/*
 * Hypervisor supplied "24x7" performance counter support
 *
 * Author: Cody P Schafer <cody@linux.vnet.ibm.com>
 * Copyright 2014 IBM Corporation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#define pr_fmt(fmt) "hv-24x7: " fmt

#include <linux/perf_event.h>
#include <linux/rbtree.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>

#include <asm/cputhreads.h>
#include <asm/firmware.h>
#include <asm/hvcall.h>
#include <asm/io.h>
#include <linux/byteorder/generic.h>

#include "hv-24x7.h"
#include "hv-24x7-catalog.h"
#include "hv-common.h"

/* Version of the 24x7 hypervisor API that we should use in this machine. */
static int interface_version;

/* Whether we have to aggregate result data for some domains. */
static bool aggregate_result_elements;

static bool domain_is_valid(unsigned domain)
{
        switch (domain) {
#define DOMAIN(n, v, x, c)              \
        case HV_PERF_DOMAIN_##n:        \
                /* fall through */
#include "hv-24x7-domains.h"
#undef DOMAIN
                return true;
        default:
                return false;
        }
}

static bool is_physical_domain(unsigned domain)
{
        switch (domain) {
#define DOMAIN(n, v, x, c)              \
        case HV_PERF_DOMAIN_##n:        \
                return c;
#include "hv-24x7-domains.h"
#undef DOMAIN
        default:
                return false;
        }
}

/* Domains for which more than one result element are returned for each event. */
static bool domain_needs_aggregation(unsigned int domain)
{
        return aggregate_result_elements &&
                        (domain == HV_PERF_DOMAIN_PHYS_CORE ||
                         (domain >= HV_PERF_DOMAIN_VCPU_HOME_CORE &&
                          domain <= HV_PERF_DOMAIN_VCPU_REMOTE_NODE));
}

static const char *domain_name(unsigned domain)
{
        if (!domain_is_valid(domain))
                return NULL;

        switch (domain) {
        case HV_PERF_DOMAIN_PHYS_CHIP:          return "Physical Chip";
        case HV_PERF_DOMAIN_PHYS_CORE:          return "Physical Core";
        case HV_PERF_DOMAIN_VCPU_HOME_CORE:     return "VCPU Home Core";
        case HV_PERF_DOMAIN_VCPU_HOME_CHIP:     return "VCPU Home Chip";
        case HV_PERF_DOMAIN_VCPU_HOME_NODE:     return "VCPU Home Node";
        case HV_PERF_DOMAIN_VCPU_REMOTE_NODE:   return "VCPU Remote Node";
        }

        WARN_ON_ONCE(domain);
        return NULL;
}

static bool catalog_entry_domain_is_valid(unsigned domain)
{
        /* POWER8 doesn't support virtual domains. */
        if (interface_version == 1)
                return is_physical_domain(domain);
        else
                return domain_is_valid(domain);
}

/*
 * TODO: Merging events:
 * - Think of the hcall as an interface to a 4d array of counters:
 *   - x = domains
 *   - y = indexes in the domain (core, chip, vcpu, node, etc)
 *   - z = offset into the counter space
 *   - w = lpars (guest vms, "logical partitions")
 * - A single request is: x,y,y_last,z,z_last,w,w_last
 *   - this means we can retrieve a rectangle of counters in y,z for a single x.
 *
 * - Things to consider (ignoring w):
 *   - input  cost_per_request = 16
 *   - output cost_per_result(ys,zs)  = 8 + 8 * ys + ys * zs
 *   - limited number of requests per hcall (must fit into 4K bytes)
 *     - 4k = 16 [buffer header] - 16 [request size] * request_count
 *     - 255 requests per hcall
 *   - sometimes it will be more efficient to read extra data and discard
 */

/*
 * Example usage:
 *  perf stat -e 'hv_24x7/domain=2,offset=8,vcpu=0,lpar=0xffffffff/'
 */

/* u3 0-6, one of HV_24X7_PERF_DOMAIN */
EVENT_DEFINE_RANGE_FORMAT(domain, config, 0, 3);
/* u16 */
EVENT_DEFINE_RANGE_FORMAT(core, config, 16, 31);
EVENT_DEFINE_RANGE_FORMAT(chip, config, 16, 31);
EVENT_DEFINE_RANGE_FORMAT(vcpu, config, 16, 31);
/* u32, see "data_offset" */
EVENT_DEFINE_RANGE_FORMAT(offset, config, 32, 63);
/* u16 */
EVENT_DEFINE_RANGE_FORMAT(lpar, config1, 0, 15);

