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         /* we must 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                 if (current->thread.mm_segment == USER_DS) {
  77                         __ctl_load(S390_lowcore.user_asce, 1, 1);
  78                         /* Mark user-ASCE present in CR1 */
  79                         clear_cpu_flag(CIF_ASCE_PRIMARY);
  80                 }
  81                 if (current->thread.mm_segment == USER_DS_SACF) {
  82                         __ctl_load(S390_lowcore.user_asce, 7, 7);
  83                         /* enable_sacf_uaccess does all or nothing */
  84                         WARN_ON(!test_cpu_flag(CIF_ASCE_SECONDARY));
  85                 }
  86         }
  87         __tlb_flush_local();
  88 }
  89
  90 int crst_table_upgrade(struct mm_struct *mm, unsigned long end)
  91 {
  92         unsigned long *pgd = NULL, *p4d = NULL, *__pgd;
  93         unsigned long asce_limit = mm->context.asce_limit;
  94
  95         /* upgrade should only happen from 3 to 4, 3 to 5, or 4 to 5 levels */
  96         VM_BUG_ON(asce_limit < _REGION2_SIZE);
  97
  98         if (end <= asce_limit)
  99                 return 0;
 100
 101         if (asce_limit == _REGION2_SIZE) {
 102                 p4d = crst_table_alloc(mm);
 103                 if (unlikely(!p4d))
 104                         goto err_p4d;
 105                 crst_table_init(p4d, _REGION2_ENTRY_EMPTY);
 106         }
 107         if (end > _REGION1_SIZE) {
 108                 pgd = crst_table_alloc(mm);
 109                 if (unlikely(!pgd))
 110                         goto err_pgd;
 111                 crst_table_init(pgd, _REGION1_ENTRY_EMPTY);
 112         }
 113
 114         spin_lock_bh(&mm->page_table_lock);
 115
 116         /*
 117          * This routine gets called with mmap_lock lock held and there is
 118          * no reason to optimize for the case of otherwise. However, if
 119          * that would ever change, the below check will let us know.
 120          */
 121         VM_BUG_ON(asce_limit != mm->context.asce_limit);
 122
 123         if (p4d) {
 124                 __pgd = (unsigned long *) mm->pgd;
 125                 p4d_populate(mm, (p4d_t *) p4d, (pud_t *) __pgd);
 126                 mm->pgd = (pgd_t *) p4d;
 127                 mm->context.asce_limit = _REGION1_SIZE;
 128                 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 129                         _ASCE_USER_BITS | _ASCE_TYPE_REGION2;
 130                 mm_inc_nr_puds(mm);
 131         }
 132         if (pgd) {
 133                 __pgd = (unsigned long *) mm->pgd;
 134                 pgd_populate(mm, (pgd_t *) pgd, (p4d_t *) __pgd);
 135                 mm->pgd = (pgd_t *) pgd;
 136                 mm->context.asce_limit = TASK_SIZE_MAX;
 137                 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 138                         _ASCE_USER_BITS | _ASCE_TYPE_REGION1;
 139         }
 140
 141         spin_unlock_bh(&mm->page_table_lock);
 142
 143         on_each_cpu(__crst_table_upgrade, mm, 0);
 144
 145         return 0;
 146
 147 err_pgd:
 148         crst_table_free(mm, p4d);
 149 err_p4d:
 150         return -ENOMEM;
 151 }
 152
 153 static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
 154 {
 155         unsigned int old, new;
 156
 157         do {
 158                 old = atomic_read(v);
 159                 new = old ^ bits;
 160         } while (atomic_cmpxchg(v, old, new) != old);
 161         return new;
 162 }
 163
 164 #ifdef CONFIG_PGSTE
 165
 166 struct page *page_table_alloc_pgste(struct mm_struct *mm)
 167 {
 168         struct page *page;
 169         u64 *table;
 170
 171         page = alloc_page(GFP_KERNEL);
 172         if (page) {
 173                 table = (u64 *)page_to_phys(page);
 174                 memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
 175                 memset64(table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
 176         }
 177         return page;
 178 }
 179
 180 void page_table_free_pgste(struct page *page)
 181 {
 182         __free_page(page);
 183 }
 184
 185 #endif /* CONFIG_PGSTE */
 186
 187 /*
 188  * page table entry allocation/free routines.
