nfs: add minor version to nfs_server_key for fscache

[linux/fpc-iii.git] / drivers / perf / arm_spe_pmu.c

/*
 * Perf support for the Statistical Profiling Extension, introduced as
 * part of ARMv8.2.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Copyright (C) 2016 ARM Limited
 *
 * Author: Will Deacon <will.deacon@arm.com>
 */

#define PMUNAME                                 "arm_spe"
#define DRVNAME                                 PMUNAME "_pmu"
#define pr_fmt(fmt)                             DRVNAME ": " fmt

#include <linux/bitops.h>
#include <linux/bug.h>
#include <linux/capability.h>
#include <linux/cpuhotplug.h>
#include <linux/cpumask.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/perf_event.h>
#include <linux/platform_device.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/vmalloc.h>

#include <asm/barrier.h>
#include <asm/cpufeature.h>
#include <asm/mmu.h>
#include <asm/sysreg.h>

#define ARM_SPE_BUF_PAD_BYTE                    0

struct arm_spe_pmu_buf {
        int                                     nr_pages;
        bool                                    snapshot;
        void                                    *base;
};

struct arm_spe_pmu {
        struct pmu                              pmu;
        struct platform_device                  *pdev;
        cpumask_t                               supported_cpus;
        struct hlist_node                       hotplug_node;

        int                                     irq; /* PPI */

        u16                                     min_period;
        u16                                     counter_sz;

#define SPE_PMU_FEAT_FILT_EVT                   (1UL << 0)
#define SPE_PMU_FEAT_FILT_TYP                   (1UL << 1)
#define SPE_PMU_FEAT_FILT_LAT                   (1UL << 2)
#define SPE_PMU_FEAT_ARCH_INST                  (1UL << 3)
#define SPE_PMU_FEAT_LDS                        (1UL << 4)
#define SPE_PMU_FEAT_ERND                       (1UL << 5)
#define SPE_PMU_FEAT_DEV_PROBED                 (1UL << 63)
        u64                                     features;

        u16                                     max_record_sz;
        u16                                     align;
        struct perf_output_handle __percpu      *handle;
};

#define to_spe_pmu(p) (container_of(p, struct arm_spe_pmu, pmu))

/* Convert a free-running index from perf into an SPE buffer offset */
#define PERF_IDX2OFF(idx, buf)  ((idx) % ((buf)->nr_pages << PAGE_SHIFT))

/* Keep track of our dynamic hotplug state */
static enum cpuhp_state arm_spe_pmu_online;

enum arm_spe_pmu_buf_fault_action {
        SPE_PMU_BUF_FAULT_ACT_SPURIOUS,
        SPE_PMU_BUF_FAULT_ACT_FATAL,
        SPE_PMU_BUF_FAULT_ACT_OK,
};

/* This sysfs gunk was really good fun to write. */
enum arm_spe_pmu_capabilities {
        SPE_PMU_CAP_ARCH_INST = 0,
        SPE_PMU_CAP_ERND,
        SPE_PMU_CAP_FEAT_MAX,
        SPE_PMU_CAP_CNT_SZ = SPE_PMU_CAP_FEAT_MAX,
        SPE_PMU_CAP_MIN_IVAL,
};

static int arm_spe_pmu_feat_caps[SPE_PMU_CAP_FEAT_MAX] = {
        [SPE_PMU_CAP_ARCH_INST] = SPE_PMU_FEAT_ARCH_INST,
        [SPE_PMU_CAP_ERND]      = SPE_PMU_FEAT_ERND,
};

static u32 arm_spe_pmu_cap_get(struct arm_spe_pmu *spe_pmu, int cap)
{
        if (cap < SPE_PMU_CAP_FEAT_MAX)
                return !!(spe_pmu->features & arm_spe_pmu_feat_caps[cap]);

        switch (cap) {
        case SPE_PMU_CAP_CNT_SZ:
                return spe_pmu->counter_sz;
        case SPE_PMU_CAP_MIN_IVAL:
                return spe_pmu->min_period;
        default:
                WARN(1, "unknown cap %d\n", cap);
        }

        return 0;
}

static ssize_t arm_spe_pmu_cap_show(struct device *dev,
                                    struct device_attribute *attr,
                                    char *buf)
{
        struct arm_spe_pmu *spe_pmu = dev_get_drvdata(dev);
        struct dev_ext_attribute *ea =
                container_of(attr, struct dev_ext_attribute, attr);
        int cap = (long)ea->var;

        return snprintf(buf, PAGE_SIZE, "%u\n",
                arm_spe_pmu_cap_get(spe_pmu, cap));
}

#define SPE_EXT_ATTR_ENTRY(_name, _func, _var)                          \
        &((struct dev_ext_attribute[]) {                                \
                { __ATTR(_name, S_IRUGO, _func, NULL), (void *)_var }   \
        })[0].attr.attr

#define SPE_CAP_EXT_ATTR_ENTRY(_name, _var)                             \
        SPE_EXT_ATTR_ENTRY(_name, arm_spe_pmu_cap_show, _var)

static struct attribute *arm_spe_pmu_cap_attr[] = {
        SPE_CAP_EXT_ATTR_ENTRY(arch_inst, SPE_PMU_CAP_ARCH_INST),
        SPE_CAP_EXT_ATTR_ENTRY(ernd, SPE_PMU_CAP_ERND),
        SPE_CAP_EXT_ATTR_ENTRY(count_size, SPE_PMU_CAP_CNT_SZ),
        SPE_CAP_EXT_ATTR_ENTRY(min_interval, SPE_PMU_CAP_MIN_IVAL),
        NULL,
};

static struct attribute_group arm_spe_pmu_cap_group = {
        .name   = "caps",
        .attrs  = arm_spe_pmu_cap_attr,
};

