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 40 void __init smp_prepare_boot_cpu(void) 41 { 42 init_cpu_topology(); 43 } 44 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 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 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 } 128 129 void __init smp_cpus_done(unsigned int max_cpus) 130 { 131 } 132 133 /* 134 * C entry point for a secondary processor. 135 */ 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