EVENT_DEFINE_RANGE(reserved1, config,   4, 15);
EVENT_DEFINE_RANGE(reserved2, config1, 16, 63);
EVENT_DEFINE_RANGE(reserved3, config2,  0, 63);

static struct attribute *format_attrs[] = {
        &format_attr_domain.attr,
        &format_attr_offset.attr,
        &format_attr_core.attr,
        &format_attr_chip.attr,
        &format_attr_vcpu.attr,
        &format_attr_lpar.attr,
        NULL,
};

static struct attribute_group format_group = {
        .name = "format",
        .attrs = format_attrs,
};

static struct attribute_group event_group = {
        .name = "events",
        /* .attrs is set in init */
};

static struct attribute_group event_desc_group = {
        .name = "event_descs",
        /* .attrs is set in init */
};

static struct attribute_group event_long_desc_group = {
        .name = "event_long_descs",
        /* .attrs is set in init */
};

static struct kmem_cache *hv_page_cache;

DEFINE_PER_CPU(int, hv_24x7_txn_flags);
DEFINE_PER_CPU(int, hv_24x7_txn_err);

struct hv_24x7_hw {
        struct perf_event *events[255];
};

DEFINE_PER_CPU(struct hv_24x7_hw, hv_24x7_hw);

/*
 * request_buffer and result_buffer are not required to be 4k aligned,
 * but are not allowed to cross any 4k boundary. Aligning them to 4k is
 * the simplest way to ensure that.
 */
#define H24x7_DATA_BUFFER_SIZE  4096
DEFINE_PER_CPU(char, hv_24x7_reqb[H24x7_DATA_BUFFER_SIZE]) __aligned(4096);
DEFINE_PER_CPU(char, hv_24x7_resb[H24x7_DATA_BUFFER_SIZE]) __aligned(4096);

static unsigned int max_num_requests(int interface_version)
{
        return (H24x7_DATA_BUFFER_SIZE - sizeof(struct hv_24x7_request_buffer))
                / H24x7_REQUEST_SIZE(interface_version);
}

static char *event_name(struct hv_24x7_event_data *ev, int *len)
{
        *len = be16_to_cpu(ev->event_name_len) - 2;
        return (char *)ev->remainder;
}

static char *event_desc(struct hv_24x7_event_data *ev, int *len)
{
        unsigned nl = be16_to_cpu(ev->event_name_len);
        __be16 *desc_len = (__be16 *)(ev->remainder + nl - 2);

        *len = be16_to_cpu(*desc_len) - 2;
        return (char *)ev->remainder + nl;
}

static char *event_long_desc(struct hv_24x7_event_data *ev, int *len)
{
        unsigned nl = be16_to_cpu(ev->event_name_len);
        __be16 *desc_len_ = (__be16 *)(ev->remainder + nl - 2);
        unsigned desc_len = be16_to_cpu(*desc_len_);
        __be16 *long_desc_len = (__be16 *)(ev->remainder + nl + desc_len - 2);

        *len = be16_to_cpu(*long_desc_len) - 2;
        return (char *)ev->remainder + nl + desc_len;
}

static bool event_fixed_portion_is_within(struct hv_24x7_event_data *ev,
                                          void *end)
{
        void *start = ev;

        return (start + offsetof(struct hv_24x7_event_data, remainder)) < end;
}

/*
 * Things we don't check:
 *  - padding for desc, name, and long/detailed desc is required to be '\0'
 *    bytes.
 *
 *  Return NULL if we pass end,
 *  Otherwise return the address of the byte just following the event.
 */
static void *event_end(struct hv_24x7_event_data *ev, void *end)
{
        void *start = ev;
        __be16 *dl_, *ldl_;
        unsigned dl, ldl;
        unsigned nl = be16_to_cpu(ev->event_name_len);

        if (nl < 2) {
                pr_debug("%s: name length too short: %d", __func__, nl);
                return NULL;
        }

        if (start + nl > end) {
                pr_debug("%s: start=%p + nl=%u > end=%p",
                                __func__, start, nl, end);
                return NULL;
        }

        dl_ = (__be16 *)(ev->remainder + nl - 2);
        if (!IS_ALIGNED((uintptr_t)dl_, 2))
                pr_warn("desc len not aligned %p", dl_);
        dl = be16_to_cpu(*dl_);
        if (dl < 2) {
                pr_debug("%s: desc len too short: %d", __func__, dl);
                return NULL;
        }

