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                 } else {
 105                         crst_table_init(table, _REGION1_ENTRY_EMPTY);
 106                         pgd_populate(mm, (pgd_t *) table, (p4d_t *) pgd);
 107                         mm->pgd = (pgd_t *) table;
 108                         mm->context.asce_limit = -PAGE_SIZE;
 109                         mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 110                                 _ASCE_USER_BITS | _ASCE_TYPE_REGION1;
 111                 }
 112                 notify = 1;
 113                 spin_unlock_bh(&mm->page_table_lock);
 114         }
 115         if (notify)
 116                 on_each_cpu(__crst_table_upgrade, mm, 0);
 117         return rc;
 118 }
 119
 120 void crst_table_downgrade(struct mm_struct *mm)
 121 {
 122         pgd_t *pgd;
 123
 124         /* downgrade should only happen from 3 to 2 levels (compat only) */
 125         VM_BUG_ON(mm->context.asce_limit != _REGION2_SIZE);
 126
 127         if (current->active_mm == mm) {
 128                 clear_user_asce();
 129                 __tlb_flush_mm(mm);
 130         }
 131
 132         pgd = mm->pgd;
 133         mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN);
 134         mm->context.asce_limit = _REGION3_SIZE;
 135         mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 136                            _ASCE_USER_BITS | _ASCE_TYPE_SEGMENT;
 137         crst_table_free(mm, (unsigned long *) pgd);
 138
 139         if (current->active_mm == mm)
 140                 set_user_asce(mm);
 141 }
 142
 143 static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
 144 {
 145         unsigned int old, new;
 146
 147         do {
 148                 old = atomic_read(v);
 149                 new = old ^ bits;
 150         } while (atomic_cmpxchg(v, old, new) != old);
 151         return new;
 152 }
 153
 154 #ifdef CONFIG_PGSTE
 155
 156 struct page *page_table_alloc_pgste(struct mm_struct *mm)
 157 {
 158         struct page *page;
 159         u64 *table;
 160
 161         page = alloc_page(GFP_KERNEL);
 162         if (page) {
 163                 table = (u64 *)page_to_phys(page);
 164                 memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
 165                 memset64(table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
 166         }
 167         return page;
 168 }
 169
 170 void page_table_free_pgste(struct page *page)
 171 {
 172         __free_page(page);
 173 }
 174
 175 #endif /* CONFIG_PGSTE */
 176
 177 /*
 178  * page table entry allocation/free routines.
 179  */
 180 unsigned long *page_table_alloc(struct mm_struct *mm)
 181 {
 182         unsigned long *table;
 183         struct page *page;
 184         unsigned int mask, bit;
 185
 186         /* Try to get a fragment of a 4K page as a 2K page table */
 187         if (!mm_alloc_pgste(mm)) {
 188                 table = NULL;
 189                 spin_lock_bh(&mm->context.lock);
 190                 if (!list_empty(&mm->context.pgtable_list)) {
 191                         page = list_first_entry(&mm->context.pgtable_list,
 192                                                 struct page, lru);
 193                         mask = atomic_read(&page->_refcount) >> 24;
 194                         mask = (mask | (mask >> 4)) & 3;
 195                         if (mask != 3) {
 196                                 table = (unsigned long *) page_to_phys(page);
 197                                 bit = mask & 1;         /* =1 -> second 2K */
 198                                 if (bit)
 199                                         table += PTRS_PER_PTE;
 200                                 atomic_xor_bits(&page->_refcount,
 201                                                         1U << (bit + 24));
 202                                 list_del(&page->lru);
 203                         }
 204                 }
 205                 spin_unlock_bh(&mm->context.lock);
 206                 if (table)
 207                         return table;
 208         }
 209         /* Allocate a fresh page */
 210         page = alloc_page(GFP_KERNEL);
 211         if (!page)
 212                 return NULL;
 213         if (!pgtable_page_ctor(page)) {
 214                 __free_page(page);
 215                 return NULL;
 216         }
 217         arch_set_page_dat(page, 0);
 218         /* Initialize page table */
 219         table = (unsigned long *) page_to_phys(page);
 220         if (mm_alloc_pgste(mm)) {
