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