lacking valid pmd or pte(s)
353  * @start: range virtual start address (inclusive)
354  * @end: range virtual end address (exclusive)
355  * @fault: should we fault or not ?
356  * @write_fault: write fault ?
357  * @walk: mm_walk structure
358  * Returns: 0 on success, -EAGAIN after page fault, or page fault error
359  *
360  * This function will be called whenever pmd_none() or pte_none() returns true,
361  * or whenever there is no page directory covering the virtual address range.
362  */
363 static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
364                               bool fault, bool write_fault,
365                               struct mm_walk *walk)
366 {
367         struct hmm_vma_walk *hmm_vma_walk = walk->private;
368         struct hmm_range *range = hmm_vma_walk->range;
369         uint64_t *pfns = range->pfns;
370         unsigned long i;
371
372         hmm_vma_walk->last = addr;
373         i = (addr - range->start) >> PAGE_SHIFT;
374         for (; addr < end; addr += PAGE_SIZE, i++) {
375                 pfns[i] = range->values[HMM_PFN_NONE];
376                 if (fault || write_fault) {
377                         int ret;
378
379                         ret = hmm_vma_do_fault(walk, addr, write_fault,
380                                                &pfns[i]);
381                         if (ret != -EAGAIN)
382                                 return ret;
383                 }
384         }
385
386         return (fault || write_fault) ? -EAGAIN : 0;
387 }
388
389 static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
390                                       uint64_t pfns, uint64_t cpu_flags,
391                                       bool *fault, bool *write_fault)
392 {
393         struct hmm_range *range = hmm_vma_walk->range;
394
395         *fault = *write_fault = false;
396         if (!hmm_vma_walk->fault)
397                 return;
398
399         /* We aren't ask to do anything ... */
400         if (!(pfns & range->flags[HMM_PFN_VALID]))
401                 return;
402         /* If this is device memory than only fault if explicitly requested */
403         if ((cpu_flags & range->flags[HMM_PFN_DEVICE_PRIVATE])) {
404                 /* Do we fault on device memory ? */
405                 if (pfns & range->flags[HMM_PFN_DEVICE_PRIVATE]) {
406                         *write_fault = pfns & range->flags[HMM_PFN_WRITE];
407                         *fault = true;
408                 }
409                 return;
410         }
411
412         /* If CPU page table is not valid then we need to fault */
413         *fault = !(cpu_flags & range->flags[HMM_PFN_VALID]);
414         /* Need to write fault ? */
415         if ((pfns & range->flags[HMM_PFN_WRITE]) &&
416             !(cpu_flags & range->flags[HMM_PFN_WRITE])) {
417                 *write_fault = true;
418                 *fault = true;
419         }
420 }
421
422 static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
423                                  const uint64_t *pfns, unsigned long npages,
424                                  uint64_t cpu_flags, bool *fault,
425                                  bool *write_fault)
426 {
427         unsigned long i;
428
429         if (!hmm_vma_walk->fault) {
430                 *fault = *write_fault = false;
431                 return;
432         }
433
434         for (i = 0; i < npages; ++i) {
435                 hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags,
436                                    fault, write_fault);
437                 if ((*fault) || (*write_fault))
438                         return;
439         }
440 }
441
442 static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
443                              struct mm_walk *walk)
444 {
445         struct hmm_vma_walk *hmm_vma_walk = walk->private;
446         struct hmm_range *range = hmm_vma_walk->range;
447         bool fault, write_fault;
