Revert "mm: replace p??_write with pte_access_permitted in fault + gup paths"
[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 defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC)
39 /*
40  * Device private memory see HMM (Documentation/vm/hmm.txt) or hmm.h
41  */
42 DEFINE_STATIC_KEY_FALSE(device_private_key);
43 EXPORT_SYMBOL(device_private_key);
44 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
45
46
47 #if IS_ENABLED(CONFIG_HMM_MIRROR)
48 static const struct mmu_notifier_ops hmm_mmu_notifier_ops;
49
50 /*
51  * struct hmm - HMM per mm struct
52  *
53  * @mm: mm struct this HMM struct is bound to
54  * @lock: lock protecting ranges list
55  * @sequence: we track updates to the CPU page table with a sequence number
56  * @ranges: list of range being snapshotted
57  * @mirrors: list of mirrors for this mm
58  * @mmu_notifier: mmu notifier to track updates to CPU page table
59  * @mirrors_sem: read/write semaphore protecting the mirrors list
60  */
61 struct hmm {
62         struct mm_struct        *mm;
63         spinlock_t              lock;
64         atomic_t                sequence;
65         struct list_head        ranges;
66         struct list_head        mirrors;
67         struct mmu_notifier     mmu_notifier;
68         struct rw_semaphore     mirrors_sem;
69 };
70
71 /*
72  * hmm_register - register HMM against an mm (HMM internal)
73  *
74  * @mm: mm struct to attach to
75  *
76  * This is not intended to be used directly by device drivers. It allocates an
77  * HMM struct if mm does not have one, and initializes it.
78  */
79 static struct hmm *hmm_register(struct mm_struct *mm)
80 {
81         struct hmm *hmm = READ_ONCE(mm->hmm);
82         bool cleanup = false;
83
84         /*
85          * The hmm struct can only be freed once the mm_struct goes away,
86          * hence we should always have pre-allocated an new hmm struct
87          * above.
88          */
89         if (hmm)
90                 return hmm;
91
92         hmm = kmalloc(sizeof(*hmm), GFP_KERNEL);
93         if (!hmm)
94                 return NULL;
95         INIT_LIST_HEAD(&hmm->mirrors);
96         init_rwsem(&hmm->mirrors_sem);
97         atomic_set(&hmm->sequence, 0);
98         hmm->mmu_notifier.ops = NULL;
99         INIT_LIST_HEAD(&hmm->ranges);
100         spin_lock_init(&hmm->lock);
101         hmm->mm = mm;
102
103         /*
104          * We should only get here if hold the mmap_sem in write mode ie on
105          * registration of first mirror through hmm_mirror_register()
106          */
107         hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops;
108         if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) {
109                 kfree(hmm);
110                 return NULL;
111         }
112
113         spin_lock(&mm->page_table_lock);
114         if (!mm->hmm)
115                 mm->hmm = hmm;
116         else
117                 cleanup = true;
118         spin_unlock(&mm->page_table_lock);
119
120         if (cleanup) {
121                 mmu_notifier_unregister(&hmm->mmu_notifier, mm);
122                 kfree(hmm);
123         }
124
125         return mm->hmm;
126 }
127
128 void hmm_mm_destroy(struct mm_struct *mm)
129 {
130         kfree(mm->hmm);
131 }
132
133 static void hmm_invalidate_range(struct hmm *hmm,
134                                  enum hmm_update_type action,
135                                  unsigned long start,
136                                  unsigned long end)
137 {
138         struct hmm_mirror *mirror;
139         struct hmm_range *range;
140
141         spin_lock(&hmm->lock);
142         list_for_each_entry(range, &hmm->ranges, list) {
143                 unsigned long addr, idx, npages;
144
145                 if (end < range->start || start >= range->end)
146                         continue;
147
148                 range->valid = false;
149                 addr = max(start, range->start);
150                 idx = (addr - range->start) >> PAGE_SHIFT;
151                 npages = (min(range->end, end) - addr) >> PAGE_SHIFT;
152                 memset(&range->pfns[idx], 0, sizeof(*range->pfns) * npages);
153         }
154         spin_unlock(&hmm->lock);
155
156         down_read(&hmm->mirrors_sem);
157         list_for_each_entry(mirror, &hmm->mirrors, list)
158                 mirror->ops->sync_cpu_device_pagetables(mirror, action,
159                                                         start, end);
160         up_read(&hmm->mirrors_sem);
161 }
162
163 static void hmm_invalidate_range_start(struct mmu_notifier *mn,
164                                        struct mm_struct *mm,
165                                        unsigned long start,
166                                        unsigned long end)
167 {
168         struct hmm *hmm = mm->hmm;
169
170         VM_BUG_ON(!hmm);
171
172         atomic_inc(&hmm->sequence);
173 }
174
175 static void hmm_invalidate_range_end(struct mmu_notifier *mn,
176                                      struct mm_struct *mm,
177                                      unsigned long start,
178                                      unsigned long end)
179 {
180         struct hmm *hmm = mm->hmm;
181
182         VM_BUG_ON(!hmm);
183
184         hmm_invalidate_range(mm->hmm, HMM_UPDATE_INVALIDATE, start, end);
185 }
186
187 static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
188         .invalidate_range_start = hmm_invalidate_range_start,
189         .invalidate_range_end   = hmm_invalidate_range_end,
190 };
191
192 /*
193  * hmm_mirror_register() - register a mirror against an mm
194  *
195  * @mirror: new mirror struct to register
196  * @mm: mm to register against
197  *
198  * To start mirroring a process address space, the device driver must register
199  * an HMM mirror struct.
