| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * linux/arch/arm/mm/minicache.c |
| 3 | * |
| 4 | * Copyright (C) 2001 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 | * This handles the mini data cache, as found on SA11x0 and XScale |
| 11 | * processors. When we copy a user page page, we map it in such a way |
| 12 | * that accesses to this page will not touch the main data cache, but |
| 13 | * will be cached in the mini data cache. This prevents us thrashing |
| 14 | * the main data cache on page faults. |
| 15 | */ |
| 16 | #include <linux/init.h> |
| 17 | #include <linux/mm.h> |
| 18 | |
| 19 | #include <asm/page.h> |
| 20 | #include <asm/pgtable.h> |
| 21 | #include <asm/tlbflush.h> |
| 22 | |
| 23 | /* |
| 24 | * 0xffff8000 to 0xffffffff is reserved for any ARM architecture |
| 25 | * specific hacks for copying pages efficiently. |
| 26 | */ |
| 27 | #define minicache_address (0xffff8000) |
| 28 | #define minicache_pgprot __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | \ |
| 29 | L_PTE_CACHEABLE) |
| 30 | |
| 31 | static pte_t *minicache_pte; |
| 32 | |
| 33 | /* |
| 34 | * Note that this is intended to be called only from the copy_user_page |
| 35 | * asm code; anything else will require special locking to prevent the |
| 36 | * mini-cache space being re-used. (Note: probably preempt unsafe). |
| 37 | * |
| 38 | * We rely on the fact that the minicache is 2K, and we'll be pushing |
| 39 | * 4K of data through it, so we don't actually have to specifically |
| 40 | * flush the minicache when we change the mapping. |
| 41 | * |
| 42 | * Note also: assert(PAGE_OFFSET <= virt < high_memory). |
| 43 | * Unsafe: preempt, kmap. |
| 44 | */ |
| 45 | unsigned long map_page_minicache(unsigned long virt) |
| 46 | { |
| 47 | set_pte(minicache_pte, pfn_pte(__pa(virt) >> PAGE_SHIFT, minicache_pgprot)); |
| 48 | flush_tlb_kernel_page(minicache_address); |
| 49 | |
| 50 | return minicache_address; |
| 51 | } |
| 52 | |
| 53 | static int __init minicache_init(void) |
| 54 | { |
| 55 | pgd_t *pgd; |
| 56 | pmd_t *pmd; |
| 57 | |
| 58 | spin_lock(&init_mm.page_table_lock); |
| 59 | |
| 60 | pgd = pgd_offset_k(minicache_address); |
| 61 | pmd = pmd_alloc(&init_mm, pgd, minicache_address); |
| 62 | if (!pmd) |
| 63 | BUG(); |
| 64 | minicache_pte = pte_alloc_kernel(&init_mm, pmd, minicache_address); |
| 65 | if (!minicache_pte) |
| 66 | BUG(); |
| 67 | |
| 68 | spin_unlock(&init_mm.page_table_lock); |
| 69 | |
| 70 | return 0; |
| 71 | } |
| 72 | |
| 73 | core_initcall(minicache_init); |