s390/perf: add support for the CPU-Measurement Sampling Facility

Introduce a perf PMU, "cpum_sf", to support the CPU-Measurement
Sampling Facility.  You can control the sampling facility through
this perf PMU interfaces.  Perf sampling events are created for
hardware samples.

For details about the CPU-Measurement Sampling Facility, see
"The Load-Program-Parameter and the CPU-Measurement Facilities" (SA23-2260).
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/cpu_mf.h

@@ -210,6 +210,20 @@ static inline int lsctl(struct hws_lsctl_request_block *req)
 
 /* Sampling control helper functions */
 
+#include <linux/time.h>
+
+static inline unsigned long freq_to_sample_rate(struct hws_qsi_info_block *qsi,
+						unsigned long freq)
+{
+	return (USEC_PER_SEC / freq) * qsi->cpu_speed;
+}
+
+static inline unsigned long sample_rate_to_freq(struct hws_qsi_info_block *qsi,
+						unsigned long rate)
+{
+	return USEC_PER_SEC * qsi->cpu_speed / rate;
+}
+
 #define SDB_TE_ALERT_REQ_MASK	0x4000000000000000UL
 #define SDB_TE_BUFFER_FULL_MASK 0x8000000000000000UL
 

arch/s390/include/asm/perf_event.h

@@ -15,12 +15,13 @@
 #include <linux/device.h>
 #include <asm/cpu_mf.h>
 
-/* CPU-measurement counter facility */
-#define PERF_CPUM_CF_MAX_CTR		256
-
 /* Per-CPU flags for PMU states */
 #define PMU_F_RESERVED			0x1000
 #define PMU_F_ENABLED			0x2000
+#define PMU_F_IN_USE			0x4000
+#define PMU_F_ERR_IBE			0x0100
+#define PMU_F_ERR_LSDA			0x0200
+#define PMU_F_ERR_MASK			(PMU_F_ERR_IBE|PMU_F_ERR_LSDA)
 
 /* Perf defintions for PMU event attributes in sysfs */
 extern __init const struct attribute_group **cpumf_cf_event_group(void);
@@ -41,5 +42,15 @@ extern unsigned long perf_instruction_pointer(struct pt_regs *regs);
 extern unsigned long perf_misc_flags(struct pt_regs *regs);
 #define perf_misc_flags(regs) perf_misc_flags(regs)
 
+/* Perf PMU definitions for the counter facility */
+#define PERF_CPUM_CF_MAX_CTR		256
+
+/* Perf PMU definitions for the sampling facility */
+#define PERF_CPUM_SF_MAX_CTR		1
+#define PERF_EVENT_CPUM_SF		0xB0000UL	/* Raw event ID */
+
+#define TEAR_REG(hwc)		((hwc)->last_tag)
+#define SAMPL_RATE(hwc)		((hwc)->event_base)
+
 #endif /* CONFIG_64BIT */
 #endif /* _ASM_S390_PERF_EVENT_H */

arch/s390/kernel/Makefile

@@ -60,7 +60,7 @@ obj-$(CONFIG_FTRACE_SYSCALLS)  += ftrace.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 
 ifdef CONFIG_64BIT
-obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_cpum_cf.o \
+obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_cpum_cf.o perf_cpum_sf.o \
 						perf_cpum_cf_events.o
 obj-y				+= runtime_instr.o cache.o
 endif