200  *
201  * THE mm->mmap_sem MUST BE HELD IN WRITE MODE !
202  */
203 int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
204 {
205         /* Sanity check */
206         if (!mm || !mirror || !mirror->ops)
207                 return -EINVAL;
208
209         mirror->hmm = hmm_register(mm);
210         if (!mirror->hmm)
211                 return -ENOMEM;
212
213         down_write(&mirror->hmm->mirrors_sem);
214         list_add(&mirror->list, &mirror->hmm->mirrors);
215         up_write(&mirror->hmm->mirrors_sem);
216
217         return 0;
218 }
219 EXPORT_SYMBOL(hmm_mirror_register);
220
221 /*
222  * hmm_mirror_unregister() - unregister a mirror
223  *
224  * @mirror: new mirror struct to register
225  *
226  * Stop mirroring a process address space, and cleanup.
227  */
228 void hmm_mirror_unregister(struct hmm_mirror *mirror)
229 {
230         struct hmm *hmm = mirror->hmm;
231
232         down_write(&hmm->mirrors_sem);
233         list_del(&mirror->list);
234         up_write(&hmm->mirrors_sem);
235 }
236 EXPORT_SYMBOL(hmm_mirror_unregister);
237
238 struct hmm_vma_walk {
239         struct hmm_range        *range;
240         unsigned long           last;
241         bool                    fault;
242         bool                    block;
243         bool                    write;
244 };
245
246 static int hmm_vma_do_fault(struct mm_walk *walk,
247                             unsigned long addr,
248                             hmm_pfn_t *pfn)
249 {
250         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
251         struct hmm_vma_walk *hmm_vma_walk = walk->private;
252         struct vm_area_struct *vma = walk->vma;
253         int r;
254
255         flags |= hmm_vma_walk->block ? 0 : FAULT_FLAG_ALLOW_RETRY;
256         flags |= hmm_vma_walk->write ? FAULT_FLAG_WRITE : 0;
257         r = handle_mm_fault(vma, addr, flags);
258         if (r & VM_FAULT_RETRY)
259                 return -EBUSY;
260         if (r & VM_FAULT_ERROR) {
261                 *pfn = HMM_PFN_ERROR;
262                 return -EFAULT;
263         }
264
265         return -EAGAIN;
266 }
267
268 static void hmm_pfns_special(hmm_pfn_t *pfns,
269                              unsigned long addr,
270                              unsigned long end)
271 {
272         for (; addr < end; addr += PAGE_SIZE, pfns++)
273                 *pfns = HMM_PFN_SPECIAL;
274 }
275
276 static int hmm_pfns_bad(unsigned long addr,
277                         unsigned long end,
278                         struct mm_walk *walk)
279 {
280         struct hmm_range *range = walk->private;
281         hmm_pfn_t *pfns = range->pfns;
282         unsigned long i;
283
284         i = (addr - range->start) >> PAGE_SHIFT;
285         for (; addr < end; addr += PAGE_SIZE, i++)
286                 pfns[i] = HMM_PFN_ERROR;
287
288         return 0;
289 }
290
291 static void hmm_pfns_clear(hmm_pfn_t *pfns,
292                            unsigned long addr,
293                            unsigned long end)
294 {
295         for (; addr < end; addr += PAGE_SIZE, pfns++)
296                 *pfns = 0;
297 }
298
299 static int hmm_vma_walk_hole(unsigned long addr,
300                              unsigned long end,
301                              struct mm_walk *walk)
302 {
303         struct hmm_vma_walk *hmm_vma_walk = walk->private;
304         struct hmm_range *range = hmm_vma_walk->range;
305         hmm_pfn_t *pfns = range->pfns;
306         unsigned long i;
307
308         hmm_vma_walk->last = addr;
309         i = (addr - range->start) >> PAGE_SHIFT;
310         for (; addr < end; addr += PAGE_SIZE, i++) {
311                 pfns[i] = HMM_PFN_EMPTY;
312                 if (hmm_vma_walk->fault) {
313                         int ret;
314
315                         ret = hmm_vma_do_fault(walk, addr, &pfns[i]);
316                         if (ret != -EAGAIN)
317                                 return ret;
318                 }
319         }
320
321         return hmm_vma_walk->fault ? -EAGAIN : 0;
322 }
323
324 static int hmm_vma_walk_clear(unsigned long addr,
325                               unsigned long end,
326                               struct mm_walk *walk)
327 {
328         struct hmm_vma_walk *hmm_vma_walk = walk->private;
329         struct hmm_range *range = hmm_vma_walk->range;
330         hmm_pfn_t *pfns = range->pfns;
331         unsigned long i;
332
333         hmm_vma_walk->last = addr;
334         i = (addr - range->start) >> PAGE_SHIFT;
335         for (; addr < end; addr += PAGE_SIZE, i++) {
336                 pfns[i] = 0;
337                 if (hmm_vma_walk->fault) {
338                         int ret;
339
340                         ret = hmm_vma_do_fault(walk, addr, &pfns[i]);
341                         if (ret != -EAGAIN)
342                                 return ret;
343                 }
344         }
345
346         return hmm_vma_walk->fault ? -EAGAIN : 0;
347 }
348
349 static int hmm_vma_walk_pmd(pmd_t *pmdp,
350                             unsigned long start,
351                             unsigned long end,
352                             struct mm_walk *walk)
353 {
354         struct hmm_vma_walk *hmm_vma_walk = walk->private;
355         struct hmm_range *range = hmm_vma_walk->range;
356         struct vm_area_struct *vma = walk->vma;
357         hmm_pfn_t *pfns = range->pfns;
358         unsigned long addr = start, i;
359         bool write_fault;
360         hmm_pfn_t flag;
361         pte_t *ptep;
362
363         i = (addr - range->start) >> PAGE_SHIFT;
364         flag = vma->vm_flags & VM_READ ? HMM_PFN_READ : 0;
365         write_fault = hmm_vma_walk->fault & hmm_vma_walk->write;
366
367 again:
368         if (pmd_none(*pmdp))
369                 return hmm_vma_walk_hole(start, end, walk);
370
371         if (pmd_huge(*pmdp) && vma->vm_flags & VM_HUGETLB)
372                 return hmm_pfns_bad(start, end, walk);
373
374         if (pmd_devmap(*pmdp) || pmd_trans_huge(*pmdp)) {
375                 unsigned long pfn;
376                 pmd_t pmd;
377
378                 /*
379                  * No need to take pmd_lock here, even if some other threads
380                  * is splitting the huge pmd we will get that event through
381                  * mmu_notifier callback.
