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 static int page_table_allocate_pgste_min = 0;
  21 static int page_table_allocate_pgste_max = 1;
  22 int page_table_allocate_pgste = 0;
  23 EXPORT_SYMBOL(page_table_allocate_pgste);
  24
  25 static struct ctl_table page_table_sysctl[] = {
  26         {
  27                 .procname       = "allocate_pgste",
  28                 .data           = &page_table_allocate_pgste,
  29                 .maxlen         = sizeof(int),
  30                 .mode           = S_IRUGO | S_IWUSR,
  31                 .proc_handler   = proc_dointvec_minmax,
  32                 .extra1         = &page_table_allocate_pgste_min,
  33                 .extra2         = &page_table_allocate_pgste_max,
  34         },
  35         { }
  36 };
  37
  38 static struct ctl_table page_table_sysctl_dir[] = {
  39         {
  40                 .procname       = "vm",
  41                 .maxlen         = 0,
  42                 .mode           = 0555,
  43                 .child          = page_table_sysctl,
  44         },
  45         { }
  46 };
  47
  48 static int __init page_table_register_sysctl(void)
  49 {
  50         return register_sysctl_table(page_table_sysctl_dir) ? 0 : -ENOMEM;
  51 }
  52 __initcall(page_table_register_sysctl);
  53
  54 #endif /* CONFIG_PGSTE */
  55
  56 unsigned long *crst_table_alloc(struct mm_struct *mm)
  57 {
  58         struct page *page = alloc_pages(GFP_KERNEL, 2);
  59
  60         if (!page)
  61                 return NULL;
  62         arch_set_page_dat(page, 2);
  63         return (unsigned long *) page_to_phys(page);
  64 }
  65
  66 void crst_table_free(struct mm_struct *mm, unsigned long *table)
  67 {
  68         free_pages((unsigned long) table, 2);
  69 }
  70
  71 static void __crst_table_upgrade(void *arg)
  72 {
  73         struct mm_struct *mm = arg;
  74
  75         if (current->active_mm == mm)
  76                 set_user_asce(mm);
  77         __tlb_flush_local();
  78 }
  79
  80 int crst_table_upgrade(struct mm_struct *mm, unsigned long end)
  81 {
  82         unsigned long *table, *pgd;
  83         int rc, notify;
  84
  85         /* upgrade should only happen from 3 to 4, 3 to 5, or 4 to 5 levels */
  86         VM_BUG_ON(mm->context.asce_limit < _REGION2_SIZE);
  87         rc = 0;
  88         notify = 0;
  89         while (mm->context.asce_limit < end) {
  90                 table = crst_table_alloc(mm);
  91                 if (!table) {
  92                         rc = -ENOMEM;
  93                         break;
  94                 }
  95                 spin_lock_bh(&mm->page_table_lock);
  96                 pgd = (unsigned long *) mm->pgd;
  97                 if (mm->context.asce_limit == _REGION2_SIZE) {
  98                         crst_table_init(table, _REGION2_ENTRY_EMPTY);
  99                         p4d_populate(mm, (p4d_t *) table, (pud_t *) pgd);
 100                         mm->pgd = (pgd_t *) table;
 101                         mm->context.asce_limit = _REGION1_SIZE;
 102                         mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 103                                 _ASCE_USER_BITS | _ASCE_TYPE_REGION2;
 104                         mm_inc_nr_puds(mm);
 105                 } else {
 106                         crst_table_init(table, _REGION1_ENTRY_EMPTY);
 107                         pgd_populate(mm, (pgd_t *) table, (p4d_t *) pgd);
 108                         mm->pgd = (pgd_t *) table;
 109                         mm->context.asce_limit = -PAGE_SIZE;
 110                         mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 111                                 _ASCE_USER_BITS | _ASCE_TYPE_REGION1;
 112                 }
 113                 notify = 1;
 114                 spin_unlock_bh(&mm->page_table_lock);
 115         }
 116         if (notify)
 117                 on_each_cpu(__crst_table_upgrade, mm, 0);
 118         return rc;
 119 }
 120
 121 void crst_table_downgrade(struct mm_struct *mm)
 122 {
 123         pgd_t *pgd;
 124
 125         /* downgrade should only happen from 3 to 2 levels (compat only) */
 126         VM_BUG_ON(mm->context.asce_limit != _REGION2_SIZE);
 127
 128         if (current->active_mm == mm) {
 129                 clear_user_asce();
 130                 __tlb_flush_mm(mm);
 131         }
 132
 133         pgd = mm->pgd;
 134         mm_dec_nr_pmds(mm);
 135         mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN);
 136         mm->context.asce_limit = _REGION3_SIZE;
 137         mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 138                            _ASCE_USER_BITS | _ASCE_TYPE_SEGMENT;
 139         crst_table_free(mm, (unsigned long *) pgd);
 140
 141         if (current->active_mm == mm)
 142                 set_user_asce(mm);
 143 }
 144
 145 static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
 146 {
 147         unsigned int old, new;
 148
 149         do {
 150                 old = atomic_read(v);
 151                 new = old ^ bits;
 152         } while (atomic_cmpxchg(v, old, new) != old);
 153         return new;
 154 }
 155
 156 #ifdef CONFIG_PGSTE
 157
 158 struct page *page_table_alloc_pgste(struct mm_struct *mm)
 159 {
 160         struct page *page;
 161         u64 *table;
 162
 163         page = alloc_page(GFP_KERNEL);
 164         if (page) {
 165                 table = (u64 *)page_to_phys(page);
 166                 memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
 167                 memset64(table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
 168         }
 169         return page;
 170 }
 171
 172 void page_table_free_pgste(struct page *page)
 173 {
 174         __free_page(page);
 175 }
 176
 177 #endif /* CONFIG_PGSTE */
 178
 179 /*
 180  * page table entry allocation/free routines.
 181  */
 182 unsigned long *page_table_alloc(struct mm_struct *mm)
 183 {
 184         unsigned long *table;
 185         struct page *page;
 186         unsigned int mask, bit;
 187
 188         /* Try to get a fragment of a 4K page as a 2K page table */
 189         if (!mm_alloc_pgste(mm)) {
 190                 table = NULL;
 191                 spin_lock_bh(&mm->context.lock);
 192                 if (!list_empty(&mm->context.pgtable_list)) {
 193                         page = list_first_entry(&mm->context.pgtable_list,
 194                                                 struct page, lru);
 195                         mask = atomic_read(&page->_refcount) >> 24;
 196                         mask = (mask | (mask >> 4)) & 3;
 197                         if (mask != 3) {
 198                                 table = (unsigned long *) page_to_phys(page);
 199                                 bit = mask & 1;         /* =1 -> second 2K */
 200                                 if (bit)
 201                                         table += PTRS_PER_PTE;
 202                                 atomic_xor_bits(&page->_refcount,
 203                                                         1U << (bit + 24));
 204                                 list_del(&page->lru);
 205                         }
 206                 }
 207                 spin_unlock_bh(&mm->context.lock);
 208                 if (table)
 209                         return table;
 210         }
 211         /* Allocate a fresh page */
 212         page = alloc_page(GFP_KERNEL);
 213         if (!page)
 214                 return NULL;
 215         if (!pgtable_page_ctor(page)) {
 216                 __free_page(page);
 217                 return NULL;
 218         }
 219         arch_set_page_dat(page, 0);
 220         /* Initialize page table */
 221         table = (unsigned long *) page_to_phys(page);
 222         if (mm_alloc_pgste(mm)) {
 223                 /* Return 4K page table with PGSTEs */
 224                 atomic_xor_bits(&page->_refcount, 3 << 24);
 225                 memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
 226                 memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
 227         } else {
 228                 /* Return the first 2K fragment of the page */
 229                 atomic_xor_bits(&page->_refcount, 1 << 24);
 230                 memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE);
 231                 spin_lock_bh(&mm->context.lock);
 232                 list_add(&page->lru, &mm->context.pgtable_list);
 233                 spin_unlock_bh(&mm->context.lock);
 234         }
 235         return table;
 236 }
 237
 238 void page_table_free(struct mm_struct *mm, unsigned long *table)
 239 {
 240         struct page *page;
 241         unsigned int bit, mask;
 242
 243         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 244         if (!mm_alloc_pgste(mm)) {
 245                 /* Free 2K page table fragment of a 4K page */
 246                 bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
 247                 spin_lock_bh(&mm->context.lock);
 248                 mask = atomic_xor_bits(&page->_refcount, 1U << (bit + 24));
 249                 mask >>= 24;
 250                 if (mask & 3)
 251                         list_add(&page->lru, &mm->context.pgtable_list);
 252                 else
 253                         list_del(&page->lru);
 254                 spin_unlock_bh(&mm->context.lock);
 255                 if (mask != 0)
 256                         return;
 257         } else {
 258                 atomic_xor_bits(&page->_refcount, 3U << 24);
 259         }
 260
 261         pgtable_page_dtor(page);
 262         __free_page(page);
 263 }
 264
 265 void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
 266                          unsigned long vmaddr)
 267 {
 268         struct mm_struct *mm;
 269         struct page *page;
 270         unsigned int bit, mask;
 271
 272         mm = tlb->mm;
 273         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 274         if (mm_alloc_pgste(mm)) {
 275                 gmap_unlink(mm, table, vmaddr);
 276                 table = (unsigned long *) (__pa(table) | 3);
 277                 tlb_remove_table(tlb, table);
 278                 return;
 279         }
 280         bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
 281         spin_lock_bh(&mm->context.lock);
 282         mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
 283         mask >>= 24;
 284         if (mask & 3)
 285                 list_add_tail(&page->lru, &mm->context.pgtable_list);
 286         else
 287                 list_del(&page->lru);
 288         spin_unlock_bh(&mm->context.lock);
 289         table = (unsigned long *) (__pa(table) | (1U << bit));
 290         tlb_remove_table(tlb, table);
 291 }
 292
 293 void __tlb_remove_table(void *_table)
 294 {
 295         unsigned int mask = (unsigned long) _table & 3;
 296         void *table = (void *)((unsigned long) _table ^ mask);
 297         struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 298
 299         switch (mask) {
 300         case 0:         /* pmd, pud, or p4d */
 301                 free_pages((unsigned long) table, 2);
 302                 break;
 303         case 1:         /* lower 2K of a 4K page table */
 304         case 2:         /* higher 2K of a 4K page table */
 305                 mask = atomic_xor_bits(&page->_refcount, mask << (4 + 24));
 306                 mask >>= 24;
 307                 if (mask != 0)
 308                         break;
 309                 /* fallthrough */
 310         case 3:         /* 4K page table with pgstes */
 311                 if (mask & 3)
 312                         atomic_xor_bits(&page->_refcount, 3 << 24);
 313                 pgtable_page_dtor(page);
 314                 __free_page(page);
 315                 break;
 316         }
 317 }
 318
 319 /*
 320  * Base infrastructure required to generate basic asces, region, segment,
 321  * and page tables that do not make use of enhanced features like EDAT1.
 322  */
 323
 324 static struct kmem_cache *base_pgt_cache;
 325
 326 static unsigned long base_pgt_alloc(void)
 327 {
 328         u64 *table;
 329
 330         table = kmem_cache_alloc(base_pgt_cache, GFP_KERNEL);
 331         if (table)
 332                 memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
 333         return (unsigned long) table;
 334 }
 335
 336 static void base_pgt_free(unsigned long table)
 337 {
 338         kmem_cache_free(base_pgt_cache, (void *) table);
 339 }
 340
 341 static unsigned long base_crst_alloc(unsigned long val)
 342 {
 343         unsigned long table;
 344
 345         table =  __get_free_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
 346         if (table)
 347                 crst_table_init((unsigned long *)table, val);
 348         return table;
 349 }
 350
 351 static void base_crst_free(unsigned long table)
 352 {
 353         free_pages(table, CRST_ALLOC_ORDER);
 354 }
 355
 356 #define BASE_ADDR_END_FUNC(NAME, SIZE)                                  \
 357 static inline unsigned long base_##NAME##_addr_end(unsigned long addr,  \
 358                                                    unsigned long end)   \
 359 {                                                                       \
 360         unsigned long next = (addr + (SIZE)) & ~((SIZE) - 1);           \
 361                                                                         \
 362         return (next - 1) < (end - 1) ? next : end;                     \
 363 }
 364
 365 BASE_ADDR_END_FUNC(page,    _PAGE_SIZE)
 366 BASE_ADDR_END_FUNC(segment, _SEGMENT_SIZE)
 367 BASE_ADDR_END_FUNC(region3, _REGION3_SIZE)
 368 BASE_ADDR_END_FUNC(region2, _REGION2_SIZE)
 369 BASE_ADDR_END_FUNC(region1, _REGION1_SIZE)
 370
 371 static inline unsigned long base_lra(unsigned long address)
 372 {
 373         unsigned long real;
 374
 375         asm volatile(
 376                 "       lra     %0,0(%1)\n"
 377                 : "=d" (real) : "a" (address) : "cc");
 378         return real;
 379 }
 380
 381 static int base_page_walk(unsigned long origin, unsigned long addr,
 382                           unsigned long end, int alloc)
 383 {
 384         unsigned long *pte, next;
 385
 386         if (!alloc)
 387                 return 0;
 388         pte = (unsigned long *) origin;
 389         pte += (addr & _PAGE_INDEX) >> _PAGE_SHIFT;
 390         do {
 391                 next = base_page_addr_end(addr, end);
 392                 *pte = base_lra(addr);
 393         } while (pte++, addr = next, addr < end);
 394         return 0;
 395 }
 396
 397 static int base_segment_walk(unsigned long origin, unsigned long addr,
 398                              unsigned long end, int alloc)
 399 {
 400         unsigned long *ste, next, table;
 401         int rc;
 402
 403         ste = (unsigned long *) origin;
 404         ste += (addr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
 405         do {
 406                 next = base_segment_addr_end(addr, end);
 407                 if (*ste & _SEGMENT_ENTRY_INVALID) {
 408                         if (!alloc)
 409                                 continue;
 410                         table = base_pgt_alloc();
 411                         if (!table)
 412                                 return -ENOMEM;
 413                         *ste = table | _SEGMENT_ENTRY;
 414                 }
 415                 table = *ste & _SEGMENT_ENTRY_ORIGIN;
 416                 rc = base_page_walk(table, addr, next, alloc);
 417                 if (rc)
 418                         return rc;
 419                 if (!alloc)
 420                         base_pgt_free(table);
 421                 cond_resched();
 422         } while (ste++, addr = next, addr < end);
 423         return 0;
 424 }
 425
 426 static int base_region3_walk(unsigned long origin, unsigned long addr,
 427                              unsigned long end, int alloc)
 428 {
 429         unsigned long *rtte, next, table;
 430         int rc;
 431
 432         rtte = (unsigned long *) origin;
 433         rtte += (addr & _REGION3_INDEX) >> _REGION3_SHIFT;
 434         do {
 435                 next = base_region3_addr_end(addr, end);
 436                 if (*rtte & _REGION_ENTRY_INVALID) {
 437                         if (!alloc)
 438                                 continue;
 439                         table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
 440                         if (!table)
 441                                 return -ENOMEM;
 442                         *rtte = table | _REGION3_ENTRY;
 443                 }
 444                 table = *rtte & _REGION_ENTRY_ORIGIN;
 445                 rc = base_segment_walk(table, addr, next, alloc);
 446                 if (rc)
 447                         return rc;
 448                 if (!alloc)
 449                         base_crst_free(table);
 450         } while (rtte++, addr = next, addr < end);
 451         return 0;
 452 }
 453
 454 static int base_region2_walk(unsigned long origin, unsigned long addr,
 455                              unsigned long end, int alloc)
 456 {
 457         unsigned long *rste, next, table;
 458         int rc;
 459
 460         rste = (unsigned long *) origin;
 461         rste += (addr & _REGION2_INDEX) >> _REGION2_SHIFT;
 462         do {
 463                 next = base_region2_addr_end(addr, end);
 464                 if (*rste & _REGION_ENTRY_INVALID) {
 465                         if (!alloc)
 466                                 continue;
 467                         table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
 468                         if (!table)
 469                                 return -ENOMEM;
 470                         *rste = table | _REGION2_ENTRY;
 471                 }
 472                 table = *rste & _REGION_ENTRY_ORIGIN;
 473                 rc = base_region3_walk(table, addr, next, alloc);
 474                 if (rc)
 475                         return rc;
 476                 if (!alloc)
 477                         base_crst_free(table);
 478         } while (rste++, addr = next, addr < end);
 479         return 0;
 480 }
 481
 482 static int base_region1_walk(unsigned long origin, unsigned long addr,
 483                              unsigned long end, int alloc)
 484 {
 485         unsigned long *rfte, next, table;
 486         int rc;
 487
 488         rfte = (unsigned long *) origin;
 489         rfte += (addr & _REGION1_INDEX) >> _REGION1_SHIFT;
 490         do {
 491                 next = base_region1_addr_end(addr, end);
 492                 if (*rfte & _REGION_ENTRY_INVALID) {
 493                         if (!alloc)
 494                                 continue;
 495                         table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
 496                         if (!table)
 497                                 return -ENOMEM;
 498                         *rfte = table | _REGION1_ENTRY;
 499                 }
 500                 table = *rfte & _REGION_ENTRY_ORIGIN;
 501                 rc = base_region2_walk(table, addr, next, alloc);
 502                 if (rc)
 503                         return rc;
 504                 if (!alloc)
 505                         base_crst_free(table);
 506         } while (rfte++, addr = next, addr < end);
 507         return 0;
 508 }
 509
 510 /**
 511  * base_asce_free - free asce and tables returned from base_asce_alloc()
 512  * @asce: asce to be freed
 513  *
 514  * Frees all region, segment, and page tables that were allocated with a
 515  * corresponding base_asce_alloc() call.
 516  */
 517 void base_asce_free(unsigned long asce)
 518 {
 519         unsigned long table = asce & _ASCE_ORIGIN;
 520
 521         if (!asce)
 522                 return;
 523         switch (asce & _ASCE_TYPE_MASK) {
 524         case _ASCE_TYPE_SEGMENT:
 525                 base_segment_walk(table, 0, _REGION3_SIZE, 0);
 526                 break;
 527         case _ASCE_TYPE_REGION3:
 528                 base_region3_walk(table, 0, _REGION2_SIZE, 0);
 529                 break;
 530         case _ASCE_TYPE_REGION2:
 531                 base_region2_walk(table, 0, _REGION1_SIZE, 0);
 532                 break;
 533         case _ASCE_TYPE_REGION1:
 534                 base_region1_walk(table, 0, -_PAGE_SIZE, 0);
 535                 break;
 536         }
 537         base_crst_free(table);
 538 }
 539
 540 static int base_pgt_cache_init(void)
 541 {
 542         static DEFINE_MUTEX(base_pgt_cache_mutex);
 543         unsigned long sz = _PAGE_TABLE_SIZE;
 544
 545         if (base_pgt_cache)
 546                 return 0;
 547         mutex_lock(&base_pgt_cache_mutex);
 548         if (!base_pgt_cache)
 549                 base_pgt_cache = kmem_cache_create("base_pgt", sz, sz, 0, NULL);
 550         mutex_unlock(&base_pgt_cache_mutex);
 551         return base_pgt_cache ? 0 : -ENOMEM;
 552 }
 553
 554 /**
 555  * base_asce_alloc - create kernel mapping without enhanced DAT features
 556  * @addr: virtual start address of kernel mapping
 557  * @num_pages: number of consecutive pages
 558  *
 559  * Generate an asce, including all required region, segment and page tables,
 560  * that can be used to access the virtual kernel mapping. The difference is
 561  * that the returned asce does not make use of any enhanced DAT features like
 562  * e.g. large pages. This is required for some I/O functions that pass an
 563  * asce, like e.g. some service call requests.
 564  *
 565  * Note: the returned asce may NEVER be attached to any cpu. It may only be
 566  *       used for I/O requests. tlb entries that might result because the
 567  *       asce was attached to a cpu won't be cleared.
 568  */
 569 unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages)
 570 {
 571         unsigned long asce, table, end;
 572         int rc;
 573
 574         if (base_pgt_cache_init())
 575                 return 0;
 576         end = addr + num_pages * PAGE_SIZE;
 577         if (end <= _REGION3_SIZE) {
 578                 table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
 579                 if (!table)
 580                         return 0;
 581                 rc = base_segment_walk(table, addr, end, 1);
 582                 asce = table | _ASCE_TYPE_SEGMENT | _ASCE_TABLE_LENGTH;
 583         } else if (end <= _REGION2_SIZE) {
 584                 table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
 585                 if (!table)
 586                         return 0;
 587                 rc = base_region3_walk(table, addr, end, 1);
 588                 asce = table | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
 589         } else if (end <= _REGION1_SIZE) {
 590                 table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
 591                 if (!table)
 592                         return 0;
 593                 rc = base_region2_walk(table, addr, end, 1);
 594                 asce = table | _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
 595         } else {
 596                 table = base_crst_alloc(_REGION1_ENTRY_EMPTY);
 597                 if (!table)
 598                         return 0;
 599                 rc = base_region1_walk(table, addr, end, 1);
 600                 asce = table | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
 601         }
 602         if (rc) {
 603                 base_asce_free(asce);
 604                 asce = 0;
 605         }
 606         return asce;
 607 }