448         unsigned long i, npages;
449         uint64_t *pfns;
450
451         i = (addr - range->start) >> PAGE_SHIFT;
452         npages = (end - addr) >> PAGE_SHIFT;
453         pfns = &range->pfns[i];
454         hmm_range_need_fault(hmm_vma_walk, pfns, npages,
455                              0, &fault, &write_fault);
456         return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
457 }
458
459 static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
460 {
461         if (pmd_protnone(pmd))
462                 return 0;
463         return pmd_write(pmd) ? range->flags[HMM_PFN_VALID] |
464                                 range->flags[HMM_PFN_WRITE] :
465                                 range->flags[HMM_PFN_VALID];
466 }
467
468 static int hmm_vma_handle_pmd(struct mm_walk *walk,
469                               unsigned long addr,
470                               unsigned long end,
471                               uint64_t *pfns,
472                               pmd_t pmd)
473 {
474         struct hmm_vma_walk *hmm_vma_walk = walk->private;
475         struct hmm_range *range = hmm_vma_walk->range;
476         unsigned long pfn, npages, i;
477         bool fault, write_fault;
478         uint64_t cpu_flags;
479
480         npages = (end - addr) >> PAGE_SHIFT;
481         cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
482         hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags,
483                              &fault, &write_fault);
484
485         if (pmd_protnone(pmd) || fault || write_fault)
486                 return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
487
488         pfn = pmd_pfn(pmd) + pte_index(addr);
489         for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
490                 pfns[i] = hmm_pfn_from_pfn(range, pfn) | cpu_flags;
491         hmm_vma_walk->last = end;
492         return 0;
493 }
494
495 static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
496 {
497         if (pte_none(pte) || !pte_present(pte))
498                 return 0;
499         return pte_write(pte) ? range->flags[HMM_PFN_VALID] |
500                                 range->flags[HMM_PFN_WRITE] :
501                                 range->flags[HMM_PFN_VALID];
502 }
503
504 static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
505                               unsigned long end, pmd_t *pmdp, pte_t *ptep,
506                               uint64_t *pfn)
507 {
508         struct hmm_vma_walk *hmm_vma_walk = walk->private;
509         struct hmm_range *range = hmm_vma_walk->range;
510         struct vm_area_struct *vma = walk->vma;
511         bool fault, write_fault;
512         uint64_t cpu_flags;
513         pte_t pte = *ptep;
514         uint64_t orig_pfn = *pfn;
515
516         *pfn = range->values[HMM_PFN_NONE];
517         cpu_flags = pte_to_hmm_pfn_flags(range, pte);
518         hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
519                            &fault, &write_fault);
520
521         if (pte_none(pte)) {
522                 if (fault || write_fault)
523                         goto fault;
524                 return 0;
525         }
526
527         if (!pte_present(pte)) {
528                 swp_entry_t entry = pte_to_swp_entry(pte);
529
530                 if (!non_swap_entry(entry)) {
531                         if (fault || write_fault)
532                                 goto fault;
533                         return 0;
534                 }
535
536                 /*
537                  * This is a special swap entry, ignore migration, use
538                  * device and report anything else as error.
539                  */
540                 if (is_device_private_entry(entry)) {
541                         cpu_flags = range->flags[HMM_PFN_VALID] |
542                                 range->flags[HMM_PFN_DEVICE_PRIVATE];
543                         cpu_flags |= is_write_device_private_entry(entry) ?
