mm: page_alloc: unreserve highatomic page blocks before oom
[linux-2.6-microblaze.git] / mm / hmm.c
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright 2013 Red Hat Inc.
4  *
5  * Authors: Jérôme Glisse <jglisse@redhat.com>
6  */
7 /*
8  * Refer to include/linux/hmm.h for information about heterogeneous memory
9  * management or HMM for short.
10  */
11 #include <linux/pagewalk.h>
12 #include <linux/hmm.h>
13 #include <linux/init.h>
14 #include <linux/rmap.h>
15 #include <linux/swap.h>
16 #include <linux/slab.h>
17 #include <linux/sched.h>
18 #include <linux/mmzone.h>
19 #include <linux/pagemap.h>
20 #include <linux/swapops.h>
21 #include <linux/hugetlb.h>
22 #include <linux/memremap.h>
23 #include <linux/sched/mm.h>
24 #include <linux/jump_label.h>
25 #include <linux/dma-mapping.h>
26 #include <linux/mmu_notifier.h>
27 #include <linux/memory_hotplug.h>
28
29 #include "internal.h"
30
31 struct hmm_vma_walk {
32         struct hmm_range        *range;
33         unsigned long           last;
34 };
35
36 enum {
37         HMM_NEED_FAULT = 1 << 0,
38         HMM_NEED_WRITE_FAULT = 1 << 1,
39         HMM_NEED_ALL_BITS = HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT,
40 };
41
42 static int hmm_pfns_fill(unsigned long addr, unsigned long end,
43                          struct hmm_range *range, unsigned long cpu_flags)
44 {
45         unsigned long i = (addr - range->start) >> PAGE_SHIFT;
46
47         for (; addr < end; addr += PAGE_SIZE, i++)
48                 range->hmm_pfns[i] = cpu_flags;
49         return 0;
50 }
51
52 /*
53  * hmm_vma_fault() - fault in a range lacking valid pmd or pte(s)
54  * @addr: range virtual start address (inclusive)
55  * @end: range virtual end address (exclusive)
56  * @required_fault: HMM_NEED_* flags
57  * @walk: mm_walk structure
58  * Return: -EBUSY after page fault, or page fault error
59  *
60  * This function will be called whenever pmd_none() or pte_none() returns true,
61  * or whenever there is no page directory covering the virtual address range.
62  */
63 static int hmm_vma_fault(unsigned long addr, unsigned long end,
64                          unsigned int required_fault, struct mm_walk *walk)
65 {
66         struct hmm_vma_walk *hmm_vma_walk = walk->private;
67         struct vm_area_struct *vma = walk->vma;
68         unsigned int fault_flags = FAULT_FLAG_REMOTE;
69
70         WARN_ON_ONCE(!required_fault);
71         hmm_vma_walk->last = addr;
72
73         if (required_fault & HMM_NEED_WRITE_FAULT) {
74                 if (!(vma->vm_flags & VM_WRITE))
75                         return -EPERM;
76                 fault_flags |= FAULT_FLAG_WRITE;
77         }
78
79         for (; addr < end; addr += PAGE_SIZE)
80                 if (handle_mm_fault(vma, addr, fault_flags, NULL) &
81                     VM_FAULT_ERROR)
82                         return -EFAULT;
83         return -EBUSY;
84 }
85
86 static unsigned int hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
87                                        unsigned long pfn_req_flags,
88                                        unsigned long cpu_flags)
89 {
90         struct hmm_range *range = hmm_vma_walk->range;
91
92         /*
93          * So we not only consider the individual per page request we also
94          * consider the default flags requested for the range. The API can
95          * be used 2 ways. The first one where the HMM user coalesces
96          * multiple page faults into one request and sets flags per pfn for
97          * those faults. The second one where the HMM user wants to pre-
98          * fault a range with specific flags. For the latter one it is a
99          * waste to have the user pre-fill the pfn arrays with a default
100          * flags value.
