Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2409 insertions, 0 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
new file mode 100644
index 000000000..c9ca190ec
--- /dev/null
+++ b/kernel/cpu.c
@@ -0,0 +1,2409 @@
+/* CPU control.
+ * (C) 2001, 2002, 2003, 2004 Rusty Russell
+ *
+ * This code is licenced under the GPL.
+ */
+#include <linux/sched/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/smp.h>
+#include <linux/init.h>
+#include <linux/notifier.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/hotplug.h>
+#include <linux/sched/task.h>
+#include <linux/sched/smt.h>
+#include <linux/unistd.h>
+#include <linux/cpu.h>
+#include <linux/oom.h>
+#include <linux/rcupdate.h>
+#include <linux/export.h>
+#include <linux/bug.h>
+#include <linux/kthread.h>
+#include <linux/stop_machine.h>
+#include <linux/mutex.h>
+#include <linux/gfp.h>
+#include <linux/suspend.h>
+#include <linux/lockdep.h>
+#include <linux/tick.h>
+#include <linux/irq.h>
+#include <linux/nmi.h>
+#include <linux/smpboot.h>
+#include <linux/relay.h>
+#include <linux/slab.h>
+#include <linux/percpu-rwsem.h>
+#include <linux/cpuset.h>
+#include <linux/random.h>
+
+#include <trace/events/power.h>
+#define CREATE_TRACE_POINTS
+#include <trace/events/cpuhp.h>
+
+#include "smpboot.h"
+
+/**
+ * cpuhp_cpu_state - Per cpu hotplug state storage
+ * @state:	The current cpu state
+ * @target:	The target state
+ * @thread:	Pointer to the hotplug thread
+ * @should_run:	Thread should execute
+ * @rollback:	Perform a rollback
+ * @single:	Single callback invocation
+ * @bringup:	Single callback bringup or teardown selector
+ * @cb_state:	The state for a single callback (install/uninstall)
+ * @result:	Result of the operation
+ * @done_up:	Signal completion to the issuer of the task for cpu-up
+ * @done_down:	Signal completion to the issuer of the task for cpu-down
+ */
+struct cpuhp_cpu_state {
+	enum cpuhp_state	state;
+	enum cpuhp_state	target;
+	enum cpuhp_state	fail;
+#ifdef CONFIG_SMP
+	struct task_struct	*thread;
+	bool			should_run;
+	bool			rollback;
+	bool			single;
+	bool			bringup;
+	bool			booted_once;
+	struct hlist_node	*node;
+	struct hlist_node	*last;
+	enum cpuhp_state	cb_state;
+	int			result;
+	struct completion	done_up;
+	struct completion	done_down;
+#endif
+};
+
+static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
+	.fail = CPUHP_INVALID,
+};
+
+#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
+static struct lockdep_map cpuhp_state_up_map =
+	STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
+static struct lockdep_map cpuhp_state_down_map =
+	STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
+
+
+static inline void cpuhp_lock_acquire(bool bringup)
+{
+	lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
+}
+
+static inline void cpuhp_lock_release(bool bringup)
+{
+	lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
+}
+#else
+
+static inline void cpuhp_lock_acquire(bool bringup) { }
+static inline void cpuhp_lock_release(bool bringup) { }
+
+#endif
+
+/**
+ * cpuhp_step - Hotplug state machine step
+ * @name:	Name of the step
+ * @startup:	Startup function of the step
+ * @teardown:	Teardown function of the step
+ * @cant_stop:	Bringup/teardown can't be stopped at this step
+ */
+struct cpuhp_step {
+	const char		*name;
+	union {
+		int		(*single)(unsigned int cpu);
+		int		(*multi)(unsigned int cpu,
+					 struct hlist_node *node);
+	} startup;
+	union {
+		int		(*single)(unsigned int cpu);
+		int		(*multi)(unsigned int cpu,
+					 struct hlist_node *node);
+	} teardown;
+	struct hlist_head	list;
+	bool			cant_stop;
+	bool			multi_instance;
+};
+
+static DEFINE_MUTEX(cpuhp_state_mutex);
+static struct cpuhp_step cpuhp_hp_states[];
+
+static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
+{
+	return cpuhp_hp_states + state;
+}
+
+/**
+ * cpuhp_invoke_callback _ Invoke the callbacks for a given state
+ * @cpu:	The cpu for which the callback should be invoked
+ * @state:	The state to do callbacks for
+ * @bringup:	True if the bringup callback should be invoked
+ * @node:	For multi-instance, do a single entry callback for install/remove
+ * @lastp:	For multi-instance rollback, remember how far we got
+ *
+ * Called from cpu hotplug and from the state register machinery.
+ */
+static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
+				 bool bringup, struct hlist_node *node,
+				 struct hlist_node **lastp)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+	struct cpuhp_step *step = cpuhp_get_step(state);
+	int (*cbm)(unsigned int cpu, struct hlist_node *node);
+	int (*cb)(unsigned int cpu);
+	int ret, cnt;
+
+	if (st->fail == state) {
+		st->fail = CPUHP_INVALID;
+
+		if (!(bringup ? step->startup.single : step->teardown.single))
+			return 0;
+
+		return -EAGAIN;
+	}
+
+	if (!step->multi_instance) {
+		WARN_ON_ONCE(lastp && *lastp);
+		cb = bringup ? step->startup.single : step->teardown.single;
+		if (!cb)
+			return 0;
+		trace_cpuhp_enter(cpu, st->target, state, cb);
+		ret = cb(cpu);
+		trace_cpuhp_exit(cpu, st->state, state, ret);
+		return ret;
+	}
+	cbm = bringup ? step->startup.multi : step->teardown.multi;
+	if (!cbm)
+		return 0;
+
+	/* Single invocation for instance add/remove */
+	if (node) {
+		WARN_ON_ONCE(lastp && *lastp);
+		trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
+		ret = cbm(cpu, node);
+		trace_cpuhp_exit(cpu, st->state, state, ret);
+		return ret;
+	}
+
+	/* State transition. Invoke on all instances */
+	cnt = 0;
+	hlist_for_each(node, &step->list) {
+		if (lastp && node == *lastp)
+			break;
+
+		trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
+		ret = cbm(cpu, node);
+		trace_cpuhp_exit(cpu, st->state, state, ret);
+		if (ret) {
+			if (!lastp)
+				goto err;
+
+			*lastp = node;
+			return ret;
+		}
+		cnt++;
+	}
+	if (lastp)
+		*lastp = NULL;
+	return 0;
+err:
+	/* Rollback the instances if one failed */
+	cbm = !bringup ? step->startup.multi : step->teardown.multi;
+	if (!cbm)
+		return ret;
+
+	hlist_for_each(node, &step->list) {
+		if (!cnt--)
+			break;
+
+		trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
+		ret = cbm(cpu, node);
+		trace_cpuhp_exit(cpu, st->state, state, ret);
+		/*
+		 * Rollback must not fail,
+		 */
+		WARN_ON_ONCE(ret);
+	}
+	return ret;
+}
+
+#ifdef CONFIG_SMP
+static bool cpuhp_is_ap_state(enum cpuhp_state state)
+{
+	/*
+	 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
+	 * purposes as that state is handled explicitly in cpu_down.
+	 */
+	return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
+}
+
+static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
+{
+	struct completion *done = bringup ? &st->done_up : &st->done_down;
+	wait_for_completion(done);
+}
+
+static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
+{
+	struct completion *done = bringup ? &st->done_up : &st->done_down;
+	complete(done);
+}
+
+/*
+ * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
+ */
+static bool cpuhp_is_atomic_state(enum cpuhp_state state)
+{
+	return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
+}
+
+/* Serializes the updates to cpu_online_mask, cpu_present_mask */
+static DEFINE_MUTEX(cpu_add_remove_lock);
+bool cpuhp_tasks_frozen;
+EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
+
+/*
+ * The following two APIs (cpu_maps_update_begin/done) must be used when
+ * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
+ */
+void cpu_maps_update_begin(void)
+{
+	mutex_lock(&cpu_add_remove_lock);
+}
+
+void cpu_maps_update_done(void)
+{
+	mutex_unlock(&cpu_add_remove_lock);
+}
+
+/*
+ * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
+ * Should always be manipulated under cpu_add_remove_lock
+ */
+static int cpu_hotplug_disabled;
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
+
+void cpus_read_lock(void)
+{
+	percpu_down_read(&cpu_hotplug_lock);
+}
+EXPORT_SYMBOL_GPL(cpus_read_lock);
+
+int cpus_read_trylock(void)
+{
+	return percpu_down_read_trylock(&cpu_hotplug_lock);
+}
+EXPORT_SYMBOL_GPL(cpus_read_trylock);
+
+void cpus_read_unlock(void)
+{
+	percpu_up_read(&cpu_hotplug_lock);
+}
+EXPORT_SYMBOL_GPL(cpus_read_unlock);
+
+void cpus_write_lock(void)
+{
+	percpu_down_write(&cpu_hotplug_lock);
+}
+
+void cpus_write_unlock(void)
+{
+	percpu_up_write(&cpu_hotplug_lock);
+}
+
+void lockdep_assert_cpus_held(void)
+{
+	/*
+	 * We can't have hotplug operations before userspace starts running,
+	 * and some init codepaths will knowingly not take the hotplug lock.
