GNU Linux-libre 4.19.211-gnu1
[releases.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  * @sequence: we track updates to the CPU page table with a sequence number
47  * @ranges: list of range being snapshotted
48  * @mirrors: list of mirrors for this mm
49  * @mmu_notifier: mmu notifier to track updates to CPU page table
50  * @mirrors_sem: read/write semaphore protecting the mirrors list
51  */
52 struct hmm {
53         struct mm_struct        *mm;
54         spinlock_t              lock;
55         atomic_t                sequence;
56         struct list_head        ranges;
57         struct list_head        mirrors;
58         struct mmu_notifier     mmu_notifier;
59         struct rw_semaphore     mirrors_sem;
60 };
61
62 /*
63  * hmm_register - register HMM against an mm (HMM internal)
64  *
65  * @mm: mm struct to attach to
66  *
67  * This is not intended to be used directly by device drivers. It allocates an
68  * HMM struct if mm does not have one, and initializes it.
69  */
70 static struct hmm *hmm_register(struct mm_struct *mm)
71 {
72         struct hmm *hmm = READ_ONCE(mm->hmm);
73         bool cleanup = false;
74
75         /*
76          * The hmm struct can only be freed once the mm_struct goes away,
77          * hence we should always have pre-allocated an new hmm struct
78          * above.
79          */
80         if (hmm)
81                 return hmm;
82
83         hmm = kmalloc(sizeof(*hmm), GFP_KERNEL);
84         if (!hmm)
85                 return NULL;
86         INIT_LIST_HEAD(&hmm->mirrors);
87         init_rwsem(&hmm->mirrors_sem);
88         atomic_set(&hmm->sequence, 0);
89         hmm->mmu_notifier.ops = NULL;
90         INIT_LIST_HEAD(&hmm->ranges);
91         spin_lock_init(&hmm->lock);
92         hmm->mm = mm;
93
94         spin_lock(&mm->page_table_lock);
95         if (!mm->hmm)
96                 mm->hmm = hmm;
97         else
98                 cleanup = true;
99         spin_unlock(&mm->page_table_lock);
100
101         if (cleanup)
102                 goto error;
103
104         /*
105          * We should only get here if hold the mmap_sem in write mode ie on
106          * registration of first mirror through hmm_mirror_register()
107          */
108         hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops;
109         if (__mmu_notifier_register(&hmm->mmu_notifier, mm))
110                 goto error_mm;
111
112         return mm->hmm;
113
114 error_mm:
115         spin_lock(&mm->page_table_lock);
116         if (mm->hmm == hmm)
117                 mm->hmm = NULL;
118         spin_unlock(&mm->page_table_lock);
119 error:
120         kfree(hmm);
121         return NULL;
122 }
123
124 void hmm_mm_destroy(struct mm_struct *mm)
125 {
126         kfree(mm->hmm);
127 }
128
129 static void hmm_invalidate_range(struct hmm *hmm,
130                                  enum hmm_update_type action,
131                                  unsigned long start,
132                                  unsigned long end)
133 {
134         struct hmm_mirror *mirror;
135         struct hmm_range *range;
136
137         spin_lock(&hmm->lock);
138         list_for_each_entry(range, &hmm->ranges, list) {
139                 unsigned long addr, idx, npages;
140
141                 if (end < range->start || start >= range->end)
142                         continue;
143
144                 range->valid = false;
145                 addr = max(start, range->start);
146                 idx = (addr - range->start) >> PAGE_SHIFT;
147                 npages = (min(range->end, end) - addr) >> PAGE_SHIFT;
148                 memset(&range->pfns[idx], 0, sizeof(*range->pfns) * npages);
149         }
150         spin_unlock(&hmm->lock);
151
152         down_read(&hmm->mirrors_sem);
153         list_for_each_entry(mirror, &hmm->mirrors, list)
154                 mirror->ops->sync_cpu_device_pagetables(mirror, action,
155                                                         start, end);
156         up_read(&hmm->mirrors_sem);
157 }
158
159 static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
160 {
161         struct hmm_mirror *mirror;
162         struct hmm *hmm = mm->hmm;
163
164         down_write(&hmm->mirrors_sem);
165         mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror,
166                                           list);
167         while (mirror) {
168                 list_del_init(&mirror->list);
169                 if (mirror->ops->release) {
170                         /*
171                          * Drop mirrors_sem so callback can wait on any pending
172                          * work that might itself trigger mmu_notifier callback
173                          * and thus would deadlock with us.
174                          */
175                         up_write(&hmm->mirrors_sem);
176                         mirror->ops->release(mirror);
177                         down_write(&hmm->mirrors_sem);
178                 }
179                 mirror = list_first_entry_or_null(&hmm->mirrors,
180                                                   struct hmm_mirror, list);
181         }
182         up_write(&hmm->mirrors_sem);
183 }
184
185 static int hmm_invalidate_range_start(struct mmu_notifier *mn,
186                                        struct mm_struct *mm,
187                                        unsigned long start,
188                                        unsigned long end,
189                                        bool blockable)
190 {
191         struct hmm *hmm = mm->hmm;
192
193         VM_BUG_ON(!hmm);
194
195         atomic_inc(&hmm->sequence);
196
197         return 0;
198 }
199
200 static void hmm_invalidate_range_end(struct mmu_notifier *mn,
201                                      struct mm_struct *mm,
202                                      unsigned long start,
203                                      unsigned long end)
204 {
205         struct hmm *hmm = mm->hmm;
206
207         VM_BUG_ON(!hmm);
208
209         hmm_invalidate_range(mm->hmm, HMM_UPDATE_INVALIDATE, start, end);
210 }
211
212 static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
213         .release                = hmm_release,
214         .invalidate_range_start = hmm_invalidate_range_start,
215         .invalidate_range_end   = hmm_invalidate_range_end,
216 };
217
218 /*
219  * hmm_mirror_register() - register a mirror against an mm
220  *
221  * @mirror: new mirror struct to register
222  * @mm: mm to register against
223  *
224  * To start mirroring a process address space, the device driver must register
225  * an HMM mirror struct.
