arch/powerpc/platforms/pseries/hotplug-cpu.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * 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
  */

 #define pr_fmt(fmt)     "pseries-hotplug-cpu: " fmt

 #include <linux/kernel.h>
 #include <linux/interrupt.h>
 #include <linux/delay.h>
 #include <linux/sched.h>	/* for idle_task_exit */
 #include <linux/sched/hotplug.h>
 #include <linux/cpu.h>
 #include <linux/of.h>
 #include <linux/slab.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/xive.h>
 #include <asm/plpar_wrappers.h>
 #include <asm/topology.h>

 #include "pseries.h"

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

 static void rtas_stop_self(void)
 {
 	static struct rtas_args args;

 	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());

 	rtas_call_unlocked(&args, rtas_stop_self_token, 0, 1, NULL);

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

 static void pseries_cpu_offline_self(void)
 {
 	unsigned int hwcpu = hard_smp_processor_id();

 	local_irq_disable();
 	idle_task_exit();
 	if (xive_enabled())
 		xive_teardown_cpu();
 	else
 		xics_teardown_cpu();

 	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 */
 	if (xive_enabled())
 		xive_smp_disable_cpu();
 	else
 		xics_migrate_irqs_away();

 	cleanup_cpu_mmu_context();

 	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_cpu_offline_self() is called by the @cpu when it wants to
  * self-destruct.
  */
 static void pseries_cpu_die(unsigned int cpu)
 {
 	int cpu_status = 1;
 	unsigned int pcpu = get_hard_smp_processor_id(cpu);
 	unsigned long timeout = jiffies + msecs_to_jiffies(120000);

 	while (true) {
 		cpu_status = smp_query_cpu_stopped(pcpu);
 		if (cpu_status == QCSS_STOPPED ||
 		    cpu_status == QCSS_HARDWARE_ERROR)
 			break;

 		if (time_after(jiffies, timeout)) {
 			pr_warn("CPU %i (hwid %i) didn't die after 120 seconds\n",
 				cpu, pcpu);
 			timeout = jiffies + msecs_to_jiffies(120000);
 		}

 		cond_resched();
 	}

 	if (cpu_status == QCSS_HARDWARE_ERROR) {
 		pr_warn("CPU %i (hwid %i) reported error while dying\n",
 			cpu, pcpu);
 	}

 	/* 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_ptrs[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 %pOF; this system configuration"
 		       " supports %d logical cpus.\n", np,
 		       num_possible_cpus());
 		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 %pOFn with %d thread(s)\n", np,
 		       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);
 			update_numa_cpu_lookup_table(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 dlpar_offline_cpu(struct device_node *dn)
 {
 	int rc = 0;
 	unsigned int cpu;
 	int len, nthreads, i;
 	const __be32 *intserv;
 	u32 thread;

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

 	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;

 			if (!cpu_online(cpu))
 				break;

 			cpu_maps_update_done();
 			rc = device_offline(get_cpu_device(cpu));
 			if (rc)
 				goto out;
 			cpu_maps_update_begin();
 			break;
 		}
 		if (cpu == num_possible_cpus()) {
 			pr_warn("Could not find cpu to offline with physical id 0x%x\n",
 				thread);
 		}
 	}
 	cpu_maps_update_done();

 out:
 	return rc;
 }

 static int dlpar_online_cpu(struct device_node *dn)
 {
 	int rc = 0;
 	unsigned int cpu;
 	int len, nthreads, i;
 	const __be32 *intserv;
 	u32 thread;

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

 	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;
 			cpu_maps_update_done();
 			find_and_online_cpu_nid(cpu);
 			rc = device_online(get_cpu_device(cpu));
 			if (rc) {
 				dlpar_offline_cpu(dn);
 				goto out;
 			}
 			cpu_maps_update_begin();

 			break;
 		}
 		if (cpu == num_possible_cpus())
 			printk(KERN_WARNING "Could not find cpu to online "
 			       "with physical id 0x%x\n", thread);
 	}
 	cpu_maps_update_done();

 out:
 	return rc;

 }

 static bool dlpar_cpu_exists(struct device_node *parent, u32 drc_index)
 {
 	struct device_node *child = NULL;
 	u32 my_drc_index;
 	bool found;
 	int rc;

 	/* Assume cpu doesn't exist */
 	found = false;

 	for_each_child_of_node(parent, child) {
 		rc = of_property_read_u32(child, "ibm,my-drc-index",
 					  &my_drc_index);
 		if (rc)
 			continue;

 		if (my_drc_index == drc_index) {
 			of_node_put(child);
 			found = true;
 			break;
 		}
 	}

 	return found;
 }

 static bool drc_info_valid_index(struct device_node *parent, u32 drc_index)
 {
 	struct property *info;
 	struct of_drc_info drc;
 	const __be32 *value;
 	u32 index;
 	int count, i, j;

 	info = of_find_property(parent, "ibm,drc-info", NULL);
 	if (!info)
 		return false;

 	value = of_prop_next_u32(info, NULL, &count);

 	/* First value of ibm,drc-info is number of drc-info records */
 	if (value)
 		value++;
 	else
 		return false;

 	for (i = 0; i < count; i++) {
 		if (of_read_drc_info_cell(&info, &value, &drc))
 			return false;

 		if (strncmp(drc.drc_type, "CPU", 3))
 			break;

 		if (drc_index > drc.last_drc_index)
 			continue;

 		index = drc.drc_index_start;
 		for (j = 0; j < drc.num_sequential_elems; j++) {
 			if (drc_index == index)
 				return true;

 			index += drc.sequential_inc;
 		}
 	}

 	return false;
 }

 static bool valid_cpu_drc_index(struct device_node *parent, u32 drc_index)
 {
 	bool found = false;
 	int rc, index;

 	if (of_find_property(parent, "ibm,drc-info", NULL))
 		return drc_info_valid_index(parent, drc_index);

 	/* Note that the format of the ibm,drc-indexes array is
 	 * the number of entries in the array followed by the array
 	 * of drc values so we start looking at index = 1.
 	 */
 	index = 1;
 	while (!found) {
 		u32 drc;

 		rc = of_property_read_u32_index(parent, "ibm,drc-indexes",
 						index++, &drc);

 		if (rc)
 			break;

 		if (drc == drc_index)
 			found = true;
 	}

 	return found;
 }

 static ssize_t dlpar_cpu_add(u32 drc_index)
 {
 	struct device_node *dn, *parent;
 	int rc, saved_rc;

 	pr_debug("Attempting to add CPU, drc index: %x\n", drc_index);

 	parent = of_find_node_by_path("/cpus");
 	if (!parent) {
 		pr_warn("Failed to find CPU root node \"/cpus\"\n");
 		return -ENODEV;
 	}

 	if (dlpar_cpu_exists(parent, drc_index)) {
 		of_node_put(parent);
 		pr_warn("CPU with drc index %x already exists\n", drc_index);
 		return -EINVAL;
 	}

 	if (!valid_cpu_drc_index(parent, drc_index)) {
 		of_node_put(parent);
 		pr_warn("Cannot find CPU (drc index %x) to add.\n", drc_index);
 		return -EINVAL;
 	}

 	rc = dlpar_acquire_drc(drc_index);
 	if (rc) {
 		pr_warn("Failed to acquire DRC, rc: %d, drc index: %x\n",
 			rc, drc_index);
 		of_node_put(parent);
 		return -EINVAL;
 	}

 	dn = dlpar_configure_connector(cpu_to_be32(drc_index), parent);
 	if (!dn) {
 		pr_warn("Failed call to configure-connector, drc index: %x\n",
 			drc_index);
 		dlpar_release_drc(drc_index);
 		of_node_put(parent);
 		return -EINVAL;
 	}

 	rc = dlpar_attach_node(dn, parent);

 	/* Regardless we are done with parent now */
 	of_node_put(parent);

 	if (rc) {
 		saved_rc = rc;
 		pr_warn("Failed to attach node %pOFn, rc: %d, drc index: %x\n",
 			dn, rc, drc_index);

 		rc = dlpar_release_drc(drc_index);
 		if (!rc)
 			dlpar_free_cc_nodes(dn);

 		return saved_rc;
 	}

 	rc = dlpar_online_cpu(dn);
 	if (rc) {
 		saved_rc = rc;
 		pr_warn("Failed to online cpu %pOFn, rc: %d, drc index: %x\n",
 			dn, rc, drc_index);

 		rc = dlpar_detach_node(dn);
 		if (!rc)
 			dlpar_release_drc(drc_index);

 		return saved_rc;
 	}

 	pr_debug("Successfully added CPU %pOFn, drc index: %x\n", dn,
 		 drc_index);
 	return rc;
 }

 static ssize_t dlpar_cpu_remove(struct device_node *dn, u32 drc_index)
 {
 	int rc;

 	pr_debug("Attempting to remove CPU %pOFn, drc index: %x\n",
 		 dn, drc_index);

 	rc = dlpar_offline_cpu(dn);
 	if (rc) {
 		pr_warn("Failed to offline CPU %pOFn, rc: %d\n", dn, rc);
 		return -EINVAL;
 	}

 	rc = dlpar_release_drc(drc_index);
 	if (rc) {
 		pr_warn("Failed to release drc (%x) for CPU %pOFn, rc: %d\n",
 			drc_index, dn, rc);
 		dlpar_online_cpu(dn);
 		return rc;
 	}

 	rc = dlpar_detach_node(dn);
 	if (rc) {
 		int saved_rc = rc;

 		pr_warn("Failed to detach CPU %pOFn, rc: %d", dn, rc);

 		rc = dlpar_acquire_drc(drc_index);
 		if (!rc)
 			dlpar_online_cpu(dn);

 		return saved_rc;
 	}

 	pr_debug("Successfully removed CPU, drc index: %x\n", drc_index);
 	return 0;
 }

 static struct device_node *cpu_drc_index_to_dn(u32 drc_index)
 {
 	struct device_node *dn;
 	u32 my_index;
 	int rc;

 	for_each_node_by_type(dn, "cpu") {
 		rc = of_property_read_u32(dn, "ibm,my-drc-index", &my_index);
 		if (rc)
 			continue;

 		if (my_index == drc_index)
 			break;
 	}

 	return dn;
 }

 static int dlpar_cpu_remove_by_index(u32 drc_index)
 {
 	struct device_node *dn;
 	int rc;

 	dn = cpu_drc_index_to_dn(drc_index);
 	if (!dn) {
 		pr_warn("Cannot find CPU (drc index %x) to remove\n",
 			drc_index);
 		return -ENODEV;
 	}

 	rc = dlpar_cpu_remove(dn, drc_index);
 	of_node_put(dn);
 	return rc;
 }

 static int find_dlpar_cpus_to_remove(u32 *cpu_drcs, int cpus_to_remove)
 {
 	struct device_node *dn;
 	int cpus_found = 0;
 	int rc;

 	/* We want to find cpus_to_remove + 1 CPUs to ensure we do not
 	 * remove the last CPU.
 	 */
 	for_each_node_by_type(dn, "cpu") {
 		cpus_found++;

 		if (cpus_found > cpus_to_remove) {
 			of_node_put(dn);
 			break;
 		}

 		/* Note that cpus_found is always 1 ahead of the index
 		 * into the cpu_drcs array, so we use cpus_found - 1
 		 */
 		rc = of_property_read_u32(dn, "ibm,my-drc-index",
 					  &cpu_drcs[cpus_found - 1]);
 		if (rc) {
 			pr_warn("Error occurred getting drc-index for %pOFn\n",
 				dn);
 			of_node_put(dn);
 			return -1;
 		}
 	}

 	if (cpus_found < cpus_to_remove) {
 		pr_warn("Failed to find enough CPUs (%d of %d) to remove\n",
 			cpus_found, cpus_to_remove);
 	} else if (cpus_found == cpus_to_remove) {
 		pr_warn("Cannot remove all CPUs\n");
 	}

 	return cpus_found;
 }

 static int dlpar_cpu_remove_by_count(u32 cpus_to_remove)
 {
 	u32 *cpu_drcs;
 	int cpus_found;
 	int cpus_removed = 0;
 	int i, rc;

 	pr_debug("Attempting to hot-remove %d CPUs\n", cpus_to_remove);

 	cpu_drcs = kcalloc(cpus_to_remove, sizeof(*cpu_drcs), GFP_KERNEL);
 	if (!cpu_drcs)
 		return -EINVAL;

 	cpus_found = find_dlpar_cpus_to_remove(cpu_drcs, cpus_to_remove);
 	if (cpus_found <= cpus_to_remove) {
 		kfree(cpu_drcs);
 		return -EINVAL;
 	}

 	for (i = 0; i < cpus_to_remove; i++) {
 		rc = dlpar_cpu_remove_by_index(cpu_drcs[i]);
 		if (rc)
 			break;

 		cpus_removed++;
 	}

 	if (cpus_removed != cpus_to_remove) {
 		pr_warn("CPU hot-remove failed, adding back removed CPUs\n");

 		for (i = 0; i < cpus_removed; i++)
 			dlpar_cpu_add(cpu_drcs[i]);

 		rc = -EINVAL;
 	} else {
 		rc = 0;
 	}

 	kfree(cpu_drcs);
 	return rc;
 }

 static int find_drc_info_cpus_to_add(struct device_node *cpus,
 				     struct property *info,
 				     u32 *cpu_drcs, u32 cpus_to_add)
 {
 	struct of_drc_info drc;
 	const __be32 *value;
 	u32 count, drc_index;
 	int cpus_found = 0;
 	int i, j;

 	if (!info)
 		return -1;

 	value = of_prop_next_u32(info, NULL, &count);
 	if (value)
 		value++;

 	for (i = 0; i < count; i++) {
 		of_read_drc_info_cell(&info, &value, &drc);
 		if (strncmp(drc.drc_type, "CPU", 3))
 			break;

 		drc_index = drc.drc_index_start;
 		for (j = 0; j < drc.num_sequential_elems; j++) {
 			if (dlpar_cpu_exists(cpus, drc_index))
 				continue;

 			cpu_drcs[cpus_found++] = drc_index;

 			if (cpus_found == cpus_to_add)
 				return cpus_found;

 			drc_index += drc.sequential_inc;
 		}
 	}

 	return cpus_found;
 }

 static int find_drc_index_cpus_to_add(struct device_node *cpus,
 				      u32 *cpu_drcs, u32 cpus_to_add)
 {
 	int cpus_found = 0;
 	int index, rc;
 	u32 drc_index;

 	/* Search the ibm,drc-indexes array for possible CPU drcs to
 	 * add. Note that the format of the ibm,drc-indexes array is
 	 * the number of entries in the array followed by the array
 	 * of drc values so we start looking at index = 1.
 	 */
 	index = 1;
 	while (cpus_found < cpus_to_add) {
 		rc = of_property_read_u32_index(cpus, "ibm,drc-indexes",
 						index++, &drc_index);

 		if (rc)
 			break;

 		if (dlpar_cpu_exists(cpus, drc_index))
 			continue;

 		cpu_drcs[cpus_found++] = drc_index;
 	}

 	return cpus_found;
 }

 static int dlpar_cpu_add_by_count(u32 cpus_to_add)
 {
 	struct device_node *parent;
 	struct property *info;
 	u32 *cpu_drcs;
 	int cpus_added = 0;
 	int cpus_found;
 	int i, rc;

 	pr_debug("Attempting to hot-add %d CPUs\n", cpus_to_add);

 	cpu_drcs = kcalloc(cpus_to_add, sizeof(*cpu_drcs), GFP_KERNEL);
 	if (!cpu_drcs)
 		return -EINVAL;

 	parent = of_find_node_by_path("/cpus");
 	if (!parent) {
 		pr_warn("Could not find CPU root node in device tree\n");
 		kfree(cpu_drcs);
 		return -1;
 	}

 	info = of_find_property(parent, "ibm,drc-info", NULL);
 	if (info)
 		cpus_found = find_drc_info_cpus_to_add(parent, info, cpu_drcs, cpus_to_add);
 	else
 		cpus_found = find_drc_index_cpus_to_add(parent, cpu_drcs, cpus_to_add);

 	of_node_put(parent);

 	if (cpus_found < cpus_to_add) {
 		pr_warn("Failed to find enough CPUs (%d of %d) to add\n",
 			cpus_found, cpus_to_add);
 		kfree(cpu_drcs);
 		return -EINVAL;
 	}

 	for (i = 0; i < cpus_to_add; i++) {
 		rc = dlpar_cpu_add(cpu_drcs[i]);
 		if (rc)
 			break;

 		cpus_added++;
 	}

 	if (cpus_added < cpus_to_add) {
 		pr_warn("CPU hot-add failed, removing any added CPUs\n");

 		for (i = 0; i < cpus_added; i++)
 			dlpar_cpu_remove_by_index(cpu_drcs[i]);

 		rc = -EINVAL;
 	} else {
 		rc = 0;
 	}

 	kfree(cpu_drcs);
 	return rc;
 }

 int dlpar_cpu(struct pseries_hp_errorlog *hp_elog)
 {
 	u32 count, drc_index;
 	int rc;

 	count = hp_elog->_drc_u.drc_count;
 	drc_index = hp_elog->_drc_u.drc_index;

 	lock_device_hotplug();

 	switch (hp_elog->action) {
 	case PSERIES_HP_ELOG_ACTION_REMOVE:
 		if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_COUNT)
 			rc = dlpar_cpu_remove_by_count(count);
 		else if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX)
 			rc = dlpar_cpu_remove_by_index(drc_index);
 		else
 			rc = -EINVAL;
 		break;
 	case PSERIES_HP_ELOG_ACTION_ADD:
 		if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_COUNT)
 			rc = dlpar_cpu_add_by_count(count);
 		else if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX)
 			rc = dlpar_cpu_add(drc_index);
 		else
 			rc = -EINVAL;
 		break;
 	default:
 		pr_err("Invalid action (%d) specified\n", hp_elog->action);
 		rc = -EINVAL;
 		break;
 	}

 	unlock_device_hotplug();
 	return rc;
 }

 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE

 static ssize_t dlpar_cpu_probe(const char *buf, size_t count)
 {
 	u32 drc_index;
 	int rc;

 	rc = kstrtou32(buf, 0, &drc_index);
 	if (rc)
 		return -EINVAL;

 	rc = dlpar_cpu_add(drc_index);

 	return rc ? rc : count;
 }

 static ssize_t dlpar_cpu_release(const char *buf, size_t count)
 {
 	struct device_node *dn;
 	u32 drc_index;
 	int rc;

 	dn = of_find_node_by_path(buf);
 	if (!dn)
 		return -EINVAL;

 	rc = of_property_read_u32(dn, "ibm,my-drc-index", &drc_index);
 	if (rc) {
 		of_node_put(dn);
 		return -EINVAL;
 	}

 	rc = dlpar_cpu_remove(dn, drc_index);
 	of_node_put(dn);

 	return rc ? rc : count;
 }

 #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */

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

 	switch (action) {
 	case OF_RECONFIG_ATTACH_NODE:
 		err = pseries_add_processor(rd->dn);
 		break;
 	case OF_RECONFIG_DETACH_NODE:
 		pseries_remove_processor(rd->dn);
 		break;
 	}
 	return notifier_from_errno(err);
 }

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

 static int __init pseries_cpu_hotplug_init(void)
 {
 	int qcss_tok;

 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 	ppc_md.cpu_probe = dlpar_cpu_probe;
 	ppc_md.cpu_release = dlpar_cpu_release;
 #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */

 	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;
 	}

 	smp_ops->cpu_offline_self = pseries_cpu_offline_self;
 	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);

 	return 0;
 }
 machine_arch_initcall(pseries, pseries_cpu_hotplug_init);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* 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
	*/

	#define pr_fmt(fmt) "pseries-hotplug-cpu: " fmt

	#include <linux/kernel.h>
	#include <linux/interrupt.h>
	#include <linux/delay.h>
	#include <linux/sched.h> /* for idle_task_exit */
	#include <linux/sched/hotplug.h>
	#include <linux/cpu.h>
	#include <linux/of.h>
	#include <linux/slab.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/xive.h>
	#include <asm/plpar_wrappers.h>
	#include <asm/topology.h>

	#include "pseries.h"

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

	static void rtas_stop_self(void)
	{
	static struct rtas_args args;

	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());

	rtas_call_unlocked(&args, rtas_stop_self_token, 0, 1, NULL);

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

	static void pseries_cpu_offline_self(void)
	{
	unsigned int hwcpu = hard_smp_processor_id();

	local_irq_disable();
	idle_task_exit();
	if (xive_enabled())
	xive_teardown_cpu();
	else
	xics_teardown_cpu();

	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 */
	if (xive_enabled())
	xive_smp_disable_cpu();
	else
	xics_migrate_irqs_away();

	cleanup_cpu_mmu_context();

	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_cpu_offline_self() is called by the @cpu when it wants to
	* self-destruct.
	*/
	static void pseries_cpu_die(unsigned int cpu)
	{
	int cpu_status = 1;
	unsigned int pcpu = get_hard_smp_processor_id(cpu);
	unsigned long timeout = jiffies + msecs_to_jiffies(120000);

	while (true) {
	cpu_status = smp_query_cpu_stopped(pcpu);
	if (cpu_status == QCSS_STOPPED \|\|
	cpu_status == QCSS_HARDWARE_ERROR)
	break;

	if (time_after(jiffies, timeout)) {
	pr_warn("CPU %i (hwid %i) didn't die after 120 seconds\n",
	cpu, pcpu);
	timeout = jiffies + msecs_to_jiffies(120000);
	}

	cond_resched();
	}

	if (cpu_status == QCSS_HARDWARE_ERROR) {
	pr_warn("CPU %i (hwid %i) reported error while dying\n",
	cpu, pcpu);
	}

	/* 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_ptrs[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 %pOF; this system configuration"
	" supports %d logical cpus.\n", np,
	num_possible_cpus());
	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 %pOFn with %d thread(s)\n", np,
	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);
	update_numa_cpu_lookup_table(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 dlpar_offline_cpu(struct device_node *dn)
	{
	int rc = 0;
	unsigned int cpu;
	int len, nthreads, i;
	const __be32 *intserv;
	u32 thread;

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

	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;

	if (!cpu_online(cpu))
	break;

	cpu_maps_update_done();
	rc = device_offline(get_cpu_device(cpu));
	if (rc)
	goto out;
	cpu_maps_update_begin();
	break;
	}
	if (cpu == num_possible_cpus()) {
	pr_warn("Could not find cpu to offline with physical id 0x%x\n",
	thread);
	}
	}
	cpu_maps_update_done();

	out:
	return rc;
	}

	static int dlpar_online_cpu(struct device_node *dn)
	{
	int rc = 0;
	unsigned int cpu;
	int len, nthreads, i;
	const __be32 *intserv;
	u32 thread;

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

	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;
	cpu_maps_update_done();
	find_and_online_cpu_nid(cpu);
	rc = device_online(get_cpu_device(cpu));
	if (rc) {
	dlpar_offline_cpu(dn);
	goto out;
	}
	cpu_maps_update_begin();

	break;
	}
	if (cpu == num_possible_cpus())
	printk(KERN_WARNING "Could not find cpu to online "
	"with physical id 0x%x\n", thread);
	}
	cpu_maps_update_done();

	out:
	return rc;

	}

	static bool dlpar_cpu_exists(struct device_node *parent, u32 drc_index)
	{
	struct device_node *child = NULL;
	u32 my_drc_index;
	bool found;
	int rc;

	/* Assume cpu doesn't exist */
	found = false;

	for_each_child_of_node(parent, child) {
	rc = of_property_read_u32(child, "ibm,my-drc-index",
	&my_drc_index);
	if (rc)
	continue;

	if (my_drc_index == drc_index) {
	of_node_put(child);
	found = true;
	break;
	}
	}

	return found;
	}

	static bool drc_info_valid_index(struct device_node *parent, u32 drc_index)
	{
	struct property *info;
	struct of_drc_info drc;
	const __be32 *value;
	u32 index;
	int count, i, j;

	info = of_find_property(parent, "ibm,drc-info", NULL);
	if (!info)
	return false;

	value = of_prop_next_u32(info, NULL, &count);

	/* First value of ibm,drc-info is number of drc-info records */
	if (value)
	value++;
	else
	return false;

	for (i = 0; i < count; i++) {
	if (of_read_drc_info_cell(&info, &value, &drc))
	return false;

	if (strncmp(drc.drc_type, "CPU", 3))
	break;

	if (drc_index > drc.last_drc_index)
	continue;

	index = drc.drc_index_start;
	for (j = 0; j < drc.num_sequential_elems; j++) {
	if (drc_index == index)
	return true;

	index += drc.sequential_inc;
	}
	}

	return false;
	}

	static bool valid_cpu_drc_index(struct device_node *parent, u32 drc_index)
	{
	bool found = false;
	int rc, index;

	if (of_find_property(parent, "ibm,drc-info", NULL))
	return drc_info_valid_index(parent, drc_index);

	/* Note that the format of the ibm,drc-indexes array is
	* the number of entries in the array followed by the array
	* of drc values so we start looking at index = 1.
	*/
	index = 1;
	while (!found) {
	u32 drc;

	rc = of_property_read_u32_index(parent, "ibm,drc-indexes",
	index++, &drc);

	if (rc)
	break;

	if (drc == drc_index)
	found = true;
	}

	return found;
	}

	static ssize_t dlpar_cpu_add(u32 drc_index)
	{
	struct device_node dn, parent;
	int rc, saved_rc;

	pr_debug("Attempting to add CPU, drc index: %x\n", drc_index);

	parent = of_find_node_by_path("/cpus");
	if (!parent) {
	pr_warn("Failed to find CPU root node \"/cpus\"\n");
	return -ENODEV;
	}

	if (dlpar_cpu_exists(parent, drc_index)) {
	of_node_put(parent);
	pr_warn("CPU with drc index %x already exists\n", drc_index);
	return -EINVAL;
	}

	if (!valid_cpu_drc_index(parent, drc_index)) {
	of_node_put(parent);
	pr_warn("Cannot find CPU (drc index %x) to add.\n", drc_index);
	return -EINVAL;
	}

	rc = dlpar_acquire_drc(drc_index);
	if (rc) {
	pr_warn("Failed to acquire DRC, rc: %d, drc index: %x\n",
	rc, drc_index);
	of_node_put(parent);
	return -EINVAL;
	}

	dn = dlpar_configure_connector(cpu_to_be32(drc_index), parent);
	if (!dn) {
	pr_warn("Failed call to configure-connector, drc index: %x\n",
	drc_index);
	dlpar_release_drc(drc_index);
	of_node_put(parent);
	return -EINVAL;
	}

	rc = dlpar_attach_node(dn, parent);

	/* Regardless we are done with parent now */
	of_node_put(parent);

	if (rc) {
	saved_rc = rc;
	pr_warn("Failed to attach node %pOFn, rc: %d, drc index: %x\n",
	dn, rc, drc_index);

	rc = dlpar_release_drc(drc_index);
	if (!rc)
	dlpar_free_cc_nodes(dn);

	return saved_rc;
	}

	rc = dlpar_online_cpu(dn);
	if (rc) {
	saved_rc = rc;
	pr_warn("Failed to online cpu %pOFn, rc: %d, drc index: %x\n",
	dn, rc, drc_index);

	rc = dlpar_detach_node(dn);
	if (!rc)
	dlpar_release_drc(drc_index);

	return saved_rc;
	}

	pr_debug("Successfully added CPU %pOFn, drc index: %x\n", dn,
	drc_index);
	return rc;
	}

	static ssize_t dlpar_cpu_remove(struct device_node *dn, u32 drc_index)
	{
	int rc;

	pr_debug("Attempting to remove CPU %pOFn, drc index: %x\n",
	dn, drc_index);

	rc = dlpar_offline_cpu(dn);
	if (rc) {
	pr_warn("Failed to offline CPU %pOFn, rc: %d\n", dn, rc);
	return -EINVAL;
	}

	rc = dlpar_release_drc(drc_index);
	if (rc) {
	pr_warn("Failed to release drc (%x) for CPU %pOFn, rc: %d\n",
	drc_index, dn, rc);
	dlpar_online_cpu(dn);
	return rc;
	}

	rc = dlpar_detach_node(dn);
	if (rc) {
	int saved_rc = rc;

	pr_warn("Failed to detach CPU %pOFn, rc: %d", dn, rc);

	rc = dlpar_acquire_drc(drc_index);
	if (!rc)
	dlpar_online_cpu(dn);

	return saved_rc;
	}

	pr_debug("Successfully removed CPU, drc index: %x\n", drc_index);
	return 0;
	}

	static struct device_node *cpu_drc_index_to_dn(u32 drc_index)
	{
	struct device_node *dn;
	u32 my_index;
	int rc;

	for_each_node_by_type(dn, "cpu") {
	rc = of_property_read_u32(dn, "ibm,my-drc-index", &my_index);
	if (rc)
	continue;

	if (my_index == drc_index)
	break;
	}

	return dn;
	}

	static int dlpar_cpu_remove_by_index(u32 drc_index)
	{
	struct device_node *dn;
	int rc;

	dn = cpu_drc_index_to_dn(drc_index);
	if (!dn) {
	pr_warn("Cannot find CPU (drc index %x) to remove\n",
	drc_index);
	return -ENODEV;
	}

	rc = dlpar_cpu_remove(dn, drc_index);
	of_node_put(dn);
	return rc;
	}

	static int find_dlpar_cpus_to_remove(u32 *cpu_drcs, int cpus_to_remove)
	{
	struct device_node *dn;
	int cpus_found = 0;
	int rc;

	/* We want to find cpus_to_remove + 1 CPUs to ensure we do not
	* remove the last CPU.
	*/
	for_each_node_by_type(dn, "cpu") {
	cpus_found++;

	if (cpus_found > cpus_to_remove) {
	of_node_put(dn);
	break;
	}

	/* Note that cpus_found is always 1 ahead of the index
	* into the cpu_drcs array, so we use cpus_found - 1
	*/
	rc = of_property_read_u32(dn, "ibm,my-drc-index",
	&cpu_drcs[cpus_found - 1]);
	if (rc) {
	pr_warn("Error occurred getting drc-index for %pOFn\n",
	dn);
	of_node_put(dn);
	return -1;
	}
	}

	if (cpus_found < cpus_to_remove) {
	pr_warn("Failed to find enough CPUs (%d of %d) to remove\n",
	cpus_found, cpus_to_remove);
	} else if (cpus_found == cpus_to_remove) {
	pr_warn("Cannot remove all CPUs\n");
	}

	return cpus_found;
	}

	static int dlpar_cpu_remove_by_count(u32 cpus_to_remove)
	{
	u32 *cpu_drcs;
	int cpus_found;
	int cpus_removed = 0;
	int i, rc;

	pr_debug("Attempting to hot-remove %d CPUs\n", cpus_to_remove);

	cpu_drcs = kcalloc(cpus_to_remove, sizeof(*cpu_drcs), GFP_KERNEL);
	if (!cpu_drcs)
	return -EINVAL;

	cpus_found = find_dlpar_cpus_to_remove(cpu_drcs, cpus_to_remove);
	if (cpus_found <= cpus_to_remove) {
	kfree(cpu_drcs);
	return -EINVAL;
	}

	for (i = 0; i < cpus_to_remove; i++) {
	rc = dlpar_cpu_remove_by_index(cpu_drcs[i]);
	if (rc)
	break;

	cpus_removed++;
	}

	if (cpus_removed != cpus_to_remove) {
	pr_warn("CPU hot-remove failed, adding back removed CPUs\n");

	for (i = 0; i < cpus_removed; i++)
	dlpar_cpu_add(cpu_drcs[i]);

	rc = -EINVAL;
	} else {
	rc = 0;
	}

	kfree(cpu_drcs);
	return rc;
	}

	static int find_drc_info_cpus_to_add(struct device_node *cpus,
	struct property *info,
	u32 *cpu_drcs, u32 cpus_to_add)
	{
	struct of_drc_info drc;
	const __be32 *value;
	u32 count, drc_index;
	int cpus_found = 0;
	int i, j;

	if (!info)
	return -1;

	value = of_prop_next_u32(info, NULL, &count);
	if (value)
	value++;

	for (i = 0; i < count; i++) {
	of_read_drc_info_cell(&info, &value, &drc);
	if (strncmp(drc.drc_type, "CPU", 3))
	break;

	drc_index = drc.drc_index_start;
	for (j = 0; j < drc.num_sequential_elems; j++) {
	if (dlpar_cpu_exists(cpus, drc_index))
	continue;

	cpu_drcs[cpus_found++] = drc_index;

	if (cpus_found == cpus_to_add)
	return cpus_found;

	drc_index += drc.sequential_inc;
	}
	}

	return cpus_found;
	}

	static int find_drc_index_cpus_to_add(struct device_node *cpus,
	u32 *cpu_drcs, u32 cpus_to_add)
	{
	int cpus_found = 0;
	int index, rc;
	u32 drc_index;

	/* Search the ibm,drc-indexes array for possible CPU drcs to
	* add. Note that the format of the ibm,drc-indexes array is
	* the number of entries in the array followed by the array
	* of drc values so we start looking at index = 1.
	*/
	index = 1;
	while (cpus_found < cpus_to_add) {
	rc = of_property_read_u32_index(cpus, "ibm,drc-indexes",
	index++, &drc_index);

	if (rc)
	break;

	if (dlpar_cpu_exists(cpus, drc_index))
	continue;

	cpu_drcs[cpus_found++] = drc_index;
	}

	return cpus_found;
	}

	static int dlpar_cpu_add_by_count(u32 cpus_to_add)
	{
	struct device_node *parent;
	struct property *info;
	u32 *cpu_drcs;
	int cpus_added = 0;
	int cpus_found;
	int i, rc;

	pr_debug("Attempting to hot-add %d CPUs\n", cpus_to_add);

	cpu_drcs = kcalloc(cpus_to_add, sizeof(*cpu_drcs), GFP_KERNEL);
	if (!cpu_drcs)
	return -EINVAL;

	parent = of_find_node_by_path("/cpus");
	if (!parent) {
	pr_warn("Could not find CPU root node in device tree\n");
	kfree(cpu_drcs);
	return -1;
	}

	info = of_find_property(parent, "ibm,drc-info", NULL);
	if (info)
	cpus_found = find_drc_info_cpus_to_add(parent, info, cpu_drcs, cpus_to_add);
	else
	cpus_found = find_drc_index_cpus_to_add(parent, cpu_drcs, cpus_to_add);

	of_node_put(parent);

	if (cpus_found < cpus_to_add) {
	pr_warn("Failed to find enough CPUs (%d of %d) to add\n",
	cpus_found, cpus_to_add);
	kfree(cpu_drcs);
	return -EINVAL;
	}

	for (i = 0; i < cpus_to_add; i++) {
	rc = dlpar_cpu_add(cpu_drcs[i]);
	if (rc)
	break;

	cpus_added++;
	}

	if (cpus_added < cpus_to_add) {
	pr_warn("CPU hot-add failed, removing any added CPUs\n");

	for (i = 0; i < cpus_added; i++)
	dlpar_cpu_remove_by_index(cpu_drcs[i]);

	rc = -EINVAL;
	} else {
	rc = 0;
	}

	kfree(cpu_drcs);
	return rc;
	}

	int dlpar_cpu(struct pseries_hp_errorlog *hp_elog)
	{
	u32 count, drc_index;
	int rc;

	count = hp_elog->_drc_u.drc_count;
	drc_index = hp_elog->_drc_u.drc_index;

	lock_device_hotplug();

	switch (hp_elog->action) {
	case PSERIES_HP_ELOG_ACTION_REMOVE:
	if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_COUNT)
	rc = dlpar_cpu_remove_by_count(count);
	else if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX)
	rc = dlpar_cpu_remove_by_index(drc_index);
	else
	rc = -EINVAL;
	break;
	case PSERIES_HP_ELOG_ACTION_ADD:
	if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_COUNT)
	rc = dlpar_cpu_add_by_count(count);
	else if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX)
	rc = dlpar_cpu_add(drc_index);
	else
	rc = -EINVAL;
	break;
	default:
	pr_err("Invalid action (%d) specified\n", hp_elog->action);
	rc = -EINVAL;
	break;
	}

	unlock_device_hotplug();
	return rc;
	}

	#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE

	static ssize_t dlpar_cpu_probe(const char *buf, size_t count)
	{
	u32 drc_index;
	int rc;

	rc = kstrtou32(buf, 0, &drc_index);
	if (rc)
	return -EINVAL;

	rc = dlpar_cpu_add(drc_index);

	return rc ? rc : count;
	}

	static ssize_t dlpar_cpu_release(const char *buf, size_t count)
	{
	struct device_node *dn;
	u32 drc_index;
	int rc;

	dn = of_find_node_by_path(buf);
	if (!dn)
	return -EINVAL;

	rc = of_property_read_u32(dn, "ibm,my-drc-index", &drc_index);
	if (rc) {
	of_node_put(dn);
	return -EINVAL;
	}

	rc = dlpar_cpu_remove(dn, drc_index);
	of_node_put(dn);

	return rc ? rc : count;
	}

	#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */

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

	switch (action) {
	case OF_RECONFIG_ATTACH_NODE:
	err = pseries_add_processor(rd->dn);
	break;
	case OF_RECONFIG_DETACH_NODE:
	pseries_remove_processor(rd->dn);
	break;
	}
	return notifier_from_errno(err);
	}

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

	static int __init pseries_cpu_hotplug_init(void)
	{
	int qcss_tok;

	#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
	ppc_md.cpu_probe = dlpar_cpu_probe;
	ppc_md.cpu_release = dlpar_cpu_release;
	#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */

	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;
	}

	smp_ops->cpu_offline_self = pseries_cpu_offline_self;
	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);

	return 0;
	}
	machine_arch_initcall(pseries, pseries_cpu_hotplug_init);