arch/powerpc/platforms/pseries/hotplug-cpu.c - kernel/msm-4.9 - Gitiles

 /*
  * pseries CPU Hotplug infrastructure.
  *
  * Split out from arch/powerpc/platforms/pseries/setup.c
  *  arch/powerpc/kernel/rtas.c, and arch/powerpc/platforms/pseries/smp.c
  *
  * Peter Bergner, IBM	March 2001.
  * Copyright (C) 2001 IBM.
  * Dave Engebretsen, Peter Bergner, and
  * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
  * Plus various changes from other IBM teams...
  *
  * Copyright (C) 2006 Michael Ellerman, IBM Corporation
  *
  *      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.
  */

 #include <linux/kernel.h>
 #include <linux/interrupt.h>
 #include <linux/delay.h>
 #include <linux/sched.h>	/* for idle_task_exit */
 #include <linux/cpu.h>
 #include <linux/of.h>
 #include <asm/prom.h>
 #include <asm/rtas.h>
 #include <asm/firmware.h>
 #include <asm/machdep.h>
 #include <asm/vdso_datapage.h>
 #include <asm/xics.h>
 #include <asm/plpar_wrappers.h>

 #include "offline_states.h"

 /* This version can't take the spinlock, because it never returns */
 static int rtas_stop_self_token = RTAS_UNKNOWN_SERVICE;

 static DEFINE_PER_CPU(enum cpu_state_vals, preferred_offline_state) =
 							CPU_STATE_OFFLINE;
 static DEFINE_PER_CPU(enum cpu_state_vals, current_state) = CPU_STATE_OFFLINE;

 static enum cpu_state_vals default_offline_state = CPU_STATE_OFFLINE;

 static int cede_offline_enabled __read_mostly = 1;

 /*
  * Enable/disable cede_offline when available.
  */
 static int __init setup_cede_offline(char *str)
 {
 	if (!strcmp(str, "off"))
 		cede_offline_enabled = 0;
 	else if (!strcmp(str, "on"))
 		cede_offline_enabled = 1;
 	else
 		return 0;
 	return 1;
 }

 __setup("cede_offline=", setup_cede_offline);

 enum cpu_state_vals get_cpu_current_state(int cpu)
 {
 	return per_cpu(current_state, cpu);
 }

 void set_cpu_current_state(int cpu, enum cpu_state_vals state)
 {
 	per_cpu(current_state, cpu) = state;
 }

 enum cpu_state_vals get_preferred_offline_state(int cpu)
 {
 	return per_cpu(preferred_offline_state, cpu);
 }

 void set_preferred_offline_state(int cpu, enum cpu_state_vals state)
 {
 	per_cpu(preferred_offline_state, cpu) = state;
 }

 void set_default_offline_state(int cpu)
 {
 	per_cpu(preferred_offline_state, cpu) = default_offline_state;
 }

 static void rtas_stop_self(void)
 {
 	static struct rtas_args args = {
 		.nargs = 0,
 		.nret = cpu_to_be32(1),
 		.rets = &args.args[0],
 	};

 	args.token = cpu_to_be32(rtas_stop_self_token);

 	local_irq_disable();

 	BUG_ON(rtas_stop_self_token == RTAS_UNKNOWN_SERVICE);

 	printk("cpu %u (hwid %u) Ready to die...\n",
 	       smp_processor_id(), hard_smp_processor_id());
 	enter_rtas(__pa(&args));

 	panic("Alas, I survived.\n");
 }

 static void pseries_mach_cpu_die(void)
 {
 	unsigned int cpu = smp_processor_id();
 	unsigned int hwcpu = hard_smp_processor_id();
 	u8 cede_latency_hint = 0;

 	local_irq_disable();
 	idle_task_exit();
 	xics_teardown_cpu();

 	if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
 		set_cpu_current_state(cpu, CPU_STATE_INACTIVE);
 		if (ppc_md.suspend_disable_cpu)
 			ppc_md.suspend_disable_cpu();

 		cede_latency_hint = 2;

 		get_lppaca()->idle = 1;
 		if (!lppaca_shared_proc(get_lppaca()))
 			get_lppaca()->donate_dedicated_cpu = 1;

 		while (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
 			while (!prep_irq_for_idle()) {
 				local_irq_enable();
 				local_irq_disable();
 			}

 			extended_cede_processor(cede_latency_hint);
 		}

 		local_irq_disable();

 		if (!lppaca_shared_proc(get_lppaca()))
 			get_lppaca()->donate_dedicated_cpu = 0;
 		get_lppaca()->idle = 0;

 		if (get_preferred_offline_state(cpu) == CPU_STATE_ONLINE) {
 			unregister_slb_shadow(hwcpu);

 			hard_irq_disable();
 			/*
 			 * Call to start_secondary_resume() will not return.
 			 * Kernel stack will be reset and start_secondary()
 			 * will be called to continue the online operation.
 			 */
 			start_secondary_resume();
 		}
 	}

 	/* Requested state is CPU_STATE_OFFLINE at this point */
 	WARN_ON(get_preferred_offline_state(cpu) != CPU_STATE_OFFLINE);

 	set_cpu_current_state(cpu, CPU_STATE_OFFLINE);
 	unregister_slb_shadow(hwcpu);
 	rtas_stop_self();

 	/* Should never get here... */
 	BUG();
 	for(;;);
 }

 static int pseries_cpu_disable(void)
 {
 	int cpu = smp_processor_id();

 	set_cpu_online(cpu, false);
 	vdso_data->processorCount--;

 	/*fix boot_cpuid here*/
 	if (cpu == boot_cpuid)
 		boot_cpuid = cpumask_any(cpu_online_mask);

 	/* FIXME: abstract this to not be platform specific later on */
 	xics_migrate_irqs_away();
 	return 0;
 }

 /*
  * pseries_cpu_die: Wait for the cpu to die.
  * @cpu: logical processor id of the CPU whose death we're awaiting.
  *
  * This function is called from the context of the thread which is performing
  * the cpu-offline. Here we wait for long enough to allow the cpu in question
  * to self-destroy so that the cpu-offline thread can send the CPU_DEAD
  * notifications.
  *
  * OTOH, pseries_mach_cpu_die() is called by the @cpu when it wants to
  * self-destruct.
  */
 static void pseries_cpu_die(unsigned int cpu)
 {
 	int tries;
 	int cpu_status = 1;
 	unsigned int pcpu = get_hard_smp_processor_id(cpu);

 	if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
 		cpu_status = 1;
 		for (tries = 0; tries < 5000; tries++) {
 			if (get_cpu_current_state(cpu) == CPU_STATE_INACTIVE) {
 				cpu_status = 0;
 				break;
 			}
 			msleep(1);
 		}
 	} else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {

 		for (tries = 0; tries < 25; tries++) {
 			cpu_status = smp_query_cpu_stopped(pcpu);
 			if (cpu_status == QCSS_STOPPED ||
 			    cpu_status == QCSS_HARDWARE_ERROR)
 				break;
 			cpu_relax();
 		}
 	}

 	if (cpu_status != 0) {
 		printk("Querying DEAD? cpu %i (%i) shows %i\n",
 		       cpu, pcpu, cpu_status);
 	}

 	/* Isolation and deallocation are definitely done by
 	 * drslot_chrp_cpu.  If they were not they would be
 	 * done here.  Change isolate state to Isolate and
 	 * change allocation-state to Unusable.
 	 */
 	paca[cpu].cpu_start = 0;
 }

 /*
  * Update cpu_present_mask and paca(s) for a new cpu node.  The wrinkle
  * here is that a cpu device node may represent up to two logical cpus
  * in the SMT case.  We must honor the assumption in other code that
  * the logical ids for sibling SMT threads x and y are adjacent, such
  * that x^1 == y and y^1 == x.
  */
 static int pseries_add_processor(struct device_node *np)
 {
 	unsigned int cpu;
 	cpumask_var_t candidate_mask, tmp;
 	int err = -ENOSPC, len, nthreads, i;
 	const __be32 *intserv;

 	intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
 	if (!intserv)
 		return 0;

 	zalloc_cpumask_var(&candidate_mask, GFP_KERNEL);
 	zalloc_cpumask_var(&tmp, GFP_KERNEL);

 	nthreads = len / sizeof(u32);
 	for (i = 0; i < nthreads; i++)
 		cpumask_set_cpu(i, tmp);

 	cpu_maps_update_begin();

 	BUG_ON(!cpumask_subset(cpu_present_mask, cpu_possible_mask));

 	/* Get a bitmap of unoccupied slots. */
 	cpumask_xor(candidate_mask, cpu_possible_mask, cpu_present_mask);
 	if (cpumask_empty(candidate_mask)) {
 		/* If we get here, it most likely means that NR_CPUS is
 		 * less than the partition's max processors setting.
 		 */
 		printk(KERN_ERR "Cannot add cpu %s; this system configuration"
 		       " supports %d logical cpus.\n", np->full_name,
 		       cpumask_weight(cpu_possible_mask));
 		goto out_unlock;
 	}

 	while (!cpumask_empty(tmp))
 		if (cpumask_subset(tmp, candidate_mask))
 			/* Found a range where we can insert the new cpu(s) */
 			break;
 		else
 			cpumask_shift_left(tmp, tmp, nthreads);

 	if (cpumask_empty(tmp)) {
 		printk(KERN_ERR "Unable to find space in cpu_present_mask for"
 		       " processor %s with %d thread(s)\n", np->name,
 		       nthreads);
 		goto out_unlock;
 	}

 	for_each_cpu(cpu, tmp) {
 		BUG_ON(cpu_present(cpu));
 		set_cpu_present(cpu, true);
 		set_hard_smp_processor_id(cpu, be32_to_cpu(*intserv++));
 	}
 	err = 0;
 out_unlock:
 	cpu_maps_update_done();
 	free_cpumask_var(candidate_mask);
 	free_cpumask_var(tmp);
 	return err;
 }

 /*
  * Update the present map for a cpu node which is going away, and set
  * the hard id in the paca(s) to -1 to be consistent with boot time
  * convention for non-present cpus.
  */
 static void pseries_remove_processor(struct device_node *np)
 {
 	unsigned int cpu;
 	int len, nthreads, i;
 	const __be32 *intserv;
 	u32 thread;

 	intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
 	if (!intserv)
 		return;

 	nthreads = len / sizeof(u32);

 	cpu_maps_update_begin();
 	for (i = 0; i < nthreads; i++) {
 		thread = be32_to_cpu(intserv[i]);
 		for_each_present_cpu(cpu) {
 			if (get_hard_smp_processor_id(cpu) != thread)
 				continue;
 			BUG_ON(cpu_online(cpu));
 			set_cpu_present(cpu, false);
 			set_hard_smp_processor_id(cpu, -1);
 			break;
 		}
 		if (cpu >= nr_cpu_ids)
 			printk(KERN_WARNING "Could not find cpu to remove "
 			       "with physical id 0x%x\n", thread);
 	}
 	cpu_maps_update_done();
 }

 static int pseries_smp_notifier(struct notifier_block *nb,
 				unsigned long action, void *node)
 {
 	int err = 0;

 	switch (action) {
 	case OF_RECONFIG_ATTACH_NODE:
 		err = pseries_add_processor(node);
 		break;
 	case OF_RECONFIG_DETACH_NODE:
 		pseries_remove_processor(node);
 		break;
 	}
 	return notifier_from_errno(err);
 }

 static struct notifier_block pseries_smp_nb = {
 	.notifier_call = pseries_smp_notifier,
 };

 #define MAX_CEDE_LATENCY_LEVELS		4
 #define	CEDE_LATENCY_PARAM_LENGTH	10
 #define CEDE_LATENCY_PARAM_MAX_LENGTH	\
 	(MAX_CEDE_LATENCY_LEVELS * CEDE_LATENCY_PARAM_LENGTH * sizeof(char))
 #define CEDE_LATENCY_TOKEN		45

 static char cede_parameters[CEDE_LATENCY_PARAM_MAX_LENGTH];

 static int parse_cede_parameters(void)
 {
 	memset(cede_parameters, 0, CEDE_LATENCY_PARAM_MAX_LENGTH);
 	return rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
 			 NULL,
 			 CEDE_LATENCY_TOKEN,
 			 __pa(cede_parameters),
 			 CEDE_LATENCY_PARAM_MAX_LENGTH);
 }

 static int __init pseries_cpu_hotplug_init(void)
 {
 	struct device_node *np;
 	const char *typep;
 	int cpu;
 	int qcss_tok;

 	for_each_node_by_name(np, "interrupt-controller") {
 		typep = of_get_property(np, "compatible", NULL);
 		if (strstr(typep, "open-pic")) {
 			of_node_put(np);

 			printk(KERN_INFO "CPU Hotplug not supported on "
 				"systems using MPIC\n");
 			return 0;
 		}
 	}

 	rtas_stop_self_token = rtas_token("stop-self");
 	qcss_tok = rtas_token("query-cpu-stopped-state");

 	if (rtas_stop_self_token == RTAS_UNKNOWN_SERVICE ||
 			qcss_tok == RTAS_UNKNOWN_SERVICE) {
 		printk(KERN_INFO "CPU Hotplug not supported by firmware "
 				"- disabling.\n");
 		return 0;
 	}

 	ppc_md.cpu_die = pseries_mach_cpu_die;
 	smp_ops->cpu_disable = pseries_cpu_disable;
 	smp_ops->cpu_die = pseries_cpu_die;

 	/* Processors can be added/removed only on LPAR */
 	if (firmware_has_feature(FW_FEATURE_LPAR)) {
 		of_reconfig_notifier_register(&pseries_smp_nb);
 		cpu_maps_update_begin();
 		if (cede_offline_enabled && parse_cede_parameters() == 0) {
 			default_offline_state = CPU_STATE_INACTIVE;
 			for_each_online_cpu(cpu)
 				set_default_offline_state(cpu);
 		}
 		cpu_maps_update_done();
 	}

 	return 0;
 }
 machine_arch_initcall(pseries, pseries_cpu_hotplug_init);
	/*
	* pseries CPU Hotplug infrastructure.
	*
	* Split out from arch/powerpc/platforms/pseries/setup.c
	* arch/powerpc/kernel/rtas.c, and arch/powerpc/platforms/pseries/smp.c
	*
	* Peter Bergner, IBM March 2001.
	* Copyright (C) 2001 IBM.
	* Dave Engebretsen, Peter Bergner, and
	* Mike Corrigan {engebret\|bergner\|mikec}@us.ibm.com
	* Plus various changes from other IBM teams...
	*
	* Copyright (C) 2006 Michael Ellerman, IBM Corporation
	*
	* 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.
	*/

	#include <linux/kernel.h>
	#include <linux/interrupt.h>
	#include <linux/delay.h>
	#include <linux/sched.h> /* for idle_task_exit */
	#include <linux/cpu.h>
	#include <linux/of.h>
	#include <asm/prom.h>
	#include <asm/rtas.h>
	#include <asm/firmware.h>
	#include <asm/machdep.h>
	#include <asm/vdso_datapage.h>
	#include <asm/xics.h>
	#include <asm/plpar_wrappers.h>

	#include "offline_states.h"

	/* This version can't take the spinlock, because it never returns */
	static int rtas_stop_self_token = RTAS_UNKNOWN_SERVICE;

	static DEFINE_PER_CPU(enum cpu_state_vals, preferred_offline_state) =
	CPU_STATE_OFFLINE;
	static DEFINE_PER_CPU(enum cpu_state_vals, current_state) = CPU_STATE_OFFLINE;

	static enum cpu_state_vals default_offline_state = CPU_STATE_OFFLINE;

	static int cede_offline_enabled __read_mostly = 1;

