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/*
* 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
*
* 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/mm.h>
#include <linux/init.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
unsigned long 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 */
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