544                                 range->flags[HMM_PFN_WRITE] : 0;
545                         hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
546                                            &fault, &write_fault);
547                         if (fault || write_fault)
548                                 goto fault;
549                         *pfn = hmm_pfn_from_pfn(range, swp_offset(entry));
550                         *pfn |= cpu_flags;
551                         return 0;
552                 }
553
554                 if (is_migration_entry(entry)) {
555                         if (fault || write_fault) {
556                                 pte_unmap(ptep);
557                                 hmm_vma_walk->last = addr;
558                                 migration_entry_wait(vma->vm_mm,
559                                                      pmdp, addr);
560                                 return -EAGAIN;
561                         }
562                         return 0;
563                 }
564
565                 /* Report error for everything else */
566                 *pfn = range->values[HMM_PFN_ERROR];
567                 return -EFAULT;
568         }
569
570         if (fault || write_fault)
571                 goto fault;
572
573         *pfn = hmm_pfn_from_pfn(range, pte_pfn(pte)) | cpu_flags;
574         return 0;
575
576 fault:
577         pte_unmap(ptep);
578         /* Fault any virtual address we were asked to fault */
579         return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
580 }
581
582 static int hmm_vma_walk_pmd(pmd_t *pmdp,
583                             unsigned long start,
584                             unsigned long end,
585                             struct mm_walk *walk)
586 {
587         struct hmm_vma_walk *hmm_vma_walk = walk->private;
588         struct hmm_range *range = hmm_vma_walk->range;
589         struct vm_area_struct *vma = walk->vma;
590         uint64_t *pfns = range->pfns;
591         unsigned long addr = start, i;
592         pte_t *ptep;
593         pmd_t pmd;
594
595
596 again:
597         pmd = READ_ONCE(*pmdp);
598         if (pmd_none(pmd))
599                 return hmm_vma_walk_hole(start, end, walk);
600
601         if (pmd_huge(pmd) && (range->vma->vm_flags & VM_HUGETLB))
602                 return hmm_pfns_bad(start, end, walk);
603
604         if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
605                 bool fault, write_fault;
606                 unsigned long npages;
607                 uint64_t *pfns;
608
609                 i = (addr - range->start) >> PAGE_SHIFT;
610                 npages = (end - addr) >> PAGE_SHIFT;
611                 pfns = &range->pfns[i];
612
613                 hmm_range_need_fault(hmm_vma_walk, pfns, npages,
614                                      0, &fault, &write_fault);
615                 if (fault || write_fault) {
616                         hmm_vma_walk->last = addr;
617                         pmd_migration_entry_wait(vma->vm_mm, pmdp);
618                         return -EAGAIN;
619                 }
620                 return 0;
621         } else if (!pmd_present(pmd))
622                 return hmm_pfns_bad(start, end, walk);
623
624         if (pmd_devmap(pmd) || pmd_trans_huge(pmd)) {
625                 /*
626                  * No need to take pmd_lock here, even if some other threads
627                  * is splitting the huge pmd we will get that event through
628                  * mmu_notifier callback.
629                  *
630                  * So just read pmd value and check again its a transparent
631                  * huge or device mapping one and compute corresponding pfn
632                  * values.
633                  */
634                 pmd = pmd_read_atomic(pmdp);
635                 barrier();
636                 if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
637                         goto again;
638
639                 i = (addr - range->start) >> PAGE_SHIFT;
640                 return hmm_vma_handle_pmd(walk, addr, end, &pfns[i], pmd);
641         }
642
643         /*
644          * We have handled all the valid case above ie either none, migration,
645          * huge or transparent huge. At this point either it is a valid pmd
646          * entry pointing to pte directory or it is a bad pmd that will not
647          * recover.
648          */
649         if (pmd_bad(pmd))
650                 return hmm_pfns_bad(start, end, walk);
651
652         ptep = pte_offset_map(pmdp, addr);
653         i = (addr - range->start) >> PAGE_SHIFT;
654         for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
655                 int r;
656
657                 r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i]);
658                 if (r) {
659                         /* hmm_vma_handle_pte() did unmap pte directory */
660                         hmm_vma_walk->last = addr;
661                         return r;
662                 }
663         }
664         pte_unmap(ptep - 1);
665
666         hmm_vma_walk->last = addr;
667         return 0;
668 }
669
670 static void hmm_pfns_clear(struct hmm_range *range,
671                            uint64_t *pfns,
672                            unsigned long addr,
673                            unsigned long end)
674 {
675         for (; addr < end; addr += PAGE_SIZE, pfns++)
676                 *pfns = range->values[HMM_PFN_NONE];
677 }
678
679 static void hmm_pfns_special(struct hmm_range *range)
680 {
681         unsigned long addr = range->start, i = 0;
682
683         for (; addr < range->end; addr += PAGE_SIZE, i++)
684                 range->pfns[i] = range->values[HMM_PFN_SPECIAL];
685 }
686
687 /*
688  * hmm_vma_get_pfns() - snapshot CPU page table for a range of virtual addresses
689  * @range: range being snapshotted
690  * Returns: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
691  *          vma permission, 0 success
692  *
693  * This snapshots the CPU page table for a range of virtual addresses. Snapshot
694  * validity is tracked by range struct. See hmm_vma_range_done() for further
695  * information.