/* User ABI */
#define ATTR_CFG_FLD_ts_enable_CFG              config  /* PMSCR_EL1.TS */
#define ATTR_CFG_FLD_ts_enable_LO               0
#define ATTR_CFG_FLD_ts_enable_HI               0
#define ATTR_CFG_FLD_pa_enable_CFG              config  /* PMSCR_EL1.PA */
#define ATTR_CFG_FLD_pa_enable_LO               1
#define ATTR_CFG_FLD_pa_enable_HI               1
#define ATTR_CFG_FLD_pct_enable_CFG             config  /* PMSCR_EL1.PCT */
#define ATTR_CFG_FLD_pct_enable_LO              2
#define ATTR_CFG_FLD_pct_enable_HI              2
#define ATTR_CFG_FLD_jitter_CFG                 config  /* PMSIRR_EL1.RND */
#define ATTR_CFG_FLD_jitter_LO                  16
#define ATTR_CFG_FLD_jitter_HI                  16
#define ATTR_CFG_FLD_branch_filter_CFG          config  /* PMSFCR_EL1.B */
#define ATTR_CFG_FLD_branch_filter_LO           32
#define ATTR_CFG_FLD_branch_filter_HI           32
#define ATTR_CFG_FLD_load_filter_CFG            config  /* PMSFCR_EL1.LD */
#define ATTR_CFG_FLD_load_filter_LO             33
#define ATTR_CFG_FLD_load_filter_HI             33
#define ATTR_CFG_FLD_store_filter_CFG           config  /* PMSFCR_EL1.ST */
#define ATTR_CFG_FLD_store_filter_LO            34
#define ATTR_CFG_FLD_store_filter_HI            34

#define ATTR_CFG_FLD_event_filter_CFG           config1 /* PMSEVFR_EL1 */
#define ATTR_CFG_FLD_event_filter_LO            0
#define ATTR_CFG_FLD_event_filter_HI            63

#define ATTR_CFG_FLD_min_latency_CFG            config2 /* PMSLATFR_EL1.MINLAT */
#define ATTR_CFG_FLD_min_latency_LO             0
#define ATTR_CFG_FLD_min_latency_HI             11

/* Why does everything I do descend into this? */
#define __GEN_PMU_FORMAT_ATTR(cfg, lo, hi)                              \
        (lo) == (hi) ? #cfg ":" #lo "\n" : #cfg ":" #lo "-" #hi

#define _GEN_PMU_FORMAT_ATTR(cfg, lo, hi)                               \
        __GEN_PMU_FORMAT_ATTR(cfg, lo, hi)

#define GEN_PMU_FORMAT_ATTR(name)                                       \
        PMU_FORMAT_ATTR(name,                                           \
        _GEN_PMU_FORMAT_ATTR(ATTR_CFG_FLD_##name##_CFG,                 \
                             ATTR_CFG_FLD_##name##_LO,                  \
                             ATTR_CFG_FLD_##name##_HI))

#define _ATTR_CFG_GET_FLD(attr, cfg, lo, hi)                            \
        ((((attr)->cfg) >> lo) & GENMASK(hi - lo, 0))

#define ATTR_CFG_GET_FLD(attr, name)                                    \
        _ATTR_CFG_GET_FLD(attr,                                         \
                          ATTR_CFG_FLD_##name##_CFG,                    \
                          ATTR_CFG_FLD_##name##_LO,                     \
                          ATTR_CFG_FLD_##name##_HI)

GEN_PMU_FORMAT_ATTR(ts_enable);
GEN_PMU_FORMAT_ATTR(pa_enable);
GEN_PMU_FORMAT_ATTR(pct_enable);
GEN_PMU_FORMAT_ATTR(jitter);
GEN_PMU_FORMAT_ATTR(branch_filter);
GEN_PMU_FORMAT_ATTR(load_filter);
GEN_PMU_FORMAT_ATTR(store_filter);
GEN_PMU_FORMAT_ATTR(event_filter);
GEN_PMU_FORMAT_ATTR(min_latency);

static struct attribute *arm_spe_pmu_formats_attr[] = {
        &format_attr_ts_enable.attr,
        &format_attr_pa_enable.attr,
        &format_attr_pct_enable.attr,
        &format_attr_jitter.attr,
        &format_attr_branch_filter.attr,
        &format_attr_load_filter.attr,
        &format_attr_store_filter.attr,
        &format_attr_event_filter.attr,
        &format_attr_min_latency.attr,
        NULL,
};

static struct attribute_group arm_spe_pmu_format_group = {
        .name   = "format",
        .attrs  = arm_spe_pmu_formats_attr,
};

static ssize_t arm_spe_pmu_get_attr_cpumask(struct device *dev,
                                            struct device_attribute *attr,
                                            char *buf)
{
        struct arm_spe_pmu *spe_pmu = dev_get_drvdata(dev);

        return cpumap_print_to_pagebuf(true, buf, &spe_pmu->supported_cpus);
}
static DEVICE_ATTR(cpumask, S_IRUGO, arm_spe_pmu_get_attr_cpumask, NULL);

static struct attribute *arm_spe_pmu_attrs[] = {
        &dev_attr_cpumask.attr,
        NULL,
};

static struct attribute_group arm_spe_pmu_group = {
        .attrs  = arm_spe_pmu_attrs,
};

static const struct attribute_group *arm_spe_pmu_attr_groups[] = {
        &arm_spe_pmu_group,
        &arm_spe_pmu_cap_group,
        &arm_spe_pmu_format_group,
        NULL,
};

