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1 | /* |
2 | * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License version 2 as | |
6 | * published by the Free Software Foundation. | |
7 | * | |
8 | * vineetg: May 2011 | |
9 | * -Refactored get_new_mmu_context( ) to only handle live-mm. | |
10 | * retiring-mm handled in other hooks | |
11 | * | |
12 | * Vineetg: March 25th, 2008: Bug #92690 | |
13 | * -Major rewrite of Core ASID allocation routine get_new_mmu_context | |
14 | * | |
15 | * Amit Bhor, Sameer Dhavale: Codito Technologies 2004 | |
16 | */ | |
17 | ||
18 | #ifndef _ASM_ARC_MMU_CONTEXT_H | |
19 | #define _ASM_ARC_MMU_CONTEXT_H | |
20 | ||
21 | #include <asm/arcregs.h> | |
22 | #include <asm/tlb.h> | |
6e84f315 | 23 | #include <linux/sched/mm.h> |
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24 | |
25 | #include <asm-generic/mm_hooks.h> | |
26 | ||
27 | /* ARC700 ASID Management | |
28 | * | |
29 | * ARC MMU provides 8-bit ASID (0..255) to TAG TLB entries, allowing entries | |
30 | * with same vaddr (different tasks) to co-exit. This provides for | |
31 | * "Fast Context Switch" i.e. no TLB flush on ctxt-switch | |
32 | * | |
33 | * Linux assigns each task a unique ASID. A simple round-robin allocation | |
63eca94c | 34 | * of H/w ASID is done using software tracker @asid_cpu. |
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35 | * When it reaches max 255, the allocation cycle starts afresh by flushing |
36 | * the entire TLB and wrapping ASID back to zero. | |
37 | * | |
947bf103 VG |
38 | * A new allocation cycle, post rollover, could potentially reassign an ASID |
39 | * to a different task. Thus the rule is to refresh the ASID in a new cycle. | |
63eca94c | 40 | * The 32 bit @asid_cpu (and mm->asid) have 8 bits MMU PID and rest 24 bits |
947bf103 VG |
41 | * serve as cycle/generation indicator and natural 32 bit unsigned math |
42 | * automagically increments the generation when lower 8 bits rollover. | |
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43 | */ |
44 | ||
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45 | #define MM_CTXT_ASID_MASK 0x000000ff /* MMU PID reg :8 bit PID */ |
46 | #define MM_CTXT_CYCLE_MASK (~MM_CTXT_ASID_MASK) | |
47 | ||
48 | #define MM_CTXT_FIRST_CYCLE (MM_CTXT_ASID_MASK + 1) | |
49 | #define MM_CTXT_NO_ASID 0UL | |
f1f3347d | 50 | |
63eca94c VG |
51 | #define asid_mm(mm, cpu) mm->context.asid[cpu] |
52 | #define hw_pid(mm, cpu) (asid_mm(mm, cpu) & MM_CTXT_ASID_MASK) | |
f1f3347d | 53 | |
63eca94c VG |
54 | DECLARE_PER_CPU(unsigned int, asid_cache); |
55 | #define asid_cpu(cpu) per_cpu(asid_cache, cpu) | |
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56 | |
57 | /* | |
3daa48d1 VG |
58 | * Get a new ASID if task doesn't have a valid one (unalloc or from prev cycle) |
59 | * Also set the MMU PID register to existing/updated ASID | |
f1f3347d VG |
60 | */ |
61 | static inline void get_new_mmu_context(struct mm_struct *mm) | |
62 | { | |
63eca94c | 63 | const unsigned int cpu = smp_processor_id(); |
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64 | unsigned long flags; |
65 | ||
66 | local_irq_save(flags); | |
67 | ||
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68 | /* |
69 | * Move to new ASID if it was not from current alloc-cycle/generation. | |
947bf103 VG |
70 | * This is done by ensuring that the generation bits in both mm->ASID |
71 | * and cpu's ASID counter are exactly same. | |
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72 | * |
73 | * Note: Callers needing new ASID unconditionally, independent of | |
74 | * generation, e.g. local_flush_tlb_mm() for forking parent, | |
75 | * first need to destroy the context, setting it to invalid | |
76 | * value. | |
77 | */ | |
63eca94c | 78 | if (!((asid_mm(mm, cpu) ^ asid_cpu(cpu)) & MM_CTXT_CYCLE_MASK)) |
3daa48d1 VG |
79 | goto set_hw; |
80 | ||
947bf103 | 81 | /* move to new ASID and handle rollover */ |
63eca94c | 82 | if (unlikely(!(++asid_cpu(cpu) & MM_CTXT_ASID_MASK))) { |
f1f3347d | 83 | |
5ea72a90 | 84 | local_flush_tlb_all(); |
f1f3347d | 85 | |
947bf103 | 86 | /* |
2547476a | 87 | * Above check for rollover of 8 bit ASID in 32 bit container. |
