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 <asm/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_MASK         0x000000ffUL
  31 #define MMU_CONTEXT_VERSION_MASK        0xffffff00UL
  32 #define MMU_CONTEXT_FIRST_VERSION       0x00000100UL
  33 #define MMU_NO_CONTEXT                  0x00000000UL
  34
  35 extern unsigned long mmu_context_cache[NR_CPUS];
  36 #define mm_context(mm)  (mm->context.tlbpid[smp_processor_id()])
  37
  38 #define enter_lazy_tlb(mm, tsk) do {} while (0)
  39
  40 #ifdef CONFIG_SMP
  41 #define cpu_ran_vm(cpu, mm) \
  42         cpumask_set_cpu((cpu), mm_cpumask(mm))
  43 #define cpu_maybe_ran_vm(cpu, mm) \
  44         cpumask_test_and_set_cpu((cpu), mm_cpumask(mm))
  45 #else
  46 #define cpu_ran_vm(cpu, mm)             do {} while (0)
  47 #define cpu_maybe_ran_vm(cpu, mm)       true
  48 #endif /* CONFIG_SMP */
  49
  50 /*
  51  * allocate an MMU context
  52  */
  53 static inline unsigned long allocate_mmu_context(struct mm_struct *mm)
  54 {
  55         unsigned long *pmc = &mmu_context_cache[smp_processor_id()];
  56         unsigned long mc = ++(*pmc);
  57
  58         if (!(mc & MMU_CONTEXT_TLBPID_MASK)) {
  59                 /* we exhausted the TLB PIDs of this version on this CPU, so we
  60                  * flush this CPU's TLB in its entirety and start new cycle */
  61                 flush_tlb_all();
  62
  63                 /* fix the TLB version if needed (we avoid version #0 so as to
  64                  * distingush MMU_NO_CONTEXT) */
  65                 if (!mc)
  66                         *pmc = mc = MMU_CONTEXT_FIRST_VERSION;
  67         }
  68         mm_context(mm) = mc;
  69         return mc;
  70 }
  71
  72 /*
  73  * get an MMU context if one is needed
  74  */
  75 static inline unsigned long get_mmu_context(struct mm_struct *mm)
  76 {
  77         unsigned long mc = MMU_NO_CONTEXT, cache;
  78
  79         if (mm) {
  80                 cache = mmu_context_cache[smp_processor_id()];
  81                 mc = mm_context(mm);
  82
  83                 /* if we have an old version of the context, replace it */
  84                 if ((mc ^ cache) & MMU_CONTEXT_VERSION_MASK)
  85                         mc = allocate_mmu_context(mm);
  86         }
  87         return mc;
  88 }
  89
  90 /*
  91  * initialise the context related info for a new mm_struct instance
  92  */
  93 static inline int init_new_context(struct task_struct *tsk,
  94                                    struct mm_struct *mm)
  95 {
  96         int num_cpus = NR_CPUS, i;
  97
  98         for (i = 0; i < num_cpus; i++)
  99                 mm->context.tlbpid[i] = MMU_NO_CONTEXT;
 100         return 0;
 101 }
 102
 103 /*
 104  * destroy context related info for an mm_struct that is about to be put to
 105  * rest
 106  */
 107 #define destroy_context(mm)     do { } while (0)
 108
 109 /*
 110  * after we have set current->mm to a new value, this activates the context for
 111  * the new mm so we see the new mappings.
 112  */
 113 static inline void activate_context(struct mm_struct *mm, int cpu)
 114 {
 115         PIDR = get_mmu_context(mm) & MMU_CONTEXT_TLBPID_MASK;
 116 }
 117
 118 /*
 119  * change between virtual memory sets
 120  */
 121 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 122                              struct task_struct *tsk)
 123 {
 124         int cpu = smp_processor_id();
 125
 126         if (prev != next) {
 127                 cpu_ran_vm(cpu, next);
 128                 activate_context(next, cpu);
 129                 PTBR = (unsigned long) next->pgd;
 130         } else if (!cpu_maybe_ran_vm(cpu, next)) {
 131                 activate_context(next, cpu);
 132         }
 133 }
 134
 135 #define deactivate_mm(tsk, mm)  do {} while (0)
 136 #define activate_mm(prev, next) switch_mm((prev), (next), NULL)
 137
 138 #endif /* _ASM_MMU_CONTEXT_H */