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
  23 #include <asm/mmu_context.h>
  24
  25 static DEFINE_SPINLOCK(mmu_context_lock);
  26 static DEFINE_IDR(mmu_context_idr);
  27
  28 /*
  29  * The proto-VSID space has 2^35 - 1 segments available for user mappings.
  30  * Each segment contains 2^28 bytes.  Each context maps 2^44 bytes,
  31  * so we can support 2^19-1 contexts (19 == 35 + 28 - 44).
  32  */
  33 #define NO_CONTEXT      0
  34 #define MAX_CONTEXT     ((1UL << 19) - 1)
  35
  36 int __init_new_context(void)
  37 {
  38         int index;
  39         int err;
  40
  41 again:
  42         if (!idr_pre_get(&mmu_context_idr, GFP_KERNEL))
  43                 return -ENOMEM;
  44
  45         spin_lock(&mmu_context_lock);
  46         err = idr_get_new_above(&mmu_context_idr, NULL, 1, &index);
  47         spin_unlock(&mmu_context_lock);
  48
  49         if (err == -EAGAIN)
  50                 goto again;
  51         else if (err)
  52                 return err;
  53
  54         if (index > MAX_CONTEXT) {
  55                 spin_lock(&mmu_context_lock);
  56                 idr_remove(&mmu_context_idr, index);
  57                 spin_unlock(&mmu_context_lock);
  58                 return -ENOMEM;
  59         }
  60
  61         return index;
  62 }
  63 EXPORT_SYMBOL_GPL(__init_new_context);
  64
  65 int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  66 {
  67         int index;
  68
  69         index = __init_new_context();
  70         if (index < 0)
  71                 return index;
  72
  73         /* The old code would re-promote on fork, we don't do that
  74          * when using slices as it could cause problem promoting slices
  75          * that have been forced down to 4K
  76          */
  77         if (slice_mm_new_context(mm))
  78                 slice_set_user_psize(mm, mmu_virtual_psize);
  79         mm->context.id = index;
  80
  81         return 0;
  82 }
  83
  84 void __destroy_context(int context_id)
  85 {
  86         spin_lock(&mmu_context_lock);
  87         idr_remove(&mmu_context_idr, context_id);
  88         spin_unlock(&mmu_context_lock);
  89 }
  90 EXPORT_SYMBOL_GPL(__destroy_context);
  91
  92 void destroy_context(struct mm_struct *mm)
  93 {
  94         __destroy_context(mm->context.id);
  95         mm->context.id = NO_CONTEXT;
  96 }