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/notifier.h>
+#include <linux/export.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
+
+/* Minimum number of sample-data-blocks:
+ * The minimum designates a single page for sample-data-block, i.e.,
+ * up to 126 sample-data-blocks with a size of 32 bytes (bsdes).
+ */
+#define CPUM_SF_MIN_SDB	    126
+
+/* Maximum number of sample-data-blocks:
+ * The maximum number designates approx. 256K per CPU including
+ * the given number of sample-data-blocks and taking the number
+ * of sample-data-block tables into account.
+ *
+ * Later, this number can be increased for extending the sampling
+ * buffer, for example, by factor 2 (512K) or 4 (1M).
+ */
+#define CPUM_SF_MAX_SDB	    6471
+
+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	 tail;	    /* last sample-data-block-table */
+};
+
+struct cpu_hw_sf {
+	/* CPU-measurement sampling information block */
+	struct hws_qsi_info_block qsi;
+	struct hws_lsctl_request_block lsctl;
+	struct sf_buffer sfb;	    /* Sampling buffer */
+	unsigned int flags;	    /* Status flags */
+	struct perf_event *event;   /* Scheduled perf event */
+};
+static DEFINE_PER_CPU(struct cpu_hw_sf, cpu_hw_sf);
+
+/* Debug feature */
+static debug_info_t *sfdbg;
+
+/*
+ * sf_buffer_available() - Check for an allocated sampling buffer
+ */
+static int sf_buffer_available(struct cpu_hw_sf *cpuhw)
+{
+	return (cpuhw->sfb.sdbt) ? 1 : 0;
+}
+
+/*
+ * 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 = (unsigned long *) sdbt;
+
+	/* we'll free the SDBT after all SDBs are processed... */
+	while (1) {
+		if (!*curr || !sdbt)
+			break;
+
+		/* watch for link entry reset if found */
+		if (is_link_entry(curr)) {
+			curr = get_next_sdbt(curr);
+			if (sdbt)
+				free_page(sdbt);
+
+			/* we are done if we reach the origin */
+			if ((unsigned long) curr == sfb->sdbt)
+				break;
+			else
+				sdbt = (unsigned long) curr;
+		} else {
+			/* process SDB pointer */
+			if (*curr) {
+				free_page(*curr);
+				curr++;
+			}
+		}
+	}
+
+	debug_sprintf_event(sfdbg, 5,
+			    "free_sampling_buffer: freed sdbt=%0lx\n", sfb->sdbt);
+	memset(sfb, 0, sizeof(*sfb));
+}
+
+/*
+ * 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 j, k, rc;
+	unsigned long *sdbt, *tail, *trailer;
+	unsigned long sdb;
+	unsigned long num_sdbt, sdb_per_table;
+
+	if (sfb->sdbt)
+		return -EINVAL;
+	sfb->num_sdb = 0;
+
+	/* Compute the number of required sample-data-block-tables (SDBT) */
+	num_sdbt = num_sdb / ((PAGE_SIZE - 8) / 8);
+	if (num_sdbt < CPUM_SF_MIN_SDBT)
+		num_sdbt = CPUM_SF_MIN_SDBT;
+	sdb_per_table = (PAGE_SIZE - 8) / 8;
+
+	debug_sprintf_event(sfdbg, 4, "alloc_sampling_buffer: num_sdbt=%lu "
+			    "num_sdb=%lu sdb_per_table=%lu\n",
+			    num_sdbt, num_sdb, sdb_per_table);
+	sdbt = NULL;
+	tail = sdbt;
+
+	for (j = 0; j < num_sdbt; j++) {
+		sdbt = (unsigned long *) get_zeroed_page(GFP_KERNEL);
+		if (!sdbt) {
+			rc = -ENOMEM;
+			goto allocate_sdbt_error;
+		}
+
+		/* save origin of sample-data-block-table */
+		if (!sfb->sdbt)
+			sfb->sdbt = (unsigned long) sdbt;
+
+		/* link current page to tail of chain */
+		if (tail)
+			*tail = (unsigned long)(void *) sdbt + 1;
+
+		for (k = 0; k < num_sdb && k < sdb_per_table; k++) {
+			/* get and set SDB page */
+			sdb = get_zeroed_page(GFP_KERNEL);
+			if (!sdb) {
+				rc = -ENOMEM;
+				goto allocate_sdbt_error;
+			}
+			*sdbt = sdb;
+			trailer = trailer_entry_ptr(*sdbt);
+			*trailer = SDB_TE_ALERT_REQ_MASK;
+			sdbt++;
+		}
+		num_sdb -= k;
+		sfb->num_sdb += k;	/* count allocated sdb's */
+		tail = sdbt;
+	}
+
+	rc = 0;
+	if (tail)
+		*tail = sfb->sdbt + 1;
