arch/arm/include/asm/mmu_context.h

   1 /*
   2  *  arch/arm/include/asm/mmu_context.h
   3  *
   4  *  Copyright (C) 1996 Russell King.
   5  *
   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.
   9  *
  10  *  Changelog:
  11  *   27-06-1996 RMK     Created
  12  */
  13 #ifndef __ASM_ARM_MMU_CONTEXT_H
  14 #define __ASM_ARM_MMU_CONTEXT_H
  15
  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>
  22
  23 void __check_kvm_seq(struct mm_struct *mm);
  24
  25 #ifdef CONFIG_CPU_HAS_ASID
  26
  27 /*
  28  * On ARMv6, we have the following structure in the Context ID:
  29  *
  30  * 31                         7          0
  31  * +-------------------------+-----------+
  32  * |      process ID         |   ASID    |
  33  * +-------------------------+-----------+
  34  * |              context ID             |
  35  * +-------------------------------------+
  36  *
  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.
  40  */
  41 #define ASID_BITS               8
  42 #define ASID_MASK               ((~0) << ASID_BITS)
  43 #define ASID_FIRST_VERSION      (1 << ASID_BITS)
  44
  45 extern unsigned int cpu_last_asid;
  46 #ifdef CONFIG_SMP
  47 DECLARE_PER_CPU(struct mm_struct *, current_mm);
  48 #endif
  49
  50 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
  51 void __new_context(struct mm_struct *mm);
  52
  53 static inline void check_context(struct mm_struct *mm)
  54 {
  55         /*
  56          * This code is executed with interrupts enabled. Therefore,
  57          * mm->context.id cannot be updated to the latest ASID version
  58          * on a different CPU (and condition below not triggered)
  59          * without first getting an IPI to reset the context. The
  60          * alternative is to take a read_lock on mm->context.id_lock
  61          * (after changing its type to rwlock_t).
  62          */
  63         if (unlikely((mm->context.id ^ cpu_last_asid) >> ASID_BITS))
  64                 __new_context(mm);
  65
  66         if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq))
  67                 __check_kvm_seq(mm);
  68 }
  69
  70 #define init_new_context(tsk,mm)        (__init_new_context(tsk,mm),0)
  71
  72 #else
  73
  74 static inline void check_context(struct mm_struct *mm)
  75 {
  76 #ifdef CONFIG_MMU
  77         if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq))
  78                 __check_kvm_seq(mm);
  79 #endif
  80 }
  81
  82 #define init_new_context(tsk,mm)        0
  83
  84 #endif
  85
  86 #define destroy_context(mm)             do { } while(0)
  87
  88 /*
  89  * This is called when "tsk" is about to enter lazy TLB mode.
  90  *
  91  * mm:  describes the currently active mm context
  92  * tsk: task which is entering lazy tlb
  93  * cpu: cpu number which is entering lazy tlb
  94  *
  95  * tsk->mm will be NULL
  96  */
  97 static inline void
  98 enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
  99 {
 100 }
 101
 102 /*
 103  * This is the actual mm switch as far as the scheduler
 104  * is concerned.  No registers are touched.  We avoid
 105  * calling the CPU specific function when the mm hasn't
 106  * actually changed.
 107  */
 108 static inline void
 109 switch_mm(struct mm_struct *prev, struct mm_struct *next,
 110           struct task_struct *tsk)
 111 {
 112 #ifdef CONFIG_MMU
 113         unsigned int cpu = smp_processor_id();
 114
 115 #ifdef CONFIG_SMP
 116         /* check for possible thread migration */
 117         if (!cpumask_empty(mm_cpumask(next)) &&
 118             !cpumask_test_cpu(cpu, mm_cpumask(next)))
 119                 __flush_icache_all();
 120 #endif
 121         if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next) {
 122 #ifdef CONFIG_SMP
 123                 struct mm_struct **crt_mm = &per_cpu(current_mm, cpu);
 124                 *crt_mm = next;
 125 #endif
 126                 check_context(next);
 127                 cpu_switch_mm(next->pgd, next);
 128                 if (cache_is_vivt())
 129                         cpumask_clear_cpu(cpu, mm_cpumask(prev));
 130         }
 131 #endif
 132 }
 133
 134 #define deactivate_mm(tsk,mm)   do { } while (0)
 135 #define activate_mm(prev,next)  switch_mm(prev, next, NULL)
 136
 137 #endif