226  *
227  * THE mm->mmap_sem MUST BE HELD IN WRITE MODE !
228  */
229 int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
230 {
231         /* Sanity check */
232         if (!mm || !mirror || !mirror->ops)
233                 return -EINVAL;
234
235 again:
236         mirror->hmm = hmm_register(mm);
237         if (!mirror->hmm)
238                 return -ENOMEM;
239
240         down_write(&mirror->hmm->mirrors_sem);
241         if (mirror->hmm->mm == NULL) {
242                 /*
243                  * A racing hmm_mirror_unregister() is about to destroy the hmm
244                  * struct. Try again to allocate a new one.
245                  */
246                 up_write(&mirror->hmm->mirrors_sem);
247                 mirror->hmm = NULL;
248                 goto again;
249         } else {
250                 list_add(&mirror->list, &mirror->hmm->mirrors);
251                 up_write(&mirror->hmm->mirrors_sem);
252         }
253
254         return 0;
255 }
256 EXPORT_SYMBOL(hmm_mirror_register);
257
258 /*
259  * hmm_mirror_unregister() - unregister a mirror
260  *
261  * @mirror: new mirror struct to register
262  *
263  * Stop mirroring a process address space, and cleanup.
264  */
265 void hmm_mirror_unregister(struct hmm_mirror *mirror)
266 {
267         bool should_unregister = false;
268         struct mm_struct *mm;
269         struct hmm *hmm;
270
271         if (mirror->hmm == NULL)
272                 return;
273
274         hmm = mirror->hmm;
275         down_write(&hmm->mirrors_sem);
276         list_del_init(&mirror->list);
277         should_unregister = list_empty(&hmm->mirrors);
278         mirror->hmm = NULL;
279         mm = hmm->mm;
280         hmm->mm = NULL;
281         up_write(&hmm->mirrors_sem);
282
283         if (!should_unregister || mm == NULL)
284                 return;
285
286         mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm);
287
288         spin_lock(&mm->page_table_lock);
289         if (mm->hmm == hmm)
290                 mm->hmm = NULL;
291         spin_unlock(&mm->page_table_lock);
292
293         kfree(hmm);
294 }
295 EXPORT_SYMBOL(hmm_mirror_unregister);
296
297 struct hmm_vma_walk {
298         struct hmm_range        *range;
299         unsigned long           last;
300         bool                    fault;
301         bool                    block;
302 };
303
304 static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
305                             bool write_fault, uint64_t *pfn)
306 {
307         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
308         struct hmm_vma_walk *hmm_vma_walk = walk->private;
309         struct hmm_range *range = hmm_vma_walk->range;
310         struct vm_area_struct *vma = walk->vma;
311         vm_fault_t ret;
312
313         flags |= hmm_vma_walk->block ? 0 : FAULT_FLAG_ALLOW_RETRY;
314         flags |= write_fault ? FAULT_FLAG_WRITE : 0;
315         ret = handle_mm_fault(vma, addr, flags);
316         if (ret & VM_FAULT_RETRY)
317                 return -EBUSY;
318         if (ret & VM_FAULT_ERROR) {
319                 *pfn = range->values[HMM_PFN_ERROR];
320                 return -EFAULT;
321         }
322
323         return -EAGAIN;
324 }
325
326 static int hmm_pfns_bad(unsigned long addr,
327                         unsigned long end,
328                         struct mm_walk *walk)
329 {
330         struct hmm_vma_walk *hmm_vma_walk = walk->private;
331         struct hmm_range *range = hmm_vma_walk->range;
332         uint64_t *pfns = range->pfns;
333         unsigned long i;
334
335         i = (addr - range->start) >> PAGE_SHIFT;
336         for (; addr < end; addr += PAGE_SIZE, i++)
337                 pfns[i] = range->values[HMM_PFN_ERROR];
338
339         return 0;
340 }
341
342 /*
343  * hmm_vma_walk_hole() - handle a range lacking valid pmd or pte(s)
344  * @start: range virtual start address (inclusive)
345  * @end: range virtual end address (exclusive)
346  * @fault: should we fault or not ?
347  * @write_fault: write fault ?
348  * @walk: mm_walk structure
349  * Returns: 0 on success, -EAGAIN after page fault, or page fault error
350  *
351  * This function will be called whenever pmd_none() or pte_none() returns true,
352  * or whenever there is no page directory covering the virtual address range.
