1// SPDX-License-Identifier: GPL-2.0-or-later 2/* 3 * Copyright 2013 Red Hat Inc. 4 * 5 * Authors: J��r��me 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 31struct hmm_vma_walk { 32 struct hmm_range *range; 33 unsigned long last; 34}; 35 36enum { 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 42static 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 */ 63static 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 86static 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 120static unsigned int 121hmm_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 147static 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 171static inline unsigned long hmm_pfn_flags_order(unsigned long order) 172{ 173 return order << HMM_PFN_ORDER_SHIFT; 174} 175 176static 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 187static 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 */ 211int 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 215static 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 223static 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 314fault: 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 320static 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 334again: 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) 401static 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 411static 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 464out_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 473static 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 525static 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 559static 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 */ 587int 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} 614EXPORT_SYMBOL(hmm_range_fault); 615