LXR linux/arch/powerpc/mm/mmu_context

   1/*
   2 *  MMU context allocation for 64-bit kernels.
   3 *
   4 *  Copyright (C) 2004 Anton Blanchard, IBM Corp. <anton@samba.org>
   5 *
   6 *  This program is free software; you can redistribute it and/or
   7 *  modify it under the terms of the GNU General Public License
   8 *  as published by the Free Software Foundation; either version
   9 *  2 of the License, or (at your option) any later version.
  10 *
  11 */
  12
  13#include <linux/sched.h>
  14#include <linux/kernel.h>
  15#include <linux/errno.h>
  16#include <linux/string.h>
  17#include <linux/types.h>
  18#include <linux/mm.h>
  19#include <linux/spinlock.h>
  20#include <linux/idr.h>
  21#include <linux/module.h>
  22#include <linux/gfp.h>
  23
  24#include <asm/mmu_context.h>
  25
  26static DEFINE_SPINLOCK(mmu_context_lock);
  27static DEFINE_IDA(mmu_context_ida);
  28
  29/*
  30 * The proto-VSID space has 2^35 - 1 segments available for user mappings.
  31 * Each segment contains 2^28 bytes.  Each context maps 2^44 bytes,
  32 * so we can support 2^19-1 contexts (19 == 35 + 28 - 44).
  33 */
  34#define NO_CONTEXT      0
  35#define MAX_CONTEXT     ((1UL << 19) - 1)
  36
  37int __init_new_context(void)
  38{
  39        int index;
  40        int err;
  41
  42again:
  43        if (!ida_pre_get(&mmu_context_ida, GFP_KERNEL))
  44                return -ENOMEM;
  45
  46        spin_lock(&mmu_context_lock);
  47        err = ida_get_new_above(&mmu_context_ida, 1, &index);
  48        spin_unlock(&mmu_context_lock);
  49
  50        if (err == -EAGAIN)
  51                goto again;
  52        else if (err)
  53                return err;
  54
  55        if (index > MAX_CONTEXT) {
  56                spin_lock(&mmu_context_lock);
  57                ida_remove(&mmu_context_ida, index);
  58                spin_unlock(&mmu_context_lock);
  59                return -ENOMEM;
  60        }
  61
  62        return index;
  63}
  64EXPORT_SYMBOL_GPL(__init_new_context);
  65
  66int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  67{
  68        int index;
  69
  70        index = __init_new_context();
  71        if (index < 0)
  72                return index;
  73
  74        /* The old code would re-promote on fork, we don't do that
  75         * when using slices as it could cause problem promoting slices
  76         * that have been forced down to 4K
  77         */
  78        if (slice_mm_new_context(mm))
  79                slice_set_user_psize(mm, mmu_virtual_psize);
  80        subpage_prot_init_new_context(mm);
  81        mm->context.id = index;
  82
  83        return 0;
  84}
  85
  86void __destroy_context(int context_id)
  87{
  88        spin_lock(&mmu_context_lock);
  89        ida_remove(&mmu_context_ida, context_id);
  90        spin_unlock(&mmu_context_lock);
  91}
  92EXPORT_SYMBOL_GPL(__destroy_context);
  93
  94void destroy_context(struct mm_struct *mm)
  95{
  96        __destroy_context(mm->context.id);
  97        subpage_prot_free(mm);
  98        mm->context.id = NO_CONTEXT;
  99}
 100