Merge with Linus' kernel.
[linux-2.6] / arch / arm / mm / mm-armv.c
1 /*
2  *  linux/arch/arm/mm/mm-armv.c
3  *
4  *  Copyright (C) 1998-2005 Russell King
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  *  Page table sludge for ARM v3 and v4 processor architectures.
11  */
12 #include <linux/config.h>
13 #include <linux/module.h>
14 #include <linux/mm.h>
15 #include <linux/init.h>
16 #include <linux/bootmem.h>
17 #include <linux/highmem.h>
18 #include <linux/nodemask.h>
19
20 #include <asm/pgalloc.h>
21 #include <asm/page.h>
22 #include <asm/setup.h>
23 #include <asm/tlbflush.h>
24
25 #include <asm/mach/map.h>
26
27 #define CPOLICY_UNCACHED        0
28 #define CPOLICY_BUFFERED        1
29 #define CPOLICY_WRITETHROUGH    2
30 #define CPOLICY_WRITEBACK       3
31 #define CPOLICY_WRITEALLOC      4
32
33 static unsigned int cachepolicy __initdata = CPOLICY_WRITEBACK;
34 static unsigned int ecc_mask __initdata = 0;
35 pgprot_t pgprot_kernel;
36
37 EXPORT_SYMBOL(pgprot_kernel);
38
39 pmd_t *top_pmd;
40
41 struct cachepolicy {
42         const char      policy[16];
43         unsigned int    cr_mask;
44         unsigned int    pmd;
45         unsigned int    pte;
46 };
47
48 static struct cachepolicy cache_policies[] __initdata = {
49         {
50                 .policy         = "uncached",
51                 .cr_mask        = CR_W|CR_C,
52                 .pmd            = PMD_SECT_UNCACHED,
53                 .pte            = 0,
54         }, {
55                 .policy         = "buffered",
56                 .cr_mask        = CR_C,
57                 .pmd            = PMD_SECT_BUFFERED,
58                 .pte            = PTE_BUFFERABLE,
59         }, {
60                 .policy         = "writethrough",
61                 .cr_mask        = 0,
62                 .pmd            = PMD_SECT_WT,
63                 .pte            = PTE_CACHEABLE,
64         }, {
65                 .policy         = "writeback",
66                 .cr_mask        = 0,
67                 .pmd            = PMD_SECT_WB,
68                 .pte            = PTE_BUFFERABLE|PTE_CACHEABLE,
69         }, {
70                 .policy         = "writealloc",
71                 .cr_mask        = 0,
72                 .pmd            = PMD_SECT_WBWA,
73                 .pte            = PTE_BUFFERABLE|PTE_CACHEABLE,
74         }
75 };
76
77 /*
78  * These are useful for identifing cache coherency
79  * problems by allowing the cache or the cache and
80  * writebuffer to be turned off.  (Note: the write
81  * buffer should not be on and the cache off).
