2 * Populate sysfs with topology information
4 * Written by: Matthew Dobson, IBM Corporation
5 * Original Code: Paul Dorwin, IBM Corporation, Patrick Mochel, OSDL
7 * Copyright (C) 2002, IBM Corp.
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.
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
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.
26 * Send feedback to <colpatch@us.ibm.com>
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>
37 static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
39 #ifdef CONFIG_HOTPLUG_CPU
41 #ifdef CONFIG_BOOTPARAM_HOTPLUG_CPU0
42 static int cpu0_hotpluggable = 1;
44 static int cpu0_hotpluggable;
45 static int __init enable_cpu0_hotplug(char *str)
47 cpu0_hotpluggable = 1;
51 __setup("cpu0_hotplug", enable_cpu0_hotplug);
54 #ifdef CONFIG_DEBUG_HOTPLUG_CPU0
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.
59 * This is only called for debugging CPU offline/online feature.
61 int _debug_hotplug_cpu(int cpu, int action)
65 if (!cpu_is_hotpluggable(cpu))
70 ret = remove_cpu(cpu);
72 pr_info("DEBUG_HOTPLUG_CPU0: CPU %u is now offline\n", cpu);
74 pr_debug("Can't offline CPU%d.\n", cpu);
79 pr_debug("Can't online CPU%d.\n", cpu);
89 static int __init debug_hotplug_cpu(void)
91 _debug_hotplug_cpu(0, 0);
95 late_initcall_sync(debug_hotplug_cpu);
96 #endif /* CONFIG_DEBUG_HOTPLUG_CPU0 */
98 int arch_register_cpu(int num)
100 struct cpuinfo_x86 *c = &cpu_data(num);
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.
107 if (c->x86_vendor != X86_VENDOR_INTEL ||
108 boot_cpu_has(X86_FEATURE_XENPV))
109 cpu0_hotpluggable = 0;
112 * Two known BSP/CPU0 dependencies: Resume from suspend/hibernate
113 * depends on BSP. PIC interrupts depend on BSP.
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.
119 if (num == 0 && cpu0_hotpluggable) {
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.
125 for_each_active_irq(irq) {
126 if (!IO_APIC_IRQ(irq) && irq_has_action(irq)) {
127 cpu0_hotpluggable = 0;
132 if (num || cpu0_hotpluggable)
133 per_cpu(cpu_devices, num).cpu.hotpluggable = 1;
135 return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
137 EXPORT_SYMBOL(arch_register_cpu);
139 void arch_unregister_cpu(int num)
141 unregister_cpu(&per_cpu(cpu_devices, num).cpu);
143 EXPORT_SYMBOL(arch_unregister_cpu);
144 #else /* CONFIG_HOTPLUG_CPU */
146 static int __init arch_register_cpu(int num)
148 return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
150 #endif /* CONFIG_HOTPLUG_CPU */
152 static int __init topology_init(void)
157 for_each_online_node(i)
158 register_one_node(i);
161 for_each_present_cpu(i)
162 arch_register_cpu(i);
166 subsys_initcall(topology_init);