2 * arch/arm/include/asm/mmu_context.h
4 * Copyright (C) 1996 Russell King.
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
11 * 27-06-1996 RMK Created
13 #ifndef __ASM_ARM_MMU_CONTEXT_H
14 #define __ASM_ARM_MMU_CONTEXT_H
16 #include <linux/compiler.h>
17 #include <linux/sched.h>
18 #include <asm/cacheflush.h>
19 #include <asm/cachetype.h>
20 #include <asm/proc-fns.h>
21 #include <asm-generic/mm_hooks.h>
23 void __check_kvm_seq(struct mm_struct *mm);
25 #ifdef CONFIG_CPU_HAS_ASID
28 * On ARMv6, we have the following structure in the Context ID:
31 * +-------------------------+-----------+
32 * | process ID | ASID |
33 * +-------------------------+-----------+
35 * +-------------------------------------+
37 * The ASID is used to tag entries in the CPU caches and TLBs.
38 * The context ID is used by debuggers and trace logic, and
39 * should be unique within all running processes.
42 #define ASID_MASK ((~0) << ASID_BITS)
43 #define ASID_FIRST_VERSION (1 << ASID_BITS)
45 extern unsigned int cpu_last_asid;
47 DECLARE_PER_CPU(struct mm_struct *, current_mm);
50 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
51 void __new_context(struct mm_struct *mm);
52 void cpu_set_reserved_ttbr0(void);
54 static inline void switch_new_context(struct mm_struct *mm)
60 local_irq_save(flags);
61 cpu_switch_mm(mm->pgd, mm);
62 local_irq_restore(flags);
65 static inline void check_and_switch_context(struct mm_struct *mm,
66 struct task_struct *tsk)
68 if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq))
72 * Required during context switch to avoid speculative page table
73 * walking with the wrong TTBR.
75 cpu_set_reserved_ttbr0();
77 if (!((mm->context.id ^ cpu_last_asid) >> ASID_BITS))
79 * The ASID is from the current generation, just switch to the
80 * new pgd. This condition is only true for calls from
81 * context_switch() and interrupts are already disabled.
83 cpu_switch_mm(mm->pgd, mm);
84 else if (irqs_disabled())
86 * Defer the new ASID allocation until after the context
87 * switch critical region since __new_context() cannot be
88 * called with interrupts disabled (it sends IPIs).
90 set_ti_thread_flag(task_thread_info(tsk), TIF_SWITCH_MM);
93 * That is a direct call to switch_mm() or activate_mm() with
94 * interrupts enabled and a new context.
96 switch_new_context(mm);
99 #define init_new_context(tsk,mm) (__init_new_context(tsk,mm),0)
101 #define finish_arch_post_lock_switch \
102 finish_arch_post_lock_switch
103 static inline void finish_arch_post_lock_switch(void)
105 if (test_and_clear_thread_flag(TIF_SWITCH_MM))
106 switch_new_context(current->mm);
109 #else /* !CONFIG_CPU_HAS_ASID */
111 static inline void check_and_switch_context(struct mm_struct *mm,
112 struct task_struct *tsk)
115 if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq))
117 cpu_switch_mm(mm->pgd, mm);
121 #define init_new_context(tsk,mm) 0
123 #define finish_arch_post_lock_switch() do { } while (0)
125 #endif /* CONFIG_CPU_HAS_ASID */
127 #define destroy_context(mm) do { } while(0)
130 * This is called when "tsk" is about to enter lazy TLB mode.
132 * mm: describes the currently active mm context
133 * tsk: task which is entering lazy tlb
134 * cpu: cpu number which is entering lazy tlb
136 * tsk->mm will be NULL
139 enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
144 * This is the actual mm switch as far as the scheduler
145 * is concerned. No registers are touched. We avoid
146 * calling the CPU specific function when the mm hasn't
150 switch_mm(struct mm_struct *prev, struct mm_struct *next,
151 struct task_struct *tsk)
154 unsigned int cpu = smp_processor_id();
157 /* check for possible thread migration */
158 if (!cpumask_empty(mm_cpumask(next)) &&
159 !cpumask_test_cpu(cpu, mm_cpumask(next)))
160 __flush_icache_all();
162 if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next) {
164 struct mm_struct **crt_mm = &per_cpu(current_mm, cpu);
167 check_and_switch_context(next, tsk);
169 cpumask_clear_cpu(cpu, mm_cpumask(prev));
174 #define deactivate_mm(tsk,mm) do { } while (0)
175 #define activate_mm(prev,next) switch_mm(prev, next, NULL)