82  */
83 static void __init early_cachepolicy(char **p)
84 {
85         int i;
86
87         for (i = 0; i < ARRAY_SIZE(cache_policies); i++) {
88                 int len = strlen(cache_policies[i].policy);
89
90                 if (memcmp(*p, cache_policies[i].policy, len) == 0) {
91                         cachepolicy = i;
92                         cr_alignment &= ~cache_policies[i].cr_mask;
93                         cr_no_alignment &= ~cache_policies[i].cr_mask;
94                         *p += len;
95                         break;
96                 }
97         }
98         if (i == ARRAY_SIZE(cache_policies))
99                 printk(KERN_ERR "ERROR: unknown or unsupported cache policy\n");
100         flush_cache_all();
101         set_cr(cr_alignment);
102 }
103
104 static void __init early_nocache(char **__unused)
105 {
106         char *p = "buffered";
107         printk(KERN_WARNING "nocache is deprecated; use cachepolicy=%s\n", p);
108         early_cachepolicy(&p);
109 }
110
111 static void __init early_nowrite(char **__unused)
112 {
113         char *p = "uncached";
114         printk(KERN_WARNING "nowb is deprecated; use cachepolicy=%s\n", p);
115         early_cachepolicy(&p);
116 }
117
118 static void __init early_ecc(char **p)
119 {
120         if (memcmp(*p, "on", 2) == 0) {
121                 ecc_mask = PMD_PROTECTION;
122                 *p += 2;
123         } else if (memcmp(*p, "off", 3) == 0) {
124                 ecc_mask = 0;
125                 *p += 3;
126         }
127 }
128
129 __early_param("nocache", early_nocache);
130 __early_param("nowb", early_nowrite);
131 __early_param("cachepolicy=", early_cachepolicy);
132 __early_param("ecc=", early_ecc);
133
134 static int __init noalign_setup(char *__unused)
135 {
136         cr_alignment &= ~CR_A;
137         cr_no_alignment &= ~CR_A;
138         set_cr(cr_alignment);
139         return 1;
140 }
141
142 __setup("noalign", noalign_setup);
143
144 #define FIRST_KERNEL_PGD_NR     (FIRST_USER_PGD_NR + USER_PTRS_PER_PGD)
145
146 static inline pmd_t *pmd_off(pgd_t *pgd, unsigned long virt)
147 {
148         return pmd_offset(pgd, virt);
149 }
150
151 static inline pmd_t *pmd_off_k(unsigned long virt)
152 {
153         return pmd_off(pgd_offset_k(virt), virt);
154 }
155
156 /*
157  * need to get a 16k page for level 1
158  */
159 pgd_t *get_pgd_slow(struct mm_struct *mm)
160 {
161         pgd_t *new_pgd, *init_pgd;
162         pmd_t *new_pmd, *init_pmd;
163         pte_t *new_pte, *init_pte;
164
165         new_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL, 2);
166         if (!new_pgd)
167                 goto no_pgd;
168
169         memzero(new_pgd, FIRST_KERNEL_PGD_NR * sizeof(pgd_t));
170
171         /*
172          * Copy over the kernel and IO PGD entries
173          */
174         init_pgd = pgd_offset_k(0);
175         memcpy(new_pgd + FIRST_KERNEL_PGD_NR, init_pgd + FIRST_KERNEL_PGD_NR,
176                        (PTRS_PER_PGD - FIRST_KERNEL_PGD_NR) * sizeof(pgd_t));
177
178         clean_dcache_area(new_pgd, PTRS_PER_PGD * sizeof(pgd_t));
179
180         if (!vectors_high()) {
181                 /*
182                  * On ARM, first page must always be allocated since it
183                  * contains the machine vectors.
184                  */
185                 new_pmd = pmd_alloc(mm, new_pgd, 0);
186                 if (!new_pmd)
187                         goto no_pmd;
188
189                 new_pte = pte_alloc_map(mm, new_pmd, 0);
190                 if (!new_pte)
191                         goto no_pte;
192
193                 init_pmd = pmd_offset(init_pgd, 0);
194                 init_pte = pte_offset_map_nested(init_pmd, 0);
195                 set_pte(new_pte, *init_pte);
196                 pte_unmap_nested(init_pte);
197                 pte_unmap(new_pte);
198         }
199
200         return new_pgd;
201
202 no_pte:
203         pmd_free(new_pmd);
204 no_pmd:
205         free_pages((unsigned long)new_pgd, 2);
206 no_pgd:
207         return NULL;
208 }
209
210 void free_pgd_slow(pgd_t *pgd)
211 {
212         pmd_t *pmd;
213         struct page *pte;
214
215         if (!pgd)
216                 return;
217
218         /* pgd is always present and good */
219         pmd = pmd_off(pgd, 0);
220         if (pmd_none(*pmd))
221                 goto free;
222         if (pmd_bad(*pmd)) {
223                 pmd_ERROR(*pmd);
224                 pmd_clear(pmd);
225                 goto free;
226         }
227
228         pte = pmd_page(*pmd);
229         pmd_clear(pmd);
230         dec_page_state(nr_page_table_pages);
231         pte_lock_deinit(pte);
232         pte_free(pte);
233         pmd_free(pmd);
234 free:
235         free_pages((unsigned long) pgd, 2);
236 }
237
238 /*
239  * Create a SECTION PGD between VIRT and PHYS in domain
240  * DOMAIN with protection PROT.  This operates on half-
241  * pgdir entry increments.
