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
35static DEFINE_RAW_SPINLOCK(cpu_asid_lock);
36unsigned 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 */
41void __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
47static 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
58static 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 */
89static 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
115static 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
123void __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