 221                 /* Return 4K page table with PGSTEs */
 222                 atomic_xor_bits(&page->_refcount, 3 << 24);
 223                 memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
 224                 memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
 225         } else {
 226                 /* Return the first 2K fragment of the page */
 227                 atomic_xor_bits(&page->_refcount, 1 << 24);
 228                 memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE);
 229                 spin_lock_bh(&mm->context.lock);
 230                 list_add(&page->lru, &mm->context.pgtable_list);
 231                 spin_unlock_bh(&mm->context.lock);
 232         }
 233         return table;
 234 }
 235
 236 void page_table_free(struct mm_struct *mm, unsigned long *table)
 237 {
 238         struct page *page;
 239         unsigned int bit, mask;
 240
 241         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 242         if (!mm_alloc_pgste(mm)) {
 243                 /* Free 2K page table fragment of a 4K page */
 244                 bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
 245                 spin_lock_bh(&mm->context.lock);
 246                 mask = atomic_xor_bits(&page->_refcount, 1U << (bit + 24));
 247                 mask >>= 24;
 248                 if (mask & 3)
 249                         list_add(&page->lru, &mm->context.pgtable_list);
 250                 else
 251                         list_del(&page->lru);
 252                 spin_unlock_bh(&mm->context.lock);
 253                 if (mask != 0)
 254                         return;
 255         } else {
 256                 atomic_xor_bits(&page->_refcount, 3U << 24);
 257         }
 258
 259         pgtable_page_dtor(page);
 260         __free_page(page);
 261 }
 262
 263 void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
 264                          unsigned long vmaddr)
 265 {
 266         struct mm_struct *mm;
 267         struct page *page;
 268         unsigned int bit, mask;
 269
 270         mm = tlb->mm;
 271         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 272         if (mm_alloc_pgste(mm)) {
 273                 gmap_unlink(mm, table, vmaddr);
 274                 table = (unsigned long *) (__pa(table) | 3);
 275                 tlb_remove_table(tlb, table);
 276                 return;
 277         }
 278         bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
 279         spin_lock_bh(&mm->context.lock);
 280         mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
 281         mask >>= 24;
 282         if (mask & 3)
 283                 list_add_tail(&page->lru, &mm->context.pgtable_list);
 284         else
 285                 list_del(&page->lru);
 286         spin_unlock_bh(&mm->context.lock);
 287         table = (unsigned long *) (__pa(table) | (1U << bit));
 288         tlb_remove_table(tlb, table);
 289 }
 290
 291 static void __tlb_remove_table(void *_table)
 292 {
 293         unsigned int mask = (unsigned long) _table & 3;
 294         void *table = (void *)((unsigned long) _table ^ mask);
 295         struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 296
 297         switch (mask) {
 298         case 0:         /* pmd, pud, or p4d */
 299                 free_pages((unsigned long) table, 2);
 300                 break;
 301         case 1:         /* lower 2K of a 4K page table */
 302         case 2:         /* higher 2K of a 4K page table */
 303                 mask = atomic_xor_bits(&page->_refcount, mask << (4 + 24));
 304                 mask >>= 24;
 305                 if (mask != 0)
 306                         break;
 307                 /* fallthrough */
 308         case 3:         /* 4K page table with pgstes */
 309                 if (mask & 3)
 310                         atomic_xor_bits(&page->_refcount, 3 << 24);
 311                 pgtable_page_dtor(page);
 312                 __free_page(page);
 313                 break;
 314         }
 315 }
 316
 317 static void tlb_remove_table_smp_sync(void *arg)
 318 {
 319         /* Simply deliver the interrupt */
 320 }
 321
 322 static void tlb_remove_table_one(void *table)
 323 {
 324         /*
 325          * This isn't an RCU grace period and hence the page-tables cannot be
 326          * assumed to be actually RCU-freed.
 327          *
 328          * It is however sufficient for software page-table walkers that rely
 329          * on IRQ disabling. See the comment near struct mmu_table_batch.
