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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
19static DEFINE_SPINLOCK(cpu_asid_lock);
20unsigned int cpu_last_asid = ASID_FIRST_VERSION;
21#ifdef CONFIG_SMP
22DEFINE_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 */
31void __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
37static 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
51static 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 */
82static 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
108static 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
116void __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}
1/*
2 * linux/arch/arm/mm/context.c
3 *
4 * Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
5 * Copyright (C) 2012 ARM Limited
6 *
7 * Author: Will Deacon <will.deacon@arm.com>
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
12 */
13#include <linux/init.h>
14#include <linux/sched.h>
15#include <linux/mm.h>
16#include <linux/smp.h>
17#include <linux/percpu.h>
18
19#include <asm/mmu_context.h>
20#include <asm/smp_plat.h>
21#include <asm/thread_notify.h>
22#include <asm/tlbflush.h>
23#include <asm/proc-fns.h>
24
25/*
26 * On ARMv6, we have the following structure in the Context ID:
27 *
28 * 31 7 0
29 * +-------------------------+-----------+
30 * | process ID | ASID |
31 * +-------------------------+-----------+
32 * | context ID |
33 * +-------------------------------------+
34 *
35 * The ASID is used to tag entries in the CPU caches and TLBs.
36 * The context ID is used by debuggers and trace logic, and
37 * should be unique within all running processes.
38 *
39 * In big endian operation, the two 32 bit words are swapped if accessed
40 * by non-64-bit operations.
41 */
42#define ASID_FIRST_VERSION (1ULL << ASID_BITS)
43#define NUM_USER_ASIDS ASID_FIRST_VERSION
44
45static DEFINE_RAW_SPINLOCK(cpu_asid_lock);
46static atomic64_t asid_generation = ATOMIC64_INIT(ASID_FIRST_VERSION);
47static DECLARE_BITMAP(asid_map, NUM_USER_ASIDS);
48
49static DEFINE_PER_CPU(atomic64_t, active_asids);
50static DEFINE_PER_CPU(u64, reserved_asids);
51static cpumask_t tlb_flush_pending;
52
53#ifdef CONFIG_ARM_ERRATA_798181
54void a15_erratum_get_cpumask(int this_cpu, struct mm_struct *mm,
55 cpumask_t *mask)
56{
57 int cpu;
58 unsigned long flags;
59 u64 context_id, asid;
60
61 raw_spin_lock_irqsave(&cpu_asid_lock, flags);
62 context_id = mm->context.id.counter;
63 for_each_online_cpu(cpu) {
64 if (cpu == this_cpu)
65 continue;
66 /*
67 * We only need to send an IPI if the other CPUs are
68 * running the same ASID as the one being invalidated.
69 */
70 asid = per_cpu(active_asids, cpu).counter;
71 if (asid == 0)
72 asid = per_cpu(reserved_asids, cpu);
73 if (context_id == asid)
74 cpumask_set_cpu(cpu, mask);
75 }
76 raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
77}
78#endif
79
80#ifdef CONFIG_ARM_LPAE
81/*
82 * With LPAE, the ASID and page tables are updated atomicly, so there is
83 * no need for a reserved set of tables (the active ASID tracking prevents
84 * any issues across a rollover).
85 */
86#define cpu_set_reserved_ttbr0()
87#else
88static void cpu_set_reserved_ttbr0(void)
89{
90 u32 ttb;
91 /*
92 * Copy TTBR1 into TTBR0.
93 * This points at swapper_pg_dir, which contains only global
94 * entries so any speculative walks are perfectly safe.
95 */
96 asm volatile(
97 " mrc p15, 0, %0, c2, c0, 1 @ read TTBR1\n"
98 " mcr p15, 0, %0, c2, c0, 0 @ set TTBR0\n"
99 : "=r" (ttb));
100 isb();
101}
102#endif
103
104#ifdef CONFIG_PID_IN_CONTEXTIDR
105static int contextidr_notifier(struct notifier_block *unused, unsigned long cmd,
106 void *t)
107{
108 u32 contextidr;
109 pid_t pid;
110 struct thread_info *thread = t;
111
112 if (cmd != THREAD_NOTIFY_SWITCH)
113 return NOTIFY_DONE;
114
115 pid = task_pid_nr(thread->task) << ASID_BITS;
116 asm volatile(
117 " mrc p15, 0, %0, c13, c0, 1\n"
118 " and %0, %0, %2\n"
119 " orr %0, %0, %1\n"
120 " mcr p15, 0, %0, c13, c0, 1\n"
121 : "=r" (contextidr), "+r" (pid)
122 : "I" (~ASID_MASK));
123 isb();
124
125 return NOTIFY_OK;
126}
127
128static struct notifier_block contextidr_notifier_block = {
129 .notifier_call = contextidr_notifier,
130};
131
132static int __init contextidr_notifier_init(void)
133{
134 return thread_register_notifier(&contextidr_notifier_block);
135}
136arch_initcall(contextidr_notifier_init);
137#endif
138
139static void flush_context(unsigned int cpu)
140{
141 int i;
142 u64 asid;
143
144 /* Update the list of reserved ASIDs and the ASID bitmap. */
145 bitmap_clear(asid_map, 0, NUM_USER_ASIDS);
146 for_each_possible_cpu(i) {
147 asid = atomic64_xchg(&per_cpu(active_asids, i), 0);
148 /*
149 * If this CPU has already been through a
150 * rollover, but hasn't run another task in
151 * the meantime, we must preserve its reserved
152 * ASID, as this is the only trace we have of
153 * the process it is still running.