        if (start + nl + dl > end) {
                pr_debug("%s: (start=%p + nl=%u + dl=%u)=%p > end=%p",
                                __func__, start, nl, dl, start + nl + dl, end);
                return NULL;
        }

        ldl_ = (__be16 *)(ev->remainder + nl + dl - 2);
        if (!IS_ALIGNED((uintptr_t)ldl_, 2))
                pr_warn("long desc len not aligned %p", ldl_);
        ldl = be16_to_cpu(*ldl_);
        if (ldl < 2) {
                pr_debug("%s: long desc len too short (ldl=%u)",
                                __func__, ldl);
                return NULL;
        }

        if (start + nl + dl + ldl > end) {
                pr_debug("%s: start=%p + nl=%u + dl=%u + ldl=%u > end=%p",
                                __func__, start, nl, dl, ldl, end);
                return NULL;
        }

        return start + nl + dl + ldl;
}

static long h_get_24x7_catalog_page_(unsigned long phys_4096,
                                     unsigned long version, unsigned long index)
{
        pr_devel("h_get_24x7_catalog_page(0x%lx, %lu, %lu)",
                        phys_4096, version, index);

        WARN_ON(!IS_ALIGNED(phys_4096, 4096));

        return plpar_hcall_norets(H_GET_24X7_CATALOG_PAGE,
                        phys_4096, version, index);
}

static long h_get_24x7_catalog_page(char page[], u64 version, u32 index)
{
        return h_get_24x7_catalog_page_(virt_to_phys(page),
                                        version, index);
}

/*
 * Each event we find in the catalog, will have a sysfs entry. Format the
 * data for this sysfs entry based on the event's domain.
 *
 * Events belonging to the Chip domain can only be monitored in that domain.
 * i.e the domain for these events is a fixed/knwon value.
 *
 * Events belonging to the Core domain can be monitored either in the physical
 * core or in one of the virtual CPU domains. So the domain value for these
 * events must be specified by the user (i.e is a required parameter). Format
 * the Core events with 'domain=?' so the perf-tool can error check required
 * parameters.
 *
 * NOTE: For the Core domain events, rather than making domain a required
 *       parameter we could default it to PHYS_CORE and allowe users to
 *       override the domain to one of the VCPU domains.
 *
 *       However, this can make the interface a little inconsistent.
 *
 *       If we set domain=2 (PHYS_CHIP) and allow user to override this field
 *       the user may be tempted to also modify the "offset=x" field in which
 *       can lead to confusing usage. Consider the HPM_PCYC (offset=0x18) and
 *       HPM_INST (offset=0x20) events. With:
 *
 *              perf stat -e hv_24x7/HPM_PCYC,offset=0x20/
 *
 *      we end up monitoring HPM_INST, while the command line has HPM_PCYC.
 *
 *      By not assigning a default value to the domain for the Core events,
 *      we can have simple guidelines:
 *
 *              - Specifying values for parameters with "=?" is required.
 *
 *              - Specifying (i.e overriding) values for other parameters
 *                is undefined.
 */
static char *event_fmt(struct hv_24x7_event_data *event, unsigned domain)
{
        const char *sindex;
        const char *lpar;
        const char *domain_str;
        char buf[8];

        switch (domain) {
        case HV_PERF_DOMAIN_PHYS_CHIP:
                snprintf(buf, sizeof(buf), "%d", domain);
                domain_str = buf;
                lpar = "0x0";
                sindex = "chip";
                break;
        case HV_PERF_DOMAIN_PHYS_CORE:
                domain_str = "?";
                lpar = "0x0";
                sindex = "core";
                break;
        default:
                domain_str = "?";
                lpar = "?";
                sindex = "vcpu";
        }

        return kasprintf(GFP_KERNEL,
                        "domain=%s,offset=0x%x,%s=?,lpar=%s",
                        domain_str,
                        be16_to_cpu(event->event_counter_offs) +
                                be16_to_cpu(event->event_group_record_offs),
                        sindex,
                        lpar);
}