382                  *
383                  * So just read pmd value and check again its a transparent
384                  * huge or device mapping one and compute corresponding pfn
385                  * values.
386                  */
387                 pmd = pmd_read_atomic(pmdp);
388                 barrier();
389                 if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
390                         goto again;
391                 if (pmd_protnone(pmd))
392                         return hmm_vma_walk_clear(start, end, walk);
393
394                 if (write_fault && !pmd_write(pmd))
395                         return hmm_vma_walk_clear(start, end, walk);
396
397                 pfn = pmd_pfn(pmd) + pte_index(addr);
398                 flag |= pmd_write(pmd) ? HMM_PFN_WRITE : 0;
399                 for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
400                         pfns[i] = hmm_pfn_t_from_pfn(pfn) | flag;
401                 return 0;
402         }
403
404         if (pmd_bad(*pmdp))
405                 return hmm_pfns_bad(start, end, walk);
406
407         ptep = pte_offset_map(pmdp, addr);
408         for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
409                 pte_t pte = *ptep;
410
411                 pfns[i] = 0;
412
413                 if (pte_none(pte)) {
414                         pfns[i] = HMM_PFN_EMPTY;
415                         if (hmm_vma_walk->fault)
416                                 goto fault;
417                         continue;
418                 }
419
420                 if (!pte_present(pte)) {
421                         swp_entry_t entry;
422
423                         if (!non_swap_entry(entry)) {
424                                 if (hmm_vma_walk->fault)
425                                         goto fault;
426                                 continue;
427                         }
428
429                         entry = pte_to_swp_entry(pte);
430
431                         /*
432                          * This is a special swap entry, ignore migration, use
433                          * device and report anything else as error.
434                          */
435                         if (is_device_private_entry(entry)) {
436                                 pfns[i] = hmm_pfn_t_from_pfn(swp_offset(entry));
437                                 if (is_write_device_private_entry(entry)) {
438                                         pfns[i] |= HMM_PFN_WRITE;
439                                 } else if (write_fault)
440                                         goto fault;
441                                 pfns[i] |= HMM_PFN_DEVICE_UNADDRESSABLE;
442                                 pfns[i] |= flag;
443                         } else if (is_migration_entry(entry)) {
444                                 if (hmm_vma_walk->fault) {
445                                         pte_unmap(ptep);
446                                         hmm_vma_walk->last = addr;
447                                         migration_entry_wait(vma->vm_mm,
448                                                              pmdp, addr);
449                                         return -EAGAIN;
450                                 }
451                                 continue;
452                         } else {
453                                 /* Report error for everything else */
454                                 pfns[i] = HMM_PFN_ERROR;
455                         }
456                         continue;
457                 }
458
459                 if (write_fault && !pte_write(pte))
460                         goto fault;
461
462                 pfns[i] = hmm_pfn_t_from_pfn(pte_pfn(pte)) | flag;
463                 pfns[i] |= pte_write(pte) ? HMM_PFN_WRITE : 0;
464                 continue;
465
466 fault:
467                 pte_unmap(ptep);
468                 /* Fault all pages in range */
469                 return hmm_vma_walk_clear(start, end, walk);
470         }
471         pte_unmap(ptep - 1);
472
473         return 0;
474 }
475
476 /*
477  * hmm_vma_get_pfns() - snapshot CPU page table for a range of virtual addresses
478  * @vma: virtual memory area containing the virtual address range
479  * @range: used to track snapshot validity
480  * @start: range virtual start address (inclusive)
481  * @end: range virtual end address (exclusive)
482  * @entries: array of hmm_pfn_t: provided by the caller, filled in by function
483  * Returns: -EINVAL if invalid argument, -ENOMEM out of memory, 0 success
484  *
485  * This snapshots the CPU page table for a range of virtual addresses. Snapshot
486  * validity is tracked by range struct. See hmm_vma_range_done() for further
487  * information.
488  *
489  * The range struct is initialized here. It tracks the CPU page table, but only
490  * if the function returns success (0), in which case the caller must then call
491  * hmm_vma_range_done() to stop CPU page table update tracking on this range.
492  *
493  * NOT CALLING hmm_vma_range_done() IF FUNCTION RETURNS 0 WILL LEAD TO SERIOUS
494  * MEMORY CORRUPTION ! YOU HAVE BEEN WARNED !
