Adding upstream version 6.1.76.upstream/6.1.76

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

1 files changed, 888 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
new file mode 100644
index 000000000..e0a7ac5db
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -0,0 +1,888 @@
+// 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;
+
+/*
+ * Record the CPU ids used on each nodes.
+ * Protected by cpu_add_remove_lock.
+ */
+static cpumask_var_t node_recorded_ids_map[MAX_NUMNODES];
+
+static void rtas_stop_self(void)
+{
+	static struct rtas_args args;
+
+	local_irq_disable();
+
+	BUG_ON(rtas_stop_self_token == RTAS_UNKNOWN_SERVICE);
+
+	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);
+	}
+
+	paca_ptrs[cpu]->cpu_start = 0;
+}
+
+/**
+ * find_cpu_id_range - found a linear ranger of @nthreads free CPU ids.
+ * @nthreads : the number of threads (cpu ids)
+ * @assigned_node : the node it belongs to or NUMA_NO_NODE if free ids from any
+ *                  node can be peek.
+ * @cpu_mask: the returned CPU mask.
+ *
+ * Returns 0 on success.
+ */
+static int find_cpu_id_range(unsigned int nthreads, int assigned_node,
+			     cpumask_var_t *cpu_mask)
+{
+	cpumask_var_t candidate_mask;
+	unsigned int cpu, node;
+	int rc = -ENOSPC;
+
+	if (!zalloc_cpumask_var(&candidate_mask, GFP_KERNEL))
+		return -ENOMEM;
+
+	cpumask_clear(*cpu_mask);
+	for (cpu = 0; cpu < nthreads; cpu++)
+		cpumask_set_cpu(cpu, *cpu_mask);
+
+	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 (assigned_node != NUMA_NO_NODE) {
+		/*
+		 * Remove free ids previously assigned on the other nodes. We
+		 * can walk only online nodes because once a node became online
+		 * it is not turned offlined back.
+		 */
+		for_each_online_node(node) {
+			if (node == assigned_node)
+				continue;
+			cpumask_andnot(candidate_mask, candidate_mask,
+				       node_recorded_ids_map[node]);
+		}
+	}
+
+	if (cpumask_empty(candidate_mask))
+		goto out;
+
+	while (!cpumask_empty(*cpu_mask)) {
+		if (cpumask_subset(*cpu_mask, candidate_mask))
+			/* Found a range where we can insert the new cpu(s) */
+			break;
+		cpumask_shift_left(*cpu_mask, *cpu_mask, nthreads);
+	}
+
+	if (!cpumask_empty(*cpu_mask))
+		rc = 0;
+
+out:
+	free_cpumask_var(candidate_mask);
+	return rc;
+}
+
+/*
+ * Update cpu_present_mask and paca(s) for a new cpu node.  The wrinkle
+ * here is that a cpu device node may represent multiple 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)
+{
+	int len, nthreads, node, cpu, assigned_node;
+	int rc = 0;
+	cpumask_var_t cpu_mask;
+	const __be32 *intserv;
+
+	intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
+	if (!intserv)
+		return 0;
+
+	nthreads = len / sizeof(u32);
+
+	if (!alloc_cpumask_var(&cpu_mask, GFP_KERNEL))
+		return -ENOMEM;
+
+	/*
+	 * Fetch from the DT nodes read by dlpar_configure_connector() the NUMA
+	 * node id the added CPU belongs to.
+	 */
+	node = of_node_to_nid(np);
+	if (node < 0 || !node_possible(node))
+		node = first_online_node;
+
+	BUG_ON(node == NUMA_NO_NODE);
+	assigned_node = node;
+
+	cpu_maps_update_begin();
+
+	rc = find_cpu_id_range(nthreads, node, &cpu_mask);
+	if (rc && nr_node_ids > 1) {
+		/*
+		 * Try again, considering the free CPU ids from the other node.
+		 */
+		node = NUMA_NO_NODE;
+		rc = find_cpu_id_range(nthreads, NUMA_NO_NODE, &cpu_mask);
+	}
+
+	if (rc) {
+		pr_err("Cannot add cpu %pOF; this system configuration"
+		       " supports %d logical cpus.\n", np, num_possible_cpus());
+		goto out;
+	}
+
+	for_each_cpu(cpu, cpu_mask) {
+		BUG_ON(cpu_present(cpu));
+		set_cpu_present(cpu, true);
+		set_hard_smp_processor_id(cpu, be32_to_cpu(*intserv++));
+	}
+
+	/* Record the newly used CPU ids for the associate node. */
+	cpumask_or(node_recorded_ids_map[assigned_node],
+		   node_recorded_ids_map[assigned_node], cpu_mask);
+
+	/*
+	 * If node is set to NUMA_NO_NODE, CPU ids have be reused from
+	 * another node, remove them from its mask.
+	 */
+	if (node == NUMA_NO_NODE) {
+		cpu = cpumask_first(cpu_mask);
+		pr_warn("Reusing free CPU ids %d-%d from another node\n",
+			cpu, cpu + nthreads - 1);
+		for_each_online_node(node) {
+			if (node == assigned_node)
+				continue;
+			cpumask_andnot(node_recorded_ids_map[node],
+				       node_recorded_ids_map[node],
+				       cpu_mask);
+		}
+	}
+
+out:
+	cpu_maps_update_done();
+	free_cpumask_var(cpu_mask);
+	return rc;
+}
+
+/*
+ * 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;
+
+			/*
+			 * device_offline() will return -EBUSY (via cpu_down()) if there
+			 * is only one CPU left. Check it here to fail earlier and with a
+			 * more informative error message, while also retaining the
+			 * cpu_add_remove_lock to be sure that no CPUs are being
+			 * online/offlined during this check.
+			 */
+			if (num_online_cpus() == 1) {
+				pr_warn("Unable to remove last online CPU %pOFn\n", dn);
+				rc = -EBUSY;
+				goto out_unlock;
+			}
+
+			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);
+		}
+	}
+out_unlock:
+	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_update_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 int pseries_cpuhp_attach_nodes(struct device_node *dn)
+{
+	struct of_changeset cs;
+	int ret;
+
+	/*
+	 * This device node is unattached but may have siblings; open-code the
+	 * traversal.
+	 */
+	for (of_changeset_init(&cs); dn != NULL; dn = dn->sibling) {
+		ret = of_changeset_attach_node(&cs, dn);
+		if (ret)
+			goto out;
+	}
+
+	ret = of_changeset_apply(&cs);
+out:
+	of_changeset_destroy(&cs);
+	return ret;
+}
+
+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 = pseries_cpuhp_attach_nodes(dn);
+
+	/* 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;
+	}
+
+	update_numa_distance(dn);
+
+	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 unsigned int pseries_cpuhp_cache_use_count(const struct device_node *cachedn)
+{
+	unsigned int use_count = 0;
+	struct device_node *dn, *tn;
+
+	WARN_ON(!of_node_is_type(cachedn, "cache"));
+
+	for_each_of_cpu_node(dn) {
+		tn = of_find_next_cache_node(dn);
+		of_node_put(tn);
+		if (tn == cachedn)
+			use_count++;
+	}
+
+	for_each_node_by_type(dn, "cache") {
+		tn = of_find_next_cache_node(dn);
+		of_node_put(tn);
+		if (tn == cachedn)
+			use_count++;
+	}
+
+	return use_count;
+}
+
+static int pseries_cpuhp_detach_nodes(struct device_node *cpudn)
+{
+	struct device_node *dn;
+	struct of_changeset cs;
+	int ret = 0;
+
+	of_changeset_init(&cs);
+	ret = of_changeset_detach_node(&cs, cpudn);
+	if (ret)
+		goto out;
+
+	dn = cpudn;
+	while ((dn = of_find_next_cache_node(dn))) {
+		if (pseries_cpuhp_cache_use_count(dn) > 1) {
+			of_node_put(dn);
+			break;
+		}
+
+		ret = of_changeset_detach_node(&cs, dn);
+		of_node_put(dn);
+		if (ret)
+			goto out;
+	}
+
+	ret = of_changeset_apply(&cs);
+out:
+	of_changeset_destroy(&cs);
+	return ret;
+}
+
+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 = pseries_cpuhp_detach_nodes(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;
+}
+
+int dlpar_cpu(struct pseries_hp_errorlog *hp_elog)
+{
+	u32 drc_index;
+	int rc;
+
+	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_INDEX) {
+			rc = dlpar_cpu_remove_by_index(drc_index);
+			/*
+			 * Setting the isolation state of an UNISOLATED/CONFIGURED
+			 * device to UNISOLATE is a no-op, but the hypervisor can
+			 * use it as a hint that the CPU removal failed.
+			 */
+			if (rc)
+				dlpar_unisolate_drc(drc_index);
+		}
+		else
+			rc = -EINVAL;
+		break;
+	case PSERIES_HP_ELOG_ACTION_ADD:
+		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;
+	unsigned int node;
+
+#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)) {
+		for_each_node(node) {
+			if (!alloc_cpumask_var_node(&node_recorded_ids_map[node],
+						    GFP_KERNEL, node))
+				return -ENOMEM;
+
+			/* Record ids of CPU added at boot time */
+			cpumask_copy(node_recorded_ids_map[node],
+				     cpumask_of_node(node));
+		}
+
+		of_reconfig_notifier_register(&pseries_smp_nb);
+	}
+
+	return 0;
+}
+machine_arch_initcall(pseries, pseries_cpu_hotplug_init);