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->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN);
 135         mm->context.asce_limit = _REGION3_SIZE;
 136         mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 137                            _ASCE_USER_BITS | _ASCE_TYPE_SEGMENT;
 138         crst_table_free(mm, (unsigned long *) pgd);
 139
 140         if (current->active_mm == mm)
 141                 set_user_asce(mm);
 142 }
 143
 144 static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
 145 {
 146         unsigned int old, new;
 147
 148         do {
 149                 old = atomic_read(v);
 150                 new = old ^ bits;
 151         } while (atomic_cmpxchg(v, old, new) != old);
 152         return new;
 153 }
 154
 155 #ifdef CONFIG_PGSTE
 156
 157 struct page *page_table_alloc_pgste(struct mm_struct *mm)
 158 {
 159         struct page *page;
 160         u64 *table;
 161
 162         page = alloc_page(GFP_KERNEL);
 163         if (page) {
 164                 table = (u64 *)page_to_phys(page);
 165                 memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
 166                 memset64(table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
 167         }
 168         return page;
 169 }
 170
 171 void page_table_free_pgste(struct page *page)
 172 {
 173         __free_page(page);
 174 }
 175
 176 #endif /* CONFIG_PGSTE */
 177
 178 /*
 179  * page table entry allocation/free routines.
 180  */
 181 unsigned long *page_table_alloc(struct mm_struct *mm)
 182 {
 183         unsigned long *table;
 184         struct page *page;
 185         unsigned int mask, bit;
 186
 187         /* Try to get a fragment of a 4K page as a 2K page table */
 188         if (!mm_alloc_pgste(mm)) {
 189                 table = NULL;
 190                 spin_lock_bh(&mm->context.lock);
 191                 if (!list_empty(&mm->context.pgtable_list)) {
 192                         page = list_first_entry(&mm->context.pgtable_list,
 193                                                 struct page, lru);
 194                         mask = atomic_read(&page->_refcount) >> 24;
 195                         mask = (mask | (mask >> 4)) & 3;
 196                         if (mask != 3) {
 197                                 table = (unsigned long *) page_to_phys(page);
 198                                 bit = mask & 1;         /* =1 -> second 2K */
 199                                 if (bit)
 200                                         table += PTRS_PER_PTE;
 201                                 atomic_xor_bits(&page->_refcount,
 202                                                         1U << (bit + 24));
 203                                 list_del(&page->lru);
 204                         }
 205                 }
 206                 spin_unlock_bh(&mm->context.lock);
 207                 if (table)
 208                         return table;
 209         }
 210         /* Allocate a fresh page */
 211         page = alloc_page(GFP_KERNEL);
 212         if (!page)
 213                 return NULL;
 214         if (!pgtable_page_ctor(page)) {
 215                 __free_page(page);
 216                 return NULL;
 217         }
 218         arch_set_page_dat(page, 0);
 219         /* Initialize page table */
 220         table = (unsigned long *) page_to_phys(page);
 221         if (mm_alloc_pgste(mm)) {
 222                 /* Return 4K page table with PGSTEs */
 223                 atomic_xor_bits(&page->_refcount, 3 << 24);
 224                 memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
 225                 memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
 226         } else {
 227                 /* Return the first 2K fragment of the page */
 228                 atomic_xor_bits(&page->_refcount, 1 << 24);
 229                 memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE);
 230                 spin_lock_bh(&mm->context.lock);
