Linux Kernel  3.7.1
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
tlb.c
Go to the documentation of this file.
1 /*
2  * linux/arch/cris/mm/tlb.c
3  *
4  * Copyright (C) 2000, 2001 Axis Communications AB
5  *
6  * Authors: Bjorn Wesen ([email protected])
7  *
8  */
9 
10 #include <linux/init.h>
11 #include <linux/kernel.h>
12 #include <asm/tlb.h>
13 
14 #define D(x)
15 
16 /* The TLB can host up to 64 different mm contexts at the same time.
17  * The running context is R_MMU_CONTEXT, and each TLB entry contains a
18  * page_id that has to match to give a hit. In page_id_map, we keep track
19  * of which mm we have assigned to which page_id, so that we know when
20  * to invalidate TLB entries.
21  *
22  * The last page_id is never running - it is used as an invalid page_id
23  * so we can make TLB entries that will never match.
24  *
25  * Notice that we need to make the flushes atomic, otherwise an interrupt
26  * handler that uses vmalloced memory might cause a TLB load in the middle
27  * of a flush causing.
28  */
29 
31 static int map_replace_ptr = 1; /* which page_id_map entry to replace next */
32 
33 /* the following functions are similar to those used in the PPC port */
34 
35 static inline void
36 alloc_context(struct mm_struct *mm)
37 {
38  struct mm_struct *old_mm;
39 
40  D(printk("tlb: alloc context %d (%p)\n", map_replace_ptr, mm));
41 
42  /* did we replace an mm ? */
43 
44  old_mm = page_id_map[map_replace_ptr];
45 
46  if(old_mm) {
47  /* throw out any TLB entries belonging to the mm we replace
48  * in the map
49  */
50  flush_tlb_mm(old_mm);
51 
52  old_mm->context.page_id = NO_CONTEXT;
53  }
54 
55  /* insert it into the page_id_map */
56 
57  mm->context.page_id = map_replace_ptr;
58  page_id_map[map_replace_ptr] = mm;
59 
60  map_replace_ptr++;
61 
62  if(map_replace_ptr == INVALID_PAGEID)
63  map_replace_ptr = 0; /* wrap around */
64 }
65 
66 /*
67  * if needed, get a new MMU context for the mm. otherwise nothing is done.
68  */
69 
70 void
72 {
73  if(mm->context.page_id == NO_CONTEXT)
74  alloc_context(mm);
75 }
76 
77 /* called by __exit_mm to destroy the used MMU context if any before
78  * destroying the mm itself. this is only called when the last user of the mm
79  * drops it.
80  *
81  * the only thing we really need to do here is mark the used PID slot
82  * as empty.
83  */
84 
85 void
87 {
88  if(mm->context.page_id != NO_CONTEXT) {
89  D(printk("destroy_context %d (%p)\n", mm->context.page_id, mm));
90  flush_tlb_mm(mm); /* TODO this might be redundant ? */
91  page_id_map[mm->context.page_id] = NULL;
92  }
93 }
94 
95 /* called once during VM initialization, from init.c */
96 
97 void __init
98 tlb_init(void)
99 {
100  int i;
101 
102  /* clear the page_id map */
103 
104  for (i = 1; i < ARRAY_SIZE(page_id_map); i++)
105  page_id_map[i] = NULL;
106 
107  /* invalidate the entire TLB */
108 
109  flush_tlb_all();
110 
111  /* the init_mm has context 0 from the boot */
112 
113  page_id_map[0] = &init_mm;
114 }