arch/arm/mm/context.c

   1 /*
   2  *  linux/arch/arm/mm/context.c
   3  *
   4  *  Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10 #include <linux/init.h>
  11 #include <linux/sched.h>
  12 #include <linux/mm.h>
  13 #include <linux/smp.h>
  14 #include <linux/percpu.h>
  15
  16 #include <asm/mmu_context.h>
  17 #include <asm/tlbflush.h>
  18
  19 static DEFINE_SPINLOCK(cpu_asid_lock);
  20 unsigned int cpu_last_asid = ASID_FIRST_VERSION;
  21 #ifdef CONFIG_SMP
  22 DEFINE_PER_CPU(struct mm_struct *, current_mm);
  23 #endif
  24
  25 /*
  26  * We fork()ed a process, and we need a new context for the child
  27  * to run in.  We reserve version 0 for initial tasks so we will
  28  * always allocate an ASID. The ASID 0 is reserved for the TTBR
  29  * register changing sequence.
  30  */
  31 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  32 {
  33         mm->context.id = 0;
  34         spin_lock_init(&mm->context.id_lock);
  35 }
  36
  37 static void flush_context(void)
  38 {
  39         /* set the reserved ASID before flushing the TLB */
  40         asm("mcr        p15, 0, %0, c13, c0, 1\n" : : "r" (0));
  41         isb();
  42         local_flush_tlb_all();
  43         if (icache_is_vivt_asid_tagged()) {
  44                 __flush_icache_all();
  45                 dsb();
  46         }
  47 }
  48
  49 #ifdef CONFIG_SMP
  50
  51 static void set_mm_context(struct mm_struct *mm, unsigned int asid)
  52 {
  53         unsigned long flags;
  54
  55         /*
  56          * Locking needed for multi-threaded applications where the
  57          * same mm->context.id could be set from different CPUs during
  58          * the broadcast. This function is also called via IPI so the
  59          * mm->context.id_lock has to be IRQ-safe.
  60          */
  61         spin_lock_irqsave(&mm->context.id_lock, flags);
  62         if (likely((mm->context.id ^ cpu_last_asid) >> ASID_BITS)) {
  63                 /*
  64                  * Old version of ASID found. Set the new one and
  65                  * reset mm_cpumask(mm).
  66                  */
  67                 mm->context.id = asid;
  68                 cpumask_clear(mm_cpumask(mm));
  69         }
  70         spin_unlock_irqrestore(&mm->context.id_lock, flags);
  71
  72         /*
  73          * Set the mm_cpumask(mm) bit for the current CPU.
  74          */
  75         cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
  76 }
  77
  78 /*
  79  * Reset the ASID on the current CPU. This function call is broadcast
  80  * from the CPU handling the ASID rollover and holding cpu_asid_lock.
  81  */
  82 static void reset_context(void *info)
  83 {
  84         unsigned int asid;
  85         unsigned int cpu = smp_processor_id();
  86         struct mm_struct *mm = per_cpu(current_mm, cpu);
  87
  88         /*
  89          * Check if a current_mm was set on this CPU as it might still
  90          * be in the early booting stages and using the reserved ASID.
  91          */
  92         if (!mm)
  93                 return;
  94
  95         smp_rmb();
  96         asid = cpu_last_asid + cpu + 1;
  97
  98         flush_context();
  99         set_mm_context(mm, asid);
 100
 101         /* set the new ASID */
 102         asm("mcr        p15, 0, %0, c13, c0, 1\n" : : "r" (mm->context.id));
 103         isb();
 104 }
 105
 106 #else
 107
 108 static inline void set_mm_context(struct mm_struct *mm, unsigned int asid)
 109 {
 110         mm->context.id = asid;
 111         cpumask_copy(mm_cpumask(mm), cpumask_of(smp_processor_id()));
 112 }
 113
 114 #endif
 115
 116 void __new_context(struct mm_struct *mm)
 117 {
 118         unsigned int asid;
 119
 120         spin_lock(&cpu_asid_lock);
 121 #ifdef CONFIG_SMP
 122         /*
 123          * Check the ASID again, in case the change was broadcast from
 124          * another CPU before we acquired the lock.
 125          */
 126         if (unlikely(((mm->context.id ^ cpu_last_asid) >> ASID_BITS) == 0)) {
 127                 cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
 128                 spin_unlock(&cpu_asid_lock);
 129                 return;
 130         }
 131 #endif
 132         /*
 133          * At this point, it is guaranteed that the current mm (with
 134          * an old ASID) isn't active on any other CPU since the ASIDs
 135          * are changed simultaneously via IPI.
 136          */
 137         asid = ++cpu_last_asid;
 138         if (asid == 0)
 139                 asid = cpu_last_asid = ASID_FIRST_VERSION;
 140
 141         /*
 142          * If we've used up all our ASIDs, we need
 143          * to start a new version and flush the TLB.
 144          */
 145         if (unlikely((asid & ~ASID_MASK) == 0)) {
 146                 asid = cpu_last_asid + smp_processor_id() + 1;
 147                 flush_context();
 148 #ifdef CONFIG_SMP
 149                 smp_wmb();
 150                 smp_call_function(reset_context, NULL, 1);
 151 #endif
 152                 cpu_last_asid += NR_CPUS;
 153         }
 154
 155         set_mm_context(mm, asid);
 156         spin_unlock(&cpu_asid_lock);
 157 }