/* Avoid trusting fw to NUL terminate strings */
static char *memdup_to_str(char *maybe_str, int max_len, gfp_t gfp)
{
        return kasprintf(gfp, "%.*s", max_len, maybe_str);
}

static ssize_t device_show_string(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct dev_ext_attribute *d;

        d = container_of(attr, struct dev_ext_attribute, attr);

        return sprintf(buf, "%s\n", (char *)d->var);
}

static struct attribute *device_str_attr_create_(char *name, char *str)
{
        struct dev_ext_attribute *attr = kzalloc(sizeof(*attr), GFP_KERNEL);

        if (!attr)
                return NULL;

        sysfs_attr_init(&attr->attr.attr);

        attr->var = str;
        attr->attr.attr.name = name;
        attr->attr.attr.mode = 0444;
        attr->attr.show = device_show_string;

        return &attr->attr.attr;
}

/*
 * Allocate and initialize strings representing event attributes.
 *
 * NOTE: The strings allocated here are never destroyed and continue to
 *       exist till shutdown. This is to allow us to create as many events
 *       from the catalog as possible, even if we encounter errors with some.
 *       In case of changes to error paths in future, these may need to be
 *       freed by the caller.
 */
static struct attribute *device_str_attr_create(char *name, int name_max,
                                                int name_nonce,
                                                char *str, size_t str_max)
{
        char *n;
        char *s = memdup_to_str(str, str_max, GFP_KERNEL);
        struct attribute *a;

        if (!s)
                return NULL;

        if (!name_nonce)
                n = kasprintf(GFP_KERNEL, "%.*s", name_max, name);
        else
                n = kasprintf(GFP_KERNEL, "%.*s__%d", name_max, name,
                                        name_nonce);
        if (!n)
                goto out_s;

        a = device_str_attr_create_(n, s);
        if (!a)
                goto out_n;

        return a;
out_n:
        kfree(n);
out_s:
        kfree(s);
        return NULL;
}

static struct attribute *event_to_attr(unsigned ix,
                                       struct hv_24x7_event_data *event,
                                       unsigned domain,
                                       int nonce)
{
        int event_name_len;
        char *ev_name, *a_ev_name, *val;
        struct attribute *attr;

        if (!domain_is_valid(domain)) {
                pr_warn("catalog event %u has invalid domain %u\n",
                                ix, domain);
                return NULL;
        }

        val = event_fmt(event, domain);
        if (!val)
                return NULL;

        ev_name = event_name(event, &event_name_len);
        if (!nonce)
                a_ev_name = kasprintf(GFP_KERNEL, "%.*s",
                                (int)event_name_len, ev_name);
        else
                a_ev_name = kasprintf(GFP_KERNEL, "%.*s__%d",
                                (int)event_name_len, ev_name, nonce);

        if (!a_ev_name)
                goto out_val;

        attr = device_str_attr_create_(a_ev_name, val);
        if (!attr)
                goto out_name;

        return attr;
out_name:
        kfree(a_ev_name);
out_val:
        kfree(val);
        return NULL;
}

static struct attribute *event_to_desc_attr(struct hv_24x7_event_data *event,
                                            int nonce)
{
        int nl, dl;
        char *name = event_name(event, &nl);
        char *desc = event_desc(event, &dl);

        /* If there isn't a description, don't create the sysfs file */
        if (!dl)
                return NULL;

        return device_str_attr_create(name, nl, nonce, desc, dl);
}

static struct attribute *
event_to_long_desc_attr(struct hv_24x7_event_data *event, int nonce)
{
        int nl, dl;
        char *name = event_name(event, &nl);
        char *desc = event_long_desc(event, &dl);

        /* If there isn't a description, don't create the sysfs file */
        if (!dl)
                return NULL;

        return device_str_attr_create(name, nl, nonce, desc, dl);
}

static int event_data_to_attrs(unsigned ix, struct attribute **attrs,
                                   struct hv_24x7_event_data *event, int nonce)
{
        *attrs = event_to_attr(ix, event, event->domain, nonce);
        if (!*attrs)
                return -1;

        return 0;
}

/* */
struct event_uniq {
        struct rb_node node;
        const char *name;
        int nl;
        unsigned ct;
        unsigned domain;
};

static int memord(const void *d1, size_t s1, const void *d2, size_t s2)
{
        if (s1 < s2)
                return 1;
        if (s1 > s2)
                return -1;

        return memcmp(d1, d2, s1);
}

static int ev_uniq_ord(const void *v1, size_t s1, unsigned d1, const void *v2,
                       size_t s2, unsigned d2)
{
        int r = memord(v1, s1, v2, s2);

        if (r)
                return r;
        if (d1 > d2)
                return 1;
        if (d2 > d1)
                return -1;
        return 0;
}

static int event_uniq_add(struct rb_root *root, const char *name, int nl,
                          unsigned domain)
{
        struct rb_node **new = &(root->rb_node), *parent = NULL;
        struct event_uniq *data;