 231                 list_add(&page->lru, &mm->context.pgtable_list);
 232                 spin_unlock_bh(&mm->context.lock);
 233         }
 234         return table;
 235 }
 236
 237 void page_table_free(struct mm_struct *mm, unsigned long *table)
 238 {
 239         struct page *page;
 240         unsigned int bit, mask;
 241
 242         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 243         if (!mm_alloc_pgste(mm)) {
 244                 /* Free 2K page table fragment of a 4K page */
 245                 bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
 246                 spin_lock_bh(&mm->context.lock);
 247                 mask = atomic_xor_bits(&page->_refcount, 1U << (bit + 24));
 248                 mask >>= 24;
 249                 if (mask & 3)
 250                         list_add(&page->lru, &mm->context.pgtable_list);
 251                 else
 252                         list_del(&page->lru);
 253                 spin_unlock_bh(&mm->context.lock);
 254                 if (mask != 0)
 255                         return;
 256         } else {
 257                 atomic_xor_bits(&page->_refcount, 3U << 24);
 258         }
 259
 260         pgtable_page_dtor(page);
 261         __free_page(page);
 262 }
 263
 264 void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
 265                          unsigned long vmaddr)
 266 {
 267         struct mm_struct *mm;
 268         struct page *page;
 269         unsigned int bit, mask;
 270
 271         mm = tlb->mm;
 272         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 273         if (mm_alloc_pgste(mm)) {
 274                 gmap_unlink(mm, table, vmaddr);
 275                 table = (unsigned long *) (__pa(table) | 3);
 276                 tlb_remove_table(tlb, table);
 277                 return;
 278         }
 279         bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
 280         spin_lock_bh(&mm->context.lock);
 281         mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
 282         mask >>= 24;
 283         if (mask & 3)
 284                 list_add_tail(&page->lru, &mm->context.pgtable_list);
 285         else
 286                 list_del(&page->lru);
 287         spin_unlock_bh(&mm->context.lock);
 288         table = (unsigned long *) (__pa(table) | (1U << bit));
 289         tlb_remove_table(tlb, table);
 290 }
 291
 292 static void __tlb_remove_table(void *_table)
 293 {
 294         unsigned int mask = (unsigned long) _table & 3;
 295         void *table = (void *)((unsigned long) _table ^ mask);
 296         struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 297
 298         switch (mask) {
 299         case 0:         /* pmd, pud, or p4d */
 300                 free_pages((unsigned long) table, 2);
 301                 break;
 302         case 1:         /* lower 2K of a 4K page table */
 303         case 2:         /* higher 2K of a 4K page table */
 304                 mask = atomic_xor_bits(&page->_refcount, mask << (4 + 24));
 305                 mask >>= 24;
 306                 if (mask != 0)
 307                         break;
 308                 /* fallthrough */
 309         case 3:         /* 4K page table with pgstes */
 310                 if (mask & 3)
 311                         atomic_xor_bits(&page->_refcount, 3 << 24);
 312                 pgtable_page_dtor(page);
 313                 __free_page(page);
 314                 break;
 315         }
 316 }
 317
 318 static void tlb_remove_table_smp_sync(void *arg)
 319 {
 320         /* Simply deliver the interrupt */
 321 }
 322
 323 static void tlb_remove_table_one(void *table)
 324 {
 325         /*
 326          * This isn't an RCU grace period and hence the page-tables cannot be
 327          * assumed to be actually RCU-freed.
 328          *
 329          * It is however sufficient for software page-table walkers that rely
 330          * on IRQ disabling. See the comment near struct mmu_table_batch.
