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/interrupt.h> 29 #include <linux/nodemask.h> 30 #include <linux/export.h> 31 #include <linux/mmzone.h> 32 #include <linux/init.h> 33 #include <linux/smp.h> 34 #include <linux/irq.h> 35 #include <asm/io_apic.h> 36 #include <asm/cpu.h> 37 38 static DEFINE_PER_CPU(struct x86_cpu, cpu_devices); 39 40 #ifdef CONFIG_HOTPLUG_CPU 41 42 #ifdef CONFIG_BOOTPARAM_HOTPLUG_CPU0 43 static int cpu0_hotpluggable = 1; 44 #else 45 static int cpu0_hotpluggable; 46 static int __init enable_cpu0_hotplug(char *str) 47 { 48 cpu0_hotpluggable = 1; 49 return 1; 50 } 51 52 __setup("cpu0_hotplug", enable_cpu0_hotplug); 53 #endif 54 55 #ifdef CONFIG_DEBUG_HOTPLUG_CPU0 56 /* 57 * This function offlines a CPU as early as possible and allows userspace to 58 * boot up without the CPU. The CPU can be onlined back by user after boot. 59 * 60 * This is only called for debugging CPU offline/online feature. 61 */ 62 int _debug_hotplug_cpu(int cpu, int action) 63 { 64 int ret; 65 66 if (!cpu_is_hotpluggable(cpu)) 67 return -EINVAL; 68 69 switch (action) { 70 case 0: 71 ret = remove_cpu(cpu); 72 if (!ret) 73 pr_info("DEBUG_HOTPLUG_CPU0: CPU %u is now offline\n", cpu); 74 else 75 pr_debug("Can't offline CPU%d.\n", cpu); 76 break; 77 case 1: 78 ret = add_cpu(cpu); 79 if (ret) 80 pr_debug("Can't online CPU%d.\n", cpu); 81 82 break; 83 default: 84 ret = -EINVAL; 85 } 86 87 return ret; 88 } 89 90 static int __init debug_hotplug_cpu(void) 91 { 92 _debug_hotplug_cpu(0, 0); 93 return 0; 94 } 95 96 late_initcall_sync(debug_hotplug_cpu); 97 #endif /* CONFIG_DEBUG_HOTPLUG_CPU0 */ 98 99 int arch_register_cpu(int num) 100 { 101 struct cpuinfo_x86 *c = &cpu_data(num); 102 103 /* 104 * Currently CPU0 is only hotpluggable on Intel platforms. Other 105 * vendors can add hotplug support later. 106 * Xen PV guests don't support CPU0 hotplug at all. 107 */ 108 if (c->x86_vendor != X86_VENDOR_INTEL || 109 cpu_feature_enabled(X86_FEATURE_XENPV)) 110 cpu0_hotpluggable = 0; 111 112 /* 113 * Two known BSP/CPU0 dependencies: Resume from suspend/hibernate 114 * depends on BSP. PIC interrupts depend on BSP. 115 * 116 * If the BSP dependencies are under control, one can tell kernel to 117 * enable BSP hotplug. This basically adds a control file and 118 * one can attempt to offline BSP. 119 */ 120 if (num == 0 && cpu0_hotpluggable) { 121 unsigned int irq; 122 /* 123 * We won't take down the boot processor on i386 if some 124 * interrupts only are able to be serviced by the BSP in PIC. 125 */ 126 for_each_active_irq(irq) { 127 if (!IO_APIC_IRQ(irq) && irq_has_action(irq)) { 128 cpu0_hotpluggable = 0; 129 break; 130 } 131 } 132 } 133 if (num || cpu0_hotpluggable) 134 per_cpu(cpu_devices, num).cpu.hotpluggable = 1; 135 136 return register_cpu(&per_cpu(cpu_devices, num).cpu, num); 137 } 138 EXPORT_SYMBOL(arch_register_cpu); 139 140 void arch_unregister_cpu(int num) 141 { 142 unregister_cpu(&per_cpu(cpu_devices, num).cpu); 143 } 144 EXPORT_SYMBOL(arch_unregister_cpu); 145 #else /* CONFIG_HOTPLUG_CPU */ 146 147 static int __init arch_register_cpu(int num) 148 { 149 return register_cpu(&per_cpu(cpu_devices, num).cpu, num); 150 } 151 #endif /* CONFIG_HOTPLUG_CPU */ 152 153 static int __init topology_init(void) 154 { 155 int i; 156 157 for_each_present_cpu(i) 158 arch_register_cpu(i); 159 160 return 0; 161 } 162 subsys_initcall(topology_init); 163