101          */
102         pfn_req_flags &= range->pfn_flags_mask;
103         pfn_req_flags |= range->default_flags;
104
105         /* We aren't ask to do anything ... */
106         if (!(pfn_req_flags & HMM_PFN_REQ_FAULT))
107                 return 0;
108
109         /* Need to write fault ? */
110         if ((pfn_req_flags & HMM_PFN_REQ_WRITE) &&
111             !(cpu_flags & HMM_PFN_WRITE))
112                 return HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT;
113
114         /* If CPU page table is not valid then we need to fault */
115         if (!(cpu_flags & HMM_PFN_VALID))
116                 return HMM_NEED_FAULT;
117         return 0;
118 }
119
120 static unsigned int
121 hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
122                      const unsigned long hmm_pfns[], unsigned long npages,
123                      unsigned long cpu_flags)
124 {
125         struct hmm_range *range = hmm_vma_walk->range;
126         unsigned int required_fault = 0;
127         unsigned long i;
128
129         /*
130          * If the default flags do not request to fault pages, and the mask does
131          * not allow for individual pages to be faulted, then
132          * hmm_pte_need_fault() will always return 0.
133          */
134         if (!((range->default_flags | range->pfn_flags_mask) &
135               HMM_PFN_REQ_FAULT))
136                 return 0;
137
138         for (i = 0; i < npages; ++i) {
139                 required_fault |= hmm_pte_need_fault(hmm_vma_walk, hmm_pfns[i],
140                                                      cpu_flags);
141                 if (required_fault == HMM_NEED_ALL_BITS)
142                         return required_fault;
143         }
144         return required_fault;
145 }
146
147 static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
148                              __always_unused int depth, struct mm_walk *walk)
149 {
150         struct hmm_vma_walk *hmm_vma_walk = walk->private;
151         struct hmm_range *range = hmm_vma_walk->range;
152         unsigned int required_fault;
153         unsigned long i, npages;
154         unsigned long *hmm_pfns;
155
156         i = (addr - range->start) >> PAGE_SHIFT;
157         npages = (end - addr) >> PAGE_SHIFT;
158         hmm_pfns = &range->hmm_pfns[i];
159         required_fault =
160                 hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0);
161         if (!walk->vma) {
162                 if (required_fault)
163                         return -EFAULT;
164                 return hmm_pfns_fill(addr, end, range, HMM_PFN_ERROR);
165         }
166         if (required_fault)
167                 return hmm_vma_fault(addr, end, required_fault, walk);
168         return hmm_pfns_fill(addr, end, range, 0);
169 }
170
171 static inline unsigned long hmm_pfn_flags_order(unsigned long order)
172 {
173         return order << HMM_PFN_ORDER_SHIFT;
174 }
175
176 static inline unsigned long pmd_to_hmm_pfn_flags(struct hmm_range *range,
177                                                  pmd_t pmd)
178 {
179         if (pmd_protnone(pmd))
180                 return 0;
181         return (pmd_write(pmd) ? (HMM_PFN_VALID | HMM_PFN_WRITE) :
182                                  HMM_PFN_VALID) |
183                hmm_pfn_flags_order(PMD_SHIFT - PAGE_SHIFT);
184 }
185
186 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
187 static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
188                               unsigned long end, unsigned long hmm_pfns[],
189                               pmd_t pmd)
190 {
191         struct hmm_vma_walk *hmm_vma_walk = walk->private;
192         struct hmm_range *range = hmm_vma_walk->range;
193         unsigned long pfn, npages, i;
194         unsigned int required_fault;
195         unsigned long cpu_flags;
196
197         npages = (end - addr) >> PAGE_SHIFT;
198         cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
199         required_fault =
200                 hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, cpu_flags);
201         if (required_fault)
202                 return hmm_vma_fault(addr, end, required_fault, walk);
203
204         pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
205         for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
206                 hmm_pfns[i] = pfn | cpu_flags;
207         return 0;
208 }
209 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
210 /* stub to allow the code below to compile */
211 int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
212                 unsigned long end, unsigned long hmm_pfns[], pmd_t pmd);
213 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
214
215 static inline unsigned long pte_to_hmm_pfn_flags(struct hmm_range *range,
216                                                  pte_t pte)
217 {
218         if (pte_none(pte) || !pte_present(pte) || pte_protnone(pte))
219                 return 0;
220         return pte_write(pte) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : HMM_PFN_VALID;
221 }
222
223 static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
224                               unsigned long end, pmd_t *pmdp, pte_t *ptep,
225                               unsigned long *hmm_pfn)
226 {
227         struct hmm_vma_walk *hmm_vma_walk = walk->private;
228         struct hmm_range *range = hmm_vma_walk->range;
229         unsigned int required_fault;
230         unsigned long cpu_flags;
231         pte_t pte = ptep_get(ptep);
232         uint64_t pfn_req_flags = *hmm_pfn;
233
234         if (pte_none_mostly(pte)) {
235                 required_fault =
236                         hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
237                 if (required_fault)
238                         goto fault;
239                 *hmm_pfn = 0;
240                 return 0;
241         }
242
243         if (!pte_present(pte)) {
244                 swp_entry_t entry = pte_to_swp_entry(pte);
245
246                 /*
247                  * Don't fault in device private pages owned by the caller,
248                  * just report the PFN.
