1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * SMP initialisation and IPI support
4 * Based on arch/arm64/kernel/smp.c
5 *
6 * Copyright (C) 2012 ARM Ltd.
7 * Copyright (C) 2015 Regents of the University of California
8 * Copyright (C) 2017 SiFive
9 */
10
11 #include <linux/arch_topology.h>
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/kernel.h>
15 #include <linux/mm.h>
16 #include <linux/sched.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/notifier.h>
19 #include <linux/cpu.h>
20 #include <linux/percpu.h>
21 #include <linux/delay.h>
22 #include <linux/err.h>
23 #include <linux/irq.h>
24 #include <linux/of.h>
25 #include <linux/sched/task_stack.h>
26 #include <linux/sched/mm.h>
27 #include <asm/irq.h>
28 #include <asm/mmu_context.h>
29 #include <asm/tlbflush.h>
30 #include <asm/sections.h>
31 #include <asm/sbi.h>
32 #include <asm/smp.h>
33
34 #include "head.h"
35
36 void *__cpu_up_stack_pointer[NR_CPUS];
37 void *__cpu_up_task_pointer[NR_CPUS];
38 static DECLARE_COMPLETION(cpu_running);
39
smp_prepare_boot_cpu(void)40 void __init smp_prepare_boot_cpu(void)
41 {
42 init_cpu_topology();
43 }
44
smp_prepare_cpus(unsigned int max_cpus)45 void __init smp_prepare_cpus(unsigned int max_cpus)
46 {
47 int cpuid;
48
49 /* This covers non-smp usecase mandated by "nosmp" option */
50 if (max_cpus == 0)
51 return;
52
53 for_each_possible_cpu(cpuid) {
54 if (cpuid == smp_processor_id())
55 continue;
56 set_cpu_present(cpuid, true);
57 }
58 }
59
setup_smp(void)60 void __init setup_smp(void)
61 {
62 struct device_node *dn;
63 int hart;
64 bool found_boot_cpu = false;
65 int cpuid = 1;
66
67 for_each_of_cpu_node(dn) {
68 hart = riscv_of_processor_hartid(dn);
69 if (hart < 0)
70 continue;
71
72 if (hart == cpuid_to_hartid_map(0)) {
73 BUG_ON(found_boot_cpu);
74 found_boot_cpu = 1;
75 continue;
76 }
77 if (cpuid >= NR_CPUS) {
78 pr_warn("Invalid cpuid [%d] for hartid [%d]\n",
79 cpuid, hart);
80 break;
81 }
82
83 cpuid_to_hartid_map(cpuid) = hart;
84 cpuid++;
85 }
86
87 BUG_ON(!found_boot_cpu);
88
89 if (cpuid > nr_cpu_ids)
90 pr_warn("Total number of cpus [%d] is greater than nr_cpus option value [%d]\n",
91 cpuid, nr_cpu_ids);
92
93 for (cpuid = 1; cpuid < nr_cpu_ids; cpuid++) {
94 if (cpuid_to_hartid_map(cpuid) != INVALID_HARTID)
95 set_cpu_possible(cpuid, true);
96 }
97 }
98
__cpu_up(unsigned int cpu,struct task_struct * tidle)99 int __cpu_up(unsigned int cpu, struct task_struct *tidle)
100 {
101 int ret = 0;
102 int hartid = cpuid_to_hartid_map(cpu);
103 tidle->thread_info.cpu = cpu;
104
105 /*
106 * On RISC-V systems, all harts boot on their own accord. Our _start
107 * selects the first hart to boot the kernel and causes the remainder
108 * of the harts to spin in a loop waiting for their stack pointer to be
109 * setup by that main hart. Writing __cpu_up_stack_pointer signals to
110 * the spinning harts that they can continue the boot process.
111 */
112 smp_mb();
113 WRITE_ONCE(__cpu_up_stack_pointer[hartid],
114 task_stack_page(tidle) + THREAD_SIZE);
115 WRITE_ONCE(__cpu_up_task_pointer[hartid], tidle);
116
117 lockdep_assert_held(&cpu_running);
118 wait_for_completion_timeout(&cpu_running,
119 msecs_to_jiffies(1000));
120
121 if (!cpu_online(cpu)) {
122 pr_crit("CPU%u: failed to come online\n", cpu);
123 ret = -EIO;
124 }
125
126 return ret;
127 }
128
smp_cpus_done(unsigned int max_cpus)129 void __init smp_cpus_done(unsigned int max_cpus)
130 {
131 }
132
133 /*
134 * C entry point for a secondary processor.
135 */
smp_callin(void)136 asmlinkage __visible void __init smp_callin(void)
137 {
138 struct mm_struct *mm = &init_mm;
139
140 /* All kernel threads share the same mm context. */
141 mmgrab(mm);
142 current->active_mm = mm;
143
144 trap_init();
145 notify_cpu_starting(smp_processor_id());
146 update_siblings_masks(smp_processor_id());
147 set_cpu_online(smp_processor_id(), 1);
148 /*
149 * Remote TLB flushes are ignored while the CPU is offline, so emit
150 * a local TLB flush right now just in case.
151 */
152 local_flush_tlb_all();
153 complete(&cpu_running);
154 /*
155 * Disable preemption before enabling interrupts, so we don't try to
156 * schedule a CPU that hasn't actually started yet.
157 */
158 preempt_disable();
159 local_irq_enable();
160 cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
161 }
162