696  *
697  * The range struct is initialized here. It tracks the CPU page table, but only
698  * if the function returns success (0), in which case the caller must then call
699  * hmm_vma_range_done() to stop CPU page table update tracking on this range.
700  *
701  * NOT CALLING hmm_vma_range_done() IF FUNCTION RETURNS 0 WILL LEAD TO SERIOUS
702  * MEMORY CORRUPTION ! YOU HAVE BEEN WARNED !
703  */
704 int hmm_vma_get_pfns(struct hmm_range *range)
705 {
706         struct vm_area_struct *vma = range->vma;
707         struct hmm_vma_walk hmm_vma_walk;
708         struct mm_walk mm_walk;
709         struct hmm *hmm;
710
711         /* Sanity check, this really should not happen ! */
712         if (range->start < vma->vm_start || range->start >= vma->vm_end)
713                 return -EINVAL;
714         if (range->end < vma->vm_start || range->end > vma->vm_end)
715                 return -EINVAL;
716
717         hmm = hmm_register(vma->vm_mm);
718         if (!hmm)
719                 return -ENOMEM;
720         /* Caller must have registered a mirror, via hmm_mirror_register() ! */
721         if (!hmm->mmu_notifier.ops)
722                 return -EINVAL;
723
724         /* FIXME support hugetlb fs */
725         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
726                         vma_is_dax(vma)) {
727                 hmm_pfns_special(range);
728                 return -EINVAL;
729         }
730
731         if (!(vma->vm_flags & VM_READ)) {
732                 /*
733                  * If vma do not allow read access, then assume that it does
734                  * not allow write access, either. Architecture that allow
735                  * write without read access are not supported by HMM, because
736                  * operations such has atomic access would not work.
737                  */
738                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
739                 return -EPERM;
740         }
741
742         /* Initialize range to track CPU page table update */
743         spin_lock(&hmm->lock);
744         range->valid = true;
745         list_add_rcu(&range->list, &hmm->ranges);
746         spin_unlock(&hmm->lock);
747
748         hmm_vma_walk.fault = false;
749         hmm_vma_walk.range = range;
750         mm_walk.private = &hmm_vma_walk;
751
752         mm_walk.vma = vma;
753         mm_walk.mm = vma->vm_mm;
754         mm_walk.pte_entry = NULL;
755         mm_walk.test_walk = NULL;
756         mm_walk.hugetlb_entry = NULL;
757         mm_walk.pmd_entry = hmm_vma_walk_pmd;
758         mm_walk.pte_hole = hmm_vma_walk_hole;
759
760         walk_page_range(range->start, range->end, &mm_walk);
761         return 0;
762 }
763 EXPORT_SYMBOL(hmm_vma_get_pfns);
764
765 /*
766  * hmm_vma_range_done() - stop tracking change to CPU page table over a range
767  * @range: range being tracked
768  * Returns: false if range data has been invalidated, true otherwise
769  *
770  * Range struct is used to track updates to the CPU page table after a call to
771  * either hmm_vma_get_pfns() or hmm_vma_fault(). Once the device driver is done
772  * using the data,  or wants to lock updates to the data it got from those
773  * functions, it must call the hmm_vma_range_done() function, which will then
774  * stop tracking CPU page table updates.
775  *
776  * Note that device driver must still implement general CPU page table update
777  * tracking either by using hmm_mirror (see hmm_mirror_register()) or by using
778  * the mmu_notifier API directly.
779  *
780  * CPU page table update tracking done through hmm_range is only temporary and
781  * to be used while trying to duplicate CPU page table contents for a range of
782  * virtual addresses.