242  */
243 static inline void
244 alloc_init_section(unsigned long virt, unsigned long phys, int prot)
245 {
246         pmd_t *pmdp = pmd_off_k(virt);
247
248         if (virt & (1 << 20))
249                 pmdp++;
250
251         *pmdp = __pmd(phys | prot);
252         flush_pmd_entry(pmdp);
253 }
254
255 /*
256  * Create a SUPER SECTION PGD between VIRT and PHYS with protection PROT
257  */
258 static inline void
259 alloc_init_supersection(unsigned long virt, unsigned long phys, int prot)
260 {
261         int i;
262
263         for (i = 0; i < 16; i += 1) {
264                 alloc_init_section(virt, phys, prot | PMD_SECT_SUPER);
265
266                 virt += (PGDIR_SIZE / 2);
267         }
268 }
269
270 /*
271  * Add a PAGE mapping between VIRT and PHYS in domain
272  * DOMAIN with protection PROT.  Note that due to the
273  * way we map the PTEs, we must allocate two PTE_SIZE'd
274  * blocks - one for the Linux pte table, and one for
275  * the hardware pte table.
276  */
277 static inline void
278 alloc_init_page(unsigned long virt, unsigned long phys, unsigned int prot_l1, pgprot_t prot)
279 {
280         pmd_t *pmdp = pmd_off_k(virt);
281         pte_t *ptep;
282
283         if (pmd_none(*pmdp)) {
284                 ptep = alloc_bootmem_low_pages(2 * PTRS_PER_PTE *
285                                                sizeof(pte_t));
286
287                 __pmd_populate(pmdp, __pa(ptep) | prot_l1);
288         }
289         ptep = pte_offset_kernel(pmdp, virt);
290
291         set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, prot));
292 }
293
294 struct mem_types {
295         unsigned int    prot_pte;
296         unsigned int    prot_l1;
297         unsigned int    prot_sect;
298         unsigned int    domain;
299 };
300
301 static struct mem_types mem_types[] __initdata = {
302         [MT_DEVICE] = {
303                 .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
304                                 L_PTE_WRITE,
305                 .prot_l1   = PMD_TYPE_TABLE,
306                 .prot_sect = PMD_TYPE_SECT | PMD_SECT_UNCACHED |
307                                 PMD_SECT_AP_WRITE,
308                 .domain    = DOMAIN_IO,
309         },
310         [MT_CACHECLEAN] = {
311                 .prot_sect = PMD_TYPE_SECT,
312                 .domain    = DOMAIN_KERNEL,
313         },
314         [MT_MINICLEAN] = {
315                 .prot_sect = PMD_TYPE_SECT | PMD_SECT_MINICACHE,
316                 .domain    = DOMAIN_KERNEL,
317         },
318         [MT_LOW_VECTORS] = {
319                 .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
320                                 L_PTE_EXEC,
321                 .prot_l1   = PMD_TYPE_TABLE,
322                 .domain    = DOMAIN_USER,
323         },
324         [MT_HIGH_VECTORS] = {
325                 .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
326                                 L_PTE_USER | L_PTE_EXEC,
327                 .prot_l1   = PMD_TYPE_TABLE,
328                 .domain    = DOMAIN_USER,
329         },
330         [MT_MEMORY] = {
331                 .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE,
332                 .domain    = DOMAIN_KERNEL,
333         },
334         [MT_ROM] = {
335                 .prot_sect = PMD_TYPE_SECT,
336                 .domain    = DOMAIN_KERNEL,
337         },
338         [MT_IXP2000_DEVICE] = { /* IXP2400 requires XCB=101 for on-chip I/O */
339                 .prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
340                                 L_PTE_WRITE,
341                 .prot_l1   = PMD_TYPE_TABLE,
342                 .prot_sect = PMD_TYPE_SECT | PMD_SECT_UNCACHED |
343                                 PMD_SECT_AP_WRITE | PMD_SECT_BUFFERABLE |
344                                 PMD_SECT_TEX(1),
345                 .domain    = DOMAIN_IO,
346         }
347 };
348
349 /*
350  * Adjust the PMD section entries according to the CPU in use.
