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
  36 static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
  37
  38 #ifdef CONFIG_HOTPLUG_CPU
  39
  40 #ifdef CONFIG_BOOTPARAM_HOTPLUG_CPU0
  41 static int cpu0_hotpluggable = 1;
  42 #else
  43 static int cpu0_hotpluggable;
  44 static 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  */
  60 int _debug_hotplug_cpu(int cpu, int action)
  61 {
  62         int ret;
  63
  64         if (!cpu_is_hotpluggable(cpu))
  65                 return -EINVAL;
  66
  67         switch (action) {
  68         case 0:
  69                 ret = remove_cpu(cpu);
  70                 if (!ret)
  71                         pr_info("DEBUG_HOTPLUG_CPU0: CPU %u is now offline\n", cpu);
  72                 else
  73                         pr_debug("Can't offline CPU%d.\n", cpu);
  74                 break;
  75         case 1:
  76                 ret = add_cpu(cpu);
  77                 if (ret)
  78                         pr_debug("Can't online CPU%d.\n", cpu);
  79
  80                 break;
  81         default:
  82                 ret = -EINVAL;
  83         }
  84
  85         return ret;
  86 }
  87
  88 static int __init debug_hotplug_cpu(void)
  89 {
  90         _debug_hotplug_cpu(0, 0);
  91         return 0;
  92 }
  93
  94 late_initcall_sync(debug_hotplug_cpu);
  95 #endif /* CONFIG_DEBUG_HOTPLUG_CPU0 */
  96
  97 int arch_register_cpu(int num)
  98 {
  99         struct cpuinfo_x86 *c = &cpu_data(num);
 100
 101         /*
 102          * Currently CPU0 is only hotpluggable on Intel platforms. Other
 103          * vendors can add hotplug support later.
 104          * Xen PV guests don't support CPU0 hotplug at all.
 105          */
 106         if (c->x86_vendor != X86_VENDOR_INTEL ||
 107             boot_cpu_has(X86_FEATURE_XENPV))
 108                 cpu0_hotpluggable = 0;
 109
 110         /*
 111          * Two known BSP/CPU0 dependencies: Resume from suspend/hibernate
 112          * depends on BSP. PIC interrupts depend on BSP.
 113          *
 114          * If the BSP depencies are under control, one can tell kernel to
 115          * enable BSP hotplug. This basically adds a control file and
 116          * one can attempt to offline BSP.
 117          */
 118         if (num == 0 && cpu0_hotpluggable) {
 119                 unsigned int irq;
 120                 /*
 121                  * We won't take down the boot processor on i386 if some
 122                  * interrupts only are able to be serviced by the BSP in PIC.
 123                  */
 124                 for_each_active_irq(irq) {
 125                         if (!IO_APIC_IRQ(irq) && irq_has_action(irq)) {
 126                                 cpu0_hotpluggable = 0;
 127                                 break;
 128                         }
 129                 }
 130         }
 131         if (num || cpu0_hotpluggable)
 132                 per_cpu(cpu_devices, num).cpu.hotpluggable = 1;
 133
 134         return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
 135 }
 136 EXPORT_SYMBOL(arch_register_cpu);
 137
 138 void arch_unregister_cpu(int num)
 139 {
 140         unregister_cpu(&per_cpu(cpu_devices, num).cpu);
 141 }
 142 EXPORT_SYMBOL(arch_unregister_cpu);
 143 #else /* CONFIG_HOTPLUG_CPU */
 144
 145 static int __init arch_register_cpu(int num)
 146 {
 147         return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
 148 }
 149 #endif /* CONFIG_HOTPLUG_CPU */
 150
 151 static int __init topology_init(void)
 152 {
 153         int i;
 154
 155 #ifdef CONFIG_NUMA
 156         for_each_online_node(i)
 157                 register_one_node(i);
 158 #endif
 159
 160         for_each_present_cpu(i)
 161                 arch_register_cpu(i);
 162
 163         return 0;
 164 }
 165 subsys_initcall(topology_init);