+	 * This is all valid, so mute lockdep until it makes sense to report
+	 * unheld locks.
+	 */
+	if (system_state < SYSTEM_RUNNING)
+		return;
+
+	percpu_rwsem_assert_held(&cpu_hotplug_lock);
+}
+
+/*
+ * Wait for currently running CPU hotplug operations to complete (if any) and
+ * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
+ * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
+ * hotplug path before performing hotplug operations. So acquiring that lock
+ * guarantees mutual exclusion from any currently running hotplug operations.
+ */
+void cpu_hotplug_disable(void)
+{
+	cpu_maps_update_begin();
+	cpu_hotplug_disabled++;
+	cpu_maps_update_done();
+}
+EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
+
+static void __cpu_hotplug_enable(void)
+{
+	if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
+		return;
+	cpu_hotplug_disabled--;
+}
+
+void cpu_hotplug_enable(void)
+{
+	cpu_maps_update_begin();
+	__cpu_hotplug_enable();
+	cpu_maps_update_done();
+}
+EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
+#endif	/* CONFIG_HOTPLUG_CPU */
+
+/*
+ * Architectures that need SMT-specific errata handling during SMT hotplug
+ * should override this.
+ */
+void __weak arch_smt_update(void) { }
+
+#ifdef CONFIG_HOTPLUG_SMT
+enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
+
+void __init cpu_smt_disable(bool force)
+{
+	if (cpu_smt_control == CPU_SMT_FORCE_DISABLED ||
+		cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
+		return;
+
+	if (force) {
+		pr_info("SMT: Force disabled\n");
+		cpu_smt_control = CPU_SMT_FORCE_DISABLED;
+	} else {
+		pr_info("SMT: disabled\n");
+		cpu_smt_control = CPU_SMT_DISABLED;
+	}
+}
+
+/*
+ * The decision whether SMT is supported can only be done after the full
+ * CPU identification. Called from architecture code.
+ */
+void __init cpu_smt_check_topology(void)
+{
+	if (!topology_smt_supported())
+		cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
+}
+
+static int __init smt_cmdline_disable(char *str)
+{
+	cpu_smt_disable(str && !strcmp(str, "force"));
+	return 0;
+}
+early_param("nosmt", smt_cmdline_disable);
+
+static inline bool cpu_smt_allowed(unsigned int cpu)
+{
+	if (cpu_smt_control == CPU_SMT_ENABLED)
+		return true;
+
+	if (topology_is_primary_thread(cpu))
+		return true;
+
+	/*
+	 * On x86 it's required to boot all logical CPUs at least once so
+	 * that the init code can get a chance to set CR4.MCE on each
+	 * CPU. Otherwise, a broadacasted MCE observing CR4.MCE=0b on any
+	 * core will shutdown the machine.
+	 */
+	return !per_cpu(cpuhp_state, cpu).booted_once;
+}
+#else
+static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
+#endif
+
+static inline enum cpuhp_state
+cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
+{
+	enum cpuhp_state prev_state = st->state;
+
+	st->rollback = false;
+	st->last = NULL;
+
+	st->target = target;
+	st->single = false;
+	st->bringup = st->state < target;
+
+	return prev_state;
+}
+
+static inline void
+cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
+{
+	st->rollback = true;
+
+	/*
+	 * If we have st->last we need to undo partial multi_instance of this
+	 * state first. Otherwise start undo at the previous state.
+	 */
+	if (!st->last) {
+		if (st->bringup)
+			st->state--;
+		else
+			st->state++;
+	}
+
+	st->target = prev_state;
+	st->bringup = !st->bringup;
+}
+
+/* Regular hotplug invocation of the AP hotplug thread */
+static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
+{
+	if (!st->single && st->state == st->target)
+		return;
+
+	st->result = 0;
+	/*
+	 * Make sure the above stores are visible before should_run becomes
+	 * true. Paired with the mb() above in cpuhp_thread_fun()
+	 */
+	smp_mb();
+	st->should_run = true;
+	wake_up_process(st->thread);
+	wait_for_ap_thread(st, st->bringup);
+}
+
+static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
+{
+	enum cpuhp_state prev_state;
+	int ret;
+
+	prev_state = cpuhp_set_state(st, target);
+	__cpuhp_kick_ap(st);
+	if ((ret = st->result)) {
+		cpuhp_reset_state(st, prev_state);
+		__cpuhp_kick_ap(st);
+	}
+
+	return ret;
+}
+
+static int bringup_wait_for_ap(unsigned int cpu)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+
+	/* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
+	wait_for_ap_thread(st, true);
+	if (WARN_ON_ONCE((!cpu_online(cpu))))
+		return -ECANCELED;
+
+	/* Unpark the hotplug thread of the target cpu */
+	kthread_unpark(st->thread);
+
+	/*
+	 * SMT soft disabling on X86 requires to bring the CPU out of the
+	 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit.  The
+	 * CPU marked itself as booted_once in cpu_notify_starting() so the
+	 * cpu_smt_allowed() check will now return false if this is not the
+	 * primary sibling.
+	 */
+	if (!cpu_smt_allowed(cpu))
+		return -ECANCELED;
+
+	if (st->target <= CPUHP_AP_ONLINE_IDLE)
+		return 0;
+
+	return cpuhp_kick_ap(st, st->target);
+}
+
+static int bringup_cpu(unsigned int cpu)
+{
+	struct task_struct *idle = idle_thread_get(cpu);
+	int ret;
+
+	/*
+	 * Some architectures have to walk the irq descriptors to
+	 * setup the vector space for the cpu which comes online.
+	 * Prevent irq alloc/free across the bringup.
+	 */
+	irq_lock_sparse();
+
+	/* Arch-specific enabling code. */
+	ret = __cpu_up(cpu, idle);
+	irq_unlock_sparse();
+	if (ret)
+		return ret;
+	return bringup_wait_for_ap(cpu);
+}
+
+static int finish_cpu(unsigned int cpu)
+{
+	struct task_struct *idle = idle_thread_get(cpu);
+	struct mm_struct *mm = idle->active_mm;
+
+	/*
+	 * idle_task_exit() will have switched to &init_mm, now
+	 * clean up any remaining active_mm state.
+	 */
+	if (mm != &init_mm)
+		idle->active_mm = &init_mm;
+	mmdrop(mm);
+	return 0;
+}
+
+/*
+ * Hotplug state machine related functions
+ */
+
+static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
+{
+	for (st->state--; st->state > st->target; st->state--)
+		cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
+}
+
+static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
+{
+	if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
+		return true;
+	/*
+	 * When CPU hotplug is disabled, then taking the CPU down is not
+	 * possible because takedown_cpu() and the architecture and
+	 * subsystem specific mechanisms are not available. So the CPU
+	 * which would be completely unplugged again needs to stay around
+	 * in the current state.
+	 */
+	return st->state <= CPUHP_BRINGUP_CPU;
+}
+
+static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
+			      enum cpuhp_state target)
+{
+	enum cpuhp_state prev_state = st->state;
+	int ret = 0;
+
+	while (st->state < target) {
+		st->state++;
+		ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
+		if (ret) {
+			if (can_rollback_cpu(st)) {
+				st->target = prev_state;
+				undo_cpu_up(cpu, st);
+			}
+			break;
+		}
+	}
+	return ret;
+}
+
+/*
+ * The cpu hotplug threads manage the bringup and teardown of the cpus
+ */
+static void cpuhp_create(unsigned int cpu)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+
+	init_completion(&st->done_up);
+	init_completion(&st->done_down);
+}
+
+static int cpuhp_should_run(unsigned int cpu)
+{
+	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+
+	return st->should_run;
+}
+
+/*
+ * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
+ * callbacks when a state gets [un]installed at runtime.
+ *
+ * Each invocation of this function by the smpboot thread does a single AP
+ * state callback.
+ *
+ * It has 3 modes of operation:
+ *  - single: runs st->cb_state
+ *  - up:     runs ++st->state, while st->state < st->target
+ *  - down:   runs st->state--, while st->state > st->target
+ *
+ * When complete or on error, should_run is cleared and the completion is fired.
+ */
+static void cpuhp_thread_fun(unsigned int cpu)
+{
+	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+	bool bringup = st->bringup;
+	enum cpuhp_state state;
+
+	if (WARN_ON_ONCE(!st->should_run))
+		return;
+
+	/*
+	 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
+	 * that if we see ->should_run we also see the rest of the state.
+	 */
+	smp_mb();
+
+	cpuhp_lock_acquire(bringup);
+
+	if (st->single) {
+		state = st->cb_state;
+		st->should_run = false;
+	} else {
+		if (bringup) {
+			st->state++;
+			state = st->state;
+			st->should_run = (st->state < st->target);
+			WARN_ON_ONCE(st->state > st->target);
+		} else {
+			state = st->state;
+			st->state--;
+			st->should_run = (st->state > st->target);
+			WARN_ON_ONCE(st->state < st->target);
+		}
+	}
+
+	WARN_ON_ONCE(!cpuhp_is_ap_state(state));
+
+	if (cpuhp_is_atomic_state(state)) {
+		local_irq_disable();
+		st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
+		local_irq_enable();
+
+		/*
+		 * STARTING/DYING must not fail!
+		 */
+		WARN_ON_ONCE(st->result);
+	} else {
+		st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
+	}
+
+	if (st->result) {
+		/*
+		 * If we fail on a rollback, we're up a creek without no
+		 * paddle, no way forward, no way back. We loose, thanks for
+		 * playing.
+		 */
+		WARN_ON_ONCE(st->rollback);
+		st->should_run = false;
+	}
+
+	cpuhp_lock_release(bringup);
+
+	if (!st->should_run)
+		complete_ap_thread(st, bringup);
+}
+
+/* Invoke a single callback on a remote cpu */
+static int
+cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
+			 struct hlist_node *node)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+	int ret;
+
+	if (!cpu_online(cpu))
+		return 0;
+
+	cpuhp_lock_acquire(false);
+	cpuhp_lock_release(false);
+
+	cpuhp_lock_acquire(true);
+	cpuhp_lock_release(true);
+
+	/*
+	 * If we are up and running, use the hotplug thread. For early calls
+	 * we invoke the thread function directly.
+	 */
+	if (!st->thread)
+		return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
+
+	st->rollback = false;
+	st->last = NULL;
+
+	st->node = node;
+	st->bringup = bringup;
+	st->cb_state = state;
+	st->single = true;
+
+	__cpuhp_kick_ap(st);
+
+	/*
+	 * If we failed and did a partial, do a rollback.
+	 */
+	if ((ret = st->result) && st->last) {
+		st->rollback = true;
+		st->bringup = !bringup;
+
+		__cpuhp_kick_ap(st);
+	}
+
+	/*
+	 * Clean up the leftovers so the next hotplug operation wont use stale
+	 * data.
+	 */
+	st->node = st->last = NULL;
+	return ret;
+}
+
+static int cpuhp_kick_ap_work(unsigned int cpu)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+	enum cpuhp_state prev_state = st->state;
+	int ret;
+
+	cpuhp_lock_acquire(false);
+	cpuhp_lock_release(false);
+
+	cpuhp_lock_acquire(true);
+	cpuhp_lock_release(true);
+
+	trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
+	ret = cpuhp_kick_ap(st, st->target);
+	trace_cpuhp_exit(cpu, st->state, prev_state, ret);
+
+	return ret;
+}
+
+static struct smp_hotplug_thread cpuhp_threads = {
+	.store			= &cpuhp_state.thread,
+	.create			= &cpuhp_create,
+	.thread_should_run	= cpuhp_should_run,
+	.thread_fn		= cpuhp_thread_fun,
+	.thread_comm		= "cpuhp/%u",
+	.selfparking		= true,
+};
+
+void __init cpuhp_threads_init(void)
+{
+	BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
+	kthread_unpark(this_cpu_read(cpuhp_state.thread));
+}
+
+/*
+ *
+ * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
+ * protected region.
+ *
+ * The operation is still serialized against concurrent CPU hotplug via
+ * cpu_add_remove_lock, i.e. CPU map protection.  But it is _not_
+ * serialized against other hotplug related activity like adding or
+ * removing of state callbacks and state instances, which invoke either the
+ * startup or the teardown callback of the affected state.
+ *
+ * This is required for subsystems which are unfixable vs. CPU hotplug and
+ * evade lock inversion problems by scheduling work which has to be
+ * completed _before_ cpu_up()/_cpu_down() returns.
+ *
+ * Don't even think about adding anything to this for any new code or even
+ * drivers. It's only purpose is to keep existing lock order trainwrecks
+ * working.
+ *
+ * For cpu_down() there might be valid reasons to finish cleanups which are
+ * not required to be done under cpu_hotplug_lock, but that's a different
+ * story and would be not invoked via this.
+ */
+static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
+{
+	/*
+	 * cpusets delegate hotplug operations to a worker to "solve" the
+	 * lock order problems. Wait for the worker, but only if tasks are
+	 * _not_ frozen (suspend, hibernate) as that would wait forever.
+	 *
+	 * The wait is required because otherwise the hotplug operation
+	 * returns with inconsistent state, which could even be observed in
+	 * user space when a new CPU is brought up. The CPU plug uevent
+	 * would be delivered and user space reacting on it would fail to
+	 * move tasks to the newly plugged CPU up to the point where the
+	 * work has finished because up to that point the newly plugged CPU
+	 * is not assignable in cpusets/cgroups. On unplug that's not
+	 * necessarily a visible issue, but it is still inconsistent state,
+	 * which is the real problem which needs to be "fixed". This can't
+	 * prevent the transient state between scheduling the work and
+	 * returning from waiting for it.
+	 */
+	if (!tasks_frozen)
+		cpuset_wait_for_hotplug();
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+#ifndef arch_clear_mm_cpumask_cpu
+#define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
+#endif
+
+/**
+ * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
+ * @cpu: a CPU id
+ *
+ * This function walks all processes, finds a valid mm struct for each one and
+ * then clears a corresponding bit in mm's cpumask.  While this all sounds
+ * trivial, there are various non-obvious corner cases, which this function
+ * tries to solve in a safe manner.
+ *
+ * Also note that the function uses a somewhat relaxed locking scheme, so it may
+ * be called only for an already offlined CPU.
+ */
+void clear_tasks_mm_cpumask(int cpu)
+{
+	struct task_struct *p;
+
+	/*
+	 * This function is called after the cpu is taken down and marked
+	 * offline, so its not like new tasks will ever get this cpu set in
+	 * their mm mask. -- Peter Zijlstra
+	 * Thus, we may use rcu_read_lock() here, instead of grabbing
+	 * full-fledged tasklist_lock.
+	 */
+	WARN_ON(cpu_online(cpu));
+	rcu_read_lock();
+	for_each_process(p) {
+		struct task_struct *t;
+
+		/*
+		 * Main thread might exit, but other threads may still have
+		 * a valid mm. Find one.
+		 */
+		t = find_lock_task_mm(p);
+		if (!t)
+			continue;
+		arch_clear_mm_cpumask_cpu(cpu, t->mm);
+		task_unlock(t);
+	}
+	rcu_read_unlock();
+}
+
+/* Take this CPU down. */
+static int take_cpu_down(void *_param)
+{
+	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+	enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
+	int err, cpu = smp_processor_id();
+	int ret;
+
+	/* Ensure this CPU doesn't handle any more interrupts. */
+	err = __cpu_disable();
+	if (err < 0)
+		return err;
+
+	/*
+	 * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
+	 * do this step again.
+	 */
+	WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
+	st->state--;
+	/* Invoke the former CPU_DYING callbacks */
+	for (; st->state > target; st->state--) {
+		ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
+		/*
+		 * DYING must not fail!
+		 */
+		WARN_ON_ONCE(ret);
+	}
+
+	/* Give up timekeeping duties */
+	tick_handover_do_timer();
+	/* Park the stopper thread */
+	stop_machine_park(cpu);
+	return 0;
+}
+
+static int takedown_cpu(unsigned int cpu)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+	int err;
+
+	/* Park the smpboot threads */
+	kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
+
+	/*
+	 * Prevent irq alloc/free while the dying cpu reorganizes the
+	 * interrupt affinities.
+	 */
+	irq_lock_sparse();
+
+	/*
+	 * So now all preempt/rcu users must observe !cpu_active().
+	 */
+	err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
+	if (err) {
+		/* CPU refused to die */
+		irq_unlock_sparse();
+		/* Unpark the hotplug thread so we can rollback there */
+		kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
+		return err;
+	}
+	BUG_ON(cpu_online(cpu));
+
+	/*
+	 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
+	 * all runnable tasks from the CPU, there's only the idle task left now
+	 * that the migration thread is done doing the stop_machine thing.
+	 *
+	 * Wait for the stop thread to go away.
+	 */
+	wait_for_ap_thread(st, false);
+	BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
+
+	/* Interrupts are moved away from the dying cpu, reenable alloc/free */
+	irq_unlock_sparse();
+
+	hotplug_cpu__broadcast_tick_pull(cpu);
+	/* This actually kills the CPU. */
+	__cpu_die(cpu);
+
+	tick_cleanup_dead_cpu(cpu);
+	rcutree_migrate_callbacks(cpu);
+	return 0;
+}
+
+static void cpuhp_complete_idle_dead(void *arg)
+{
+	struct cpuhp_cpu_state *st = arg;
+
+	complete_ap_thread(st, false);
+}
+
+void cpuhp_report_idle_dead(void)
+{
+	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+
+	BUG_ON(st->state != CPUHP_AP_OFFLINE);
+	rcu_report_dead(smp_processor_id());
+	st->state = CPUHP_AP_IDLE_DEAD;
+	/*
+	 * We cannot call complete after rcu_report_dead() so we delegate it
+	 * to an online cpu.
+	 */
+	smp_call_function_single(cpumask_first(cpu_online_mask),
+				 cpuhp_complete_idle_dead, st, 0);
+}
+
+static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
+{
+	for (st->state++; st->state < st->target; st->state++)
+		cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
+}
+
+static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
+				enum cpuhp_state target)
+{
+	enum cpuhp_state prev_state = st->state;
+	int ret = 0;
+
+	for (; st->state > target; st->state--) {
+		ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
+		if (ret) {
+			st->target = prev_state;
+			if (st->state < prev_state)
+				undo_cpu_down(cpu, st);
+			break;
+		}
+	}
+	return ret;
+}
+
+/* Requires cpu_add_remove_lock to be held */
+static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
+			   enum cpuhp_state target)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+	int prev_state, ret = 0;
+
+	if (num_online_cpus() == 1)
+		return -EBUSY;
+
+	if (!cpu_present(cpu))
+		return -EINVAL;
+
+	cpus_write_lock();
+
+	cpuhp_tasks_frozen = tasks_frozen;
+
+	prev_state = cpuhp_set_state(st, target);
+	/*
+	 * If the current CPU state is in the range of the AP hotplug thread,
+	 * then we need to kick the thread.
+	 */
+	if (st->state > CPUHP_TEARDOWN_CPU) {
+		st->target = max((int)target, CPUHP_TEARDOWN_CPU);
+		ret = cpuhp_kick_ap_work(cpu);
+		/*
+		 * The AP side has done the error rollback already. Just
+		 * return the error code..
+		 */
+		if (ret)
+			goto out;
+
+		/*
+		 * We might have stopped still in the range of the AP hotplug
+		 * thread. Nothing to do anymore.
+		 */
+		if (st->state > CPUHP_TEARDOWN_CPU)
+			goto out;
+
+		st->target = target;
+	}
+	/*
+	 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
+	 * to do the further cleanups.
+	 */
+	ret = cpuhp_down_callbacks(cpu, st, target);
+	if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
+		cpuhp_reset_state(st, prev_state);
+		__cpuhp_kick_ap(st);
+	}
+
+out:
+	cpus_write_unlock();
+	/*
+	 * Do post unplug cleanup. This is still protected against
+	 * concurrent CPU hotplug via cpu_add_remove_lock.
+	 */
+	lockup_detector_cleanup();
+	arch_smt_update();
+	cpu_up_down_serialize_trainwrecks(tasks_frozen);
+	return ret;
+}
+
+static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
+{
+	if (cpu_hotplug_disabled)
+		return -EBUSY;
+	return _cpu_down(cpu, 0, target);
+}
+
+static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
+{
+	int err;
+
+	cpu_maps_update_begin();
+	err = cpu_down_maps_locked(cpu, target);
+	cpu_maps_update_done();
+	return err;
+}
+
+int cpu_down(unsigned int cpu)
+{
+	return do_cpu_down(cpu, CPUHP_OFFLINE);
+}
+EXPORT_SYMBOL(cpu_down);
+
+#else
+#define takedown_cpu		NULL
+#endif /*CONFIG_HOTPLUG_CPU*/
+
+/**
+ * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
+ * @cpu: cpu that just started
+ *
+ * It must be called by the arch code on the new cpu, before the new cpu
+ * enables interrupts and before the "boot" cpu returns from __cpu_up().
+ */
+void notify_cpu_starting(unsigned int cpu)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+	enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
+	int ret;
+
+	rcu_cpu_starting(cpu);	/* Enables RCU usage on this CPU. */
+	st->booted_once = true;
+	while (st->state < target) {
+		st->state++;
+		ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
+		/*
+		 * STARTING must not fail!
+		 */
+		WARN_ON_ONCE(ret);
+	}
+}
+
+/*
+ * Called from the idle task. Wake up the controlling task which brings the
+ * hotplug thread of the upcoming CPU up and then delegates the rest of the
+ * online bringup to the hotplug thread.
+ */
+void cpuhp_online_idle(enum cpuhp_state state)
+{
+	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+
+	/* Happens for the boot cpu */
+	if (state != CPUHP_AP_ONLINE_IDLE)
+		return;
+
+	/*
+	 * Unpart the stopper thread before we start the idle loop (and start
+	 * scheduling); this ensures the stopper task is always available.
+	 */
+	stop_machine_unpark(smp_processor_id());
+
+	st->state = CPUHP_AP_ONLINE_IDLE;
+	complete_ap_thread(st, true);
+}
+
+/* Requires cpu_add_remove_lock to be held */
+static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+	struct task_struct *idle;
+	int ret = 0;
+
+	cpus_write_lock();
+
+	if (!cpu_present(cpu)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/*
+	 * The caller of do_cpu_up might have raced with another
+	 * caller. Ignore it for now.
+	 */
+	if (st->state >= target)
+		goto out;
+
+	if (st->state == CPUHP_OFFLINE) {
+		/* Let it fail before we try to bring the cpu up */
+		idle = idle_thread_get(cpu);
+		if (IS_ERR(idle)) {
+			ret = PTR_ERR(idle);
+			goto out;
+		}
+	}
+
+	cpuhp_tasks_frozen = tasks_frozen;
+
+	cpuhp_set_state(st, target);
+	/*
+	 * If the current CPU state is in the range of the AP hotplug thread,
+	 * then we need to kick the thread once more.
+	 */
+	if (st->state > CPUHP_BRINGUP_CPU) {
+		ret = cpuhp_kick_ap_work(cpu);
+		/*
+		 * The AP side has done the error rollback already. Just
+		 * return the error code..
+		 */
+		if (ret)
+			goto out;
+	}
+
+	/*
+	 * Try to reach the target state. We max out on the BP at
+	 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
+	 * responsible for bringing it up to the target state.
