Merge tag 'locking-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel...

[linux/fpc-iii.git] / arch / s390 / kernel / perf_cpum_cf_diag.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Performance event support for s390x - CPU-measurement Counter Sets
 *
 *  Copyright IBM Corp. 2019
 *  Author(s): Hendrik Brueckner <brueckner@linux.ibm.com>
 *             Thomas Richer <tmricht@linux.ibm.com>
 */
#define KMSG_COMPONENT  "cpum_cf_diag"
#define pr_fmt(fmt)     KMSG_COMPONENT ": " fmt

#include <linux/kernel.h>
#include <linux/kernel_stat.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/processor.h>

#include <asm/ctl_reg.h>
#include <asm/irq.h>
#include <asm/cpu_mcf.h>
#include <asm/timex.h>
#include <asm/debug.h>

#define CF_DIAG_CTRSET_DEF              0xfeef  /* Counter set header mark */

static unsigned int cf_diag_cpu_speed;
static debug_info_t *cf_diag_dbg;

struct cf_diag_csd {            /* Counter set data per CPU */
        size_t used;                    /* Bytes used in data/start */
        unsigned char start[PAGE_SIZE]; /* Counter set at event start */
        unsigned char data[PAGE_SIZE];  /* Counter set at event delete */
};
static DEFINE_PER_CPU(struct cf_diag_csd, cf_diag_csd);

/* Counter sets are stored as data stream in a page sized memory buffer and
 * exported to user space via raw data attached to the event sample data.
 * Each counter set starts with an eight byte header consisting of:
 * - a two byte eye catcher (0xfeef)
 * - a one byte counter set number
 * - a two byte counter set size (indicates the number of counters in this set)
 * - a three byte reserved value (must be zero) to make the header the same
 *   size as a counter value.
 * All counter values are eight byte in size.
 *
 * All counter sets are followed by a 64 byte trailer.
 * The trailer consists of a:
 * - flag field indicating valid fields when corresponding bit set
 * - the counter facility first and second version number
 * - the CPU speed if nonzero
 * - the time stamp the counter sets have been collected
 * - the time of day (TOD) base value
 * - the machine type.
 *
 * The counter sets are saved when the process is prepared to be executed on a
 * CPU and saved again when the process is going to be removed from a CPU.
 * The difference of both counter sets are calculated and stored in the event
 * sample data area.
 */

struct cf_ctrset_entry {        /* CPU-M CF counter set entry (8 byte) */
        unsigned int def:16;    /* 0-15  Data Entry Format */
        unsigned int set:16;    /* 16-31 Counter set identifier */
        unsigned int ctr:16;    /* 32-47 Number of stored counters */
        unsigned int res1:16;   /* 48-63 Reserved */
};

struct cf_trailer_entry {       /* CPU-M CF_DIAG trailer (64 byte) */
        /* 0 - 7 */
        union {
                struct {
                        unsigned int clock_base:1;      /* TOD clock base set */
                        unsigned int speed:1;           /* CPU speed set */
                        /* Measurement alerts */
                        unsigned int mtda:1;    /* Loss of MT ctr. data alert */
                        unsigned int caca:1;    /* Counter auth. change alert */
                        unsigned int lcda:1;    /* Loss of counter data alert */
                };
                unsigned long flags;    /* 0-63    All indicators */
        };
        /* 8 - 15 */
        unsigned int cfvn:16;                   /* 64-79   Ctr First Version */
        unsigned int csvn:16;                   /* 80-95   Ctr Second Version */
        unsigned int cpu_speed:32;              /* 96-127  CPU speed */
        /* 16 - 23 */
        unsigned long timestamp;                /* 128-191 Timestamp (TOD) */
        /* 24 - 55 */
        union {
                struct {
                        unsigned long progusage1;
                        unsigned long progusage2;
                        unsigned long progusage3;
                        unsigned long tod_base;
                };
                unsigned long progusage[4];
        };
        /* 56 - 63 */
        unsigned int mach_type:16;              /* Machine type */
        unsigned int res1:16;                   /* Reserved */
        unsigned int res2:32;                   /* Reserved */
};

/* Create the trailer data at the end of a page. */
static void cf_diag_trailer(struct cf_trailer_entry *te)
{
        struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);
        struct cpuid cpuid;

        te->cfvn = cpuhw->info.cfvn;            /* Counter version numbers */
        te->csvn = cpuhw->info.csvn;

        get_cpu_id(&cpuid);                     /* Machine type */
        te->mach_type = cpuid.machine;
        te->cpu_speed = cf_diag_cpu_speed;
        if (te->cpu_speed)
                te->speed = 1;
        te->clock_base = 1;                     /* Save clock base */
        memcpy(&te->tod_base, &tod_clock_base[1], 8);
        store_tod_clock((__u64 *)&te->timestamp);
}

/*
 * Change the CPUMF state to active.
 * Enable and activate the CPU-counter sets according
 * to the per-cpu control state.
 */
static void cf_diag_enable(struct pmu *pmu)
{
        struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);
        int err;

        debug_sprintf_event(cf_diag_dbg, 5,
                            "%s pmu %p cpu %d flags %#x state %#llx\n",
                            __func__, pmu, smp_processor_id(), cpuhw->flags,
                            cpuhw->state);
        if (cpuhw->flags & PMU_F_ENABLED)
                return;

        err = lcctl(cpuhw->state);
        if (err) {
                pr_err("Enabling the performance measuring unit "
                       "failed with rc=%x\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 cf_diag_disable(struct pmu *pmu)
{
        struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);
        u64 inactive;
        int err;

        debug_sprintf_event(cf_diag_dbg, 5,
                            "%s pmu %p cpu %d flags %#x state %#llx\n",
                            __func__, pmu, smp_processor_id(), cpuhw->flags,
                            cpuhw->state);
        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=%x\n", err);
                return;
        }
        cpuhw->flags &= ~PMU_F_ENABLED;
}

/* Number of perf events counting hardware events */
static atomic_t cf_diag_events = ATOMIC_INIT(0);

/* Release the PMU if event is the last perf event */
static void cf_diag_perf_event_destroy(struct perf_event *event)
{
        debug_sprintf_event(cf_diag_dbg, 5,
                            "%s event %p cpu %d cf_diag_events %d\n",
                            __func__, event, event->cpu,
                            atomic_read(&cf_diag_events));
        if (atomic_dec_return(&cf_diag_events) == 0)
                __kernel_cpumcf_end();
}

/* Setup the event. Test for authorized counter sets and only include counter
 * sets which are authorized at the time of the setup. Including unauthorized
 * counter sets result in specification exception (and panic).
 */
static int __hw_perf_event_init(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        struct cpu_cf_events *cpuhw;
        enum cpumf_ctr_set i;
        int err = 0;

        debug_sprintf_event(cf_diag_dbg, 5, "%s event %p cpu %d\n", __func__,
                            event, event->cpu);

        event->hw.config = attr->config;
        event->hw.config_base = 0;

        /* Add all authorized counter sets to config_base. The
         * the hardware init function is either called per-cpu or just once
         * for all CPUS (event->cpu == -1).  This depends on the whether
         * counting is started for all CPUs or on a per workload base where
         * the perf event moves from one CPU to another CPU.
         * Checking the authorization on any CPU is fine as the hardware
         * applies the same authorization settings to all CPUs.
         */
        cpuhw = &get_cpu_var(cpu_cf_events);
        for (i = CPUMF_CTR_SET_BASIC; i < CPUMF_CTR_SET_MAX; ++i)
                if (cpuhw->info.auth_ctl & cpumf_ctr_ctl[i])
                        event->hw.config_base |= cpumf_ctr_ctl[i];
        put_cpu_var(cpu_cf_events);

        /* No authorized counter sets, nothing to count/sample */
        if (!event->hw.config_base) {
                err = -EINVAL;
                goto out;
        }

        /* Set sample_period to indicate sampling */
        event->hw.sample_period = attr->sample_period;
        local64_set(&event->hw.period_left, event->hw.sample_period);
        event->hw.last_period  = event->hw.sample_period;
out:
        debug_sprintf_event(cf_diag_dbg, 5, "%s err %d config_base %#lx\n",
                            __func__, err, event->hw.config_base);
        return err;
}

static int cf_diag_event_init(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        int err = -ENOENT;

        debug_sprintf_event(cf_diag_dbg, 5,
                            "%s event %p cpu %d config %#llx type:%u "
                            "sample_type %#llx cf_diag_events %d\n", __func__,
                            event, event->cpu, attr->config, event->pmu->type,
                            attr->sample_type, atomic_read(&cf_diag_events));

        if (event->attr.config != PERF_EVENT_CPUM_CF_DIAG ||
            event->attr.type != event->pmu->type)
                goto out;

        /* Raw events are used to access counters directly,
         * hence do not permit excludes.
         * This event is usesless without PERF_SAMPLE_RAW to return counter set
         * values as raw data.
         */
        if (attr->exclude_kernel || attr->exclude_user || attr->exclude_hv ||
            !(attr->sample_type & (PERF_SAMPLE_CPU | PERF_SAMPLE_RAW))) {
                err = -EOPNOTSUPP;
                goto out;
        }

        /* Initialize for using the CPU-measurement counter facility */
        if (atomic_inc_return(&cf_diag_events) == 1) {
                if (__kernel_cpumcf_begin()) {
                        atomic_dec(&cf_diag_events);
                        err = -EBUSY;
                        goto out;
                }
        }
        event->destroy = cf_diag_perf_event_destroy;

        err = __hw_perf_event_init(event);
        if (unlikely(err))
                event->destroy(event);
out:
        debug_sprintf_event(cf_diag_dbg, 5, "%s err %d\n", __func__, err);
        return err;
}

static void cf_diag_read(struct perf_event *event)
{
        debug_sprintf_event(cf_diag_dbg, 5, "%s event %p\n", __func__, event);
}

/* Return the maximum possible counter set size (in number of 8 byte counters)
 * depending on type and model number.
 */
static size_t cf_diag_ctrset_size(enum cpumf_ctr_set ctrset,
                                 struct cpumf_ctr_info *info)
{
        size_t ctrset_size = 0;

        switch (ctrset) {
        case CPUMF_CTR_SET_BASIC:
                if (info->cfvn >= 1)
                        ctrset_size = 6;
                break;
        case CPUMF_CTR_SET_USER:
                if (info->cfvn == 1)
                        ctrset_size = 6;
                else if (info->cfvn >= 3)
                        ctrset_size = 2;
                break;
        case CPUMF_CTR_SET_CRYPTO:
                if (info->csvn >= 1 && info->csvn <= 5)
                        ctrset_size = 16;
                else if (info->csvn == 6)
                        ctrset_size = 20;
                break;
        case CPUMF_CTR_SET_EXT:
                if (info->csvn == 1)
                        ctrset_size = 32;
                else if (info->csvn == 2)
                        ctrset_size = 48;
                else if (info->csvn >= 3 && info->csvn <= 5)
                        ctrset_size = 128;
                else if (info->csvn == 6)
                        ctrset_size = 160;
                break;
        case CPUMF_CTR_SET_MT_DIAG:
                if (info->csvn > 3)
                        ctrset_size = 48;
                break;
        case CPUMF_CTR_SET_MAX:
                break;
        }

        return ctrset_size;
}

/* Calculate memory needed to store all counter sets together with header and
 * trailer data. This is independend of the counter set authorization which
 * can vary depending on the configuration.
 */
static size_t cf_diag_ctrset_maxsize(struct cpumf_ctr_info *info)
{
        size_t max_size = sizeof(struct cf_trailer_entry);
        enum cpumf_ctr_set i;

        for (i = CPUMF_CTR_SET_BASIC; i < CPUMF_CTR_SET_MAX; ++i) {
                size_t size = cf_diag_ctrset_size(i, info);

                if (size)
                        max_size += size * sizeof(u64) +
                                    sizeof(struct cf_ctrset_entry);
        }
        debug_sprintf_event(cf_diag_dbg, 5, "%s max_size %zu\n", __func__,
                            max_size);

        return max_size;
}

/* Read a counter set. The counter set number determines which counter set and
 * the CPUM-CF first and second version number determine the number of
 * available counters in this counter set.
 * Each counter set starts with header containing the counter set number and
 * the number of 8 byte counters.
 *
 * The functions returns the number of bytes occupied by this counter set
 * including the header.
 * If there is no counter in the counter set, this counter set is useless and
 * zero is returned on this case.
 */
static size_t cf_diag_getctrset(struct cf_ctrset_entry *ctrdata, int ctrset,
                                size_t room)
{
        struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);
        size_t ctrset_size, need = 0;
        int rc = 3;                             /* Assume write failure */

        ctrdata->def = CF_DIAG_CTRSET_DEF;
        ctrdata->set = ctrset;
        ctrdata->res1 = 0;
        ctrset_size = cf_diag_ctrset_size(ctrset, &cpuhw->info);

        if (ctrset_size) {                      /* Save data */
                need = ctrset_size * sizeof(u64) + sizeof(*ctrdata);
                if (need <= room)
                        rc = ctr_stcctm(ctrset, ctrset_size,
                                        (u64 *)(ctrdata + 1));
                if (rc != 3)
                        ctrdata->ctr = ctrset_size;
                else
                        need = 0;
        }

        debug_sprintf_event(cf_diag_dbg, 6,
                            "%s ctrset %d ctrset_size %zu cfvn %d csvn %d"
                            " need %zd rc %d\n",
                            __func__, ctrset, ctrset_size, cpuhw->info.cfvn,
                            cpuhw->info.csvn, need, rc);
        return need;
}

/* Read out all counter sets and save them in the provided data buffer.
 * The last 64 byte host an artificial trailer entry.
 */
static size_t cf_diag_getctr(void *data, size_t sz, unsigned long auth)
{
        struct cf_trailer_entry *trailer;
        size_t offset = 0, done;
        int i;

        memset(data, 0, sz);
        sz -= sizeof(*trailer);                 /* Always room for trailer */
        for (i = CPUMF_CTR_SET_BASIC; i < CPUMF_CTR_SET_MAX; ++i) {
                struct cf_ctrset_entry *ctrdata = data + offset;

                if (!(auth & cpumf_ctr_ctl[i]))
                        continue;       /* Counter set not authorized */

                done = cf_diag_getctrset(ctrdata, i, sz - offset);
                offset += done;
                debug_sprintf_event(cf_diag_dbg, 6,
                                    "%s ctrset %d offset %zu done %zu\n",
                                     __func__, i, offset, done);
        }
        trailer = data + offset;
        cf_diag_trailer(trailer);
        return offset + sizeof(*trailer);
}

/* Calculate the difference for each counter in a counter set. */
static void cf_diag_diffctrset(u64 *pstart, u64 *pstop, int counters)
{
        for (; --counters >= 0; ++pstart, ++pstop)
                if (*pstop >= *pstart)
                        *pstop -= *pstart;
                else
                        *pstop = *pstart - *pstop;
}

/* Scan the counter sets and calculate the difference of each counter
 * in each set. The result is the increment of each counter during the
 * period the counter set has been activated.
 *
 * Return true on success.
 */
static int cf_diag_diffctr(struct cf_diag_csd *csd, unsigned long auth)
{
        struct cf_trailer_entry *trailer_start, *trailer_stop;
        struct cf_ctrset_entry *ctrstart, *ctrstop;
        size_t offset = 0;

        auth &= (1 << CPUMF_LCCTL_ENABLE_SHIFT) - 1;
        do {
                ctrstart = (struct cf_ctrset_entry *)(csd->start + offset);
                ctrstop = (struct cf_ctrset_entry *)(csd->data + offset);

                if (memcmp(ctrstop, ctrstart, sizeof(*ctrstop))) {
                        pr_err("cpum_cf_diag counter set compare error "
                                "in set %i\n", ctrstart->set);
                        return 0;
                }
                auth &= ~cpumf_ctr_ctl[ctrstart->set];
                if (ctrstart->def == CF_DIAG_CTRSET_DEF) {
                        cf_diag_diffctrset((u64 *)(ctrstart + 1),
                                          (u64 *)(ctrstop + 1), ctrstart->ctr);
                        offset += ctrstart->ctr * sizeof(u64) +
                                  sizeof(*ctrstart);
                }
                debug_sprintf_event(cf_diag_dbg, 6,
                                    "%s set %d ctr %d offset %zu auth %lx\n",
                                    __func__, ctrstart->set, ctrstart->ctr,
                                    offset, auth);
        } while (ctrstart->def && auth);

        /* Save time_stamp from start of event in stop's trailer */
        trailer_start = (struct cf_trailer_entry *)(csd->start + offset);
        trailer_stop = (struct cf_trailer_entry *)(csd->data + offset);
        trailer_stop->progusage[0] = trailer_start->timestamp;

        return 1;
}

/* Create perf event sample with the counter sets as raw data.  The sample
 * is then pushed to the event subsystem and the function checks for
 * possible event overflows. If an event overflow occurs, the PMU is
 * stopped.
 *
 * Return non-zero if an event overflow occurred.
 */
static int cf_diag_push_sample(struct perf_event *event,
                               struct cf_diag_csd *csd)
{
        struct perf_sample_data data;
        struct perf_raw_record raw;
        struct pt_regs regs;
        int overflow;

        /* Setup perf sample */
        perf_sample_data_init(&data, 0, event->hw.last_period);
        memset(&regs, 0, sizeof(regs));
        memset(&raw, 0, sizeof(raw));

        if (event->attr.sample_type & PERF_SAMPLE_CPU)
                data.cpu_entry.cpu = event->cpu;
        if (event->attr.sample_type & PERF_SAMPLE_RAW) {
                raw.frag.size = csd->used;
                raw.frag.data = csd->data;
                raw.size = csd->used;
                data.raw = &raw;
        }

        overflow = perf_event_overflow(event, &data, &regs);
        debug_sprintf_event(cf_diag_dbg, 6,
                            "%s event %p cpu %d sample_type %#llx raw %d "
                            "ov %d\n", __func__, event, event->cpu,
                            event->attr.sample_type, raw.size, overflow);
        if (overflow)
                event->pmu->stop(event, 0);

        perf_event_update_userpage(event);
        return overflow;
}

static void cf_diag_start(struct perf_event *event, int flags)
{
        struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);
        struct cf_diag_csd *csd = this_cpu_ptr(&cf_diag_csd);
        struct hw_perf_event *hwc = &event->hw;

        debug_sprintf_event(cf_diag_dbg, 5,
                            "%s event %p cpu %d flags %#x hwc-state %#x\n",
                            __func__, event, event->cpu, flags, hwc->state);
        if (WARN_ON_ONCE(!(hwc->state & PERF_HES_STOPPED)))
                return;

        /* (Re-)enable and activate all counter sets */
        lcctl(0);               /* Reset counter sets */
        hwc->state = 0;
        ctr_set_multiple_enable(&cpuhw->state, hwc->config_base);
        lcctl(cpuhw->state);    /* Enable counter sets */
        csd->used = cf_diag_getctr(csd->start, sizeof(csd->start),
                                   event->hw.config_base);
        ctr_set_multiple_start(&cpuhw->state, hwc->config_base);
        /* Function cf_diag_enable() starts the counter sets. */
}

static void cf_diag_stop(struct perf_event *event, int flags)
{
        struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);
        struct cf_diag_csd *csd = this_cpu_ptr(&cf_diag_csd);
        struct hw_perf_event *hwc = &event->hw;

        debug_sprintf_event(cf_diag_dbg, 5,
                            "%s event %p cpu %d flags %#x hwc-state %#x\n",
                            __func__, event, event->cpu, flags, hwc->state);

        /* Deactivate all counter sets */
        ctr_set_multiple_stop(&cpuhw->state, hwc->config_base);
        local64_inc(&event->count);
        csd->used = cf_diag_getctr(csd->data, sizeof(csd->data),
                                   event->hw.config_base);
        if (cf_diag_diffctr(csd, event->hw.config_base))
                cf_diag_push_sample(event, csd);
        hwc->state |= PERF_HES_STOPPED;
}

static int cf_diag_add(struct perf_event *event, int flags)
{
        struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);
        int err = 0;

        debug_sprintf_event(cf_diag_dbg, 5,
                            "%s event %p cpu %d flags %#x cpuhw %p\n",
                            __func__, event, event->cpu, flags, cpuhw);

        if (cpuhw->flags & PMU_F_IN_USE) {
                err = -EAGAIN;
                goto out;
        }

        event->hw.state = PERF_HES_UPTODATE | PERF_HES_STOPPED;

        cpuhw->flags |= PMU_F_IN_USE;
        if (flags & PERF_EF_START)
                cf_diag_start(event, PERF_EF_RELOAD);
out:
        debug_sprintf_event(cf_diag_dbg, 5, "%s err %d\n", __func__, err);
        return err;
}

static void cf_diag_del(struct perf_event *event, int flags)
{
        struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);

        debug_sprintf_event(cf_diag_dbg, 5,
                            "%s event %p cpu %d flags %#x\n",
                           __func__, event, event->cpu, flags);

        cf_diag_stop(event, PERF_EF_UPDATE);
        ctr_set_multiple_stop(&cpuhw->state, event->hw.config_base);
        ctr_set_multiple_disable(&cpuhw->state, event->hw.config_base);
        cpuhw->flags &= ~PMU_F_IN_USE;
}

CPUMF_EVENT_ATTR(CF_DIAG, CF_DIAG, PERF_EVENT_CPUM_CF_DIAG);

static struct attribute *cf_diag_events_attr[] = {
        CPUMF_EVENT_PTR(CF_DIAG, CF_DIAG),
        NULL,
};

PMU_FORMAT_ATTR(event, "config:0-63");

static struct attribute *cf_diag_format_attr[] = {
        &format_attr_event.attr,
        NULL,
};

static struct attribute_group cf_diag_events_group = {
        .name = "events",
        .attrs = cf_diag_events_attr,
};
static struct attribute_group cf_diag_format_group = {
        .name = "format",
        .attrs = cf_diag_format_attr,
};
static const struct attribute_group *cf_diag_attr_groups[] = {
        &cf_diag_events_group,
        &cf_diag_format_group,
        NULL,
};

/* Performance monitoring unit for s390x */
static struct pmu cf_diag = {
        .task_ctx_nr  = perf_sw_context,
        .pmu_enable   = cf_diag_enable,
        .pmu_disable  = cf_diag_disable,
        .event_init   = cf_diag_event_init,
        .add          = cf_diag_add,
        .del          = cf_diag_del,
        .start        = cf_diag_start,
        .stop         = cf_diag_stop,
        .read         = cf_diag_read,

        .attr_groups  = cf_diag_attr_groups
};

/* Get the CPU speed, try sampling facility first and CPU attributes second. */
static void cf_diag_get_cpu_speed(void)
{
        if (cpum_sf_avail()) {                  /* Sampling facility first */
                struct hws_qsi_info_block si;

                memset(&si, 0, sizeof(si));
                if (!qsi(&si)) {
                        cf_diag_cpu_speed = si.cpu_speed;
                        return;
                }
        }

        if (test_facility(34)) {                /* CPU speed extract static part */
                unsigned long mhz = __ecag(ECAG_CPU_ATTRIBUTE, 0);

                if (mhz != -1UL)
                        cf_diag_cpu_speed = mhz & 0xffffffff;
        }
}

/* Initialize the counter set PMU to generate complete counter set data as
 * event raw data. This relies on the CPU Measurement Counter Facility device
 * already being loaded and initialized.
 */
static int __init cf_diag_init(void)
{
        struct cpumf_ctr_info info;
        size_t need;
        int rc;

        if (!kernel_cpumcf_avail() || !stccm_avail() || qctri(&info))
                return -ENODEV;
        cf_diag_get_cpu_speed();

        /* Make sure the counter set data fits into predefined buffer. */
        need = cf_diag_ctrset_maxsize(&info);
        if (need > sizeof(((struct cf_diag_csd *)0)->start)) {
                pr_err("Insufficient memory for PMU(cpum_cf_diag) need=%zu\n",
                       need);
                return -ENOMEM;
        }

        /* Setup s390dbf facility */
        cf_diag_dbg = debug_register(KMSG_COMPONENT, 2, 1, 128);
        if (!cf_diag_dbg) {
                pr_err("Registration of s390dbf(cpum_cf_diag) failed\n");
                return -ENOMEM;
        }
        debug_register_view(cf_diag_dbg, &debug_sprintf_view);

        rc = perf_pmu_register(&cf_diag, "cpum_cf_diag", -1);
        if (rc) {
                debug_unregister_view(cf_diag_dbg, &debug_sprintf_view);
                debug_unregister(cf_diag_dbg);
                pr_err("Registration of PMU(cpum_cf_diag) failed with rc=%i\n",
                       rc);
        }
        return rc;
}
arch_initcall(cf_diag_init);