	/*
	* Enable/disable cede_offline when available.
	*/
	static int __init setup_cede_offline(char *str)
	{
	if (!strcmp(str, "off"))
	cede_offline_enabled = 0;
	else if (!strcmp(str, "on"))
	cede_offline_enabled = 1;
	else
	return 0;
	return 1;
	}

	__setup("cede_offline=", setup_cede_offline);

	enum cpu_state_vals get_cpu_current_state(int cpu)
	{
	return per_cpu(current_state, cpu);
	}

	void set_cpu_current_state(int cpu, enum cpu_state_vals state)
	{
	per_cpu(current_state, cpu) = state;
	}

	enum cpu_state_vals get_preferred_offline_state(int cpu)
	{
	return per_cpu(preferred_offline_state, cpu);
	}

	void set_preferred_offline_state(int cpu, enum cpu_state_vals state)
	{
	per_cpu(preferred_offline_state, cpu) = state;
	}

	void set_default_offline_state(int cpu)
	{
	per_cpu(preferred_offline_state, cpu) = default_offline_state;
	}

	static void rtas_stop_self(void)
	{
	static struct rtas_args args = {
	.nargs = 0,
	.nret = cpu_to_be32(1),
	.rets = &args.args[0],
	};

	args.token = cpu_to_be32(rtas_stop_self_token);

	local_irq_disable();

	BUG_ON(rtas_stop_self_token == RTAS_UNKNOWN_SERVICE);

	printk("cpu %u (hwid %u) Ready to die...\n",
	smp_processor_id(), hard_smp_processor_id());
	enter_rtas(__pa(&args));

	panic("Alas, I survived.\n");
	}

	static void pseries_mach_cpu_die(void)
	{
	unsigned int cpu = smp_processor_id();
	unsigned int hwcpu = hard_smp_processor_id();
	u8 cede_latency_hint = 0;

	local_irq_disable();
	idle_task_exit();
	xics_teardown_cpu();

	if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
	set_cpu_current_state(cpu, CPU_STATE_INACTIVE);
	if (ppc_md.suspend_disable_cpu)
	ppc_md.suspend_disable_cpu();

	cede_latency_hint = 2;

	get_lppaca()->idle = 1;
	if (!lppaca_shared_proc(get_lppaca()))
	get_lppaca()->donate_dedicated_cpu = 1;

	while (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
	while (!prep_irq_for_idle()) {
	local_irq_enable();
	local_irq_disable();
	}

	extended_cede_processor(cede_latency_hint);
	}

	local_irq_disable();

	if (!lppaca_shared_proc(get_lppaca()))
	get_lppaca()->donate_dedicated_cpu = 0;
	get_lppaca()->idle = 0;

	if (get_preferred_offline_state(cpu) == CPU_STATE_ONLINE) {
	unregister_slb_shadow(hwcpu);

	hard_irq_disable();
	/*
	* Call to start_secondary_resume() will not return.
	* Kernel stack will be reset and start_secondary()
	* will be called to continue the online operation.
	*/
	start_secondary_resume();
	}
	}

	/* Requested state is CPU_STATE_OFFLINE at this point */
	WARN_ON(get_preferred_offline_state(cpu) != CPU_STATE_OFFLINE);

	set_cpu_current_state(cpu, CPU_STATE_OFFLINE);
	unregister_slb_shadow(hwcpu);
	rtas_stop_self();

	/* Should never get here... */
	BUG();
	for(;;);
	}

	static int pseries_cpu_disable(void)
	{
	int cpu = smp_processor_id();

	set_cpu_online(cpu, false);
	vdso_data->processorCount--;

	/fix boot_cpuid here/
	if (cpu == boot_cpuid)
	boot_cpuid = cpumask_any(cpu_online_mask);

	/* FIXME: abstract this to not be platform specific later on */
	xics_migrate_irqs_away();
	return 0;
	}

	/*
	* pseries_cpu_die: Wait for the cpu to die.
	* @cpu: logical processor id of the CPU whose death we're awaiting.
	*
	* This function is called from the context of the thread which is performing
	* the cpu-offline. Here we wait for long enough to allow the cpu in question
	* to self-destroy so that the cpu-offline thread can send the CPU_DEAD
	* notifications.
	*
	* OTOH, pseries_mach_cpu_die() is called by the @cpu when it wants to
	* self-destruct.
	*/
	static void pseries_cpu_die(unsigned int cpu)
	{
	int tries;
	int cpu_status = 1;
	unsigned int pcpu = get_hard_smp_processor_id(cpu);

	if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
	cpu_status = 1;
	for (tries = 0; tries < 5000; tries++) {
	if (get_cpu_current_state(cpu) == CPU_STATE_INACTIVE) {
	cpu_status = 0;
	break;
	}
	msleep(1);
	}
	} else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {

	for (tries = 0; tries < 25; tries++) {
	cpu_status = smp_query_cpu_stopped(pcpu);
	if (cpu_status == QCSS_STOPPED \|\|
	cpu_status == QCSS_HARDWARE_ERROR)
	break;
	cpu_relax();
	}
	}

	if (cpu_status != 0) {
	printk("Querying DEAD? cpu %i (%i) shows %i\n",
	cpu, pcpu, cpu_status);
	}

	/* Isolation and deallocation are definitely done by
	* drslot_chrp_cpu. If they were not they would be
	* done here. Change isolate state to Isolate and
	* change allocation-state to Unusable.
	*/
	paca[cpu].cpu_start = 0;
	}

	/*
	* Update cpu_present_mask and paca(s) for a new cpu node. The wrinkle
	* here is that a cpu device node may represent up to two logical cpus
	* in the SMT case. We must honor the assumption in other code that
	* the logical ids for sibling SMT threads x and y are adjacent, such
	* that x^1 == y and y^1 == x.
	*/
	static int pseries_add_processor(struct device_node *np)
	{
	unsigned int cpu;
	cpumask_var_t candidate_mask, tmp;
	int err = -ENOSPC, len, nthreads, i;
	const __be32 *intserv;

	intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
	if (!intserv)
	return 0;

	zalloc_cpumask_var(&candidate_mask, GFP_KERNEL);
	zalloc_cpumask_var(&tmp, GFP_KERNEL);

	nthreads = len / sizeof(u32);
	for (i = 0; i < nthreads; i++)
	cpumask_set_cpu(i, tmp);

	cpu_maps_update_begin();

	BUG_ON(!cpumask_subset(cpu_present_mask, cpu_possible_mask));

	/* Get a bitmap of unoccupied slots. */
	cpumask_xor(candidate_mask, cpu_possible_mask, cpu_present_mask);
	if (cpumask_empty(candidate_mask)) {
	/* If we get here, it most likely means that NR_CPUS is
	* less than the partition's max processors setting.
	*/
	printk(KERN_ERR "Cannot add cpu %s; this system configuration"
	" supports %d logical cpus.\n", np->full_name,
	cpumask_weight(cpu_possible_mask));
	goto out_unlock;
	}

	while (!cpumask_empty(tmp))
	if (cpumask_subset(tmp, candidate_mask))
	/* Found a range where we can insert the new cpu(s) */
	break;
	else
	cpumask_shift_left(tmp, tmp, nthreads);

	if (cpumask_empty(tmp)) {
	printk(KERN_ERR "Unable to find space in cpu_present_mask for"
	" processor %s with %d thread(s)\n", np->name,
	nthreads);
	goto out_unlock;
	}

	for_each_cpu(cpu, tmp) {
	BUG_ON(cpu_present(cpu));
	set_cpu_present(cpu, true);
	set_hard_smp_processor_id(cpu, be32_to_cpu(*intserv++));
	}
	err = 0;
	out_unlock:
	cpu_maps_update_done();
	free_cpumask_var(candidate_mask);
	free_cpumask_var(tmp);
	return err;
	}

