arch/mn10300/include/asm/mmu_context.h

   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 <linux/atomic.h>
  26 #include <linux/mm_types.h>
  27
  28 #include <asm/pgalloc.h>
  29 #include <asm/tlbflush.h>
  30 #include <asm-generic/mm_hooks.h>
  31
  32 #define MMU_CONTEXT_TLBPID_NR           256
  33 #define MMU_CONTEXT_TLBPID_MASK         0x000000ffUL
  34 #define MMU_CONTEXT_VERSION_MASK        0xffffff00UL
  35 #define MMU_CONTEXT_FIRST_VERSION       0x00000100UL
  36 #define MMU_NO_CONTEXT                  0x00000000UL
  37 #define MMU_CONTEXT_TLBPID_LOCK_NR      0
  38
  39 #define enter_lazy_tlb(mm, tsk) do {} while (0)
  40
  41 static inline void cpu_ran_vm(int cpu, struct mm_struct *mm)
  42 {
  43 #ifdef CONFIG_SMP
  44         cpumask_set_cpu(cpu, mm_cpumask(mm));
  45 #endif
  46 }
  47
  48 static inline bool cpu_maybe_ran_vm(int cpu, struct mm_struct *mm)
  49 {
  50 #ifdef CONFIG_SMP
  51         return cpumask_test_and_set_cpu(cpu, mm_cpumask(mm));
  52 #else
  53         return true;
  54 #endif
  55 }
  56
  57 #ifdef CONFIG_MN10300_TLB_USE_PIDR
  58 extern unsigned long mmu_context_cache[NR_CPUS];
  59 #define mm_context(mm)  (mm->context.tlbpid[smp_processor_id()])
  60
  61 /**
  62  * allocate_mmu_context - Allocate storage for the arch-specific MMU data
  63  * @mm: The userspace VM context being set up
  64  */
  65 static inline unsigned long allocate_mmu_context(struct mm_struct *mm)
  66 {
  67         unsigned long *pmc = &mmu_context_cache[smp_processor_id()];
  68         unsigned long mc = ++(*pmc);
  69
  70         if (!(mc & MMU_CONTEXT_TLBPID_MASK)) {
  71                 /* we exhausted the TLB PIDs of this version on this CPU, so we
  72                  * flush this CPU's TLB in its entirety and start new cycle */
  73                 local_flush_tlb_all();
  74
  75                 /* fix the TLB version if needed (we avoid version #0 so as to
  76                  * distinguish MMU_NO_CONTEXT) */
  77                 if (!mc)
  78                         *pmc = mc = MMU_CONTEXT_FIRST_VERSION;
  79         }
  80         mm_context(mm) = mc;
  81         return mc;
  82 }
  83
  84 /*
  85  * get an MMU context if one is needed
  86  */
  87 static inline unsigned long get_mmu_context(struct mm_struct *mm)
  88 {
  89         unsigned long mc = MMU_NO_CONTEXT, cache;
  90
  91         if (mm) {
  92                 cache = mmu_context_cache[smp_processor_id()];
  93                 mc = mm_context(mm);
  94
  95                 /* if we have an old version of the context, replace it */
  96                 if ((mc ^ cache) & MMU_CONTEXT_VERSION_MASK)
  97                         mc = allocate_mmu_context(mm);
  98         }
  99         return mc;
 100 }
 101
 102 /*
 103  * initialise the context related info for a new mm_struct instance
 104  */
 105 static inline int init_new_context(struct task_struct *tsk,
 106                                    struct mm_struct *mm)
 107 {
 108         int num_cpus = NR_CPUS, i;
 109
 110         for (i = 0; i < num_cpus; i++)
 111                 mm->context.tlbpid[i] = MMU_NO_CONTEXT;
 112         return 0;
 113 }
 114
 115 /*
 116  * after we have set current->mm to a new value, this activates the context for
 117  * the new mm so we see the new mappings.
 118  */
 119 static inline void activate_context(struct mm_struct *mm)
 120 {
 121         PIDR = get_mmu_context(mm) & MMU_CONTEXT_TLBPID_MASK;
 122 }
 123 #else  /* CONFIG_MN10300_TLB_USE_PIDR */
 124
 125 #define init_new_context(tsk, mm)       (0)
 126 #define activate_context(mm)            local_flush_tlb()
 127
 128 #endif /* CONFIG_MN10300_TLB_USE_PIDR */
 129
 130 /**
 131  * destroy_context - Destroy mm context information
 132  * @mm: The MM being destroyed.
 133  *
 134  * Destroy context related info for an mm_struct that is about to be put to
 135  * rest
 136  */
 137 #define destroy_context(mm)     do {} while (0)
 138
 139 /**
 140  * switch_mm - Change between userspace virtual memory contexts
 141  * @prev: The outgoing MM context.
 142  * @next: The incoming MM context.
 143  * @tsk: The incoming task.
 144  */
 145 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 146                              struct task_struct *tsk)
 147 {
 148         int cpu = smp_processor_id();
 149
 150         if (prev != next) {
 151 #ifdef CONFIG_SMP
 152                 per_cpu(cpu_tlbstate, cpu).active_mm = next;
 153 #endif
 154                 cpu_ran_vm(cpu, next);
 155                 PTBR = (unsigned long) next->pgd;
 156                 activate_context(next);
 157         }
 158 }
 159
 160 #define deactivate_mm(tsk, mm)  do {} while (0)
 161 #define activate_mm(prev, next) switch_mm((prev), (next), NULL)
 162
 163 #endif /* _ASM_MMU_CONTEXT_H */