783  *
784  * There are two ways to use this :
785  * again:
786  *   hmm_vma_get_pfns(range); or hmm_vma_fault(...);
787  *   trans = device_build_page_table_update_transaction(pfns);
788  *   device_page_table_lock();
789  *   if (!hmm_vma_range_done(range)) {
790  *     device_page_table_unlock();
791  *     goto again;
792  *   }
793  *   device_commit_transaction(trans);
794  *   device_page_table_unlock();
795  *
796  * Or:
797  *   hmm_vma_get_pfns(range); or hmm_vma_fault(...);
798  *   device_page_table_lock();
799  *   hmm_vma_range_done(range);
800  *   device_update_page_table(range->pfns);
801  *   device_page_table_unlock();
802  */
803 bool hmm_vma_range_done(struct hmm_range *range)
804 {
805         unsigned long npages = (range->end - range->start) >> PAGE_SHIFT;
806         struct hmm *hmm;
807
808         if (range->end <= range->start) {
809                 BUG();
810                 return false;
811         }
812
813         hmm = hmm_register(range->vma->vm_mm);
814         if (!hmm) {
815                 memset(range->pfns, 0, sizeof(*range->pfns) * npages);
816                 return false;
817         }
818
819         spin_lock(&hmm->lock);
820         list_del_rcu(&range->list);
821         spin_unlock(&hmm->lock);
822
823         return range->valid;
824 }
825 EXPORT_SYMBOL(hmm_vma_range_done);
826
827 /*
828  * hmm_vma_fault() - try to fault some address in a virtual address range
829  * @range: range being faulted
830  * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
831  * Returns: 0 success, error otherwise (-EAGAIN means mmap_sem have been drop)
832  *
833  * This is similar to a regular CPU page fault except that it will not trigger
834  * any memory migration if the memory being faulted is not accessible by CPUs.
835  *
836  * On error, for one virtual address in the range, the function will mark the
837  * corresponding HMM pfn entry with an error flag.
838  *
839  * Expected use pattern:
840  * retry:
841  *   down_read(&mm->mmap_sem);
842  *   // Find vma and address device wants to fault, initialize hmm_pfn_t
843  *   // array accordingly
844  *   ret = hmm_vma_fault(range, write, block);
845  *   switch (ret) {
846  *   case -EAGAIN:
847  *     hmm_vma_range_done(range);
848  *     // You might want to rate limit or yield to play nicely, you may
849  *     // also commit any valid pfn in the array assuming that you are
850  *     // getting true from hmm_vma_range_monitor_end()
851  *     goto retry;
852  *   case 0:
853  *     break;
854  *   case -ENOMEM:
855  *   case -EINVAL:
856  *   case -EPERM:
857  *   default:
858  *     // Handle error !
859  *     up_read(&mm->mmap_sem)
860  *     return;
861  *   }
862  *   // Take device driver lock that serialize device page table update
863  *   driver_lock_device_page_table_update();
864  *   hmm_vma_range_done(range);
865  *   // Commit pfns we got from hmm_vma_fault()
866  *   driver_unlock_device_page_table_update();
867  *   up_read(&mm->mmap_sem)
868  *
869  * YOU MUST CALL hmm_vma_range_done() AFTER THIS FUNCTION RETURN SUCCESS (0)
870  * BEFORE FREEING THE range struct OR YOU WILL HAVE SERIOUS MEMORY CORRUPTION !
871  *
872  * YOU HAVE BEEN WARNED !
873  */
874 int hmm_vma_fault(struct hmm_range *range, bool block)
875 {
876         struct vm_area_struct *vma = range->vma;
877         unsigned long start = range->start;
878         struct hmm_vma_walk hmm_vma_walk;
879         struct mm_walk mm_walk;
880         struct hmm *hmm;
881         int ret;
882
883         /* Sanity check, this really should not happen ! */
884         if (range->start < vma->vm_start || range->start >= vma->vm_end)
885                 return -EINVAL;
886         if (range->end < vma->vm_start || range->end > vma->vm_end)
887                 return -EINVAL;
888
889         hmm = hmm_register(vma->vm_mm);
890         if (!hmm) {
891                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
892                 return -ENOMEM;
893         }
894         /* Caller must have registered a mirror using hmm_mirror_register() */
895         if (!hmm->mmu_notifier.ops)
896                 return -EINVAL;
897
898         /* FIXME support hugetlb fs */
899         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
900                         vma_is_dax(vma)) {
901                 hmm_pfns_special(range);
902                 return -EINVAL;
903         }
904
905         if (!(vma->vm_flags & VM_READ)) {
906                 /*
907                  * If vma do not allow read access, then assume that it does
908                  * not allow write access, either. Architecture that allow
909                  * write without read access are not supported by HMM, because
910                  * operations such has atomic access would not work.
