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1 | /* |
2 | * This file contains the routines for handling the MMU on those | |
3 | * PowerPC implementations where the MMU substantially follows the | |
4 | * architecture specification. This includes the 6xx, 7xx, 7xxx, | |
5 | * 8260, and POWER3 implementations but excludes the 8xx and 4xx. | |
6 | * -- paulus | |
7 | * | |
8 | * Derived from arch/ppc/mm/init.c: | |
9 | * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) | |
10 | * | |
11 | * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au) | |
12 | * and Cort Dougan (PReP) (cort@cs.nmt.edu) | |
13 | * Copyright (C) 1996 Paul Mackerras | |
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14 | * |
15 | * Derived from "arch/i386/mm/init.c" | |
16 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds | |
17 | * | |
18 | * This program is free software; you can redistribute it and/or | |
19 | * modify it under the terms of the GNU General Public License | |
20 | * as published by the Free Software Foundation; either version | |
21 | * 2 of the License, or (at your option) any later version. | |
22 | * | |
23 | */ | |
24 | ||
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25 | #include <linux/mm.h> |
26 | #include <linux/init.h> | |
27 | ||
28 | #include <asm/mmu_context.h> | |
29 | #include <asm/tlbflush.h> | |
30 | ||
6218a761 | 31 | unsigned long next_mmu_context; |
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32 | unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1]; |
33 | #ifdef FEW_CONTEXTS | |
34 | atomic_t nr_free_contexts; | |
35 | struct mm_struct *context_mm[LAST_CONTEXT+1]; | |
36 | void steal_context(void); | |
37 | #endif /* FEW_CONTEXTS */ | |
38 | ||
39 | /* | |
40 | * Initialize the context management stuff. | |
41 | */ | |
42 | void __init | |
43 | mmu_context_init(void) | |
44 | { | |
45 | /* | |
46 | * Some processors have too few contexts to reserve one for | |
47 | * init_mm, and require using context 0 for a normal task. | |
48 | * Other processors reserve the use of context zero for the kernel. | |
49 | * This code assumes FIRST_CONTEXT < 32. | |
50 | */ | |
51 | context_map[0] = (1 << FIRST_CONTEXT) - 1; | |
52 | next_mmu_context = FIRST_CONTEXT; | |
53 | #ifdef FEW_CONTEXTS | |
54 | atomic_set(&nr_free_contexts, LAST_CONTEXT - FIRST_CONTEXT + 1); | |
55 | #endif /* FEW_CONTEXTS */ | |
56 | } | |
57 | ||
58 | #ifdef FEW_CONTEXTS | |
59 | /* | |
60 | * Steal a context from a task that has one at the moment. | |
61 | * This is only used on 8xx and 4xx and we presently assume that | |
62 | * they don't do SMP. If they do then this will have to check | |
63 | * whether the MM we steal is in use. | |
64 | * We also assume that this is only used on systems that don't | |
65 | * use an MMU hash table - this is true for 8xx and 4xx. | |
66 | * This isn't an LRU system, it just frees up each context in | |
67 | * turn (sort-of pseudo-random replacement :). This would be the | |
68 | * place to implement an LRU scheme if anyone was motivated to do it. | |
69 | * -- paulus | |
70 | */ | |
71 | void | |
72 | steal_context(void) | |
73 | { | |
74 | struct mm_struct *mm; | |
75 | ||
76 | /* free up context `next_mmu_context' */ | |
77 | /* if we shouldn't free context 0, don't... */ | |
78 | if (next_mmu_context < FIRST_CONTEXT) | |
79 | next_mmu_context = FIRST_CONTEXT; | |
80 | mm = context_mm[next_mmu_context]; | |
81 | flush_tlb_mm(mm); | |
82 | destroy_context(mm); | |
83 | } | |
84 | #endif /* FEW_CONTEXTS */ |