arch/microblaze/mm/mmu_context.c

   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 }