Merge branch 'rework/kthreads' into for-linus
[platform/kernel/linux-starfive.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 bool hmm_is_device_private_entry(struct hmm_range *range,
216                 swp_entry_t entry)
217 {
218         return is_device_private_entry(entry) &&
219                 pfn_swap_entry_to_page(entry)->pgmap->owner ==
220                 range->dev_private_owner;
221 }
222
223 static inline unsigned long pte_to_hmm_pfn_flags(struct hmm_range *range,
224                                                  pte_t pte)
225 {
226         if (pte_none(pte) || !pte_present(pte) || pte_protnone(pte))
227                 return 0;
228         return pte_write(pte) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : HMM_PFN_VALID;
229 }
230
231 static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
232                               unsigned long end, pmd_t *pmdp, pte_t *ptep,
233                               unsigned long *hmm_pfn)
234 {
235         struct hmm_vma_walk *hmm_vma_walk = walk->private;
236         struct hmm_range *range = hmm_vma_walk->range;
237         unsigned int required_fault;
238         unsigned long cpu_flags;
239         pte_t pte = *ptep;
240         uint64_t pfn_req_flags = *hmm_pfn;
241
242         if (pte_none_mostly(pte)) {
243                 required_fault =
244                         hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
245                 if (required_fault)
246                         goto fault;
247                 *hmm_pfn = 0;
248                 return 0;
249         }
250
251         if (!pte_present(pte)) {
252                 swp_entry_t entry = pte_to_swp_entry(pte);
253
254                 /*
255                  * Never fault in device private pages, but just report
256                  * the PFN even if not present.
257                  */
258                 if (hmm_is_device_private_entry(range, entry)) {
259                         cpu_flags = HMM_PFN_VALID;
260                         if (is_writable_device_private_entry(entry))
261                                 cpu_flags |= HMM_PFN_WRITE;
262                         *hmm_pfn = swp_offset(entry) | cpu_flags;
263                         return 0;
264                 }
265
266                 required_fault =
267                         hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
268                 if (!required_fault) {
269                         *hmm_pfn = 0;
270                         return 0;
271                 }
272
273                 if (!non_swap_entry(entry))
274                         goto fault;
275
276                 if (is_device_exclusive_entry(entry))
277                         goto fault;
278
279                 if (is_migration_entry(entry)) {
280                         pte_unmap(ptep);
281                         hmm_vma_walk->last = addr;
282                         migration_entry_wait(walk->mm, pmdp, addr);
283                         return -EBUSY;
284                 }
285
286                 /* Report error for everything else */
287                 pte_unmap(ptep);
288                 return -EFAULT;
289         }
290
291         cpu_flags = pte_to_hmm_pfn_flags(range, pte);
292         required_fault =
293                 hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
294         if (required_fault)
295                 goto fault;
296
297         /*
298          * Bypass devmap pte such as DAX page when all pfn requested
299          * flags(pfn_req_flags) are fulfilled.
300          * Since each architecture defines a struct page for the zero page, just
301          * fall through and treat it like a normal page.
302          */
303         if (!vm_normal_page(walk->vma, addr, pte) &&
304             !pte_devmap(pte) &&
305             !is_zero_pfn(pte_pfn(pte))) {
306                 if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) {
307                         pte_unmap(ptep);
308                         return -EFAULT;
309                 }
310                 *hmm_pfn = HMM_PFN_ERROR;
311                 return 0;
312         }
313
314         *hmm_pfn = pte_pfn(pte) | cpu_flags;
315         return 0;
316
317 fault:
318         pte_unmap(ptep);
319         /* Fault any virtual address we were asked to fault */
320         return hmm_vma_fault(addr, end, required_fault, walk);
321 }
322
323 static int hmm_vma_walk_pmd(pmd_t *pmdp,
324                             unsigned long start,
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         unsigned long *hmm_pfns =
331                 &range->hmm_pfns[(start - range->start) >> PAGE_SHIFT];
332         unsigned long npages = (end - start) >> PAGE_SHIFT;
333         unsigned long addr = start;
334         pte_t *ptep;
335         pmd_t pmd;
336
337 again:
338         pmd = READ_ONCE(*pmdp);
339         if (pmd_none(pmd))
340                 return hmm_vma_walk_hole(start, end, -1, walk);
341
342         if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
343                 if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) {
344                         hmm_vma_walk->last = addr;
345                         pmd_migration_entry_wait(walk->mm, pmdp);
346                         return -EBUSY;
347                 }
348                 return hmm_pfns_fill(start, end, range, 0);
349         }
350
351         if (!pmd_present(pmd)) {
352                 if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0))
353                         return -EFAULT;
354                 return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
355         }
356
357         if (pmd_devmap(pmd) || pmd_trans_huge(pmd)) {
358                 /*
359                  * No need to take pmd_lock here, even if some other thread
360                  * is splitting the huge pmd we will get that event through
361                  * mmu_notifier callback.
362                  *
363                  * So just read pmd value and check again it's a transparent
364                  * huge or device mapping one and compute corresponding pfn
365                  * values.
366                  */
367                 pmd = pmd_read_atomic(pmdp);
368                 barrier();
369                 if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
370                         goto again;
371
372                 return hmm_vma_handle_pmd(walk, addr, end, hmm_pfns, pmd);
373         }
374
375         /*
376          * We have handled all the valid cases above ie either none, migration,
377          * huge or transparent huge. At this point either it is a valid pmd
378          * entry pointing to pte directory or it is a bad pmd that will not
379          * recover.
380          */
381         if (pmd_bad(pmd)) {
382                 if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0))
383                         return -EFAULT;
384                 return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
385         }
386
387         ptep = pte_offset_map(pmdp, addr);
388         for (; addr < end; addr += PAGE_SIZE, ptep++, hmm_pfns++) {
389                 int r;
390
391                 r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, hmm_pfns);
392                 if (r) {
393                         /* hmm_vma_handle_pte() did pte_unmap() */
394                         return r;
395                 }
396         }
397         pte_unmap(ptep - 1);
398         return 0;
399 }
400
401 #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && \
402     defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
403 static inline unsigned long pud_to_hmm_pfn_flags(struct hmm_range *range,
404                                                  pud_t pud)
405 {
406         if (!pud_present(pud))
407                 return 0;
408         return (pud_write(pud) ? (HMM_PFN_VALID | HMM_PFN_WRITE) :
409                                  HMM_PFN_VALID) |
410                hmm_pfn_flags_order(PUD_SHIFT - PAGE_SHIFT);
411 }
412
413 static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
414                 struct mm_walk *walk)
415 {
416         struct hmm_vma_walk *hmm_vma_walk = walk->private;
417         struct hmm_range *range = hmm_vma_walk->range;
418         unsigned long addr = start;
419         pud_t pud;
420         spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma);
421
422         if (!ptl)
423                 return 0;
424
425         /* Normally we don't want to split the huge page */
426         walk->action = ACTION_CONTINUE;
427
428         pud = READ_ONCE(*pudp);
429         if (pud_none(pud)) {
430                 spin_unlock(ptl);
431                 return hmm_vma_walk_hole(start, end, -1, walk);
432         }
433
434         if (pud_huge(pud) && pud_devmap(pud)) {
435                 unsigned long i, npages, pfn;
436                 unsigned int required_fault;
437                 unsigned long *hmm_pfns;
438                 unsigned long cpu_flags;
439
440                 if (!pud_present(pud)) {
441                         spin_unlock(ptl);
442                         return hmm_vma_walk_hole(start, end, -1, walk);
443                 }
444
445                 i = (addr - range->start) >> PAGE_SHIFT;
446                 npages = (end - addr) >> PAGE_SHIFT;
447                 hmm_pfns = &range->hmm_pfns[i];
448
449                 cpu_flags = pud_to_hmm_pfn_flags(range, pud);
450                 required_fault = hmm_range_need_fault(hmm_vma_walk, hmm_pfns,
451                                                       npages, cpu_flags);
452                 if (required_fault) {
453                         spin_unlock(ptl);
454                         return hmm_vma_fault(addr, end, required_fault, walk);
455                 }
456
457                 pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
458                 for (i = 0; i < npages; ++i, ++pfn)
459                         hmm_pfns[i] = pfn | cpu_flags;
460                 goto out_unlock;
461         }
462
463         /* Ask for the PUD to be split */
464         walk->action = ACTION_SUBTREE;
465
466 out_unlock:
467         spin_unlock(ptl);
468         return 0;
469 }
470 #else
471 #define hmm_vma_walk_pud        NULL
472 #endif
473
474 #ifdef CONFIG_HUGETLB_PAGE
475 static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
476                                       unsigned long start, unsigned long end,
477                                       struct mm_walk *walk)
478 {
479         unsigned long addr = start, i, pfn;
480         struct hmm_vma_walk *hmm_vma_walk = walk->private;
481         struct hmm_range *range = hmm_vma_walk->range;
482         struct vm_area_struct *vma = walk->vma;
483         unsigned int required_fault;
484         unsigned long pfn_req_flags;
485         unsigned long cpu_flags;
486         spinlock_t *ptl;
487         pte_t entry;
488
489         ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
490         entry = huge_ptep_get(pte);
491
492         i = (start - range->start) >> PAGE_SHIFT;
493         pfn_req_flags = range->hmm_pfns[i];
494         cpu_flags = pte_to_hmm_pfn_flags(range, entry) |
495                     hmm_pfn_flags_order(huge_page_order(hstate_vma(vma)));
496         required_fault =
497                 hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
498         if (required_fault) {
499                 spin_unlock(ptl);
500                 return hmm_vma_fault(addr, end, required_fault, walk);
501         }
502
503         pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);
504         for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
505                 range->hmm_pfns[i] = pfn | cpu_flags;
506
507         spin_unlock(ptl);
508         return 0;
509 }
510 #else
511 #define hmm_vma_walk_hugetlb_entry NULL
512 #endif /* CONFIG_HUGETLB_PAGE */
513
514 static int hmm_vma_walk_test(unsigned long start, unsigned long end,
515                              struct mm_walk *walk)
516 {
517         struct hmm_vma_walk *hmm_vma_walk = walk->private;
518         struct hmm_range *range = hmm_vma_walk->range;
519         struct vm_area_struct *vma = walk->vma;
520
521         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)) &&
522             vma->vm_flags & VM_READ)
523                 return 0;
524
525         /*
526          * vma ranges that don't have struct page backing them or map I/O
527          * devices directly cannot be handled by hmm_range_fault().
528          *
529          * If the vma does not allow read access, then assume that it does not
530          * allow write access either. HMM does not support architectures that
531          * allow write without read.
532          *
533          * If a fault is requested for an unsupported range then it is a hard
534          * failure.
535          */
536         if (hmm_range_need_fault(hmm_vma_walk,
537                                  range->hmm_pfns +
538                                          ((start - range->start) >> PAGE_SHIFT),
539                                  (end - start) >> PAGE_SHIFT, 0))
540                 return -EFAULT;
541
542         hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
543
544         /* Skip this vma and continue processing the next vma. */
545         return 1;
546 }
547
548 static const struct mm_walk_ops hmm_walk_ops = {
549         .pud_entry      = hmm_vma_walk_pud,
550         .pmd_entry      = hmm_vma_walk_pmd,
551         .pte_hole       = hmm_vma_walk_hole,
552         .hugetlb_entry  = hmm_vma_walk_hugetlb_entry,
553         .test_walk      = hmm_vma_walk_test,
554 };
555
556 /**
557  * hmm_range_fault - try to fault some address in a virtual address range
558  * @range:      argument structure
559  *
560  * Returns 0 on success or one of the following error codes:
561  *
562  * -EINVAL:     Invalid arguments or mm or virtual address is in an invalid vma
563  *              (e.g., device file vma).
564  * -ENOMEM:     Out of memory.
565  * -EPERM:      Invalid permission (e.g., asking for write and range is read
566  *              only).
567  * -EBUSY:      The range has been invalidated and the caller needs to wait for
568  *              the invalidation to finish.
569  * -EFAULT:     A page was requested to be valid and could not be made valid
570  *              ie it has no backing VMA or it is illegal to access
571  *
572  * This is similar to get_user_pages(), except that it can read the page tables
573  * without mutating them (ie causing faults).
574  */
575 int hmm_range_fault(struct hmm_range *range)
576 {
577         struct hmm_vma_walk hmm_vma_walk = {
578                 .range = range,
579                 .last = range->start,
580         };
581         struct mm_struct *mm = range->notifier->mm;
582         int ret;
583
584         mmap_assert_locked(mm);
585
586         do {
587                 /* If range is no longer valid force retry. */
588                 if (mmu_interval_check_retry(range->notifier,
589                                              range->notifier_seq))
590                         return -EBUSY;
591                 ret = walk_page_range(mm, hmm_vma_walk.last, range->end,
592                                       &hmm_walk_ops, &hmm_vma_walk);
593                 /*
594                  * When -EBUSY is returned the loop restarts with
595                  * hmm_vma_walk.last set to an address that has not been stored
596                  * in pfns. All entries < last in the pfn array are set to their
597                  * output, and all >= are still at their input values.
598                  */
599         } while (ret == -EBUSY);
600         return ret;
601 }
602 EXPORT_SYMBOL(hmm_range_fault);