/* Convert between user ABI and register values */
static u64 arm_spe_event_to_pmscr(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        u64 reg = 0;

        reg |= ATTR_CFG_GET_FLD(attr, ts_enable) << SYS_PMSCR_EL1_TS_SHIFT;
        reg |= ATTR_CFG_GET_FLD(attr, pa_enable) << SYS_PMSCR_EL1_PA_SHIFT;
        reg |= ATTR_CFG_GET_FLD(attr, pct_enable) << SYS_PMSCR_EL1_PCT_SHIFT;

        if (!attr->exclude_user)
                reg |= BIT(SYS_PMSCR_EL1_E0SPE_SHIFT);

        if (!attr->exclude_kernel)
                reg |= BIT(SYS_PMSCR_EL1_E1SPE_SHIFT);

        if (IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR) && capable(CAP_SYS_ADMIN))
                reg |= BIT(SYS_PMSCR_EL1_CX_SHIFT);

        return reg;
}

static void arm_spe_event_sanitise_period(struct perf_event *event)
{
        struct arm_spe_pmu *spe_pmu = to_spe_pmu(event->pmu);
        u64 period = event->hw.sample_period;
        u64 max_period = SYS_PMSIRR_EL1_INTERVAL_MASK
                         << SYS_PMSIRR_EL1_INTERVAL_SHIFT;

        if (period < spe_pmu->min_period)
                period = spe_pmu->min_period;
        else if (period > max_period)
                period = max_period;
        else
                period &= max_period;

        event->hw.sample_period = period;
}

static u64 arm_spe_event_to_pmsirr(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        u64 reg = 0;

        arm_spe_event_sanitise_period(event);

        reg |= ATTR_CFG_GET_FLD(attr, jitter) << SYS_PMSIRR_EL1_RND_SHIFT;
        reg |= event->hw.sample_period;

        return reg;
}

static u64 arm_spe_event_to_pmsfcr(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        u64 reg = 0;

        reg |= ATTR_CFG_GET_FLD(attr, load_filter) << SYS_PMSFCR_EL1_LD_SHIFT;
        reg |= ATTR_CFG_GET_FLD(attr, store_filter) << SYS_PMSFCR_EL1_ST_SHIFT;
        reg |= ATTR_CFG_GET_FLD(attr, branch_filter) << SYS_PMSFCR_EL1_B_SHIFT;

        if (reg)
                reg |= BIT(SYS_PMSFCR_EL1_FT_SHIFT);

        if (ATTR_CFG_GET_FLD(attr, event_filter))
                reg |= BIT(SYS_PMSFCR_EL1_FE_SHIFT);

        if (ATTR_CFG_GET_FLD(attr, min_latency))
                reg |= BIT(SYS_PMSFCR_EL1_FL_SHIFT);

        return reg;
}

static u64 arm_spe_event_to_pmsevfr(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        return ATTR_CFG_GET_FLD(attr, event_filter);
}

static u64 arm_spe_event_to_pmslatfr(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        return ATTR_CFG_GET_FLD(attr, min_latency)
               << SYS_PMSLATFR_EL1_MINLAT_SHIFT;
}

static void arm_spe_pmu_pad_buf(struct perf_output_handle *handle, int len)
{
        struct arm_spe_pmu_buf *buf = perf_get_aux(handle);
        u64 head = PERF_IDX2OFF(handle->head, buf);

        memset(buf->base + head, ARM_SPE_BUF_PAD_BYTE, len);
        if (!buf->snapshot)
                perf_aux_output_skip(handle, len);
}

static u64 arm_spe_pmu_next_snapshot_off(struct perf_output_handle *handle)
{
        struct arm_spe_pmu_buf *buf = perf_get_aux(handle);
        struct arm_spe_pmu *spe_pmu = to_spe_pmu(handle->event->pmu);
        u64 head = PERF_IDX2OFF(handle->head, buf);
        u64 limit = buf->nr_pages * PAGE_SIZE;

        /*
         * The trace format isn't parseable in reverse, so clamp
         * the limit to half of the buffer size in snapshot mode
         * so that the worst case is half a buffer of records, as
         * opposed to a single record.
         */
        if (head < limit >> 1)
                limit >>= 1;

        /*
         * If we're within max_record_sz of the limit, we must
         * pad, move the head index and recompute the limit.
         */
        if (limit - head < spe_pmu->max_record_sz) {
                arm_spe_pmu_pad_buf(handle, limit - head);
                handle->head = PERF_IDX2OFF(limit, buf);
                limit = ((buf->nr_pages * PAGE_SIZE) >> 1) + handle->head;
        }

        return limit;
}

static u64 __arm_spe_pmu_next_off(struct perf_output_handle *handle)
{
        struct arm_spe_pmu *spe_pmu = to_spe_pmu(handle->event->pmu);
        struct arm_spe_pmu_buf *buf = perf_get_aux(handle);
        const u64 bufsize = buf->nr_pages * PAGE_SIZE;
        u64 limit = bufsize;
        u64 head, tail, wakeup;

        /*
         * The head can be misaligned for two reasons:
         *
         * 1. The hardware left PMBPTR pointing to the first byte after
         *    a record when generating a buffer management event.
         *
         * 2. We used perf_aux_output_skip to consume handle->size bytes
         *    and CIRC_SPACE was used to compute the size, which always
         *    leaves one entry free.
         *
         * Deal with this by padding to the next alignment boundary and
         * moving the head index. If we run out of buffer space, we'll
         * reduce handle->size to zero and end up reporting truncation.
         */
        head = PERF_IDX2OFF(handle->head, buf);
        if (!IS_ALIGNED(head, spe_pmu->align)) {
                unsigned long delta = roundup(head, spe_pmu->align) - head;

                delta = min(delta, handle->size);
                arm_spe_pmu_pad_buf(handle, delta);
                head = PERF_IDX2OFF(handle->head, buf);
        }

        /* If we've run out of free space, then nothing more to do */
        if (!handle->size)
                goto no_space;

        /* Compute the tail and wakeup indices now that we've aligned head */
        tail = PERF_IDX2OFF(handle->head + handle->size, buf);
        wakeup = PERF_IDX2OFF(handle->wakeup, buf);

        /*
         * Avoid clobbering unconsumed data. We know we have space, so
         * if we see head == tail we know that the buffer is empty. If
         * head > tail, then there's nothing to clobber prior to
         * wrapping.
         */
        if (head < tail)
                limit = round_down(tail, PAGE_SIZE);

