mmc: core: prepend 0x to OCR entry in sysfs

[mirror_ubuntu-bionic-kernel.git] / arch / s390 / kernel / perf_cpum_sf.c

/*
 * Performance event support for the System z CPU-measurement Sampling Facility
 *
 * Copyright IBM Corp. 2013
 * 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_sf"
#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/pid.h>
#include <linux/notifier.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/moduleparam.h>
#include <asm/cpu_mf.h>
#include <asm/irq.h>
#include <asm/debug.h>
#include <asm/timex.h>

/* Minimum number of sample-data-block-tables:
 * At least one table is required for the sampling buffer structure.
 * A single table contains up to 511 pointers to sample-data-blocks.
 */
#define CPUM_SF_MIN_SDBT        1

/* Number of sample-data-blocks per sample-data-block-table (SDBT):
 * A table contains SDB pointers (8 bytes) and one table-link entry
 * that points to the origin of the next SDBT.
 */
#define CPUM_SF_SDB_PER_TABLE   ((PAGE_SIZE - 8) / 8)

/* Maximum page offset for an SDBT table-link entry:
 * If this page offset is reached, a table-link entry to the next SDBT
 * must be added.
 */
#define CPUM_SF_SDBT_TL_OFFSET  (CPUM_SF_SDB_PER_TABLE * 8)
static inline int require_table_link(const void *sdbt)
{
        return ((unsigned long) sdbt & ~PAGE_MASK) == CPUM_SF_SDBT_TL_OFFSET;
}

/* Minimum and maximum sampling buffer sizes:
 *
 * This number represents the maximum size of the sampling buffer taking
 * the number of sample-data-block-tables into account.  Note that these
 * numbers apply to the basic-sampling function only.
 * The maximum number of SDBs is increased by CPUM_SF_SDB_DIAG_FACTOR if
 * the diagnostic-sampling function is active.
 *
 * Sampling buffer size         Buffer characteristics
 * ---------------------------------------------------
 *       64KB               ==    16 pages (4KB per page)
 *                                 1 page  for SDB-tables
 *                                15 pages for SDBs
 *
 *  32MB                    ==  8192 pages (4KB per page)
 *                                16 pages for SDB-tables
 *                              8176 pages for SDBs
 */
static unsigned long __read_mostly CPUM_SF_MIN_SDB = 15;
static unsigned long __read_mostly CPUM_SF_MAX_SDB = 8176;
static unsigned long __read_mostly CPUM_SF_SDB_DIAG_FACTOR = 1;

struct sf_buffer {
        unsigned long    *sdbt;     /* Sample-data-block-table origin */
        /* buffer characteristics (required for buffer increments) */
        unsigned long  num_sdb;     /* Number of sample-data-blocks */
        unsigned long num_sdbt;     /* Number of sample-data-block-tables */
        unsigned long    *tail;     /* last sample-data-block-table */
};

struct aux_buffer {
        struct sf_buffer sfb;
        unsigned long head;        /* index of SDB of buffer head */
        unsigned long alert_mark;  /* index of SDB of alert request position */
        unsigned long empty_mark;  /* mark of SDB not marked full */
        unsigned long *sdb_index;  /* SDB address for fast lookup */
        unsigned long *sdbt_index; /* SDBT address for fast lookup */
};

struct cpu_hw_sf {
        /* CPU-measurement sampling information block */
        struct hws_qsi_info_block qsi;
        /* CPU-measurement sampling control block */
        struct hws_lsctl_request_block lsctl;
        struct sf_buffer sfb;       /* Sampling buffer */
        unsigned int flags;         /* Status flags */
        struct perf_event *event;   /* Scheduled perf event */
        struct perf_output_handle handle; /* AUX buffer output handle */
};
static DEFINE_PER_CPU(struct cpu_hw_sf, cpu_hw_sf);

/* Debug feature */
static debug_info_t *sfdbg;

/*
 * sf_disable() - Switch off sampling facility
 */
static int sf_disable(void)
{
        struct hws_lsctl_request_block sreq;

        memset(&sreq, 0, sizeof(sreq));
        return lsctl(&sreq);
}

/*
 * sf_buffer_available() - Check for an allocated sampling buffer
 */
static int sf_buffer_available(struct cpu_hw_sf *cpuhw)
{
        return !!cpuhw->sfb.sdbt;
}

/*
 * deallocate sampling facility buffer
 */
static void free_sampling_buffer(struct sf_buffer *sfb)
{
        unsigned long *sdbt, *curr;

        if (!sfb->sdbt)
                return;

        sdbt = sfb->sdbt;
        curr = sdbt;

        /* Free the SDBT after all SDBs are processed... */
        while (1) {
                if (!*curr || !sdbt)
                        break;

                /* Process table-link entries */
                if (is_link_entry(curr)) {
                        curr = get_next_sdbt(curr);
                        if (sdbt)
                                free_page((unsigned long) sdbt);

                        /* If the origin is reached, sampling buffer is freed */
                        if (curr == sfb->sdbt)
                                break;
                        else
                                sdbt = curr;
                } else {
                        /* Process SDB pointer */
                        if (*curr) {
                                free_page(*curr);
                                curr++;
                        }
                }
        }

        debug_sprintf_event(sfdbg, 5,
                            "free_sampling_buffer: freed sdbt=%p\n", sfb->sdbt);
        memset(sfb, 0, sizeof(*sfb));
}

static int alloc_sample_data_block(unsigned long *sdbt, gfp_t gfp_flags)
{
        unsigned long sdb, *trailer;

        /* Allocate and initialize sample-data-block */
        sdb = get_zeroed_page(gfp_flags);
        if (!sdb)
                return -ENOMEM;
        trailer = trailer_entry_ptr(sdb);
        *trailer = SDB_TE_ALERT_REQ_MASK;

        /* Link SDB into the sample-data-block-table */
        *sdbt = sdb;

        return 0;
}

/*
 * realloc_sampling_buffer() - extend sampler memory
 *
 * Allocates new sample-data-blocks and adds them to the specified sampling
 * buffer memory.
 *
 * Important: This modifies the sampling buffer and must be called when the
 *            sampling facility is disabled.
 *
 * Returns zero on success, non-zero otherwise.
 */
static int realloc_sampling_buffer(struct sf_buffer *sfb,
                                   unsigned long num_sdb, gfp_t gfp_flags)
{
        int i, rc;
        unsigned long *new, *tail;

        if (!sfb->sdbt || !sfb->tail)
                return -EINVAL;

        if (!is_link_entry(sfb->tail))
                return -EINVAL;

        /* Append to the existing sampling buffer, overwriting the table-link
         * register.
         * The tail variables always points to the "tail" (last and table-link)
         * entry in an SDB-table.
         */
        tail = sfb->tail;

        /* Do a sanity check whether the table-link entry points to
         * the sampling buffer origin.
         */
        if (sfb->sdbt != get_next_sdbt(tail)) {
                debug_sprintf_event(sfdbg, 3, "realloc_sampling_buffer: "
                                    "sampling buffer is not linked: origin=%p"
                                    "tail=%p\n",
                                    (void *) sfb->sdbt, (void *) tail);
                return -EINVAL;
        }

        /* Allocate remaining SDBs */
        rc = 0;
        for (i = 0; i < num_sdb; i++) {
                /* Allocate a new SDB-table if it is full. */
                if (require_table_link(tail)) {
                        new = (unsigned long *) get_zeroed_page(gfp_flags);
                        if (!new) {
                                rc = -ENOMEM;
                                break;
                        }
                        sfb->num_sdbt++;
                        /* Link current page to tail of chain */
                        *tail = (unsigned long)(void *) new + 1;
                        tail = new;
                }

                /* Allocate a new sample-data-block.
                 * If there is not enough memory, stop the realloc process
                 * and simply use what was allocated.  If this is a temporary
                 * issue, a new realloc call (if required) might succeed.
                 */
                rc = alloc_sample_data_block(tail, gfp_flags);
                if (rc)
                        break;
                sfb->num_sdb++;
                tail++;
        }

        /* Link sampling buffer to its origin */
        *tail = (unsigned long) sfb->sdbt + 1;
        sfb->tail = tail;

        debug_sprintf_event(sfdbg, 4, "realloc_sampling_buffer: new buffer"
                            " settings: sdbt=%lu sdb=%lu\n",
                            sfb->num_sdbt, sfb->num_sdb);
        return rc;
}

/*
 * allocate_sampling_buffer() - allocate sampler memory
 *
 * Allocates and initializes a sampling buffer structure using the
 * specified number of sample-data-blocks (SDB).  For each allocation,
 * a 4K page is used.  The number of sample-data-block-tables (SDBT)
 * are calculated from SDBs.
 * Also set the ALERT_REQ mask in each SDBs trailer.
 *
 * Returns zero on success, non-zero otherwise.
 */
static int alloc_sampling_buffer(struct sf_buffer *sfb, unsigned long num_sdb)
{
        int rc;

        if (sfb->sdbt)
                return -EINVAL;

        /* Allocate the sample-data-block-table origin */
        sfb->sdbt = (unsigned long *) get_zeroed_page(GFP_KERNEL);
        if (!sfb->sdbt)
                return -ENOMEM;
        sfb->num_sdb = 0;
        sfb->num_sdbt = 1;

        /* Link the table origin to point to itself to prepare for
         * realloc_sampling_buffer() invocation.
         */
        sfb->tail = sfb->sdbt;
        *sfb->tail = (unsigned long)(void *) sfb->sdbt + 1;

        /* Allocate requested number of sample-data-blocks */
        rc = realloc_sampling_buffer(sfb, num_sdb, GFP_KERNEL);
        if (rc) {
                free_sampling_buffer(sfb);
                debug_sprintf_event(sfdbg, 4, "alloc_sampling_buffer: "
                        "realloc_sampling_buffer failed with rc=%i\n", rc);
        } else
                debug_sprintf_event(sfdbg, 4,
                        "alloc_sampling_buffer: tear=%p dear=%p\n",
                        sfb->sdbt, (void *) *sfb->sdbt);
        return rc;
}

static void sfb_set_limits(unsigned long min, unsigned long max)
{
        struct hws_qsi_info_block si;

        CPUM_SF_MIN_SDB = min;
        CPUM_SF_MAX_SDB = max;

        memset(&si, 0, sizeof(si));
        if (!qsi(&si))
                CPUM_SF_SDB_DIAG_FACTOR = DIV_ROUND_UP(si.dsdes, si.bsdes);
}

static unsigned long sfb_max_limit(struct hw_perf_event *hwc)
{
        return SAMPL_DIAG_MODE(hwc) ? CPUM_SF_MAX_SDB * CPUM_SF_SDB_DIAG_FACTOR
                                    : CPUM_SF_MAX_SDB;
}

static unsigned long sfb_pending_allocs(struct sf_buffer *sfb,
                                        struct hw_perf_event *hwc)
{
        if (!sfb->sdbt)
                return SFB_ALLOC_REG(hwc);
        if (SFB_ALLOC_REG(hwc) > sfb->num_sdb)
                return SFB_ALLOC_REG(hwc) - sfb->num_sdb;
        return 0;
}

static int sfb_has_pending_allocs(struct sf_buffer *sfb,
                                   struct hw_perf_event *hwc)
{
        return sfb_pending_allocs(sfb, hwc) > 0;
}

static void sfb_account_allocs(unsigned long num, struct hw_perf_event *hwc)
{
        /* Limit the number of SDBs to not exceed the maximum */
        num = min_t(unsigned long, num, sfb_max_limit(hwc) - SFB_ALLOC_REG(hwc));
        if (num)
                SFB_ALLOC_REG(hwc) += num;
}

static void sfb_init_allocs(unsigned long num, struct hw_perf_event *hwc)
{
        SFB_ALLOC_REG(hwc) = 0;
        sfb_account_allocs(num, hwc);
}

static void deallocate_buffers(struct cpu_hw_sf *cpuhw)
{
        if (cpuhw->sfb.sdbt)
                free_sampling_buffer(&cpuhw->sfb);
}

static int allocate_buffers(struct cpu_hw_sf *cpuhw, struct hw_perf_event *hwc)
{
        unsigned long n_sdb, freq, factor;
        size_t sample_size;

        /* Calculate sampling buffers using 4K pages
         *
         *    1. Determine the sample data size which depends on the used
         *       sampling functions, for example, basic-sampling or
         *       basic-sampling with diagnostic-sampling.
         *
         *    2. Use the sampling frequency as input.  The sampling buffer is
         *       designed for almost one second.  This can be adjusted through
         *       the "factor" variable.
         *       In any case, alloc_sampling_buffer() sets the Alert Request
         *       Control indicator to trigger a measurement-alert to harvest
         *       sample-data-blocks (sdb).
         *
         *    3. Compute the number of sample-data-blocks and ensure a minimum
         *       of CPUM_SF_MIN_SDB.  Also ensure the upper limit does not
         *       exceed a "calculated" maximum.  The symbolic maximum is
         *       designed for basic-sampling only and needs to be increased if
         *       diagnostic-sampling is active.
         *       See also the remarks for these symbolic constants.
         *
         *    4. Compute the number of sample-data-block-tables (SDBT) and
         *       ensure a minimum of CPUM_SF_MIN_SDBT (one table can manage up
         *       to 511 SDBs).
         */
        sample_size = sizeof(struct hws_basic_entry);
        freq = sample_rate_to_freq(&cpuhw->qsi, SAMPL_RATE(hwc));
        factor = 1;
        n_sdb = DIV_ROUND_UP(freq, factor * ((PAGE_SIZE-64) / sample_size));
        if (n_sdb < CPUM_SF_MIN_SDB)
                n_sdb = CPUM_SF_MIN_SDB;

        /* If there is already a sampling buffer allocated, it is very likely
         * that the sampling facility is enabled too.  If the event to be
         * initialized requires a greater sampling buffer, the allocation must
         * be postponed.  Changing the sampling buffer requires the sampling
         * facility to be in the disabled state.  So, account the number of
         * required SDBs and let cpumsf_pmu_enable() resize the buffer just
         * before the event is started.
         */
        sfb_init_allocs(n_sdb, hwc);
        if (sf_buffer_available(cpuhw))
                return 0;

        debug_sprintf_event(sfdbg, 3,
                            "allocate_buffers: rate=%lu f=%lu sdb=%lu/%lu"
                            " sample_size=%lu cpuhw=%p\n",
                            SAMPL_RATE(hwc), freq, n_sdb, sfb_max_limit(hwc),
                            sample_size, cpuhw);

        return alloc_sampling_buffer(&cpuhw->sfb,
                                     sfb_pending_allocs(&cpuhw->sfb, hwc));
}

static unsigned long min_percent(unsigned int percent, unsigned long base,
                                 unsigned long min)
{
        return min_t(unsigned long, min, DIV_ROUND_UP(percent * base, 100));
}

static unsigned long compute_sfb_extent(unsigned long ratio, unsigned long base)
{
        /* Use a percentage-based approach to extend the sampling facility
         * buffer.  Accept up to 5% sample data loss.
         * Vary the extents between 1% to 5% of the current number of
         * sample-data-blocks.
         */
        if (ratio <= 5)
                return 0;
        if (ratio <= 25)
                return min_percent(1, base, 1);
        if (ratio <= 50)
                return min_percent(1, base, 1);
        if (ratio <= 75)
                return min_percent(2, base, 2);
        if (ratio <= 100)
                return min_percent(3, base, 3);
        if (ratio <= 250)
                return min_percent(4, base, 4);

        return min_percent(5, base, 8);
}

static void sfb_account_overflows(struct cpu_hw_sf *cpuhw,
                                  struct hw_perf_event *hwc)
{
        unsigned long ratio, num;

        if (!OVERFLOW_REG(hwc))
                return;

        /* The sample_overflow contains the average number of sample data
         * that has been lost because sample-data-blocks were full.
         *
         * Calculate the total number of sample data entries that has been
         * discarded.  Then calculate the ratio of lost samples to total samples
         * per second in percent.
         */
        ratio = DIV_ROUND_UP(100 * OVERFLOW_REG(hwc) * cpuhw->sfb.num_sdb,
                             sample_rate_to_freq(&cpuhw->qsi, SAMPL_RATE(hwc)));

        /* Compute number of sample-data-blocks */
        num = compute_sfb_extent(ratio, cpuhw->sfb.num_sdb);
        if (num)
                sfb_account_allocs(num, hwc);

        debug_sprintf_event(sfdbg, 5, "sfb: overflow: overflow=%llu ratio=%lu"
                            " num=%lu\n", OVERFLOW_REG(hwc), ratio, num);
        OVERFLOW_REG(hwc) = 0;
}

/* extend_sampling_buffer() - Extend sampling buffer
 * @sfb:        Sampling buffer structure (for local CPU)
 * @hwc:        Perf event hardware structure
 *
 * Use this function to extend the sampling buffer based on the overflow counter
 * and postponed allocation extents stored in the specified Perf event hardware.
 *
 * Important: This function disables the sampling facility in order to safely
 *            change the sampling buffer structure.  Do not call this function
 *            when the PMU is active.
 */
static void extend_sampling_buffer(struct sf_buffer *sfb,
                                   struct hw_perf_event *hwc)
{
        unsigned long num, num_old;
        int rc;

        num = sfb_pending_allocs(sfb, hwc);
        if (!num)
                return;
        num_old = sfb->num_sdb;

        /* Disable the sampling facility to reset any states and also
         * clear pending measurement alerts.
         */
        sf_disable();

        /* Extend the sampling buffer.
         * This memory allocation typically happens in an atomic context when
         * called by perf.  Because this is a reallocation, it is fine if the
         * new SDB-request cannot be satisfied immediately.
         */
        rc = realloc_sampling_buffer(sfb, num, GFP_ATOMIC);
        if (rc)
                debug_sprintf_event(sfdbg, 5, "sfb: extend: realloc "
                                    "failed with rc=%i\n", rc);

        if (sfb_has_pending_allocs(sfb, hwc))
                debug_sprintf_event(sfdbg, 5, "sfb: extend: "
                                    "req=%lu alloc=%lu remaining=%lu\n",
                                    num, sfb->num_sdb - num_old,
                                    sfb_pending_allocs(sfb, hwc));
}


/* Number of perf events counting hardware events */
static atomic_t num_events;
/* Used to avoid races in calling reserve/release_cpumf_hardware */
static DEFINE_MUTEX(pmc_reserve_mutex);

#define PMC_INIT      0
#define PMC_RELEASE   1
#define PMC_FAILURE   2
static void setup_pmc_cpu(void *flags)
{
        int err;
        struct cpu_hw_sf *cpusf = this_cpu_ptr(&cpu_hw_sf);

        err = 0;
        switch (*((int *) flags)) {
        case PMC_INIT:
                memset(cpusf, 0, sizeof(*cpusf));
                err = qsi(&cpusf->qsi);
                if (err)
                        break;
                cpusf->flags |= PMU_F_RESERVED;
                err = sf_disable();
                if (err)
                        pr_err("Switching off the sampling facility failed "
                               "with rc=%i\n", err);
                debug_sprintf_event(sfdbg, 5,
                                    "setup_pmc_cpu: initialized: cpuhw=%p\n", cpusf);
                break;
        case PMC_RELEASE:
                cpusf->flags &= ~PMU_F_RESERVED;
                err = sf_disable();
                if (err) {
                        pr_err("Switching off the sampling facility failed "
                               "with rc=%i\n", err);
                } else
                        deallocate_buffers(cpusf);
                debug_sprintf_event(sfdbg, 5,
                                    "setup_pmc_cpu: released: cpuhw=%p\n", cpusf);
                break;
        }
        if (err)
                *((int *) flags) |= PMC_FAILURE;
}

static void release_pmc_hardware(void)
{
        int flags = PMC_RELEASE;

        irq_subclass_unregister(IRQ_SUBCLASS_MEASUREMENT_ALERT);
        on_each_cpu(setup_pmc_cpu, &flags, 1);
}

static int reserve_pmc_hardware(void)
{
        int flags = PMC_INIT;

        on_each_cpu(setup_pmc_cpu, &flags, 1);
        if (flags & PMC_FAILURE) {
                release_pmc_hardware();
                return -ENODEV;
        }
        irq_subclass_register(IRQ_SUBCLASS_MEASUREMENT_ALERT);

        return 0;
}

static void hw_perf_event_destroy(struct perf_event *event)
{
        /* Release PMC if this is the last perf 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);
        }
}

static void hw_init_period(struct hw_perf_event *hwc, u64 period)
{
        hwc->sample_period = period;
        hwc->last_period = hwc->sample_period;
        local64_set(&hwc->period_left, hwc->sample_period);
}

static void hw_reset_registers(struct hw_perf_event *hwc,
                               unsigned long *sdbt_origin)
{
        /* (Re)set to first sample-data-block-table */
        TEAR_REG(hwc) = (unsigned long) sdbt_origin;
}

static unsigned long hw_limit_rate(const struct hws_qsi_info_block *si,
                                   unsigned long rate)
{
        return clamp_t(unsigned long, rate,
                       si->min_sampl_rate, si->max_sampl_rate);
}

static u32 cpumsf_pid_type(struct perf_event *event,
                           u32 pid, enum pid_type type)
{
        struct task_struct *tsk;

        /* Idle process */
        if (!pid)
                goto out;

        tsk = find_task_by_pid_ns(pid, &init_pid_ns);
        pid = -1;
        if (tsk) {
                /*
                 * Only top level events contain the pid namespace in which
                 * they are created.
                 */
                if (event->parent)
                        event = event->parent;
                pid = __task_pid_nr_ns(tsk, type, event->ns);
                /*
                 * See also 1d953111b648
                 * "perf/core: Don't report zero PIDs for exiting tasks".
                 */
                if (!pid && !pid_alive(tsk))
                        pid = -1;
        }
out:
        return pid;
}

static void cpumsf_output_event_pid(struct perf_event *event,
                                    struct perf_sample_data *data,
                                    struct pt_regs *regs)
{
        u32 pid;
        struct perf_event_header header;
        struct perf_output_handle handle;

        /*
         * Obtain the PID from the basic-sampling data entry and
         * correct the data->tid_entry.pid value.
         */
        pid = data->tid_entry.pid;

        /* Protect callchain buffers, tasks */
        rcu_read_lock();

        perf_prepare_sample(&header, data, event, regs);
        if (perf_output_begin(&handle, event, header.size))
                goto out;

        /* Update the process ID (see also kernel/events/core.c) */
        data->tid_entry.pid = cpumsf_pid_type(event, pid, __PIDTYPE_TGID);
        data->tid_entry.tid = cpumsf_pid_type(event, pid, PIDTYPE_PID);

        perf_output_sample(&handle, &header, data, event);
        perf_output_end(&handle);
out:
        rcu_read_unlock();
}

static int __hw_perf_event_init(struct perf_event *event)
{
        struct cpu_hw_sf *cpuhw;
        struct hws_qsi_info_block si;
        struct perf_event_attr *attr = &event->attr;
        struct hw_perf_event *hwc = &event->hw;
        unsigned long rate;
        int cpu, err;

        /* Reserve CPU-measurement sampling facility */
        err = 0;
        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;

        if (err)
                goto out;

        /* Access per-CPU sampling information (query sampling info) */
        /*
         * The event->cpu value can be -1 to count on every CPU, for example,
         * when attaching to a task.  If this is specified, use the query
         * sampling info from the current CPU, otherwise use event->cpu to
         * retrieve the per-CPU information.
         * Later, cpuhw indicates whether to allocate sampling buffers for a
         * particular CPU (cpuhw!=NULL) or each online CPU (cpuw==NULL).
         */
        memset(&si, 0, sizeof(si));
        cpuhw = NULL;
        if (event->cpu == -1)
                qsi(&si);
        else {
                /* Event is pinned to a particular CPU, retrieve the per-CPU
                 * sampling structure for accessing the CPU-specific QSI.
                 */
                cpuhw = &per_cpu(cpu_hw_sf, event->cpu);
                si = cpuhw->qsi;
        }

        /* Check sampling facility authorization and, if not authorized,
         * fall back to other PMUs.  It is safe to check any CPU because
         * the authorization is identical for all configured CPUs.
         */
        if (!si.as) {
                err = -ENOENT;
                goto out;
        }

        /* Always enable basic sampling */
        SAMPL_FLAGS(hwc) = PERF_CPUM_SF_BASIC_MODE;

        /* Check if diagnostic sampling is requested.  Deny if the required
         * sampling authorization is missing.
         */
        if (attr->config == PERF_EVENT_CPUM_SF_DIAG) {
                if (!si.ad) {
                        err = -EPERM;
                        goto out;
                }
                SAMPL_FLAGS(hwc) |= PERF_CPUM_SF_DIAG_MODE;
        }

        /* Check and set other sampling flags */
        if (attr->config1 & PERF_CPUM_SF_FULL_BLOCKS)
                SAMPL_FLAGS(hwc) |= PERF_CPUM_SF_FULL_BLOCKS;

        /* The sampling information (si) contains information about the
         * min/max sampling intervals and the CPU speed.  So calculate the
         * correct sampling interval and avoid the whole period adjust
         * feedback loop.
         */
        rate = 0;
        if (attr->freq) {
                rate = freq_to_sample_rate(&si, attr->sample_freq);
                rate = hw_limit_rate(&si, rate);
                attr->freq = 0;
                attr->sample_period = rate;
        } else {
                /* The min/max sampling rates specifies the valid range
                 * of sample periods.  If the specified sample period is
                 * out of range, limit the period to the range boundary.
                 */
                rate = hw_limit_rate(&si, hwc->sample_period);

                /* The perf core maintains a maximum sample rate that is
                 * configurable through the sysctl interface.  Ensure the
                 * sampling rate does not exceed this value.  This also helps
                 * to avoid throttling when pushing samples with
                 * perf_event_overflow().
                 */
                if (sample_rate_to_freq(&si, rate) >
                      sysctl_perf_event_sample_rate) {
                        err = -EINVAL;
                        debug_sprintf_event(sfdbg, 1, "Sampling rate exceeds maximum perf sample rate\n");
                        goto out;
                }
        }
        SAMPL_RATE(hwc) = rate;
        hw_init_period(hwc, SAMPL_RATE(hwc));

        /* Initialize sample data overflow accounting */
        hwc->extra_reg.reg = REG_OVERFLOW;
        OVERFLOW_REG(hwc) = 0;

        /* Use AUX buffer. No need to allocate it by ourself */
        if (attr->config == PERF_EVENT_CPUM_SF_DIAG)
                return 0;

        /* Allocate the per-CPU sampling buffer using the CPU information
         * from the event.  If the event is not pinned to a particular
         * CPU (event->cpu == -1; or cpuhw == NULL), allocate sampling
         * buffers for each online CPU.
         */
        if (cpuhw)
                /* Event is pinned to a particular CPU */
                err = allocate_buffers(cpuhw, hwc);
        else {
                /* Event is not pinned, allocate sampling buffer on
                 * each online CPU
                 */
                for_each_online_cpu(cpu) {
                        cpuhw = &per_cpu(cpu_hw_sf, cpu);
                        err = allocate_buffers(cpuhw, hwc);
                        if (err)
                                break;
                }
        }

        /* If PID/TID sampling is active, replace the default overflow
         * handler to extract and resolve the PIDs from the basic-sampling
         * data entries.
         */
        if (event->attr.sample_type & PERF_SAMPLE_TID)
                if (is_default_overflow_handler(event))
                        event->overflow_handler = cpumsf_output_event_pid;
out:
        return err;
}

static int cpumsf_pmu_event_init(struct perf_event *event)
{
        int err;

        /* No support for taken branch sampling */
        if (has_branch_stack(event))
                return -EOPNOTSUPP;

        switch (event->attr.type) {
        case PERF_TYPE_RAW:
                if ((event->attr.config != PERF_EVENT_CPUM_SF) &&
                    (event->attr.config != PERF_EVENT_CPUM_SF_DIAG))
                        return -ENOENT;
                break;
        case PERF_TYPE_HARDWARE:
                /* Support sampling of CPU cycles in addition to the
                 * counter facility.  However, the counter facility
                 * is more precise and, hence, restrict this PMU to
                 * sampling events only.
                 */
                if (event->attr.config != PERF_COUNT_HW_CPU_CYCLES)
                        return -ENOENT;
                if (!is_sampling_event(event))
                        return -ENOENT;
                break;
        default:
                return -ENOENT;
        }

        /* Check online status of the CPU to which the event is pinned */
        if (event->cpu >= 0 && !cpu_online(event->cpu))
                        return -ENODEV;

        /* Force reset of idle/hv excludes regardless of what the
         * user requested.
         */
        if (event->attr.exclude_hv)
                event->attr.exclude_hv = 0;
        if (event->attr.exclude_idle)
                event->attr.exclude_idle = 0;

        err = __hw_perf_event_init(event);
        if (unlikely(err))
                if (event->destroy)
                        event->destroy(event);
        return err;
}

static void cpumsf_pmu_enable(struct pmu *pmu)
{
        struct cpu_hw_sf *cpuhw = this_cpu_ptr(&cpu_hw_sf);
        struct hw_perf_event *hwc;
        int err;

        if (cpuhw->flags & PMU_F_ENABLED)
                return;

        if (cpuhw->flags & PMU_F_ERR_MASK)
                return;

        /* Check whether to extent the sampling buffer.
         *
         * Two conditions trigger an increase of the sampling buffer for a
         * perf event:
         *    1. Postponed buffer allocations from the event initialization.
         *    2. Sampling overflows that contribute to pending allocations.
         *
         * Note that the extend_sampling_buffer() function disables the sampling
         * facility, but it can be fully re-enabled using sampling controls that
         * have been saved in cpumsf_pmu_disable().
         */
        if (cpuhw->event) {
                hwc = &cpuhw->event->hw;
                if (!(SAMPL_DIAG_MODE(hwc))) {
                        /*
                         * Account number of overflow-designated
                         * buffer extents
                         */
                        sfb_account_overflows(cpuhw, hwc);
                        if (sfb_has_pending_allocs(&cpuhw->sfb, hwc))
                                extend_sampling_buffer(&cpuhw->sfb, hwc);
                }
        }

        /* (Re)enable the PMU and sampling facility */
        cpuhw->flags |= PMU_F_ENABLED;
        barrier();

        err = lsctl(&cpuhw->lsctl);
        if (err) {
                cpuhw->flags &= ~PMU_F_ENABLED;
                pr_err("Loading sampling controls failed: op=%i err=%i\n",
                        1, err);
                return;
        }

        /* Load current program parameter */
        lpp(&S390_lowcore.lpp);

        debug_sprintf_event(sfdbg, 6, "pmu_enable: es=%i cs=%i ed=%i cd=%i "
                            "tear=%p dear=%p\n", cpuhw->lsctl.es, cpuhw->lsctl.cs,
                            cpuhw->lsctl.ed, cpuhw->lsctl.cd,
                            (void *) cpuhw->lsctl.tear, (void *) cpuhw->lsctl.dear);
}

static void cpumsf_pmu_disable(struct pmu *pmu)
{
        struct cpu_hw_sf *cpuhw = this_cpu_ptr(&cpu_hw_sf);
        struct hws_lsctl_request_block inactive;
        struct hws_qsi_info_block si;
        int err;

        if (!(cpuhw->flags & PMU_F_ENABLED))
                return;

        if (cpuhw->flags & PMU_F_ERR_MASK)
                return;

        /* Switch off sampling activation control */
        inactive = cpuhw->lsctl;
        inactive.cs = 0;
        inactive.cd = 0;

        err = lsctl(&inactive);
        if (err) {
                pr_err("Loading sampling controls failed: op=%i err=%i\n",
                        2, err);
                return;
        }

        /* Save state of TEAR and DEAR register contents */
        if (!qsi(&si)) {
                /* TEAR/DEAR values are valid only if the sampling facility is
                 * enabled.  Note that cpumsf_pmu_disable() might be called even
                 * for a disabled sampling facility because cpumsf_pmu_enable()
                 * controls the enable/disable state.
                 */
                if (si.es) {
                        cpuhw->lsctl.tear = si.tear;
                        cpuhw->lsctl.dear = si.dear;
                }
        } else
                debug_sprintf_event(sfdbg, 3, "cpumsf_pmu_disable: "
                                    "qsi() failed with err=%i\n", err);

        cpuhw->flags &= ~PMU_F_ENABLED;
}

/* perf_exclude_event() - Filter event
 * @event:      The perf event
 * @regs:       pt_regs structure
 * @sde_regs:   Sample-data-entry (sde) regs structure
 *
 * Filter perf events according to their exclude specification.
 *
 * Return non-zero if the event shall be excluded.
 */
static int perf_exclude_event(struct perf_event *event, struct pt_regs *regs,
                              struct perf_sf_sde_regs *sde_regs)
{
        if (event->attr.exclude_user && user_mode(regs))
                return 1;
        if (event->attr.exclude_kernel && !user_mode(regs))
                return 1;
        if (event->attr.exclude_guest && sde_regs->in_guest)
                return 1;
        if (event->attr.exclude_host && !sde_regs->in_guest)
                return 1;
        return 0;
}

/* perf_push_sample() - Push samples to perf
 * @event:      The perf event
 * @sample:     Hardware sample data
 *
 * Use the hardware sample data to create perf event sample.  The sample
 * is the 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 perf_push_sample(struct perf_event *event,
                            struct hws_basic_entry *basic)
{
        int overflow;
        struct pt_regs regs;
        struct perf_sf_sde_regs *sde_regs;
        struct perf_sample_data data;

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

        /* Setup pt_regs to look like an CPU-measurement external interrupt
         * using the Program Request Alert code.  The regs.int_parm_long
         * field which is unused contains additional sample-data-entry related
         * indicators.
         */
        memset(&regs, 0, sizeof(regs));
        regs.int_code = 0x1407;
        regs.int_parm = CPU_MF_INT_SF_PRA;
        sde_regs = (struct perf_sf_sde_regs *) &regs.int_parm_long;

        psw_bits(regs.psw).ia   = basic->ia;
        psw_bits(regs.psw).dat  = basic->T;
        psw_bits(regs.psw).wait = basic->W;
        psw_bits(regs.psw).pstate = basic->P;
        psw_bits(regs.psw).as   = basic->AS;

        /*
         * Use the hardware provided configuration level to decide if the
         * sample belongs to a guest or host. If that is not available,
         * fall back to the following heuristics:
         * A non-zero guest program parameter always indicates a guest
         * sample. Some early samples or samples from guests without
         * lpp usage would be misaccounted to the host. We use the asn
         * value as an addon heuristic to detect most of these guest samples.
         * If the value differs from 0xffff (the host value), we assume to
         * be a KVM guest.
         */
        switch (basic->CL) {
        case 1: /* logical partition */
                sde_regs->in_guest = 0;
                break;
        case 2: /* virtual machine */
                sde_regs->in_guest = 1;
                break;
        default: /* old machine, use heuristics */
                if (basic->gpp || basic->prim_asn != 0xffff)
                        sde_regs->in_guest = 1;
                break;
        }

        /*
         * Store the PID value from the sample-data-entry to be
         * processed and resolved by cpumsf_output_event_pid().
         */
        data.tid_entry.pid = basic->hpp & LPP_PID_MASK;

        overflow = 0;
        if (perf_exclude_event(event, &regs, sde_regs))
                goto out;
        if (perf_event_overflow(event, &data, &regs)) {
                overflow = 1;
                event->pmu->stop(event, 0);
        }
        perf_event_update_userpage(event);
out:
        return overflow;
}

static void perf_event_count_update(struct perf_event *event, u64 count)
{
        local64_add(count, &event->count);
}

static void debug_sample_entry(struct hws_basic_entry *sample,
                               struct hws_trailer_entry *te)
{
        debug_sprintf_event(sfdbg, 4, "hw_collect_samples: Found unknown "
                            "sampling data entry: te->f=%i basic.def=%04x (%p)\n",
                            te->f, sample->def, sample);
}

/* hw_collect_samples() - Walk through a sample-data-block and collect samples
 * @event:      The perf event
 * @sdbt:       Sample-data-block table
 * @overflow:   Event overflow counter
 *
 * Walks through a sample-data-block and collects sampling data entries that are
 * then pushed to the perf event subsystem.  Depending on the sampling function,
 * there can be either basic-sampling or combined-sampling data entries.  A
 * combined-sampling data entry consists of a basic- and a diagnostic-sampling
 * data entry.  The sampling function is determined by the flags in the perf
 * event hardware structure.  The function always works with a combined-sampling
 * data entry but ignores the the diagnostic portion if it is not available.
 *
 * Note that the implementation focuses on basic-sampling data entries and, if
 * such an entry is not valid, the entire combined-sampling data entry is
 * ignored.
 *
 * The overflow variables counts the number of samples that has been discarded
 * due to a perf event overflow.
 */
static void hw_collect_samples(struct perf_event *event, unsigned long *sdbt,
                               unsigned long long *overflow)
{
        struct hws_trailer_entry *te;
        struct hws_basic_entry *sample;

        te = (struct hws_trailer_entry *) trailer_entry_ptr(*sdbt);
        sample = (struct hws_basic_entry *) *sdbt;
        while ((unsigned long *) sample < (unsigned long *) te) {
                /* Check for an empty sample */
                if (!sample->def)
                        break;

                /* Update perf event period */
                perf_event_count_update(event, SAMPL_RATE(&event->hw));

                /* Check whether sample is valid */
                if (sample->def == 0x0001) {
                        /* If an event overflow occurred, the PMU is stopped to
                         * throttle event delivery.  Remaining sample data is
                         * discarded.
                         */
                        if (!*overflow) {
                                /* Check whether sample is consistent */
                                if (sample->I == 0 && sample->W == 0) {
                                        /* Deliver sample data to perf */
                                        *overflow = perf_push_sample(event,
                                                                     sample);
                                }
                        } else
                                /* Count discarded samples */
                                *overflow += 1;
                } else {
                        debug_sample_entry(sample, te);
                        /* Sample slot is not yet written or other record.
                         *
                         * This condition can occur if the buffer was reused
                         * from a combined basic- and diagnostic-sampling.
                         * If only basic-sampling is then active, entries are
                         * written into the larger diagnostic entries.
                         * This is typically the case for sample-data-blocks
                         * that are not full.  Stop processing if the first
                         * invalid format was detected.
                         */
                        if (!te->f)
                                break;
                }

                /* Reset sample slot and advance to next sample */
                sample->def = 0;
                sample++;
        }
}

/* hw_perf_event_update() - Process sampling buffer
 * @event:      The perf event
 * @flush_all:  Flag to also flush partially filled sample-data-blocks
 *
 * Processes the sampling buffer and create perf event samples.
 * The sampling buffer position are retrieved and saved in the TEAR_REG
 * register of the specified perf event.
 *
 * Only full sample-data-blocks are processed.  Specify the flash_all flag
 * to also walk through partially filled sample-data-blocks.  It is ignored
 * if PERF_CPUM_SF_FULL_BLOCKS is set.  The PERF_CPUM_SF_FULL_BLOCKS flag
 * enforces the processing of full sample-data-blocks only (trailer entries
 * with the block-full-indicator bit set).
 */
static void hw_perf_event_update(struct perf_event *event, int flush_all)
{
        struct hw_perf_event *hwc = &event->hw;
        struct hws_trailer_entry *te;
        unsigned long *sdbt;
        unsigned long long event_overflow, sampl_overflow, num_sdb, te_flags;
        int done;

        /*
         * AUX buffer is used when in diagnostic sampling mode.
         * No perf events/samples are created.
         */
        if (SAMPL_DIAG_MODE(&event->hw))
                return;

        if (flush_all && SDB_FULL_BLOCKS(hwc))
                flush_all = 0;

        sdbt = (unsigned long *) TEAR_REG(hwc);
        done = event_overflow = sampl_overflow = num_sdb = 0;
        while (!done) {
                /* Get the trailer entry of the sample-data-block */
                te = (struct hws_trailer_entry *) trailer_entry_ptr(*sdbt);

                /* Leave loop if no more work to do (block full indicator) */
                if (!te->f) {
                        done = 1;
                        if (!flush_all)
                                break;
                }

                /* Check the sample overflow count */
                if (te->overflow)
                        /* Account sample overflows and, if a particular limit
                         * is reached, extend the sampling buffer.
                         * For details, see sfb_account_overflows().
                         */
                        sampl_overflow += te->overflow;

                /* Timestamps are valid for full sample-data-blocks only */
                debug_sprintf_event(sfdbg, 6, "hw_perf_event_update: sdbt=%p "
                                    "overflow=%llu timestamp=0x%llx\n",
                                    sdbt, te->overflow,
                                    (te->f) ? trailer_timestamp(te) : 0ULL);

                /* Collect all samples from a single sample-data-block and
                 * flag if an (perf) event overflow happened.  If so, the PMU
                 * is stopped and remaining samples will be discarded.
                 */
                hw_collect_samples(event, sdbt, &event_overflow);
                num_sdb++;

                /* Reset trailer (using compare-double-and-swap) */
                do {
                        te_flags = te->flags & ~SDB_TE_BUFFER_FULL_MASK;
                        te_flags |= SDB_TE_ALERT_REQ_MASK;
                } while (!cmpxchg_double(&te->flags, &te->overflow,
                                         te->flags, te->overflow,
                                         te_flags, 0ULL));

                /* Advance to next sample-data-block */
                sdbt++;
                if (is_link_entry(sdbt))
                        sdbt = get_next_sdbt(sdbt);

                /* Update event hardware registers */
                TEAR_REG(hwc) = (unsigned long) sdbt;

                /* Stop processing sample-data if all samples of the current
                 * sample-data-block were flushed even if it was not full.
                 */
                if (flush_all && done)
                        break;

                /* If an event overflow happened, discard samples by
                 * processing any remaining sample-data-blocks.
                 */
                if (event_overflow)
                        flush_all = 1;
        }

        /* Account sample overflows in the event hardware structure */
        if (sampl_overflow)
                OVERFLOW_REG(hwc) = DIV_ROUND_UP(OVERFLOW_REG(hwc) +
                                                 sampl_overflow, 1 + num_sdb);
        if (sampl_overflow || event_overflow)
                debug_sprintf_event(sfdbg, 4, "hw_perf_event_update: "
                                    "overflow stats: sample=%llu event=%llu\n",
                                    sampl_overflow, event_overflow);
}

#define AUX_SDB_INDEX(aux, i) ((i) % aux->sfb.num_sdb)
#define AUX_SDB_NUM(aux, start, end) (end >= start ? end - start + 1 : 0)
#define AUX_SDB_NUM_ALERT(aux) AUX_SDB_NUM(aux, aux->head, aux->alert_mark)
#define AUX_SDB_NUM_EMPTY(aux) AUX_SDB_NUM(aux, aux->head, aux->empty_mark)

/*
 * Get trailer entry by index of SDB.
 */
static struct hws_trailer_entry *aux_sdb_trailer(struct aux_buffer *aux,
                                                 unsigned long index)
{
        unsigned long sdb;

        index = AUX_SDB_INDEX(aux, index);
        sdb = aux->sdb_index[index];
        return (struct hws_trailer_entry *)trailer_entry_ptr(sdb);
}

/*
 * Finish sampling on the cpu. Called by cpumsf_pmu_del() with pmu
 * disabled. Collect the full SDBs in AUX buffer which have not reached
 * the point of alert indicator. And ignore the SDBs which are not
 * full.
 *
 * 1. Scan SDBs to see how much data is there and consume them.
 * 2. Remove alert indicator in the buffer.
 */
static void aux_output_end(struct perf_output_handle *handle)
{
        unsigned long i, range_scan, idx;
        struct aux_buffer *aux;
        struct hws_trailer_entry *te;

        aux = perf_get_aux(handle);
        if (!aux)
                return;

        range_scan = AUX_SDB_NUM_ALERT(aux);
        for (i = 0, idx = aux->head; i < range_scan; i++, idx++) {
                te = aux_sdb_trailer(aux, idx);
                if (!(te->flags & SDB_TE_BUFFER_FULL_MASK))
                        break;
        }
        /* i is num of SDBs which are full */
        perf_aux_output_end(handle, i << PAGE_SHIFT);

        /* Remove alert indicators in the buffer */
        te = aux_sdb_trailer(aux, aux->alert_mark);
        te->flags &= ~SDB_TE_ALERT_REQ_MASK;

        debug_sprintf_event(sfdbg, 6, "aux_output_end: collect %lx SDBs\n", i);
}

/*
 * Start sampling on the CPU. Called by cpumsf_pmu_add() when an event
 * is first added to the CPU or rescheduled again to the CPU. It is called
 * with pmu disabled.
 *
 * 1. Reset the trailer of SDBs to get ready for new data.
 * 2. Tell the hardware where to put the data by reset the SDBs buffer
 *    head(tear/dear).
 */
static int aux_output_begin(struct perf_output_handle *handle,
                            struct aux_buffer *aux,
                            struct cpu_hw_sf *cpuhw)
{
        unsigned long range;
        unsigned long i, range_scan, idx;
        unsigned long head, base, offset;
        struct hws_trailer_entry *te;

        if (WARN_ON_ONCE(handle->head & ~PAGE_MASK))
                return -EINVAL;

        aux->head = handle->head >> PAGE_SHIFT;
        range = (handle->size + 1) >> PAGE_SHIFT;
        if (range <= 1)
                return -ENOMEM;

        /*
         * SDBs between aux->head and aux->empty_mark are already ready
         * for new data. range_scan is num of SDBs not within them.
         */
        if (range > AUX_SDB_NUM_EMPTY(aux)) {
                range_scan = range - AUX_SDB_NUM_EMPTY(aux);
                idx = aux->empty_mark + 1;
                for (i = 0; i < range_scan; i++, idx++) {
                        te = aux_sdb_trailer(aux, idx);
                        te->flags = te->flags & ~SDB_TE_BUFFER_FULL_MASK;
                        te->flags = te->flags & ~SDB_TE_ALERT_REQ_MASK;
                        te->overflow = 0;
                }
                /* Save the position of empty SDBs */
                aux->empty_mark = aux->head + range - 1;
        }

        /* Set alert indicator */
        aux->alert_mark = aux->head + range/2 - 1;
        te = aux_sdb_trailer(aux, aux->alert_mark);
        te->flags = te->flags | SDB_TE_ALERT_REQ_MASK;

        /* Reset hardware buffer head */
        head = AUX_SDB_INDEX(aux, aux->head);
        base = aux->sdbt_index[head / CPUM_SF_SDB_PER_TABLE];
        offset = head % CPUM_SF_SDB_PER_TABLE;
        cpuhw->lsctl.tear = base + offset * sizeof(unsigned long);
        cpuhw->lsctl.dear = aux->sdb_index[head];

        debug_sprintf_event(sfdbg, 6, "aux_output_begin: "
                            "head->alert_mark->empty_mark (num_alert, range)"
                            "[%lx -> %lx -> %lx] (%lx, %lx) "
                            "tear index %lx, tear %lx dear %lx\n",
                            aux->head, aux->alert_mark, aux->empty_mark,
                            AUX_SDB_NUM_ALERT(aux), range,
                            head / CPUM_SF_SDB_PER_TABLE,
                            cpuhw->lsctl.tear,
                            cpuhw->lsctl.dear);

        return 0;
}

/*
 * Set alert indicator on SDB at index @alert_index while sampler is running.
 *
 * Return true if successfully.
 * Return false if full indicator is already set by hardware sampler.
 */
static bool aux_set_alert(struct aux_buffer *aux, unsigned long alert_index,
                          unsigned long long *overflow)
{
        unsigned long long orig_overflow, orig_flags, new_flags;
        struct hws_trailer_entry *te;

        te = aux_sdb_trailer(aux, alert_index);
        do {
                orig_flags = te->flags;
                orig_overflow = te->overflow;
                *overflow = orig_overflow;
                if (orig_flags & SDB_TE_BUFFER_FULL_MASK) {
                        /*
                         * SDB is already set by hardware.
                         * Abort and try to set somewhere
                         * behind.
                         */
                        return false;
                }
                new_flags = orig_flags | SDB_TE_ALERT_REQ_MASK;
        } while (!cmpxchg_double(&te->flags, &te->overflow,
                                 orig_flags, orig_overflow,
                                 new_flags, 0ULL));
        return true;
}

/*
 * aux_reset_buffer() - Scan and setup SDBs for new samples
 * @aux:        The AUX buffer to set
 * @range:      The range of SDBs to scan started from aux->head
 * @overflow:   Set to overflow count
 *
 * Set alert indicator on the SDB at index of aux->alert_mark. If this SDB is
 * marked as empty, check if it is already set full by the hardware sampler.
 * If yes, that means new data is already there before we can set an alert
 * indicator. Caller should try to set alert indicator to some position behind.
 *
 * Scan the SDBs in AUX buffer from behind aux->empty_mark. They are used
 * previously and have already been consumed by user space. Reset these SDBs
 * (clear full indicator and alert indicator) for new data.
 * If aux->alert_mark fall in this area, just set it. Overflow count is
 * recorded while scanning.
 *
 * SDBs between aux->head and aux->empty_mark are already reset at last time.
 * and ready for new samples. So scanning on this area could be skipped.
 *
 * Return true if alert indicator is set successfully and false if not.
 */
static bool aux_reset_buffer(struct aux_buffer *aux, unsigned long range,
                             unsigned long long *overflow)
{
        unsigned long long orig_overflow, orig_flags, new_flags;
        unsigned long i, range_scan, idx;
        struct hws_trailer_entry *te;

        if (range <= AUX_SDB_NUM_EMPTY(aux))
                /*
                 * No need to scan. All SDBs in range are marked as empty.
                 * Just set alert indicator. Should check race with hardware
                 * sampler.
                 */
                return aux_set_alert(aux, aux->alert_mark, overflow);

        if (aux->alert_mark <= aux->empty_mark)
                /*
                 * Set alert indicator on empty SDB. Should check race
                 * with hardware sampler.
                 */
                if (!aux_set_alert(aux, aux->alert_mark, overflow))
                        return false;

        /*
         * Scan the SDBs to clear full and alert indicator used previously.
         * Start scanning from one SDB behind empty_mark. If the new alert
         * indicator fall into this range, set it.
         */
        range_scan = range - AUX_SDB_NUM_EMPTY(aux);
        idx = aux->empty_mark + 1;
        for (i = 0; i < range_scan; i++, idx++) {
                te = aux_sdb_trailer(aux, idx);
                do {
                        orig_flags = te->flags;
                        orig_overflow = te->overflow;
                        new_flags = orig_flags & ~SDB_TE_BUFFER_FULL_MASK;
                        if (idx == aux->alert_mark)
                                new_flags |= SDB_TE_ALERT_REQ_MASK;
                        else
                                new_flags &= ~SDB_TE_ALERT_REQ_MASK;
                } while (!cmpxchg_double(&te->flags, &te->overflow,
                                         orig_flags, orig_overflow,
                                         new_flags, 0ULL));
                *overflow += orig_overflow;
        }

        /* Update empty_mark to new position */
        aux->empty_mark = aux->head + range - 1;

        return true;
}

/*
 * Measurement alert handler for diagnostic mode sampling.
 */
static void hw_collect_aux(struct cpu_hw_sf *cpuhw)
{
        struct aux_buffer *aux;
        int done = 0;
        unsigned long range = 0, size;
        unsigned long long overflow = 0;
        struct perf_output_handle *handle = &cpuhw->handle;
        unsigned long num_sdb;

        aux = perf_get_aux(handle);
        if (WARN_ON_ONCE(!aux))
                return;

        /* Inform user space new data arrived */
        size = AUX_SDB_NUM_ALERT(aux) << PAGE_SHIFT;
        perf_aux_output_end(handle, size);
        num_sdb = aux->sfb.num_sdb;

        while (!done) {
                /* Get an output handle */
                aux = perf_aux_output_begin(handle, cpuhw->event);
                if (handle->size == 0) {
                        pr_err("The AUX buffer with %lu pages for the "
                               "diagnostic-sampling mode is full\n",
                                num_sdb);
                        debug_sprintf_event(sfdbg, 1, "AUX buffer used up\n");
                        break;
                }
                if (WARN_ON_ONCE(!aux))
                        return;

                /* Update head and alert_mark to new position */
                aux->head = handle->head >> PAGE_SHIFT;
                range = (handle->size + 1) >> PAGE_SHIFT;
                if (range == 1)
                        aux->alert_mark = aux->head;
                else
                        aux->alert_mark = aux->head + range/2 - 1;

                if (aux_reset_buffer(aux, range, &overflow)) {
                        if (!overflow) {
                                done = 1;
                                break;
                        }
                        size = range << PAGE_SHIFT;
                        perf_aux_output_end(&cpuhw->handle, size);
                        pr_err("Sample data caused the AUX buffer with %lu "
                               "pages to overflow\n", num_sdb);
                        debug_sprintf_event(sfdbg, 1, "head %lx range %lx "
                                            "overflow %llx\n",
                                            aux->head, range, overflow);
                } else {
                        size = AUX_SDB_NUM_ALERT(aux) << PAGE_SHIFT;
                        perf_aux_output_end(&cpuhw->handle, size);
                        debug_sprintf_event(sfdbg, 6, "head %lx alert %lx "
                                            "already full, try another\n",
                                            aux->head, aux->alert_mark);
                }
        }

        if (done)
                debug_sprintf_event(sfdbg, 6, "aux_reset_buffer: "
                                    "[%lx -> %lx -> %lx] (%lx, %lx)\n",
                                    aux->head, aux->alert_mark, aux->empty_mark,
                                    AUX_SDB_NUM_ALERT(aux), range);
}

/*
 * Callback when freeing AUX buffers.
 */
static void aux_buffer_free(void *data)
{
        struct aux_buffer *aux = data;
        unsigned long i, num_sdbt;

        if (!aux)
                return;

        /* Free SDBT. SDB is freed by the caller */
        num_sdbt = aux->sfb.num_sdbt;
        for (i = 0; i < num_sdbt; i++)
                free_page(aux->sdbt_index[i]);

        kfree(aux->sdbt_index);
        kfree(aux->sdb_index);
        kfree(aux);

        debug_sprintf_event(sfdbg, 4, "aux_buffer_free: free "
                            "%lu SDBTs\n", num_sdbt);
}

/*
 * aux_buffer_setup() - Setup AUX buffer for diagnostic mode sampling
 * @cpu:        On which to allocate, -1 means current
 * @pages:      Array of pointers to buffer pages passed from perf core
 * @nr_pages:   Total pages
 * @snapshot:   Flag for snapshot mode
 *
 * This is the callback when setup an event using AUX buffer. Perf tool can
 * trigger this by an additional mmap() call on the event. Unlike the buffer
 * for basic samples, AUX buffer belongs to the event. It is scheduled with
 * the task among online cpus when it is a per-thread event.
 *
 * Return the private AUX buffer structure if success or NULL if fails.
 */
static void *aux_buffer_setup(int cpu, void **pages, int nr_pages,
                              bool snapshot)
{
        struct sf_buffer *sfb;
        struct aux_buffer *aux;
        unsigned long *new, *tail;
        int i, n_sdbt;

        if (!nr_pages || !pages)
                return NULL;

        if (nr_pages > CPUM_SF_MAX_SDB * CPUM_SF_SDB_DIAG_FACTOR) {
                pr_err("AUX buffer size (%i pages) is larger than the "
                       "maximum sampling buffer limit\n",
                       nr_pages);
                return NULL;
        } else if (nr_pages < CPUM_SF_MIN_SDB * CPUM_SF_SDB_DIAG_FACTOR) {
                pr_err("AUX buffer size (%i pages) is less than the "
                       "minimum sampling buffer limit\n",
                       nr_pages);
                return NULL;
        }

        /* Allocate aux_buffer struct for the event */
        aux = kmalloc(sizeof(struct aux_buffer), GFP_KERNEL);
        if (!aux)
                goto no_aux;
        sfb = &aux->sfb;

        /* Allocate sdbt_index for fast reference */
        n_sdbt = (nr_pages + CPUM_SF_SDB_PER_TABLE - 1) / CPUM_SF_SDB_PER_TABLE;
        aux->sdbt_index = kmalloc_array(n_sdbt, sizeof(void *), GFP_KERNEL);
        if (!aux->sdbt_index)
                goto no_sdbt_index;

        /* Allocate sdb_index for fast reference */
        aux->sdb_index = kmalloc_array(nr_pages, sizeof(void *), GFP_KERNEL);
        if (!aux->sdb_index)
                goto no_sdb_index;

        /* Allocate the first SDBT */
        sfb->num_sdbt = 0;
        sfb->sdbt = (unsigned long *) get_zeroed_page(GFP_KERNEL);
        if (!sfb->sdbt)
                goto no_sdbt;
        aux->sdbt_index[sfb->num_sdbt++] = (unsigned long)sfb->sdbt;
        tail = sfb->tail = sfb->sdbt;

        /*
         * Link the provided pages of AUX buffer to SDBT.
         * Allocate SDBT if needed.
         */
        for (i = 0; i < nr_pages; i++, tail++) {
                if (require_table_link(tail)) {
                        new = (unsigned long *) get_zeroed_page(GFP_KERNEL);
                        if (!new)
                                goto no_sdbt;
                        aux->sdbt_index[sfb->num_sdbt++] = (unsigned long)new;
                        /* Link current page to tail of chain */
                        *tail = (unsigned long)(void *) new + 1;
                        tail = new;
                }
                /* Tail is the entry in a SDBT */
                *tail = (unsigned long)pages[i];
                aux->sdb_index[i] = (unsigned long)pages[i];
        }
        sfb->num_sdb = nr_pages;

        /* Link the last entry in the SDBT to the first SDBT */
        *tail = (unsigned long) sfb->sdbt + 1;
        sfb->tail = tail;

        /*
         * Initial all SDBs are zeroed. Mark it as empty.
         * So there is no need to clear the full indicator
         * when this event is first added.
         */
        aux->empty_mark = sfb->num_sdb - 1;

        debug_sprintf_event(sfdbg, 4, "aux_buffer_setup: setup %lu SDBTs"
                            " and %lu SDBs\n",
                            sfb->num_sdbt, sfb->num_sdb);

        return aux;

no_sdbt:
        /* SDBs (AUX buffer pages) are freed by caller */
        for (i = 0; i < sfb->num_sdbt; i++)
                free_page(aux->sdbt_index[i]);
        kfree(aux->sdb_index);
no_sdb_index:
        kfree(aux->sdbt_index);
no_sdbt_index:
        kfree(aux);
no_aux:
        return NULL;
}

static void cpumsf_pmu_read(struct perf_event *event)
{
        /* Nothing to do ... updates are interrupt-driven */
}

/* Activate sampling control.
 * Next call of pmu_enable() starts sampling.
 */
static void cpumsf_pmu_start(struct perf_event *event, int flags)
{
        struct cpu_hw_sf *cpuhw = this_cpu_ptr(&cpu_hw_sf);

        if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
                return;

        if (flags & PERF_EF_RELOAD)
                WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));

        perf_pmu_disable(event->pmu);
        event->hw.state = 0;
        cpuhw->lsctl.cs = 1;
        if (SAMPL_DIAG_MODE(&event->hw))
                cpuhw->lsctl.cd = 1;
        perf_pmu_enable(event->pmu);
}

/* Deactivate sampling control.
 * Next call of pmu_enable() stops sampling.
 */
static void cpumsf_pmu_stop(struct perf_event *event, int flags)
{
        struct cpu_hw_sf *cpuhw = this_cpu_ptr(&cpu_hw_sf);

        if (event->hw.state & PERF_HES_STOPPED)
                return;

        perf_pmu_disable(event->pmu);
        cpuhw->lsctl.cs = 0;
        cpuhw->lsctl.cd = 0;
        event->hw.state |= PERF_HES_STOPPED;

        if ((flags & PERF_EF_UPDATE) && !(event->hw.state & PERF_HES_UPTODATE)) {
                hw_perf_event_update(event, 1);
                event->hw.state |= PERF_HES_UPTODATE;
        }
        perf_pmu_enable(event->pmu);
}

static int cpumsf_pmu_add(struct perf_event *event, int flags)
{
        struct cpu_hw_sf *cpuhw = this_cpu_ptr(&cpu_hw_sf);
        struct aux_buffer *aux;
        int err;

        if (cpuhw->flags & PMU_F_IN_USE)
                return -EAGAIN;

        if (!SAMPL_DIAG_MODE(&event->hw) && !cpuhw->sfb.sdbt)
                return -EINVAL;

        err = 0;
        perf_pmu_disable(event->pmu);

        event->hw.state = PERF_HES_UPTODATE | PERF_HES_STOPPED;

        /* Set up sampling controls.  Always program the sampling register
         * using the SDB-table start.  Reset TEAR_REG event hardware register
         * that is used by hw_perf_event_update() to store the sampling buffer
         * position after samples have been flushed.
         */
        cpuhw->lsctl.s = 0;
        cpuhw->lsctl.h = 1;
        cpuhw->lsctl.interval = SAMPL_RATE(&event->hw);
        if (!SAMPL_DIAG_MODE(&event->hw)) {
                cpuhw->lsctl.tear = (unsigned long) cpuhw->sfb.sdbt;
                cpuhw->lsctl.dear = *(unsigned long *) cpuhw->sfb.sdbt;
                hw_reset_registers(&event->hw, cpuhw->sfb.sdbt);
        }

        /* Ensure sampling functions are in the disabled state.  If disabled,
         * switch on sampling enable control. */
        if (WARN_ON_ONCE(cpuhw->lsctl.es == 1 || cpuhw->lsctl.ed == 1)) {
                err = -EAGAIN;
                goto out;
        }
        if (SAMPL_DIAG_MODE(&event->hw)) {
                aux = perf_aux_output_begin(&cpuhw->handle, event);
                if (!aux) {
                        err = -EINVAL;
                        goto out;
                }
                err = aux_output_begin(&cpuhw->handle, aux, cpuhw);
                if (err)
                        goto out;
                cpuhw->lsctl.ed = 1;
        }
        cpuhw->lsctl.es = 1;

        /* Set in_use flag and store event */
        cpuhw->event = event;
        cpuhw->flags |= PMU_F_IN_USE;

        if (flags & PERF_EF_START)
                cpumsf_pmu_start(event, PERF_EF_RELOAD);
out:
        perf_event_update_userpage(event);
        perf_pmu_enable(event->pmu);
        return err;
}

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

        perf_pmu_disable(event->pmu);
        cpumsf_pmu_stop(event, PERF_EF_UPDATE);

        cpuhw->lsctl.es = 0;
        cpuhw->lsctl.ed = 0;
        cpuhw->flags &= ~PMU_F_IN_USE;
        cpuhw->event = NULL;

        if (SAMPL_DIAG_MODE(&event->hw))
                aux_output_end(&cpuhw->handle);
        perf_event_update_userpage(event);
        perf_pmu_enable(event->pmu);
}

CPUMF_EVENT_ATTR(SF, SF_CYCLES_BASIC, PERF_EVENT_CPUM_SF);
CPUMF_EVENT_ATTR(SF, SF_CYCLES_BASIC_DIAG, PERF_EVENT_CPUM_SF_DIAG);

static struct attribute *cpumsf_pmu_events_attr[] = {
        CPUMF_EVENT_PTR(SF, SF_CYCLES_BASIC),
        NULL,
        NULL,
};

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

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

static struct attribute_group cpumsf_pmu_events_group = {
        .name = "events",
        .attrs = cpumsf_pmu_events_attr,
};
static struct attribute_group cpumsf_pmu_format_group = {
        .name = "format",
        .attrs = cpumsf_pmu_format_attr,
};
static const struct attribute_group *cpumsf_pmu_attr_groups[] = {
        &cpumsf_pmu_events_group,
        &cpumsf_pmu_format_group,
        NULL,
};

static struct pmu cpumf_sampling = {
        .pmu_enable   = cpumsf_pmu_enable,
        .pmu_disable  = cpumsf_pmu_disable,

        .event_init   = cpumsf_pmu_event_init,
        .add          = cpumsf_pmu_add,
        .del          = cpumsf_pmu_del,

        .start        = cpumsf_pmu_start,
        .stop         = cpumsf_pmu_stop,
        .read         = cpumsf_pmu_read,

        .attr_groups  = cpumsf_pmu_attr_groups,

        .setup_aux    = aux_buffer_setup,
        .free_aux     = aux_buffer_free,
};

static void cpumf_measurement_alert(struct ext_code ext_code,
                                    unsigned int alert, unsigned long unused)
{
        struct cpu_hw_sf *cpuhw;

        if (!(alert & CPU_MF_INT_SF_MASK))
                return;
        inc_irq_stat(IRQEXT_CMS);
        cpuhw = this_cpu_ptr(&cpu_hw_sf);

        /* 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;

        /* The processing below must take care of multiple alert events that
         * might be indicated concurrently. */

        /* Program alert request */
        if (alert & CPU_MF_INT_SF_PRA) {
                if (cpuhw->flags & PMU_F_IN_USE)
                        if (SAMPL_DIAG_MODE(&cpuhw->event->hw))
                                hw_collect_aux(cpuhw);
                        else
                                hw_perf_event_update(cpuhw->event, 0);
                else
                        WARN_ON_ONCE(!(cpuhw->flags & PMU_F_IN_USE));
        }

        /* Report measurement alerts only for non-PRA codes */
        if (alert != CPU_MF_INT_SF_PRA)
                debug_sprintf_event(sfdbg, 6, "measurement alert: 0x%x\n", alert);

        /* Sampling authorization change request */
        if (alert & CPU_MF_INT_SF_SACA)
                qsi(&cpuhw->qsi);

        /* Loss of sample data due to high-priority machine activities */
        if (alert & CPU_MF_INT_SF_LSDA) {
                pr_err("Sample data was lost\n");
                cpuhw->flags |= PMU_F_ERR_LSDA;
                sf_disable();
        }

        /* Invalid sampling buffer entry */
        if (alert & (CPU_MF_INT_SF_IAE|CPU_MF_INT_SF_ISE)) {
                pr_err("A sampling buffer entry is incorrect (alert=0x%x)\n",
                       alert);
                cpuhw->flags |= PMU_F_ERR_IBE;
                sf_disable();
        }
}
static int cpusf_pmu_setup(unsigned int cpu, int flags)
{
        /* Ignore the notification if no events are scheduled on the PMU.
         * This might be racy...
         */
        if (!atomic_read(&num_events))
                return 0;

        local_irq_disable();
        setup_pmc_cpu(&flags);
        local_irq_enable();
        return 0;
}

static int s390_pmu_sf_online_cpu(unsigned int cpu)
{
        return cpusf_pmu_setup(cpu, PMC_INIT);
}

static int s390_pmu_sf_offline_cpu(unsigned int cpu)
{
        return cpusf_pmu_setup(cpu, PMC_RELEASE);
}

static int param_get_sfb_size(char *buffer, const struct kernel_param *kp)
{
        if (!cpum_sf_avail())
                return -ENODEV;
        return sprintf(buffer, "%lu,%lu", CPUM_SF_MIN_SDB, CPUM_SF_MAX_SDB);
}

static int param_set_sfb_size(const char *val, const struct kernel_param *kp)
{
        int rc;
        unsigned long min, max;

        if (!cpum_sf_avail())
                return -ENODEV;
        if (!val || !strlen(val))
                return -EINVAL;

        /* Valid parameter values: "min,max" or "max" */
        min = CPUM_SF_MIN_SDB;
        max = CPUM_SF_MAX_SDB;
        if (strchr(val, ','))
                rc = (sscanf(val, "%lu,%lu", &min, &max) == 2) ? 0 : -EINVAL;
        else
                rc = kstrtoul(val, 10, &max);

        if (min < 2 || min >= max || max > get_num_physpages())
                rc = -EINVAL;
        if (rc)
                return rc;

        sfb_set_limits(min, max);
        pr_info("The sampling buffer limits have changed to: "
                "min=%lu max=%lu (diag=x%lu)\n",
                CPUM_SF_MIN_SDB, CPUM_SF_MAX_SDB, CPUM_SF_SDB_DIAG_FACTOR);
        return 0;
}

#define param_check_sfb_size(name, p) __param_check(name, p, void)
static const struct kernel_param_ops param_ops_sfb_size = {
        .set = param_set_sfb_size,
        .get = param_get_sfb_size,
};

#define RS_INIT_FAILURE_QSI       0x0001
#define RS_INIT_FAILURE_BSDES     0x0002
#define RS_INIT_FAILURE_ALRT      0x0003
#define RS_INIT_FAILURE_PERF      0x0004
static void __init pr_cpumsf_err(unsigned int reason)
{
        pr_err("Sampling facility support for perf is not available: "
               "reason=%04x\n", reason);
}

static int __init init_cpum_sampling_pmu(void)
{
        struct hws_qsi_info_block si;
        int err;

        if (!cpum_sf_avail())
                return -ENODEV;

        memset(&si, 0, sizeof(si));
        if (qsi(&si)) {
                pr_cpumsf_err(RS_INIT_FAILURE_QSI);
                return -ENODEV;
        }

        if (!si.as && !si.ad)
                return -ENODEV;

        if (si.bsdes != sizeof(struct hws_basic_entry)) {
                pr_cpumsf_err(RS_INIT_FAILURE_BSDES);
                return -EINVAL;
        }

        if (si.ad) {
                sfb_set_limits(CPUM_SF_MIN_SDB, CPUM_SF_MAX_SDB);
                cpumsf_pmu_events_attr[1] =
                        CPUMF_EVENT_PTR(SF, SF_CYCLES_BASIC_DIAG);
        }

        sfdbg = debug_register(KMSG_COMPONENT, 2, 1, 80);
        if (!sfdbg)
                pr_err("Registering for s390dbf failed\n");
        debug_register_view(sfdbg, &debug_sprintf_view);

        err = register_external_irq(EXT_IRQ_MEASURE_ALERT,
                                    cpumf_measurement_alert);
        if (err) {
                pr_cpumsf_err(RS_INIT_FAILURE_ALRT);
                goto out;
        }

        err = perf_pmu_register(&cpumf_sampling, "cpum_sf", PERF_TYPE_RAW);
        if (err) {
                pr_cpumsf_err(RS_INIT_FAILURE_PERF);
                unregister_external_irq(EXT_IRQ_MEASURE_ALERT,
                                        cpumf_measurement_alert);
                goto out;
        }

        cpuhp_setup_state(CPUHP_AP_PERF_S390_SF_ONLINE, "perf/s390/sf:online",
                          s390_pmu_sf_online_cpu, s390_pmu_sf_offline_cpu);
out:
        return err;
}
arch_initcall(init_cpum_sampling_pmu);
core_param(cpum_sfb_size, CPUM_SF_MAX_SDB, sfb_size, 0640);