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
enter_lazy_tlb(struct mm_struct * mm,struct task_struct * tsk)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 */
get_mmu_context(struct mm_struct * mm)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 */
destroy_context(struct mm_struct * mm)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
switch_mm(struct mm_struct * prev,struct mm_struct * next,struct task_struct * tsk)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 */
activate_mm(struct mm_struct * active_mm,struct mm_struct * mm)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 */
141
