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
  22 #include <asm/mmu_context.h>
  23
  24 static DEFINE_SPINLOCK(mmu_context_lock);
  25 static 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
  35 int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  36 {
  37         int index;
  38         int err;
  39
  40 again:
  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
  71 void 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 }