        /* Figure out where to put new node */
        while (*new) {
                struct event_uniq *it;
                int result;

                it = container_of(*new, struct event_uniq, node);
                result = ev_uniq_ord(name, nl, domain, it->name, it->nl,
                                        it->domain);

                parent = *new;
                if (result < 0)
                        new = &((*new)->rb_left);
                else if (result > 0)
                        new = &((*new)->rb_right);
                else {
                        it->ct++;
                        pr_info("found a duplicate event %.*s, ct=%u\n", nl,
                                                name, it->ct);
                        return it->ct;
                }
        }

        data = kmalloc(sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        *data = (struct event_uniq) {
                .name = name,
                .nl = nl,
                .ct = 0,
                .domain = domain,
        };

        /* Add new node and rebalance tree. */
        rb_link_node(&data->node, parent, new);
        rb_insert_color(&data->node, root);

        /* data->ct */
        return 0;
}

static void event_uniq_destroy(struct rb_root *root)
{
        /*
         * the strings we point to are in the giant block of memory filled by
         * the catalog, and are freed separately.
         */
        struct event_uniq *pos, *n;

        rbtree_postorder_for_each_entry_safe(pos, n, root, node)
                kfree(pos);
}


/*
 * ensure the event structure's sizes are self consistent and don't cause us to
 * read outside of the event
 *
 * On success, return the event length in bytes.
 * Otherwise, return -1 (and print as appropriate).
 */
static ssize_t catalog_event_len_validate(struct hv_24x7_event_data *event,
                                          size_t event_idx,
                                          size_t event_data_bytes,
                                          size_t event_entry_count,
                                          size_t offset, void *end)
{
        ssize_t ev_len;
        void *ev_end, *calc_ev_end;

        if (offset >= event_data_bytes)
                return -1;

        if (event_idx >= event_entry_count) {
                pr_devel("catalog event data has %zu bytes of padding after last event\n",
                                event_data_bytes - offset);
                return -1;
        }

        if (!event_fixed_portion_is_within(event, end)) {
                pr_warn("event %zu fixed portion is not within range\n",
                                event_idx);
                return -1;
        }

        ev_len = be16_to_cpu(event->length);

        if (ev_len % 16)
                pr_info("event %zu has length %zu not divisible by 16: event=%pK\n",
                                event_idx, ev_len, event);

        ev_end = (__u8 *)event + ev_len;
        if (ev_end > end) {
                pr_warn("event %zu has .length=%zu, ends after buffer end: ev_end=%pK > end=%pK, offset=%zu\n",
                                event_idx, ev_len, ev_end, end,
                                offset);
                return -1;
        }

        calc_ev_end = event_end(event, end);
        if (!calc_ev_end) {
                pr_warn("event %zu has a calculated length which exceeds buffer length %zu: event=%pK end=%pK, offset=%zu\n",
                        event_idx, event_data_bytes, event, end,
                        offset);
                return -1;
        }

        if (calc_ev_end > ev_end) {
                pr_warn("event %zu exceeds it's own length: event=%pK, end=%pK, offset=%zu, calc_ev_end=%pK\n",
                        event_idx, event, ev_end, offset, calc_ev_end);
                return -1;
        }

        return ev_len;
}

#define MAX_4K (SIZE_MAX / 4096)

static int create_events_from_catalog(struct attribute ***events_,
                                      struct attribute ***event_descs_,
                                      struct attribute ***event_long_descs_)
{
        long hret;
        size_t catalog_len, catalog_page_len, event_entry_count,
               event_data_len, event_data_offs,
               event_data_bytes, junk_events, event_idx, event_attr_ct, i,
               attr_max, event_idx_last, desc_ct, long_desc_ct;
        ssize_t ct, ev_len;
        uint64_t catalog_version_num;
        struct attribute **events, **event_descs, **event_long_descs;
        struct hv_24x7_catalog_page_0 *page_0 =
                kmem_cache_alloc(hv_page_cache, GFP_KERNEL);
        void *page = page_0;
        void *event_data, *end;
        struct hv_24x7_event_data *event;
        struct rb_root ev_uniq = RB_ROOT;
        int ret = 0;

        if (!page) {
                ret = -ENOMEM;
                goto e_out;
        }

        hret = h_get_24x7_catalog_page(page, 0, 0);
        if (hret) {
                ret = -EIO;
                goto e_free;
        }

        catalog_version_num = be64_to_cpu(page_0->version);
        catalog_page_len = be32_to_cpu(page_0->length);

        if (MAX_4K < catalog_page_len) {
                pr_err("invalid page count: %zu\n", catalog_page_len);
                ret = -EIO;
                goto e_free;
        }

        catalog_len = catalog_page_len * 4096;

