summaryrefslogtreecommitdiffstats
path: root/arch/microblaze/include/asm/mmu_context_mm.h
blob: 99472d2ca3404d44e43d1565ff7bef7fdb30d442 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
/*
 * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
 * Copyright (C) 2008-2009 PetaLogix
 * Copyright (C) 2006 Atmark Techno, Inc.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License. See the file "COPYING" in the main directory of this archive
 * for more details.
 */

#ifndef _ASM_MICROBLAZE_MMU_CONTEXT_H
#define _ASM_MICROBLAZE_MMU_CONTEXT_H

#include <linux/atomic.h>
#include <linux/mm_types.h>

#include <asm/bitops.h>
#include <asm/mmu.h>
#include <asm-generic/mm_hooks.h>

# ifdef __KERNEL__
/*
 * This function defines the mapping from contexts to VSIDs (virtual
 * segment IDs).  We use a skew on both the context and the high 4 bits
 * of the 32-bit virtual address (the "effective segment ID") in order
 * to spread out the entries in the MMU hash table.
 */
# define CTX_TO_VSID(ctx, va)	(((ctx) * (897 * 16) + ((va) >> 28) * 0x111) \
				 & 0xffffff)

/*
   MicroBlaze has 256 contexts, so we can just rotate through these
   as a way of "switching" contexts.  If the TID of the TLB is zero,
   the PID/TID comparison is disabled, so we can use a TID of zero
   to represent all kernel pages as shared among all contexts.
 */

static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
{
}

# define NO_CONTEXT	256
# define LAST_CONTEXT	255
# define FIRST_CONTEXT	1

/*
 * Set the current MMU context.
 * This is done byloading up the segment registers for the user part of the
 * address space.
 *
 * Since the PGD is immediately available, it is much faster to simply
 * pass this along as a second parameter, which is required for 8xx and
 * can be used for debugging on all processors (if you happen to have
 * an Abatron).
 */
extern void set_context(mm_context_t context, pgd_t *pgd);

/*
 * Bitmap of contexts in use.
 * The size of this bitmap is LAST_CONTEXT + 1 bits.
 */
extern unsigned long context_map[];

/*
 * This caches the next context number that we expect to be free.
 * Its use is an optimization only, we can't rely on this context
 * number to be free, but it usually will be.
 */
extern mm_context_t next_mmu_context;

/*
 * Since we don't have sufficient contexts to give one to every task
 * that could be in the system, we need to be able to steal contexts.
 * These variables support that.
 */
extern atomic_t nr_free_contexts;
extern struct mm_struct *context_mm[LAST_CONTEXT+1];
extern void steal_context(void);

/*
 * Get a new mmu context for the address space described by `mm'.
 */
static inline void get_mmu_context(struct mm_struct *mm)
{
	mm_context_t ctx;

	if (mm->context != NO_CONTEXT)
		return;
	while (atomic_dec_if_positive(&nr_free_contexts) < 0)
		steal_context();
	ctx = next_mmu_context;
	while (test_and_set_bit(ctx, context_map)) {
		ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
		if (ctx > LAST_CONTEXT)
			ctx = 0;
	}
	next_mmu_context = (ctx + 1) & LAST_CONTEXT;
	mm->context = ctx;
	context_mm[ctx] = mm;
}

/*
 * Set up the context for a new address space.
 */
# define init_new_context(tsk, mm)	(((mm)->context = NO_CONTEXT), 0)

/*
 * We're finished using the context for an address space.
 */
static inline void destroy_context(struct mm_struct *mm)
{
	if (mm->context != NO_CONTEXT) {
		clear_bit(mm->context, context_map);
		mm->context = NO_CONTEXT;
		atomic_inc(&nr_free_contexts);
	}
}

static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
			     struct task_struct *tsk)
{
	tsk->thread.pgdir = next->pgd;
	get_mmu_context(next);
	set_context(next->context, next->pgd);
}

/*
 * After we have set current->mm to a new value, this activates
 * the context for the new mm so we see the new mappings.
 */
static inline void activate_mm(struct mm_struct *active_mm,
			struct mm_struct *mm)
{
	current->thread.pgdir = mm->pgd;
	get_mmu_context(mm);
	set_context(mm->context, mm->pgd);
}

extern void mmu_context_init(void);

# endif /* __KERNEL__ */
#endif /* _ASM_MICROBLAZE_MMU_CONTEXT_H */