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_RAW_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 raw_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 raw_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 raw_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 raw_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 raw_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 raw_spin_unlock(&cpu_asid_lock); 157 } 158