1 /*
2 * Based on arch/arm/mm/context.c
3 *
4 * Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
5 * Copyright (C) 2012 ARM Ltd.
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 */
19
20 #include <linux/init.h>
21 #include <linux/sched.h>
22 #include <linux/mm.h>
23 #include <linux/smp.h>
24 #include <linux/percpu.h>
25
26 #include <asm/mmu_context.h>
27 #include <asm/tlbflush.h>
28 #include <asm/cachetype.h>
29
30 #define asid_bits(reg) \
31 (((read_cpuid(ID_AA64MMFR0_EL1) & 0xf0) >> 2) + 8)
32
33 #define ASID_FIRST_VERSION (1 << MAX_ASID_BITS)
34
35 static DEFINE_RAW_SPINLOCK(cpu_asid_lock);
36 unsigned int cpu_last_asid = ASID_FIRST_VERSION;
37
38 /*
39 * We fork()ed a process, and we need a new context for the child to run in.
40 */
__init_new_context(struct task_struct * tsk,struct mm_struct * mm)41 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
42 {
43 mm->context.id = 0;
44 raw_spin_lock_init(&mm->context.id_lock);
45 }
46
flush_context(void)47 static void flush_context(void)
48 {
49 /* set the reserved TTBR0 before flushing the TLB */
50 cpu_set_reserved_ttbr0();
51 flush_tlb_all();
52 if (icache_is_aivivt())
53 __flush_icache_all();
54 }
55
56 #ifdef CONFIG_SMP
57
set_mm_context(struct mm_struct * mm,unsigned int asid)58 static void set_mm_context(struct mm_struct *mm, unsigned int asid)
59 {
60 unsigned long flags;
61
62 /*
63 * Locking needed for multi-threaded applications where the same
64 * mm->context.id could be set from different CPUs during the
65 * broadcast. This function is also called via IPI so the
66 * mm->context.id_lock has to be IRQ-safe.
67 */
68 raw_spin_lock_irqsave(&mm->context.id_lock, flags);
69 if (likely((mm->context.id ^ cpu_last_asid) >> MAX_ASID_BITS)) {
70 /*
71 * Old version of ASID found. Set the new one and reset
72 * mm_cpumask(mm).
73 */
74 mm->context.id = asid;
75 cpumask_clear(mm_cpumask(mm));
76 }
77 raw_spin_unlock_irqrestore(&mm->context.id_lock, flags);
78
79 /*
80 * Set the mm_cpumask(mm) bit for the current CPU.
81 */
82 cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
83 }
84
85 /*
86 * Reset the ASID on the current CPU. This function call is broadcast from the
87 * CPU handling the ASID rollover and holding cpu_asid_lock.
88 */
reset_context(void * info)89 static void reset_context(void *info)
90 {
91 unsigned int asid;
92 unsigned int cpu = smp_processor_id();
93 struct mm_struct *mm = current->active_mm;
94
95 /*
96 * current->active_mm could be init_mm for the idle thread immediately
97 * after secondary CPU boot or hotplug. TTBR0_EL1 is already set to
98 * the reserved value, so no need to reset any context.
99 */
100 if (mm == &init_mm)
101 return;
102
103 smp_rmb();
104 asid = cpu_last_asid + cpu;
105
106 flush_context();
107 set_mm_context(mm, asid);
108
109 /* set the new ASID */
110 cpu_switch_mm(mm->pgd, mm);
111 }
112
113 #else
114
set_mm_context(struct mm_struct * mm,unsigned int asid)115 static inline void set_mm_context(struct mm_struct *mm, unsigned int asid)
116 {
117 mm->context.id = asid;
118 cpumask_copy(mm_cpumask(mm), cpumask_of(smp_processor_id()));
119 }
120
121 #endif
122
__new_context(struct mm_struct * mm)123 void __new_context(struct mm_struct *mm)
124 {
125 unsigned int asid;
126 unsigned int bits = asid_bits();
127
128 raw_spin_lock(&cpu_asid_lock);
129 #ifdef CONFIG_SMP
130 /*
131 * Check the ASID again, in case the change was broadcast from another
132 * CPU before we acquired the lock.
133 */
134 if (!unlikely((mm->context.id ^ cpu_last_asid) >> MAX_ASID_BITS)) {
135 cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
136 raw_spin_unlock(&cpu_asid_lock);
137 return;
138 }
139 #endif
140 /*
141 * At this point, it is guaranteed that the current mm (with an old
142 * ASID) isn't active on any other CPU since the ASIDs are changed
143 * simultaneously via IPI.
144 */
145 asid = ++cpu_last_asid;
146
147 /*
148 * If we've used up all our ASIDs, we need to start a new version and
149 * flush the TLB.
150 */
151 if (unlikely((asid & ((1 << bits) - 1)) == 0)) {
152 /* increment the ASID version */
153 cpu_last_asid += (1 << MAX_ASID_BITS) - (1 << bits);
154 if (cpu_last_asid == 0)
155 cpu_last_asid = ASID_FIRST_VERSION;
156 asid = cpu_last_asid + smp_processor_id();
157 flush_context();
158 #ifdef CONFIG_SMP
159 smp_wmb();
160 smp_call_function(reset_context, NULL, 1);
161 #endif
162 cpu_last_asid += NR_CPUS - 1;
163 }
164
165 set_mm_context(mm, asid);
166 raw_spin_unlock(&cpu_asid_lock);
167 }
168