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 // SPDX-License-Identifier: GPL-2.0
 /*
  * Performance event support for the System z CPU-measurement Sampling Facility
  *
  * Copyright IBM Corp. 2013, 2018
  * Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
  */
 #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, "%s: freed sdbt %#lx\n", __func__,
                 (unsigned long)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, *tail_prev = NULL;
 
     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, "%s: "
                     "sampling buffer is not linked: origin %#lx"
                     " tail %#lx\n", __func__,
                     (unsigned long)sfb->sdbt,
                     (unsigned long)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_prev = tail;
             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) {
             /* Undo last SDBT. An SDBT with no SDB at its first
              * entry but with an SDBT entry instead can not be
              * handled by the interrupt handler code.
              * Avoid this situation.
              */
             if (tail_prev) {
                 sfb->num_sdbt--;
                 free_page((unsigned long) new);
                 tail = tail_prev;
             }
             break;
         }
         sfb->num_sdb++;
         tail++;
         tail_prev = new = NULL; /* Allocated at least one SBD */
     }
 
     /* Link sampling buffer to its origin */
     *tail = (unsigned long) sfb->sdbt + 1;
     sfb->tail = tail;
 
     debug_sprintf_event(sfdbg, 4, "%s: new buffer"
                 " settings: sdbt %lu sdb %lu\n", __func__,
                 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, "%s: "
             "realloc_sampling_buffer failed with rc %i\n",
             __func__, rc);
     } else
         debug_sprintf_event(sfdbg, 4,
             "%s: tear %#lx dear %#lx\n", __func__,
             (unsigned long)sfb->sdbt, (unsigned long)*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;
     size_t sample_size;
 
     /* Calculate sampling buffers using 4K pages
      *
      *    1. The sampling size is 32 bytes for basic sampling. This size
      *   is the same for all machine types. Diagnostic
      *   sampling uses auxlilary data buffer setup which provides the
      *   memory for SDBs using linux common code auxiliary trace
      *   setup.
      *
      *    2. Function alloc_sampling_buffer() sets the Alert Request
      *   Control indicator to trigger a measurement-alert to harvest
      *   sample-data-blocks (SDB). This is done per SDB. This
      *   measurement alert interrupt fires quick enough to handle
      *   one SDB, on very high frequency and work loads there might
      *   be 2 to 3 SBDs available for sample processing.
      *   Currently there is no need for setup alert request on every
      *   n-th page. This is counterproductive as one IRQ triggers
      *   a very high number of samples to be processed at one IRQ.
      *
      *    3. Use the sampling frequency as input.
      *   Compute the number of SDBs and ensure a minimum
      *   of CPUM_SF_MIN_SDB.  Depending on frequency add some more
      *   SDBs to handle a higher sampling rate.
      *   Use a minimum of CPUM_SF_MIN_SDB and allow for 100 samples
      *   (one SDB) for every 10000 HZ frequency increment.
      *
      *    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));
     n_sdb = CPUM_SF_MIN_SDB + DIV_ROUND_UP(freq, 10000);
 
     /* 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,
                 "%s: rate %lu f %lu sdb %lu/%lu"
                 " sample_size %lu cpuhw %p\n", __func__,
                 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, "%s: overflow %llu ratio %lu num %lu\n",
                 __func__, 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, "%s: realloc failed with rc %i\n",
                     __func__, rc);
 
     if (sfb_has_pending_allocs(sfb, hwc))
         debug_sprintf_event(sfdbg, 5, "%s: "
                     "req %lu alloc %lu remaining %lu\n",
                     __func__, 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,
                     "%s: initialized: cpuhw %p\n", __func__,
                     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,
                     "%s: released: cpuhw %p\n", __func__,
                     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 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, data, 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 unsigned long getrate(bool freq, unsigned long sample,
                  struct hws_qsi_info_block *si)
 {
     unsigned long rate;
 
     if (freq) {
         rate = freq_to_sample_rate(si, sample);
         rate = hw_limit_rate(si, 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, sample);
 
         /* 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) {
             debug_sprintf_event(sfdbg, 1, "%s: "
                         "Sampling rate exceeds maximum "
                         "perf sample rate\n", __func__);
             rate = 0;
         }
     }
     return rate;
 }
 
 /* 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.
  *
  * Since the CPU Measurement sampling facility can not handle frequency
  * calculate the sampling interval when frequency is specified using
  * this formula:
  *  interval := cpu_speed * 1000000 / sample_freq
  *
  * Returns errno on bad input and zero on success with parameter interval
  * set to the correct sampling rate.
  *
  * Note: This function turns off freq bit to avoid calling function
  * perf_adjust_period(). This causes frequency adjustment in the common
  * code part which causes tremendous variations in the counter values.
  */
 static int __hw_perf_event_init_rate(struct perf_event *event,
                      struct hws_qsi_info_block *si)
 {
     struct perf_event_attr *attr = &event->attr;
     struct hw_perf_event *hwc = &event->hw;
     unsigned long rate;
 
     if (attr->freq) {
         if (!attr->sample_freq)
             return -EINVAL;
         rate = getrate(attr->freq, attr->sample_freq, si);
         attr->freq = 0;     /* Don't call  perf_adjust_period() */
         SAMPL_FLAGS(hwc) |= PERF_CPUM_SF_FREQ_MODE;
     } else {
         rate = getrate(attr->freq, attr->sample_period, si);
         if (!rate)
             return -EINVAL;
     }
     attr->sample_period = rate;
     SAMPL_RATE(hwc) = rate;
     hw_init_period(hwc, SAMPL_RATE(hwc));
     debug_sprintf_event(sfdbg, 4, "%s: cpu %d period %#llx freq %d,%#lx\n",
                 __func__, event->cpu, event->attr.sample_period,
                 event->attr.freq, SAMPLE_FREQ_MODE(hwc));
     return 0;
 }
 
 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;
     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;
     }
 
     if (si.ribm & CPU_MF_SF_RIBM_NOTAV) {
         pr_warn("CPU Measurement Facility sampling is temporarily not available\n");
         err = -EBUSY;
         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;
 
     err =  __hw_perf_event_init_rate(event, &si);
     if (err)
         goto out;
 
     /* 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 bool is_callchain_event(struct perf_event *event)
 {
     u64 sample_type = event->attr.sample_type;
 
     return sample_type & (PERF_SAMPLE_CALLCHAIN | PERF_SAMPLE_REGS_USER |
                   PERF_SAMPLE_STACK_USER);
 }
 
 static int cpumsf_pmu_event_init(struct perf_event *event)
 {
     int err;
 
     /* No support for taken branch sampling */
     /* No support for callchain, stacks and registers */
     if (has_branch_stack(event) || is_callchain_event(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);
             extend_sampling_buffer(&cpuhw->sfb, hwc);
         }
         /* Rate may be adjusted with ioctl() */
         cpuhw->lsctl.interval = SAMPL_RATE(&cpuhw->event->hw);
     }
 
     /* (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, "%s: es %i cs %i ed %i cd %i "
                 "interval %#lx tear %#lx dear %#lx\n", __func__,
                 cpuhw->lsctl.es, cpuhw->lsctl.cs, cpuhw->lsctl.ed,
                 cpuhw->lsctl.cd, cpuhw->lsctl.interval,
                 cpuhw->lsctl.tear, 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 */
     err = qsi(&si);
     if (!err) {
         /* 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, "%s: qsi() failed with err %i\n",
                     __func__, 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);
 }
 
 /* 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 || sample->LS)
             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_sprintf_event(sfdbg, 4,
                         "%s: Found unknown"
                         " sampling data entry: te->f %i"
                         " basic.def %#4x (%p)\n", __func__,
                         te->f, sample->def, sample);
             /* 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, "%s: sdbt %#lx "
                     "overflow %llu timestamp %#llx\n",
                     __func__, (unsigned long)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;
     }
 
     /* 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);
 
     /* Perf_event_overflow() and perf_event_account_interrupt() limit
      * the interrupt rate to an upper limit. Roughly 1000 samples per
      * task tick.
      * Hitting this limit results in a large number
      * of throttled REF_REPORT_THROTTLE entries and the samples
      * are dropped.
      * Slightly increase the interval to avoid hitting this limit.
      */
     if (event_overflow) {
         SAMPL_RATE(hwc) += DIV_ROUND_UP(SAMPL_RATE(hwc), 10);
         debug_sprintf_event(sfdbg, 1, "%s: rate adjustment %ld\n",
                     __func__,
                     DIV_ROUND_UP(SAMPL_RATE(hwc), 10));
     }
 
     if (sampl_overflow || event_overflow)
         debug_sprintf_event(sfdbg, 4, "%s: "
                     "overflows: sample %llu event %llu"
                     " total %llu num_sdb %llu\n",
                     __func__, sampl_overflow, event_overflow,
                     OVERFLOW_REG(hwc), num_sdb);
 }
 
 #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, "%s: SDBs %ld range %ld head %ld\n",
                 __func__, i, range_scan, aux->head);
 }
 
 /*
  * 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.
      */
     debug_sprintf_event(sfdbg, 6,
                 "%s: range %ld head %ld alert %ld empty %ld\n",
                 __func__, range, aux->head, aux->alert_mark,
                 aux->empty_mark);
     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 &= ~(SDB_TE_BUFFER_FULL_MASK |
                        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, "%s: head %ld alert %ld empty %ld "
                 "index %ld tear %#lx dear %#lx\n", __func__,
                 aux->head, aux->alert_mark, aux->empty_mark,
                 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;
         *overflow = orig_overflow = te->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, idx_old;
     struct hws_trailer_entry *te;
 
     debug_sprintf_event(sfdbg, 6, "%s: range %ld head %ld alert %ld "
                 "empty %ld\n", __func__, range, aux->head,
                 aux->alert_mark, aux->empty_mark);
     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_old = 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;
 
     debug_sprintf_event(sfdbg, 6, "%s: range_scan %ld idx %ld..%ld "
                 "empty %ld\n", __func__, range_scan, idx_old,
                 idx - 1, aux->empty_mark);
     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;
     debug_sprintf_event(sfdbg, 6, "%s: #alert %ld\n", __func__,
                 size >> 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,
                         "%s: AUX buffer used up\n",
                         __func__);
             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", aux->sfb.num_sdb);
             debug_sprintf_event(sfdbg, 1, "%s: head %ld range %ld "
                         "overflow %lld\n", __func__,
                         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, "%s: head %ld alert %ld "
                         "already full, try another\n",
                         __func__,
                         aux->head, aux->alert_mark);
         }
     }
 
     if (done)
         debug_sprintf_event(sfdbg, 6, "%s: head %ld alert %ld "
                     "empty %ld\n", __func__, aux->head,
                     aux->alert_mark, aux->empty_mark);
 }
 
 /*
  * 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, "%s: SDBTs %lu\n", __func__, num_sdbt);
 }
 
 static void aux_sdb_init(unsigned long sdb)
 {
     struct hws_trailer_entry *te;
 
     te = (struct hws_trailer_entry *)trailer_entry_ptr(sdb);
 
     /* Save clock base */
     te->clock_base = 1;
     te->progusage2 = tod_clock_base.tod;
 }
 
 /*
  * aux_buffer_setup() - Setup AUX buffer for diagnostic mode sampling
  * @event:  Event the buffer is setup for, event->cpu == -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(struct perf_event *event, 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 = kzalloc(sizeof(struct aux_buffer), GFP_KERNEL);
     if (!aux)
         goto no_aux;
     sfb = &aux->sfb;
 
     /* Allocate sdbt_index for fast reference */
     n_sdbt = DIV_ROUND_UP(nr_pages, 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];
         aux_sdb_init((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, "%s: SDBTs %lu SDBs %lu\n", __func__,
                 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 */
 }
 
 /* Check if the new sampling period/freqeuncy is appropriate.
  *
  * Return non-zero on error and zero on passed checks.
  */
 static int cpumsf_pmu_check_period(struct perf_event *event, u64 value)
 {
     struct hws_qsi_info_block si;
     unsigned long rate;
     bool do_freq;
 
     memset(&si, 0, sizeof(si));
     if (event->cpu == -1) {
         if (qsi(&si))
             return -ENODEV;
     } else {
         /* Event is pinned to a particular CPU, retrieve the per-CPU
          * sampling structure for accessing the CPU-specific QSI.
          */
         struct cpu_hw_sf *cpuhw = &per_cpu(cpu_hw_sf, event->cpu);
 
         si = cpuhw->qsi;
     }
 
     do_freq = !!SAMPLE_FREQ_MODE(&event->hw);
     rate = getrate(do_freq, value, &si);
     if (!rate)
         return -EINVAL;
 
     event->attr.sample_period = rate;
     SAMPL_RATE(&event->hw) = rate;
     hw_init_period(&event->hw, SAMPL_RATE(&event->hw));
     debug_sprintf_event(sfdbg, 4, "%s:"
                 " cpu %d value %#llx period %#llx freq %d\n",
                 __func__, event->cpu, value,
                 event->attr.sample_period, do_freq);
     return 0;
 }
 
 /* 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;
         TEAR_REG(&event->hw) = (unsigned long) 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);
 
 /* Attribute list for CPU_SF.
  *
  * The availablitiy depends on the CPU_MF sampling facility authorization
  * for basic + diagnositic samples. This is determined at initialization
  * time by the sampling facility device driver.
  * If the authorization for basic samples is turned off, it should be
  * also turned off for diagnostic sampling.
  *
  * During initialization of the device driver, check the authorization
  * level for diagnostic sampling and installs the attribute
  * file for diagnostic sampling if necessary.
  *
  * For now install a placeholder to reference all possible attributes:
  * SF_CYCLES_BASIC and SF_CYCLES_BASIC_DIAG.
  * Add another entry for the final NULL pointer.
  */
 enum {
     SF_CYCLES_BASIC_ATTR_IDX = 0,
     SF_CYCLES_BASIC_DIAG_ATTR_IDX,
     SF_CYCLES_ATTR_MAX
 };
 
 static struct attribute *cpumsf_pmu_events_attr[SF_CYCLES_ATTR_MAX + 1] = {
     [SF_CYCLES_BASIC_ATTR_IDX] = CPUMF_EVENT_PTR(SF, SF_CYCLES_BASIC)
 };
 
 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,
 
     .check_period = cpumsf_pmu_check_period,
 };
 
 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, "%s: alert %#x\n", __func__,
                     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 %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 %#x\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);
         /* Sampling of diagnostic data authorized,
          * install event into attribute list of PMU device.
          */
         cpumsf_pmu_events_attr[SF_CYCLES_BASIC_DIAG_ATTR_IDX] =
             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");
         return -ENOMEM;
     }
     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);
         debug_unregister(sfdbg);
         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);
         debug_unregister(sfdbg);
         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, 0644);

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