arch/riscv/kernel/smpboot.c

   1 /*
   2  * SMP initialisation and IPI support
   3  * Based on arch/arm64/kernel/smp.c
   4  *
   5  * Copyright (C) 2012 ARM Ltd.
   6  * Copyright (C) 2015 Regents of the University of California
   7  * Copyright (C) 2017 SiFive
   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  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  */
  18
  19 #include <linux/module.h>
  20 #include <linux/init.h>
  21 #include <linux/kernel.h>
  22 #include <linux/mm.h>
  23 #include <linux/sched.h>
  24 #include <linux/kernel_stat.h>
  25 #include <linux/notifier.h>
  26 #include <linux/cpu.h>
  27 #include <linux/percpu.h>
  28 #include <linux/delay.h>
  29 #include <linux/err.h>
  30 #include <linux/irq.h>
  31 #include <linux/of.h>
  32 #include <linux/sched/task_stack.h>
  33 #include <linux/sched/mm.h>
  34 #include <asm/irq.h>
  35 #include <asm/mmu_context.h>
  36 #include <asm/tlbflush.h>
  37 #include <asm/sections.h>
  38 #include <asm/sbi.h>
  39
  40 void *__cpu_up_stack_pointer[NR_CPUS];
  41 void *__cpu_up_task_pointer[NR_CPUS];
  42 static DECLARE_COMPLETION(cpu_running);
  43
  44 void __init smp_prepare_boot_cpu(void)
  45 {
  46 }
  47
  48 void __init smp_prepare_cpus(unsigned int max_cpus)
  49 {
  50 }
  51
  52 void __init setup_smp(void)
  53 {
  54         struct device_node *dn;
  55         int hart;
  56         bool found_boot_cpu = false;
  57         int cpuid = 1;
  58
  59         for_each_of_cpu_node(dn) {
  60                 hart = riscv_of_processor_hartid(dn);
  61                 if (hart < 0)
  62                         continue;
  63
  64                 if (hart == cpuid_to_hartid_map(0)) {
  65                         BUG_ON(found_boot_cpu);
  66                         found_boot_cpu = 1;
  67                         continue;
  68                 }
  69                 if (cpuid >= NR_CPUS) {
  70                         pr_warn("Invalid cpuid [%d] for hartid [%d]\n",
  71                                 cpuid, hart);
  72                         break;
  73                 }
  74
  75                 cpuid_to_hartid_map(cpuid) = hart;
  76                 set_cpu_possible(cpuid, true);
  77                 set_cpu_present(cpuid, true);
  78                 cpuid++;
  79         }
  80
  81         BUG_ON(!found_boot_cpu);
  82 }
  83
  84 int __cpu_up(unsigned int cpu, struct task_struct *tidle)
  85 {
  86         int ret = 0;
  87         int hartid = cpuid_to_hartid_map(cpu);
  88         tidle->thread_info.cpu = cpu;
  89
  90         /*
  91          * On RISC-V systems, all harts boot on their own accord.  Our _start
  92          * selects the first hart to boot the kernel and causes the remainder
  93          * of the harts to spin in a loop waiting for their stack pointer to be
  94          * setup by that main hart.  Writing __cpu_up_stack_pointer signals to
  95          * the spinning harts that they can continue the boot process.
  96          */
  97         smp_mb();
  98         WRITE_ONCE(__cpu_up_stack_pointer[hartid],
  99                   task_stack_page(tidle) + THREAD_SIZE);
 100         WRITE_ONCE(__cpu_up_task_pointer[hartid], tidle);
 101
 102         lockdep_assert_held(&cpu_running);
 103         wait_for_completion_timeout(&cpu_running,
 104                                             msecs_to_jiffies(1000));
 105
 106         if (!cpu_online(cpu)) {
 107                 pr_crit("CPU%u: failed to come online\n", cpu);
 108                 ret = -EIO;
 109         }
 110
 111         return ret;
 112 }
 113
 114 void __init smp_cpus_done(unsigned int max_cpus)
 115 {
 116 }
 117
 118 /*
 119  * C entry point for a secondary processor.
 120  */
 121 asmlinkage void __init smp_callin(void)
 122 {
 123         struct mm_struct *mm = &init_mm;
 124
 125         /* All kernel threads share the same mm context.  */
 126         mmgrab(mm);
 127         current->active_mm = mm;
 128
 129         trap_init();
 130         notify_cpu_starting(smp_processor_id());
 131         set_cpu_online(smp_processor_id(), 1);
 132         /*
 133          * Remote TLB flushes are ignored while the CPU is offline, so emit
 134          * a local TLB flush right now just in case.
 135          */
 136         local_flush_tlb_all();
 137         complete(&cpu_running);
 138         /*
 139          * Disable preemption before enabling interrupts, so we don't try to
 140          * schedule a CPU that hasn't actually started yet.
 141          */
 142         preempt_disable();
 143         local_irq_enable();
 144         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 145 }