495  */
496 int hmm_vma_get_pfns(struct vm_area_struct *vma,
497                      struct hmm_range *range,
498                      unsigned long start,
499                      unsigned long end,
500                      hmm_pfn_t *pfns)
501 {
502         struct hmm_vma_walk hmm_vma_walk;
503         struct mm_walk mm_walk;
504         struct hmm *hmm;
505
506         /* FIXME support hugetlb fs */
507         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
508                 hmm_pfns_special(pfns, start, end);
509                 return -EINVAL;
510         }
511
512         /* Sanity check, this really should not happen ! */
513         if (start < vma->vm_start || start >= vma->vm_end)
514                 return -EINVAL;
515         if (end < vma->vm_start || end > vma->vm_end)
516                 return -EINVAL;
517
518         hmm = hmm_register(vma->vm_mm);
519         if (!hmm)
520                 return -ENOMEM;
521         /* Caller must have registered a mirror, via hmm_mirror_register() ! */
522         if (!hmm->mmu_notifier.ops)
523                 return -EINVAL;
524
525         /* Initialize range to track CPU page table update */
526         range->start = start;
527         range->pfns = pfns;
528         range->end = end;
529         spin_lock(&hmm->lock);
530         range->valid = true;
531         list_add_rcu(&range->list, &hmm->ranges);
532         spin_unlock(&hmm->lock);
533
534         hmm_vma_walk.fault = false;
535         hmm_vma_walk.range = range;
536         mm_walk.private = &hmm_vma_walk;
537
538         mm_walk.vma = vma;
539         mm_walk.mm = vma->vm_mm;
540         mm_walk.pte_entry = NULL;
541         mm_walk.test_walk = NULL;
542         mm_walk.hugetlb_entry = NULL;
543         mm_walk.pmd_entry = hmm_vma_walk_pmd;
544         mm_walk.pte_hole = hmm_vma_walk_hole;
545
546         walk_page_range(start, end, &mm_walk);
547         return 0;
548 }
549 EXPORT_SYMBOL(hmm_vma_get_pfns);
550
551 /*
552  * hmm_vma_range_done() - stop tracking change to CPU page table over a range
553  * @vma: virtual memory area containing the virtual address range
554  * @range: range being tracked
555  * Returns: false if range data has been invalidated, true otherwise
556  *
557  * Range struct is used to track updates to the CPU page table after a call to
558  * either hmm_vma_get_pfns() or hmm_vma_fault(). Once the device driver is done
559  * using the data,  or wants to lock updates to the data it got from those
560  * functions, it must call the hmm_vma_range_done() function, which will then
561  * stop tracking CPU page table updates.
562  *
563  * Note that device driver must still implement general CPU page table update
564  * tracking either by using hmm_mirror (see hmm_mirror_register()) or by using
565  * the mmu_notifier API directly.
566  *
567  * CPU page table update tracking done through hmm_range is only temporary and
568  * to be used while trying to duplicate CPU page table contents for a range of
569  * virtual addresses.
570  *
571  * There are two ways to use this :
572  * again:
573  *   hmm_vma_get_pfns(vma, range, start, end, pfns); or hmm_vma_fault(...);
574  *   trans = device_build_page_table_update_transaction(pfns);
575  *   device_page_table_lock();
576  *   if (!hmm_vma_range_done(vma, range)) {
577  *     device_page_table_unlock();
578  *     goto again;
579  *   }
580  *   device_commit_transaction(trans);
581  *   device_page_table_unlock();
582  *
583  * Or:
584  *   hmm_vma_get_pfns(vma, range, start, end, pfns); or hmm_vma_fault(...);
585  *   device_page_table_lock();
586  *   hmm_vma_range_done(vma, range);
587  *   device_update_page_table(pfns);
588  *   device_page_table_unlock();
589  */
590 bool hmm_vma_range_done(struct vm_area_struct *vma, struct hmm_range *range)
591 {
592         unsigned long npages = (range->end - range->start) >> PAGE_SHIFT;
593         struct hmm *hmm;
594
595         if (range->end <= range->start) {
596                 BUG();
597                 return false;
598         }
599
600         hmm = hmm_register(vma->vm_mm);
601         if (!hmm) {
602                 memset(range->pfns, 0, sizeof(*range->pfns) * npages);
603                 return false;
604         }
605
606         spin_lock(&hmm->lock);
607         list_del_rcu(&range->list);
608         spin_unlock(&hmm->lock);
609
610         return range->valid;
611 }
612 EXPORT_SYMBOL(hmm_vma_range_done);
613
614 /*
615  * hmm_vma_fault() - try to fault some address in a virtual address range
616  * @vma: virtual memory area containing the virtual address range
617  * @range: use to track pfns array content validity
618  * @start: fault range virtual start address (inclusive)
619  * @end: fault range virtual end address (exclusive)
620  * @pfns: array of hmm_pfn_t, only entry with fault flag set will be faulted
621  * @write: is it a write fault
622  * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
623  * Returns: 0 success, error otherwise (-EAGAIN means mmap_sem have been drop)
624  *
625  * This is similar to a regular CPU page fault except that it will not trigger
626  * any memory migration if the memory being faulted is not accessible by CPUs.
627  *
628  * On error, for one virtual address in the range, the function will set the
629  * hmm_pfn_t error flag for the corresponding pfn entry.