+	sfb->tail = (unsigned long) (void *)tail;
+
+allocate_sdbt_error:
+	if (rc)
+		free_sampling_buffer(sfb);
+	else
+		debug_sprintf_event(sfdbg, 4,
+			"alloc_sampling_buffer: tear=%0lx dear=%0lx\n",
+			sfb->sdbt, *(unsigned long *) sfb->sdbt);
+	return rc;
+}
+
+static int allocate_sdbt(struct cpu_hw_sf *cpuhw, const struct hw_perf_event *hwc)
+{
+	unsigned long n_sdb, freq;
+	unsigned long factor;
+
+	/* Calculate sampling buffers using 4K pages
+	 *
+	 *    1. Use frequency as input.  The samping buffer is designed for
+	 *	 a complete second.  This can be adjusted through the "factor"
+	 *	 variable.
+	 *	 In any case, alloc_sampling_buffer() sets the Alert Request
+	 *	 Control indicator to trigger measurement-alert to harvest
+	 *	 sample-data-blocks (sdb).
+	 *
+	 *    2. Compute the number of sample-data-blocks and ensure a minimum
+	 *	 of CPUM_SF_MIN_SDB.  Also ensure the upper limit does not
+	 *	 exceed CPUM_SF_MAX_SDB.  See also the remarks for these
+	 *	 symbolic constants.
+	 *
+	 *    3. Compute number of pages used for the sample-data-block-table
+	 *	 and ensure a minimum of CPUM_SF_MIN_SDBT (at minimum one table
+	 *	 to manage up to 511 sample-data-blocks).
+	 */
+	freq = sample_rate_to_freq(&cpuhw->qsi, SAMPL_RATE(hwc));
+	factor = 1;
+	n_sdb = DIV_ROUND_UP(freq, factor * ((PAGE_SIZE-64) / cpuhw->qsi.bsdes));
+	if (n_sdb < CPUM_SF_MIN_SDB)
+		n_sdb = CPUM_SF_MIN_SDB;
+
+	/* Return if there is already a sampling buffer allocated.
+	 * XXX Remove this later and check number of available and
+	 * required sdb's and, if necessary, increase the sampling buffer.
+	 */
+	if (sf_buffer_available(cpuhw))
+		return 0;
+
+	debug_sprintf_event(sfdbg, 3,
+			    "allocate_sdbt: rate=%lu f=%lu sdb=%lu/%i cpuhw=%p\n",
+			    SAMPL_RATE(hwc), freq, n_sdb, CPUM_SF_MAX_SDB, cpuhw);
+
+	return alloc_sampling_buffer(&cpuhw->sfb,
+			       min_t(unsigned long, n_sdb, CPUM_SF_MAX_SDB));
+}
+
+
+/* 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);
+
+/*
+ * 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);
+}
+
+
+#define PMC_INIT      0
+#define PMC_RELEASE   1
+static void setup_pmc_cpu(void *flags)
+{
+	int err;
+	struct cpu_hw_sf *cpusf = &__get_cpu_var(cpu_hw_sf);
+
+	/* XXX Improve error handling and pass a flag in the *flags
+	 *     variable to indicate failures.  Alternatively, ignore
+	 *     (print) errors here and let the PMU functions fail if
+	 *     the per-cpu PMU_F_RESERVED flag is not.
+	 */
+	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 {
+			if (cpusf->sfb.sdbt)
+				free_sampling_buffer(&cpusf->sfb);
+		}
+		debug_sprintf_event(sfdbg, 5,
+				    "setup_pmc_cpu: released: cpuhw=%p\n", cpusf);
+		break;
+	}
+}
+
+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);
+	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)
+{
+	TEAR_REG(hwc) = sdbt_origin;	      /* (re)set to first sdb table */
+}
+
+static unsigned long hw_limit_rate(const struct hws_qsi_info_block *si,
+				   unsigned long rate)
+{
+	if (rate < si->min_sampl_rate)
+		return si->min_sampl_rate;
+	if (rate > si->max_sampl_rate)
+		return si->max_sampl_rate;
+	return rate;
+}
+
+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;
+	}
+
+	/* 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));
+
+	/* 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_sdbt(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_sdbt(cpuhw, hwc);
+			if (err)
+				break;
+		}
+	}
+out:
+	return err;
+}
+
+static int cpumsf_pmu_event_init(struct perf_event *event)
+{
+	int err;
+
+	if (event->attr.type != PERF_TYPE_RAW)
+		return -ENOENT;
+
+	if (event->attr.config != PERF_EVENT_CPUM_SF)
+		return -ENOENT;
+
+	if (event->cpu >= nr_cpumask_bits ||
+	    (event->cpu >= 0 && !cpu_online(event->cpu)))
+		return -ENODEV;
+
+	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 = &__get_cpu_var(cpu_hw_sf);
+	int err;
+
+	if (cpuhw->flags & PMU_F_ENABLED)
+		return;
+
+	if (cpuhw->flags & PMU_F_ERR_MASK)
+		return;
+
+	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;
+	}
+
+	debug_sprintf_event(sfdbg, 6, "pmu_enable: es=%i cs=%i tear=%p dear=%p\n",
+			    cpuhw->lsctl.es, cpuhw->lsctl.cs,
+			    (void *) cpuhw->lsctl.tear, (void *) cpuhw->lsctl.dear);
+}
+
+static void cpumsf_pmu_disable(struct pmu *pmu)
+{
+	struct cpu_hw_sf *cpuhw = &__get_cpu_var(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;
+
+	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_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_data_entry *sample)
+{
+	int overflow;
+	struct pt_regs regs;
+	struct perf_sample_data data;
+
+	/* Skip samples that are invalid or for which the instruction address
+	 * is not predictable.	For the latter, the wait-state bit is set.
+	 */
+	if (sample->I || sample->W)
+		return 0;
+
+	perf_sample_data_init(&data, 0, event->hw.last_period);
+
+	memset(&regs, 0, sizeof(regs));
+	regs.psw.addr = sample->ia;
+	if (sample->T)
+		regs.psw.mask |= PSW_MASK_DAT;
+	if (sample->W)
+		regs.psw.mask |= PSW_MASK_WAIT;
+	if (sample->P)
+		regs.psw.mask |= PSW_MASK_PSTATE;
+	switch (sample->AS) {
+	case 0x0:
+		regs.psw.mask |= PSW_ASC_PRIMARY;
+		break;
+	case 0x1:
+		regs.psw.mask |= PSW_ASC_ACCREG;
+		break;
+	case 0x2:
+		regs.psw.mask |= PSW_ASC_SECONDARY;
+		break;
+	case 0x3:
+		regs.psw.mask |= PSW_ASC_HOME;
+		break;
+	}
+
+	overflow = 0;
+	if (perf_event_overflow(event, &data, &regs)) {
+		overflow = 1;
+		event->pmu->stop(event, 0);
+		debug_sprintf_event(sfdbg, 4, "perf_push_sample: PMU stopped"
+				    " because of an event overflow\n");
+	}
+	perf_event_update_userpage(event);
+
+	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 hardware sample-data that is
+ * pushed to the perf event subsystem.	The overflow reports the number of
+ * samples that has been discarded due to an event overflow.
+ */
+static void hw_collect_samples(struct perf_event *event, unsigned long *sdbt,
+			       unsigned long long *overflow)
+{
+	struct hws_data_entry *sample;
+	unsigned long *trailer;
+
+	trailer = trailer_entry_ptr(*sdbt);
+	sample = (struct hws_data_entry *) *sdbt;
+	while ((unsigned long *) sample < trailer) {
+		/* Check for an empty sample */
+		if (!sample->def)
+			break;
+
+		/* Update perf event period */
+		perf_event_count_update(event, SAMPL_RATE(&event->hw));
+
+		/* Check for basic sampling mode */
+		if (sample->def == 0x0001) {
+			/* If an event overflow occurred, the PMU is stopped to
+			 * throttle event delivery.  Remaining sample data is
+			 * discarded.
+			 */
+			if (!*overflow)
+				*overflow = perf_push_sample(event, sample);
+			else
+				/* Count discarded samples */
+				*overflow += 1;
+		} else
+			/* Sample slot is not yet written or other record */
+			debug_sprintf_event(sfdbg, 5, "hw_collect_samples: "
+					    "Unknown sample data entry format:"
+					    " %i\n", sample->def);
+
+		/* 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.
+ *
+ */
+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;
+	int done;
+
+	sdbt = (unsigned long *) TEAR_REG(hwc);
+	done = event_overflow = sampl_overflow = 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 sample overflow count */
+		if (te->overflow) {
+			/* Increment sample overflow counter */
+			sampl_overflow += te->overflow;
+
+			/* XXX: If an sample overflow occurs, increase the
+			 *	sampling buffer.  Set a "realloc" flag because
+			 *	the sampler must be re-enabled for changing
+			 *	the sample-data-block-table content.
+			 */
+		}
+
+		/* 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) ? te->timestamp : 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);
+
+		/* Reset trailer */
+		xchg(&te->overflow, 0);
+		xchg((unsigned char *) te, 0x40);
+
+		/* 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;
+	}
+
+	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);
+}
+
+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 = &__get_cpu_var(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;
+	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 = &__get_cpu_var(cpu_hw_sf);
+
+	if (event->hw.state & PERF_HES_STOPPED)
+		return;
+
+	perf_pmu_disable(event->pmu);
+	cpuhw->lsctl.cs = 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 = &__get_cpu_var(cpu_hw_sf);
+	int err;
+
+	if (cpuhw->flags & PMU_F_IN_USE)
+		return -EAGAIN;
+
+	if (!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.tear = cpuhw->sfb.sdbt;
+	cpuhw->lsctl.dear = *(unsigned long *) cpuhw->sfb.sdbt;
+	cpuhw->lsctl.interval = SAMPL_RATE(&event->hw);
+	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)) {
+		err = -EAGAIN;
+		goto out;
+	}
+	cpuhw->lsctl.es = 1;
+
+	/* Set in_use flag and store event */
+	event->hw.idx = 0;	  /* only one sampling event per CPU supported */
+	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 = &__get_cpu_var(cpu_hw_sf);
+
+	perf_pmu_disable(event->pmu);
+	cpumsf_pmu_stop(event, PERF_EF_UPDATE);
+
+	cpuhw->lsctl.es = 0;
+	cpuhw->flags &= ~PMU_F_IN_USE;
+	cpuhw->event = NULL;
+
+	perf_event_update_userpage(event);
+	perf_pmu_enable(event->pmu);
+}
+
+static int cpumsf_pmu_event_idx(struct perf_event *event)
+{
+	return event->hw.idx;
+}
+
+CPUMF_EVENT_ATTR(SF, SF_CYCLES_BASIC, PERF_EVENT_CPUM_SF);
+
+static struct attribute *cpumsf_pmu_events_attr[] = {
+	CPUMF_EVENT_PTR(SF, SF_CYCLES_BASIC),
+	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,
+
+	.event_idx    = cpumsf_pmu_event_idx,
+	.attr_groups  = cpumsf_pmu_attr_groups,
+};
+
+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 = &__get_cpu_var(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)
+			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 __cpuinit cpumf_pmu_notifier(struct notifier_block *self,
+					unsigned long action, void *hcpu)
+{
+	unsigned int cpu = (long) hcpu;
+	int flags;
+
+	/* Ignore the notification if no events are scheduled on the PMU.
+	 * This might be racy...
+	 */
+	if (!atomic_read(&num_events))
+		return NOTIFY_OK;
+
+	switch (action & ~CPU_TASKS_FROZEN) {
+	case CPU_ONLINE:
+	case CPU_ONLINE_FROZEN:
+		flags = PMC_INIT;
+		smp_call_function_single(cpu, setup_pmc_cpu, &flags, 1);
+		break;
+	case CPU_DOWN_PREPARE:
+		flags = PMC_RELEASE;
+		smp_call_function_single(cpu, setup_pmc_cpu, &flags, 1);
+		break;
+	default:
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static int __init init_cpum_sampling_pmu(void)
+{
+	int err;
+
+	if (!cpum_sf_avail())
+		return -ENODEV;
+
+	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_interrupt(0x1407, cpumf_measurement_alert);
+	if (err) {
+		pr_err("Failed to register for CPU-measurement alerts\n");
+		goto out;
+	}
+
+	err = perf_pmu_register(&cpumf_sampling, "cpum_sf", PERF_TYPE_RAW);
+	if (err) {
+		pr_err("Failed to register cpum_sf pmu\n");
+		unregister_external_interrupt(0x1407, cpumf_measurement_alert);
+		goto out;
+	}
+	perf_cpu_notifier(cpumf_pmu_notifier);
+out:
+	return err;
+}
+arch_initcall(init_cpum_sampling_pmu);

arch/s390/kernel/perf_event.c

@@ -16,6 +16,7 @@
 #include <linux/kvm_host.h>
 #include <linux/percpu.h>
 #include <linux/export.h>
+#include <linux/spinlock.h>
 #include <linux/sysfs.h>
 #include <asm/irq.h>
 #include <asm/cpu_mf.h>
@@ -36,6 +37,8 @@ int perf_num_counters(void)
 
 	if (cpum_cf_avail())
 		num += PERF_CPUM_CF_MAX_CTR;
+	if (cpum_sf_avail())
+		num += PERF_CPUM_SF_MAX_CTR;
 
 	return num;
 }
@@ -93,24 +96,45 @@ unsigned long perf_misc_flags(struct pt_regs *regs)
 			       : PERF_RECORD_MISC_KERNEL;
 }
 
-void perf_event_print_debug(void)
+void print_debug_cf(void)
 {
 	struct cpumf_ctr_info cf_info;
-	unsigned long flags;
-	int cpu;
-
-	if (!cpum_cf_avail())
-		return;
-
-	local_irq_save(flags);
+	int cpu = smp_processor_id();
 
-	cpu = smp_processor_id();
 	memset(&cf_info, 0, sizeof(cf_info));
 	if (!qctri(&cf_info))
 		pr_info("CPU[%i] CPUM_CF: ver=%u.%u A=%04x E=%04x C=%04x\n",
 			cpu, cf_info.cfvn, cf_info.csvn,
 			cf_info.auth_ctl, cf_info.enable_ctl, cf_info.act_ctl);
+}
+
+static void print_debug_sf(void)
+{
+	struct hws_qsi_info_block si;
+	int cpu = smp_processor_id();
+
+	memset(&si, 0, sizeof(si));
+	if (qsi(&si)) {
+		pr_err("CPU[%i]: CPM_SF: qsi failed\n");
+		return;
+	}
+
+	pr_info("CPU[%i]: CPM_SF: as=%i es=%i cs=%i bsdes=%i dsdes=%i"
+		" min=%i max=%i cpu_speed=%i tear=%p dear=%p\n",
+		cpu, si.as, si.es, si.cs, si.bsdes, si.dsdes,
+		si.min_sampl_rate, si.max_sampl_rate, si.cpu_speed,
+		si.tear, si.dear);
+}
+
+void perf_event_print_debug(void)
+{
+	unsigned long flags;
 
+	local_irq_save(flags);
+	if (cpum_cf_avail())
+		print_debug_cf();
+	if (cpum_sf_avail())
+		print_debug_sf();
 	local_irq_restore(flags);
 }