        event_entry_count = be16_to_cpu(page_0->event_entry_count);
        event_data_offs   = be16_to_cpu(page_0->event_data_offs);
        event_data_len    = be16_to_cpu(page_0->event_data_len);

        pr_devel("cv %llu cl %zu eec %zu edo %zu edl %zu\n",
                        catalog_version_num, catalog_len,
                        event_entry_count, event_data_offs, event_data_len);

        if ((MAX_4K < event_data_len)
                        || (MAX_4K < event_data_offs)
                        || (MAX_4K - event_data_offs < event_data_len)) {
                pr_err("invalid event data offs %zu and/or len %zu\n",
                                event_data_offs, event_data_len);
                ret = -EIO;
                goto e_free;
        }

        if ((event_data_offs + event_data_len) > catalog_page_len) {
                pr_err("event data %zu-%zu does not fit inside catalog 0-%zu\n",
                                event_data_offs,
                                event_data_offs + event_data_len,
                                catalog_page_len);
                ret = -EIO;
                goto e_free;
        }

        if (SIZE_MAX - 1 < event_entry_count) {
                pr_err("event_entry_count %zu is invalid\n", event_entry_count);
                ret = -EIO;
                goto e_free;
        }

        event_data_bytes = event_data_len * 4096;

        /*
         * event data can span several pages, events can cross between these
         * pages. Use vmalloc to make this easier.
         */
        event_data = vmalloc(event_data_bytes);
        if (!event_data) {
                pr_err("could not allocate event data\n");
                ret = -ENOMEM;
                goto e_free;
        }

        end = event_data + event_data_bytes;

        /*
         * using vmalloc_to_phys() like this only works if PAGE_SIZE is
         * divisible by 4096
         */
        BUILD_BUG_ON(PAGE_SIZE % 4096);

        for (i = 0; i < event_data_len; i++) {
                hret = h_get_24x7_catalog_page_(
                                vmalloc_to_phys(event_data + i * 4096),
                                catalog_version_num,
                                i + event_data_offs);
                if (hret) {
                        pr_err("Failed to get event data in page %zu: rc=%ld\n",
                               i + event_data_offs, hret);
                        ret = -EIO;
                        goto e_event_data;
                }
        }

        /*
         * scan the catalog to determine the number of attributes we need, and
         * verify it at the same time.
         */
        for (junk_events = 0, event = event_data, event_idx = 0, attr_max = 0;
             ;
             event_idx++, event = (void *)event + ev_len) {
                size_t offset = (void *)event - (void *)event_data;
                char *name;
                int nl;

                ev_len = catalog_event_len_validate(event, event_idx,
                                                    event_data_bytes,
                                                    event_entry_count,
                                                    offset, end);
                if (ev_len < 0)
                        break;

                name = event_name(event, &nl);

                if (event->event_group_record_len == 0) {
                        pr_devel("invalid event %zu (%.*s): group_record_len == 0, skipping\n",
                                        event_idx, nl, name);
                        junk_events++;
                        continue;
                }

                if (!catalog_entry_domain_is_valid(event->domain)) {
                        pr_info("event %zu (%.*s) has invalid domain %d\n",
                                        event_idx, nl, name, event->domain);
                        junk_events++;
                        continue;
                }

                attr_max++;
        }

        event_idx_last = event_idx;
        if (event_idx_last != event_entry_count)
                pr_warn("event buffer ended before listed # of events were parsed (got %zu, wanted %zu, junk %zu)\n",
                                event_idx_last, event_entry_count, junk_events);

        events = kmalloc_array(attr_max + 1, sizeof(*events), GFP_KERNEL);
        if (!events) {
                ret = -ENOMEM;
                goto e_event_data;
        }

        event_descs = kmalloc_array(event_idx + 1, sizeof(*event_descs),
                                GFP_KERNEL);
        if (!event_descs) {
                ret = -ENOMEM;
                goto e_event_attrs;
        }

        event_long_descs = kmalloc_array(event_idx + 1,
                        sizeof(*event_long_descs), GFP_KERNEL);
        if (!event_long_descs) {
                ret = -ENOMEM;
                goto e_event_descs;
        }

        /* Iterate over the catalog filling in the attribute vector */
        for (junk_events = 0, event_attr_ct = 0, desc_ct = 0, long_desc_ct = 0,
                                event = event_data, event_idx = 0;
                        event_idx < event_idx_last;
                        event_idx++, ev_len = be16_to_cpu(event->length),
                                event = (void *)event + ev_len) {
                char *name;
                int nl;
                int nonce;
                /*
                 * these are the only "bad" events that are intermixed and that
                 * we can ignore without issue. make sure to skip them here
                 */
                if (event->event_group_record_len == 0)
                        continue;
                if (!catalog_entry_domain_is_valid(event->domain))
                        continue;

                name  = event_name(event, &nl);
                nonce = event_uniq_add(&ev_uniq, name, nl, event->domain);
                ct    = event_data_to_attrs(event_idx, events + event_attr_ct,
                                            event, nonce);
                if (ct < 0) {
                        pr_warn("event %zu (%.*s) creation failure, skipping\n",
                                event_idx, nl, name);
                        junk_events++;
                } else {
                        event_attr_ct++;
                        event_descs[desc_ct] = event_to_desc_attr(event, nonce);
                        if (event_descs[desc_ct])
                                desc_ct++;
                        event_long_descs[long_desc_ct] =
                                        event_to_long_desc_attr(event, nonce);
                        if (event_long_descs[long_desc_ct])
                                long_desc_ct++;
                }
        }

        pr_info("read %zu catalog entries, created %zu event attrs (%zu failures), %zu descs\n",
                        event_idx, event_attr_ct, junk_events, desc_ct);

        events[event_attr_ct] = NULL;
        event_descs[desc_ct] = NULL;
        event_long_descs[long_desc_ct] = NULL;

        event_uniq_destroy(&ev_uniq);
        vfree(event_data);
        kmem_cache_free(hv_page_cache, page);

        *events_ = events;
        *event_descs_ = event_descs;
        *event_long_descs_ = event_long_descs;
        return 0;

e_event_descs:
        kfree(event_descs);
e_event_attrs:
        kfree(events);
e_event_data:
        vfree(event_data);
e_free:
        kmem_cache_free(hv_page_cache, page);
e_out:
        *events_ = NULL;
        *event_descs_ = NULL;
        *event_long_descs_ = NULL;
        return ret;
}

static ssize_t catalog_read(struct file *filp, struct kobject *kobj,
                            struct bin_attribute *bin_attr, char *buf,
                            loff_t offset, size_t count)
{
        long hret;
        ssize_t ret = 0;
        size_t catalog_len = 0, catalog_page_len = 0;
        loff_t page_offset = 0;
        loff_t offset_in_page;
        size_t copy_len;
        uint64_t catalog_version_num = 0;
        void *page = kmem_cache_alloc(hv_page_cache, GFP_USER);
        struct hv_24x7_catalog_page_0 *page_0 = page;

        if (!page)
                return -ENOMEM;

        hret = h_get_24x7_catalog_page(page, 0, 0);
        if (hret) {
                ret = -EIO;
                goto e_free;
        }

        catalog_version_num = be64_to_cpu(page_0->version);
        catalog_page_len = be32_to_cpu(page_0->length);
        catalog_len = catalog_page_len * 4096;

        page_offset = offset / 4096;
        offset_in_page = offset % 4096;

        if (page_offset >= catalog_page_len)
                goto e_free;

        if (page_offset != 0) {
                hret = h_get_24x7_catalog_page(page, catalog_version_num,
                                               page_offset);
                if (hret) {
                        ret = -EIO;
                        goto e_free;
                }
        }

        copy_len = 4096 - offset_in_page;
        if (copy_len > count)
                copy_len = count;

        memcpy(buf, page+offset_in_page, copy_len);
        ret = copy_len;

e_free:
        if (hret)
                pr_err("h_get_24x7_catalog_page(ver=%lld, page=%lld) failed:"
                       " rc=%ld\n",
                       catalog_version_num, page_offset, hret);
        kmem_cache_free(hv_page_cache, page);

        pr_devel("catalog_read: offset=%lld(%lld) count=%zu "
                        "catalog_len=%zu(%zu) => %zd\n", offset, page_offset,
                        count, catalog_len, catalog_page_len, ret);

        return ret;
}

static ssize_t domains_show(struct device *dev, struct device_attribute *attr,
                            char *page)
{
        int d, n, count = 0;
        const char *str;

        for (d = 0; d < HV_PERF_DOMAIN_MAX; d++) {
                str = domain_name(d);
                if (!str)
                        continue;

                n = sprintf(page, "%d: %s\n", d, str);

                if (n < 0)
                        break;