 331          */
 332         smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
 333         __tlb_remove_table(table);
 334 }
 335
 336 static void tlb_remove_table_rcu(struct rcu_head *head)
 337 {
 338         struct mmu_table_batch *batch;
 339         int i;
 340
 341         batch = container_of(head, struct mmu_table_batch, rcu);
 342
 343         for (i = 0; i < batch->nr; i++)
 344                 __tlb_remove_table(batch->tables[i]);
 345
 346         free_page((unsigned long)batch);
 347 }
 348
 349 void tlb_table_flush(struct mmu_gather *tlb)
 350 {
 351         struct mmu_table_batch **batch = &tlb->batch;
 352
 353         if (*batch) {
 354                 call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
 355                 *batch = NULL;
 356         }
 357 }
 358
 359 void tlb_remove_table(struct mmu_gather *tlb, void *table)
 360 {
 361         struct mmu_table_batch **batch = &tlb->batch;
 362
 363         tlb->mm->context.flush_mm = 1;
 364         if (*batch == NULL) {
 365                 *batch = (struct mmu_table_batch *)
 366                         __get_free_page(GFP_NOWAIT | __GFP_NOWARN);
 367                 if (*batch == NULL) {
 368                         __tlb_flush_mm_lazy(tlb->mm);
 369                         tlb_remove_table_one(table);
 370                         return;
 371                 }
 372                 (*batch)->nr = 0;
 373         }
 374         (*batch)->tables[(*batch)->nr++] = table;
 375         if ((*batch)->nr == MAX_TABLE_BATCH)
 376                 tlb_flush_mmu(tlb);
 377 }
 378
 379 /*
 380  * Base infrastructure required to generate basic asces, region, segment,
 381  * and page tables that do not make use of enhanced features like EDAT1.
 382  */
 383
 384 static struct kmem_cache *base_pgt_cache;
 385
 386 static unsigned long base_pgt_alloc(void)
 387 {
 388         u64 *table;
 389
 390         table = kmem_cache_alloc(base_pgt_cache, GFP_KERNEL);
 391         if (table)
 392                 memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
 393         return (unsigned long) table;
 394 }
 395
 396 static void base_pgt_free(unsigned long table)
 397 {
 398         kmem_cache_free(base_pgt_cache, (void *) table);
 399 }
 400
 401 static unsigned long base_crst_alloc(unsigned long val)
 402 {
 403         unsigned long table;
 404
 405         table =  __get_free_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
 406         if (table)
 407                 crst_table_init((unsigned long *)table, val);
 408         return table;
 409 }
 410
 411 static void base_crst_free(unsigned long table)
 412 {
 413         free_pages(table, CRST_ALLOC_ORDER);
 414 }
 415
 416 #define BASE_ADDR_END_FUNC(NAME, SIZE)                                  \
 417 static inline unsigned long base_##NAME##_addr_end(unsigned long addr,  \
 418                                                    unsigned long end)   \
 419 {                                                                       \
 420         unsigned long next = (addr + (SIZE)) & ~((SIZE) - 1);           \
 421                                                                         \
 422         return (next - 1) < (end - 1) ? next : end;                     \
 423 }
 424
 425 BASE_ADDR_END_FUNC(page,    _PAGE_SIZE)
 426 BASE_ADDR_END_FUNC(segment, _SEGMENT_SIZE)
 427 BASE_ADDR_END_FUNC(region3, _REGION3_SIZE)
 428 BASE_ADDR_END_FUNC(region2, _REGION2_SIZE)
 429 BASE_ADDR_END_FUNC(region1, _REGION1_SIZE)
 430
 431 static inline unsigned long base_lra(unsigned long address)
 432 {
 433         unsigned long real;
 434
 435         asm volatile(
 436                 "       lra     %0,0(%1)\n"
 437                 : "=d" (real) : "a" (address) : "cc");
 438         return real;
 439 }
 440
 441 static int base_page_walk(unsigned long origin, unsigned long addr,
 442                           unsigned long end, int alloc)
 443 {
 444         unsigned long *pte, next;
 445
 446         if (!alloc)
 447                 return 0;
 448         pte = (unsigned long *) origin;
 449         pte += (addr & _PAGE_INDEX) >> _PAGE_SHIFT;
 450         do {
 451                 next = base_page_addr_end(addr, end);
 452                 *pte = base_lra(addr);
 453         } while (pte++, addr = next, addr < end);
 454         return 0;
 455 }
 456
 457 static int base_segment_walk(unsigned long origin, unsigned long addr,
 458                              unsigned long end, int alloc)
 459 {
 460         unsigned long *ste, next, table;
 461         int rc;
 462
 463         ste = (unsigned long *) origin;
 464         ste += (addr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
