LXR linux/arch/x86/kernel/topology.c

   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/cpu.h>
  35
  36static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
  37
  38#ifdef CONFIG_HOTPLUG_CPU
  39
  40#ifdef CONFIG_BOOTPARAM_HOTPLUG_CPU0
  41static int cpu0_hotpluggable = 1;
  42#else
  43static int cpu0_hotpluggable;
  44static int __init enable_cpu0_hotplug(char *str)
  45{
  46        cpu0_hotpluggable = 1;
  47        return 1;
  48}
  49
  50__setup("cpu0_hotplug", enable_cpu0_hotplug);
  51#endif
  52
  53#ifdef CONFIG_DEBUG_HOTPLUG_CPU0
  54/*
  55 * This function offlines a CPU as early as possible and allows userspace to
  56 * boot up without the CPU. The CPU can be onlined back by user after boot.
  57 *
  58 * This is only called for debugging CPU offline/online feature.
  59 */
  60int _debug_hotplug_cpu(int cpu, int action)
  61{
  62        struct device *dev = get_cpu_device(cpu);
  63        int ret;
  64
  65        if (!cpu_is_hotpluggable(cpu))
  66                return -EINVAL;
  67
  68        lock_device_hotplug();
  69
  70        switch (action) {
  71        case 0:
  72                ret = cpu_down(cpu);
  73                if (!ret) {
  74                        pr_info("DEBUG_HOTPLUG_CPU0: CPU %u is now offline\n", cpu);
  75                        dev->offline = true;
  76                        kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
  77                } else
  78                        pr_debug("Can't offline CPU%d.\n", cpu);
  79                break;
  80        case 1:
  81                ret = cpu_up(cpu);
  82                if (!ret) {
  83                        dev->offline = false;
  84                        kobject_uevent(&dev->kobj, KOBJ_ONLINE);
  85                } else {
  86                        pr_debug("Can't online CPU%d.\n", cpu);
  87                }
  88                break;
  89        default:
  90                ret = -EINVAL;
  91        }
  92
  93        unlock_device_hotplug();
  94
  95        return ret;
  96}
  97
  98static int __init debug_hotplug_cpu(void)
  99{
 100        _debug_hotplug_cpu(0, 0);
 101        return 0;
 102}
 103
 104late_initcall_sync(debug_hotplug_cpu);
 105#endif /* CONFIG_DEBUG_HOTPLUG_CPU0 */
 106
 107int arch_register_cpu(int num)
 108{
 109        struct cpuinfo_x86 *c = &cpu_data(num);
 110
 111        /*
 112         * Currently CPU0 is only hotpluggable on Intel platforms. Other
 113         * vendors can add hotplug support later.
 114         * Xen PV guests don't support CPU0 hotplug at all.
 115         */
 116        if (c->x86_vendor != X86_VENDOR_INTEL ||
 117            boot_cpu_has(X86_FEATURE_XENPV))
 118                cpu0_hotpluggable = 0;
 119
 120        /*
 121         * Two known BSP/CPU0 dependencies: Resume from suspend/hibernate
 122         * depends on BSP. PIC interrupts depend on BSP.
 123         *
 124         * If the BSP depencies are under control, one can tell kernel to
 125         * enable BSP hotplug. This basically adds a control file and
 126         * one can attempt to offline BSP.
 127         */
 128        if (num == 0 && cpu0_hotpluggable) {
 129                unsigned int irq;
 130                /*
 131                 * We won't take down the boot processor on i386 if some
 132                 * interrupts only are able to be serviced by the BSP in PIC.
 133                 */
 134                for_each_active_irq(irq) {
 135                        if (!IO_APIC_IRQ(irq) && irq_has_action(irq)) {
 136                                cpu0_hotpluggable = 0;
 137                                break;
 138                        }
 139                }
 140        }
 141        if (num || cpu0_hotpluggable)
 142                per_cpu(cpu_devices, num).cpu.hotpluggable = 1;
 143
 144        return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
 145}
 146EXPORT_SYMBOL(arch_register_cpu);
 147
 148void arch_unregister_cpu(int num)
 149{
 150        unregister_cpu(&per_cpu(cpu_devices, num).cpu);
 151}
 152EXPORT_SYMBOL(arch_unregister_cpu);
 153#else /* CONFIG_HOTPLUG_CPU */
 154
 155static int __init arch_register_cpu(int num)
 156{
 157        return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
 158}
 159#endif /* CONFIG_HOTPLUG_CPU */
 160
 161static int __init topology_init(void)
 162{
 163        int i;
 164
 165#ifdef CONFIG_NUMA
 166        for_each_online_node(i)
 167                register_one_node(i);
 168#endif
 169
 170        for_each_present_cpu(i)
 171                arch_register_cpu(i);
 172
 173        return 0;
 174}
 175subsys_initcall(topology_init);
 176