353  */
354 static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
355                               bool fault, bool write_fault,
356                               struct mm_walk *walk)
357 {
358         struct hmm_vma_walk *hmm_vma_walk = walk->private;
359         struct hmm_range *range = hmm_vma_walk->range;
360         uint64_t *pfns = range->pfns;
361         unsigned long i;
362
363         hmm_vma_walk->last = addr;
364         i = (addr - range->start) >> PAGE_SHIFT;
365         for (; addr < end; addr += PAGE_SIZE, i++) {
366                 pfns[i] = range->values[HMM_PFN_NONE];
367                 if (fault || write_fault) {
368                         int ret;
369
370                         ret = hmm_vma_do_fault(walk, addr, write_fault,
371                                                &pfns[i]);
372                         if (ret != -EAGAIN)
373                                 return ret;
374                 }
375         }
376
377         return (fault || write_fault) ? -EAGAIN : 0;
378 }
379
380 static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
381                                       uint64_t pfns, uint64_t cpu_flags,
382                                       bool *fault, bool *write_fault)
383 {
384         struct hmm_range *range = hmm_vma_walk->range;
385
386         *fault = *write_fault = false;
387         if (!hmm_vma_walk->fault)
388                 return;
389
390         /* We aren't ask to do anything ... */
391         if (!(pfns & range->flags[HMM_PFN_VALID]))
392                 return;
393         /* If this is device memory than only fault if explicitly requested */
394         if ((cpu_flags & range->flags[HMM_PFN_DEVICE_PRIVATE])) {
395                 /* Do we fault on device memory ? */
396                 if (pfns & range->flags[HMM_PFN_DEVICE_PRIVATE]) {
397                         *write_fault = pfns & range->flags[HMM_PFN_WRITE];
398                         *fault = true;
399                 }
400                 return;
401         }
402
403         /* If CPU page table is not valid then we need to fault */
404         *fault = !(cpu_flags & range->flags[HMM_PFN_VALID]);
405         /* Need to write fault ? */
406         if ((pfns & range->flags[HMM_PFN_WRITE]) &&
407             !(cpu_flags & range->flags[HMM_PFN_WRITE])) {
408                 *write_fault = true;
409                 *fault = true;
410         }
411 }
412
413 static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
414                                  const uint64_t *pfns, unsigned long npages,
415                                  uint64_t cpu_flags, bool *fault,
416                                  bool *write_fault)
417 {
418         unsigned long i;
419
420         if (!hmm_vma_walk->fault) {
421                 *fault = *write_fault = false;
422                 return;
423         }
424
425         for (i = 0; i < npages; ++i) {
426                 hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags,
427                                    fault, write_fault);
428                 if ((*fault) || (*write_fault))
429                         return;
430         }
431 }
432
433 static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
434                              struct mm_walk *walk)
435 {
436         struct hmm_vma_walk *hmm_vma_walk = walk->private;
437         struct hmm_range *range = hmm_vma_walk->range;
438         bool fault, write_fault;
439         unsigned long i, npages;
440         uint64_t *pfns;
441
442         i = (addr - range->start) >> PAGE_SHIFT;
443         npages = (end - addr) >> PAGE_SHIFT;
444         pfns = &range->pfns[i];
445         hmm_range_need_fault(hmm_vma_walk, pfns, npages,
446                              0, &fault, &write_fault);
447         return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
448 }
449
450 static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
451 {
452         if (pmd_protnone(pmd))
453                 return 0;
454         return pmd_write(pmd) ? range->flags[HMM_PFN_VALID] |
455                                 range->flags[HMM_PFN_WRITE] :
456                                 range->flags[HMM_PFN_VALID];
457 }
458
459 static int hmm_vma_handle_pmd(struct mm_walk *walk,
460                               unsigned long addr,
461                               unsigned long end,
462                               uint64_t *pfns,
463                               pmd_t pmd)
464 {
465         struct hmm_vma_walk *hmm_vma_walk = walk->private;
466         struct hmm_range *range = hmm_vma_walk->range;
467         unsigned long pfn, npages, i;
468         bool fault, write_fault;
469         uint64_t cpu_flags;
470
471         npages = (end - addr) >> PAGE_SHIFT;
472         cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
473         hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags,
474                              &fault, &write_fault);
475
476         if (pmd_protnone(pmd) || fault || write_fault)
477                 return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
478
479         pfn = pmd_pfn(pmd) + pte_index(addr);
480         for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
481                 pfns[i] = hmm_pfn_from_pfn(range, pfn) | cpu_flags;
482         hmm_vma_walk->last = end;
483         return 0;
484 }
485
486 static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
487 {
488         if (pte_none(pte) || !pte_present(pte))
489                 return 0;
490         return pte_write(pte) ? range->flags[HMM_PFN_VALID] |
491                                 range->flags[HMM_PFN_WRITE] :
492                                 range->flags[HMM_PFN_VALID];
493 }
494
495 static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
496                               unsigned long end, pmd_t *pmdp, pte_t *ptep,
497                               uint64_t *pfn)
498 {
499         struct hmm_vma_walk *hmm_vma_walk = walk->private;
500         struct hmm_range *range = hmm_vma_walk->range;
501         struct vm_area_struct *vma = walk->vma;
502         bool fault, write_fault;
503         uint64_t cpu_flags;
504         pte_t pte = *ptep;
505         uint64_t orig_pfn = *pfn;
506
507         *pfn = range->values[HMM_PFN_NONE];
508         cpu_flags = pte_to_hmm_pfn_flags(range, pte);
509         hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
510                            &fault, &write_fault);
511
512         if (pte_none(pte)) {
513                 if (fault || write_fault)
514                         goto fault;
515                 return 0;
516         }
517
518         if (!pte_present(pte)) {
519                 swp_entry_t entry = pte_to_swp_entry(pte);
520
521                 if (!non_swap_entry(entry)) {
522                         if (fault || write_fault)
523                                 goto fault;
524                         return 0;
525                 }
526
527                 /*
528                  * This is a special swap entry, ignore migration, use
529                  * device and report anything else as error.
530                  */
531                 if (is_device_private_entry(entry)) {
532                         cpu_flags = range->flags[HMM_PFN_VALID] |
533                                 range->flags[HMM_PFN_DEVICE_PRIVATE];
534                         cpu_flags |= is_write_device_private_entry(entry) ?
