arch/cris/mm/tlb.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/arch/cris/mm/tlb.c
   4  *
   5  *  Copyright (C) 2000, 2001  Axis Communications AB
   6  *
   7  *  Authors:   Bjorn Wesen (bjornw@axis.com)
   8  *
   9  */
  10
  11 #include <linux/init.h>
  12 #include <linux/kernel.h>
  13 #include <linux/mm_types.h>
  14
  15 #include <asm/tlb.h>
  16
  17 #define D(x)
  18
  19 /* The TLB can host up to 64 different mm contexts at the same time.
  20  * The running context is R_MMU_CONTEXT, and each TLB entry contains a
  21  * page_id that has to match to give a hit. In page_id_map, we keep track
  22  * of which mm we have assigned to which page_id, so that we know when
  23  * to invalidate TLB entries.
  24  *
  25  * The last page_id is never running - it is used as an invalid page_id
  26  * so we can make TLB entries that will never match.
  27  *
  28  * Notice that we need to make the flushes atomic, otherwise an interrupt
  29  * handler that uses vmalloced memory might cause a TLB load in the middle
  30  * of a flush causing.
  31  */
  32
  33 struct mm_struct *page_id_map[NUM_PAGEID];
  34 static int map_replace_ptr = 1;  /* which page_id_map entry to replace next */
  35
  36 /* the following functions are similar to those used in the PPC port */
  37
  38 static inline void
  39 alloc_context(struct mm_struct *mm)
  40 {
  41         struct mm_struct *old_mm;
  42
  43         D(printk("tlb: alloc context %d (%p)\n", map_replace_ptr, mm));
  44
  45         /* did we replace an mm ? */
  46
  47         old_mm = page_id_map[map_replace_ptr];
  48
  49         if(old_mm) {
  50                 /* throw out any TLB entries belonging to the mm we replace
  51                  * in the map
  52                  */
  53                 flush_tlb_mm(old_mm);
  54
  55                 old_mm->context.page_id = NO_CONTEXT;
  56         }
  57
  58         /* insert it into the page_id_map */
  59
  60         mm->context.page_id = map_replace_ptr;
  61         page_id_map[map_replace_ptr] = mm;
  62
  63         map_replace_ptr++;
  64
  65         if(map_replace_ptr == INVALID_PAGEID)
  66                 map_replace_ptr = 0;         /* wrap around */
  67 }
  68
  69 /*
  70  * if needed, get a new MMU context for the mm. otherwise nothing is done.
  71  */
  72
  73 void
  74 get_mmu_context(struct mm_struct *mm)
  75 {
  76         if(mm->context.page_id == NO_CONTEXT)
  77                 alloc_context(mm);
  78 }
  79
  80 /* called by __exit_mm to destroy the used MMU context if any before
  81  * destroying the mm itself. this is only called when the last user of the mm
  82  * drops it.
  83  *
  84  * the only thing we really need to do here is mark the used PID slot
  85  * as empty.
  86  */
  87
  88 void
  89 destroy_context(struct mm_struct *mm)
  90 {
  91         if(mm->context.page_id != NO_CONTEXT) {
  92                 D(printk("destroy_context %d (%p)\n", mm->context.page_id, mm));
  93                 flush_tlb_mm(mm);  /* TODO this might be redundant ? */
  94                 page_id_map[mm->context.page_id] = NULL;
  95         }
  96 }
  97
  98 /* called once during VM initialization, from init.c */
  99
 100 void __init
 101 tlb_init(void)
 102 {
 103         int i;
 104
 105         /* clear the page_id map */
 106
 107         for (i = 1; i < ARRAY_SIZE(page_id_map); i++)
 108                 page_id_map[i] = NULL;
 109
 110         /* invalidate the entire TLB */
 111
 112         flush_tlb_all();
 113
 114         /* the init_mm has context 0 from the boot */
 115
 116         page_id_map[0] = &init_mm;
 117 }