154 */
155 if (asid == 0)
156 asid = per_cpu(reserved_asids, i);
157 __set_bit(asid & ~ASID_MASK, asid_map);
158 per_cpu(reserved_asids, i) = asid;
159 }
160
161 /* Queue a TLB invalidate and flush the I-cache if necessary. */
162 cpumask_setall(&tlb_flush_pending);
163
164 if (icache_is_vivt_asid_tagged())
165 __flush_icache_all();
166}
167
168static bool check_update_reserved_asid(u64 asid, u64 newasid)
169{
170 int cpu;
171 bool hit = false;
172
173 /*
174 * Iterate over the set of reserved ASIDs looking for a match.
175 * If we find one, then we can update our mm to use newasid
176 * (i.e. the same ASID in the current generation) but we can't
177 * exit the loop early, since we need to ensure that all copies
178 * of the old ASID are updated to reflect the mm. Failure to do
179 * so could result in us missing the reserved ASID in a future
180 * generation.
181 */
182 for_each_possible_cpu(cpu) {
183 if (per_cpu(reserved_asids, cpu) == asid) {
184 hit = true;
185 per_cpu(reserved_asids, cpu) = newasid;
186 }
187 }
188
189 return hit;
190}
191
192static u64 new_context(struct mm_struct *mm, unsigned int cpu)
193{
194 static u32 cur_idx = 1;
195 u64 asid = atomic64_read(&mm->context.id);
196 u64 generation = atomic64_read(&asid_generation);
197
198 if (asid != 0) {
199 u64 newasid = generation | (asid & ~ASID_MASK);
200
201 /*
202 * If our current ASID was active during a rollover, we
203 * can continue to use it and this was just a false alarm.
204 */
205 if (check_update_reserved_asid(asid, newasid))
206 return newasid;
207
208 /*
209 * We had a valid ASID in a previous life, so try to re-use
210 * it if possible.,
211 */
212 asid &= ~ASID_MASK;
213 if (!__test_and_set_bit(asid, asid_map))
214 return newasid;
215 }
216
217 /*
218 * Allocate a free ASID. If we can't find one, take a note of the
219 * currently active ASIDs and mark the TLBs as requiring flushes.
220 * We always count from ASID #1, as we reserve ASID #0 to switch
221 * via TTBR0 and to avoid speculative page table walks from hitting
222 * in any partial walk caches, which could be populated from
223 * overlapping level-1 descriptors used to map both the module
224 * area and the userspace stack.
225 */
226 asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, cur_idx);
227 if (asid == NUM_USER_ASIDS) {
228 generation = atomic64_add_return(ASID_FIRST_VERSION,
229 &asid_generation);
230 flush_context(cpu);
231 asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1);
232 }
233
234 __set_bit(asid, asid_map);
235 cur_idx = asid;
236 cpumask_clear(mm_cpumask(mm));
237 return asid | generation;
238}
239
240void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk)
241{
242 unsigned long flags;
243 unsigned int cpu = smp_processor_id();
244 u64 asid;
245
246 if (unlikely(mm->context.vmalloc_seq != init_mm.context.vmalloc_seq))
247 __check_vmalloc_seq(mm);
248
249 /*
250 * We cannot update the pgd and the ASID atomicly with classic
251 * MMU, so switch exclusively to global mappings to avoid
252 * speculative page table walking with the wrong TTBR.
253 */
254 cpu_set_reserved_ttbr0();
255
256 asid = atomic64_read(&mm->context.id);
257 if (!((asid ^ atomic64_read(&asid_generation)) >> ASID_BITS)
258 && atomic64_xchg(&per_cpu(active_asids, cpu), asid))
259 goto switch_mm_fastpath;
260
261 raw_spin_lock_irqsave(&cpu_asid_lock, flags);
262 /* Check that our ASID belongs to the current generation. */
263 asid = atomic64_read(&mm->context.id);
264 if ((asid ^ atomic64_read(&asid_generation)) >> ASID_BITS) {
265 asid = new_context(mm, cpu);
266 atomic64_set(&mm->context.id, asid);
267 }
268
269 if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending)) {
270 local_flush_bp_all();
271 local_flush_tlb_all();
272 }
273
274 atomic64_set(&per_cpu(active_asids, cpu), asid);
275 cpumask_set_cpu(cpu, mm_cpumask(mm));
276 raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
277
278switch_mm_fastpath:
279 cpu_switch_mm(mm->pgd, mm);
280}