535                                 range->flags[HMM_PFN_WRITE] : 0;
536                         hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
537                                            &fault, &write_fault);
538                         if (fault || write_fault)
539                                 goto fault;
540                         *pfn = hmm_pfn_from_pfn(range, swp_offset(entry));
541                         *pfn |= cpu_flags;
542                         return 0;
543                 }
544
545                 if (is_migration_entry(entry)) {
546                         if (fault || write_fault) {
547                                 pte_unmap(ptep);
548                                 hmm_vma_walk->last = addr;
549                                 migration_entry_wait(vma->vm_mm,
550                                                      pmdp, addr);
551                                 return -EAGAIN;
552                         }
553                         return 0;
554                 }
555
556                 /* Report error for everything else */
557                 *pfn = range->values[HMM_PFN_ERROR];
558                 return -EFAULT;
559         }
560
561         if (fault || write_fault)
562                 goto fault;
563
564         *pfn = hmm_pfn_from_pfn(range, pte_pfn(pte)) | cpu_flags;
565         return 0;
566
567 fault:
568         pte_unmap(ptep);
569         /* Fault any virtual address we were asked to fault */
570         return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
571 }
572
573 static int hmm_vma_walk_pmd(pmd_t *pmdp,
574                             unsigned long start,
575                             unsigned long end,
576                             struct mm_walk *walk)
577 {
578         struct hmm_vma_walk *hmm_vma_walk = walk->private;
579         struct hmm_range *range = hmm_vma_walk->range;
580         uint64_t *pfns = range->pfns;
581         unsigned long addr = start, i;
582         pte_t *ptep;
583
584         i = (addr - range->start) >> PAGE_SHIFT;
585
586 again:
587         if (pmd_none(*pmdp))
588                 return hmm_vma_walk_hole(start, end, walk);
589
590         if (pmd_huge(*pmdp) && (range->vma->vm_flags & VM_HUGETLB))
591                 return hmm_pfns_bad(start, end, walk);
592
593         if (pmd_devmap(*pmdp) || pmd_trans_huge(*pmdp)) {
594                 pmd_t pmd;
595
596                 /*
597                  * No need to take pmd_lock here, even if some other threads
598                  * is splitting the huge pmd we will get that event through
599                  * mmu_notifier callback.
600                  *
601                  * So just read pmd value and check again its a transparent
602                  * huge or device mapping one and compute corresponding pfn
603                  * values.
604                  */
605                 pmd = pmd_read_atomic(pmdp);
606                 barrier();
607                 if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
608                         goto again;
609
610                 return hmm_vma_handle_pmd(walk, addr, end, &pfns[i], pmd);
611         }
612
613         if (pmd_bad(*pmdp))
614                 return hmm_pfns_bad(start, end, walk);
615
616         ptep = pte_offset_map(pmdp, addr);
617         for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
618                 int r;
619
620                 r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i]);
621                 if (r) {
622                         /* hmm_vma_handle_pte() did unmap pte directory */
623                         hmm_vma_walk->last = addr;
624                         return r;
625                 }
626         }
627         pte_unmap(ptep - 1);
628
629         hmm_vma_walk->last = addr;
630         return 0;
631 }
632
633 static void hmm_pfns_clear(struct hmm_range *range,
634                            uint64_t *pfns,
635                            unsigned long addr,
636                            unsigned long end)
637 {
638         for (; addr < end; addr += PAGE_SIZE, pfns++)
639                 *pfns = range->values[HMM_PFN_NONE];
640 }
641
642 static void hmm_pfns_special(struct hmm_range *range)
643 {
644         unsigned long addr = range->start, i = 0;
645
646         for (; addr < range->end; addr += PAGE_SIZE, i++)
647                 range->pfns[i] = range->values[HMM_PFN_SPECIAL];
648 }
649
650 /*
651  * hmm_vma_get_pfns() - snapshot CPU page table for a range of virtual addresses
652  * @range: range being snapshotted
653  * Returns: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
654  *          vma permission, 0 success
655  *
656  * This snapshots the CPU page table for a range of virtual addresses. Snapshot
657  * validity is tracked by range struct. See hmm_vma_range_done() for further
658  * information.
659  *
660  * The range struct is initialized here. It tracks the CPU page table, but only
661  * if the function returns success (0), in which case the caller must then call
662  * hmm_vma_range_done() to stop CPU page table update tracking on this range.
663  *
664  * NOT CALLING hmm_vma_range_done() IF FUNCTION RETURNS 0 WILL LEAD TO SERIOUS
665  * MEMORY CORRUPTION ! YOU HAVE BEEN WARNED !
666  */
667 int hmm_vma_get_pfns(struct hmm_range *range)
668 {
669         struct vm_area_struct *vma = range->vma;
670         struct hmm_vma_walk hmm_vma_walk;
671         struct mm_walk mm_walk;
672         struct hmm *hmm;
673
674         /* Sanity check, this really should not happen ! */
675         if (range->start < vma->vm_start || range->start >= vma->vm_end)
676                 return -EINVAL;
677         if (range->end < vma->vm_start || range->end > vma->vm_end)
678                 return -EINVAL;
679
680         hmm = hmm_register(vma->vm_mm);
681         if (!hmm)
682                 return -ENOMEM;
683         /* Caller must have registered a mirror, via hmm_mirror_register() ! */
684         if (!hmm->mmu_notifier.ops)
685                 return -EINVAL;
686
687         /* FIXME support hugetlb fs */
688         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
689                         vma_is_dax(vma)) {
690                 hmm_pfns_special(range);
691                 return -EINVAL;
692         }
693
694         if (!(vma->vm_flags & VM_READ)) {
695                 /*
696                  * If vma do not allow read access, then assume that it does
697                  * not allow write access, either. Architecture that allow
698                  * write without read access are not supported by HMM, because
699                  * operations such has atomic access would not work.
