Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * linux/arch/cris/mm/tlb.c |
| 3 | * |
| 4 | * Copyright (C) 2000, 2001 Axis Communications AB |
| 5 | * |
| 6 | * Authors: Bjorn Wesen (bjornw@axis.com) |
| 7 | * |
| 8 | */ |
| 9 | |
| 10 | #include <linux/init.h> |
| 11 | #include <asm/tlb.h> |
| 12 | |
| 13 | #define D(x) |
| 14 | |
| 15 | /* The TLB can host up to 64 different mm contexts at the same time. |
| 16 | * The running context is R_MMU_CONTEXT, and each TLB entry contains a |
| 17 | * page_id that has to match to give a hit. In page_id_map, we keep track |
| 18 | * of which mm's we have assigned which page_id's, so that we know when |
| 19 | * to invalidate TLB entries. |
| 20 | * |
| 21 | * The last page_id is never running - it is used as an invalid page_id |
| 22 | * so we can make TLB entries that will never match. |
| 23 | * |
| 24 | * Notice that we need to make the flushes atomic, otherwise an interrupt |
| 25 | * handler that uses vmalloced memory might cause a TLB load in the middle |
| 26 | * of a flush causing. |
| 27 | */ |
| 28 | |
| 29 | struct mm_struct *page_id_map[NUM_PAGEID]; |
| 30 | static int map_replace_ptr = 1; /* which page_id_map entry to replace next */ |
| 31 | |
| 32 | /* |
| 33 | * Initialize the context related info for a new mm_struct |
| 34 | * instance. |
| 35 | */ |
| 36 | |
| 37 | int |
| 38 | init_new_context(struct task_struct *tsk, struct mm_struct *mm) |
| 39 | { |
| 40 | mm->context = NO_CONTEXT; |
| 41 | return 0; |
| 42 | } |
| 43 | |
| 44 | /* the following functions are similar to those used in the PPC port */ |
| 45 | |
| 46 | static inline void |
| 47 | alloc_context(struct mm_struct *mm) |
| 48 | { |
| 49 | struct mm_struct *old_mm; |
| 50 | |
| 51 | D(printk("tlb: alloc context %d (%p)\n", map_replace_ptr, mm)); |
| 52 | |
| 53 | /* did we replace an mm ? */ |
| 54 | |
| 55 | old_mm = page_id_map[map_replace_ptr]; |
| 56 | |
| 57 | if(old_mm) { |
| 58 | /* throw out any TLB entries belonging to the mm we replace |
| 59 | * in the map |
| 60 | */ |
| 61 | flush_tlb_mm(old_mm); |
| 62 | |
| 63 | old_mm->context = NO_CONTEXT; |
| 64 | } |
| 65 | |
| 66 | /* insert it into the page_id_map */ |
| 67 | |
| 68 | mm->context = map_replace_ptr; |
| 69 | page_id_map[map_replace_ptr] = mm; |
| 70 | |
| 71 | map_replace_ptr++; |
| 72 | |
| 73 | if(map_replace_ptr == INVALID_PAGEID) |
| 74 | map_replace_ptr = 0; /* wrap around */ |
| 75 | } |
| 76 | |
| 77 | /* |
| 78 | * if needed, get a new MMU context for the mm. otherwise nothing is done. |
| 79 | */ |
| 80 | |
| 81 | void |
| 82 | get_mmu_context(struct mm_struct *mm) |
| 83 | { |
| 84 | if(mm->context == NO_CONTEXT) |
| 85 | alloc_context(mm); |
| 86 | } |
| 87 | |
| 88 | /* called by __exit_mm to destroy the used MMU context if any before |
| 89 | * destroying the mm itself. this is only called when the last user of the mm |
| 90 | * drops it. |
| 91 | * |
| 92 | * the only thing we really need to do here is mark the used PID slot |
| 93 | * as empty. |
| 94 | */ |
| 95 | |
| 96 | void |
| 97 | destroy_context(struct mm_struct *mm) |
| 98 | { |
| 99 | if(mm->context != NO_CONTEXT) { |
| 100 | D(printk("destroy_context %d (%p)\n", mm->context, mm)); |
| 101 | flush_tlb_mm(mm); /* TODO this might be redundant ? */ |
| 102 | page_id_map[mm->context] = NULL; |
| 103 | /* mm->context = NO_CONTEXT; redundant.. mm will be freed */ |
| 104 | } |
| 105 | } |
| 106 | |
| 107 | /* called once during VM initialization, from init.c */ |
| 108 | |
| 109 | void __init |
| 110 | tlb_init(void) |
| 111 | { |
| 112 | int i; |
| 113 | |
| 114 | /* clear the page_id map */ |
| 115 | |
| 116 | for (i = 1; i < sizeof (page_id_map) / sizeof (page_id_map[0]); i++) |
| 117 | page_id_map[i] = NULL; |
| 118 | |
| 119 | /* invalidate the entire TLB */ |
| 120 | |
| 121 | flush_tlb_all(); |
| 122 | |
| 123 | /* the init_mm has context 0 from the boot */ |
| 124 | |
| 125 | page_id_map[0] = &init_mm; |
| 126 | } |