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1 | /* |
2 | * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu> | |
3 | * Copyright (C) 2008-2009 PetaLogix | |
4 | * Copyright (C) 2006 Atmark Techno, Inc. | |
5 | * | |
6 | * This file is subject to the terms and conditions of the GNU General Public | |
7 | * License. See the file "COPYING" in the main directory of this archive | |
8 | * for more details. | |
9 | */ | |
10 | ||
11 | #ifndef _ASM_MICROBLAZE_MMU_CONTEXT_H | |
12 | #define _ASM_MICROBLAZE_MMU_CONTEXT_H | |
13 | ||
60063497 | 14 | #include <linux/atomic.h> |
fc34d1eb MS |
15 | #include <asm/bitops.h> |
16 | #include <asm/mmu.h> | |
17 | #include <asm-generic/mm_hooks.h> | |
18 | ||
19 | # ifdef __KERNEL__ | |
20 | /* | |
21 | * This function defines the mapping from contexts to VSIDs (virtual | |
22 | * segment IDs). We use a skew on both the context and the high 4 bits | |
23 | * of the 32-bit virtual address (the "effective segment ID") in order | |
24 | * to spread out the entries in the MMU hash table. | |
25 | */ | |
26 | # define CTX_TO_VSID(ctx, va) (((ctx) * (897 * 16) + ((va) >> 28) * 0x111) \ | |
27 | & 0xffffff) | |
28 | ||
29 | /* | |
30 | MicroBlaze has 256 contexts, so we can just rotate through these | |
31 | as a way of "switching" contexts. If the TID of the TLB is zero, | |
32 | the PID/TID comparison is disabled, so we can use a TID of zero | |
33 | to represent all kernel pages as shared among all contexts. | |
34 | */ | |
35 | ||
36 | static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk) | |
37 | { | |
38 | } | |
39 | ||
40 | # define NO_CONTEXT 256 | |
41 | # define LAST_CONTEXT 255 | |
42 | # define FIRST_CONTEXT 1 | |
43 | ||
44 | /* | |
45 | * Set the current MMU context. | |
46 | * This is done byloading up the segment registers for the user part of the | |
47 | * address space. | |
48 | * | |
49 | * Since the PGD is immediately available, it is much faster to simply | |
50 | * pass this along as a second parameter, which is required for 8xx and | |
51 | * can be used for debugging on all processors (if you happen to have | |
52 | * an Abatron). | |
53 | */ | |
54 | extern void set_context(mm_context_t context, pgd_t *pgd); | |
55 | ||
56 | /* | |
57 | * Bitmap of contexts in use. | |
58 | * The size of this bitmap is LAST_CONTEXT + 1 bits. | |
59 | */ | |
60 | extern unsigned long context_map[]; | |
61 | ||
62 | /* | |
63 | * This caches the next context number that we expect to be free. | |
64 | * Its use is an optimization only, we can't rely on this context | |
65 | * number to be free, but it usually will be. | |
66 | */ | |
67 | extern mm_context_t next_mmu_context; | |
68 | ||
69 | /* | |
70 | * Since we don't have sufficient contexts to give one to every task | |
71 | * that could be in the system, we need to be able to steal contexts. | |
72 | * These variables support that. | |
73 | */ | |
74 | extern atomic_t nr_free_contexts; | |
75 | extern struct mm_struct *context_mm[LAST_CONTEXT+1]; | |
76 | extern void steal_context(void); | |
77 | ||
78 | /* | |
79 | * Get a new mmu context for the address space described by `mm'. | |
80 | */ | |
81 | static inline void get_mmu_context(struct mm_struct *mm) | |
82 | { | |
83 | mm_context_t ctx; | |
84 | ||
85 | if (mm->context != NO_CONTEXT) | |
86 | return; | |
87 | while (atomic_dec_if_positive(&nr_free_contexts) < 0) | |
88 | steal_context(); | |
89 | ctx = next_mmu_context; | |
90 | while (test_and_set_bit(ctx, context_map)) { | |
91 | ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx); | |
92 | if (ctx > LAST_CONTEXT) | |
93 | ctx = 0; | |
94 | } | |
95 | next_mmu_context = (ctx + 1) & LAST_CONTEXT; | |
96 | mm->context = ctx; | |
97 | context_mm[ctx] = mm; | |
98 | } | |
99 | ||
100 | /* | |
101 | * Set up the context for a new address space. | |
102 | */ | |
103 | # define init_new_context(tsk, mm) (((mm)->context = NO_CONTEXT), 0) | |
104 | ||
105 | /* | |
106 | * We're finished using the context for an address space. | |
107 | */ | |
108 | static inline void destroy_context(struct mm_struct *mm) | |
109 | { | |
110 | if (mm->context != NO_CONTEXT) { | |
111 | clear_bit(mm->context, context_map); | |
112 | mm->context = NO_CONTEXT; | |
113 | atomic_inc(&nr_free_contexts); | |
114 | } | |
115 | } | |
116 | ||
117 | static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, | |
118 | struct task_struct *tsk) | |
119 | { | |
120 | tsk->thread.pgdir = next->pgd; | |
121 | get_mmu_context(next); | |
122 | set_context(next->context, next->pgd); | |
123 | } | |
124 | ||
125 | /* | |
126 | * After we have set current->mm to a new value, this activates | |
127 | * the context for the new mm so we see the new mappings. | |
128 | */ | |
129 | static inline void activate_mm(struct mm_struct *active_mm, | |
130 | struct mm_struct *mm) | |
131 | { | |
132 | current->thread.pgdir = mm->pgd; | |
133 | get_mmu_context(mm); | |
134 | set_context(mm->context, mm->pgd); | |
135 | } | |
136 | ||
137 | extern void mmu_context_init(void); | |
138 | ||
139 | # endif /* __KERNEL__ */ | |
140 | #endif /* _ASM_MICROBLAZE_MMU_CONTEXT_H */ |