arch/powerpc/mm/mmu_context_hash64.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 #include <linux/module.h>
  22 #include <linux/gfp.h>
  23
  24 #include <asm/mmu_context.h>
  25
  26 static DEFINE_SPINLOCK(mmu_context_lock);
  27 static 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
  37 int __init_new_context(void)
  38 {
  39         int index;
  40         int err;
  41
  42 again:
  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 }
  64 EXPORT_SYMBOL_GPL(__init_new_context);
  65
  66 int 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
  86 void __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 }
  92 EXPORT_SYMBOL_GPL(__destroy_context);
  93
  94 void 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 }