351  */
352 void __init build_mem_type_table(void)
353 {
354         struct cachepolicy *cp;
355         unsigned int cr = get_cr();
356         unsigned int user_pgprot, kern_pgprot;
357         int cpu_arch = cpu_architecture();
358         int i;
359
360 #if defined(CONFIG_CPU_DCACHE_DISABLE)
361         if (cachepolicy > CPOLICY_BUFFERED)
362                 cachepolicy = CPOLICY_BUFFERED;
363 #elif defined(CONFIG_CPU_DCACHE_WRITETHROUGH)
364         if (cachepolicy > CPOLICY_WRITETHROUGH)
365                 cachepolicy = CPOLICY_WRITETHROUGH;
366 #endif
367         if (cpu_arch < CPU_ARCH_ARMv5) {
368                 if (cachepolicy >= CPOLICY_WRITEALLOC)
369                         cachepolicy = CPOLICY_WRITEBACK;
370                 ecc_mask = 0;
371         }
372
373         if (cpu_arch <= CPU_ARCH_ARMv5TEJ) {
374                 for (i = 0; i < ARRAY_SIZE(mem_types); i++) {
375                         if (mem_types[i].prot_l1)
376                                 mem_types[i].prot_l1 |= PMD_BIT4;
377                         if (mem_types[i].prot_sect)
378                                 mem_types[i].prot_sect |= PMD_BIT4;
379                 }
380         }
381
382         cp = &cache_policies[cachepolicy];
383         kern_pgprot = user_pgprot = cp->pte;
384
385         /*
386          * ARMv6 and above have extended page tables.
387          */
388         if (cpu_arch >= CPU_ARCH_ARMv6 && (cr & CR_XP)) {
389                 /*
390                  * bit 4 becomes XN which we must clear for the
391                  * kernel memory mapping.
392                  */
393                 mem_types[MT_MEMORY].prot_sect &= ~PMD_BIT4;
394                 mem_types[MT_ROM].prot_sect &= ~PMD_BIT4;
395
396                 /*
397                  * Mark cache clean areas and XIP ROM read only
398                  * from SVC mode and no access from userspace.
399                  */
400                 mem_types[MT_ROM].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
401                 mem_types[MT_MINICLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
402                 mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE;
403
404                 /*
405                  * Mark the device area as "shared device"
406                  */
407                 mem_types[MT_DEVICE].prot_pte |= L_PTE_BUFFERABLE;
408                 mem_types[MT_DEVICE].prot_sect |= PMD_SECT_BUFFERED;
409
410                 /*
411                  * User pages need to be mapped with the ASID
412                  * (iow, non-global)
413                  */
414                 user_pgprot |= L_PTE_ASID;
415
416 #ifdef CONFIG_SMP
417                 /*
418                  * Mark memory with the "shared" attribute for SMP systems
419                  */
420                 user_pgprot |= L_PTE_SHARED;
421                 kern_pgprot |= L_PTE_SHARED;
422                 mem_types[MT_MEMORY].prot_sect |= PMD_SECT_S;
423 #endif
424         }
425
426         for (i = 0; i < 16; i++) {
427                 unsigned long v = pgprot_val(protection_map[i]);
428                 v = (v & ~(L_PTE_BUFFERABLE|L_PTE_CACHEABLE)) | user_pgprot;
429                 protection_map[i] = __pgprot(v);
430         }
431
432         mem_types[MT_LOW_VECTORS].prot_pte |= kern_pgprot;
433         mem_types[MT_HIGH_VECTORS].prot_pte |= kern_pgprot;
434
435         if (cpu_arch >= CPU_ARCH_ARMv5) {
436 #ifndef CONFIG_SMP
437                 /*
438                  * Only use write-through for non-SMP systems
439                  */
440                 mem_types[MT_LOW_VECTORS].prot_pte &= ~L_PTE_BUFFERABLE;
