1 /* 2 * Populate sysfs with topology information 3 * 4 * Written by: Matthew Dobson, IBM Corporation 5 * Original Code: Paul Dorwin, IBM Corporation, Patrick Mochel, OSDL 6 * 7 * Copyright (C) 2002, IBM Corp. 8 * 9 * All rights reserved. 10 * 11 * This program is free software; you can redistribute it and/or modify 12 * it under the terms of the GNU General Public License as published by 13 * the Free Software Foundation; either version 2 of the License, or 14 * (at your option) any later version. 15 * 16 * This program is distributed in the hope that it will be useful, but 17 * WITHOUT ANY WARRANTY; without even the implied warranty of 18 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or 19 * NON INFRINGEMENT. See the GNU General Public License for more 20 * details. 21 * 22 * You should have received a copy of the GNU General Public License 23 * along with this program; if not, write to the Free Software 24 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 25 * 26 * Send feedback to <colpatch@us.ibm.com> 27 */ 28 #include <linux/nodemask.h> 29 #include <linux/export.h> 30 #include <linux/mmzone.h> 31 #include <linux/init.h> 32 #include <linux/smp.h> 33 #include <linux/irq.h> 34 #include <asm/io_apic.h> 35 #include <asm/cpu.h> 36 37 static DEFINE_PER_CPU(struct x86_cpu, cpu_devices); 38 39 #ifdef CONFIG_HOTPLUG_CPU 40 41 #ifdef CONFIG_BOOTPARAM_HOTPLUG_CPU0 42 static int cpu0_hotpluggable = 1; 43 #else 44 static int cpu0_hotpluggable; 45 static int __init enable_cpu0_hotplug(char *str) 46 { 47 cpu0_hotpluggable = 1; 48 return 1; 49 } 50 51 __setup("cpu0_hotplug", enable_cpu0_hotplug); 52 #endif 53 54 #ifdef CONFIG_DEBUG_HOTPLUG_CPU0 55 /* 56 * This function offlines a CPU as early as possible and allows userspace to 57 * boot up without the CPU. The CPU can be onlined back by user after boot. 58 * 59 * This is only called for debugging CPU offline/online feature. 60 */ 61 int _debug_hotplug_cpu(int cpu, int action) 62 { 63 int ret; 64 65 if (!cpu_is_hotpluggable(cpu)) 66 return -EINVAL; 67 68 switch (action) { 69 case 0: 70 ret = remove_cpu(cpu); 71 if (!ret) 72 pr_info("DEBUG_HOTPLUG_CPU0: CPU %u is now offline\n", cpu); 73 else 74 pr_debug("Can't offline CPU%d.\n", cpu); 75 break; 76 case 1: 77 ret = add_cpu(cpu); 78 if (ret) 79 pr_debug("Can't online CPU%d.\n", cpu); 80 81 break; 82 default: 83 ret = -EINVAL; 84 } 85 86 return ret; 87 } 88 89 static int __init debug_hotplug_cpu(void) 90 { 91 _debug_hotplug_cpu(0, 0); 92 return 0; 93 } 94 95 late_initcall_sync(debug_hotplug_cpu); 96 #endif /* CONFIG_DEBUG_HOTPLUG_CPU0 */ 97 98 int arch_register_cpu(int num) 99 { 100 struct cpuinfo_x86 *c = &cpu_data(num); 101 102 /* 103 * Currently CPU0 is only hotpluggable on Intel platforms. Other 104 * vendors can add hotplug support later. 105 * Xen PV guests don't support CPU0 hotplug at all. 106 */ 107 if (c->x86_vendor != X86_VENDOR_INTEL || 108 boot_cpu_has(X86_FEATURE_XENPV)) 109 cpu0_hotpluggable = 0; 110 111 /* 112 * Two known BSP/CPU0 dependencies: Resume from suspend/hibernate 113 * depends on BSP. PIC interrupts depend on BSP. 114 * 115 * If the BSP depencies are under control, one can tell kernel to 116 * enable BSP hotplug. This basically adds a control file and 117 * one can attempt to offline BSP. 118 */ 119 if (num == 0 && cpu0_hotpluggable) { 120 unsigned int irq; 121 /* 122 * We won't take down the boot processor on i386 if some 123 * interrupts only are able to be serviced by the BSP in PIC. 124 */ 125 for_each_active_irq(irq) { 126 if (!IO_APIC_IRQ(irq) && irq_has_action(irq)) { 127 cpu0_hotpluggable = 0; 128 break; 129 } 130 } 131 } 132 if (num || cpu0_hotpluggable) 133 per_cpu(cpu_devices, num).cpu.hotpluggable = 1; 134 135 return register_cpu(&per_cpu(cpu_devices, num).cpu, num); 136 } 137 EXPORT_SYMBOL(arch_register_cpu); 138 139 void arch_unregister_cpu(int num) 140 { 141 unregister_cpu(&per_cpu(cpu_devices, num).cpu); 142 } 143 EXPORT_SYMBOL(arch_unregister_cpu); 144 #else /* CONFIG_HOTPLUG_CPU */ 145 146 static int __init arch_register_cpu(int num) 147 { 148 return register_cpu(&per_cpu(cpu_devices, num).cpu, num); 149 } 150 #endif /* CONFIG_HOTPLUG_CPU */ 151 152 static int __init topology_init(void) 153 { 154 int i; 155 156 #ifdef CONFIG_NUMA 157 for_each_online_node(i) 158 register_one_node(i); 159 #endif 160 161 for_each_present_cpu(i) 162 arch_register_cpu(i); 163 164 return 0; 165 } 166 subsys_initcall(topology_init); 167