 330          */
 331         smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
 332         __tlb_remove_table(table);
 333 }
 334
 335 static void tlb_remove_table_rcu(struct rcu_head *head)
 336 {
 337         struct mmu_table_batch *batch;
 338         int i;
 339
 340         batch = container_of(head, struct mmu_table_batch, rcu);
 341
 342         for (i = 0; i < batch->nr; i++)
 343                 __tlb_remove_table(batch->tables[i]);
 344
 345         free_page((unsigned long)batch);
 346 }
 347
 348 void tlb_table_flush(struct mmu_gather *tlb)
 349 {
 350         struct mmu_table_batch **batch = &tlb->batch;
 351
 352         if (*batch) {
 353                 call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
 354                 *batch = NULL;
 355         }
 356 }
 357
 358 void tlb_remove_table(struct mmu_gather *tlb, void *table)
 359 {
 360         struct mmu_table_batch **batch = &tlb->batch;
 361
 362         tlb->mm->context.flush_mm = 1;
 363         if (*batch == NULL) {
 364                 *batch = (struct mmu_table_batch *)
 365                         __get_free_page(GFP_NOWAIT | __GFP_NOWARN);
 366                 if (*batch == NULL) {
 367                         __tlb_flush_mm_lazy(tlb->mm);
 368                         tlb_remove_table_one(table);
 369                         return;
 370                 }
 371                 (*batch)->nr = 0;
 372         }
 373         (*batch)->tables[(*batch)->nr++] = table;
 374         if ((*batch)->nr == MAX_TABLE_BATCH)
 375                 tlb_flush_mmu(tlb);
 376 }
 377
 378 /*
 379  * Base infrastructure required to generate basic asces, region, segment,
 380  * and page tables that do not make use of enhanced features like EDAT1.
 381  */
 382
 383 static struct kmem_cache *base_pgt_cache;
 384
 385 static unsigned long base_pgt_alloc(void)
 386 {
 387         u64 *table;
 388
 389         table = kmem_cache_alloc(base_pgt_cache, GFP_KERNEL);
 390         if (table)
 391                 memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
 392         return (unsigned long) table;
 393 }
 394
 395 static void base_pgt_free(unsigned long table)
 396 {
 397         kmem_cache_free(base_pgt_cache, (void *) table);
 398 }
 399
 400 static unsigned long base_crst_alloc(unsigned long val)
 401 {
 402         unsigned long table;
 403
 404         table =  __get_free_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
 405         if (table)
 406                 crst_table_init((unsigned long *)table, val);
 407         return table;
 408 }
 409
 410 static void base_crst_free(unsigned long table)
 411 {
 412         free_pages(table, CRST_ALLOC_ORDER);
 413 }
 414
 415 #define BASE_ADDR_END_FUNC(NAME, SIZE)                                  \
 416 static inline unsigned long base_##NAME##_addr_end(unsigned long addr,  \
 417                                                    unsigned long end)   \
 418 {                                                                       \
 419         unsigned long next = (addr + (SIZE)) & ~((SIZE) - 1);           \
 420                                                                         \
 421         return (next - 1) < (end - 1) ? next : end;                     \
 422 }
 423
 424 BASE_ADDR_END_FUNC(page,    _PAGE_SIZE)
 425 BASE_ADDR_END_FUNC(segment, _SEGMENT_SIZE)
 426 BASE_ADDR_END_FUNC(region3, _REGION3_SIZE)
 427 BASE_ADDR_END_FUNC(region2, _REGION2_SIZE)
 428 BASE_ADDR_END_FUNC(region1, _REGION1_SIZE)
 429
 430 static inline unsigned long base_lra(unsigned long address)
 431 {
 432         unsigned long real;
 433
 434         asm volatile(
 435                 "       lra     %0,0(%1)\n"
 436                 : "=d" (real) : "a" (address) : "cc");
 437         return real;
 438 }
 439
 440 static int base_page_walk(unsigned long origin, unsigned long addr,
 441                           unsigned long end, int alloc)
 442 {
 443         unsigned long *pte, next;
 444
 445         if (!alloc)
 446                 return 0;
 447         pte = (unsigned long *) origin;
 448         pte += (addr & _PAGE_INDEX) >> _PAGE_SHIFT;
 449         do {
 450                 next = base_page_addr_end(addr, end);
 451                 *pte = base_lra(addr);
 452         } while (pte++, addr = next, addr < end);
 453         return 0;
 454 }
 455
 456 static int base_segment_walk(unsigned long origin, unsigned long addr,
 457                              unsigned long end, int alloc)
 458 {
 459         unsigned long *ste, next, table;
 460         int rc;
 461
 462         ste = (unsigned long *) origin;
 463         ste += (addr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