+	 */
+	target = min((int)target, CPUHP_BRINGUP_CPU);
+	ret = cpuhp_up_callbacks(cpu, st, target);
+out:
+	cpus_write_unlock();
+	arch_smt_update();
+	cpu_up_down_serialize_trainwrecks(tasks_frozen);
+	return ret;
+}
+
+static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
+{
+	int err = 0;
+
+	if (!cpu_possible(cpu)) {
+		pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
+		       cpu);
+#if defined(CONFIG_IA64)
+		pr_err("please check additional_cpus= boot parameter\n");
+#endif
+		return -EINVAL;
+	}
+
+	err = try_online_node(cpu_to_node(cpu));
+	if (err)
+		return err;
+
+	cpu_maps_update_begin();
+
+	if (cpu_hotplug_disabled) {
+		err = -EBUSY;
+		goto out;
+	}
+	if (!cpu_smt_allowed(cpu)) {
+		err = -EPERM;
+		goto out;
+	}
+
+	err = _cpu_up(cpu, 0, target);
+out:
+	cpu_maps_update_done();
+	return err;
+}
+
+int cpu_up(unsigned int cpu)
+{
+	return do_cpu_up(cpu, CPUHP_ONLINE);
+}
+EXPORT_SYMBOL_GPL(cpu_up);
+
+#ifdef CONFIG_PM_SLEEP_SMP
+static cpumask_var_t frozen_cpus;
+
+int freeze_secondary_cpus(int primary)
+{
+	int cpu, error = 0;
+
+	cpu_maps_update_begin();
+	if (!cpu_online(primary))
+		primary = cpumask_first(cpu_online_mask);
+	/*
+	 * We take down all of the non-boot CPUs in one shot to avoid races
+	 * with the userspace trying to use the CPU hotplug at the same time
+	 */
+	cpumask_clear(frozen_cpus);
+
+	pr_info("Disabling non-boot CPUs ...\n");
+	for_each_online_cpu(cpu) {
+		if (cpu == primary)
+			continue;
+		trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
+		error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
+		trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
+		if (!error)
+			cpumask_set_cpu(cpu, frozen_cpus);
+		else {
+			pr_err("Error taking CPU%d down: %d\n", cpu, error);
+			break;
+		}
+	}
+
+	if (!error)
+		BUG_ON(num_online_cpus() > 1);
+	else
+		pr_err("Non-boot CPUs are not disabled\n");
+
+	/*
+	 * Make sure the CPUs won't be enabled by someone else. We need to do
+	 * this even in case of failure as all disable_nonboot_cpus() users are
+	 * supposed to do enable_nonboot_cpus() on the failure path.
+	 */
+	cpu_hotplug_disabled++;
+
+	cpu_maps_update_done();
+	return error;
+}
+
+void __weak arch_enable_nonboot_cpus_begin(void)
+{
+}
+
+void __weak arch_enable_nonboot_cpus_end(void)
+{
+}
+
+void enable_nonboot_cpus(void)
+{
+	int cpu, error;
+
+	/* Allow everyone to use the CPU hotplug again */
+	cpu_maps_update_begin();
+	__cpu_hotplug_enable();
+	if (cpumask_empty(frozen_cpus))
+		goto out;
+
+	pr_info("Enabling non-boot CPUs ...\n");
+
+	arch_enable_nonboot_cpus_begin();
+
+	for_each_cpu(cpu, frozen_cpus) {
+		trace_suspend_resume(TPS("CPU_ON"), cpu, true);
+		error = _cpu_up(cpu, 1, CPUHP_ONLINE);
+		trace_suspend_resume(TPS("CPU_ON"), cpu, false);
+		if (!error) {
+			pr_info("CPU%d is up\n", cpu);
+			continue;
+		}
+		pr_warn("Error taking CPU%d up: %d\n", cpu, error);
+	}
+
+	arch_enable_nonboot_cpus_end();
+
+	cpumask_clear(frozen_cpus);
+out:
+	cpu_maps_update_done();
+}
+
+static int __init alloc_frozen_cpus(void)
+{
+	if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
+		return -ENOMEM;
+	return 0;
+}
+core_initcall(alloc_frozen_cpus);
+
+/*
+ * When callbacks for CPU hotplug notifications are being executed, we must
+ * ensure that the state of the system with respect to the tasks being frozen
+ * or not, as reported by the notification, remains unchanged *throughout the
+ * duration* of the execution of the callbacks.
+ * Hence we need to prevent the freezer from racing with regular CPU hotplug.
+ *
+ * This synchronization is implemented by mutually excluding regular CPU
+ * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
+ * Hibernate notifications.
+ */
+static int
+cpu_hotplug_pm_callback(struct notifier_block *nb,
+			unsigned long action, void *ptr)
+{
+	switch (action) {
+
+	case PM_SUSPEND_PREPARE:
+	case PM_HIBERNATION_PREPARE:
+		cpu_hotplug_disable();
+		break;
+
+	case PM_POST_SUSPEND:
+	case PM_POST_HIBERNATION:
+		cpu_hotplug_enable();
+		break;
+
+	default:
+		return NOTIFY_DONE;
+	}
+
+	return NOTIFY_OK;
+}
+
+
+static int __init cpu_hotplug_pm_sync_init(void)
+{
+	/*
+	 * cpu_hotplug_pm_callback has higher priority than x86
+	 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
+	 * to disable cpu hotplug to avoid cpu hotplug race.
+	 */
+	pm_notifier(cpu_hotplug_pm_callback, 0);
+	return 0;
+}
+core_initcall(cpu_hotplug_pm_sync_init);
+
+#endif /* CONFIG_PM_SLEEP_SMP */
+
+int __boot_cpu_id;
+
+#endif /* CONFIG_SMP */
+
+/* Boot processor state steps */
+static struct cpuhp_step cpuhp_hp_states[] = {
+	[CPUHP_OFFLINE] = {
+		.name			= "offline",
+		.startup.single		= NULL,
+		.teardown.single	= NULL,
+	},
+#ifdef CONFIG_SMP
+	[CPUHP_CREATE_THREADS]= {
+		.name			= "threads:prepare",
+		.startup.single		= smpboot_create_threads,
+		.teardown.single	= NULL,
+		.cant_stop		= true,
+	},
+	[CPUHP_PERF_PREPARE] = {
+		.name			= "perf:prepare",
+		.startup.single		= perf_event_init_cpu,
+		.teardown.single	= perf_event_exit_cpu,
+	},
+	[CPUHP_RANDOM_PREPARE] = {
+		.name			= "random:prepare",
+		.startup.single		= random_prepare_cpu,
+		.teardown.single	= NULL,
+	},
+	[CPUHP_WORKQUEUE_PREP] = {
+		.name			= "workqueue:prepare",
+		.startup.single		= workqueue_prepare_cpu,
+		.teardown.single	= NULL,
+	},
+	[CPUHP_HRTIMERS_PREPARE] = {
+		.name			= "hrtimers:prepare",
+		.startup.single		= hrtimers_prepare_cpu,
+		.teardown.single	= hrtimers_dead_cpu,
+	},
+	[CPUHP_SMPCFD_PREPARE] = {
+		.name			= "smpcfd:prepare",
+		.startup.single		= smpcfd_prepare_cpu,
+		.teardown.single	= smpcfd_dead_cpu,
+	},
+	[CPUHP_RELAY_PREPARE] = {
+		.name			= "relay:prepare",
+		.startup.single		= relay_prepare_cpu,
+		.teardown.single	= NULL,
+	},
+	[CPUHP_SLAB_PREPARE] = {
+		.name			= "slab:prepare",
+		.startup.single		= slab_prepare_cpu,
+		.teardown.single	= slab_dead_cpu,
+	},
+	[CPUHP_RCUTREE_PREP] = {
+		.name			= "RCU/tree:prepare",
+		.startup.single		= rcutree_prepare_cpu,
+		.teardown.single	= rcutree_dead_cpu,
+	},
+	/*
+	 * On the tear-down path, timers_dead_cpu() must be invoked
+	 * before blk_mq_queue_reinit_notify() from notify_dead(),
+	 * otherwise a RCU stall occurs.
+	 */
+	[CPUHP_TIMERS_PREPARE] = {
+		.name			= "timers:prepare",
+		.startup.single		= timers_prepare_cpu,
+		.teardown.single	= timers_dead_cpu,
+	},
+	/* Kicks the plugged cpu into life */
+	[CPUHP_BRINGUP_CPU] = {
+		.name			= "cpu:bringup",
+		.startup.single		= bringup_cpu,
+		.teardown.single	= finish_cpu,
+		.cant_stop		= true,
+	},
+	/* Final state before CPU kills itself */
+	[CPUHP_AP_IDLE_DEAD] = {
+		.name			= "idle:dead",
+	},
+	/*
+	 * Last state before CPU enters the idle loop to die. Transient state
+	 * for synchronization.
+	 */
+	[CPUHP_AP_OFFLINE] = {
+		.name			= "ap:offline",
+		.cant_stop		= true,
+	},
+	/* First state is scheduler control. Interrupts are disabled */
+	[CPUHP_AP_SCHED_STARTING] = {
+		.name			= "sched:starting",
+		.startup.single		= sched_cpu_starting,
+		.teardown.single	= sched_cpu_dying,
+	},
+	[CPUHP_AP_RCUTREE_DYING] = {
+		.name			= "RCU/tree:dying",
+		.startup.single		= NULL,
+		.teardown.single	= rcutree_dying_cpu,
+	},
+	[CPUHP_AP_SMPCFD_DYING] = {
+		.name			= "smpcfd:dying",
+		.startup.single		= NULL,
+		.teardown.single	= smpcfd_dying_cpu,
+	},
+	/* Entry state on starting. Interrupts enabled from here on. Transient
+	 * state for synchronsization */
+	[CPUHP_AP_ONLINE] = {
+		.name			= "ap:online",
+	},
+	/*
+	 * Handled on controll processor until the plugged processor manages
+	 * this itself.
+	 */
+	[CPUHP_TEARDOWN_CPU] = {
+		.name			= "cpu:teardown",
+		.startup.single		= NULL,
+		.teardown.single	= takedown_cpu,
+		.cant_stop		= true,
+	},
+	/* Handle smpboot threads park/unpark */
+	[CPUHP_AP_SMPBOOT_THREADS] = {
+		.name			= "smpboot/threads:online",
+		.startup.single		= smpboot_unpark_threads,
+		.teardown.single	= smpboot_park_threads,
+	},
+	[CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
+		.name			= "irq/affinity:online",
+		.startup.single		= irq_affinity_online_cpu,
+		.teardown.single	= NULL,
+	},
+	[CPUHP_AP_PERF_ONLINE] = {
+		.name			= "perf:online",
+		.startup.single		= perf_event_init_cpu,
+		.teardown.single	= perf_event_exit_cpu,
+	},
+	[CPUHP_AP_WATCHDOG_ONLINE] = {
+		.name			= "lockup_detector:online",
+		.startup.single		= lockup_detector_online_cpu,
+		.teardown.single	= lockup_detector_offline_cpu,
+	},
+	[CPUHP_AP_WORKQUEUE_ONLINE] = {
+		.name			= "workqueue:online",
+		.startup.single		= workqueue_online_cpu,
+		.teardown.single	= workqueue_offline_cpu,
+	},
+	[CPUHP_AP_RANDOM_ONLINE] = {
+		.name			= "random:online",
+		.startup.single		= random_online_cpu,
+		.teardown.single	= NULL,
+	},
+	[CPUHP_AP_RCUTREE_ONLINE] = {
+		.name			= "RCU/tree:online",
+		.startup.single		= rcutree_online_cpu,
+		.teardown.single	= rcutree_offline_cpu,
+	},
+#endif
+	/*
+	 * The dynamically registered state space is here
+	 */
+
+#ifdef CONFIG_SMP
+	/* Last state is scheduler control setting the cpu active */
+	[CPUHP_AP_ACTIVE] = {
+		.name			= "sched:active",
+		.startup.single		= sched_cpu_activate,
+		.teardown.single	= sched_cpu_deactivate,
+	},
+#endif
+
+	/* CPU is fully up and running. */
+	[CPUHP_ONLINE] = {
+		.name			= "online",
+		.startup.single		= NULL,
+		.teardown.single	= NULL,
+	},
+};
+
+/* Sanity check for callbacks */
+static int cpuhp_cb_check(enum cpuhp_state state)
+{
+	if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
+		return -EINVAL;
+	return 0;
+}
+
+/*
+ * Returns a free for dynamic slot assignment of the Online state. The states
+ * are protected by the cpuhp_slot_states mutex and an empty slot is identified
+ * by having no name assigned.
+ */
+static int cpuhp_reserve_state(enum cpuhp_state state)
+{
+	enum cpuhp_state i, end;
+	struct cpuhp_step *step;
+
+	switch (state) {
+	case CPUHP_AP_ONLINE_DYN:
+		step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
+		end = CPUHP_AP_ONLINE_DYN_END;
+		break;
+	case CPUHP_BP_PREPARE_DYN:
+		step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
+		end = CPUHP_BP_PREPARE_DYN_END;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	for (i = state; i <= end; i++, step++) {
+		if (!step->name)
+			return i;
+	}
+	WARN(1, "No more dynamic states available for CPU hotplug\n");
+	return -ENOSPC;
+}
+
+static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
+				 int (*startup)(unsigned int cpu),
+				 int (*teardown)(unsigned int cpu),
+				 bool multi_instance)
+{
+	/* (Un)Install the callbacks for further cpu hotplug operations */
+	struct cpuhp_step *sp;
+	int ret = 0;
+
+	/*
+	 * If name is NULL, then the state gets removed.
+	 *
+	 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
+	 * the first allocation from these dynamic ranges, so the removal
+	 * would trigger a new allocation and clear the wrong (already
+	 * empty) state, leaving the callbacks of the to be cleared state
+	 * dangling, which causes wreckage on the next hotplug operation.
+	 */
+	if (name && (state == CPUHP_AP_ONLINE_DYN ||
+		     state == CPUHP_BP_PREPARE_DYN)) {
+		ret = cpuhp_reserve_state(state);
+		if (ret < 0)
+			return ret;
+		state = ret;
+	}
+	sp = cpuhp_get_step(state);
+	if (name && sp->name)
+		return -EBUSY;
+
+	sp->startup.single = startup;
+	sp->teardown.single = teardown;
+	sp->name = name;
+	sp->multi_instance = multi_instance;
+	INIT_HLIST_HEAD(&sp->list);
+	return ret;
+}
+
+static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
+{
+	return cpuhp_get_step(state)->teardown.single;
+}
+
+/*
+ * Call the startup/teardown function for a step either on the AP or
+ * on the current CPU.
+ */
+static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
+			    struct hlist_node *node)
+{
+	struct cpuhp_step *sp = cpuhp_get_step(state);
+	int ret;
+
+	/*
+	 * If there's nothing to do, we done.
+	 * Relies on the union for multi_instance.
+	 */
+	if ((bringup && !sp->startup.single) ||
+	    (!bringup && !sp->teardown.single))
+		return 0;
+	/*
+	 * The non AP bound callbacks can fail on bringup. On teardown
+	 * e.g. module removal we crash for now.
+	 */
+#ifdef CONFIG_SMP
+	if (cpuhp_is_ap_state(state))
+		ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
+	else
+		ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
+#else
+	ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
+#endif
+	BUG_ON(ret && !bringup);
+	return ret;
+}
+
+/*
+ * Called from __cpuhp_setup_state on a recoverable failure.
+ *
+ * Note: The teardown callbacks for rollback are not allowed to fail!
+ */
+static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
+				   struct hlist_node *node)
+{
+	int cpu;
+
+	/* Roll back the already executed steps on the other cpus */
+	for_each_present_cpu(cpu) {
+		struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+		int cpustate = st->state;
+
+		if (cpu >= failedcpu)
+			break;
+
+		/* Did we invoke the startup call on that cpu ? */
+		if (cpustate >= state)
+			cpuhp_issue_call(cpu, state, false, node);
+	}
+}
+
+int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
+					  struct hlist_node *node,
+					  bool invoke)
+{
+	struct cpuhp_step *sp;
+	int cpu;
+	int ret;
+
+	lockdep_assert_cpus_held();
+
+	sp = cpuhp_get_step(state);
+	if (sp->multi_instance == false)
+		return -EINVAL;
+
+	mutex_lock(&cpuhp_state_mutex);
+
+	if (!invoke || !sp->startup.multi)
+		goto add_node;
+
+	/*
+	 * Try to call the startup callback for each present cpu
+	 * depending on the hotplug state of the cpu.
+	 */
+	for_each_present_cpu(cpu) {
+		struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+		int cpustate = st->state;
+
+		if (cpustate < state)
+			continue;
+
+		ret = cpuhp_issue_call(cpu, state, true, node);
+		if (ret) {
+			if (sp->teardown.multi)
+				cpuhp_rollback_install(cpu, state, node);
+			goto unlock;
+		}
+	}
+add_node:
+	ret = 0;
+	hlist_add_head(node, &sp->list);
+unlock:
+	mutex_unlock(&cpuhp_state_mutex);
+	return ret;
+}
+
+int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
+			       bool invoke)
+{
+	int ret;
+
+	cpus_read_lock();
+	ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
+	cpus_read_unlock();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
+
+/**
+ * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
+ * @state:		The state to setup
+ * @invoke:		If true, the startup function is invoked for cpus where
+ *			cpu state >= @state
+ * @startup:		startup callback function
+ * @teardown:		teardown callback function
+ * @multi_instance:	State is set up for multiple instances which get
+ *			added afterwards.
+ *
+ * The caller needs to hold cpus read locked while calling this function.
+ * Returns:
+ *   On success:
+ *      Positive state number if @state is CPUHP_AP_ONLINE_DYN
+ *      0 for all other states
+ *   On failure: proper (negative) error code
+ */
+int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
+				   const char *name, bool invoke,
+				   int (*startup)(unsigned int cpu),
+				   int (*teardown)(unsigned int cpu),
+				   bool multi_instance)
+{
+	int cpu, ret = 0;
+	bool dynstate;
+
+	lockdep_assert_cpus_held();
+
+	if (cpuhp_cb_check(state) || !name)
+		return -EINVAL;
+
+	mutex_lock(&cpuhp_state_mutex);
+
+	ret = cpuhp_store_callbacks(state, name, startup, teardown,
+				    multi_instance);
+
+	dynstate = state == CPUHP_AP_ONLINE_DYN;
+	if (ret > 0 && dynstate) {
+		state = ret;
+		ret = 0;
+	}
+
+	if (ret || !invoke || !startup)
+		goto out;
+
+	/*
+	 * Try to call the startup callback for each present cpu
+	 * depending on the hotplug state of the cpu.
+	 */
+	for_each_present_cpu(cpu) {
+		struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+		int cpustate = st->state;
+
+		if (cpustate < state)
+			continue;
+
+		ret = cpuhp_issue_call(cpu, state, true, NULL);
+		if (ret) {
+			if (teardown)
+				cpuhp_rollback_install(cpu, state, NULL);
+			cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
+			goto out;
+		}
+	}
+out:
+	mutex_unlock(&cpuhp_state_mutex);
+	/*
+	 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
+	 * dynamically allocated state in case of success.
+	 */
+	if (!ret && dynstate)
+		return state;
+	return ret;
+}
+EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
+
+int __cpuhp_setup_state(enum cpuhp_state state,
+			const char *name, bool invoke,
+			int (*startup)(unsigned int cpu),
+			int (*teardown)(unsigned int cpu),
+			bool multi_instance)
+{
+	int ret;
+
+	cpus_read_lock();
+	ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
+					     teardown, multi_instance);
+	cpus_read_unlock();
+	return ret;
+}
+EXPORT_SYMBOL(__cpuhp_setup_state);
+
+int __cpuhp_state_remove_instance(enum cpuhp_state state,
+				  struct hlist_node *node, bool invoke)
+{
+	struct cpuhp_step *sp = cpuhp_get_step(state);
+	int cpu;
+
+	BUG_ON(cpuhp_cb_check(state));
+
+	if (!sp->multi_instance)
+		return -EINVAL;
+
+	cpus_read_lock();
+	mutex_lock(&cpuhp_state_mutex);
+
+	if (!invoke || !cpuhp_get_teardown_cb(state))
+		goto remove;
+	/*
+	 * Call the teardown callback for each present cpu depending
+	 * on the hotplug state of the cpu. This function is not
+	 * allowed to fail currently!
+	 */
+	for_each_present_cpu(cpu) {
+		struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+		int cpustate = st->state;
+
+		if (cpustate >= state)
+			cpuhp_issue_call(cpu, state, false, node);
+	}
+
+remove:
+	hlist_del(node);
+	mutex_unlock(&cpuhp_state_mutex);
+	cpus_read_unlock();
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
+
+/**
+ * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
+ * @state:	The state to remove
+ * @invoke:	If true, the teardown function is invoked for cpus where
+ *		cpu state >= @state
+ *
+ * The caller needs to hold cpus read locked while calling this function.
+ * The teardown callback is currently not allowed to fail. Think
+ * about module removal!
+ */
+void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
+{
+	struct cpuhp_step *sp = cpuhp_get_step(state);
+	int cpu;
+
+	BUG_ON(cpuhp_cb_check(state));
+
+	lockdep_assert_cpus_held();
+
+	mutex_lock(&cpuhp_state_mutex);
+	if (sp->multi_instance) {
+		WARN(!hlist_empty(&sp->list),
+		     "Error: Removing state %d which has instances left.\n",
+		     state);
+		goto remove;
+	}
+
+	if (!invoke || !cpuhp_get_teardown_cb(state))
+		goto remove;
+
+	/*
+	 * Call the teardown callback for each present cpu depending
+	 * on the hotplug state of the cpu. This function is not
+	 * allowed to fail currently!
+	 */
+	for_each_present_cpu(cpu) {
+		struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+		int cpustate = st->state;
+
+		if (cpustate >= state)
+			cpuhp_issue_call(cpu, state, false, NULL);
+	}
+remove:
+	cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
+	mutex_unlock(&cpuhp_state_mutex);
+}
+EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
+
+void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
+{
+	cpus_read_lock();
+	__cpuhp_remove_state_cpuslocked(state, invoke);
+	cpus_read_unlock();
+}
+EXPORT_SYMBOL(__cpuhp_remove_state);
+
+#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
+static ssize_t show_cpuhp_state(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+
+	return sprintf(buf, "%d\n", st->state);
+}
+static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
+
+static ssize_t write_cpuhp_target(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+	struct cpuhp_step *sp;
+	int target, ret;
+
+	ret = kstrtoint(buf, 10, &target);
+	if (ret)
+		return ret;
+
+#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
+	if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
+		return -EINVAL;
+#else
+	if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
+		return -EINVAL;
+#endif
+
+	ret = lock_device_hotplug_sysfs();
+	if (ret)
+		return ret;
+
+	mutex_lock(&cpuhp_state_mutex);
+	sp = cpuhp_get_step(target);
+	ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
+	mutex_unlock(&cpuhp_state_mutex);
+	if (ret)
+		goto out;
+
+	if (st->state < target)
+		ret = do_cpu_up(dev->id, target);
+	else
+		ret = do_cpu_down(dev->id, target);
+out:
+	unlock_device_hotplug();
+	return ret ? ret : count;
+}
+
+static ssize_t show_cpuhp_target(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+
+	return sprintf(buf, "%d\n", st->target);
+}
+static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
+
+
+static ssize_t write_cpuhp_fail(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+	struct cpuhp_step *sp;
+	int fail, ret;
+
+	ret = kstrtoint(buf, 10, &fail);
+	if (ret)
+		return ret;
+
+	if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
+		return -EINVAL;
+
+	/*
+	 * Cannot fail STARTING/DYING callbacks.
+	 */
+	if (cpuhp_is_atomic_state(fail))
+		return -EINVAL;
+
+	/*
+	 * Cannot fail anything that doesn't have callbacks.
+	 */
+	mutex_lock(&cpuhp_state_mutex);
+	sp = cpuhp_get_step(fail);
+	if (!sp->startup.single && !sp->teardown.single)
+		ret = -EINVAL;
+	mutex_unlock(&cpuhp_state_mutex);
+	if (ret)
+		return ret;
+
+	st->fail = fail;
+
+	return count;
+}
+
+static ssize_t show_cpuhp_fail(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+
+	return sprintf(buf, "%d\n", st->fail);
+}
+
+static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_fail);
+
+static struct attribute *cpuhp_cpu_attrs[] = {
+	&dev_attr_state.attr,
+	&dev_attr_target.attr,
+	&dev_attr_fail.attr,
+	NULL
+};
+
+static const struct attribute_group cpuhp_cpu_attr_group = {
+	.attrs = cpuhp_cpu_attrs,
+	.name = "hotplug",
+	NULL
+};
+
+static ssize_t show_cpuhp_states(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	ssize_t cur, res = 0;
+	int i;
+
+	mutex_lock(&cpuhp_state_mutex);
+	for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
+		struct cpuhp_step *sp = cpuhp_get_step(i);
+
+		if (sp->name) {
+			cur = sprintf(buf, "%3d: %s\n", i, sp->name);
+			buf += cur;
+			res += cur;
+		}
+	}
+	mutex_unlock(&cpuhp_state_mutex);
+	return res;
+}
+static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
+
+static struct attribute *cpuhp_cpu_root_attrs[] = {
+	&dev_attr_states.attr,
+	NULL
+};
+
+static const struct attribute_group cpuhp_cpu_root_attr_group = {
+	.attrs = cpuhp_cpu_root_attrs,
+	.name = "hotplug",
+	NULL
+};
+
+#ifdef CONFIG_HOTPLUG_SMT
+
+static const char *smt_states[] = {
+	[CPU_SMT_ENABLED]		= "on",
+	[CPU_SMT_DISABLED]		= "off",
+	[CPU_SMT_FORCE_DISABLED]	= "forceoff",
+	[CPU_SMT_NOT_SUPPORTED]		= "notsupported",
+};
+
+static ssize_t
+show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE - 2, "%s\n", smt_states[cpu_smt_control]);
+}
+
+static void cpuhp_offline_cpu_device(unsigned int cpu)
+{
+	struct device *dev = get_cpu_device(cpu);
+
+	dev->offline = true;
+	/* Tell user space about the state change */
+	kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
+}
+
+static void cpuhp_online_cpu_device(unsigned int cpu)
+{
+	struct device *dev = get_cpu_device(cpu);
+
+	dev->offline = false;
+	/* Tell user space about the state change */
+	kobject_uevent(&dev->kobj, KOBJ_ONLINE);
+}
+
+int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
+{
+	int cpu, ret = 0;
+
+	cpu_maps_update_begin();
+	for_each_online_cpu(cpu) {
+		if (topology_is_primary_thread(cpu))
+			continue;
+		ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
+		if (ret)
+			break;
+		/*
+		 * As this needs to hold the cpu maps lock it's impossible
+		 * to call device_offline() because that ends up calling
+		 * cpu_down() which takes cpu maps lock. cpu maps lock
+		 * needs to be held as this might race against in kernel
+		 * abusers of the hotplug machinery (thermal management).
