arch/cris/mm/tlb.c

   1 /*
   2  *  linux/arch/cris/mm/tlb.c
   3  *
   4  *  Copyright (C) 2000, 2001  Axis Communications AB
   5  *
   6  *  Authors:   Bjorn Wesen (bjornw@axis.com)
   7  *
   8  */
   9
  10 #include <linux/init.h>
  11 #include <asm/tlb.h>
  12
  13 #define D(x)
  14
  15 /* The TLB can host up to 64 different mm contexts at the same time.
  16  * The running context is R_MMU_CONTEXT, and each TLB entry contains a
  17  * page_id that has to match to give a hit. In page_id_map, we keep track
  18  * of which mm's we have assigned which page_id's, so that we know when
  19  * to invalidate TLB entries.
  20  *
  21  * The last page_id is never running - it is used as an invalid page_id
  22  * so we can make TLB entries that will never match.
  23  *
  24  * Notice that we need to make the flushes atomic, otherwise an interrupt
  25  * handler that uses vmalloced memory might cause a TLB load in the middle
  26  * of a flush causing.
  27  */
  28
  29 struct mm_struct *page_id_map[NUM_PAGEID];
  30 static int map_replace_ptr = 1;  /* which page_id_map entry to replace next */
  31
  32 /*
  33  * Initialize the context related info for a new mm_struct
  34  * instance.
  35  */
  36
  37 int
  38 init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  39 {
  40         mm->context = NO_CONTEXT;
  41         return 0;
  42 }
  43
  44 /* the following functions are similar to those used in the PPC port */
  45
  46 static inline void
  47 alloc_context(struct mm_struct *mm)
  48 {
  49         struct mm_struct *old_mm;
  50
  51         D(printk("tlb: alloc context %d (%p)\n", map_replace_ptr, mm));
  52
  53         /* did we replace an mm ? */
  54
  55         old_mm = page_id_map[map_replace_ptr];
  56
  57         if(old_mm) {
  58                 /* throw out any TLB entries belonging to the mm we replace
  59                  * in the map
  60                  */
  61                 flush_tlb_mm(old_mm);
  62
  63                 old_mm->context = NO_CONTEXT;
  64         }
  65
  66         /* insert it into the page_id_map */
  67
  68         mm->context = map_replace_ptr;
  69         page_id_map[map_replace_ptr] = mm;
  70
  71         map_replace_ptr++;
  72
  73         if(map_replace_ptr == INVALID_PAGEID)
  74                 map_replace_ptr = 0;         /* wrap around */
  75 }
  76
  77 /*
  78  * if needed, get a new MMU context for the mm. otherwise nothing is done.
  79  */
  80
  81 void
  82 get_mmu_context(struct mm_struct *mm)
  83 {
  84         if(mm->context == NO_CONTEXT)
  85                 alloc_context(mm);
  86 }
  87
  88 /* called by __exit_mm to destroy the used MMU context if any before
  89  * destroying the mm itself. this is only called when the last user of the mm
  90  * drops it.
  91  *
  92  * the only thing we really need to do here is mark the used PID slot
  93  * as empty.
  94  */
  95
  96 void
  97 destroy_context(struct mm_struct *mm)
  98 {
  99         if(mm->context != NO_CONTEXT) {
 100                 D(printk("destroy_context %d (%p)\n", mm->context, mm));
 101                 flush_tlb_mm(mm);  /* TODO this might be redundant ? */
 102                 page_id_map[mm->context] = NULL;
 103                 /* mm->context = NO_CONTEXT; redundant.. mm will be freed */
 104         }
 105 }
 106
 107 /* called once during VM initialization, from init.c */
 108
 109 void __init
 110 tlb_init(void)
 111 {
 112         int i;
 113
 114         /* clear the page_id map */
 115
 116         for (i = 1; i < sizeof (page_id_map) / sizeof (page_id_map[0]); i++)
 117                 page_id_map[i] = NULL;
 118
 119         /* invalidate the entire TLB */
 120
 121         flush_tlb_all();
 122
 123         /* the init_mm has context 0 from the boot */
 124
 125         page_id_map[0] = &init_mm;
 126 }