249                  */
250                 if (is_device_private_entry(entry) &&
251                     pfn_swap_entry_to_page(entry)->pgmap->owner ==
252                     range->dev_private_owner) {
253                         cpu_flags = HMM_PFN_VALID;
254                         if (is_writable_device_private_entry(entry))
255                                 cpu_flags |= HMM_PFN_WRITE;
256                         *hmm_pfn = swp_offset_pfn(entry) | cpu_flags;
257                         return 0;
258                 }
259
260                 required_fault =
261                         hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
262                 if (!required_fault) {
263                         *hmm_pfn = 0;
264                         return 0;
265                 }
266
267                 if (!non_swap_entry(entry))
268                         goto fault;
269
270                 if (is_device_private_entry(entry))
271                         goto fault;
272
273                 if (is_device_exclusive_entry(entry))
274                         goto fault;
275
276                 if (is_migration_entry(entry)) {
277                         pte_unmap(ptep);
278                         hmm_vma_walk->last = addr;
279                         migration_entry_wait(walk->mm, pmdp, addr);
280                         return -EBUSY;
281                 }
282
283                 /* Report error for everything else */
284                 pte_unmap(ptep);
285                 return -EFAULT;
286         }
287
288         cpu_flags = pte_to_hmm_pfn_flags(range, pte);
289         required_fault =
290                 hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
291         if (required_fault)
292                 goto fault;
293
294         /*
295          * Bypass devmap pte such as DAX page when all pfn requested
296          * flags(pfn_req_flags) are fulfilled.
297          * Since each architecture defines a struct page for the zero page, just
298          * fall through and treat it like a normal page.
299          */
300         if (!vm_normal_page(walk->vma, addr, pte) &&
301             !pte_devmap(pte) &&
302             !is_zero_pfn(pte_pfn(pte))) {
303                 if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) {
304                         pte_unmap(ptep);
305                         return -EFAULT;
306                 }
307                 *hmm_pfn = HMM_PFN_ERROR;
308                 return 0;
309         }
310
311         *hmm_pfn = pte_pfn(pte) | cpu_flags;
312         return 0;
313
314 fault:
315         pte_unmap(ptep);
316         /* Fault any virtual address we were asked to fault */
317         return hmm_vma_fault(addr, end, required_fault, walk);
318 }
319
320 static int hmm_vma_walk_pmd(pmd_t *pmdp,
321                             unsigned long start,
322                             unsigned long end,
323                             struct mm_walk *walk)
324 {
325         struct hmm_vma_walk *hmm_vma_walk = walk->private;
326         struct hmm_range *range = hmm_vma_walk->range;
327         unsigned long *hmm_pfns =
328                 &range->hmm_pfns[(start - range->start) >> PAGE_SHIFT];
329         unsigned long npages = (end - start) >> PAGE_SHIFT;
330         unsigned long addr = start;
331         pte_t *ptep;
332         pmd_t pmd;
333
334 again:
335         pmd = pmdp_get_lockless(pmdp);
336         if (pmd_none(pmd))
337                 return hmm_vma_walk_hole(start, end, -1, walk);
338
339         if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
340                 if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) {
341                         hmm_vma_walk->last = addr;
342                         pmd_migration_entry_wait(walk->mm, pmdp);
343                         return -EBUSY;
344                 }
345                 return hmm_pfns_fill(start, end, range, 0);
346         }
347
348         if (!pmd_present(pmd)) {
349                 if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0))
350                         return -EFAULT;
351                 return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
352         }
353
354         if (pmd_devmap(pmd) || pmd_trans_huge(pmd)) {
355                 /*
356                  * No need to take pmd_lock here, even if some other thread
357                  * is splitting the huge pmd we will get that event through
358                  * mmu_notifier callback.
359                  *
360                  * So just read pmd value and check again it's a transparent
361                  * huge or device mapping one and compute corresponding pfn
362                  * values.
363                  */
364                 pmd = pmdp_get_lockless(pmdp);
365                 if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
366                         goto again;
367
368                 return hmm_vma_handle_pmd(walk, addr, end, hmm_pfns, pmd);
369         }
370
371         /*
372          * We have handled all the valid cases above ie either none, migration,
373          * huge or transparent huge. At this point either it is a valid pmd
374          * entry pointing to pte directory or it is a bad pmd that will not
375          * recover.
376          */
377         if (pmd_bad(pmd)) {
378                 if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0))
379                         return -EFAULT;
380                 return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
381         }
382
383         ptep = pte_offset_map(pmdp, addr);
384         if (!ptep)
385                 goto again;
386         for (; addr < end; addr += PAGE_SIZE, ptep++, hmm_pfns++) {
387                 int r;
388
389                 r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, hmm_pfns);
390                 if (r) {
391                         /* hmm_vma_handle_pte() did pte_unmap() */
392                         return r;
393                 }
394         }
395         pte_unmap(ptep - 1);
396         return 0;
397 }
398
399 #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && \
400     defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
401 static inline unsigned long pud_to_hmm_pfn_flags(struct hmm_range *range,
402                                                  pud_t pud)
403 {
404         if (!pud_present(pud))
405                 return 0;
406         return (pud_write(pud) ? (HMM_PFN_VALID | HMM_PFN_WRITE) :
407                                  HMM_PFN_VALID) |
408                hmm_pfn_flags_order(PUD_SHIFT - PAGE_SHIFT);
409 }
410
411 static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
412                 struct mm_walk *walk)
413 {
414         struct hmm_vma_walk *hmm_vma_walk = walk->private;
415         struct hmm_range *range = hmm_vma_walk->range;
416         unsigned long addr = start;
417         pud_t pud;
418         spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma);
419
420         if (!ptl)
421                 return 0;
422
423         /* Normally we don't want to split the huge page */
424         walk->action = ACTION_CONTINUE;
425
426         pud = READ_ONCE(*pudp);
427         if (pud_none(pud)) {
428                 spin_unlock(ptl);
429                 return hmm_vma_walk_hole(start, end, -1, walk);
430         }
431
432         if (pud_huge(pud) && pud_devmap(pud)) {
433                 unsigned long i, npages, pfn;
434                 unsigned int required_fault;
435                 unsigned long *hmm_pfns;
436                 unsigned long cpu_flags;
437
438                 if (!pud_present(pud)) {
439                         spin_unlock(ptl);
440                         return hmm_vma_walk_hole(start, end, -1, walk);
441                 }
442
443                 i = (addr - range->start) >> PAGE_SHIFT;
444                 npages = (end - addr) >> PAGE_SHIFT;
445                 hmm_pfns = &range->hmm_pfns[i];
446
447                 cpu_flags = pud_to_hmm_pfn_flags(range, pud);
448                 required_fault = hmm_range_need_fault(hmm_vma_walk, hmm_pfns,
449                                                       npages, cpu_flags);
450                 if (required_fault) {
451                         spin_unlock(ptl);
452                         return hmm_vma_fault(addr, end, required_fault, walk);
453                 }
454
455                 pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
456                 for (i = 0; i < npages; ++i, ++pfn)
457                         hmm_pfns[i] = pfn | cpu_flags;
458                 goto out_unlock;
459         }
460
461         /* Ask for the PUD to be split */
462         walk->action = ACTION_SUBTREE;
463
464 out_unlock:
465         spin_unlock(ptl);
466         return 0;
467 }
468 #else
469 #define hmm_vma_walk_pud        NULL
470 #endif
471
472 #ifdef CONFIG_HUGETLB_PAGE
473 static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
474                                       unsigned long start, unsigned long end,
475                                       struct mm_walk *walk)
476 {
477         unsigned long addr = start, i, pfn;
478         struct hmm_vma_walk *hmm_vma_walk = walk->private;
479         struct hmm_range *range = hmm_vma_walk->range;
480         struct vm_area_struct *vma = walk->vma;
481         unsigned int required_fault;
482         unsigned long pfn_req_flags;
483         unsigned long cpu_flags;
484         spinlock_t *ptl;
485         pte_t entry;
486
487         ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
488         entry = huge_ptep_get(pte);
489
490         i = (start - range->start) >> PAGE_SHIFT;
491         pfn_req_flags = range->hmm_pfns[i];
492         cpu_flags = pte_to_hmm_pfn_flags(range, entry) |
493                     hmm_pfn_flags_order(huge_page_order(hstate_vma(vma)));
494         required_fault =
495                 hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
496         if (required_fault) {
497                 int ret;
498
499                 spin_unlock(ptl);
500                 hugetlb_vma_unlock_read(vma);
501                 /*
502                  * Avoid deadlock: drop the vma lock before calling
503                  * hmm_vma_fault(), which will itself potentially take and
504                  * drop the vma lock. This is also correct from a
505                  * protection point of view, because there is no further
506                  * use here of either pte or ptl after dropping the vma
507                  * lock.
508                  */
509                 ret = hmm_vma_fault(addr, end, required_fault, walk);
510                 hugetlb_vma_lock_read(vma);
511                 return ret;
512         }
513
514         pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);
515         for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
516                 range->hmm_pfns[i] = pfn | cpu_flags;
517
518         spin_unlock(ptl);
519         return 0;
520 }
521 #else
522 #define hmm_vma_walk_hugetlb_entry NULL
523 #endif /* CONFIG_HUGETLB_PAGE */
524
525 static int hmm_vma_walk_test(unsigned long start, unsigned long end,
526                              struct mm_walk *walk)
527 {
528         struct hmm_vma_walk *hmm_vma_walk = walk->private;
529         struct hmm_range *range = hmm_vma_walk->range;
530         struct vm_area_struct *vma = walk->vma;
531
532         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)) &&
533             vma->vm_flags & VM_READ)
534                 return 0;
535
536         /*
537          * vma ranges that don't have struct page backing them or map I/O
538          * devices directly cannot be handled by hmm_range_fault().
539          *
540          * If the vma does not allow read access, then assume that it does not
541          * allow write access either. HMM does not support architectures that
542          * allow write without read.
543          *
544          * If a fault is requested for an unsupported range then it is a hard
545          * failure.
546          */
547         if (hmm_range_need_fault(hmm_vma_walk,
548                                  range->hmm_pfns +
549                                          ((start - range->start) >> PAGE_SHIFT),
550                                  (end - start) >> PAGE_SHIFT, 0))
551                 return -EFAULT;
552
553         hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
554
555         /* Skip this vma and continue processing the next vma. */
556         return 1;
557 }
558
559 static const struct mm_walk_ops hmm_walk_ops = {
560         .pud_entry      = hmm_vma_walk_pud,
561         .pmd_entry      = hmm_vma_walk_pmd,
562         .pte_hole       = hmm_vma_walk_hole,
563         .hugetlb_entry  = hmm_vma_walk_hugetlb_entry,
564         .test_walk      = hmm_vma_walk_test,
565         .walk_lock      = PGWALK_RDLOCK,
566 };
567
568 /**
569  * hmm_range_fault - try to fault some address in a virtual address range
570  * @range:      argument structure
571  *
572  * Returns 0 on success or one of the following error codes:
573  *
574  * -EINVAL:     Invalid arguments or mm or virtual address is in an invalid vma
575  *              (e.g., device file vma).
576  * -ENOMEM:     Out of memory.
577  * -EPERM:      Invalid permission (e.g., asking for write and range is read
578  *              only).
579  * -EBUSY:      The range has been invalidated and the caller needs to wait for
580  *              the invalidation to finish.
581  * -EFAULT:     A page was requested to be valid and could not be made valid
582  *              ie it has no backing VMA or it is illegal to access
583  *
584  * This is similar to get_user_pages(), except that it can read the page tables
585  * without mutating them (ie causing faults).
586  */
587 int hmm_range_fault(struct hmm_range *range)
588 {
589         struct hmm_vma_walk hmm_vma_walk = {
590                 .range = range,
591                 .last = range->start,
592         };
593         struct mm_struct *mm = range->notifier->mm;
594         int ret;
595
596         mmap_assert_locked(mm);
597
598         do {
599                 /* If range is no longer valid force retry. */
600                 if (mmu_interval_check_retry(range->notifier,
601                                              range->notifier_seq))
602                         return -EBUSY;
603                 ret = walk_page_range(mm, hmm_vma_walk.last, range->end,
604                                       &hmm_walk_ops, &hmm_vma_walk);
605                 /*
606                  * When -EBUSY is returned the loop restarts with
607                  * hmm_vma_walk.last set to an address that has not been stored
608                  * in pfns. All entries < last in the pfn array are set to their
609                  * output, and all >= are still at their input values.
610                  */
611         } while (ret == -EBUSY);
612         return ret;
613 }
614 EXPORT_SYMBOL(hmm_range_fault);