700                  */
701                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
702                 return -EPERM;
703         }
704
705         /* Initialize range to track CPU page table update */
706         spin_lock(&hmm->lock);
707         range->valid = true;
708         list_add_rcu(&range->list, &hmm->ranges);
709         spin_unlock(&hmm->lock);
710
711         hmm_vma_walk.fault = false;
712         hmm_vma_walk.range = range;
713         mm_walk.private = &hmm_vma_walk;
714
715         mm_walk.vma = vma;
716         mm_walk.mm = vma->vm_mm;
717         mm_walk.pte_entry = NULL;
718         mm_walk.test_walk = NULL;
719         mm_walk.hugetlb_entry = NULL;
720         mm_walk.pmd_entry = hmm_vma_walk_pmd;
721         mm_walk.pte_hole = hmm_vma_walk_hole;
722
723         walk_page_range(range->start, range->end, &mm_walk);
724         return 0;
725 }
726 EXPORT_SYMBOL(hmm_vma_get_pfns);
727
728 /*
729  * hmm_vma_range_done() - stop tracking change to CPU page table over a range
730  * @range: range being tracked
731  * Returns: false if range data has been invalidated, true otherwise
732  *
733  * Range struct is used to track updates to the CPU page table after a call to
734  * either hmm_vma_get_pfns() or hmm_vma_fault(). Once the device driver is done
735  * using the data,  or wants to lock updates to the data it got from those
736  * functions, it must call the hmm_vma_range_done() function, which will then
737  * stop tracking CPU page table updates.
738  *
739  * Note that device driver must still implement general CPU page table update
740  * tracking either by using hmm_mirror (see hmm_mirror_register()) or by using
741  * the mmu_notifier API directly.
742  *
743  * CPU page table update tracking done through hmm_range is only temporary and
744  * to be used while trying to duplicate CPU page table contents for a range of
745  * virtual addresses.
746  *
747  * There are two ways to use this :
748  * again:
749  *   hmm_vma_get_pfns(range); or hmm_vma_fault(...);
750  *   trans = device_build_page_table_update_transaction(pfns);
751  *   device_page_table_lock();
752  *   if (!hmm_vma_range_done(range)) {
753  *     device_page_table_unlock();
754  *     goto again;
755  *   }
756  *   device_commit_transaction(trans);
757  *   device_page_table_unlock();
758  *
759  * Or:
760  *   hmm_vma_get_pfns(range); or hmm_vma_fault(...);
761  *   device_page_table_lock();
762  *   hmm_vma_range_done(range);
763  *   device_update_page_table(range->pfns);
764  *   device_page_table_unlock();
765  */
766 bool hmm_vma_range_done(struct hmm_range *range)
767 {
768         unsigned long npages = (range->end - range->start) >> PAGE_SHIFT;
769         struct hmm *hmm;
770
771         if (range->end <= range->start) {
772                 BUG();
773                 return false;
774         }
775
776         hmm = hmm_register(range->vma->vm_mm);
777         if (!hmm) {
778                 memset(range->pfns, 0, sizeof(*range->pfns) * npages);
779                 return false;
780         }
781
782         spin_lock(&hmm->lock);
783         list_del_rcu(&range->list);
784         spin_unlock(&hmm->lock);
785
786         return range->valid;
787 }
788 EXPORT_SYMBOL(hmm_vma_range_done);
789
790 /*
791  * hmm_vma_fault() - try to fault some address in a virtual address range
792  * @range: range being faulted
793  * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
794  * Returns: 0 success, error otherwise (-EAGAIN means mmap_sem have been drop)
795  *
796  * This is similar to a regular CPU page fault except that it will not trigger
797  * any memory migration if the memory being faulted is not accessible by CPUs.
798  *
799  * On error, for one virtual address in the range, the function will mark the
800  * corresponding HMM pfn entry with an error flag.
801  *
802  * Expected use pattern:
803  * retry:
804  *   down_read(&mm->mmap_sem);
805  *   // Find vma and address device wants to fault, initialize hmm_pfn_t
806  *   // array accordingly
807  *   ret = hmm_vma_fault(range, write, block);
808  *   switch (ret) {
809  *   case -EAGAIN:
810  *     hmm_vma_range_done(range);
811  *     // You might want to rate limit or yield to play nicely, you may
812  *     // also commit any valid pfn in the array assuming that you are
813  *     // getting true from hmm_vma_range_monitor_end()
814  *     goto retry;
815  *   case 0:
816  *     break;
817  *   case -ENOMEM:
818  *   case -EINVAL:
819  *   case -EPERM:
820  *   default:
821  *     // Handle error !
822  *     up_read(&mm->mmap_sem)
823  *     return;
824  *   }
825  *   // Take device driver lock that serialize device page table update
826  *   driver_lock_device_page_table_update();
827  *   hmm_vma_range_done(range);
828  *   // Commit pfns we got from hmm_vma_fault()
829  *   driver_unlock_device_page_table_update();
830  *   up_read(&mm->mmap_sem)
831  *
832  * YOU MUST CALL hmm_vma_range_done() AFTER THIS FUNCTION RETURN SUCCESS (0)
833  * BEFORE FREEING THE range struct OR YOU WILL HAVE SERIOUS MEMORY CORRUPTION !
834  *
835  * YOU HAVE BEEN WARNED !
836  */
837 int hmm_vma_fault(struct hmm_range *range, bool block)
838 {
839         struct vm_area_struct *vma = range->vma;
840         unsigned long start = range->start;
841         struct hmm_vma_walk hmm_vma_walk;
842         struct mm_walk mm_walk;
843         struct hmm *hmm;
844         int ret;
845
846         /* Sanity check, this really should not happen ! */
847         if (range->start < vma->vm_start || range->start >= vma->vm_end)
848                 return -EINVAL;
849         if (range->end < vma->vm_start || range->end > vma->vm_end)
850                 return -EINVAL;
851
852         hmm = hmm_register(vma->vm_mm);
853         if (!hmm) {
854                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
855                 return -ENOMEM;
856         }
857         /* Caller must have registered a mirror using hmm_mirror_register() */
858         if (!hmm->mmu_notifier.ops)
859                 return -EINVAL;
860
861         /* FIXME support hugetlb fs */
862         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
863                         vma_is_dax(vma)) {
864                 hmm_pfns_special(range);
865                 return -EINVAL;
866         }
867
868         if (!(vma->vm_flags & VM_READ)) {
869                 /*
870                  * If vma do not allow read access, then assume that it does
871                  * not allow write access, either. Architecture that allow
872                  * write without read access are not supported by HMM, because
873                  * operations such has atomic access would not work.
