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 <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
  39static 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
  46static 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
  56extern 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 */
  63static 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 */
  85static 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 */
 103static 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 */
 117static 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 */
 143static 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 */
 162