	/*
	* Update the present map for a cpu node which is going away, and set
	* the hard id in the paca(s) to -1 to be consistent with boot time
	* convention for non-present cpus.
	*/
	static void pseries_remove_processor(struct device_node *np)
	{
	unsigned int cpu;
	int len, nthreads, i;
	const __be32 *intserv;
	u32 thread;

	intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
	if (!intserv)
	return;

	nthreads = len / sizeof(u32);

	cpu_maps_update_begin();
	for (i = 0; i < nthreads; i++) {
	thread = be32_to_cpu(intserv[i]);
	for_each_present_cpu(cpu) {
	if (get_hard_smp_processor_id(cpu) != thread)
	continue;
	BUG_ON(cpu_online(cpu));
	set_cpu_present(cpu, false);
	set_hard_smp_processor_id(cpu, -1);
	break;
	}
	if (cpu >= nr_cpu_ids)
	printk(KERN_WARNING "Could not find cpu to remove "
	"with physical id 0x%x\n", thread);
	}
	cpu_maps_update_done();
	}

	static int pseries_smp_notifier(struct notifier_block *nb,
	unsigned long action, void *node)
	{
	int err = 0;

	switch (action) {
	case OF_RECONFIG_ATTACH_NODE:
	err = pseries_add_processor(node);
	break;
	case OF_RECONFIG_DETACH_NODE:
	pseries_remove_processor(node);
	break;
	}
	return notifier_from_errno(err);
	}

	static struct notifier_block pseries_smp_nb = {
	.notifier_call = pseries_smp_notifier,
	};

	#define MAX_CEDE_LATENCY_LEVELS 4
	#define CEDE_LATENCY_PARAM_LENGTH 10
	#define CEDE_LATENCY_PARAM_MAX_LENGTH \
	(MAX_CEDE_LATENCY_LEVELS * CEDE_LATENCY_PARAM_LENGTH * sizeof(char))
	#define CEDE_LATENCY_TOKEN 45

	static char cede_parameters[CEDE_LATENCY_PARAM_MAX_LENGTH];

	static int parse_cede_parameters(void)
	{
	memset(cede_parameters, 0, CEDE_LATENCY_PARAM_MAX_LENGTH);
	return rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
	NULL,
	CEDE_LATENCY_TOKEN,
	__pa(cede_parameters),
	CEDE_LATENCY_PARAM_MAX_LENGTH);
	}

	static int __init pseries_cpu_hotplug_init(void)
	{
	struct device_node *np;
	const char *typep;
	int cpu;
	int qcss_tok;

	for_each_node_by_name(np, "interrupt-controller") {
	typep = of_get_property(np, "compatible", NULL);
	if (strstr(typep, "open-pic")) {
	of_node_put(np);

	printk(KERN_INFO "CPU Hotplug not supported on "
	"systems using MPIC\n");
	return 0;
	}
	}

	rtas_stop_self_token = rtas_token("stop-self");
	qcss_tok = rtas_token("query-cpu-stopped-state");

	if (rtas_stop_self_token == RTAS_UNKNOWN_SERVICE \|\|
	qcss_tok == RTAS_UNKNOWN_SERVICE) {
	printk(KERN_INFO "CPU Hotplug not supported by firmware "
	"- disabling.\n");
	return 0;
	}

	ppc_md.cpu_die = pseries_mach_cpu_die;
	smp_ops->cpu_disable = pseries_cpu_disable;
	smp_ops->cpu_die = pseries_cpu_die;

	/* Processors can be added/removed only on LPAR */
	if (firmware_has_feature(FW_FEATURE_LPAR)) {
	of_reconfig_notifier_register(&pseries_smp_nb);
	cpu_maps_update_begin();
	if (cede_offline_enabled && parse_cede_parameters() == 0) {
	default_offline_state = CPU_STATE_INACTIVE;
	for_each_online_cpu(cpu)
	set_default_offline_state(cpu);
	}
	cpu_maps_update_done();
	}

	return 0;
	}
	machine_arch_initcall(pseries, pseries_cpu_hotplug_init);