874                  */
875                 hmm_pfns_clear(range, range->pfns, range->start, range->end);
876                 return -EPERM;
877         }
878
879         /* Initialize range to track CPU page table update */
880         spin_lock(&hmm->lock);
881         range->valid = true;
882         list_add_rcu(&range->list, &hmm->ranges);
883         spin_unlock(&hmm->lock);
884
885         hmm_vma_walk.fault = true;
886         hmm_vma_walk.block = block;
887         hmm_vma_walk.range = range;
888         mm_walk.private = &hmm_vma_walk;
889         hmm_vma_walk.last = range->start;
890
891         mm_walk.vma = vma;
892         mm_walk.mm = vma->vm_mm;
893         mm_walk.pte_entry = NULL;
894         mm_walk.test_walk = NULL;
895         mm_walk.hugetlb_entry = NULL;
896         mm_walk.pmd_entry = hmm_vma_walk_pmd;
897         mm_walk.pte_hole = hmm_vma_walk_hole;
898
899         do {
900                 ret = walk_page_range(start, range->end, &mm_walk);
901                 start = hmm_vma_walk.last;
902         } while (ret == -EAGAIN);
903
904         if (ret) {
905                 unsigned long i;
906
907                 i = (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
908                 hmm_pfns_clear(range, &range->pfns[i], hmm_vma_walk.last,
909                                range->end);
910                 hmm_vma_range_done(range);
911         }
912         return ret;
913 }
914 EXPORT_SYMBOL(hmm_vma_fault);
915 #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
916
917
918 #if IS_ENABLED(CONFIG_DEVICE_PRIVATE) ||  IS_ENABLED(CONFIG_DEVICE_PUBLIC)
919 struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
920                                        unsigned long addr)
921 {
922         struct page *page;
923
924         page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
925         if (!page)
926                 return NULL;
927         lock_page(page);
928         return page;
929 }
930 EXPORT_SYMBOL(hmm_vma_alloc_locked_page);
931
932
933 static void hmm_devmem_ref_release(struct percpu_ref *ref)
934 {
935         struct hmm_devmem *devmem;
936
937         devmem = container_of(ref, struct hmm_devmem, ref);
938         complete(&devmem->completion);
939 }
940
941 static void hmm_devmem_ref_exit(void *data)
942 {
943         struct percpu_ref *ref = data;
944         struct hmm_devmem *devmem;
945
946         devmem = container_of(ref, struct hmm_devmem, ref);
947         percpu_ref_exit(ref);
948 }
949
950 static void hmm_devmem_ref_kill(void *data)
951 {
952         struct percpu_ref *ref = data;
953         struct hmm_devmem *devmem;
954
955         devmem = container_of(ref, struct hmm_devmem, ref);
956         percpu_ref_kill(ref);
957         wait_for_completion(&devmem->completion);
958 }
959
960 static int hmm_devmem_fault(struct vm_area_struct *vma,
961                             unsigned long addr,
962                             const struct page *page,
963                             unsigned int flags,
964                             pmd_t *pmdp)
965 {
966         struct hmm_devmem *devmem = page->pgmap->data;
967
968         return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
969 }
970
971 static void hmm_devmem_free(struct page *page, void *data)
972 {
973         struct hmm_devmem *devmem = data;
974
975         page->mapping = NULL;
976
977         devmem->ops->free(devmem, page);
978 }
979
980 static DEFINE_MUTEX(hmm_devmem_lock);
981 static RADIX_TREE(hmm_devmem_radix, GFP_KERNEL);
982
983 static void hmm_devmem_radix_release(struct resource *resource)
984 {
985         resource_size_t key;
986
987         mutex_lock(&hmm_devmem_lock);
988         for (key = resource->start;
989              key <= resource->end;
990              key += PA_SECTION_SIZE)
991                 radix_tree_delete(&hmm_devmem_radix, key >> PA_SECTION_SHIFT);
992         mutex_unlock(&hmm_devmem_lock);
993 }
994
995 static void hmm_devmem_release(void *data)
996 {
997         struct hmm_devmem *devmem = data;
998         struct resource *resource = devmem->resource;
999         unsigned long start_pfn, npages;
1000         struct page *page;
1001         int nid;
1002
1003         /* pages are dead and unused, undo the arch mapping */
1004         start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT;
1005         npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT;
1006
1007         page = pfn_to_page(start_pfn);
1008         nid = page_to_nid(page);
1009
1010         mem_hotplug_begin();
1011         if (resource->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY)
1012                 __remove_pages(start_pfn, npages, NULL);
1013         else
1014                 arch_remove_memory(nid, start_pfn << PAGE_SHIFT,
1015                                    npages << PAGE_SHIFT, NULL);
1016         mem_hotplug_done();
1017
1018         hmm_devmem_radix_release(resource);
1019 }
1020
1021 static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
1022 {
1023         resource_size_t key, align_start, align_size, align_end;
1024         struct device *device = devmem->device;
1025         int ret, nid, is_ram;
1026         unsigned long pfn;
1027
1028         align_start = devmem->resource->start & ~(PA_SECTION_SIZE - 1);
1029         align_size = ALIGN(devmem->resource->start +
1030                            resource_size(devmem->resource),
1031                            PA_SECTION_SIZE) - align_start;
1032
1033         is_ram = region_intersects(align_start, align_size,
1034                                    IORESOURCE_SYSTEM_RAM,
1035                                    IORES_DESC_NONE);
1036         if (is_ram == REGION_MIXED) {
1037                 WARN_ONCE(1, "%s attempted on mixed region %pr\n",
1038                                 __func__, devmem->resource);
1039                 return -ENXIO;
1040         }
1041         if (is_ram == REGION_INTERSECTS)
1042                 return -ENXIO;
1043