911                  */
912                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
913                 return -EPERM;
914         }
915
916         /* Initialize range to track CPU page table update */
917         spin_lock(&hmm->lock);
918         range->valid = true;
919         list_add_rcu(&range->list, &hmm->ranges);
920         spin_unlock(&hmm->lock);
921
922         hmm_vma_walk.fault = true;
923         hmm_vma_walk.block = block;
924         hmm_vma_walk.range = range;
925         mm_walk.private = &hmm_vma_walk;
926         hmm_vma_walk.last = range->start;
927
928         mm_walk.vma = vma;
929         mm_walk.mm = vma->vm_mm;
930         mm_walk.pte_entry = NULL;
931         mm_walk.test_walk = NULL;
932         mm_walk.hugetlb_entry = NULL;
933         mm_walk.pmd_entry = hmm_vma_walk_pmd;
934         mm_walk.pte_hole = hmm_vma_walk_hole;
935
936         do {
937                 ret = walk_page_range(start, range->end, &mm_walk);
938                 start = hmm_vma_walk.last;
939         } while (ret == -EAGAIN);
940
941         if (ret) {
942                 unsigned long i;
943
944                 i = (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
945                 hmm_pfns_clear(range, &range->pfns[i], hmm_vma_walk.last,
946                                range->end);
947                 hmm_vma_range_done(range);
948         }
949         return ret;
950 }
951 EXPORT_SYMBOL(hmm_vma_fault);
952 #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
953
954
955 #if IS_ENABLED(CONFIG_DEVICE_PRIVATE) ||  IS_ENABLED(CONFIG_DEVICE_PUBLIC)
956 struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
957                                        unsigned long addr)
958 {
959         struct page *page;
960
961         page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
962         if (!page)
963                 return NULL;
964         lock_page(page);
965         return page;
966 }
967 EXPORT_SYMBOL(hmm_vma_alloc_locked_page);
968
969
970 static void hmm_devmem_ref_release(struct percpu_ref *ref)
971 {
972         struct hmm_devmem *devmem;
973
974         devmem = container_of(ref, struct hmm_devmem, ref);
975         complete(&devmem->completion);
976 }
977
978 static void hmm_devmem_ref_exit(void *data)
979 {
980         struct percpu_ref *ref = data;
981         struct hmm_devmem *devmem;
982
983         devmem = container_of(ref, struct hmm_devmem, ref);
984         wait_for_completion(&devmem->completion);
985         percpu_ref_exit(ref);
986 }
987
988 static void hmm_devmem_ref_kill(struct percpu_ref *ref)
989 {
990         percpu_ref_kill(ref);
991 }
992
993 static vm_fault_t hmm_devmem_fault(struct vm_area_struct *vma,
994                             unsigned long addr,
995                             const struct page *page,
996                             unsigned int flags,
997                             pmd_t *pmdp)
998 {
999         struct hmm_devmem *devmem = page->pgmap->data;
1000
1001         return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
1002 }
1003
1004 static void hmm_devmem_free(struct page *page, void *data)
1005 {
1006         struct hmm_devmem *devmem = data;
1007
1008         page->mapping = NULL;
1009
1010         devmem->ops->free(devmem, page);
1011 }
1012
1013 /*
1014  * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
1015  *
1016  * @ops: memory event device driver callback (see struct hmm_devmem_ops)
1017  * @device: device struct to bind the resource too
1018  * @size: size in bytes of the device memory to add
1019  * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise
1020  *
1021  * This function first finds an empty range of physical address big enough to
1022  * contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which
1023  * in turn allocates struct pages. It does not do anything beyond that; all
1024  * events affecting the memory will go through the various callbacks provided
1025  * by hmm_devmem_ops struct.
