Paul Mackerras | 14cf11a | 2005-09-26 16:04:21 +1000 | [diff] [blame] | 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 |
Paul Mackerras | 14cf11a | 2005-09-26 16:04:21 +1000 | [diff] [blame] | 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 | |
Paul Mackerras | 14cf11a | 2005-09-26 16:04:21 +1000 | [diff] [blame] | 25 | #include <linux/mm.h> |
| 26 | #include <linux/init.h> |
| 27 | |
| 28 | #include <asm/mmu_context.h> |
| 29 | #include <asm/tlbflush.h> |
| 30 | |
Paul Mackerras | 6218a76 | 2006-06-11 14:15:17 +1000 | [diff] [blame] | 31 | unsigned long next_mmu_context; |
Paul Mackerras | 14cf11a | 2005-09-26 16:04:21 +1000 | [diff] [blame] | 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 */ |