947bf103 VG |
88 | * If the container itself wrapped around, set it to a non zero |
89 | * "generation" to distinguish from no context | |
90 | */ | |
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91 | if (!asid_cpu(cpu)) |
92 | asid_cpu(cpu) = MM_CTXT_FIRST_CYCLE; | |
947bf103 | 93 | } |
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94 | |
95 | /* Assign new ASID to tsk */ | |
63eca94c | 96 | asid_mm(mm, cpu) = asid_cpu(cpu); |
f1f3347d | 97 | |
3daa48d1 | 98 | set_hw: |
63eca94c | 99 | write_aux_reg(ARC_REG_PID, hw_pid(mm, cpu) | MMU_ENABLE); |
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100 | |
101 | local_irq_restore(flags); | |
102 | } | |
103 | ||
104 | /* | |
105 | * Initialize the context related info for a new mm_struct | |
106 | * instance. | |
107 | */ | |
108 | static inline int | |
109 | init_new_context(struct task_struct *tsk, struct mm_struct *mm) | |
110 | { | |
63eca94c VG |
111 | int i; |
112 | ||
113 | for_each_possible_cpu(i) | |
114 | asid_mm(mm, i) = MM_CTXT_NO_ASID; | |
115 | ||
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116 | return 0; |
117 | } | |
118 | ||
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119 | static inline void destroy_context(struct mm_struct *mm) |
120 | { | |
121 | unsigned long flags; | |
122 | ||
123 | /* Needed to elide CONFIG_DEBUG_PREEMPT warning */ | |
124 | local_irq_save(flags); | |
125 | asid_mm(mm, smp_processor_id()) = MM_CTXT_NO_ASID; | |
126 | local_irq_restore(flags); | |
127 | } | |
128 | ||
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129 | /* Prepare the MMU for task: setup PID reg with allocated ASID |
130 | If task doesn't have an ASID (never alloc or stolen, get a new ASID) | |
131 | */ | |
132 | static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, | |
133 | struct task_struct *tsk) | |
134 | { | |
5ea72a90 VG |
135 | const int cpu = smp_processor_id(); |
136 | ||
137 | /* | |
138 | * Note that the mm_cpumask is "aggregating" only, we don't clear it | |
139 | * for the switched-out task, unlike some other arches. | |
140 | * It is used to enlist cpus for sending TLB flush IPIs and not sending | |
141 | * it to CPUs where a task once ran-on, could cause stale TLB entry | |
142 | * re-use, specially for a multi-threaded task. | |
143 | * e.g. T1 runs on C1, migrates to C3. T2 running on C2 munmaps. | |
144 | * For a non-aggregating mm_cpumask, IPI not sent C1, and if T1 | |
145 | * were to re-migrate to C1, it could access the unmapped region | |
146 | * via any existing stale TLB entries. | |
147 | */ | |
148 | cpumask_set_cpu(cpu, mm_cpumask(next)); | |
149 | ||
41195d23 | 150 | #ifndef CONFIG_SMP |
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151 | /* PGD cached in MMU reg to avoid 3 mem lookups: task->mm->pgd */ |
152 | write_aux_reg(ARC_REG_SCRATCH_DATA0, next->pgd); | |
41195d23 | 153 | #endif |
f1f3347d | 154 | |
3daa48d1 | 155 | get_new_mmu_context(next); |
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156 | } |
157 | ||
c6011553 VG |
158 | /* |
159 | * Called at the time of execve() to get a new ASID | |
160 | * Note the subtlety here: get_new_mmu_context() behaves differently here | |
161 | * vs. in switch_mm(). Here it always returns a new ASID, because mm has | |
162 | * an unallocated "initial" value, while in latter, it moves to a new ASID, | |
163 | * only if it was unallocated | |
164 | */ | |
165 | #define activate_mm(prev, next) switch_mm(prev, next, NULL) | |
166 | ||
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167 | /* it seemed that deactivate_mm( ) is a reasonable place to do book-keeping |
168 | * for retiring-mm. However destroy_context( ) still needs to do that because | |
169 | * between mm_release( ) = >deactive_mm( ) and | |
170 | * mmput => .. => __mmdrop( ) => destroy_context( ) | |
171 | * there is a good chance that task gets sched-out/in, making it's ASID valid | |
172 | * again (this teased me for a whole day). | |
173 | */ | |
174 | #define deactivate_mm(tsk, mm) do { } while (0) | |
175 | ||
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176 | #define enter_lazy_tlb(mm, tsk) |
177 | ||
178 | #endif /* __ASM_ARC_MMU_CONTEXT_H */ |