1026  *
1027  * Device driver should call this function during device initialization and
1028  * is then responsible of memory management. HMM only provides helpers.
1029  */
1030 struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
1031                                   struct device *device,
1032                                   unsigned long size)
1033 {
1034         struct hmm_devmem *devmem;
1035         resource_size_t addr;
1036         void *result;
1037         int ret;
1038
1039         dev_pagemap_get_ops();
1040
1041         devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
1042         if (!devmem)
1043                 return ERR_PTR(-ENOMEM);
1044
1045         init_completion(&devmem->completion);
1046         devmem->pfn_first = -1UL;
1047         devmem->pfn_last = -1UL;
1048         devmem->resource = NULL;
1049         devmem->device = device;
1050         devmem->ops = ops;
1051
1052         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1053                               0, GFP_KERNEL);
1054         if (ret)
1055                 return ERR_PTR(ret);
1056
1057         ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit, &devmem->ref);
1058         if (ret)
1059                 return ERR_PTR(ret);
1060
1061         size = ALIGN(size, PA_SECTION_SIZE);
1062         addr = min((unsigned long)iomem_resource.end,
1063                    (1UL << MAX_PHYSMEM_BITS) - 1);
1064         addr = addr - size + 1UL;
1065
1066         /*
1067          * FIXME add a new helper to quickly walk resource tree and find free
1068          * range
1069          *
1070          * FIXME what about ioport_resource resource ?
1071          */
1072         for (; addr > size && addr >= iomem_resource.start; addr -= size) {
1073                 ret = region_intersects(addr, size, 0, IORES_DESC_NONE);
1074                 if (ret != REGION_DISJOINT)
1075                         continue;
1076
1077                 devmem->resource = devm_request_mem_region(device, addr, size,
1078                                                            dev_name(device));
1079                 if (!devmem->resource)
1080                         return ERR_PTR(-ENOMEM);
1081                 break;
1082         }
1083         if (!devmem->resource)
1084                 return ERR_PTR(-ERANGE);
1085
1086         devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
1087         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1088         devmem->pfn_last = devmem->pfn_first +
1089                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1090         devmem->page_fault = hmm_devmem_fault;
1091
1092         devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
1093         devmem->pagemap.res = *devmem->resource;
1094         devmem->pagemap.page_free = hmm_devmem_free;
1095         devmem->pagemap.altmap_valid = false;
1096         devmem->pagemap.ref = &devmem->ref;
1097         devmem->pagemap.data = devmem;
1098         devmem->pagemap.kill = hmm_devmem_ref_kill;
1099
1100         result = devm_memremap_pages(devmem->device, &devmem->pagemap);
1101         if (IS_ERR(result))
1102                 return result;
1103         return devmem;
1104 }
1105 EXPORT_SYMBOL_GPL(hmm_devmem_add);
1106
1107 struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
1108                                            struct device *device,
1109                                            struct resource *res)
1110 {
1111         struct hmm_devmem *devmem;
1112         void *result;
1113         int ret;
1114
1115         if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY)
1116                 return ERR_PTR(-EINVAL);
1117
1118         dev_pagemap_get_ops();
1119
1120         devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
1121         if (!devmem)
1122                 return ERR_PTR(-ENOMEM);
1123
1124         init_completion(&devmem->completion);
1125         devmem->pfn_first = -1UL;
1126         devmem->pfn_last = -1UL;
1127         devmem->resource = res;
1128         devmem->device = device;
1129         devmem->ops = ops;
1130
1131         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1132                               0, GFP_KERNEL);
1133         if (ret)
1134                 return ERR_PTR(ret);
1135
1136         ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit,
1137                         &devmem->ref);
1138         if (ret)
1139                 return ERR_PTR(ret);
1140
1141         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1142         devmem->pfn_last = devmem->pfn_first +
1143                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1144         devmem->page_fault = hmm_devmem_fault;
1145
1146         devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
1147         devmem->pagemap.res = *devmem->resource;
1148         devmem->pagemap.page_free = hmm_devmem_free;
1149         devmem->pagemap.altmap_valid = false;
1150         devmem->pagemap.ref = &devmem->ref;
1151         devmem->pagemap.data = devmem;
1152         devmem->pagemap.kill = hmm_devmem_ref_kill;
1153
1154         result = devm_memremap_pages(devmem->device, &devmem->pagemap);
1155         if (IS_ERR(result))
1156                 return result;
1157         return devmem;
1158 }
1159 EXPORT_SYMBOL_GPL(hmm_devmem_add_resource);
1160
1161 /*
1162  * A device driver that wants to handle multiple devices memory through a
1163  * single fake device can use hmm_device to do so. This is purely a helper
1164  * and it is not needed to make use of any HMM functionality.
