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 <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
30 struct mm_struct *page_id_map[NUM_PAGEID];
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
alloc_context(struct mm_struct * mm)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
get_mmu_context(struct mm_struct * mm)71 get_mmu_context(struct mm_struct *mm)
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
destroy_context(struct mm_struct * mm)86 destroy_context(struct mm_struct *mm)
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
tlb_init(void)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 }
115