1044         if (devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY)
1045                 devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
1046         else
1047                 devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
1048
1049         devmem->pagemap.res = *devmem->resource;
1050         devmem->pagemap.page_fault = hmm_devmem_fault;
1051         devmem->pagemap.page_free = hmm_devmem_free;
1052         devmem->pagemap.dev = devmem->device;
1053         devmem->pagemap.ref = &devmem->ref;
1054         devmem->pagemap.data = devmem;
1055
1056         mutex_lock(&hmm_devmem_lock);
1057         align_end = align_start + align_size - 1;
1058         for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) {
1059                 struct hmm_devmem *dup;
1060
1061                 dup = radix_tree_lookup(&hmm_devmem_radix,
1062                                         key >> PA_SECTION_SHIFT);
1063                 if (dup) {
1064                         dev_err(device, "%s: collides with mapping for %s\n",
1065                                 __func__, dev_name(dup->device));
1066                         mutex_unlock(&hmm_devmem_lock);
1067                         ret = -EBUSY;
1068                         goto error;
1069                 }
1070                 ret = radix_tree_insert(&hmm_devmem_radix,
1071                                         key >> PA_SECTION_SHIFT,
1072                                         devmem);
1073                 if (ret) {
1074                         dev_err(device, "%s: failed: %d\n", __func__, ret);
1075                         mutex_unlock(&hmm_devmem_lock);
1076                         goto error_radix;
1077                 }
1078         }
1079         mutex_unlock(&hmm_devmem_lock);
1080
1081         nid = dev_to_node(device);
1082         if (nid < 0)
1083                 nid = numa_mem_id();
1084
1085         mem_hotplug_begin();
1086         /*
1087          * For device private memory we call add_pages() as we only need to
1088          * allocate and initialize struct page for the device memory. More-
1089          * over the device memory is un-accessible thus we do not want to
1090          * create a linear mapping for the memory like arch_add_memory()
1091          * would do.
1092          *
1093          * For device public memory, which is accesible by the CPU, we do
1094          * want the linear mapping and thus use arch_add_memory().
1095          */
1096         if (devmem->pagemap.type == MEMORY_DEVICE_PUBLIC)
1097                 ret = arch_add_memory(nid, align_start, align_size, NULL,
1098                                 false);
1099         else
1100                 ret = add_pages(nid, align_start >> PAGE_SHIFT,
1101                                 align_size >> PAGE_SHIFT, NULL, false);
1102         if (ret) {
1103                 mem_hotplug_done();
1104                 goto error_add_memory;
1105         }
1106         move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
1107                                 align_start >> PAGE_SHIFT,
1108                                 align_size >> PAGE_SHIFT, NULL);
1109         mem_hotplug_done();
1110
1111         for (pfn = devmem->pfn_first; pfn < devmem->pfn_last; pfn++) {
1112                 struct page *page = pfn_to_page(pfn);
1113
1114                 page->pgmap = &devmem->pagemap;
1115         }
1116         return 0;
1117
1118 error_add_memory:
1119         untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
1120 error_radix:
1121         hmm_devmem_radix_release(devmem->resource);
1122 error:
1123         return ret;
1124 }
1125
1126 /*
1127  * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
1128  *
1129  * @ops: memory event device driver callback (see struct hmm_devmem_ops)
1130  * @device: device struct to bind the resource too
1131  * @size: size in bytes of the device memory to add
1132  * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise
1133  *
1134  * This function first finds an empty range of physical address big enough to
1135  * contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which
1136  * in turn allocates struct pages. It does not do anything beyond that; all
1137  * events affecting the memory will go through the various callbacks provided
1138  * by hmm_devmem_ops struct.
1139  *
1140  * Device driver should call this function during device initialization and
1141  * is then responsible of memory management. HMM only provides helpers.
1142  */
1143 struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
1144                                   struct device *device,
1145                                   unsigned long size)
1146 {
1147         struct hmm_devmem *devmem;
1148         resource_size_t addr;
1149         int ret;
1150
1151         dev_pagemap_get_ops();
1152
1153         devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
1154         if (!devmem)
1155                 return ERR_PTR(-ENOMEM);
1156
1157         init_completion(&devmem->completion);
1158         devmem->pfn_first = -1UL;
1159         devmem->pfn_last = -1UL;
1160         devmem->resource = NULL;
1161         devmem->device = device;
1162         devmem->ops = ops;
1163
1164         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1165                               0, GFP_KERNEL);
1166         if (ret)
1167                 return ERR_PTR(ret);
1168
1169         ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit, &devmem->ref);
1170         if (ret)
1171                 return ERR_PTR(ret);
1172
1173         size = ALIGN(size, PA_SECTION_SIZE);
1174         addr = min((unsigned long)iomem_resource.end,
1175                    (1UL << MAX_PHYSMEM_BITS) - 1);
1176         addr = addr - size + 1UL;
1177
1178         /*
1179          * FIXME add a new helper to quickly walk resource tree and find free
1180          * range
1181          *
1182          * FIXME what about ioport_resource resource ?
