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/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            boot_cpu_has(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#ifdef CONFIG_NUMA
 158        for_each_online_node(i)
 159                register_one_node(i);
 160#endif
 161
 162        for_each_present_cpu(i)
 163                arch_register_cpu(i);
 164
 165        return 0;
 166}
 167subsys_initcall(topology_init);
 168