arch/s390/mm/pgalloc.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  Page table allocation functions
   4  *
   5  *    Copyright IBM Corp. 2016
   6  *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
   7  */
   8
   9 #include <linux/sysctl.h>
  10 #include <linux/slab.h>
  11 #include <linux/mm.h>
  12 #include <asm/mmu_context.h>
  13 #include <asm/pgalloc.h>
  14 #include <asm/gmap.h>
  15 #include <asm/tlb.h>
  16 #include <asm/tlbflush.h>
  17
  18 #ifdef CONFIG_PGSTE
  19
  20 int page_table_allocate_pgste = 0;
  21 EXPORT_SYMBOL(page_table_allocate_pgste);
  22
  23 static struct ctl_table page_table_sysctl[] = {
  24         {
  25                 .procname       = "allocate_pgste",
  26                 .data           = &page_table_allocate_pgste,
  27                 .maxlen         = sizeof(int),
  28                 .mode           = S_IRUGO | S_IWUSR,
  29                 .proc_handler   = proc_dointvec_minmax,
  30                 .extra1         = SYSCTL_ZERO,
  31                 .extra2         = SYSCTL_ONE,
  32         },
  33         { }
  34 };
  35
  36 static struct ctl_table page_table_sysctl_dir[] = {
  37         {
  38                 .procname       = "vm",
  39                 .maxlen         = 0,
  40                 .mode           = 0555,
  41                 .child          = page_table_sysctl,
  42         },
  43         { }
  44 };
  45
  46 static int __init page_table_register_sysctl(void)
  47 {
  48         return register_sysctl_table(page_table_sysctl_dir) ? 0 : -ENOMEM;
  49 }
  50 __initcall(page_table_register_sysctl);
  51
  52 #endif /* CONFIG_PGSTE */
  53
  54 unsigned long *crst_table_alloc(struct mm_struct *mm)
  55 {
  56         struct page *page = alloc_pages(GFP_KERNEL, 2);
  57
  58         if (!page)
  59                 return NULL;
  60         arch_set_page_dat(page, 2);
  61         return (unsigned long *) page_to_phys(page);
  62 }
  63
  64 void crst_table_free(struct mm_struct *mm, unsigned long *table)
  65 {
  66         free_pages((unsigned long) table, 2);
  67 }
  68
  69 static void __crst_table_upgrade(void *arg)
  70 {
  71         struct mm_struct *mm = arg;
  72
  73         /* change all active ASCEs to avoid the creation of new TLBs */
  74         if (current->active_mm == mm) {
  75                 S390_lowcore.user_asce = mm->context.asce;
  76                 __ctl_load(S390_lowcore.user_asce, 7, 7);
  77         }
  78         __tlb_flush_local();
  79 }
  80
  81 int crst_table_upgrade(struct mm_struct *mm, unsigned long end)
  82 {
  83         unsigned long *pgd = NULL, *p4d = NULL, *__pgd;
  84         unsigned long asce_limit = mm->context.asce_limit;
  85
  86         /* upgrade should only happen from 3 to 4, 3 to 5, or 4 to 5 levels */
  87         VM_BUG_ON(asce_limit < _REGION2_SIZE);
  88
  89         if (end <= asce_limit)
  90                 return 0;
  91
  92         if (asce_limit == _REGION2_SIZE) {
  93                 p4d = crst_table_alloc(mm);
  94                 if (unlikely(!p4d))
  95                         goto err_p4d;
  96                 crst_table_init(p4d, _REGION2_ENTRY_EMPTY);
  97         }
  98         if (end > _REGION1_SIZE) {
  99                 pgd = crst_table_alloc(mm);
 100                 if (unlikely(!pgd))
 101                         goto err_pgd;
 102                 crst_table_init(pgd, _REGION1_ENTRY_EMPTY);
 103         }
 104
 105         spin_lock_bh(&mm->page_table_lock);
 106
 107         /*
 108          * This routine gets called with mmap_lock lock held and there is
 109          * no reason to optimize for the case of otherwise. However, if
 110          * that would ever change, the below check will let us know.
 111          */
 112         VM_BUG_ON(asce_limit != mm->context.asce_limit);
 113
 114         if (p4d) {
 115                 __pgd = (unsigned long *) mm->pgd;
 116                 p4d_populate(mm, (p4d_t *) p4d, (pud_t *) __pgd);
 117                 mm->pgd = (pgd_t *) p4d;
 118                 mm->context.asce_limit = _REGION1_SIZE;
 119                 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 120                         _ASCE_USER_BITS | _ASCE_TYPE_REGION2;
 121                 mm_inc_nr_puds(mm);
 122         }
 123         if (pgd) {
 124                 __pgd = (unsigned long *) mm->pgd;
 125                 pgd_populate(mm, (pgd_t *) pgd, (p4d_t *) __pgd);
 126                 mm->pgd = (pgd_t *) pgd;
 127                 mm->context.asce_limit = TASK_SIZE_MAX;
 128                 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 129                         _ASCE_USER_BITS | _ASCE_TYPE_REGION1;
 130         }
 131
 132         spin_unlock_bh(&mm->page_table_lock);
 133
 134         on_each_cpu(__crst_table_upgrade, mm, 0);
 135
 136         return 0;
 137
 138 err_pgd:
 139         crst_table_free(mm, p4d);
 140 err_p4d:
 141         return -ENOMEM;
 142 }
 143
 144 static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
 145 {
 146         unsigned int old, new;
 147
 148         do {
 149                 old = atomic_read(v);
 150                 new = old ^ bits;
 151         } while (atomic_cmpxchg(v, old, new) != old);
 152         return new;
 153 }
 154
 155 #ifdef CONFIG_PGSTE
 156
 157 struct page *page_table_alloc_pgste(struct mm_struct *mm)
 158 {
 159         struct page *page;
 160         u64 *table;
 161
 162         page = alloc_page(GFP_KERNEL);
 163         if (page) {
 164                 table = (u64 *)page_to_phys(page);
 165                 memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
 166                 memset64(table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
 167         }
 168         return page;
 169 }
 170
 171 void page_table_free_pgste(struct page *page)
 172 {
 173         __free_page(page);
 174 }
 175
 176 #endif /* CONFIG_PGSTE */
 177
 178 /*
 179  * page table entry allocation/free routines.
 180  */
 181 unsigned long *page_table_alloc(struct mm_struct *mm)
 182 {
 183         unsigned long *table;
 184         struct page *page;
 185         unsigned int mask, bit;
 186
 187         /* Try to get a fragment of a 4K page as a 2K page table */
 188         if (!mm_alloc_pgste(mm)) {
 189                 table = NULL;
 190                 spin_lock_bh(&mm->context.lock);
 191                 if (!list_empty(&mm->context.pgtable_list)) {
 192                         page = list_first_entry(&mm->context.pgtable_list,
 193                                                 struct page, lru);
 194                         mask = atomic_read(&page->_refcount) >> 24;
 195                         mask = (mask | (mask >> 4)) & 3;
 196                         if (mask != 3) {
 197                                 table = (unsigned long *) page_to_phys(page);
 198                                 bit = mask & 1;         /* =1 -> second 2K */
 199                                 if (bit)
 200                                         table += PTRS_PER_PTE;
 201                                 atomic_xor_bits(&page->_refcount,
 202                                                         1U << (bit + 24));
 203                                 list_del(&page->lru);
 204                         }
 205                 }
 206                 spin_unlock_bh(&mm->context.lock);
 207                 if (table)
 208                         return table;
 209         }
 210         /* Allocate a fresh page */
 211         page = alloc_page(GFP_KERNEL);
 212         if (!page)
 213                 return NULL;
 214         if (!pgtable_pte_page_ctor(page)) {
 215                 __free_page(page);
 216                 return NULL;
 217         }
 218         arch_set_page_dat(page, 0);
 219         /* Initialize page table */
 220         table = (unsigned long *) page_to_phys(page);
 221         if (mm_alloc_pgste(mm)) {
 222                 /* Return 4K page table with PGSTEs */
 223                 atomic_xor_bits(&page->_refcount, 3 << 24);
 224                 memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
 225                 memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
 226         } else {
 227                 /* Return the first 2K fragment of the page */
 228                 atomic_xor_bits(&page->_refcount, 1 << 24);
 229                 memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE);
 230                 spin_lock_bh(&mm->context.lock);
 231                 list_add(&page->lru, &mm->context.pgtable_list);
 232                 spin_unlock_bh(&mm->context.lock);
 233         }
 234         return table;
 235 }
 236
 237 void page_table_free(struct mm_struct *mm, unsigned long *table)
 238 {
 239         struct page *page;
 240         unsigned int bit, mask;
 241
 242         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 243         if (!mm_alloc_pgste(mm)) {
 244                 /* Free 2K page table fragment of a 4K page */
 245                 bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
 246                 spin_lock_bh(&mm->context.lock);
 247                 mask = atomic_xor_bits(&page->_refcount, 1U << (bit + 24));
 248                 mask >>= 24;
 249                 if (mask & 3)
 250                         list_add(&page->lru, &mm->context.pgtable_list);
 251                 else
 252                         list_del(&page->lru);
 253                 spin_unlock_bh(&mm->context.lock);
 254                 if (mask != 0)
 255                         return;
 256         } else {
 257                 atomic_xor_bits(&page->_refcount, 3U << 24);
 258         }
 259
 260         pgtable_pte_page_dtor(page);
 261         __free_page(page);
 262 }
 263
 264 void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
 265                          unsigned long vmaddr)
 266 {
 267         struct mm_struct *mm;
 268         struct page *page;
 269         unsigned int bit, mask;
 270
 271         mm = tlb->mm;
 272         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 273         if (mm_alloc_pgste(mm)) {
 274                 gmap_unlink(mm, table, vmaddr);
 275                 table = (unsigned long *) (__pa(table) | 3);
 276                 tlb_remove_table(tlb, table);
 277                 return;
 278         }
 279         bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
 280         spin_lock_bh(&mm->context.lock);
 281         mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
 282         mask >>= 24;
 283         if (mask & 3)
 284                 list_add_tail(&page->lru, &mm->context.pgtable_list);
 285         else
 286                 list_del(&page->lru);
 287         spin_unlock_bh(&mm->context.lock);
 288         table = (unsigned long *) (__pa(table) | (1U << bit));
 289         tlb_remove_table(tlb, table);
 290 }
 291
 292 void __tlb_remove_table(void *_table)
 293 {
 294         unsigned int mask = (unsigned long) _table & 3;
 295         void *table = (void *)((unsigned long) _table ^ mask);
 296         struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 297
 298         switch (mask) {
 299         case 0:         /* pmd, pud, or p4d */
 300                 free_pages((unsigned long) table, 2);
 301                 break;
 302         case 1:         /* lower 2K of a 4K page table */
 303         case 2:         /* higher 2K of a 4K page table */
 304                 mask = atomic_xor_bits(&page->_refcount, mask << (4 + 24));
 305                 mask >>= 24;
 306                 if (mask != 0)
 307                         break;
 308                 fallthrough;
 309         case 3:         /* 4K page table with pgstes */
 310                 if (mask & 3)
 311                         atomic_xor_bits(&page->_refcount, 3 << 24);
 312                 pgtable_pte_page_dtor(page);
 313                 __free_page(page);
 314                 break;
 315         }
 316 }
 317
 318 /*
 319  * Base infrastructure required to generate basic asces, region, segment,
 320  * and page tables that do not make use of enhanced features like EDAT1.
 321  */
 322
 323 static struct kmem_cache *base_pgt_cache;
 324
 325 static unsigned long base_pgt_alloc(void)
 326 {
 327         u64 *table;
 328
 329         table = kmem_cache_alloc(base_pgt_cache, GFP_KERNEL);
 330         if (table)
 331                 memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
 332         return (unsigned long) table;
 333 }
 334
 335 static void base_pgt_free(unsigned long table)
 336 {
 337         kmem_cache_free(base_pgt_cache, (void *) table);
 338 }
 339
 340 static unsigned long base_crst_alloc(unsigned long val)
 341 {
 342         unsigned long table;
 343
 344         table =  __get_free_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
 345         if (table)
 346                 crst_table_init((unsigned long *)table, val);
 347         return table;
 348 }
 349
 350 static void base_crst_free(unsigned long table)
 351 {
 352         free_pages(table, CRST_ALLOC_ORDER);
 353 }
 354
 355 #define BASE_ADDR_END_FUNC(NAME, SIZE)                                  \
 356 static inline unsigned long base_##NAME##_addr_end(unsigned long addr,  \
 357                                                    unsigned long end)   \
 358 {                                                                       \
 359         unsigned long next = (addr + (SIZE)) & ~((SIZE) - 1);           \
 360                                                                         \
 361         return (next - 1) < (end - 1) ? next : end;                     \
 362 }
 363
 364 BASE_ADDR_END_FUNC(page,    _PAGE_SIZE)
 365 BASE_ADDR_END_FUNC(segment, _SEGMENT_SIZE)
 366 BASE_ADDR_END_FUNC(region3, _REGION3_SIZE)
 367 BASE_ADDR_END_FUNC(region2, _REGION2_SIZE)
 368 BASE_ADDR_END_FUNC(region1, _REGION1_SIZE)
 369
 370 static inline unsigned long base_lra(unsigned long address)
 371 {
 372         unsigned long real;
 373
 374         asm volatile(
 375                 "       lra     %0,0(%1)\n"
 376                 : "=d" (real) : "a" (address) : "cc");
 377         return real;
 378 }
 379
 380 static int base_page_walk(unsigned long origin, unsigned long addr,
 381                           unsigned long end, int alloc)
 382 {
 383         unsigned long *pte, next;
 384
 385         if (!alloc)
 386                 return 0;
 387         pte = (unsigned long *) origin;
 388         pte += (addr & _PAGE_INDEX) >> _PAGE_SHIFT;
 389         do {
 390                 next = base_page_addr_end(addr, end);
 391                 *pte = base_lra(addr);
 392         } while (pte++, addr = next, addr < end);
 393         return 0;
 394 }
 395
 396 static int base_segment_walk(unsigned long origin, unsigned long addr,
 397                              unsigned long end, int alloc)
 398 {
 399         unsigned long *ste, next, table;
 400         int rc;
 401
 402         ste = (unsigned long *) origin;
 403         ste += (addr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
 404         do {
 405                 next = base_segment_addr_end(addr, end);
 406                 if (*ste & _SEGMENT_ENTRY_INVALID) {
 407                         if (!alloc)
 408                                 continue;
 409                         table = base_pgt_alloc();
 410                         if (!table)
 411                                 return -ENOMEM;
 412                         *ste = table | _SEGMENT_ENTRY;
 413                 }
 414                 table = *ste & _SEGMENT_ENTRY_ORIGIN;
 415                 rc = base_page_walk(table, addr, next, alloc);
 416                 if (rc)
 417                         return rc;
 418                 if (!alloc)
 419                         base_pgt_free(table);
 420                 cond_resched();
 421         } while (ste++, addr = next, addr < end);
 422         return 0;
 423 }
 424
 425 static int base_region3_walk(unsigned long origin, unsigned long addr,
 426                              unsigned long end, int alloc)
 427 {
 428         unsigned long *rtte, next, table;
 429         int rc;
 430
 431         rtte = (unsigned long *) origin;
 432         rtte += (addr & _REGION3_INDEX) >> _REGION3_SHIFT;
 433         do {
 434                 next = base_region3_addr_end(addr, end);
 435                 if (*rtte & _REGION_ENTRY_INVALID) {
 436                         if (!alloc)
 437                                 continue;
 438                         table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
 439                         if (!table)
 440                                 return -ENOMEM;
 441                         *rtte = table | _REGION3_ENTRY;
 442                 }
 443                 table = *rtte & _REGION_ENTRY_ORIGIN;
 444                 rc = base_segment_walk(table, addr, next, alloc);
 445                 if (rc)
 446                         return rc;
 447                 if (!alloc)
 448                         base_crst_free(table);
 449         } while (rtte++, addr = next, addr < end);
 450         return 0;
 451 }
 452
 453 static int base_region2_walk(unsigned long origin, unsigned long addr,
 454                              unsigned long end, int alloc)
 455 {
 456         unsigned long *rste, next, table;
 457         int rc;
 458
 459         rste = (unsigned long *) origin;
 460         rste += (addr & _REGION2_INDEX) >> _REGION2_SHIFT;
 461         do {
 462                 next = base_region2_addr_end(addr, end);
 463                 if (*rste & _REGION_ENTRY_INVALID) {
 464                         if (!alloc)
 465                                 continue;
 466                         table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
 467                         if (!table)
 468                                 return -ENOMEM;
 469                         *rste = table | _REGION2_ENTRY;
 470                 }
 471                 table = *rste & _REGION_ENTRY_ORIGIN;
 472                 rc = base_region3_walk(table, addr, next, alloc);
 473                 if (rc)
 474                         return rc;
 475                 if (!alloc)
 476                         base_crst_free(table);
 477         } while (rste++, addr = next, addr < end);
 478         return 0;
 479 }
 480
 481 static int base_region1_walk(unsigned long origin, unsigned long addr,
 482                              unsigned long end, int alloc)
 483 {
 484         unsigned long *rfte, next, table;
 485         int rc;
 486
 487         rfte = (unsigned long *) origin;
 488         rfte += (addr & _REGION1_INDEX) >> _REGION1_SHIFT;
 489         do {
 490                 next = base_region1_addr_end(addr, end);
 491                 if (*rfte & _REGION_ENTRY_INVALID) {
 492                         if (!alloc)
 493                                 continue;
 494                         table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
 495                         if (!table)
 496                                 return -ENOMEM;
 497                         *rfte = table | _REGION1_ENTRY;
 498                 }
 499                 table = *rfte & _REGION_ENTRY_ORIGIN;
 500                 rc = base_region2_walk(table, addr, next, alloc);
 501                 if (rc)
 502                         return rc;
 503                 if (!alloc)
 504                         base_crst_free(table);
 505         } while (rfte++, addr = next, addr < end);
 506         return 0;
 507 }
 508
 509 /**
 510  * base_asce_free - free asce and tables returned from base_asce_alloc()
 511  * @asce: asce to be freed
 512  *
 513  * Frees all region, segment, and page tables that were allocated with a
 514  * corresponding base_asce_alloc() call.
 515  */
 516 void base_asce_free(unsigned long asce)
 517 {
 518         unsigned long table = asce & _ASCE_ORIGIN;
 519
 520         if (!asce)
 521                 return;
 522         switch (asce & _ASCE_TYPE_MASK) {
 523         case _ASCE_TYPE_SEGMENT:
 524                 base_segment_walk(table, 0, _REGION3_SIZE, 0);
 525                 break;
 526         case _ASCE_TYPE_REGION3:
 527                 base_region3_walk(table, 0, _REGION2_SIZE, 0);
 528                 break;
 529         case _ASCE_TYPE_REGION2:
 530                 base_region2_walk(table, 0, _REGION1_SIZE, 0);
 531                 break;
 532         case _ASCE_TYPE_REGION1:
 533                 base_region1_walk(table, 0, TASK_SIZE_MAX, 0);
 534                 break;
 535         }
 536         base_crst_free(table);
 537 }
 538
 539 static int base_pgt_cache_init(void)
 540 {
 541         static DEFINE_MUTEX(base_pgt_cache_mutex);
 542         unsigned long sz = _PAGE_TABLE_SIZE;
 543
 544         if (base_pgt_cache)
 545                 return 0;
 546         mutex_lock(&base_pgt_cache_mutex);
 547         if (!base_pgt_cache)
 548                 base_pgt_cache = kmem_cache_create("base_pgt", sz, sz, 0, NULL);
 549         mutex_unlock(&base_pgt_cache_mutex);
 550         return base_pgt_cache ? 0 : -ENOMEM;
 551 }
 552
 553 /**
 554  * base_asce_alloc - create kernel mapping without enhanced DAT features
 555  * @addr: virtual start address of kernel mapping
 556  * @num_pages: number of consecutive pages
 557  *
 558  * Generate an asce, including all required region, segment and page tables,
 559  * that can be used to access the virtual kernel mapping. The difference is
 560  * that the returned asce does not make use of any enhanced DAT features like
 561  * e.g. large pages. This is required for some I/O functions that pass an
 562  * asce, like e.g. some service call requests.
 563  *
 564  * Note: the returned asce may NEVER be attached to any cpu. It may only be
 565  *       used for I/O requests. tlb entries that might result because the
 566  *       asce was attached to a cpu won't be cleared.
 567  */
 568 unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages)
 569 {
 570         unsigned long asce, table, end;
 571         int rc;
 572
 573         if (base_pgt_cache_init())
 574                 return 0;
 575         end = addr + num_pages * PAGE_SIZE;
 576         if (end <= _REGION3_SIZE) {
 577                 table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
 578                 if (!table)
 579                         return 0;
 580                 rc = base_segment_walk(table, addr, end, 1);
 581                 asce = table | _ASCE_TYPE_SEGMENT | _ASCE_TABLE_LENGTH;
 582         } else if (end <= _REGION2_SIZE) {
 583                 table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
 584                 if (!table)
 585                         return 0;
 586                 rc = base_region3_walk(table, addr, end, 1);
 587                 asce = table | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
 588         } else if (end <= _REGION1_SIZE) {
 589                 table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
 590                 if (!table)
 591                         return 0;
 592                 rc = base_region2_walk(table, addr, end, 1);
 593                 asce = table | _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
 594         } else {
 595                 table = base_crst_alloc(_REGION1_ENTRY_EMPTY);
 596                 if (!table)
 597                         return 0;
 598                 rc = base_region1_walk(table, addr, end, 1);
 599                 asce = table | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
 600         }
 601         if (rc) {
 602                 base_asce_free(asce);
 603                 asce = 0;
 604         }
 605         return asce;
 606 }