 465         do {
 466                 next = base_segment_addr_end(addr, end);
 467                 if (*ste & _SEGMENT_ENTRY_INVALID) {
 468                         if (!alloc)
 469                                 continue;
 470                         table = base_pgt_alloc();
 471                         if (!table)
 472                                 return -ENOMEM;
 473                         *ste = table | _SEGMENT_ENTRY;
 474                 }
 475                 table = *ste & _SEGMENT_ENTRY_ORIGIN;
 476                 rc = base_page_walk(table, addr, next, alloc);
 477                 if (rc)
 478                         return rc;
 479                 if (!alloc)
 480                         base_pgt_free(table);
 481                 cond_resched();
 482         } while (ste++, addr = next, addr < end);
 483         return 0;
 484 }
 485
 486 static int base_region3_walk(unsigned long origin, unsigned long addr,
 487                              unsigned long end, int alloc)
 488 {
 489         unsigned long *rtte, next, table;
 490         int rc;
 491
 492         rtte = (unsigned long *) origin;
 493         rtte += (addr & _REGION3_INDEX) >> _REGION3_SHIFT;
 494         do {
 495                 next = base_region3_addr_end(addr, end);
 496                 if (*rtte & _REGION_ENTRY_INVALID) {
 497                         if (!alloc)
 498                                 continue;
 499                         table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
 500                         if (!table)
 501                                 return -ENOMEM;
 502                         *rtte = table | _REGION3_ENTRY;
 503                 }
 504                 table = *rtte & _REGION_ENTRY_ORIGIN;
 505                 rc = base_segment_walk(table, addr, next, alloc);
 506                 if (rc)
 507                         return rc;
 508                 if (!alloc)
 509                         base_crst_free(table);
 510         } while (rtte++, addr = next, addr < end);
 511         return 0;
 512 }
 513
 514 static int base_region2_walk(unsigned long origin, unsigned long addr,
 515                              unsigned long end, int alloc)
 516 {
 517         unsigned long *rste, next, table;
 518         int rc;
 519
 520         rste = (unsigned long *) origin;
 521         rste += (addr & _REGION2_INDEX) >> _REGION2_SHIFT;
 522         do {
 523                 next = base_region2_addr_end(addr, end);
 524                 if (*rste & _REGION_ENTRY_INVALID) {
 525                         if (!alloc)
 526                                 continue;
 527                         table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
 528                         if (!table)
 529                                 return -ENOMEM;
 530                         *rste = table | _REGION2_ENTRY;
 531                 }
 532                 table = *rste & _REGION_ENTRY_ORIGIN;
 533                 rc = base_region3_walk(table, addr, next, alloc);
 534                 if (rc)
 535                         return rc;
 536                 if (!alloc)
 537                         base_crst_free(table);
 538         } while (rste++, addr = next, addr < end);
 539         return 0;
 540 }
 541
 542 static int base_region1_walk(unsigned long origin, unsigned long addr,
 543                              unsigned long end, int alloc)
 544 {
 545         unsigned long *rfte, next, table;
 546         int rc;
 547
 548         rfte = (unsigned long *) origin;
 549         rfte += (addr & _REGION1_INDEX) >> _REGION1_SHIFT;
 550         do {
 551                 next = base_region1_addr_end(addr, end);
 552                 if (*rfte & _REGION_ENTRY_INVALID) {
 553                         if (!alloc)
 554                                 continue;
 555                         table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
 556                         if (!table)
 557                                 return -ENOMEM;
 558                         *rfte = table | _REGION1_ENTRY;
 559                 }
 560                 table = *rfte & _REGION_ENTRY_ORIGIN;
 561                 rc = base_region2_walk(table, addr, next, alloc);
 562                 if (rc)
 563                         return rc;
 564                 if (!alloc)
 565                         base_crst_free(table);
 566         } while (rfte++, addr = next, addr < end);
 567         return 0;
 568 }
 569
 570 /**
 571  * base_asce_free - free asce and tables returned from base_asce_alloc()
 572  * @asce: asce to be freed
 573  *
 574  * Frees all region, segment, and page tables that were allocated with a
 575  * corresponding base_asce_alloc() call.
