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Release 4.14 arch/powerpc/perf/imc-pmu.c

Directory: arch/powerpc/perf
/*
 * In-Memory Collection (IMC) Performance Monitor counter support.
 *
 * Copyright (C) 2017 Madhavan Srinivasan, IBM Corporation.
 *           (C) 2017 Anju T Sudhakar, IBM Corporation.
 *           (C) 2017 Hemant K Shaw, IBM Corporation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or later version.
 */
#include <linux/perf_event.h>
#include <linux/slab.h>
#include <asm/opal.h>
#include <asm/imc-pmu.h>
#include <asm/cputhreads.h>
#include <asm/smp.h>
#include <linux/string.h>

/* Nest IMC data structures and variables */

/*
 * Used to avoid races in counting the nest-pmu units during hotplug
 * register and unregister
 */
static DEFINE_MUTEX(nest_init_lock);
static DEFINE_PER_CPU(struct imc_pmu_ref *, local_nest_imc_refc);

static struct imc_pmu *per_nest_pmu_arr[IMC_MAX_PMUS];

static cpumask_t nest_imc_cpumask;

struct imc_pmu_ref *nest_imc_refc;

static int nest_pmus;

/* Core IMC data structures and variables */


static cpumask_t core_imc_cpumask;

struct imc_pmu_ref *core_imc_refc;

static struct imc_pmu *core_imc_pmu;

/* Thread IMC data structures and variables */

static DEFINE_PER_CPU(u64 *, thread_imc_mem);

static struct imc_pmu *thread_imc_pmu;

static int thread_imc_mem_size;




struct imc_pmu *imc_event_to_pmu(struct perf_event *event)
{
	return container_of(event->pmu, struct imc_pmu, pmu);
}


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PMU_FORMAT_ATTR(event, "config:0-40");
PMU_FORMAT_ATTR(offset, "config:0-31");
PMU_FORMAT_ATTR(rvalue, "config:32");
PMU_FORMAT_ATTR(mode, "config:33-40");

static struct attribute *imc_format_attrs[] = {
	&format_attr_event.attr,
	&format_attr_offset.attr,
	&format_attr_rvalue.attr,
	&format_attr_mode.attr,
	NULL,
};


static struct attribute_group imc_format_group = {
	.name = "format",
	.attrs = imc_format_attrs,
};

/* Get the cpumask printed to a buffer "buf" */



static ssize_t imc_pmu_cpumask_get_attr(struct device *dev,
					struct device_attribute *attr,
					char *buf)
{
	struct pmu *pmu = dev_get_drvdata(dev);
	struct imc_pmu *imc_pmu = container_of(pmu, struct imc_pmu, pmu);
	cpumask_t *active_mask;

	switch(imc_pmu->domain){
	case IMC_DOMAIN_NEST:
		active_mask = &nest_imc_cpumask;
		break;
	case IMC_DOMAIN_CORE:
		active_mask = &core_imc_cpumask;
		break;
	default:
		return 0;
	}

	return cpumap_print_to_pagebuf(true, buf, active_mask);
}


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static DEVICE_ATTR(cpumask, S_IRUGO, imc_pmu_cpumask_get_attr, NULL);


static struct attribute *imc_pmu_cpumask_attrs[] = {
	&dev_attr_cpumask.attr,
	NULL,
};


static struct attribute_group imc_pmu_cpumask_attr_group = {
	.attrs = imc_pmu_cpumask_attrs,
};

/* device_str_attr_create : Populate event "name" and string "str" in attribute */



static struct attribute *device_str_attr_create(const char *name, const char *str)
{
	struct perf_pmu_events_attr *attr;

	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
	if (!attr)
		return NULL;
	sysfs_attr_init(&attr->attr.attr);

	attr->event_str = str;
	attr->attr.attr.name = name;
	attr->attr.attr.mode = 0444;
	attr->attr.show = perf_event_sysfs_show;

	return &attr->attr.attr;
}


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struct imc_events *imc_parse_event(struct device_node *np, const char *scale,
				  const char *unit, const char *prefix, u32 base)
{
	struct imc_events *event;
	const char *s;
	u32 reg;

	event = kzalloc(sizeof(struct imc_events), GFP_KERNEL);
	if (!event)
		return NULL;

	if (of_property_read_u32(np, "reg", &reg))
		goto error;
	/* Add the base_reg value to the "reg" */
	event->value = base + reg;

	if (of_property_read_string(np, "event-name", &s))
		goto error;

	event->name = kasprintf(GFP_KERNEL, "%s%s", prefix, s);
	if (!event->name)
		goto error;

	if (of_property_read_string(np, "scale", &s))
		s = scale;

	if (s) {
		event->scale = kstrdup(s, GFP_KERNEL);
		if (!event->scale)
			goto error;
	}

	if (of_property_read_string(np, "unit", &s))
		s = unit;

	if (s) {
		event->unit = kstrdup(s, GFP_KERNEL);
		if (!event->unit)
			goto error;
	}

	return event;
error:
	kfree(event->unit);
	kfree(event->scale);
	kfree(event->name);
	kfree(event);

	return NULL;
}


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/*
 * update_events_in_group: Update the "events" information in an attr_group
 *                         and assign the attr_group to the pmu "pmu".
 */



static int update_events_in_group(struct device_node *node, struct imc_pmu *pmu)
{
	struct attribute_group *attr_group;
	struct attribute **attrs, *dev_str;
	struct device_node *np, *pmu_events;
	struct imc_events *ev;
	u32 handle, base_reg;
	int i=0, j=0, ct;
	const char *prefix, *g_scale, *g_unit;
	const char *ev_val_str, *ev_scale_str, *ev_unit_str;

	if (!of_property_read_u32(node, "events", &handle))
		pmu_events = of_find_node_by_phandle(handle);
	else
		return 0;

	/* Did not find any node with a given phandle */
	if (!pmu_events)
		return 0;

	/* Get a count of number of child nodes */
	ct = of_get_child_count(pmu_events);

	/* Get the event prefix */
	if (of_property_read_string(node, "events-prefix", &prefix))
		return 0;

	/* Get a global unit and scale data if available */
	if (of_property_read_string(node, "scale", &g_scale))
		g_scale = NULL;

	if (of_property_read_string(node, "unit", &g_unit))
		g_unit = NULL;

	/* "reg" property gives out the base offset of the counters data */
	of_property_read_u32(node, "reg", &base_reg);

	/* Allocate memory for the events */
	pmu->events = kcalloc(ct, sizeof(struct imc_events), GFP_KERNEL);
	if (!pmu->events)
		return -ENOMEM;

	ct = 0;
	/* Parse the events and update the struct */
	for_each_child_of_node(pmu_events, np) {
		ev = imc_parse_event(np, g_scale, g_unit, prefix, base_reg);
		if (ev)
			pmu->events[ct++] = ev;
	}

	/* Allocate memory for attribute group */
	attr_group = kzalloc(sizeof(*attr_group), GFP_KERNEL);
	if (!attr_group)
		return -ENOMEM;

	/*
         * Allocate memory for attributes.
         * Since we have count of events for this pmu, we also allocate
         * memory for the scale and unit attribute for now.
         * "ct" has the total event structs added from the events-parent node.
         * So allocate three times the "ct" (this includes event, event_scale and
         * event_unit).
         */
	attrs = kcalloc(((ct * 3) + 1), sizeof(struct attribute *), GFP_KERNEL);
	if (!attrs) {
		kfree(attr_group);
		kfree(pmu->events);
		return -ENOMEM;
	}

	attr_group->name = "events";
	attr_group->attrs = attrs;
	do {
		ev_val_str = kasprintf(GFP_KERNEL, "event=0x%x", pmu->events[i]->value);
		dev_str = device_str_attr_create(pmu->events[i]->name, ev_val_str);
		if (!dev_str)
			continue;

		attrs[j++] = dev_str;
		if (pmu->events[i]->scale) {
			ev_scale_str = kasprintf(GFP_KERNEL, "%s.scale",pmu->events[i]->name);
			dev_str = device_str_attr_create(ev_scale_str, pmu->events[i]->scale);
			if (!dev_str)
				continue;

			attrs[j++] = dev_str;
		}

		if (pmu->events[i]->unit) {
			ev_unit_str = kasprintf(GFP_KERNEL, "%s.unit",pmu->events[i]->name);
			dev_str = device_str_attr_create(ev_unit_str, pmu->events[i]->unit);
			if (!dev_str)
				continue;

			attrs[j++] = dev_str;
		}
	} while (++i < ct);

	/* Save the event attribute */
	pmu->attr_groups[IMC_EVENT_ATTR] = attr_group;

	kfree(pmu->events);
	return 0;
}


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/* get_nest_pmu_ref: Return the imc_pmu_ref struct for the given node */



static struct imc_pmu_ref *get_nest_pmu_ref(int cpu)
{
	return per_cpu(local_nest_imc_refc, cpu);
}


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static void nest_change_cpu_context(int old_cpu, int new_cpu)
{
	struct imc_pmu **pn = per_nest_pmu_arr;
	int i;

	if (old_cpu < 0 || new_cpu < 0)
		return;

	for (i = 0; *pn && i < IMC_MAX_PMUS; i++, pn++)
		perf_pmu_migrate_context(&(*pn)->pmu, old_cpu, new_cpu);
}


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static int ppc_nest_imc_cpu_offline(unsigned int cpu)
{
	int nid, target = -1;
	const struct cpumask *l_cpumask;
	struct imc_pmu_ref *ref;

	/*
         * Check in the designated list for this cpu. Dont bother
         * if not one of them.
         */
	if (!cpumask_test_and_clear_cpu(cpu, &nest_imc_cpumask))
		return 0;

	/*
         * Now that this cpu is one of the designated,
         * find a next cpu a) which is online and b) in same chip.
         */
	nid = cpu_to_node(cpu);
	l_cpumask = cpumask_of_node(nid);
	target = cpumask_any_but(l_cpumask, cpu);

	/*
         * Update the cpumask with the target cpu and
         * migrate the context if needed
         */
	if (target >= 0 && target < nr_cpu_ids) {
		cpumask_set_cpu(target, &nest_imc_cpumask);
		nest_change_cpu_context(cpu, target);
	} else {
		opal_imc_counters_stop(OPAL_IMC_COUNTERS_NEST,
				       get_hard_smp_processor_id(cpu));
		/*
                 * If this is the last cpu in this chip then, skip the reference
                 * count mutex lock and make the reference count on this chip zero.
                 */
		ref = get_nest_pmu_ref(cpu);
		if (!ref)
			return -EINVAL;

		ref->refc = 0;
	}
	return 0;
}


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static int ppc_nest_imc_cpu_online(unsigned int cpu)
{
	const struct cpumask *l_cpumask;
	static struct cpumask tmp_mask;
	int res;

	/* Get the cpumask of this node */
	l_cpumask = cpumask_of_node(cpu_to_node(cpu));

	/*
         * If this is not the first online CPU on this node, then
         * just return.
         */
	if (cpumask_and(&tmp_mask, l_cpumask, &nest_imc_cpumask))
		return 0;

	/*
         * If this is the first online cpu on this node
         * disable the nest counters by making an OPAL call.
         */
	res = opal_imc_counters_stop(OPAL_IMC_COUNTERS_NEST,
				     get_hard_smp_processor_id(cpu));
	if (res)
		return res;

	/* Make this CPU the designated target for counter collection */
	cpumask_set_cpu(cpu, &nest_imc_cpumask);
	return 0;
}


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static int nest_pmu_cpumask_init(void)
{
	return cpuhp_setup_state(CPUHP_AP_PERF_POWERPC_NEST_IMC_ONLINE,
				 "perf/powerpc/imc:online",
				 ppc_nest_imc_cpu_online,
				 ppc_nest_imc_cpu_offline);
}


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static void nest_imc_counters_release(struct perf_event *event)
{
	int rc, node_id;
	struct imc_pmu_ref *ref;

	if (event->cpu < 0)
		return;

	node_id = cpu_to_node(event->cpu);

	/*
         * See if we need to disable the nest PMU.
         * If no events are currently in use, then we have to take a
         * mutex to ensure that we don't race with another task doing
         * enable or disable the nest counters.
         */
	ref = get_nest_pmu_ref(event->cpu);
	if (!ref)
		return;

	/* Take the mutex lock for this node and then decrement the reference count */
	mutex_lock(&ref->lock);
	if (ref->refc == 0) {
		/*
                 * The scenario where this is true is, when perf session is
                 * started, followed by offlining of all cpus in a given node.
                 *
                 * In the cpuhotplug offline path, ppc_nest_imc_cpu_offline()
                 * function set the ref->count to zero, if the cpu which is
                 * about to offline is the last cpu in a given node and make
                 * an OPAL call to disable the engine in that node.
                 *
                 */
		mutex_unlock(&ref->lock);
		return;
	}
	ref->refc--;
	if (ref->refc == 0) {
		rc = opal_imc_counters_stop(OPAL_IMC_COUNTERS_NEST,
					    get_hard_smp_processor_id(event->cpu));
		if (rc) {
			mutex_unlock(&ref->lock);
			pr_err("nest-imc: Unable to stop the counters for core %d\n", node_id);
			return;
		}
	} else if (ref->refc < 0) {
		WARN(1, "nest-imc: Invalid event reference count\n");
		ref->refc = 0;
	}
	mutex_unlock(&ref->lock);
}


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static int nest_imc_event_init(struct perf_event *event)
{
	int chip_id, rc, node_id;
	u32 l_config, config = event->attr.config;
	struct imc_mem_info *pcni;
	struct imc_pmu *pmu;
	struct imc_pmu_ref *ref;
	bool flag = false;

	if (event->attr.type != event->pmu->type)
		return -ENOENT;

	/* Sampling not supported */
	if (event->hw.sample_period)
		return -EINVAL;

	/* unsupported modes and filters */
	if (event->attr.exclude_user   ||
	    event->attr.exclude_kernel ||
	    event->attr.exclude_hv     ||
	    event->attr.exclude_idle   ||
	    event->attr.exclude_host   ||
	    event->attr.exclude_guest)
		return -EINVAL;

	if (event->cpu < 0)
		return -EINVAL;

	pmu = imc_event_to_pmu(event);

	/* Sanity check for config (event offset) */
	if ((config & IMC_EVENT_OFFSET_MASK) > pmu->counter_mem_size)
		return -EINVAL;

	/*
         * Nest HW counter memory resides in a per-chip reserve-memory (HOMER).
         * Get the base memory addresss for this cpu.
         */
	chip_id = topology_physical_package_id(event->cpu);
	pcni = pmu->mem_info;
	do {
		if (pcni->id == chip_id) {
			flag = true;
			break;
		}
		pcni++;
	} while (pcni);

	if (!flag)
		return -ENODEV;

	/*
         * Add the event offset to the base address.
         */
	l_config = config & IMC_EVENT_OFFSET_MASK;
	event->hw.event_base = (u64)pcni->vbase + l_config;
	node_id = cpu_to_node(event->cpu);

	/*
         * Get the imc_pmu_ref struct for this node.
         * Take the mutex lock and then increment the count of nest pmu events
         * inited.
         */
	ref = get_nest_pmu_ref(event->cpu);
	if (!ref)
		return -EINVAL;

	mutex_lock(&ref->lock);
	if (ref->refc == 0) {
		rc = opal_imc_counters_start(OPAL_IMC_COUNTERS_NEST,
					     get_hard_smp_processor_id(event->cpu));
		if (rc) {
			mutex_unlock(&ref->lock);
			pr_err("nest-imc: Unable to start the counters for node %d\n",
									node_id);
			return rc;
		}
	}
	++ref->refc;
	mutex_unlock(&ref->lock);

	event->destroy = nest_imc_counters_release;
	return 0;
}


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/*
 * core_imc_mem_init : Initializes memory for the current core.
 *
 * Uses alloc_pages_node() and uses the returned address as an argument to
 * an opal call to configure the pdbar. The address sent as an argument is
 * converted to physical address before the opal call is made. This is the
 * base address at which the core imc counters are populated.
 */



static int core_imc_mem_init(int cpu, int size)
{
	int phys_id, rc = 0, core_id = (cpu / threads_per_core);
	struct imc_mem_info *mem_info;

	/*
         * alloc_pages_node() will allocate memory for core in the
         * local node only.
         */
	phys_id = topology_physical_package_id(cpu);
	mem_info = &core_imc_pmu->mem_info[core_id];
	mem_info->id = core_id;

	/* We need only vbase for core counters */
	mem_info->vbase = page_address(alloc_pages_node(phys_id,
					  GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE |
					  __GFP_NOWARN, get_order(size)));
	if (!mem_info->vbase)
		return -ENOMEM;

	/* Init the mutex */
	core_imc_refc[core_id].id = core_id;
	mutex_init(&core_imc_refc[core_id].lock);

	rc = opal_imc_counters_init(OPAL_IMC_COUNTERS_CORE,
				__pa((void *)mem_info->vbase),
				get_hard_smp_processor_id(cpu));
	if (rc) {
		free_pages((u64)mem_info->vbase, get_order(size));
		mem_info->vbase = NULL;
	}

	return rc;
}


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static bool is_core_imc_mem_inited(int cpu)
{
	struct imc_mem_info *mem_info;
	int core_id = (cpu / threads_per_core);

	mem_info = &core_imc_pmu->mem_info[core_id];
	if (!mem_info->vbase)
		return false;

	return true;
}


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static int ppc_core_imc_cpu_online(unsigned int cpu)
{
	const struct cpumask *l_cpumask;
	static struct cpumask tmp_mask;
	int ret = 0;

	/* Get the cpumask for this core */
	l_cpumask = cpu_sibling_mask(cpu);

	/* If a cpu for this core is already set, then, don't do anything */
	if (cpumask_and(&tmp_mask, l_cpumask, &core_imc_cpumask))
		return 0;

	if (!is_core_imc_mem_inited(cpu)) {
		ret = core_imc_mem_init(cpu, core_imc_pmu->counter_mem_size);
		if (ret) {
			pr_info("core_imc memory allocation for cpu %d failed\n", cpu);
			return ret;
		}
	}

	/* set the cpu in the mask */
	cpumask_set_cpu(cpu, &core_imc_cpumask);
	return 0;
}


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static int ppc_core_imc_cpu_offline(unsigned int cpu)
{
	unsigned int ncpu, core_id;
	struct imc_pmu_ref *ref;

	/*
         * clear this cpu out of the mask, if not present in the mask,
         * don't bother doing anything.
         */
	if (!cpumask_test_and_clear_cpu(cpu, &core_imc_cpumask))
		return 0;

	/*
         * Check whether core_imc is registered. We could end up here
         * if the cpuhotplug callback registration fails. i.e, callback
         * invokes the offline path for all sucessfully registered cpus.
         * At this stage, core_imc pmu will not be registered and we
         * should return here.
         *
         * We return with a zero since this is not an offline failure.
         * And cpuhp_setup_state() returns the actual failure reason
         * to the caller, which inturn will call the cleanup routine.
         */
	if (!core_imc_pmu->pmu.event_init)
		return 0;

	/* Find any online cpu in that core except the current "cpu" */
	ncpu = cpumask_any_but(cpu_sibling_mask(cpu), cpu);

	if (ncpu >= 0 && ncpu < nr_cpu_ids) {
		cpumask_set_cpu(ncpu, &core_imc_cpumask);
		perf_pmu_migrate_context(&core_imc_pmu->pmu, cpu, ncpu);
	} else {
		/*
                 * If this is the last cpu in this core then, skip taking refernce
                 * count mutex lock for this core and directly zero "refc" for
                 * this core.
                 */
		opal_imc_counters_stop(OPAL_IMC_COUNTERS_CORE,
				       get_hard_smp_processor_id(cpu));
		core_id = cpu / threads_per_core;
		ref = &core_imc_refc[core_id];
		if (!ref)
			return -EINVAL;

		ref->refc = 0;
	}
	return 0;
}


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static int core_imc_pmu_cpumask_init(void)
{
	return cpuhp_setup_state(CPUHP_AP_PERF_POWERPC_CORE_IMC_ONLINE,
				 "perf/powerpc/imc_core:online",
				 ppc_core_imc_cpu_online,
				 ppc_core_imc_cpu_offline);
}


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static void core_imc_counters_release(struct perf_event *event)
{
	int rc, core_id;
	struct imc_pmu_ref *ref;

	if (event->cpu < 0)
		return;
	/*
         * See if we need to disable the IMC PMU.
         * If no events are currently in use, then we have to take a
         * mutex to ensure that we don't race with another task doing
         * enable or disable the core counters.
         */
	core_id = event->cpu / threads_per_core;

	/* Take the mutex lock and decrement the refernce count for this core */
	ref = &core_imc_refc[core_id];
	if (!ref)
		return;

	mutex_lock(&ref->lock);
	if (ref->refc == 0) {
		/*
                 * The scenario where this is true is, when perf session is
                 * started, followed by offlining of all cpus in a given core.
                 *
                 * In the cpuhotplug offline path, ppc_core_imc_cpu_offline()
                 * function set the ref->count to zero, if the cpu which is
                 * about to offline is the last cpu in a given core and make
                 * an OPAL call to disable the engine in that core.
                 *
                 */
		mutex_unlock(&ref->lock);
		return;
	}
	ref->refc--;
	if (ref->refc == 0) {
		rc = opal_imc_counters_stop(OPAL_IMC_COUNTERS_CORE,
					    get_hard_smp_processor_id(event->cpu));
		if (rc) {
			mutex_unlock(&ref->lock);
			pr_err("IMC: Unable to stop the counters for core %d\n", core_id);
			return;
		}
	} else if (ref->refc < 0) {
		WARN(1, "core-imc: Invalid event reference count\n");
		ref->refc = 0;
	}
	mutex_unlock(&ref->lock);
}


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static int core_imc_event_init(struct perf_event *event)
{
	int core_id, rc;
	u64 config = event->attr.config;
	struct imc_mem_info *pcmi;
	struct imc_pmu *pmu;
	struct imc_pmu_ref *ref;

	if (event->attr.type != event->pmu->type)
		return -ENOENT;

	/* Sampling not supported */
	if (event->hw.sample_period)
		return -EINVAL;

	/* unsupported modes and filters */
	if (event->attr.exclude_user   ||
	    event->attr.exclude_kernel ||
	    event->attr.exclude_hv     ||
	    event->attr.exclude_idle   ||
	    event->attr.exclude_host   ||
	    event->attr.exclude_guest)
		return -EINVAL;

	if (event->cpu < 0)
		return -EINVAL;

	event->hw.idx = -1;
	pmu = imc_event_to_pmu(event);

	/* Sanity check for config (event offset) */
	if (((config & IMC_EVENT_OFFSET_MASK) > pmu->counter_mem_size))
		return -EINVAL;

	if (!is_core_imc_mem_inited(event->cpu))
		return -ENODEV;

	core_id = event->cpu / threads_per_core;
	pcmi = &core_imc_pmu->mem_info[core_id];
	if ((!pcmi->vbase))
		return -ENODEV;

	/* Get the core_imc mutex for this core */
	ref = &core_imc_refc[core_id];
	if (!ref)
		return -EINVAL;

	/*
         * Core pmu units are enabled only when it is used.
         * See if this is triggered for the first time.
         * If yes, take the mutex lock and enable the core counters.
         * If not, just increment the count in core_imc_refc struct.
         */
	mutex_lock(&ref->lock);
	if (ref->refc == 0) {
		rc = opal_imc_counters_start(OPAL_IMC_COUNTERS_CORE,
					     get_hard_smp_processor_id(event->cpu));
		if (rc) {
			mutex_unlock(&ref->lock);
			pr_err("core-imc: Unable to start the counters for core %d\n",
									core_id);
			return rc;
		}
	}
	++ref->refc;
	mutex_unlock(&ref->lock);

	event->hw.event_base = (u64)pcmi->vbase + (config & IMC_EVENT_OFFSET_MASK);
	event->destroy = core_imc_counters_release;
	return 0;
}


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/*
 * Allocates a page of memory for each of the online cpus, and write the
 * physical base address of that page to the LDBAR for that cpu.
 *
 * LDBAR Register Layout:
 *
 *  0          4         8         12        16        20        24        28
 * | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - |
 *   | |       [   ]    [                   Counter Address [8:50]
 *   | * Mode    |
 *   |           * PB Scope
 *   * Enable/Disable
 *
 *  32        36        40        44        48        52        56        60
 * | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - |
 *           Counter Address [8:50]              ]
 *
 */



static int thread_imc_mem_alloc(int cpu_id, int size)
{
	u64 ldbar_value, *local_mem = per_cpu(thread_imc_mem, cpu_id);
	int phys_id = topology_physical_package_id(cpu_id);

	if (!local_mem) {
		/*
                 * This case could happen only once at start, since we dont
                 * free the memory in cpu offline path.
                 */
		local_mem = page_address(alloc_pages_node(phys_id,
				  GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE |
				  __GFP_NOWARN, get_order(size)));
		if (!local_mem)
			return -ENOMEM;

		per_cpu(thread_imc_mem, cpu_id) = local_mem;
	}

	ldbar_value = ((u64)local_mem & THREAD_IMC_LDBAR_MASK) | THREAD_IMC_ENABLE;

	mtspr(SPRN_LDBAR, ldbar_value);
	return 0;
}


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static int ppc_thread_imc_cpu_online(unsigned int cpu)
{
	return thread_imc_mem_alloc(cpu, thread_imc_mem_size);
}


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static int ppc_thread_imc_cpu_offline(unsigned int cpu)
{
	mtspr(SPRN_LDBAR, 0);
	return 0;
}


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static int