 189  */
 190 unsigned long *page_table_alloc(struct mm_struct *mm)
 191 {
 192         unsigned long *table;
 193         struct page *page;
 194         unsigned int mask, bit;
 195
 196         /* Try to get a fragment of a 4K page as a 2K page table */
 197         if (!mm_alloc_pgste(mm)) {
 198                 table = NULL;
 199                 spin_lock_bh(&mm->context.lock);
 200                 if (!list_empty(&mm->context.pgtable_list)) {
 201                         page = list_first_entry(&mm->context.pgtable_list,
 202                                                 struct page, lru);
 203                         mask = atomic_read(&page->_refcount) >> 24;
 204                         mask = (mask | (mask >> 4)) & 3;
 205                         if (mask != 3) {
 206                                 table = (unsigned long *) page_to_phys(page);
 207                                 bit = mask & 1;         /* =1 -> second 2K */
 208                                 if (bit)
 209                                         table += PTRS_PER_PTE;
 210                                 atomic_xor_bits(&page->_refcount,
 211                                                         1U << (bit + 24));
 212                                 list_del(&page->lru);
 213                         }
 214                 }
 215                 spin_unlock_bh(&mm->context.lock);
 216                 if (table)
 217                         return table;
 218         }
 219         /* Allocate a fresh page */
 220         page = alloc_page(GFP_KERNEL);
 221         if (!page)
 222                 return NULL;
 223         if (!pgtable_pte_page_ctor(page)) {
 224                 __free_page(page);
 225                 return NULL;
 226         }
 227         arch_set_page_dat(page, 0);
 228         /* Initialize page table */
 229         table = (unsigned long *) page_to_phys(page);
 230         if (mm_alloc_pgste(mm)) {
 231                 /* Return 4K page table with PGSTEs */
 232                 atomic_xor_bits(&page->_refcount, 3 << 24);
 233                 memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
 234                 memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
 235         } else {
 236                 /* Return the first 2K fragment of the page */
 237                 atomic_xor_bits(&page->_refcount, 1 << 24);
 238                 memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE);
 239                 spin_lock_bh(&mm->context.lock);
 240                 list_add(&page->lru, &mm->context.pgtable_list);
 241                 spin_unlock_bh(&mm->context.lock);
 242         }
 243         return table;
 244 }
 245
 246 void page_table_free(struct mm_struct *mm, unsigned long *table)
 247 {
 248         struct page *page;
 249         unsigned int bit, mask;
 250
 251         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 252         if (!mm_alloc_pgste(mm)) {
 253                 /* Free 2K page table fragment of a 4K page */
 254                 bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
 255                 spin_lock_bh(&mm->context.lock);
 256                 mask = atomic_xor_bits(&page->_refcount, 1U << (bit + 24));
 257                 mask >>= 24;
 258                 if (mask & 3)
 259                         list_add(&page->lru, &mm->context.pgtable_list);
 260                 else
 261                         list_del(&page->lru);
 262                 spin_unlock_bh(&mm->context.lock);
 263                 if (mask != 0)
 264                         return;
 265         } else {
 266                 atomic_xor_bits(&page->_refcount, 3U << 24);
 267         }
 268
 269         pgtable_pte_page_dtor(page);
 270         __free_page(page);
 271 }
 272
 273 void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
 274                          unsigned long vmaddr)
 275 {
 276         struct mm_struct *mm;
 277         struct page *page;
 278         unsigned int bit, mask;
 279
 280         mm = tlb->mm;
 281         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 282         if (mm_alloc_pgste(mm)) {
 283                 gmap_unlink(mm, table, vmaddr);
 284                 table = (unsigned long *) (__pa(table) | 3);
 285                 tlb_remove_table(tlb, table);
 286                 return;
 287         }
 288         bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
 289         spin_lock_bh(&mm->context.lock);
 290         mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
 291         mask >>= 24;
 292         if (mask & 3)
