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 * Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk). 15 * 16 * Derived from "arch/i386/mm/init.c" 17 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 18 * 19 * This program is free software; you can redistribute it and/or 20 * modify it under the terms of the GNU General Public License 21 * as published by the Free Software Foundation; either version 22 * 2 of the License, or (at your option) any later version. 23 * 24 */ 25 26#include <linux/mm.h> 27#include <linux/init.h> 28 29#include <asm/mmu_context.h> 30#include <asm/tlbflush.h> 31 32unsigned long next_mmu_context; 33unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1]; 34#ifdef FEW_CONTEXTS 35atomic_t nr_free_contexts; 36struct mm_struct *context_mm[LAST_CONTEXT+1]; 37void steal_context(void); 38#endif /* FEW_CONTEXTS */ 39 40/* 41 * Initialize the context management stuff. 42 */ 43void __init 44mmu_context_init(void) 45{ 46 /* 47 * Some processors have too few contexts to reserve one for 48 * init_mm, and require using context 0 for a normal task. 49 * Other processors reserve the use of context zero for the kernel. 50 * This code assumes FIRST_CONTEXT < 32. 51 */ 52 context_map[0] = (1 << FIRST_CONTEXT) - 1; 53 next_mmu_context = FIRST_CONTEXT; 54#ifdef FEW_CONTEXTS 55 atomic_set(&nr_free_contexts, LAST_CONTEXT - FIRST_CONTEXT + 1); 56#endif /* FEW_CONTEXTS */ 57} 58 59#ifdef FEW_CONTEXTS 60/* 61 * Steal a context from a task that has one at the moment. 62 * This is only used on 8xx and 4xx and we presently assume that 63 * they don't do SMP. If they do then this will have to check 64 * whether the MM we steal is in use. 65 * We also assume that this is only used on systems that don't 66 * use an MMU hash table - this is true for 8xx and 4xx. 67 * This isn't an LRU system, it just frees up each context in 68 * turn (sort-of pseudo-random replacement :). This would be the 69 * place to implement an LRU scheme if anyone was motivated to do it. 70 * -- paulus 71 */ 72void 73steal_context(void) 74{ 75 struct mm_struct *mm; 76 77 /* free up context `next_mmu_context' */ 78 /* if we shouldn't free context 0, don't... */ 79 if (next_mmu_context < FIRST_CONTEXT) 80 next_mmu_context = FIRST_CONTEXT; 81 mm = context_mm[next_mmu_context]; 82 flush_tlb_mm(mm); 83 destroy_context(mm); 84} 85#endif /* FEW_CONTEXTS */ 86