 576  */
 577 void base_asce_free(unsigned long asce)
 578 {
 579         unsigned long table = asce & _ASCE_ORIGIN;
 580
 581         if (!asce)
 582                 return;
 583         switch (asce & _ASCE_TYPE_MASK) {
 584         case _ASCE_TYPE_SEGMENT:
 585                 base_segment_walk(table, 0, _REGION3_SIZE, 0);
 586                 break;
 587         case _ASCE_TYPE_REGION3:
 588                 base_region3_walk(table, 0, _REGION2_SIZE, 0);
 589                 break;
 590         case _ASCE_TYPE_REGION2:
 591                 base_region2_walk(table, 0, _REGION1_SIZE, 0);
 592                 break;
 593         case _ASCE_TYPE_REGION1:
 594                 base_region1_walk(table, 0, -_PAGE_SIZE, 0);
 595                 break;
 596         }
 597         base_crst_free(table);
 598 }
 599
 600 static int base_pgt_cache_init(void)
 601 {
 602         static DEFINE_MUTEX(base_pgt_cache_mutex);
 603         unsigned long sz = _PAGE_TABLE_SIZE;
 604
 605         if (base_pgt_cache)
 606                 return 0;
 607         mutex_lock(&base_pgt_cache_mutex);
 608         if (!base_pgt_cache)
 609                 base_pgt_cache = kmem_cache_create("base_pgt", sz, sz, 0, NULL);
 610         mutex_unlock(&base_pgt_cache_mutex);
 611         return base_pgt_cache ? 0 : -ENOMEM;
 612 }
 613
 614 /**
 615  * base_asce_alloc - create kernel mapping without enhanced DAT features
 616  * @addr: virtual start address of kernel mapping
 617  * @num_pages: number of consecutive pages
 618  *
 619  * Generate an asce, including all required region, segment and page tables,
 620  * that can be used to access the virtual kernel mapping. The difference is
 621  * that the returned asce does not make use of any enhanced DAT features like
 622  * e.g. large pages. This is required for some I/O functions that pass an
 623  * asce, like e.g. some service call requests.
 624  *
 625  * Note: the returned asce may NEVER be attached to any cpu. It may only be
 626  *       used for I/O requests. tlb entries that might result because the
 627  *       asce was attached to a cpu won't be cleared.
 628  */
 629 unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages)
 630 {
 631         unsigned long asce, table, end;
 632         int rc;
 633
 634         if (base_pgt_cache_init())
 635                 return 0;
 636         end = addr + num_pages * PAGE_SIZE;
 637         if (end <= _REGION3_SIZE) {
 638                 table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
 639                 if (!table)
 640                         return 0;
 641                 rc = base_segment_walk(table, addr, end, 1);
 642                 asce = table | _ASCE_TYPE_SEGMENT | _ASCE_TABLE_LENGTH;
 643         } else if (end <= _REGION2_SIZE) {
 644                 table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
 645                 if (!table)
 646                         return 0;
 647                 rc = base_region3_walk(table, addr, end, 1);
 648                 asce = table | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
 649         } else if (end <= _REGION1_SIZE) {
 650                 table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
 651                 if (!table)
 652                         return 0;
 653                 rc = base_region2_walk(table, addr, end, 1);
 654                 asce = table | _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
 655         } else {
 656                 table = base_crst_alloc(_REGION1_ENTRY_EMPTY);
 657                 if (!table)
 658                         return 0;
 659                 rc = base_region1_walk(table, addr, end, 1);
 660                 asce = table | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
 661         }
 662         if (rc) {
 663                 base_asce_free(asce);
 664                 asce = 0;
 665         }
 666         return asce;
 667 }