release/src-rt-6.x/linux/linux-2.6/arch/powerpc/mm/mmu_context_64.c

   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
  24 static DEFINE_SPINLOCK(mmu_context_lock);
  25 static DEFINE_IDR(mmu_context_idr);
  26
  27 int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  28 {
  29         int index;
  30         int err;
  31         int new_context = (mm->context.id == 0);
  32
  33 again:
  34         if (!idr_pre_get(&mmu_context_idr, GFP_KERNEL))
  35                 return -ENOMEM;
  36
  37         spin_lock(&mmu_context_lock);
  38         err = idr_get_new_above(&mmu_context_idr, NULL, 1, &index);
  39         spin_unlock(&mmu_context_lock);
  40
  41         if (err == -EAGAIN)
  42                 goto again;
  43         else if (err)
  44                 return err;
  45
  46         if (index > MAX_CONTEXT) {
  47                 spin_lock(&mmu_context_lock);
  48                 idr_remove(&mmu_context_idr, index);
  49                 spin_unlock(&mmu_context_lock);
  50                 return -ENOMEM;
  51         }
  52
  53         mm->context.id = index;
  54 #ifdef CONFIG_PPC_MM_SLICES
  55         /* The old code would re-promote on fork, we don't do that
  56          * when using slices as it could cause problem promoting slices
  57          * that have been forced down to 4K
  58          */
  59         if (new_context)
  60                 slice_set_user_psize(mm, mmu_virtual_psize);
  61 #else
  62         mm->context.user_psize = mmu_virtual_psize;
  63         mm->context.sllp = SLB_VSID_USER |
  64                 mmu_psize_defs[mmu_virtual_psize].sllp;
  65 #endif
  66
  67         return 0;
  68 }
  69
  70 void destroy_context(struct mm_struct *mm)
  71 {
  72         spin_lock(&mmu_context_lock);
  73         idr_remove(&mmu_context_idr, mm->context.id);
  74         spin_unlock(&mmu_context_lock);
  75
  76         mm->context.id = NO_CONTEXT;
  77 }