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Diffstat (limited to 'arch/ppc/mm/mmu_context.c')
| -rw-r--r-- | arch/ppc/mm/mmu_context.c | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/arch/ppc/mm/mmu_context.c b/arch/ppc/mm/mmu_context.c new file mode 100644 index 000000000000..a8816e0f6a86 --- /dev/null +++ b/arch/ppc/mm/mmu_context.c @@ -0,0 +1,86 @@ +/* + * This file contains the routines for handling the MMU on those + * PowerPC implementations where the MMU substantially follows the + * architecture specification. This includes the 6xx, 7xx, 7xxx, + * 8260, and POWER3 implementations but excludes the 8xx and 4xx. + * -- paulus + * + * Derived from arch/ppc/mm/init.c: + * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) + * + * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au) + * and Cort Dougan (PReP) (cort@cs.nmt.edu) + * Copyright (C) 1996 Paul Mackerras + * Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk). + * + * Derived from "arch/i386/mm/init.c" + * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + * + */ + +#include <linux/config.h> +#include <linux/mm.h> +#include <linux/init.h> + +#include <asm/mmu_context.h> +#include <asm/tlbflush.h> + +mm_context_t next_mmu_context; +unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1]; +#ifdef FEW_CONTEXTS +atomic_t nr_free_contexts; +struct mm_struct *context_mm[LAST_CONTEXT+1]; +void steal_context(void); +#endif /* FEW_CONTEXTS */ + +/* + * Initialize the context management stuff. + */ +void __init +mmu_context_init(void) +{ + /* + * Some processors have too few contexts to reserve one for + * init_mm, and require using context 0 for a normal task. + * Other processors reserve the use of context zero for the kernel. + * This code assumes FIRST_CONTEXT < 32. + */ + context_map[0] = (1 << FIRST_CONTEXT) - 1; + next_mmu_context = FIRST_CONTEXT; +#ifdef FEW_CONTEXTS + atomic_set(&nr_free_contexts, LAST_CONTEXT - FIRST_CONTEXT + 1); +#endif /* FEW_CONTEXTS */ +} + +#ifdef FEW_CONTEXTS +/* + * Steal a context from a task that has one at the moment. + * This is only used on 8xx and 4xx and we presently assume that + * they don't do SMP. If they do then this will have to check + * whether the MM we steal is in use. + * We also assume that this is only used on systems that don't + * use an MMU hash table - this is true for 8xx and 4xx. + * This isn't an LRU system, it just frees up each context in + * turn (sort-of pseudo-random replacement :). This would be the + * place to implement an LRU scheme if anyone was motivated to do it. + * -- paulus + */ +void +steal_context(void) +{ + struct mm_struct *mm; + + /* free up context `next_mmu_context' */ + /* if we shouldn't free context 0, don't... */ + if (next_mmu_context < FIRST_CONTEXT) + next_mmu_context = FIRST_CONTEXT; + mm = context_mm[next_mmu_context]; + flush_tlb_mm(mm); + destroy_context(mm); +} +#endif /* FEW_CONTEXTS */ |