LXR linux/arch/mn10300/include/asm/mmu

   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
  35extern 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 */
  53static 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 */
  75static 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 */
  93static 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 */
 113static 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 */
 121static 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 */
 139