 293                 list_add_tail(&page->lru, &mm->context.pgtable_list);
 294         else
 295                 list_del(&page->lru);
 296         spin_unlock_bh(&mm->context.lock);
 297         table = (unsigned long *) (__pa(table) | (1U << bit));
 298         tlb_remove_table(tlb, table);
 299 }
 300
 301 void __tlb_remove_table(void *_table)
 302 {
 303         unsigned int mask = (unsigned long) _table & 3;
 304         void *table = (void *)((unsigned long) _table ^ mask);
 305         struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 306
 307         switch (mask) {
 308         case 0:         /* pmd, pud, or p4d */
 309                 free_pages((unsigned long) table, 2);
 310                 break;
 311         case 1:         /* lower 2K of a 4K page table */
 312         case 2:         /* higher 2K of a 4K page table */
 313                 mask = atomic_xor_bits(&page->_refcount, mask << (4 + 24));
 314                 mask >>= 24;
 315                 if (mask != 0)
 316                         break;
 317                 fallthrough;
 318         case 3:         /* 4K page table with pgstes */
 319                 if (mask & 3)
 320                         atomic_xor_bits(&page->_refcount, 3 << 24);
 321                 pgtable_pte_page_dtor(page);
 322                 __free_page(page);
 323                 break;
 324         }
 325 }
 326
 327 /*
 328  * Base infrastructure required to generate basic asces, region, segment,
 329  * and page tables that do not make use of enhanced features like EDAT1.
 330  */
 331
 332 static struct kmem_cache *base_pgt_cache;
 333
 334 static unsigned long base_pgt_alloc(void)
 335 {
 336         u64 *table;
 337
 338         table = kmem_cache_alloc(base_pgt_cache, GFP_KERNEL);
 339         if (table)
 340                 memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
 341         return (unsigned long) table;
 342 }
 343
 344 static void base_pgt_free(unsigned long table)
 345 {
 346         kmem_cache_free(base_pgt_cache, (void *) table);
 347 }
 348
 349 static unsigned long base_crst_alloc(unsigned long val)
 350 {
 351         unsigned long table;
 352
 353         table =  __get_free_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
 354         if (table)
 355                 crst_table_init((unsigned long *)table, val);
 356         return table;
 357 }
 358
 359 static void base_crst_free(unsigned long table)
 360 {
 361         free_pages(table, CRST_ALLOC_ORDER);
 362 }
 363
 364 #define BASE_ADDR_END_FUNC(NAME, SIZE)                                  \
 365 static inline unsigned long base_##NAME##_addr_end(unsigned long addr,  \
 366                                                    unsigned long end)   \
 367 {                                                                       \
 368         unsigned long next = (addr + (SIZE)) & ~((SIZE) - 1);           \
 369                                                                         \
 370         return (next - 1) < (end - 1) ? next : end;                     \
 371 }
 372
 373 BASE_ADDR_END_FUNC(page,    _PAGE_SIZE)
 374 BASE_ADDR_END_FUNC(segment, _SEGMENT_SIZE)
 375 BASE_ADDR_END_FUNC(region3, _REGION3_SIZE)
 376 BASE_ADDR_END_FUNC(region2, _REGION2_SIZE)
 377 BASE_ADDR_END_FUNC(region1, _REGION1_SIZE)
 378
 379 static inline unsigned long base_lra(unsigned long address)
 380 {
 381         unsigned long real;
 382
 383         asm volatile(
 384                 "       lra     %0,0(%1)\n"
 385                 : "=d" (real) : "a" (address) : "cc");
 386         return real;
 387 }
 388
 389 static int base_page_walk(unsigned long origin, unsigned long addr,
 390                           unsigned long end, int alloc)
 391 {
 392         unsigned long *pte, next;
 393
 394         if (!alloc)
 395                 return 0;
 396         pte = (unsigned long *) origin;
 397         pte += (addr & _PAGE_INDEX) >> _PAGE_SHIFT;
 398         do {
 399                 next = base_page_addr_end(addr, end);
 400                 *pte = base_lra(addr);
 401         } while (pte++, addr = next, addr < end);
 402         return 0;
 403 }
 404
 405 static int base_segment_walk(unsigned long origin, unsigned long addr,
 406                              unsigned long end, int alloc)
 407 {
 408         unsigned long *ste, next, table;
 409         int rc;
 410
 411         ste = (unsigned long *) origin;
 412         ste += (addr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
 413         do {
 414                 next = base_segment_addr_end(addr, end);
 415                 if (*ste & _SEGMENT_ENTRY_INVALID) {
 416                         if (!alloc)
 417                                 continue;
 418                         table = base_pgt_alloc();
 419                         if (!table)
 420                                 return -ENOMEM;
 421                         *ste = table | _SEGMENT_ENTRY;
 422                 }
 423                 table = *ste & _SEGMENT_ENTRY_ORIGIN;
 424                 rc = base_page_walk(table, addr, next, alloc);
 425                 if (rc)
 426                         return rc;
 427                 if (!alloc)
 428                         base_pgt_free(table);
 429                 cond_resched();
 430         } while (ste++, addr = next, addr < end);
 431         return 0;
 432 }
 433
 434 static int base_region3_walk(unsigned long origin, unsigned long addr,
 435                              unsigned long end, int alloc)
 436 {
 437         unsigned long *rtte, next, table;
 438         int rc;
 439
 440         rtte = (unsigned long *) origin;
 441         rtte += (addr & _REGION3_INDEX) >> _REGION3_SHIFT;
 442         do {
 443                 next = base_region3_addr_end(addr, end);
 444                 if (*rtte & _REGION_ENTRY_INVALID) {
 445                         if (!alloc)
 446                                 continue;
 447                         table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
 448                         if (!table)
 449                                 return -ENOMEM;
 450                         *rtte = table | _REGION3_ENTRY;
 451                 }
 452                 table = *rtte & _REGION_ENTRY_ORIGIN;
 453                 rc = base_segment_walk(table, addr, next, alloc);
 454                 if (rc)
 455                         return rc;
 456                 if (!alloc)
 457                         base_crst_free(table);
 458         } while (rtte++, addr = next, addr < end);
 459         return 0;
 460 }
 461
 462 static int base_region2_walk(unsigned long origin, unsigned long addr,
 463                              unsigned long end, int alloc)
 464 {
 465         unsigned long *rste, next, table;
 466         int rc;
 467
 468         rste = (unsigned long *) origin;
 469         rste += (addr & _REGION2_INDEX) >> _REGION2_SHIFT;
 470         do {
 471                 next = base_region2_addr_end(addr, end);
 472                 if (*rste & _REGION_ENTRY_INVALID) {
 473                         if (!alloc)
 474                                 continue;
 475                         table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
 476                         if (!table)
 477                                 return -ENOMEM;
 478                         *rste = table | _REGION2_ENTRY;
 479                 }
 480                 table = *rste & _REGION_ENTRY_ORIGIN;
 481                 rc = base_region3_walk(table, addr, next, alloc);
 482                 if (rc)
 483                         return rc;
 484                 if (!alloc)
 485                         base_crst_free(table);
 486         } while (rste++, addr = next, addr < end);
 487         return 0;
 488 }
 489
 490 static int base_region1_walk(unsigned long origin, unsigned long addr,
 491                              unsigned long end, int alloc)
 492 {
 493         unsigned long *rfte, next, table;
 494         int rc;
 495
 496         rfte = (unsigned long *) origin;
 497         rfte += (addr & _REGION1_INDEX) >> _REGION1_SHIFT;
 498         do {
 499                 next = base_region1_addr_end(addr, end);
 500                 if (*rfte & _REGION_ENTRY_INVALID) {
 501                         if (!alloc)
 502                                 continue;
 503                         table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
 504                         if (!table)
 505                                 return -ENOMEM;
 506                         *rfte = table | _REGION1_ENTRY;
 507                 }
 508                 table = *rfte & _REGION_ENTRY_ORIGIN;
 509                 rc = base_region2_walk(table, addr, next, alloc);
 510                 if (rc)
 511                         return rc;
 512                 if (!alloc)
 513                         base_crst_free(table);
 514         } while (rfte++, addr = next, addr < end);
 515         return 0;
 516 }
 517
 518 /**
 519  * base_asce_free - free asce and tables returned from base_asce_alloc()
 520  * @asce: asce to be freed
 521  *
 522  * Frees all region, segment, and page tables that were allocated with a
 523  * corresponding base_asce_alloc() call.
 524  */
 525 void base_asce_free(unsigned long asce)
 526 {
 527         unsigned long table = asce & _ASCE_ORIGIN;
 528
 529         if (!asce)
 530                 return;
 531         switch (asce & _ASCE_TYPE_MASK) {
 532         case _ASCE_TYPE_SEGMENT:
 533                 base_segment_walk(table, 0, _REGION3_SIZE, 0);
 534                 break;
 535         case _ASCE_TYPE_REGION3:
 536                 base_region3_walk(table, 0, _REGION2_SIZE, 0);
 537                 break;
 538         case _ASCE_TYPE_REGION2:
 539                 base_region2_walk(table, 0, _REGION1_SIZE, 0);
 540                 break;
 541         case _ASCE_TYPE_REGION1:
 542                 base_region1_walk(table, 0, TASK_SIZE_MAX, 0);
 543                 break;
 544         }
 545         base_crst_free(table);
 546 }
 547
 548 static int base_pgt_cache_init(void)
 549 {
 550         static DEFINE_MUTEX(base_pgt_cache_mutex);
 551         unsigned long sz = _PAGE_TABLE_SIZE;
 552
 553         if (base_pgt_cache)
 554                 return 0;
 555         mutex_lock(&base_pgt_cache_mutex);
 556         if (!base_pgt_cache)
 557                 base_pgt_cache = kmem_cache_create("base_pgt", sz, sz, 0, NULL);
 558         mutex_unlock(&base_pgt_cache_mutex);
 559         return base_pgt_cache ? 0 : -ENOMEM;
 560 }
 561
 562 /**
 563  * base_asce_alloc - create kernel mapping without enhanced DAT features
 564  * @addr: virtual start address of kernel mapping
 565  * @num_pages: number of consecutive pages
 566  *
 567  * Generate an asce, including all required region, segment and page tables,
 568  * that can be used to access the virtual kernel mapping. The difference is
 569  * that the returned asce does not make use of any enhanced DAT features like
 570  * e.g. large pages. This is required for some I/O functions that pass an
 571  * asce, like e.g. some service call requests.
 572  *
 573  * Note: the returned asce may NEVER be attached to any cpu. It may only be
 574  *       used for I/O requests. tlb entries that might result because the
 575  *       asce was attached to a cpu won't be cleared.
 576  */
 577 unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages)
 578 {
 579         unsigned long asce, table, end;
 580         int rc;
 581
 582         if (base_pgt_cache_init())
 583                 return 0;
 584         end = addr + num_pages * PAGE_SIZE;
 585         if (end <= _REGION3_SIZE) {
 586                 table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
 587                 if (!table)
 588                         return 0;
 589                 rc = base_segment_walk(table, addr, end, 1);
 590                 asce = table | _ASCE_TYPE_SEGMENT | _ASCE_TABLE_LENGTH;
 591         } else if (end <= _REGION2_SIZE) {
 592                 table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
 593                 if (!table)
 594                         return 0;
 595                 rc = base_region3_walk(table, addr, end, 1);
 596                 asce = table | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
 597         } else if (end <= _REGION1_SIZE) {
 598                 table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
 599                 if (!table)
 600                         return 0;
 601                 rc = base_region2_walk(table, addr, end, 1);
 602                 asce = table | _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
 603         } else {
 604                 table = base_crst_alloc(_REGION1_ENTRY_EMPTY);
 605                 if (!table)
 606                         return 0;
 607                 rc = base_region1_walk(table, addr, end, 1);
 608                 asce = table | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
 609         }
 610         if (rc) {
 611                 base_asce_free(asce);
 612                 asce = 0;
 613         }
 614         return asce;
 615 }