        /*
         * Wakeup may be arbitrarily far into the future. If it's not in
         * the current generation, either we'll wrap before hitting it,
         * or it's in the past and has been handled already.
         *
         * If there's a wakeup before we wrap, arrange to be woken up by
         * the page boundary following it. Keep the tail boundary if
         * that's lower.
         */
        if (handle->wakeup < (handle->head + handle->size) && head <= wakeup)
                limit = min(limit, round_up(wakeup, PAGE_SIZE));

        if (limit > head)
                return limit;

        arm_spe_pmu_pad_buf(handle, handle->size);
no_space:
        perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
        perf_aux_output_end(handle, 0);
        return 0;
}

static u64 arm_spe_pmu_next_off(struct perf_output_handle *handle)
{
        struct arm_spe_pmu_buf *buf = perf_get_aux(handle);
        struct arm_spe_pmu *spe_pmu = to_spe_pmu(handle->event->pmu);
        u64 limit = __arm_spe_pmu_next_off(handle);
        u64 head = PERF_IDX2OFF(handle->head, buf);

        /*
         * If the head has come too close to the end of the buffer,
         * then pad to the end and recompute the limit.
         */
        if (limit && (limit - head < spe_pmu->max_record_sz)) {
                arm_spe_pmu_pad_buf(handle, limit - head);
                limit = __arm_spe_pmu_next_off(handle);
        }

        return limit;
}

static void arm_spe_perf_aux_output_begin(struct perf_output_handle *handle,
                                          struct perf_event *event)
{
        u64 base, limit;
        struct arm_spe_pmu_buf *buf;

        /* Start a new aux session */
        buf = perf_aux_output_begin(handle, event);
        if (!buf) {
                event->hw.state |= PERF_HES_STOPPED;
                /*
                 * We still need to clear the limit pointer, since the
                 * profiler might only be disabled by virtue of a fault.
                 */
                limit = 0;
                goto out_write_limit;
        }

        limit = buf->snapshot ? arm_spe_pmu_next_snapshot_off(handle)
                              : arm_spe_pmu_next_off(handle);
        if (limit)
                limit |= BIT(SYS_PMBLIMITR_EL1_E_SHIFT);

        limit += (u64)buf->base;
        base = (u64)buf->base + PERF_IDX2OFF(handle->head, buf);
        write_sysreg_s(base, SYS_PMBPTR_EL1);

out_write_limit:
        write_sysreg_s(limit, SYS_PMBLIMITR_EL1);
}

static void arm_spe_perf_aux_output_end(struct perf_output_handle *handle)
{
        struct arm_spe_pmu_buf *buf = perf_get_aux(handle);
        u64 offset, size;

        offset = read_sysreg_s(SYS_PMBPTR_EL1) - (u64)buf->base;
        size = offset - PERF_IDX2OFF(handle->head, buf);

        if (buf->snapshot)
                handle->head = offset;

        perf_aux_output_end(handle, size);
}

static void arm_spe_pmu_disable_and_drain_local(void)
{
        /* Disable profiling at EL0 and EL1 */
        write_sysreg_s(0, SYS_PMSCR_EL1);
        isb();

        /* Drain any buffered data */
        psb_csync();
        dsb(nsh);

        /* Disable the profiling buffer */
        write_sysreg_s(0, SYS_PMBLIMITR_EL1);
        isb();
}

/* IRQ handling */
static enum arm_spe_pmu_buf_fault_action
arm_spe_pmu_buf_get_fault_act(struct perf_output_handle *handle)
{
        const char *err_str;
        u64 pmbsr;
        enum arm_spe_pmu_buf_fault_action ret;

        /*
         * Ensure new profiling data is visible to the CPU and any external
         * aborts have been resolved.
         */
        psb_csync();
        dsb(nsh);

        /* Ensure hardware updates to PMBPTR_EL1 are visible */
        isb();

        /* Service required? */
        pmbsr = read_sysreg_s(SYS_PMBSR_EL1);
        if (!(pmbsr & BIT(SYS_PMBSR_EL1_S_SHIFT)))
                return SPE_PMU_BUF_FAULT_ACT_SPURIOUS;

        /*
         * If we've lost data, disable profiling and also set the PARTIAL
         * flag to indicate that the last record is corrupted.
         */
        if (pmbsr & BIT(SYS_PMBSR_EL1_DL_SHIFT))
                perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED |
                                             PERF_AUX_FLAG_PARTIAL);

        /* Report collisions to userspace so that it can up the period */
        if (pmbsr & BIT(SYS_PMBSR_EL1_COLL_SHIFT))
                perf_aux_output_flag(handle, PERF_AUX_FLAG_COLLISION);

        /* We only expect buffer management events */
        switch (pmbsr & (SYS_PMBSR_EL1_EC_MASK << SYS_PMBSR_EL1_EC_SHIFT)) {
        case SYS_PMBSR_EL1_EC_BUF:
                /* Handled below */
                break;
        case SYS_PMBSR_EL1_EC_FAULT_S1:
        case SYS_PMBSR_EL1_EC_FAULT_S2:
                err_str = "Unexpected buffer fault";
                goto out_err;
        default:
                err_str = "Unknown error code";
                goto out_err;
        }

        /* Buffer management event */
        switch (pmbsr &
                (SYS_PMBSR_EL1_BUF_BSC_MASK << SYS_PMBSR_EL1_BUF_BSC_SHIFT)) {
        case SYS_PMBSR_EL1_BUF_BSC_FULL:
                ret = SPE_PMU_BUF_FAULT_ACT_OK;
                goto out_stop;
        default:
                err_str = "Unknown buffer status code";
        }

out_err:
        pr_err_ratelimited("%s on CPU %d [PMBSR=0x%016llx, PMBPTR=0x%016llx, PMBLIMITR=0x%016llx]\n",
                           err_str, smp_processor_id(), pmbsr,
                           read_sysreg_s(SYS_PMBPTR_EL1),
                           read_sysreg_s(SYS_PMBLIMITR_EL1));
        ret = SPE_PMU_BUF_FAULT_ACT_FATAL;

out_stop:
        arm_spe_perf_aux_output_end(handle);
        return ret;
}

static irqreturn_t arm_spe_pmu_irq_handler(int irq, void *dev)
{
        struct perf_output_handle *handle = dev;
        struct perf_event *event = handle->event;
        enum arm_spe_pmu_buf_fault_action act;

        if (!perf_get_aux(handle))
                return IRQ_NONE;

        act = arm_spe_pmu_buf_get_fault_act(handle);
        if (act == SPE_PMU_BUF_FAULT_ACT_SPURIOUS)
                return IRQ_NONE;

        /*
         * Ensure perf callbacks have completed, which may disable the
         * profiling buffer in response to a TRUNCATION flag.
         */
        irq_work_run();

        switch (act) {
        case SPE_PMU_BUF_FAULT_ACT_FATAL:
                /*
                 * If a fatal exception occurred then leaving the profiling
                 * buffer enabled is a recipe waiting to happen. Since
                 * fatal faults don't always imply truncation, make sure
                 * that the profiling buffer is disabled explicitly before
                 * clearing the syndrome register.
                 */
                arm_spe_pmu_disable_and_drain_local();
                break;
        case SPE_PMU_BUF_FAULT_ACT_OK:
                /*
                 * We handled the fault (the buffer was full), so resume
                 * profiling as long as we didn't detect truncation.
                 * PMBPTR might be misaligned, but we'll burn that bridge
                 * when we get to it.
                 */
                if (!(handle->aux_flags & PERF_AUX_FLAG_TRUNCATED)) {
                        arm_spe_perf_aux_output_begin(handle, event);
                        isb();
                }
                break;
        case SPE_PMU_BUF_FAULT_ACT_SPURIOUS:
                /* We've seen you before, but GCC has the memory of a sieve. */
                break;
        }

        /* The buffer pointers are now sane, so resume profiling. */
        write_sysreg_s(0, SYS_PMBSR_EL1);
        return IRQ_HANDLED;
}

/* Perf callbacks */
static int arm_spe_pmu_event_init(struct perf_event *event)
{
        u64 reg;
        struct perf_event_attr *attr = &event->attr;
        struct arm_spe_pmu *spe_pmu = to_spe_pmu(event->pmu);

        /* This is, of course, deeply driver-specific */
        if (attr->type != event->pmu->type)
                return -ENOENT;

        if (event->cpu >= 0 &&
            !cpumask_test_cpu(event->cpu, &spe_pmu->supported_cpus))
                return -ENOENT;

        if (arm_spe_event_to_pmsevfr(event) & SYS_PMSEVFR_EL1_RES0)
                return -EOPNOTSUPP;

        if (attr->exclude_idle)
                return -EOPNOTSUPP;

        /*
         * Feedback-directed frequency throttling doesn't work when we
         * have a buffer of samples. We'd need to manually count the
         * samples in the buffer when it fills up and adjust the event
         * count to reflect that. Instead, just force the user to specify
         * a sample period.
         */
        if (attr->freq)
                return -EINVAL;

        reg = arm_spe_event_to_pmsfcr(event);
        if ((reg & BIT(SYS_PMSFCR_EL1_FE_SHIFT)) &&
            !(spe_pmu->features & SPE_PMU_FEAT_FILT_EVT))
                return -EOPNOTSUPP;

        if ((reg & BIT(SYS_PMSFCR_EL1_FT_SHIFT)) &&
            !(spe_pmu->features & SPE_PMU_FEAT_FILT_TYP))
                return -EOPNOTSUPP;

        if ((reg & BIT(SYS_PMSFCR_EL1_FL_SHIFT)) &&
            !(spe_pmu->features & SPE_PMU_FEAT_FILT_LAT))
                return -EOPNOTSUPP;

        reg = arm_spe_event_to_pmscr(event);
        if (!capable(CAP_SYS_ADMIN) &&
            (reg & (BIT(SYS_PMSCR_EL1_PA_SHIFT) |
                    BIT(SYS_PMSCR_EL1_CX_SHIFT) |
                    BIT(SYS_PMSCR_EL1_PCT_SHIFT))))
                return -EACCES;

        return 0;
}

static void arm_spe_pmu_start(struct perf_event *event, int flags)
{
        u64 reg;
        struct arm_spe_pmu *spe_pmu = to_spe_pmu(event->pmu);
        struct hw_perf_event *hwc = &event->hw;
        struct perf_output_handle *handle = this_cpu_ptr(spe_pmu->handle);

        hwc->state = 0;
        arm_spe_perf_aux_output_begin(handle, event);
        if (hwc->state)
                return;

        reg = arm_spe_event_to_pmsfcr(event);
        write_sysreg_s(reg, SYS_PMSFCR_EL1);

        reg = arm_spe_event_to_pmsevfr(event);
        write_sysreg_s(reg, SYS_PMSEVFR_EL1);

        reg = arm_spe_event_to_pmslatfr(event);
        write_sysreg_s(reg, SYS_PMSLATFR_EL1);

        if (flags & PERF_EF_RELOAD) {
                reg = arm_spe_event_to_pmsirr(event);
                write_sysreg_s(reg, SYS_PMSIRR_EL1);
                isb();
                reg = local64_read(&hwc->period_left);
                write_sysreg_s(reg, SYS_PMSICR_EL1);
        }

        reg = arm_spe_event_to_pmscr(event);
        isb();
        write_sysreg_s(reg, SYS_PMSCR_EL1);
}

static void arm_spe_pmu_stop(struct perf_event *event, int flags)
{
        struct arm_spe_pmu *spe_pmu = to_spe_pmu(event->pmu);
        struct hw_perf_event *hwc = &event->hw;
        struct perf_output_handle *handle = this_cpu_ptr(spe_pmu->handle);

        /* If we're already stopped, then nothing to do */
        if (hwc->state & PERF_HES_STOPPED)
                return;

        /* Stop all trace generation */
        arm_spe_pmu_disable_and_drain_local();

        if (flags & PERF_EF_UPDATE) {
                /*
                 * If there's a fault pending then ensure we contain it
                 * to this buffer, since we might be on the context-switch
                 * path.
                 */
                if (perf_get_aux(handle)) {
                        enum arm_spe_pmu_buf_fault_action act;

                        act = arm_spe_pmu_buf_get_fault_act(handle);
                        if (act == SPE_PMU_BUF_FAULT_ACT_SPURIOUS)
                                arm_spe_perf_aux_output_end(handle);
                        else
                                write_sysreg_s(0, SYS_PMBSR_EL1);
                }

                /*
                 * This may also contain ECOUNT, but nobody else should
                 * be looking at period_left, since we forbid frequency
                 * based sampling.
                 */
                local64_set(&hwc->period_left, read_sysreg_s(SYS_PMSICR_EL1));
                hwc->state |= PERF_HES_UPTODATE;
        }

        hwc->state |= PERF_HES_STOPPED;
}

static int arm_spe_pmu_add(struct perf_event *event, int flags)
{
        int ret = 0;
        struct arm_spe_pmu *spe_pmu = to_spe_pmu(event->pmu);
        struct hw_perf_event *hwc = &event->hw;
        int cpu = event->cpu == -1 ? smp_processor_id() : event->cpu;

        if (!cpumask_test_cpu(cpu, &spe_pmu->supported_cpus))
                return -ENOENT;

        hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;

        if (flags & PERF_EF_START) {
                arm_spe_pmu_start(event, PERF_EF_RELOAD);
                if (hwc->state & PERF_HES_STOPPED)
                        ret = -EINVAL;
        }

        return ret;
}

static void arm_spe_pmu_del(struct perf_event *event, int flags)
{
        arm_spe_pmu_stop(event, PERF_EF_UPDATE);
}

static void arm_spe_pmu_read(struct perf_event *event)
{
}

static void *arm_spe_pmu_setup_aux(struct perf_event *event, void **pages,
                                   int nr_pages, bool snapshot)
{
        int i, cpu = event->cpu;
        struct page **pglist;
        struct arm_spe_pmu_buf *buf;

        /* We need at least two pages for this to work. */
        if (nr_pages < 2)
                return NULL;

        /*
         * We require an even number of pages for snapshot mode, so that
         * we can effectively treat the buffer as consisting of two equal
         * parts and give userspace a fighting chance of getting some
         * useful data out of it.
         */
        if (!nr_pages || (snapshot && (nr_pages & 1)))
                return NULL;

        if (cpu == -1)
                cpu = raw_smp_processor_id();

        buf = kzalloc_node(sizeof(*buf), GFP_KERNEL, cpu_to_node(cpu));
        if (!buf)
                return NULL;

        pglist = kcalloc(nr_pages, sizeof(*pglist), GFP_KERNEL);
        if (!pglist)
                goto out_free_buf;

        for (i = 0; i < nr_pages; ++i) {
                struct page *page = virt_to_page(pages[i]);

                if (PagePrivate(page)) {
                        pr_warn("unexpected high-order page for auxbuf!");
                        goto out_free_pglist;
                }

                pglist[i] = virt_to_page(pages[i]);
        }

        buf->base = vmap(pglist, nr_pages, VM_MAP, PAGE_KERNEL);
        if (!buf->base)
                goto out_free_pglist;

        buf->nr_pages   = nr_pages;
        buf->snapshot   = snapshot;

        kfree(pglist);
        return buf;

out_free_pglist:
        kfree(pglist);
out_free_buf:
        kfree(buf);
        return NULL;
}

static void arm_spe_pmu_free_aux(void *aux)
{
        struct arm_spe_pmu_buf *buf = aux;

        vunmap(buf->base);
        kfree(buf);
}

/* Initialisation and teardown functions */
static int arm_spe_pmu_perf_init(struct arm_spe_pmu *spe_pmu)
{
        static atomic_t pmu_idx = ATOMIC_INIT(-1);

        int idx;
        char *name;
        struct device *dev = &spe_pmu->pdev->dev;

        spe_pmu->pmu = (struct pmu) {
                .module = THIS_MODULE,
                .capabilities   = PERF_PMU_CAP_EXCLUSIVE | PERF_PMU_CAP_ITRACE,
                .attr_groups    = arm_spe_pmu_attr_groups,
                /*
                 * We hitch a ride on the software context here, so that
                 * we can support per-task profiling (which is not possible
                 * with the invalid context as it doesn't get sched callbacks).
                 * This requires that userspace either uses a dummy event for
                 * perf_event_open, since the aux buffer is not setup until
                 * a subsequent mmap, or creates the profiling event in a
                 * disabled state and explicitly PERF_EVENT_IOC_ENABLEs it
                 * once the buffer has been created.
                 */
                .task_ctx_nr    = perf_sw_context,
                .event_init     = arm_spe_pmu_event_init,
                .add            = arm_spe_pmu_add,
                .del            = arm_spe_pmu_del,
                .start          = arm_spe_pmu_start,
                .stop           = arm_spe_pmu_stop,
                .read           = arm_spe_pmu_read,
                .setup_aux      = arm_spe_pmu_setup_aux,
                .free_aux       = arm_spe_pmu_free_aux,
        };

        idx = atomic_inc_return(&pmu_idx);
        name = devm_kasprintf(dev, GFP_KERNEL, "%s_%d", PMUNAME, idx);
        if (!name) {
                dev_err(dev, "failed to allocate name for pmu %d\n", idx);
                return -ENOMEM;
        }

        return perf_pmu_register(&spe_pmu->pmu, name, -1);
}

static void arm_spe_pmu_perf_destroy(struct arm_spe_pmu *spe_pmu)
{
        perf_pmu_unregister(&spe_pmu->pmu);
}

static void __arm_spe_pmu_dev_probe(void *info)
{
        int fld;
        u64 reg;
        struct arm_spe_pmu *spe_pmu = info;
        struct device *dev = &spe_pmu->pdev->dev;

        fld = cpuid_feature_extract_unsigned_field(read_cpuid(ID_AA64DFR0_EL1),
                                                   ID_AA64DFR0_PMSVER_SHIFT);
        if (!fld) {
                dev_err(dev,
                        "unsupported ID_AA64DFR0_EL1.PMSVer [%d] on CPU %d\n",
                        fld, smp_processor_id());
                return;
        }

        /* Read PMBIDR first to determine whether or not we have access */
        reg = read_sysreg_s(SYS_PMBIDR_EL1);
        if (reg & BIT(SYS_PMBIDR_EL1_P_SHIFT)) {
                dev_err(dev,
                        "profiling buffer owned by higher exception level\n");
                return;
        }

        /* Minimum alignment. If it's out-of-range, then fail the probe */
        fld = reg >> SYS_PMBIDR_EL1_ALIGN_SHIFT & SYS_PMBIDR_EL1_ALIGN_MASK;
        spe_pmu->align = 1 << fld;
        if (spe_pmu->align > SZ_2K) {
                dev_err(dev, "unsupported PMBIDR.Align [%d] on CPU %d\n",
                        fld, smp_processor_id());
                return;
        }

        /* It's now safe to read PMSIDR and figure out what we've got */
        reg = read_sysreg_s(SYS_PMSIDR_EL1);
        if (reg & BIT(SYS_PMSIDR_EL1_FE_SHIFT))
                spe_pmu->features |= SPE_PMU_FEAT_FILT_EVT;

        if (reg & BIT(SYS_PMSIDR_EL1_FT_SHIFT))
                spe_pmu->features |= SPE_PMU_FEAT_FILT_TYP;

        if (reg & BIT(SYS_PMSIDR_EL1_FL_SHIFT))
                spe_pmu->features |= SPE_PMU_FEAT_FILT_LAT;

        if (reg & BIT(SYS_PMSIDR_EL1_ARCHINST_SHIFT))
                spe_pmu->features |= SPE_PMU_FEAT_ARCH_INST;

        if (reg & BIT(SYS_PMSIDR_EL1_LDS_SHIFT))
                spe_pmu->features |= SPE_PMU_FEAT_LDS;

        if (reg & BIT(SYS_PMSIDR_EL1_ERND_SHIFT))
                spe_pmu->features |= SPE_PMU_FEAT_ERND;

        /* This field has a spaced out encoding, so just use a look-up */
        fld = reg >> SYS_PMSIDR_EL1_INTERVAL_SHIFT & SYS_PMSIDR_EL1_INTERVAL_MASK;
        switch (fld) {
        case 0:
                spe_pmu->min_period = 256;
                break;
        case 2:
                spe_pmu->min_period = 512;
                break;
        case 3:
                spe_pmu->min_period = 768;
                break;
        case 4:
                spe_pmu->min_period = 1024;
                break;
        case 5:
                spe_pmu->min_period = 1536;
                break;
        case 6:
                spe_pmu->min_period = 2048;
                break;
        case 7:
                spe_pmu->min_period = 3072;
                break;
        default:
                dev_warn(dev, "unknown PMSIDR_EL1.Interval [%d]; assuming 8\n",
                         fld);
                /* Fallthrough */
        case 8:
                spe_pmu->min_period = 4096;
        }

        /* Maximum record size. If it's out-of-range, then fail the probe */
        fld = reg >> SYS_PMSIDR_EL1_MAXSIZE_SHIFT & SYS_PMSIDR_EL1_MAXSIZE_MASK;
        spe_pmu->max_record_sz = 1 << fld;
        if (spe_pmu->max_record_sz > SZ_2K || spe_pmu->max_record_sz < 16) {
                dev_err(dev, "unsupported PMSIDR_EL1.MaxSize [%d] on CPU %d\n",
                        fld, smp_processor_id());
                return;
        }

        fld = reg >> SYS_PMSIDR_EL1_COUNTSIZE_SHIFT & SYS_PMSIDR_EL1_COUNTSIZE_MASK;
        switch (fld) {
        default:
                dev_warn(dev, "unknown PMSIDR_EL1.CountSize [%d]; assuming 2\n",
                         fld);
                /* Fallthrough */
        case 2:
                spe_pmu->counter_sz = 12;
        }

        dev_info(dev,
                 "probed for CPUs %*pbl [max_record_sz %u, align %u, features 0x%llx]\n",
                 cpumask_pr_args(&spe_pmu->supported_cpus),
                 spe_pmu->max_record_sz, spe_pmu->align, spe_pmu->features);

        spe_pmu->features |= SPE_PMU_FEAT_DEV_PROBED;
        return;
}

static void __arm_spe_pmu_reset_local(void)
{
        /*
         * This is probably overkill, as we have no idea where we're
         * draining any buffered data to...
         */
        arm_spe_pmu_disable_and_drain_local();

        /* Reset the buffer base pointer */
        write_sysreg_s(0, SYS_PMBPTR_EL1);
        isb();

        /* Clear any pending management interrupts */
        write_sysreg_s(0, SYS_PMBSR_EL1);
        isb();
}

static void __arm_spe_pmu_setup_one(void *info)
{
        struct arm_spe_pmu *spe_pmu = info;

        __arm_spe_pmu_reset_local();
        enable_percpu_irq(spe_pmu->irq, IRQ_TYPE_NONE);
}

static void __arm_spe_pmu_stop_one(void *info)
{
        struct arm_spe_pmu *spe_pmu = info;

        disable_percpu_irq(spe_pmu->irq);
        __arm_spe_pmu_reset_local();
}

static int arm_spe_pmu_cpu_startup(unsigned int cpu, struct hlist_node *node)
{
        struct arm_spe_pmu *spe_pmu;

        spe_pmu = hlist_entry_safe(node, struct arm_spe_pmu, hotplug_node);
        if (!cpumask_test_cpu(cpu, &spe_pmu->supported_cpus))
                return 0;

        __arm_spe_pmu_setup_one(spe_pmu);
        return 0;
}

static int arm_spe_pmu_cpu_teardown(unsigned int cpu, struct hlist_node *node)
{
        struct arm_spe_pmu *spe_pmu;

        spe_pmu = hlist_entry_safe(node, struct arm_spe_pmu, hotplug_node);
        if (!cpumask_test_cpu(cpu, &spe_pmu->supported_cpus))
                return 0;

        __arm_spe_pmu_stop_one(spe_pmu);
        return 0;
}

static int arm_spe_pmu_dev_init(struct arm_spe_pmu *spe_pmu)
{
        int ret;
        cpumask_t *mask = &spe_pmu->supported_cpus;

        /* Make sure we probe the hardware on a relevant CPU */
        ret = smp_call_function_any(mask,  __arm_spe_pmu_dev_probe, spe_pmu, 1);
        if (ret || !(spe_pmu->features & SPE_PMU_FEAT_DEV_PROBED))
                return -ENXIO;

        /* Request our PPIs (note that the IRQ is still disabled) */
        ret = request_percpu_irq(spe_pmu->irq, arm_spe_pmu_irq_handler, DRVNAME,
                                 spe_pmu->handle);
        if (ret)
                return ret;

        /*
         * Register our hotplug notifier now so we don't miss any events.
         * This will enable the IRQ for any supported CPUs that are already
         * up.
         */
        ret = cpuhp_state_add_instance(arm_spe_pmu_online,
                                       &spe_pmu->hotplug_node);
        if (ret)
                free_percpu_irq(spe_pmu->irq, spe_pmu->handle);

        return ret;
}

static void arm_spe_pmu_dev_teardown(struct arm_spe_pmu *spe_pmu)
{
        cpuhp_state_remove_instance(arm_spe_pmu_online, &spe_pmu->hotplug_node);
        free_percpu_irq(spe_pmu->irq, spe_pmu->handle);
}

/* Driver and device probing */
static int arm_spe_pmu_irq_probe(struct arm_spe_pmu *spe_pmu)
{
        struct platform_device *pdev = spe_pmu->pdev;
        int irq = platform_get_irq(pdev, 0);

        if (irq < 0) {
                dev_err(&pdev->dev, "failed to get IRQ (%d)\n", irq);
                return -ENXIO;
        }

        if (!irq_is_percpu(irq)) {
                dev_err(&pdev->dev, "expected PPI but got SPI (%d)\n", irq);
                return -EINVAL;
        }

        if (irq_get_percpu_devid_partition(irq, &spe_pmu->supported_cpus)) {
                dev_err(&pdev->dev, "failed to get PPI partition (%d)\n", irq);
                return -EINVAL;
        }

        spe_pmu->irq = irq;
        return 0;
}

static const struct of_device_id arm_spe_pmu_of_match[] = {
        { .compatible = "arm,statistical-profiling-extension-v1", .data = (void *)1 },
        { /* Sentinel */ },
};

static int arm_spe_pmu_device_dt_probe(struct platform_device *pdev)
{
        int ret;
        struct arm_spe_pmu *spe_pmu;
        struct device *dev = &pdev->dev;

        /*
         * If kernelspace is unmapped when running at EL0, then the SPE
         * buffer will fault and prematurely terminate the AUX session.
         */
        if (arm64_kernel_unmapped_at_el0()) {
                dev_warn_once(dev, "profiling buffer inaccessible. Try passing \"kpti=off\" on the kernel command line\n");
                return -EPERM;
        }

        spe_pmu = devm_kzalloc(dev, sizeof(*spe_pmu), GFP_KERNEL);
        if (!spe_pmu) {
                dev_err(dev, "failed to allocate spe_pmu\n");
                return -ENOMEM;
        }

        spe_pmu->handle = alloc_percpu(typeof(*spe_pmu->handle));
        if (!spe_pmu->handle)
                return -ENOMEM;

        spe_pmu->pdev = pdev;
        platform_set_drvdata(pdev, spe_pmu);

        ret = arm_spe_pmu_irq_probe(spe_pmu);
        if (ret)
                goto out_free_handle;

        ret = arm_spe_pmu_dev_init(spe_pmu);
        if (ret)
                goto out_free_handle;

        ret = arm_spe_pmu_perf_init(spe_pmu);
        if (ret)
                goto out_teardown_dev;

        return 0;

out_teardown_dev:
        arm_spe_pmu_dev_teardown(spe_pmu);
out_free_handle:
        free_percpu(spe_pmu->handle);
        return ret;
}

static int arm_spe_pmu_device_remove(struct platform_device *pdev)
{
        struct arm_spe_pmu *spe_pmu = platform_get_drvdata(pdev);

        arm_spe_pmu_perf_destroy(spe_pmu);
        arm_spe_pmu_dev_teardown(spe_pmu);
        free_percpu(spe_pmu->handle);
        return 0;
}

static struct platform_driver arm_spe_pmu_driver = {
        .driver = {
                .name           = DRVNAME,
                .of_match_table = of_match_ptr(arm_spe_pmu_of_match),
        },
        .probe  = arm_spe_pmu_device_dt_probe,
        .remove = arm_spe_pmu_device_remove,
};

static int __init arm_spe_pmu_init(void)
{
        int ret;

        ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, DRVNAME,
                                      arm_spe_pmu_cpu_startup,
                                      arm_spe_pmu_cpu_teardown);
        if (ret < 0)
                return ret;
        arm_spe_pmu_online = ret;

        ret = platform_driver_register(&arm_spe_pmu_driver);
        if (ret)
                cpuhp_remove_multi_state(arm_spe_pmu_online);

        return ret;
}

static void __exit arm_spe_pmu_exit(void)
{
        platform_driver_unregister(&arm_spe_pmu_driver);
        cpuhp_remove_multi_state(arm_spe_pmu_online);
}

module_init(arm_spe_pmu_init);
module_exit(arm_spe_pmu_exit);

MODULE_DESCRIPTION("Perf driver for the ARMv8.2 Statistical Profiling Extension");
MODULE_AUTHOR("Will Deacon <will.deacon@arm.com>");
MODULE_LICENSE("GPL v2");