630  *
631  * Expected use pattern:
632  * retry:
633  *   down_read(&mm->mmap_sem);
634  *   // Find vma and address device wants to fault, initialize hmm_pfn_t
635  *   // array accordingly
636  *   ret = hmm_vma_fault(vma, start, end, pfns, allow_retry);
637  *   switch (ret) {
638  *   case -EAGAIN:
639  *     hmm_vma_range_done(vma, range);
640  *     // You might want to rate limit or yield to play nicely, you may
641  *     // also commit any valid pfn in the array assuming that you are
642  *     // getting true from hmm_vma_range_monitor_end()
643  *     goto retry;
644  *   case 0:
645  *     break;
646  *   default:
647  *     // Handle error !
648  *     up_read(&mm->mmap_sem)
649  *     return;
650  *   }
651  *   // Take device driver lock that serialize device page table update
652  *   driver_lock_device_page_table_update();
653  *   hmm_vma_range_done(vma, range);
654  *   // Commit pfns we got from hmm_vma_fault()
655  *   driver_unlock_device_page_table_update();
656  *   up_read(&mm->mmap_sem)
657  *
658  * YOU MUST CALL hmm_vma_range_done() AFTER THIS FUNCTION RETURN SUCCESS (0)
659  * BEFORE FREEING THE range struct OR YOU WILL HAVE SERIOUS MEMORY CORRUPTION !
660  *
661  * YOU HAVE BEEN WARNED !
662  */
663 int hmm_vma_fault(struct vm_area_struct *vma,
664                   struct hmm_range *range,
665                   unsigned long start,
666                   unsigned long end,
667                   hmm_pfn_t *pfns,
668                   bool write,
669                   bool block)
670 {
671         struct hmm_vma_walk hmm_vma_walk;
672         struct mm_walk mm_walk;
673         struct hmm *hmm;
674         int ret;
675
676         /* Sanity check, this really should not happen ! */
677         if (start < vma->vm_start || start >= vma->vm_end)
678                 return -EINVAL;
679         if (end < vma->vm_start || end > vma->vm_end)
680                 return -EINVAL;
681
682         hmm = hmm_register(vma->vm_mm);
683         if (!hmm) {
684                 hmm_pfns_clear(pfns, start, end);
685                 return -ENOMEM;
686         }
687         /* Caller must have registered a mirror using hmm_mirror_register() */
688         if (!hmm->mmu_notifier.ops)
689                 return -EINVAL;
690
691         /* Initialize range to track CPU page table update */
692         range->start = start;
693         range->pfns = pfns;
694         range->end = end;
695         spin_lock(&hmm->lock);
696         range->valid = true;
697         list_add_rcu(&range->list, &hmm->ranges);
698         spin_unlock(&hmm->lock);
699
700         /* FIXME support hugetlb fs */
701         if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
702                 hmm_pfns_special(pfns, start, end);
703                 return 0;
704         }
705
706         hmm_vma_walk.fault = true;
707         hmm_vma_walk.write = write;
708         hmm_vma_walk.block = block;
709         hmm_vma_walk.range = range;
710         mm_walk.private = &hmm_vma_walk;
711         hmm_vma_walk.last = range->start;
712
713         mm_walk.vma = vma;
714         mm_walk.mm = vma->vm_mm;
715         mm_walk.pte_entry = NULL;
716         mm_walk.test_walk = NULL;
717         mm_walk.hugetlb_entry = NULL;
718         mm_walk.pmd_entry = hmm_vma_walk_pmd;
719         mm_walk.pte_hole = hmm_vma_walk_hole;
720
721         do {
722                 ret = walk_page_range(start, end, &mm_walk);
723                 start = hmm_vma_walk.last;
724         } while (ret == -EAGAIN);
725
726         if (ret) {
727                 unsigned long i;
728
729                 i = (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
730                 hmm_pfns_clear(&pfns[i], hmm_vma_walk.last, end);
731                 hmm_vma_range_done(vma, range);
732         }
733         return ret;
734 }
735 EXPORT_SYMBOL(hmm_vma_fault);
736 #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
737
738
739 #if IS_ENABLED(CONFIG_DEVICE_PRIVATE) ||  IS_ENABLED(CONFIG_DEVICE_PUBLIC)
740 struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
741                                        unsigned long addr)
742 {
743         struct page *page;
744
745         page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
746         if (!page)
747                 return NULL;
748         lock_page(page);
749         return page;
750 }
751 EXPORT_SYMBOL(hmm_vma_alloc_locked_page);
752
753
754 static void hmm_devmem_ref_release(struct percpu_ref *ref)
755 {
756         struct hmm_devmem *devmem;
757
758         devmem = container_of(ref, struct hmm_devmem, ref);
759         complete(&devmem->completion);
760 }
761
762 static void hmm_devmem_ref_exit(void *data)
763 {
764         struct percpu_ref *ref = data;
765         struct hmm_devmem *devmem;
766
767         devmem = container_of(ref, struct hmm_devmem, ref);
768         percpu_ref_exit(ref);
769         devm_remove_action(devmem->device, &hmm_devmem_ref_exit, data);
770 }
771
772 static void hmm_devmem_ref_kill(void *data)
773 {
774         struct percpu_ref *ref = data;
775         struct hmm_devmem *devmem;
776
777         devmem = container_of(ref, struct hmm_devmem, ref);
778         percpu_ref_kill(ref);
779         wait_for_completion(&devmem->completion);
780         devm_remove_action(devmem->device, &hmm_devmem_ref_kill, data);
781 }
782
783 static int hmm_devmem_fault(struct vm_area_struct *vma,
784                             unsigned long addr,
785                             const struct page *page,
786                             unsigned int flags,
787                             pmd_t *pmdp)
788 {
789         struct hmm_devmem *devmem = page->pgmap->data;
790
791         return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
792 }
793
794 static void hmm_devmem_free(struct page *page, void *data)
795 {
796         struct hmm_devmem *devmem = data;
797
798         devmem->ops->free(devmem, page);
799 }
800
801 static DEFINE_MUTEX(hmm_devmem_lock);
802 static RADIX_TREE(hmm_devmem_radix, GFP_KERNEL);
803
804 static void hmm_devmem_radix_release(struct resource *resource)
805 {
806         resource_size_t key, align_start, align_size;
807
808         align_start = resource->start & ~(PA_SECTION_SIZE - 1);
809         align_size = ALIGN(resource_size(resource), PA_SECTION_SIZE);
810
811         mutex_lock(&hmm_devmem_lock);
812         for (key = resource->start;
813              key <= resource->end;
814              key += PA_SECTION_SIZE)
815                 radix_tree_delete(&hmm_devmem_radix, key >> PA_SECTION_SHIFT);
816         mutex_unlock(&hmm_devmem_lock);
817 }
818
819 static void hmm_devmem_release(struct device *dev, void *data)
820 {
821         struct hmm_devmem *devmem = data;
822         struct resource *resource = devmem->resource;
823         unsigned long start_pfn, npages;
824         struct zone *zone;
825         struct page *page;
826
827         if (percpu_ref_tryget_live(&devmem->ref)) {
828                 dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
829                 percpu_ref_put(&devmem->ref);
830         }
831
832         /* pages are dead and unused, undo the arch mapping */
833         start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT;
834         npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT;
835
836         page = pfn_to_page(start_pfn);
837         zone = page_zone(page);
838
839         mem_hotplug_begin();
840         if (resource->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY)
841                 __remove_pages(zone, start_pfn, npages);
842         else
843                 arch_remove_memory(start_pfn << PAGE_SHIFT,
844                                    npages << PAGE_SHIFT);
845         mem_hotplug_done();
846
847         hmm_devmem_radix_release(resource);
848 }
849
850 static struct hmm_devmem *hmm_devmem_find(resource_size_t phys)
851 {
852         WARN_ON_ONCE(!rcu_read_lock_held());
853
854         return radix_tree_lookup(&hmm_devmem_radix, phys >> PA_SECTION_SHIFT);
855 }
856
857 static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
858 {
859         resource_size_t key, align_start, align_size, align_end;
860         struct device *device = devmem->device;
861         int ret, nid, is_ram;
862         unsigned long pfn;
863
864         align_start = devmem->resource->start & ~(PA_SECTION_SIZE - 1);
865         align_size = ALIGN(devmem->resource->start +
866                            resource_size(devmem->resource),
867                            PA_SECTION_SIZE) - align_start;
868
869         is_ram = region_intersects(align_start, align_size,
870                                    IORESOURCE_SYSTEM_RAM,
871                                    IORES_DESC_NONE);
872         if (is_ram == REGION_MIXED) {
873                 WARN_ONCE(1, "%s attempted on mixed region %pr\n",
874                                 __func__, devmem->resource);
875                 return -ENXIO;
876         }
877         if (is_ram == REGION_INTERSECTS)
878                 return -ENXIO;
879
880         if (devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY)
881                 devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
882         else
883                 devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
884
885         devmem->pagemap.res = devmem->resource;
886         devmem->pagemap.page_fault = hmm_devmem_fault;
887         devmem->pagemap.page_free = hmm_devmem_free;
888         devmem->pagemap.dev = devmem->device;
889         devmem->pagemap.ref = &devmem->ref;
890         devmem->pagemap.data = devmem;
891
892         mutex_lock(&hmm_devmem_lock);
893         align_end = align_start + align_size - 1;
894         for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) {
895                 struct hmm_devmem *dup;
896
897                 rcu_read_lock();
898                 dup = hmm_devmem_find(key);
899                 rcu_read_unlock();
900                 if (dup) {
901                         dev_err(device, "%s: collides with mapping for %s\n",
902                                 __func__, dev_name(dup->device));
903                         mutex_unlock(&hmm_devmem_lock);
904                         ret = -EBUSY;
905                         goto error;
906                 }
907                 ret = radix_tree_insert(&hmm_devmem_radix,
908                                         key >> PA_SECTION_SHIFT,
909                                         devmem);
910                 if (ret) {
911                         dev_err(device, "%s: failed: %d\n", __func__, ret);
912                         mutex_unlock(&hmm_devmem_lock);
913                         goto error_radix;
914                 }
915         }
916         mutex_unlock(&hmm_devmem_lock);
917
918         nid = dev_to_node(device);
919         if (nid < 0)
920                 nid = numa_mem_id();
921
922         mem_hotplug_begin();
923         /*
924          * For device private memory we call add_pages() as we only need to
925          * allocate and initialize struct page for the device memory. More-
926          * over the device memory is un-accessible thus we do not want to
927          * create a linear mapping for the memory like arch_add_memory()
928          * would do.
929          *
930          * For device public memory, which is accesible by the CPU, we do
931          * want the linear mapping and thus use arch_add_memory().
932          */
933         if (devmem->pagemap.type == MEMORY_DEVICE_PUBLIC)
934                 ret = arch_add_memory(nid, align_start, align_size, false);
935         else
936                 ret = add_pages(nid, align_start >> PAGE_SHIFT,
937                                 align_size >> PAGE_SHIFT, false);
938         if (ret) {
939                 mem_hotplug_done();
940                 goto error_add_memory;
941         }
942         move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
943                                 align_start >> PAGE_SHIFT,
944                                 align_size >> PAGE_SHIFT);
945         mem_hotplug_done();
946
947         for (pfn = devmem->pfn_first; pfn < devmem->pfn_last; pfn++) {
948                 struct page *page = pfn_to_page(pfn);
949
950                 page->pgmap = &devmem->pagemap;
951         }
952         return 0;
953
954 error_add_memory:
955         untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
956 error_radix:
957         hmm_devmem_radix_release(devmem->resource);
958 error:
959         return ret;
960 }
961
962 static int hmm_devmem_match(struct device *dev, void *data, void *match_data)
963 {
964         struct hmm_devmem *devmem = data;
965
966         return devmem->resource == match_data;
967 }
968
969 static void hmm_devmem_pages_remove(struct hmm_devmem *devmem)
970 {
971         devres_release(devmem->device, &hmm_devmem_release,
972                        &hmm_devmem_match, devmem->resource);
973 }
974
975 /*
976  * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
977  *
978  * @ops: memory event device driver callback (see struct hmm_devmem_ops)
979  * @device: device struct to bind the resource too
980  * @size: size in bytes of the device memory to add
981  * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise
982  *
983  * This function first finds an empty range of physical address big enough to
984  * contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which
985  * in turn allocates struct pages. It does not do anything beyond that; all
986  * events affecting the memory will go through the various callbacks provided
987  * by hmm_devmem_ops struct.
988  *
989  * Device driver should call this function during device initialization and
990  * is then responsible of memory management. HMM only provides helpers.
991  */
992 struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
993                                   struct device *device,
994                                   unsigned long size)
995 {
996         struct hmm_devmem *devmem;
997         resource_size_t addr;
998         int ret;
999
1000         static_branch_enable(&device_private_key);
1001
1002         devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
1003                                    GFP_KERNEL, dev_to_node(device));
1004         if (!devmem)
1005                 return ERR_PTR(-ENOMEM);
1006
1007         init_completion(&devmem->completion);
1008         devmem->pfn_first = -1UL;
1009         devmem->pfn_last = -1UL;
1010         devmem->resource = NULL;
1011         devmem->device = device;
1012         devmem->ops = ops;
1013
1014         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1015                               0, GFP_KERNEL);
1016         if (ret)
1017                 goto error_percpu_ref;
1018
1019         ret = devm_add_action(device, hmm_devmem_ref_exit, &devmem->ref);
1020         if (ret)
1021                 goto error_devm_add_action;
1022
1023         size = ALIGN(size, PA_SECTION_SIZE);
1024         addr = min((unsigned long)iomem_resource.end,
1025                    (1UL << MAX_PHYSMEM_BITS) - 1);
1026         addr = addr - size + 1UL;
1027
1028         /*
1029          * FIXME add a new helper to quickly walk resource tree and find free
1030          * range
1031          *
1032          * FIXME what about ioport_resource resource ?
1033          */
1034         for (; addr > size && addr >= iomem_resource.start; addr -= size) {
1035                 ret = region_intersects(addr, size, 0, IORES_DESC_NONE);
1036                 if (ret != REGION_DISJOINT)
1037                         continue;
1038
1039                 devmem->resource = devm_request_mem_region(device, addr, size,
1040                                                            dev_name(device));
1041                 if (!devmem->resource) {
1042                         ret = -ENOMEM;
1043                         goto error_no_resource;
1044                 }
1045                 break;
1046         }
1047         if (!devmem->resource) {
1048                 ret = -ERANGE;
1049                 goto error_no_resource;
1050         }
1051
1052         devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
1053         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1054         devmem->pfn_last = devmem->pfn_first +
1055                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1056
1057         ret = hmm_devmem_pages_create(devmem);
1058         if (ret)
1059                 goto error_pages;
1060
1061         devres_add(device, devmem);
1062
1063         ret = devm_add_action(device, hmm_devmem_ref_kill, &devmem->ref);
1064         if (ret) {
1065                 hmm_devmem_remove(devmem);
1066                 return ERR_PTR(ret);
1067         }
1068
1069         return devmem;
1070
1071 error_pages:
1072         devm_release_mem_region(device, devmem->resource->start,
1073                                 resource_size(devmem->resource));
1074 error_no_resource:
1075 error_devm_add_action:
1076         hmm_devmem_ref_kill(&devmem->ref);
1077         hmm_devmem_ref_exit(&devmem->ref);
1078 error_percpu_ref:
1079         devres_free(devmem);
1080         return ERR_PTR(ret);
1081 }
1082 EXPORT_SYMBOL(hmm_devmem_add);
1083
1084 struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
1085                                            struct device *device,
1086                                            struct resource *res)
1087 {
1088         struct hmm_devmem *devmem;
1089         int ret;
1090
1091         if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY)
1092                 return ERR_PTR(-EINVAL);
1093
1094         static_branch_enable(&device_private_key);
1095
1096         devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
1097                                    GFP_KERNEL, dev_to_node(device));
1098         if (!devmem)
1099                 return ERR_PTR(-ENOMEM);
1100
1101         init_completion(&devmem->completion);
1102         devmem->pfn_first = -1UL;
1103         devmem->pfn_last = -1UL;
1104         devmem->resource = res;
1105         devmem->device = device;
1106         devmem->ops = ops;
1107
1108         ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
1109                               0, GFP_KERNEL);
1110         if (ret)
1111                 goto error_percpu_ref;
1112
1113         ret = devm_add_action(device, hmm_devmem_ref_exit, &devmem->ref);
1114         if (ret)
1115                 goto error_devm_add_action;
1116
1117
1118         devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
1119         devmem->pfn_last = devmem->pfn_first +
1120                            (resource_size(devmem->resource) >> PAGE_SHIFT);
1121
1122         ret = hmm_devmem_pages_create(devmem);
1123         if (ret)
1124                 goto error_devm_add_action;
1125
1126         devres_add(device, devmem);
1127
1128         ret = devm_add_action(device, hmm_devmem_ref_kill, &devmem->ref);
1129         if (ret) {
1130                 hmm_devmem_remove(devmem);
1131                 return ERR_PTR(ret);
1132         }
1133
1134         return devmem;
1135
1136 error_devm_add_action:
1137         hmm_devmem_ref_kill(&devmem->ref);
1138         hmm_devmem_ref_exit(&devmem->ref);
1139 error_percpu_ref:
1140         devres_free(devmem);
1141         return ERR_PTR(ret);
1142 }
1143 EXPORT_SYMBOL(hmm_devmem_add_resource);
1144
1145 /*
1146  * hmm_devmem_remove() - remove device memory (kill and free ZONE_DEVICE)
1147  *
1148  * @devmem: hmm_devmem struct use to track and manage the ZONE_DEVICE memory
1149  *
1150  * This will hot-unplug memory that was hotplugged by hmm_devmem_add on behalf
1151  * of the device driver. It will free struct page and remove the resource that
1152  * reserved the physical address range for this device memory.
1153  */
1154 void hmm_devmem_remove(struct hmm_devmem *devmem)
1155 {
1156         resource_size_t start, size;
1157         struct device *device;
1158         bool cdm = false;
1159
1160         if (!devmem)
1161                 return;
1162
1163         device = devmem->device;
1164         start = devmem->resource->start;
1165         size = resource_size(devmem->resource);
1166
1167         cdm = devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY;
1168         hmm_devmem_ref_kill(&devmem->ref);
1169         hmm_devmem_ref_exit(&devmem->ref);
1170         hmm_devmem_pages_remove(devmem);
1171
1172         if (!cdm)
1173                 devm_release_mem_region(device, start, size);
1174 }
1175 EXPORT_SYMBOL(hmm_devmem_remove);
1176
1177 /*
1178  * A device driver that wants to handle multiple devices memory through a
1179  * single fake device can use hmm_device to do so. This is purely a helper
1180  * and it is not needed to make use of any HMM functionality.
1181  */
1182 #define HMM_DEVICE_MAX 256
1183
1184 static DECLARE_BITMAP(hmm_device_mask, HMM_DEVICE_MAX);
1185 static DEFINE_SPINLOCK(hmm_device_lock);
1186 static struct class *hmm_device_class;
1187 static dev_t hmm_device_devt;
1188
1189 static void hmm_device_release(struct device *device)
1190 {
1191         struct hmm_device *hmm_device;
1192
1193         hmm_device = container_of(device, struct hmm_device, device);
1194         spin_lock(&hmm_device_lock);
1195         clear_bit(hmm_device->minor, hmm_device_mask);
1196         spin_unlock(&hmm_device_lock);
1197
1198         kfree(hmm_device);
1199 }
1200
1201 struct hmm_device *hmm_device_new(void *drvdata)
1202 {
1203         struct hmm_device *hmm_device;
1204
1205         hmm_device = kzalloc(sizeof(*hmm_device), GFP_KERNEL);
1206         if (!hmm_device)
1207                 return ERR_PTR(-ENOMEM);
1208
1209         spin_lock(&hmm_device_lock);
1210         hmm_device->minor = find_first_zero_bit(hmm_device_mask, HMM_DEVICE_MAX);
1211         if (hmm_device->minor >= HMM_DEVICE_MAX) {
1212                 spin_unlock(&hmm_device_lock);
1213                 kfree(hmm_device);
1214                 return ERR_PTR(-EBUSY);
1215         }
1216         set_bit(hmm_device->minor, hmm_device_mask);
1217         spin_unlock(&hmm_device_lock);
1218
1219         dev_set_name(&hmm_device->device, "hmm_device%d", hmm_device->minor);
1220         hmm_device->device.devt = MKDEV(MAJOR(hmm_device_devt),
1221                                         hmm_device->minor);
1222         hmm_device->device.release = hmm_device_release;
1223         dev_set_drvdata(&hmm_device->device, drvdata);
1224         hmm_device->device.class = hmm_device_class;
1225         device_initialize(&hmm_device->device);
1226
1227         return hmm_device;
1228 }
1229 EXPORT_SYMBOL(hmm_device_new);
1230
1231 void hmm_device_put(struct hmm_device *hmm_device)
1232 {
1233         put_device(&hmm_device->device);
1234 }
1235 EXPORT_SYMBOL(hmm_device_put);
1236
1237 static int __init hmm_init(void)
1238 {
1239         int ret;
1240
1241         ret = alloc_chrdev_region(&hmm_device_devt, 0,
1242                                   HMM_DEVICE_MAX,
1243                                   "hmm_device");
1244         if (ret)
1245                 return ret;
1246
1247         hmm_device_class = class_create(THIS_MODULE, "hmm_device");
1248         if (IS_ERR(hmm_device_class)) {
1249                 unregister_chrdev_region(hmm_device_devt, HMM_DEVICE_MAX);
1250                 return PTR_ERR(hmm_device_class);
1251         }
1252         return 0;
1253 }
1254
1255 device_initcall(hmm_init);
1256 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */