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