441                 mem_types[MT_HIGH_VECTORS].prot_pte &= ~L_PTE_BUFFERABLE;
442 #endif
443         } else {
444                 mem_types[MT_MINICLEAN].prot_sect &= ~PMD_SECT_TEX(1);
445         }
446
447         pgprot_kernel = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG |
448                                  L_PTE_DIRTY | L_PTE_WRITE |
449                                  L_PTE_EXEC | kern_pgprot);
450
451         mem_types[MT_LOW_VECTORS].prot_l1 |= ecc_mask;
452         mem_types[MT_HIGH_VECTORS].prot_l1 |= ecc_mask;
453         mem_types[MT_MEMORY].prot_sect |= ecc_mask | cp->pmd;
454         mem_types[MT_ROM].prot_sect |= cp->pmd;
455
456         switch (cp->pmd) {
457         case PMD_SECT_WT:
458                 mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_WT;
459                 break;
460         case PMD_SECT_WB:
461         case PMD_SECT_WBWA:
462                 mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_WB;
463                 break;
464         }
465         printk("Memory policy: ECC %sabled, Data cache %s\n",
466                 ecc_mask ? "en" : "dis", cp->policy);
467 }
468
469 #define vectors_base()  (vectors_high() ? 0xffff0000 : 0)
470
471 /*
472  * Create the page directory entries and any necessary
473  * page tables for the mapping specified by `md'.  We
474  * are able to cope here with varying sizes and address
475  * offsets, and we take full advantage of sections and
476  * supersections.
477  */
478 void __init create_mapping(struct map_desc *md)
479 {
480         unsigned long virt, length;
481         int prot_sect, prot_l1, domain;
482         pgprot_t prot_pte;
483         unsigned long off = (u32)__pfn_to_phys(md->pfn);
484
485         if (md->virtual != vectors_base() && md->virtual < TASK_SIZE) {
486                 printk(KERN_WARNING "BUG: not creating mapping for "
487                        "0x%08llx at 0x%08lx in user region\n",
488                        __pfn_to_phys((u64)md->pfn), md->virtual);
489                 return;
490         }
491
492         if ((md->type == MT_DEVICE || md->type == MT_ROM) &&
493             md->virtual >= PAGE_OFFSET && md->virtual < VMALLOC_END) {
494                 printk(KERN_WARNING "BUG: mapping for 0x%08llx at 0x%08lx "
495                        "overlaps vmalloc space\n",
496                        __pfn_to_phys((u64)md->pfn), md->virtual);
497         }
498
499         domain    = mem_types[md->type].domain;
500         prot_pte  = __pgprot(mem_types[md->type].prot_pte);
501         prot_l1   = mem_types[md->type].prot_l1 | PMD_DOMAIN(domain);
502         prot_sect = mem_types[md->type].prot_sect | PMD_DOMAIN(domain);
503
504         /*
505          * Catch 36-bit addresses
506          */
507         if(md->pfn >= 0x100000) {
508                 if(domain) {
509                         printk(KERN_ERR "MM: invalid domain in supersection "
510                                 "mapping for 0x%08llx at 0x%08lx\n",
511                                 __pfn_to_phys((u64)md->pfn), md->virtual);
512                         return;
513                 }
514                 if((md->virtual | md->length | __pfn_to_phys(md->pfn))
515                         & ~SUPERSECTION_MASK) {
516                         printk(KERN_ERR "MM: cannot create mapping for "
517                                 "0x%08llx at 0x%08lx invalid alignment\n",
518                                 __pfn_to_phys((u64)md->pfn), md->virtual);
519                         return;
520                 }
521
522                 /*
523                  * Shift bits [35:32] of address into bits [23:20] of PMD
524                  * (See ARMv6 spec).