 464         do {
 465                 next = base_segment_addr_end(addr, end);
 466                 if (*ste & _SEGMENT_ENTRY_INVALID) {
 467                         if (!alloc)
 468                                 continue;
 469                         table = base_pgt_alloc();
 470                         if (!table)
 471                                 return -ENOMEM;
 472                         *ste = table | _SEGMENT_ENTRY;
 473                 }
 474                 table = *ste & _SEGMENT_ENTRY_ORIGIN;
 475                 rc = base_page_walk(table, addr, next, alloc);
 476                 if (rc)
 477                         return rc;
 478                 if (!alloc)
 479                         base_pgt_free(table);
 480                 cond_resched();
 481         } while (ste++, addr = next, addr < end);
 482         return 0;
 483 }
 484
 485 static int base_region3_walk(unsigned long origin, unsigned long addr,
 486                              unsigned long end, int alloc)
 487 {
 488         unsigned long *rtte, next, table;
 489         int rc;
 490
 491         rtte = (unsigned long *) origin;
 492         rtte += (addr & _REGION3_INDEX) >> _REGION3_SHIFT;
 493         do {
 494                 next = base_region3_addr_end(addr, end);
 495                 if (*rtte & _REGION_ENTRY_INVALID) {
 496                         if (!alloc)
 497                                 continue;
 498                         table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
 499                         if (!table)
 500                                 return -ENOMEM;
 501                         *rtte = table | _REGION3_ENTRY;
 502                 }
 503                 table = *rtte & _REGION_ENTRY_ORIGIN;
 504                 rc = base_segment_walk(table, addr, next, alloc);
 505                 if (rc)
 506                         return rc;
 507                 if (!alloc)
 508                         base_crst_free(table);
 509         } while (rtte++, addr = next, addr < end);
 510         return 0;
 511 }
 512
 513 static int base_region2_walk(unsigned long origin, unsigned long addr,
 514                              unsigned long end, int alloc)
 515 {
 516         unsigned long *rste, next, table;
 517         int rc;
 518
 519         rste = (unsigned long *) origin;
 520         rste += (addr & _REGION2_INDEX) >> _REGION2_SHIFT;
 521         do {
 522                 next = base_region2_addr_end(addr, end);
 523                 if (*rste & _REGION_ENTRY_INVALID) {
 524                         if (!alloc)
 525                                 continue;
 526                         table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
 527                         if (!table)
 528                                 return -ENOMEM;
 529                         *rste = table | _REGION2_ENTRY;
 530                 }
 531                 table = *rste & _REGION_ENTRY_ORIGIN;
 532                 rc = base_region3_walk(table, addr, next, alloc);
 533                 if (rc)
 534                         return rc;
 535                 if (!alloc)
 536                         base_crst_free(table);
 537         } while (rste++, addr = next, addr < end);
 538         return 0;
 539 }
 540
 541 static int base_region1_walk(unsigned long origin, unsigned long addr,
 542                              unsigned long end, int alloc)
 543 {
 544         unsigned long *rfte, next, table;
 545         int rc;
 546
 547         rfte = (unsigned long *) origin;
 548         rfte += (addr & _REGION1_INDEX) >> _REGION1_SHIFT;
 549         do {
 550                 next = base_region1_addr_end(addr, end);
 551                 if (*rfte & _REGION_ENTRY_INVALID) {
 552                         if (!alloc)
 553                                 continue;
 554                         table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
 555                         if (!table)
 556                                 return -ENOMEM;
 557                         *rfte = table | _REGION1_ENTRY;
 558                 }
 559                 table = *rfte & _REGION_ENTRY_ORIGIN;
 560                 rc = base_region2_walk(table, addr, next, alloc);
 561                 if (rc)
 562                         return rc;
 563                 if (!alloc)
 564                         base_crst_free(table);
 565         } while (rfte++, addr = next, addr < end);
 566         return 0;
 567 }
 568
 569 /**
 570  * base_asce_free - free asce and tables returned from base_asce_alloc()
 571  * @asce: asce to be freed
 572  *
 573  * Frees all region, segment, and page tables that were allocated with a
 574  * corresponding base_asce_alloc() call.
