1 /* 2 * This file contains the routines for handling the MMU. 3 * 4 * Copyright (C) 2007 Xilinx, Inc. All rights reserved. 5 * 6 * Derived from arch/ppc/mm/4xx_mmu.c: 7 * -- paulus 8 * 9 * Derived from arch/ppc/mm/init.c: 10 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) 11 * 12 * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au) 13 * and Cort Dougan (PReP) (cort@cs.nmt.edu) 14 * Copyright (C) 1996 Paul Mackerras 15 * Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk). 16 * 17 * Derived from "arch/i386/mm/init.c" 18 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 19 * 20 * This program is free software; you can redistribute it and/or 21 * modify it under the terms of the GNU General Public License 22 * as published by the Free Software Foundation; either version 23 * 2 of the License, or (at your option) any later version. 24 * 25 */ 26 27 #include <linux/mm.h> 28 #include <linux/init.h> 29 30 #include <asm/tlbflush.h> 31 #include <asm/mmu_context.h> 32 33 mm_context_t next_mmu_context; 34 unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1]; 35 atomic_t nr_free_contexts; 36 struct mm_struct *context_mm[LAST_CONTEXT+1]; 37 38 /* 39 * Initialize the context management stuff. 40 */ 41 void __init mmu_context_init(void) 42 { 43 /* 44 * The use of context zero is reserved for the kernel. 45 * This code assumes FIRST_CONTEXT < 32. 46 */ 47 context_map[0] = (1 << FIRST_CONTEXT) - 1; 48 next_mmu_context = FIRST_CONTEXT; 49 atomic_set(&nr_free_contexts, LAST_CONTEXT - FIRST_CONTEXT + 1); 50 } 51 52 /* 53 * Steal a context from a task that has one at the moment. 54 * 55 * This isn't an LRU system, it just frees up each context in 56 * turn (sort-of pseudo-random replacement :). This would be the 57 * place to implement an LRU scheme if anyone were motivated to do it. 58 */ 59 void steal_context(void) 60 { 61 struct mm_struct *mm; 62 63 /* free up context `next_mmu_context' */ 64 /* if we shouldn't free context 0, don't... */ 65 if (next_mmu_context < FIRST_CONTEXT) 66 next_mmu_context = FIRST_CONTEXT; 67 mm = context_mm[next_mmu_context]; 68 flush_tlb_mm(mm); 69 destroy_context(mm); 70 } 71