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 22 #ifdef CONFIG_ARM_LPAE 23 void cpu_set_reserved_ttbr0(void) 24 { 25 unsigned long ttbl = __pa(swapper_pg_dir); 26 unsigned long ttbh = 0; 27 28 /* 29 * Set TTBR0 to swapper_pg_dir which contains only global entries. The 30 * ASID is set to 0. 31 */ 32 asm volatile( 33 " mcrr p15, 0, %0, %1, c2 @ set TTBR0\n" 34 : 35 : "r" (ttbl), "r" (ttbh)); 36 isb(); 37 } 38 #else 39 void cpu_set_reserved_ttbr0(void) 40 { 41 u32 ttb; 42 /* Copy TTBR1 into TTBR0 */ 43 asm volatile( 44 " mrc p15, 0, %0, c2, c0, 1 @ read TTBR1\n" 45 " mcr p15, 0, %0, c2, c0, 0 @ set TTBR0\n" 46 : "=r" (ttb)); 47 isb(); 48 } 49 #endif 50 51 /* 52 * We fork()ed a process, and we need a new context for the child 53 * to run in. 54 */ 55 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm) 56 { 57 mm->context.id = 0; 58 raw_spin_lock_init(&mm->context.id_lock); 59 } 60 61 static void flush_context(void) 62 { 63 cpu_set_reserved_ttbr0(); 64 local_flush_tlb_all(); 65 if (icache_is_vivt_asid_tagged()) { 66 __flush_icache_all(); 67 dsb(); 68 } 69 } 70 71 #ifdef CONFIG_SMP 72 73 static void set_mm_context(struct mm_struct *mm, unsigned int asid) 74 { 75 unsigned long flags; 76 77 /* 78 * Locking needed for multi-threaded applications where the 79 * same mm->context.id could be set from different CPUs during 80 * the broadcast. This function is also called via IPI so the 81 * mm->context.id_lock has to be IRQ-safe. 82 */ 83 raw_spin_lock_irqsave(&mm->context.id_lock, flags); 84 if (likely((mm->context.id ^ cpu_last_asid) >> ASID_BITS)) { 85 /* 86 * Old version of ASID found. Set the new one and 87 * reset mm_cpumask(mm). 88 */ 89 mm->context.id = asid; 90 cpumask_clear(mm_cpumask(mm)); 91 } 92 raw_spin_unlock_irqrestore(&mm->context.id_lock, flags); 93 94 /* 95 * Set the mm_cpumask(mm) bit for the current CPU. 96 */ 97 cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm)); 98 } 99 100 /* 101 * Reset the ASID on the current CPU. This function call is broadcast 102 * from the CPU handling the ASID rollover and holding cpu_asid_lock. 103 */ 104 static void reset_context(void *info) 105 { 106 unsigned int asid; 107 unsigned int cpu = smp_processor_id(); 108 struct mm_struct *mm = current->active_mm; 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_switch_mm(mm->pgd, mm); 118 } 119 120 #else 121 122 static inline void set_mm_context(struct mm_struct *mm, unsigned int asid) 123 { 124 mm->context.id = asid; 125 cpumask_copy(mm_cpumask(mm), cpumask_of(smp_processor_id())); 126 } 127 128 #endif 129 130 void __new_context(struct mm_struct *mm) 131 { 132 unsigned int asid; 133 134 raw_spin_lock(&cpu_asid_lock); 135 #ifdef CONFIG_SMP 136 /* 137 * Check the ASID again, in case the change was broadcast from 138 * another CPU before we acquired the lock. 139 */ 140 if (unlikely(((mm->context.id ^ cpu_last_asid) >> ASID_BITS) == 0)) { 141 cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm)); 142 raw_spin_unlock(&cpu_asid_lock); 143 return; 144 } 145 #endif 146 /* 147 * At this point, it is guaranteed that the current mm (with 148 * an old ASID) isn't active on any other CPU since the ASIDs 149 * are changed simultaneously via IPI. 150 */ 151 asid = ++cpu_last_asid; 152 if (asid == 0) 153 asid = cpu_last_asid = ASID_FIRST_VERSION; 154 155 /* 156 * If we've used up all our ASIDs, we need 157 * to start a new version and flush the TLB. 158 */ 159 if (unlikely((asid & ~ASID_MASK) == 0)) { 160 asid = cpu_last_asid + smp_processor_id() + 1; 161 flush_context(); 162 #ifdef CONFIG_SMP 163 smp_wmb(); 164 smp_call_function(reset_context, NULL, 1); 165 #endif 166 cpu_last_asid += NR_CPUS; 167 } 168 169 set_mm_context(mm, asid); 170 raw_spin_unlock(&cpu_asid_lock); 171 } 172