 575  */
 576 void base_asce_free(unsigned long asce)
 577 {
 578         unsigned long table = asce & _ASCE_ORIGIN;
 579
 580         if (!asce)
 581                 return;
 582         switch (asce & _ASCE_TYPE_MASK) {
 583         case _ASCE_TYPE_SEGMENT:
 584                 base_segment_walk(table, 0, _REGION3_SIZE, 0);
 585                 break;
 586         case _ASCE_TYPE_REGION3:
 587                 base_region3_walk(table, 0, _REGION2_SIZE, 0);
 588                 break;
 589         case _ASCE_TYPE_REGION2:
 590                 base_region2_walk(table, 0, _REGION1_SIZE, 0);
 591                 break;
 592         case _ASCE_TYPE_REGION1:
 593                 base_region1_walk(table, 0, -_PAGE_SIZE, 0);
 594                 break;
 595         }
 596         base_crst_free(table);
 597 }
 598
 599 static int base_pgt_cache_init(void)
 600 {
 601         static DEFINE_MUTEX(base_pgt_cache_mutex);
 602         unsigned long sz = _PAGE_TABLE_SIZE;
 603
 604         if (base_pgt_cache)
 605                 return 0;
 606         mutex_lock(&base_pgt_cache_mutex);
 607         if (!base_pgt_cache)
 608                 base_pgt_cache = kmem_cache_create("base_pgt", sz, sz, 0, NULL);
 609         mutex_unlock(&base_pgt_cache_mutex);
 610         return base_pgt_cache ? 0 : -ENOMEM;
 611 }
 612
 613 /**
 614  * base_asce_alloc - create kernel mapping without enhanced DAT features
 615  * @addr: virtual start address of kernel mapping
 616  * @num_pages: number of consecutive pages
 617  *
 618  * Generate an asce, including all required region, segment and page tables,
 619  * that can be used to access the virtual kernel mapping. The difference is
 620  * that the returned asce does not make use of any enhanced DAT features like
 621  * e.g. large pages. This is required for some I/O functions that pass an
 622  * asce, like e.g. some service call requests.
 623  *
 624  * Note: the returned asce may NEVER be attached to any cpu. It may only be
 625  *       used for I/O requests. tlb entries that might result because the
 626  *       asce was attached to a cpu won't be cleared.
 627  */
 628 unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages)
 629 {
 630         unsigned long asce, table, end;
 631         int rc;
 632
 633         if (base_pgt_cache_init())
 634                 return 0;
 635         end = addr + num_pages * PAGE_SIZE;
 636         if (end <= _REGION3_SIZE) {
 637                 table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
 638                 if (!table)
 639                         return 0;
 640                 rc = base_segment_walk(table, addr, end, 1);
 641                 asce = table | _ASCE_TYPE_SEGMENT | _ASCE_TABLE_LENGTH;
 642         } else if (end <= _REGION2_SIZE) {
 643                 table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
 644                 if (!table)
 645                         return 0;
 646                 rc = base_region3_walk(table, addr, end, 1);
 647                 asce = table | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
 648         } else if (end <= _REGION1_SIZE) {
 649                 table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
 650                 if (!table)
 651                         return 0;
 652                 rc = base_region2_walk(table, addr, end, 1);
 653                 asce = table | _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
 654         } else {
 655                 table = base_crst_alloc(_REGION1_ENTRY_EMPTY);
 656                 if (!table)
 657                         return 0;
 658                 rc = base_region1_walk(table, addr, end, 1);
 659                 asce = table | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
 660         }
 661         if (rc) {
 662                 base_asce_free(asce);
 663                 asce = 0;
 664         }
 665         return asce;
 666 }