1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
4 * Copyright (C) 2008-2009 PetaLogix
5 * Copyright (C) 2006 Atmark Techno, Inc.
6 */
7
8 #ifndef _ASM_MICROBLAZE_MMU_CONTEXT_H
9 #define _ASM_MICROBLAZE_MMU_CONTEXT_H
10
11 #include <linux/atomic.h>
12 #include <linux/mm_types.h>
13 #include <linux/sched.h>
14
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 # define NO_CONTEXT 256
37 # define LAST_CONTEXT 255
38 # define FIRST_CONTEXT 1
39
40 /*
41 * Set the current MMU context.
42 * This is done byloading up the segment registers for the user part of the
43 * address space.
44 *
45 * Since the PGD is immediately available, it is much faster to simply
46 * pass this along as a second parameter, which is required for 8xx and
47 * can be used for debugging on all processors (if you happen to have
48 * an Abatron).
49 */
50 extern void set_context(mm_context_t context, pgd_t *pgd);
51
52 /*
53 * Bitmap of contexts in use.
54 * The size of this bitmap is LAST_CONTEXT + 1 bits.
55 */
56 extern unsigned long context_map[];
57
58 /*
59 * This caches the next context number that we expect to be free.
60 * Its use is an optimization only, we can't rely on this context
61 * number to be free, but it usually will be.
62 */
63 extern mm_context_t next_mmu_context;
64
65 /*
66 * Since we don't have sufficient contexts to give one to every task
67 * that could be in the system, we need to be able to steal contexts.
68 * These variables support that.
69 */
70 extern atomic_t nr_free_contexts;
71 extern struct mm_struct *context_mm[LAST_CONTEXT+1];
72 extern void steal_context(void);
73
74 /*
75 * Get a new mmu context for the address space described by `mm'.
76 */
77 static inline void get_mmu_context(struct mm_struct *mm)
78 {
79 mm_context_t ctx;
80
81 if (mm->context != NO_CONTEXT)
82 return;
83 while (atomic_dec_if_positive(&nr_free_contexts) < 0)
84 steal_context();
85 ctx = next_mmu_context;
86 while (test_and_set_bit(ctx, context_map)) {
87 ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
88 if (ctx > LAST_CONTEXT)
89 ctx = 0;
90 }
91 next_mmu_context = (ctx + 1) & LAST_CONTEXT;
92 mm->context = ctx;
93 context_mm[ctx] = mm;
94 }
95
96 /*
97 * Set up the context for a new address space.
98 */
99 # define init_new_context(tsk, mm) (((mm)->context = NO_CONTEXT), 0)
100
101 /*
102 * We're finished using the context for an address space.
103 */
104 #define destroy_context destroy_context
105 static inline void destroy_context(struct mm_struct *mm)
106 {
107 if (mm->context != NO_CONTEXT) {
108 clear_bit(mm->context, context_map);
109 mm->context = NO_CONTEXT;
110 atomic_inc(&nr_free_contexts);
111 }
112 }
113
114 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
115 struct task_struct *tsk)
116 {
117 tsk->thread.pgdir = next->pgd;
118 get_mmu_context(next);
119 set_context(next->context, next->pgd);
120 }
121
122 /*
123 * After we have set current->mm to a new value, this activates
124 * the context for the new mm so we see the new mappings.
125 */
126 #define activate_mm activate_mm
127 static inline void activate_mm(struct mm_struct *active_mm,
128 struct mm_struct *mm)
129 {
130 current->thread.pgdir = mm->pgd;
131 get_mmu_context(mm);
132 set_context(mm->context, mm->pgd);
133 }
134
135 extern void mmu_context_init(void);
136
137 #include <asm-generic/mmu_context.h>
138
139 # endif /* __KERNEL__ */
140 #endif /* _ASM_MICROBLAZE_MMU_CONTEXT_H */
141
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