+		 *
+		 * So nothing would update device:offline state. That would
+		 * leave the sysfs entry stale and prevent onlining after
+		 * smt control has been changed to 'off' again. This is
+		 * called under the sysfs hotplug lock, so it is properly
+		 * serialized against the regular offline usage.
+		 */
+		cpuhp_offline_cpu_device(cpu);
+	}
+	if (!ret)
+		cpu_smt_control = ctrlval;
+	cpu_maps_update_done();
+	return ret;
+}
+
+int cpuhp_smt_enable(void)
+{
+	int cpu, ret = 0;
+
+	cpu_maps_update_begin();
+	cpu_smt_control = CPU_SMT_ENABLED;
+	for_each_present_cpu(cpu) {
+		/* Skip online CPUs and CPUs on offline nodes */
+		if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
+			continue;
+		ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
+		if (ret)
+			break;
+		/* See comment in cpuhp_smt_disable() */
+		cpuhp_online_cpu_device(cpu);
+	}
+	cpu_maps_update_done();
+	return ret;
+}
+
+static ssize_t
+store_smt_control(struct device *dev, struct device_attribute *attr,
+		  const char *buf, size_t count)
+{
+	int ctrlval, ret;
+
+	if (sysfs_streq(buf, "on"))
+		ctrlval = CPU_SMT_ENABLED;
+	else if (sysfs_streq(buf, "off"))
+		ctrlval = CPU_SMT_DISABLED;
+	else if (sysfs_streq(buf, "forceoff"))
+		ctrlval = CPU_SMT_FORCE_DISABLED;
+	else
+		return -EINVAL;
+
+	if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
+		return -EPERM;
+
+	if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
+		return -ENODEV;
+
+	ret = lock_device_hotplug_sysfs();
+	if (ret)
+		return ret;
+
+	if (ctrlval != cpu_smt_control) {
+		switch (ctrlval) {
+		case CPU_SMT_ENABLED:
+			ret = cpuhp_smt_enable();
+			break;
+		case CPU_SMT_DISABLED:
+		case CPU_SMT_FORCE_DISABLED:
+			ret = cpuhp_smt_disable(ctrlval);
+			break;
+		}
+	}
+
+	unlock_device_hotplug();
+	return ret ? ret : count;
+}
+static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control);
+
+static ssize_t
+show_smt_active(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	bool active = topology_max_smt_threads() > 1;
+
+	return snprintf(buf, PAGE_SIZE - 2, "%d\n", active);
+}
+static DEVICE_ATTR(active, 0444, show_smt_active, NULL);
+
+static struct attribute *cpuhp_smt_attrs[] = {
+	&dev_attr_control.attr,
+	&dev_attr_active.attr,
+	NULL
+};
+
+static const struct attribute_group cpuhp_smt_attr_group = {
+	.attrs = cpuhp_smt_attrs,
+	.name = "smt",
+	NULL
+};
+
+static int __init cpu_smt_state_init(void)
+{
+	return sysfs_create_group(&cpu_subsys.dev_root->kobj,
+				  &cpuhp_smt_attr_group);
+}
+
+#else
+static inline int cpu_smt_state_init(void) { return 0; }
+#endif
+
+static int __init cpuhp_sysfs_init(void)
+{
+	int cpu, ret;
+
+	ret = cpu_smt_state_init();
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
+				 &cpuhp_cpu_root_attr_group);
+	if (ret)
+		return ret;
+
+	for_each_possible_cpu(cpu) {
+		struct device *dev = get_cpu_device(cpu);
+
+		if (!dev)
+			continue;
+		ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+device_initcall(cpuhp_sysfs_init);
+#endif
+
+/*
+ * cpu_bit_bitmap[] is a special, "compressed" data structure that
+ * represents all NR_CPUS bits binary values of 1<<nr.
+ *
+ * It is used by cpumask_of() to get a constant address to a CPU
+ * mask value that has a single bit set only.
+ */
+
+/* cpu_bit_bitmap[0] is empty - so we can back into it */
+#define MASK_DECLARE_1(x)	[x+1][0] = (1UL << (x))
+#define MASK_DECLARE_2(x)	MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
+#define MASK_DECLARE_4(x)	MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
+#define MASK_DECLARE_8(x)	MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
+
+const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
+
+	MASK_DECLARE_8(0),	MASK_DECLARE_8(8),
+	MASK_DECLARE_8(16),	MASK_DECLARE_8(24),
+#if BITS_PER_LONG > 32
+	MASK_DECLARE_8(32),	MASK_DECLARE_8(40),
+	MASK_DECLARE_8(48),	MASK_DECLARE_8(56),
+#endif
+};
+EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
+
+const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
+EXPORT_SYMBOL(cpu_all_bits);
+
+#ifdef CONFIG_INIT_ALL_POSSIBLE
+struct cpumask __cpu_possible_mask __read_mostly
+	= {CPU_BITS_ALL};
+#else
+struct cpumask __cpu_possible_mask __read_mostly;
+#endif
+EXPORT_SYMBOL(__cpu_possible_mask);
+
+struct cpumask __cpu_online_mask __read_mostly;
+EXPORT_SYMBOL(__cpu_online_mask);
+
+struct cpumask __cpu_present_mask __read_mostly;
+EXPORT_SYMBOL(__cpu_present_mask);
+
+struct cpumask __cpu_active_mask __read_mostly;
+EXPORT_SYMBOL(__cpu_active_mask);
+
+void init_cpu_present(const struct cpumask *src)
+{
+	cpumask_copy(&__cpu_present_mask, src);
+}
+
+void init_cpu_possible(const struct cpumask *src)
+{
+	cpumask_copy(&__cpu_possible_mask, src);
+}
+
+void init_cpu_online(const struct cpumask *src)
+{
+	cpumask_copy(&__cpu_online_mask, src);
+}
+
+/*
+ * Activate the first processor.
+ */
+void __init boot_cpu_init(void)
+{
+	int cpu = smp_processor_id();
+
+	/* Mark the boot cpu "present", "online" etc for SMP and UP case */
+	set_cpu_online(cpu, true);
+	set_cpu_active(cpu, true);
+	set_cpu_present(cpu, true);
+	set_cpu_possible(cpu, true);
+
+#ifdef CONFIG_SMP
+	__boot_cpu_id = cpu;
+#endif
+}
+
+/*
+ * Must be called _AFTER_ setting up the per_cpu areas
+ */
+void __init boot_cpu_hotplug_init(void)
+{
+#ifdef CONFIG_SMP
+	this_cpu_write(cpuhp_state.booted_once, true);
+#endif
+	this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
+}
+
+/*
+ * These are used for a global "mitigations=" cmdline option for toggling
+ * optional CPU mitigations.
+ */
+enum cpu_mitigations {
+	CPU_MITIGATIONS_OFF,
+	CPU_MITIGATIONS_AUTO,
+	CPU_MITIGATIONS_AUTO_NOSMT,
+};
+
+static enum cpu_mitigations cpu_mitigations __ro_after_init =
+	CPU_MITIGATIONS_AUTO;
+
+static int __init mitigations_parse_cmdline(char *arg)
+{
+	if (!strcmp(arg, "off"))
+		cpu_mitigations = CPU_MITIGATIONS_OFF;
+	else if (!strcmp(arg, "auto"))
+		cpu_mitigations = CPU_MITIGATIONS_AUTO;
+	else if (!strcmp(arg, "auto,nosmt"))
+		cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
+	else
+		pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
+			arg);
+
+	return 0;
+}
+early_param("mitigations", mitigations_parse_cmdline);
+
+/* mitigations=off */
+bool cpu_mitigations_off(void)
+{
+	return cpu_mitigations == CPU_MITIGATIONS_OFF;
+}
+EXPORT_SYMBOL_GPL(cpu_mitigations_off);
+
+/* mitigations=auto,nosmt */
+bool cpu_mitigations_auto_nosmt(void)
+{
+	return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
+}
+EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);