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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
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
25#include <linux/mm.h>
26#include <linux/init.h>
27
28#include <asm/mmu_context.h>
29#include <asm/tlbflush.h>
30
31unsigned long next_mmu_context;
32unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
33#ifdef FEW_CONTEXTS
34atomic_t nr_free_contexts;
35struct mm_struct *context_mm[LAST_CONTEXT+1];
36void steal_context(void);
37#endif /* FEW_CONTEXTS */
38
39/*
40 * Initialize the context management stuff.
41 */
42void __init
43mmu_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 */
71void
72steal_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 */