1165  */
1166 #define HMM_DEVICE_MAX 256
1167
1168 static DECLARE_BITMAP(hmm_device_mask, HMM_DEVICE_MAX);
1169 static DEFINE_SPINLOCK(hmm_device_lock);
1170 static struct class *hmm_device_class;
1171 static dev_t hmm_device_devt;
1172
1173 static void hmm_device_release(struct device *device)
1174 {
1175         struct hmm_device *hmm_device;
1176
1177         hmm_device = container_of(device, struct hmm_device, device);
1178         spin_lock(&hmm_device_lock);
1179         clear_bit(hmm_device->minor, hmm_device_mask);
1180         spin_unlock(&hmm_device_lock);
1181
1182         kfree(hmm_device);
1183 }
1184
1185 struct hmm_device *hmm_device_new(void *drvdata)
1186 {
1187         struct hmm_device *hmm_device;
1188
1189         hmm_device = kzalloc(sizeof(*hmm_device), GFP_KERNEL);
1190         if (!hmm_device)
1191                 return ERR_PTR(-ENOMEM);
1192
1193         spin_lock(&hmm_device_lock);
1194         hmm_device->minor = find_first_zero_bit(hmm_device_mask, HMM_DEVICE_MAX);
1195         if (hmm_device->minor >= HMM_DEVICE_MAX) {
1196                 spin_unlock(&hmm_device_lock);
1197                 kfree(hmm_device);
1198                 return ERR_PTR(-EBUSY);
1199         }
1200         set_bit(hmm_device->minor, hmm_device_mask);
1201         spin_unlock(&hmm_device_lock);
1202
1203         dev_set_name(&hmm_device->device, "hmm_device%d", hmm_device->minor);
1204         hmm_device->device.devt = MKDEV(MAJOR(hmm_device_devt),
1205                                         hmm_device->minor);
1206         hmm_device->device.release = hmm_device_release;
1207         dev_set_drvdata(&hmm_device->device, drvdata);
1208         hmm_device->device.class = hmm_device_class;
1209         device_initialize(&hmm_device->device);
1210
1211         return hmm_device;
1212 }
1213 EXPORT_SYMBOL(hmm_device_new);
1214
1215 void hmm_device_put(struct hmm_device *hmm_device)
1216 {
1217         put_device(&hmm_device->device);
1218 }
1219 EXPORT_SYMBOL(hmm_device_put);
1220
1221 static int __init hmm_init(void)
1222 {
1223         int ret;
1224
1225         ret = alloc_chrdev_region(&hmm_device_devt, 0,
1226                                   HMM_DEVICE_MAX,
1227                                   "hmm_device");
1228         if (ret)
1229                 return ret;
1230
1231         hmm_device_class = class_create(THIS_MODULE, "hmm_device");
1232         if (IS_ERR(hmm_device_class)) {
1233                 unregister_chrdev_region(hmm_device_devt, HMM_DEVICE_MAX);
1234                 return PTR_ERR(hmm_device_class);
1235         }
1236         return 0;
1237 }
1238
1239 device_initcall(hmm_init);
1240 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */