v4.19.13 snapshot.
diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
new file mode 100644
index 0000000..738bf42
--- /dev/null
+++ b/arch/x86/kernel/topology.c
@@ -0,0 +1,175 @@
+/*
+ * Populate sysfs with topology information
+ *
+ * Written by: Matthew Dobson, IBM Corporation
+ * Original Code: Paul Dorwin, IBM Corporation, Patrick Mochel, OSDL
+ *
+ * Copyright (C) 2002, IBM Corp.
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * Send feedback to <colpatch@us.ibm.com>
+ */
+#include <linux/nodemask.h>
+#include <linux/export.h>
+#include <linux/mmzone.h>
+#include <linux/init.h>
+#include <linux/smp.h>
+#include <linux/irq.h>
+#include <asm/cpu.h>
+
+static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+#ifdef CONFIG_BOOTPARAM_HOTPLUG_CPU0
+static int cpu0_hotpluggable = 1;
+#else
+static int cpu0_hotpluggable;
+static int __init enable_cpu0_hotplug(char *str)
+{
+ cpu0_hotpluggable = 1;
+ return 1;
+}
+
+__setup("cpu0_hotplug", enable_cpu0_hotplug);
+#endif
+
+#ifdef CONFIG_DEBUG_HOTPLUG_CPU0
+/*
+ * This function offlines a CPU as early as possible and allows userspace to
+ * boot up without the CPU. The CPU can be onlined back by user after boot.
+ *
+ * This is only called for debugging CPU offline/online feature.
+ */
+int _debug_hotplug_cpu(int cpu, int action)
+{
+ struct device *dev = get_cpu_device(cpu);
+ int ret;
+
+ if (!cpu_is_hotpluggable(cpu))
+ return -EINVAL;
+
+ lock_device_hotplug();
+
+ switch (action) {
+ case 0:
+ ret = cpu_down(cpu);
+ if (!ret) {
+ pr_info("CPU %u is now offline\n", cpu);
+ dev->offline = true;
+ kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
+ } else
+ pr_debug("Can't offline CPU%d.\n", cpu);
+ break;
+ case 1:
+ ret = cpu_up(cpu);
+ if (!ret) {
+ dev->offline = false;
+ kobject_uevent(&dev->kobj, KOBJ_ONLINE);
+ } else {
+ pr_debug("Can't online CPU%d.\n", cpu);
+ }
+ break;
+ default:
+ ret = -EINVAL;
+ }
+
+ unlock_device_hotplug();
+
+ return ret;
+}
+
+static int __init debug_hotplug_cpu(void)
+{
+ _debug_hotplug_cpu(0, 0);
+ return 0;
+}
+
+late_initcall_sync(debug_hotplug_cpu);
+#endif /* CONFIG_DEBUG_HOTPLUG_CPU0 */
+
+int arch_register_cpu(int num)
+{
+ struct cpuinfo_x86 *c = &cpu_data(num);
+
+ /*
+ * Currently CPU0 is only hotpluggable on Intel platforms. Other
+ * vendors can add hotplug support later.
+ * Xen PV guests don't support CPU0 hotplug at all.
+ */
+ if (c->x86_vendor != X86_VENDOR_INTEL ||
+ boot_cpu_has(X86_FEATURE_XENPV))
+ cpu0_hotpluggable = 0;
+
+ /*
+ * Two known BSP/CPU0 dependencies: Resume from suspend/hibernate
+ * depends on BSP. PIC interrupts depend on BSP.
+ *
+ * If the BSP depencies are under control, one can tell kernel to
+ * enable BSP hotplug. This basically adds a control file and
+ * one can attempt to offline BSP.
+ */
+ if (num == 0 && cpu0_hotpluggable) {
+ unsigned int irq;
+ /*
+ * We won't take down the boot processor on i386 if some
+ * interrupts only are able to be serviced by the BSP in PIC.
+ */
+ for_each_active_irq(irq) {
+ if (!IO_APIC_IRQ(irq) && irq_has_action(irq)) {
+ cpu0_hotpluggable = 0;
+ break;
+ }
+ }
+ }
+ if (num || cpu0_hotpluggable)
+ per_cpu(cpu_devices, num).cpu.hotpluggable = 1;
+
+ return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
+}
+EXPORT_SYMBOL(arch_register_cpu);
+
+void arch_unregister_cpu(int num)
+{
+ unregister_cpu(&per_cpu(cpu_devices, num).cpu);
+}
+EXPORT_SYMBOL(arch_unregister_cpu);
+#else /* CONFIG_HOTPLUG_CPU */
+
+static int __init arch_register_cpu(int num)
+{
+ return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
+static int __init topology_init(void)
+{
+ int i;
+
+#ifdef CONFIG_NUMA
+ for_each_online_node(i)
+ register_one_node(i);
+#endif
+
+ for_each_present_cpu(i)
+ arch_register_cpu(i);
+
+ return 0;
+}
+subsys_initcall(topology_init);