[S390] perf: add support for s390x CPU counters

Add a perf PMU to access the CPU-measurement counter facility CPUM CF.
CPUM CF provides multiple counter sets for measuring generic,
problem-state, and crypto activaties.  Also an extended counter set for
the IBM System z10 and IBM z196 mainframes is available.

Counters from the basic and problem-state counter set are mapped to
generic perf hardware events.  Other counters are accessible through
raw events.

For a list of available counter sets and counters, see:

  - The Load-Program-Parameter and the CPU-Measurement Facilities (SA23-2260)
  - The CPU-Measurement Facility Extended Counters Definition for
    z10 and z196 (SA23-2261)

Reviewed-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 690 insertions, 0 deletions

diff --git a/arch/s390/kernel/perf_cpum_cf.c b/arch/s390/kernel/perf_cpum_cf.c
new file mode 100644
index 000000000000..8481ecf2ad71
--- /dev/null
+++ b/arch/s390/kernel/perf_cpum_cf.c
@@ -0,0 +1,690 @@
+/*
+ * Performance event support for s390x - CPU-measurement Counter Facility
+ *
+ *  Copyright IBM Corp. 2012
+ *  Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License (version 2 only)
+ * as published by the Free Software Foundation.
+ */
+#define KMSG_COMPONENT	"cpum_cf"
+#define pr_fmt(fmt)	KMSG_COMPONENT ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/kernel_stat.h>
+#include <linux/perf_event.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/init.h>
+#include <linux/export.h>
+#include <asm/system.h>
+#include <asm/irq.h>
+#include <asm/cpu_mf.h>
+
+/* CPU-measurement counter facility supports these CPU counter sets:
+ * For CPU counter sets:
+ *    Basic counter set:	     0-31
+ *    Problem-state counter set:    32-63
+ *    Crypto-activity counter set:  64-127
+ *    Extented counter set:	   128-159
+ */
+enum cpumf_ctr_set {
+	/* CPU counter sets */
+	CPUMF_CTR_SET_BASIC   = 0,
+	CPUMF_CTR_SET_USER    = 1,
+	CPUMF_CTR_SET_CRYPTO  = 2,
+	CPUMF_CTR_SET_EXT     = 3,
+
+	/* Maximum number of counter sets */
+	CPUMF_CTR_SET_MAX,
+};
+
+#define CPUMF_LCCTL_ENABLE_SHIFT    16
+#define CPUMF_LCCTL_ACTCTL_SHIFT     0
+static const u64 cpumf_state_ctl[CPUMF_CTR_SET_MAX] = {
+	[CPUMF_CTR_SET_BASIC]	= 0x02,
+	[CPUMF_CTR_SET_USER]	= 0x04,
+	[CPUMF_CTR_SET_CRYPTO]	= 0x08,
+	[CPUMF_CTR_SET_EXT]	= 0x01,
+};
+
+static void ctr_set_enable(u64 *state, int ctr_set)
+{
+	*state |= cpumf_state_ctl[ctr_set] << CPUMF_LCCTL_ENABLE_SHIFT;
+}
+static void ctr_set_disable(u64 *state, int ctr_set)
+{
+	*state &= ~(cpumf_state_ctl[ctr_set] << CPUMF_LCCTL_ENABLE_SHIFT);
+}
+static void ctr_set_start(u64 *state, int ctr_set)
+{
+	*state |= cpumf_state_ctl[ctr_set] << CPUMF_LCCTL_ACTCTL_SHIFT;
+}
+static void ctr_set_stop(u64 *state, int ctr_set)
+{
+	*state &= ~(cpumf_state_ctl[ctr_set] << CPUMF_LCCTL_ACTCTL_SHIFT);
+}
+
+/* Local CPUMF event structure */
+struct cpu_hw_events {
+	struct cpumf_ctr_info	info;
+	atomic_t		ctr_set[CPUMF_CTR_SET_MAX];
+	u64			state, tx_state;
+	unsigned int		flags;
+};
+static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events) = {
+	.ctr_set = {
+		[CPUMF_CTR_SET_BASIC]  = ATOMIC_INIT(0),
+		[CPUMF_CTR_SET_USER]   = ATOMIC_INIT(0),
+		[CPUMF_CTR_SET_CRYPTO] = ATOMIC_INIT(0),
+		[CPUMF_CTR_SET_EXT]    = ATOMIC_INIT(0),
+	},
+	.state = 0,
+	.flags = 0,
+};
+
+static int get_counter_set(u64 event)
+{
+	int set = -1;
+
+	if (event < 32)
+		set = CPUMF_CTR_SET_BASIC;
+	else if (event < 64)
+		set = CPUMF_CTR_SET_USER;
+	else if (event < 128)
+		set = CPUMF_CTR_SET_CRYPTO;
+	else if (event < 160)
+		set = CPUMF_CTR_SET_EXT;
+
+	return set;
+}
+
+static int validate_event(const struct hw_perf_event *hwc)
+{
+	switch (hwc->config_base) {
+	case CPUMF_CTR_SET_BASIC:
+	case CPUMF_CTR_SET_USER:
+	case CPUMF_CTR_SET_CRYPTO:
+	case CPUMF_CTR_SET_EXT:
+		/* check for reserved counters */
+		if ((hwc->config >=  6 && hwc->config <=  31) ||
+		    (hwc->config >= 38 && hwc->config <=  63) ||
+		    (hwc->config >= 80 && hwc->config <= 127))
+			return -EOPNOTSUPP;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int validate_ctr_version(const struct hw_perf_event *hwc)
+{
+	struct cpu_hw_events *cpuhw;
+	int err = 0;
+
+	cpuhw = &get_cpu_var(cpu_hw_events);
+
+	/* check required version for counter sets */
+	switch (hwc->config_base) {
+	case CPUMF_CTR_SET_BASIC:
+	case CPUMF_CTR_SET_USER:
+		if (cpuhw->info.cfvn < 1)
+			err = -EOPNOTSUPP;
+		break;
+	case CPUMF_CTR_SET_CRYPTO:
+	case CPUMF_CTR_SET_EXT:
+		if (cpuhw->info.csvn < 1)
+			err = -EOPNOTSUPP;
+		break;
+	}
+
+	put_cpu_var(cpu_hw_events);
+	return err;
+}
+
+static int validate_ctr_auth(const struct hw_perf_event *hwc)
+{
+	struct cpu_hw_events *cpuhw;
+	u64 ctrs_state;
+	int err = 0;
+
+	cpuhw = &get_cpu_var(cpu_hw_events);
+
+	/* check authorization for cpu counter sets */
+	ctrs_state = cpumf_state_ctl[hwc->config_base];
+	if (!(ctrs_state & cpuhw->info.auth_ctl))
+		err = -EPERM;
+
+	put_cpu_var(cpu_hw_events);
+	return err;
+}
+
+/*
+ * Change the CPUMF state to active.
+ * Enable and activate the CPU-counter sets according
+ * to the per-cpu control state.
+ */
+static void cpumf_pmu_enable(struct pmu *pmu)
+{
+	struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
+	int err;
+
+	if (cpuhw->flags & PMU_F_ENABLED)
+		return;
+
+	err = lcctl(cpuhw->state);
+	if (err) {
+		pr_err("Enabling the performance measuring unit "
+		       "failed with rc=%lx\n", err);
+		return;
+	}
+
+	cpuhw->flags |= PMU_F_ENABLED;
+}
+
+/*
+ * Change the CPUMF state to inactive.
+ * Disable and enable (inactive) the CPU-counter sets according
+ * to the per-cpu control state.
+ */
+static void cpumf_pmu_disable(struct pmu *pmu)
+{
+	struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
+	int err;
+	u64 inactive;
+
+	if (!(cpuhw->flags & PMU_F_ENABLED))
+		return;
+
+	inactive = cpuhw->state & ~((1 << CPUMF_LCCTL_ENABLE_SHIFT) - 1);
+	err = lcctl(inactive);
+	if (err) {
+		pr_err("Disabling the performance measuring unit "
+		       "failed with rc=%lx\n", err);
+		return;
+	}
+
+	cpuhw->flags &= ~PMU_F_ENABLED;
+}
+
+
+/* Number of perf events counting hardware events */
+static atomic_t num_events = ATOMIC_INIT(0);
+/* Used to avoid races in calling reserve/release_cpumf_hardware */
+static DEFINE_MUTEX(pmc_reserve_mutex);
+
+/* CPU-measurement alerts for the counter facility */
+static void cpumf_measurement_alert(struct ext_code ext_code,
+				    unsigned int alert, unsigned long unused)
+{
+	struct cpu_hw_events *cpuhw;
+
+	if (!(alert & CPU_MF_INT_CF_MASK))
+		return;
+
+	kstat_cpu(smp_processor_id()).irqs[EXTINT_CPM]++;
+	cpuhw = &__get_cpu_var(cpu_hw_events);
+
+	/* Measurement alerts are shared and might happen when the PMU
+	 * is not reserved.  Ignore these alerts in this case. */
+	if (!(cpuhw->flags & PMU_F_RESERVED))
+		return;
+
+	/* counter authorization change alert */
+	if (alert & CPU_MF_INT_CF_CACA)
+		qctri(&cpuhw->info);
+
+	/* loss of counter data alert */
+	if (alert & CPU_MF_INT_CF_LCDA)
+		pr_err("CPU[%i] Counter data was lost\n", smp_processor_id());
+}
+
+#define PMC_INIT      0
+#define PMC_RELEASE   1
+static void setup_pmc_cpu(void *flags)
+{
+	struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
+
+	switch (*((int *) flags)) {
+	case PMC_INIT:
+		memset(&cpuhw->info, 0, sizeof(cpuhw->info));
+		qctri(&cpuhw->info);
+		cpuhw->flags |= PMU_F_RESERVED;
+		break;
+
+	case PMC_RELEASE:
+		cpuhw->flags &= ~PMU_F_RESERVED;
+		break;
+	}
+
+	/* Disable CPU counter sets */
+	lcctl(0);
+}
+
+/* Initialize the CPU-measurement facility */
+static int reserve_pmc_hardware(void)
+{
+	int flags = PMC_INIT;
+
+	on_each_cpu(setup_pmc_cpu, &flags, 1);
+	measurement_alert_subclass_register();
+
+	return 0;
+}
+
+/* Release the CPU-measurement facility */
+static void release_pmc_hardware(void)
+{
+	int flags = PMC_RELEASE;
+
+	on_each_cpu(setup_pmc_cpu, &flags, 1);
+	measurement_alert_subclass_unregister();
+}
+
+/* Release the PMU if event is the last perf event */
+static void hw_perf_event_destroy(struct perf_event *event)
+{
+	if (!atomic_add_unless(&num_events, -1, 1)) {
+		mutex_lock(&pmc_reserve_mutex);
+		if (atomic_dec_return(&num_events) == 0)
+			release_pmc_hardware();
+		mutex_unlock(&pmc_reserve_mutex);
+	}
+}
+
+/* CPUMF <-> perf event mappings for kernel+userspace (basic set) */
+static const int cpumf_generic_events_basic[] = {
+	[PERF_COUNT_HW_CPU_CYCLES]	    = 0,
+	[PERF_COUNT_HW_INSTRUCTIONS]	    = 1,
+	[PERF_COUNT_HW_CACHE_REFERENCES]    = -1,
+	[PERF_COUNT_HW_CACHE_MISSES]	    = -1,
+	[PERF_COUNT_HW_BRANCH_INSTRUCTIONS] = -1,
+	[PERF_COUNT_HW_BRANCH_MISSES]	    = -1,
+	[PERF_COUNT_HW_BUS_CYCLES]	    = -1,
+};
+/* CPUMF <-> perf event mappings for userspace (problem-state set) */
+static const int cpumf_generic_events_user[] = {
+	[PERF_COUNT_HW_CPU_CYCLES]	    = 32,
+	[PERF_COUNT_HW_INSTRUCTIONS]	    = 33,
+	[PERF_COUNT_HW_CACHE_REFERENCES]    = -1,
+	[PERF_COUNT_HW_CACHE_MISSES]	    = -1,
+	[PERF_COUNT_HW_BRANCH_INSTRUCTIONS] = -1,
+	[PERF_COUNT_HW_BRANCH_MISSES]	    = -1,
+	[PERF_COUNT_HW_BUS_CYCLES]	    = -1,
+};
+
+static int __hw_perf_event_init(struct perf_event *event)
+{
+	struct perf_event_attr *attr = &event->attr;
+	struct hw_perf_event *hwc = &event->hw;
+	int err;
+	u64 ev;
+
+	switch (attr->type) {
+	case PERF_TYPE_RAW:
+		/* Raw events are used to access counters directly,
+		 * hence do not permit excludes */
+		if (attr->exclude_kernel || attr->exclude_user ||
+		    attr->exclude_hv)
+			return -EOPNOTSUPP;
+		ev = attr->config;
+		break;
+
+	case PERF_TYPE_HARDWARE:
+		ev = attr->config;
+		/* Count user space (problem-state) only */
+		if (!attr->exclude_user && attr->exclude_kernel) {
+			if (ev >= ARRAY_SIZE(cpumf_generic_events_user))
+				return -EOPNOTSUPP;
+			ev = cpumf_generic_events_user[ev];
+
+		/* No support for kernel space counters only */
+		} else if (!attr->exclude_kernel && attr->exclude_user) {
+			return -EOPNOTSUPP;
+
+		/* Count user and kernel space */
+		} else {
+			if (ev >= ARRAY_SIZE(cpumf_generic_events_basic))
+				return -EOPNOTSUPP;
+			ev = cpumf_generic_events_basic[ev];
+		}
+		break;
+
+	default:
+		return -ENOENT;
+	}
+
+	if (ev == -1)
+		return -ENOENT;
+
+	if (ev >= PERF_CPUM_CF_MAX_CTR)
+		return -EINVAL;
+
+	/* The CPU measurement counter facility does not have any interrupts
+	 * to do sampling.  Sampling must be provided by external means,
+	 * for example, by timers.
+	 */
+	if (hwc->sample_period)
+		return -EINVAL;
+
+	/* Use the hardware perf event structure to store the counter number
+	 * in 'config' member and the counter set to which the counter belongs
+	 * in the 'config_base'.  The counter set (config_base) is then used
+	 * to enable/disable the counters.
+	 */
+	hwc->config = ev;
+	hwc->config_base = get_counter_set(ev);
+
+	/* Validate the counter that is assigned to this event.
+	 * Because the counter facility can use numerous counters at the
+	 * same time without constraints, it is not necessary to explicity
+	 * validate event groups (event->group_leader != event).
+	 */
+	err = validate_event(hwc);
+	if (err)
+		return err;
+
+	/* Initialize for using the CPU-measurement counter facility */
+	if (!atomic_inc_not_zero(&num_events)) {
+		mutex_lock(&pmc_reserve_mutex);
+		if (atomic_read(&num_events) == 0 && reserve_pmc_hardware())
+			err = -EBUSY;
+		else
+			atomic_inc(&num_events);
+		mutex_unlock(&pmc_reserve_mutex);
+	}
+	event->destroy = hw_perf_event_destroy;
+
+	/* Finally, validate version and authorization of the counter set */
+	err = validate_ctr_auth(hwc);
+	if (!err)
+		err = validate_ctr_version(hwc);
+
+	return err;
+}
+
+static int cpumf_pmu_event_init(struct perf_event *event)
+{
+	int err;
+
+	switch (event->attr.type) {
+	case PERF_TYPE_HARDWARE:
+	case PERF_TYPE_HW_CACHE:
+	case PERF_TYPE_RAW:
+		err = __hw_perf_event_init(event);
+		break;
+	default:
+		return -ENOENT;
+	}
+
+	if (unlikely(err) && event->destroy)
+		event->destroy(event);
+
+	return err;
+}
+
+static int hw_perf_event_reset(struct perf_event *event)
+{
+	u64 prev, new;
+	int err;
+
+	do {
+		prev = local64_read(&event->hw.prev_count);
+		err = ecctr(event->hw.config, &new);
+		if (err) {
+			if (err != 3)
+				break;
+			/* The counter is not (yet) available. This
+			 * might happen if the counter set to which
+			 * this counter belongs is in the disabled
+			 * state.
+			 */
+			new = 0;
+		}
+	} while (local64_cmpxchg(&event->hw.prev_count, prev, new) != prev);
+
+	return err;
+}
+
+static int hw_perf_event_update(struct perf_event *event)
+{
+	u64 prev, new, delta;
+	int err;
+
+	do {
+		prev = local64_read(&event->hw.prev_count);
+		err = ecctr(event->hw.config, &new);
+		if (err)
+			goto out;
+	} while (local64_cmpxchg(&event->hw.prev_count, prev, new) != prev);
+
+	delta = (prev <= new) ? new - prev
+			      : (-1ULL - prev) + new + 1;	 /* overflow */
+	local64_add(delta, &event->count);
+out:
+	return err;
+}
+
+static void cpumf_pmu_read(struct perf_event *event)
+{
+	if (event->hw.state & PERF_HES_STOPPED)
+		return;
+
+	hw_perf_event_update(event);
+}
+
+static void cpumf_pmu_start(struct perf_event *event, int flags)
+{
+	struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
+	struct hw_perf_event *hwc = &event->hw;
+
+	if (WARN_ON_ONCE(!(hwc->state & PERF_HES_STOPPED)))
+		return;
+
+	if (WARN_ON_ONCE(hwc->config == -1))
+		return;
+
+	if (flags & PERF_EF_RELOAD)
+		WARN_ON_ONCE(!(hwc->state & PERF_HES_UPTODATE));
+
+	hwc->state = 0;
+
+	/* (Re-)enable and activate the counter set */
+	ctr_set_enable(&cpuhw->state, hwc->config_base);
+	ctr_set_start(&cpuhw->state, hwc->config_base);
+
+	/* The counter set to which this counter belongs can be already active.
+	 * Because all counters in a set are active, the event->hw.prev_count
+	 * needs to be synchronized.  At this point, the counter set can be in
+	 * the inactive or disabled state.
+	 */
+	hw_perf_event_reset(event);
+
+	/* increment refcount for this counter set */
+	atomic_inc(&cpuhw->ctr_set[hwc->config_base]);
+}
+
+static void cpumf_pmu_stop(struct perf_event *event, int flags)
+{
+	struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
+	struct hw_perf_event *hwc = &event->hw;
+
+	if (!(hwc->state & PERF_HES_STOPPED)) {
+		/* Decrement reference count for this counter set and if this
+		 * is the last used counter in the set, clear activation
+		 * control and set the counter set state to inactive.
+		 */
+		if (!atomic_dec_return(&cpuhw->ctr_set[hwc->config_base]))
+			ctr_set_stop(&cpuhw->state, hwc->config_base);
+		event->hw.state |= PERF_HES_STOPPED;
+	}
+
+	if ((flags & PERF_EF_UPDATE) && !(hwc->state & PERF_HES_UPTODATE)) {
+		hw_perf_event_update(event);
+		event->hw.state |= PERF_HES_UPTODATE;
+	}
+}
+
+static int cpumf_pmu_add(struct perf_event *event, int flags)
+{
+	struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
+
+	/* Check authorization for the counter set to which this
+	 * counter belongs.
+	 * For group events transaction, the authorization check is
+	 * done in cpumf_pmu_commit_txn().
+	 */
+	if (!(cpuhw->flags & PERF_EVENT_TXN))
+		if (validate_ctr_auth(&event->hw))
+			return -EPERM;
+
+	ctr_set_enable(&cpuhw->state, event->hw.config_base);
+	event->hw.state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
+
+	if (flags & PERF_EF_START)
+		cpumf_pmu_start(event, PERF_EF_RELOAD);
+
+	perf_event_update_userpage(event);
+
+	return 0;
+}
+
+static void cpumf_pmu_del(struct perf_event *event, int flags)
+{
+	struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
+
+	cpumf_pmu_stop(event, PERF_EF_UPDATE);
+
+	/* Check if any counter in the counter set is still used.  If not used,
+	 * change the counter set to the disabled state.  This also clears the
+	 * content of all counters in the set.
+	 *
+	 * When a new perf event has been added but not yet started, this can
+	 * clear enable control and resets all counters in a set.  Therefore,
+	 * cpumf_pmu_start() always has to reenable a counter set.
+	 */
+	if (!atomic_read(&cpuhw->ctr_set[event->hw.config_base]))
+		ctr_set_disable(&cpuhw->state, event->hw.config_base);
+
+	perf_event_update_userpage(event);
+}
+
+/*
+ * Start group events scheduling transaction.
+ * Set flags to perform a single test at commit time.
+ */
+static void cpumf_pmu_start_txn(struct pmu *pmu)
+{
+	struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
+
+	perf_pmu_disable(pmu);
+	cpuhw->flags |= PERF_EVENT_TXN;
+	cpuhw->tx_state = cpuhw->state;
+}
+
+/*
+ * Stop and cancel a group events scheduling tranctions.
+ * Assumes cpumf_pmu_del() is called for each successful added
+ * cpumf_pmu_add() during the transaction.
+ */
+static void cpumf_pmu_cancel_txn(struct pmu *pmu)
+{
+	struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
+
+	WARN_ON(cpuhw->tx_state != cpuhw->state);
+
+	cpuhw->flags &= ~PERF_EVENT_TXN;
+	perf_pmu_enable(pmu);
+}
+
+/*
+ * Commit the group events scheduling transaction.  On success, the
+ * transaction is closed.   On error, the transaction is kept open
+ * until cpumf_pmu_cancel_txn() is called.
+ */
+static int cpumf_pmu_commit_txn(struct pmu *pmu)
+{
+	struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
+	u64 state;
+
+	/* check if the updated state can be scheduled */
+	state = cpuhw->state & ~((1 << CPUMF_LCCTL_ENABLE_SHIFT) - 1);
+	state >>= CPUMF_LCCTL_ENABLE_SHIFT;
+	if ((state & cpuhw->info.auth_ctl) != state)
+		return -EPERM;
+
+	cpuhw->flags &= ~PERF_EVENT_TXN;
+	perf_pmu_enable(pmu);
+	return 0;
+}
+
+/* Performance monitoring unit for s390x */
+static struct pmu cpumf_pmu = {
+	.pmu_enable   = cpumf_pmu_enable,
+	.pmu_disable  = cpumf_pmu_disable,
+	.event_init   = cpumf_pmu_event_init,
+	.add	      = cpumf_pmu_add,
+	.del	      = cpumf_pmu_del,
+	.start	      = cpumf_pmu_start,
+	.stop	      = cpumf_pmu_stop,
+	.read	      = cpumf_pmu_read,
+	.start_txn    = cpumf_pmu_start_txn,
+	.commit_txn   = cpumf_pmu_commit_txn,
+	.cancel_txn   = cpumf_pmu_cancel_txn,
+};
+
+static int __cpuinit cpumf_pmu_notifier(struct notifier_block *self,
+					unsigned long action, void *hcpu)
+{
+	unsigned int cpu = (long) hcpu;
+	int flags;
+
+	switch (action & ~CPU_TASKS_FROZEN) {
+	case CPU_ONLINE:
+		flags = PMC_INIT;
+		smp_call_function_single(cpu, setup_pmc_cpu, &flags, 1);
+		break;
+	case CPU_DOWN_PREPARE:
+		flags = PMC_RELEASE;
+		smp_call_function_single(cpu, setup_pmc_cpu, &flags, 1);
+		break;
+	default:
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static int __init cpumf_pmu_init(void)
+{
+	int rc;
+
+	if (!cpum_cf_avail())
+		return -ENODEV;
+
+	/* clear bit 15 of cr0 to unauthorize problem-state to
+	 * extract measurement counters */
+	ctl_clear_bit(0, 48);
+
+	/* register handler for measurement-alert interruptions */
+	rc = register_external_interrupt(0x1407, cpumf_measurement_alert);
+	if (rc) {
+		pr_err("Registering for CPU-measurement alerts "
+		       "failed with rc=%i\n", rc);
+		goto out;
+	}
+
+	rc = perf_pmu_register(&cpumf_pmu, "cpum_cf", PERF_TYPE_RAW);
+	if (rc) {
+		pr_err("Registering the cpum_cf PMU failed with rc=%i\n", rc);
+		unregister_external_interrupt(0x1407, cpumf_measurement_alert);
+		goto out;
+	}
+	perf_cpu_notifier(cpumf_pmu_notifier);
+out:
+	return rc;
+}
+early_initcall(cpumf_pmu_init);