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 <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
  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
  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  */
  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  */
  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  */
 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  */
 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  */
 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 */