1183          */
1184         for (; addr > size && addr >= iomem_resource.start; addr -= size) {
1185                 ret = region_intersects(addr, size, 0, IORES_DESC_NONE);
1186                 if (ret != REGION_DISJOINT)
1187                         continue;
1188
1189                 devmem->resource = devm_request_mem_region(device, addr, size,
1190                                                            dev_name(device));
1191                 if (!devmem->resource)
1192                         return ERR_PTR(-ENOMEM);
1193                 break;
1194         }
1195         if (!devmem->resource)
1196                 return ERR_PTR(-ERANGE);
1197
1198         devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
1199         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1200         devmem->pfn_last = devmem->pfn_first +
1201                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1202
1203         ret = hmm_devmem_pages_create(devmem);
1204         if (ret)
1205                 return ERR_PTR(ret);
1206
1207         ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
1208         if (ret)
1209                 return ERR_PTR(ret);
1210
1211         return devmem;
1212 }
1213 EXPORT_SYMBOL_GPL(hmm_devmem_add);
1214
1215 struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
1216                                            struct device *device,
1217                                            struct resource *res)
1218 {
1219         struct hmm_devmem *devmem;
1220         int ret;
1221
1222         if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY)
1223                 return ERR_PTR(-EINVAL);
1224
1225         dev_pagemap_get_ops();
1226
1227         devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
1228         if (!devmem)
1229                 return ERR_PTR(-ENOMEM);
1230
1231         init_completion(&devmem->completion);
1232         devmem->pfn_first = -1UL;
1233         devmem->pfn_last = -1UL;
1234         devmem->resource = res;
1235         devmem->device = device;
1236         devmem->ops = ops;
1237
1238         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1239                               0, GFP_KERNEL);
1240         if (ret)
1241                 return ERR_PTR(ret);
1242
1243         ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit,
1244                         &devmem->ref);
1245         if (ret)
1246                 return ERR_PTR(ret);
1247
1248         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1249         devmem->pfn_last = devmem->pfn_first +
1250                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1251
1252         ret = hmm_devmem_pages_create(devmem);
1253         if (ret)
1254                 return ERR_PTR(ret);
1255
1256         ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
1257         if (ret)
1258                 return ERR_PTR(ret);
1259
1260         ret = devm_add_action_or_reset(device, hmm_devmem_ref_kill,
1261                         &devmem->ref);
1262         if (ret)
1263                 return ERR_PTR(ret);
1264
1265         return devmem;
1266 }
1267 EXPORT_SYMBOL_GPL(hmm_devmem_add_resource);
1268
1269 /*
1270  * A device driver that wants to handle multiple devices memory through a
1271  * single fake device can use hmm_device to do so. This is purely a helper
1272  * and it is not needed to make use of any HMM functionality.
1273  */
1274 #define HMM_DEVICE_MAX 256
1275
1276 static DECLARE_BITMAP(hmm_device_mask, HMM_DEVICE_MAX);
1277 static DEFINE_SPINLOCK(hmm_device_lock);
1278 static struct class *hmm_device_class;
1279 static dev_t hmm_device_devt;
1280
1281 static void hmm_device_release(struct device *device)
1282 {
1283         struct hmm_device *hmm_device;
1284
1285         hmm_device = container_of(device, struct hmm_device, device);
1286         spin_lock(&hmm_device_lock);
1287         clear_bit(hmm_device->minor, hmm_device_mask);
1288         spin_unlock(&hmm_device_lock);
1289
1290         kfree(hmm_device);
1291 }
1292
1293 struct hmm_device *hmm_device_new(void *drvdata)
1294 {
1295         struct hmm_device *hmm_device;
1296
1297         hmm_device = kzalloc(sizeof(*hmm_device), GFP_KERNEL);
1298         if (!hmm_device)
1299                 return ERR_PTR(-ENOMEM);
1300
1301         spin_lock(&hmm_device_lock);
1302         hmm_device->minor = find_first_zero_bit(hmm_device_mask, HMM_DEVICE_MAX);
1303         if (hmm_device->minor >= HMM_DEVICE_MAX) {
1304                 spin_unlock(&hmm_device_lock);
1305                 kfree(hmm_device);
1306                 return ERR_PTR(-EBUSY);
1307         }
1308         set_bit(hmm_device->minor, hmm_device_mask);
1309         spin_unlock(&hmm_device_lock);
1310
1311         dev_set_name(&hmm_device->device, "hmm_device%d", hmm_device->minor);
1312         hmm_device->device.devt = MKDEV(MAJOR(hmm_device_devt),
1313                                         hmm_device->minor);
1314         hmm_device->device.release = hmm_device_release;
1315         dev_set_drvdata(&hmm_device->device, drvdata);
1316         hmm_device->device.class = hmm_device_class;
1317         device_initialize(&hmm_device->device);
1318
1319         return hmm_device;
1320 }
1321 EXPORT_SYMBOL(hmm_device_new);
1322
1323 void hmm_device_put(struct hmm_device *hmm_device)
1324 {
1325         put_device(&hmm_device->device);
1326 }
1327 EXPORT_SYMBOL(hmm_device_put);
1328
1329 static int __init hmm_init(void)
1330 {
1331         int ret;
1332
1333         ret = alloc_chrdev_region(&hmm_device_devt, 0,
1334                                   HMM_DEVICE_MAX,
1335                                   "hmm_device");
1336         if (ret)
1337                 return ret;
1338
1339         hmm_device_class = class_create(THIS_MODULE, "hmm_device");
1340         if (IS_ERR(hmm_device_class)) {
1341                 unregister_chrdev_region(hmm_device_devt, HMM_DEVICE_MAX);
1342                 return PTR_ERR(hmm_device_class);
1343         }
1344         return 0;
1345 }
1346
1347 device_initcall(hmm_init);
1348 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */