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
 38static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
 39
 40#ifdef CONFIG_HOTPLUG_CPU
 41
 42#ifdef CONFIG_BOOTPARAM_HOTPLUG_CPU0
 43static int cpu0_hotpluggable = 1;
 44#else
 45static int cpu0_hotpluggable;
 46static 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 */
 62int _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
 90static int __init debug_hotplug_cpu(void)
 91{
 92	_debug_hotplug_cpu(0, 0);
 93	return 0;
 94}
 95
 96late_initcall_sync(debug_hotplug_cpu);
 97#endif /* CONFIG_DEBUG_HOTPLUG_CPU0 */
 98
 99int 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}
138EXPORT_SYMBOL(arch_register_cpu);
139
140void arch_unregister_cpu(int num)
141{
142	unregister_cpu(&per_cpu(cpu_devices, num).cpu);
143}
144EXPORT_SYMBOL(arch_unregister_cpu);
145#else /* CONFIG_HOTPLUG_CPU */
146
147static 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
153static 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}
162subsys_initcall(topology_init);