// SPDX-License-Identifier: GPL-2.0
/*
 * Performance event support for s390x - CPU-measurement Counter Facility
 *
 *  Copyright IBM Corp. 2012, 2019
 *  Author(s): Hendrik Brueckner <brueckner@linux.ibm.com>
 */
#define KMSG_COMPONENT  "cpum_cf"
#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 <asm/cpu_mcf.h>

static enum cpumf_ctr_set get_counter_set(u64 event)
{
        int set = CPUMF_CTR_SET_MAX;

        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 < 288)
                set = CPUMF_CTR_SET_EXT;
        else if (event >= 448 && event < 496)
                set = CPUMF_CTR_SET_MT_DIAG;

        return set;
}

static int validate_ctr_version(const struct hw_perf_event *hwc)
{
        struct cpu_cf_events *cpuhw;
        int err = 0;
        u16 mtdiag_ctl;

        cpuhw = &get_cpu_var(cpu_cf_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:
                if ((cpuhw->info.csvn >= 1 && cpuhw->info.csvn <= 5 &&
                     hwc->config > 79) ||
                    (cpuhw->info.csvn >= 6 && hwc->config > 83))
                        err = -EOPNOTSUPP;
                break;
        case CPUMF_CTR_SET_EXT:
                if (cpuhw->info.csvn < 1)
                        err = -EOPNOTSUPP;
                if ((cpuhw->info.csvn == 1 && hwc->config > 159) ||
                    (cpuhw->info.csvn == 2 && hwc->config > 175) ||
                    (cpuhw->info.csvn >= 3 && cpuhw->info.csvn <= 5
                     && hwc->config > 255) ||
                    (cpuhw->info.csvn >= 6 && hwc->config > 287))
                        err = -EOPNOTSUPP;
                break;
        case CPUMF_CTR_SET_MT_DIAG:
                if (cpuhw->info.csvn <= 3)
                        err = -EOPNOTSUPP;
                /*
                 * MT-diagnostic counters are read-only.  The counter set
                 * is automatically enabled and activated on all CPUs with
                 * multithreading (SMT).  Deactivation of multithreading
                 * also disables the counter set.  State changes are ignored
                 * by lcctl().  Because Linux controls SMT enablement through
                 * a kernel parameter only, the counter set is either disabled
                 * or enabled and active.
                 *
                 * Thus, the counters can only be used if SMT is on and the
                 * counter set is enabled and active.
                 */
                mtdiag_ctl = cpumf_ctr_ctl[CPUMF_CTR_SET_MT_DIAG];
                if (!((cpuhw->info.auth_ctl & mtdiag_ctl) &&
                      (cpuhw->info.enable_ctl & mtdiag_ctl) &&
                      (cpuhw->info.act_ctl & mtdiag_ctl)))
                        err = -EOPNOTSUPP;
                break;
        }

        put_cpu_var(cpu_cf_events);
        return err;
}

static int validate_ctr_auth(const struct hw_perf_event *hwc)
{
        struct cpu_cf_events *cpuhw;
        u64 ctrs_state;
        int err = 0;

        cpuhw = &get_cpu_var(cpu_cf_events);

        /* Check authorization for cpu counter sets.
         * If the particular CPU counter set is not authorized,
         * return with -ENOENT in order to fall back to other
         * PMUs that might suffice the event request.
         */
        ctrs_state = cpumf_ctr_ctl[hwc->config_base];
        if (!(ctrs_state & cpuhw->info.auth_ctl))
                err = -ENOENT;

        put_cpu_var(cpu_cf_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_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_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=%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 cpumf_pmu_disable(struct pmu *pmu)
{
        struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_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=%x\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);

/* 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)
                        __kernel_cpumcf_end();
                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, unsigned int type)
{
        struct perf_event_attr *attr = &event->attr;
        struct hw_perf_event *hwc = &event->hw;
        enum cpumf_ctr_set set;
        int err = 0;
        u64 ev;

        switch (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:
                if (is_sampling_event(event))   /* No sampling support */
                        return -ENOENT;
                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 -ENOENT;

        /* Obtain the counter set to which the specified counter belongs */
        set = get_counter_set(ev);
        switch (set) {
        case CPUMF_CTR_SET_BASIC:
        case CPUMF_CTR_SET_USER:
        case CPUMF_CTR_SET_CRYPTO:
        case CPUMF_CTR_SET_EXT:
        case CPUMF_CTR_SET_MT_DIAG:
                /*
                 * Use the hardware perf event structure to store the
                 * counter number in the 'config' member and the counter
                 * set number in the 'config_base'.  The counter set number
                 * is then later used to enable/disable the counter(s).
                 */
                hwc->config = ev;
                hwc->config_base = set;
                break;
        case CPUMF_CTR_SET_MAX:
                /* The counter could not be associated to a counter set */
                return -EINVAL;
        };

        /* 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 && __kernel_cpumcf_begin())
                        err = -EBUSY;
                else
                        atomic_inc(&num_events);
                mutex_unlock(&pmc_reserve_mutex);
        }
        if (err)
                return err;
        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)
{
        unsigned int type = event->attr.type;
        int err;

        if (type == PERF_TYPE_HARDWARE || type == PERF_TYPE_RAW)
                err = __hw_perf_event_init(event, type);
        else if (event->pmu->type == type)
                /* Registered as unknown PMU */
                err = __hw_perf_event_init(event, PERF_TYPE_RAW);
        else
                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 void 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)
                        return;
        } 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);
}

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_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_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_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_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_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_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->txn_flags & PERF_PMU_TXN_ADD))
                if (validate_ctr_auth(&event->hw))
                        return -ENOENT;

        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_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_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.
 *
 * We only support PERF_PMU_TXN_ADD transactions. Save the
 * transaction flags but otherwise ignore non-PERF_PMU_TXN_ADD
 * transactions.
 */
static void cpumf_pmu_start_txn(struct pmu *pmu, unsigned int txn_flags)
{
        struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);

        WARN_ON_ONCE(cpuhw->txn_flags);         /* txn already in flight */

        cpuhw->txn_flags = txn_flags;
        if (txn_flags & ~PERF_PMU_TXN_ADD)
                return;

        perf_pmu_disable(pmu);
        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)
{
        unsigned int txn_flags;
        struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);

        WARN_ON_ONCE(!cpuhw->txn_flags);        /* no txn in flight */

        txn_flags = cpuhw->txn_flags;
        cpuhw->txn_flags = 0;
        if (txn_flags & ~PERF_PMU_TXN_ADD)
                return;

        WARN_ON(cpuhw->tx_state != cpuhw->state);

        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_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);
        u64 state;

        WARN_ON_ONCE(!cpuhw->txn_flags);        /* no txn in flight */

        if (cpuhw->txn_flags & ~PERF_PMU_TXN_ADD) {
                cpuhw->txn_flags = 0;
                return 0;
        }

        /* 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 -ENOENT;

        cpuhw->txn_flags = 0;
        perf_pmu_enable(pmu);
        return 0;
}

/* Performance monitoring unit for s390x */
static struct pmu cpumf_pmu = {
        .task_ctx_nr  = perf_sw_context,
        .capabilities = PERF_PMU_CAP_NO_INTERRUPT,
        .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 __init cpumf_pmu_init(void)
{
        int rc;

        if (!kernel_cpumcf_avail())
                return -ENODEV;

        cpumf_pmu.attr_groups = cpumf_cf_event_group();
        rc = perf_pmu_register(&cpumf_pmu, "cpum_cf", -1);
        if (rc)
                pr_err("Registering the cpum_cf PMU failed with rc=%i\n", rc);
        return rc;
}
subsys_initcall(cpumf_pmu_init);