525                  */
526                 off |= (((md->pfn >> (32 - PAGE_SHIFT)) & 0xF) << 20);
527         }
528
529         virt   = md->virtual;
530         off   -= virt;
531         length = md->length;
532
533         if (mem_types[md->type].prot_l1 == 0 &&
534             (virt & 0xfffff || (virt + off) & 0xfffff || (virt + length) & 0xfffff)) {
535                 printk(KERN_WARNING "BUG: map for 0x%08lx at 0x%08lx can not "
536                        "be mapped using pages, ignoring.\n",
537                        __pfn_to_phys(md->pfn), md->virtual);
538                 return;
539         }
540
541         while ((virt & 0xfffff || (virt + off) & 0xfffff) && length >= PAGE_SIZE) {
542                 alloc_init_page(virt, virt + off, prot_l1, prot_pte);
543
544                 virt   += PAGE_SIZE;
545                 length -= PAGE_SIZE;
546         }
547
548         /* N.B. ARMv6 supersections are only defined to work with domain 0.
549          *      Since domain assignments can in fact be arbitrary, the
550          *      'domain == 0' check below is required to insure that ARMv6
551          *      supersections are only allocated for domain 0 regardless
552          *      of the actual domain assignments in use.
553          */
554         if (cpu_architecture() >= CPU_ARCH_ARMv6 && domain == 0) {
555                 /*
556                  * Align to supersection boundary if !high pages.
557                  * High pages have already been checked for proper
558                  * alignment above and they will fail the SUPSERSECTION_MASK
559                  * check because of the way the address is encoded into
560                  * offset.
561                  */
562                 if (md->pfn <= 0x100000) {
563                         while ((virt & ~SUPERSECTION_MASK ||
564                                 (virt + off) & ~SUPERSECTION_MASK) &&
565                                 length >= (PGDIR_SIZE / 2)) {
566                                 alloc_init_section(virt, virt + off, prot_sect);
567
568                                 virt   += (PGDIR_SIZE / 2);
569                                 length -= (PGDIR_SIZE / 2);
570                         }
571                 }
572
573                 while (length >= SUPERSECTION_SIZE) {
574                         alloc_init_supersection(virt, virt + off, prot_sect);
575
576                         virt   += SUPERSECTION_SIZE;
577                         length -= SUPERSECTION_SIZE;
578                 }
579         }
580
581         /*
582          * A section mapping covers half a "pgdir" entry.
583          */
584         while (length >= (PGDIR_SIZE / 2)) {
585                 alloc_init_section(virt, virt + off, prot_sect);
586
587                 virt   += (PGDIR_SIZE / 2);
588                 length -= (PGDIR_SIZE / 2);
589         }
590
591         while (length >= PAGE_SIZE) {
592                 alloc_init_page(virt, virt + off, prot_l1, prot_pte);
593
594                 virt   += PAGE_SIZE;
595                 length -= PAGE_SIZE;
596         }
597 }
598
599 /*
600  * In order to soft-boot, we need to insert a 1:1 mapping in place of
601  * the user-mode pages.  This will then ensure that we have predictable
602  * results when turning the mmu off
603  */
604 void setup_mm_for_reboot(char mode)
605 {
606         unsigned long base_pmdval;
607         pgd_t *pgd;
608         int i;
609
610         if (current->mm && current->mm->pgd)
611                 pgd = current->mm->pgd;
612         else
613                 pgd = init_mm.pgd;
614
615         base_pmdval = PMD_SECT_AP_WRITE | PMD_SECT_AP_READ | PMD_TYPE_SECT;
616         if (cpu_architecture() <= CPU_ARCH_ARMv5TEJ)
617                 base_pmdval |= PMD_BIT4;
618
619         for (i = 0; i < FIRST_USER_PGD_NR + USER_PTRS_PER_PGD; i++, pgd++) {
620                 unsigned long pmdval = (i << PGDIR_SHIFT) | base_pmdval;
621                 pmd_t *pmd;
622
623                 pmd = pmd_off(pgd, i << PGDIR_SHIFT);
624                 pmd[0] = __pmd(pmdval);
625                 pmd[1] = __pmd(pmdval + (1 << (PGDIR_SHIFT - 1)));
626                 flush_pmd_entry(pmd);
627         }
628 }
629
630 /*
631  * Create the architecture specific mappings
632  */
633 void __init iotable_init(struct map_desc *io_desc, int nr)
634 {
635         int i;
636
637         for (i = 0; i < nr; i++)
638                 create_mapping(io_desc + i);
639 }