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
  22#include <asm/mmu_context.h>
  23
  24static DEFINE_SPINLOCK(mmu_context_lock);
  25static DEFINE_IDR(mmu_context_idr);
  26
  27/*
  28 * The proto-VSID space has 2^35 - 1 segments available for user mappings.
  29 * Each segment contains 2^28 bytes.  Each context maps 2^44 bytes,
  30 * so we can support 2^19-1 contexts (19 == 35 + 28 - 44).
  31 */
  32#define NO_CONTEXT      0
  33#define MAX_CONTEXT     ((1UL << 19) - 1)
  34
  35int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  36{
  37        int index;
  38        int err;
  39
  40again:
  41        if (!idr_pre_get(&mmu_context_idr, GFP_KERNEL))
  42                return -ENOMEM;
  43
  44        spin_lock(&mmu_context_lock);
  45        err = idr_get_new_above(&mmu_context_idr, NULL, 1, &index);
  46        spin_unlock(&mmu_context_lock);
  47
  48        if (err == -EAGAIN)
  49                goto again;
  50        else if (err)
  51                return err;
  52
  53        if (index > MAX_CONTEXT) {
  54                spin_lock(&mmu_context_lock);
  55                idr_remove(&mmu_context_idr, index);
  56                spin_unlock(&mmu_context_lock);
  57                return -ENOMEM;
  58        }
  59
  60        /* The old code would re-promote on fork, we don't do that
  61         * when using slices as it could cause problem promoting slices
  62         * that have been forced down to 4K
  63         */
  64        if (slice_mm_new_context(mm))
  65                slice_set_user_psize(mm, mmu_virtual_psize);
  66        mm->context.id = index;
  67
  68        return 0;
  69}
  70
  71void destroy_context(struct mm_struct *mm)
  72{
  73        spin_lock(&mmu_context_lock);
  74        idr_remove(&mmu_context_idr, mm->context.id);
  75        spin_unlock(&mmu_context_lock);
  76
  77        mm->context.id = NO_CONTEXT;
  78}
  79