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 #ifdef CONFIG_ARM_LPAE
  26 #define cpu_set_asid(asid) {                                            \
  27         unsigned long ttbl, ttbh;                                       \
  28         asm volatile(                                                   \
  29         "       mrrc    p15, 0, %0, %1, c2              @ read TTBR0\n" \
  30         "       mov     %1, %2, lsl #(48 - 32)          @ set ASID\n"   \
  31         "       mcrr    p15, 0, %0, %1, c2              @ set TTBR0\n"  \
  32         : "=&r" (ttbl), "=&r" (ttbh)                                    \
  33         : "r" (asid & ~ASID_MASK));                                     \
  34 }
  35 #else
  36 #define cpu_set_asid(asid) \
  37         asm("   mcr     p15, 0, %0, c13, c0, 1\n" : : "r" (asid))
  38 #endif
  39
  40 /*
  41  * We fork()ed a process, and we need a new context for the child
  42  * to run in.  We reserve version 0 for initial tasks so we will
  43  * always allocate an ASID. The ASID 0 is reserved for the TTBR
  44  * register changing sequence.
  45  */
  46 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  47 {
  48         mm->context.id = 0;
  49         spin_lock_init(&mm->context.id_lock);
  50 }
  51
  52 static void flush_context(void)
  53 {
  54         /* set the reserved ASID before flushing the TLB */
  55         cpu_set_asid(0);
  56         isb();
  57         local_flush_tlb_all();
  58         if (icache_is_vivt_asid_tagged()) {
  59                 __flush_icache_all();
  60                 dsb();
  61         }
  62 }
  63
  64 #ifdef CONFIG_SMP
  65
  66 static void set_mm_context(struct mm_struct *mm, unsigned int asid)
  67 {
  68         unsigned long flags;
  69
  70         /*
  71          * Locking needed for multi-threaded applications where the
  72          * same mm->context.id could be set from different CPUs during
  73          * the broadcast. This function is also called via IPI so the
  74          * mm->context.id_lock has to be IRQ-safe.
  75          */
  76         spin_lock_irqsave(&mm->context.id_lock, flags);
  77         if (likely((mm->context.id ^ cpu_last_asid) >> ASID_BITS)) {
  78                 /*
  79                  * Old version of ASID found. Set the new one and
  80                  * reset mm_cpumask(mm).
  81                  */
  82                 mm->context.id = asid;
  83                 cpumask_clear(mm_cpumask(mm));
  84         }
  85         spin_unlock_irqrestore(&mm->context.id_lock, flags);
  86
  87         /*
  88          * Set the mm_cpumask(mm) bit for the current CPU.
  89          */
  90         cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
  91 }
  92
  93 /*
  94  * Reset the ASID on the current CPU. This function call is broadcast
  95  * from the CPU handling the ASID rollover and holding cpu_asid_lock.
  96  */
  97 static void reset_context(void *info)
  98 {
  99         unsigned int asid;
 100         unsigned int cpu = smp_processor_id();
 101         struct mm_struct *mm = per_cpu(current_mm, cpu);
 102
 103         /*
 104          * Check if a current_mm was set on this CPU as it might still
 105          * be in the early booting stages and using the reserved ASID.
 106          */
 107         if (!mm)
 108                 return;
 109
 110         smp_rmb();
 111         asid = cpu_last_asid + cpu + 1;
 112
 113         flush_context();
 114         set_mm_context(mm, asid);
 115
 116         /* set the new ASID */
 117         cpu_set_asid(mm->context.id);
 118         isb();
 119 }
 120
 121 #else
 122
 123 static inline void set_mm_context(struct mm_struct *mm, unsigned int asid)
 124 {
 125         mm->context.id = asid;
 126         cpumask_copy(mm_cpumask(mm), cpumask_of(smp_processor_id()));
 127 }
 128
 129 #endif
 130
 131 void __new_context(struct mm_struct *mm)
 132 {
 133         unsigned int asid;
 134
 135         spin_lock(&cpu_asid_lock);
 136 #ifdef CONFIG_SMP
 137         /*
 138          * Check the ASID again, in case the change was broadcast from
 139          * another CPU before we acquired the lock.
 140          */
 141         if (unlikely(((mm->context.id ^ cpu_last_asid) >> ASID_BITS) == 0)) {
 142                 cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
 143                 spin_unlock(&cpu_asid_lock);
 144                 return;
 145         }
 146 #endif
 147         /*
 148          * At this point, it is guaranteed that the current mm (with
 149          * an old ASID) isn't active on any other CPU since the ASIDs
 150          * are changed simultaneously via IPI.
 151          */
 152         asid = ++cpu_last_asid;
 153         if (asid == 0)
 154                 asid = cpu_last_asid = ASID_FIRST_VERSION;
 155
 156         /*
 157          * If we've used up all our ASIDs, we need
 158          * to start a new version and flush the TLB.
 159          */
 160         if (unlikely((asid & ~ASID_MASK) == 0)) {
 161                 asid = cpu_last_asid + smp_processor_id() + 1;
 162                 flush_context();
 163 #ifdef CONFIG_SMP
 164                 smp_wmb();
 165                 smp_call_function(reset_context, NULL, 1);
 166 #endif
 167                 cpu_last_asid += NR_CPUS;
 168         }
 169
 170         set_mm_context(mm, asid);
 171         spin_unlock(&cpu_asid_lock);
 172 }