1 /* MN10300 MMU context management
2 *
3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4 * Modified by David Howells (dhowells@redhat.com)
5 * - Derived from include/asm-m32r/mmu_context.h
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public Licence
9 * as published by the Free Software Foundation; either version
10 * 2 of the Licence, or (at your option) any later version.
11 *
12 *
13 * This implements an algorithm to provide TLB PID mappings to provide
14 * selective access to the TLB for processes, thus reducing the number of TLB
15 * flushes required.
16 *
17 * Note, however, that the M32R algorithm is technically broken as it does not
18 * handle version wrap-around, and could, theoretically, have a problem with a
19 * very long lived program that sleeps long enough for the version number to
20 * wrap all the way around so that its TLB mappings appear valid once again.
21 */
22 #ifndef _ASM_MMU_CONTEXT_H
23 #define _ASM_MMU_CONTEXT_H
24
25 #include <asm/atomic.h>
26 #include <asm/pgalloc.h>
27 #include <asm/tlbflush.h>
28 #include <asm-generic/mm_hooks.h>
29
30 #define MMU_CONTEXT_TLBPID_NR 256
31 #define MMU_CONTEXT_TLBPID_MASK 0x000000ffUL
32 #define MMU_CONTEXT_VERSION_MASK 0xffffff00UL
33 #define MMU_CONTEXT_FIRST_VERSION 0x00000100UL
34 #define MMU_NO_CONTEXT 0x00000000UL
35 #define MMU_CONTEXT_TLBPID_LOCK_NR 0
36
37 #define enter_lazy_tlb(mm, tsk) do {} while (0)
38
cpu_ran_vm(int cpu,struct mm_struct * mm)39 static inline void cpu_ran_vm(int cpu, struct mm_struct *mm)
40 {
41 #ifdef CONFIG_SMP
42 cpumask_set_cpu(cpu, mm_cpumask(mm));
43 #endif
44 }
45
cpu_maybe_ran_vm(int cpu,struct mm_struct * mm)46 static inline bool cpu_maybe_ran_vm(int cpu, struct mm_struct *mm)
47 {
48 #ifdef CONFIG_SMP
49 return cpumask_test_and_set_cpu(cpu, mm_cpumask(mm));
50 #else
51 return true;
52 #endif
53 }
54
55 #ifdef CONFIG_MN10300_TLB_USE_PIDR
56 extern unsigned long mmu_context_cache[NR_CPUS];
57 #define mm_context(mm) (mm->context.tlbpid[smp_processor_id()])
58
59 /**
60 * allocate_mmu_context - Allocate storage for the arch-specific MMU data
61 * @mm: The userspace VM context being set up
62 */
allocate_mmu_context(struct mm_struct * mm)63 static inline unsigned long allocate_mmu_context(struct mm_struct *mm)
64 {
65 unsigned long *pmc = &mmu_context_cache[smp_processor_id()];
66 unsigned long mc = ++(*pmc);
67
68 if (!(mc & MMU_CONTEXT_TLBPID_MASK)) {
69 /* we exhausted the TLB PIDs of this version on this CPU, so we
70 * flush this CPU's TLB in its entirety and start new cycle */
71 local_flush_tlb_all();
72
73 /* fix the TLB version if needed (we avoid version #0 so as to
74 * distingush MMU_NO_CONTEXT) */
75 if (!mc)
76 *pmc = mc = MMU_CONTEXT_FIRST_VERSION;
77 }
78 mm_context(mm) = mc;
79 return mc;
80 }
81
82 /*
83 * get an MMU context if one is needed
84 */
get_mmu_context(struct mm_struct * mm)85 static inline unsigned long get_mmu_context(struct mm_struct *mm)
86 {
87 unsigned long mc = MMU_NO_CONTEXT, cache;
88
89 if (mm) {
90 cache = mmu_context_cache[smp_processor_id()];
91 mc = mm_context(mm);
92
93 /* if we have an old version of the context, replace it */
94 if ((mc ^ cache) & MMU_CONTEXT_VERSION_MASK)
95 mc = allocate_mmu_context(mm);
96 }
97 return mc;
98 }
99
100 /*
101 * initialise the context related info for a new mm_struct instance
102 */
init_new_context(struct task_struct * tsk,struct mm_struct * mm)103 static inline int init_new_context(struct task_struct *tsk,
104 struct mm_struct *mm)
105 {
106 int num_cpus = NR_CPUS, i;
107
108 for (i = 0; i < num_cpus; i++)
109 mm->context.tlbpid[i] = MMU_NO_CONTEXT;
110 return 0;
111 }
112
113 /*
114 * after we have set current->mm to a new value, this activates the context for
115 * the new mm so we see the new mappings.
116 */
activate_context(struct mm_struct * mm)117 static inline void activate_context(struct mm_struct *mm)
118 {
119 PIDR = get_mmu_context(mm) & MMU_CONTEXT_TLBPID_MASK;
120 }
121 #else /* CONFIG_MN10300_TLB_USE_PIDR */
122
123 #define init_new_context(tsk, mm) (0)
124 #define activate_context(mm) local_flush_tlb()
125
126 #endif /* CONFIG_MN10300_TLB_USE_PIDR */
127
128 /**
129 * destroy_context - Destroy mm context information
130 * @mm: The MM being destroyed.
131 *
132 * Destroy context related info for an mm_struct that is about to be put to
133 * rest
134 */
135 #define destroy_context(mm) do {} while (0)
136
137 /**
138 * switch_mm - Change between userspace virtual memory contexts
139 * @prev: The outgoing MM context.
140 * @next: The incoming MM context.
141 * @tsk: The incoming task.
142 */
switch_mm(struct mm_struct * prev,struct mm_struct * next,struct task_struct * tsk)143 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
144 struct task_struct *tsk)
145 {
146 int cpu = smp_processor_id();
147
148 if (prev != next) {
149 #ifdef CONFIG_SMP
150 per_cpu(cpu_tlbstate, cpu).active_mm = next;
151 #endif
152 cpu_ran_vm(cpu, next);
153 PTBR = (unsigned long) next->pgd;
154 activate_context(next);
155 }
156 }
157
158 #define deactivate_mm(tsk, mm) do {} while (0)
159 #define activate_mm(prev, next) switch_mm((prev), (next), NULL)
160
161 #endif /* _ASM_MMU_CONTEXT_H */
162