                count += n;
                page += n;
        }
        return count;
}

#define PAGE_0_ATTR(_name, _fmt, _expr)                         \
static ssize_t _name##_show(struct device *dev,                 \
                            struct device_attribute *dev_attr,  \
                            char *buf)                          \
{                                                               \
        long hret;                                              \
        ssize_t ret = 0;                                        \
        void *page = kmem_cache_alloc(hv_page_cache, GFP_USER); \
        struct hv_24x7_catalog_page_0 *page_0 = page;           \
        if (!page)                                              \
                return -ENOMEM;                                 \
        hret = h_get_24x7_catalog_page(page, 0, 0);             \
        if (hret) {                                             \
                ret = -EIO;                                     \
                goto e_free;                                    \
        }                                                       \
        ret = sprintf(buf, _fmt, _expr);                        \
e_free:                                                         \
        kmem_cache_free(hv_page_cache, page);                   \
        return ret;                                             \
}                                                               \
static DEVICE_ATTR_RO(_name)

PAGE_0_ATTR(catalog_version, "%lld\n",
                (unsigned long long)be64_to_cpu(page_0->version));
PAGE_0_ATTR(catalog_len, "%lld\n",
                (unsigned long long)be32_to_cpu(page_0->length) * 4096);
static BIN_ATTR_RO(catalog, 0/* real length varies */);
static DEVICE_ATTR_RO(domains);

static struct bin_attribute *if_bin_attrs[] = {
        &bin_attr_catalog,
        NULL,
};

static struct attribute *if_attrs[] = {
        &dev_attr_catalog_len.attr,
        &dev_attr_catalog_version.attr,
        &dev_attr_domains.attr,
        NULL,
};

static struct attribute_group if_group = {
        .name = "interface",
        .bin_attrs = if_bin_attrs,
        .attrs = if_attrs,
};

static const struct attribute_group *attr_groups[] = {
        &format_group,
        &event_group,
        &event_desc_group,
        &event_long_desc_group,
        &if_group,
        NULL,
};

/*
 * Start the process for a new H_GET_24x7_DATA hcall.
 */
static void init_24x7_request(struct hv_24x7_request_buffer *request_buffer,
                              struct hv_24x7_data_result_buffer *result_buffer)
{

        memset(request_buffer, 0, H24x7_DATA_BUFFER_SIZE);
        memset(result_buffer, 0, H24x7_DATA_BUFFER_SIZE);

        request_buffer->interface_version = interface_version;
        /* memset above set request_buffer->num_requests to 0 */
}

/*
 * Commit (i.e perform) the H_GET_24x7_DATA hcall using the data collected
 * by 'init_24x7_request()' and 'add_event_to_24x7_request()'.
 */
static int make_24x7_request(struct hv_24x7_request_buffer *request_buffer,
                             struct hv_24x7_data_result_buffer *result_buffer)
{
        long ret;

        /*
         * NOTE: Due to variable number of array elements in request and
         *       result buffer(s), sizeof() is not reliable. Use the actual
         *       allocated buffer size, H24x7_DATA_BUFFER_SIZE.
         */
        ret = plpar_hcall_norets(H_GET_24X7_DATA,
                        virt_to_phys(request_buffer), H24x7_DATA_BUFFER_SIZE,
                        virt_to_phys(result_buffer),  H24x7_DATA_BUFFER_SIZE);

        if (ret) {
                struct hv_24x7_request *req;

                req = request_buffer->requests;
                pr_notice_ratelimited("hcall failed: [%d %#x %#x %d] => ret 0x%lx (%ld) detail=0x%x failing ix=%x\n",
                                      req->performance_domain, req->data_offset,
                                      req->starting_ix, req->starting_lpar_ix,
                                      ret, ret, result_buffer->detailed_rc,
                                      result_buffer->failing_request_ix);
                return -EIO;
        }

        return 0;
}

/*
 * Add the given @event to the next slot in the 24x7 request_buffer.
 *
 * Note that H_GET_24X7_DATA hcall allows reading several counters'
 * values in a single HCALL. We expect the caller to add events to the
 * request buffer one by one, make the HCALL and process the results.
 */
static int add_event_to_24x7_request(struct perf_event *event,
                                struct hv_24x7_request_buffer *request_buffer)
{
        u16 idx;
        int i;
        size_t req_size;
        struct hv_24x7_request *req;

        if (request_buffer->num_requests >=
            max_num_requests(request_buffer->interface_version)) {
                pr_devel("Too many requests for 24x7 HCALL %d\n",
                                request_buffer->num_requests);
                return -EINVAL;
        }

        switch (event_get_domain(event)) {
        case HV_PERF_DOMAIN_PHYS_CHIP:
                idx = event_get_chip(event);
                break;
        case HV_PERF_DOMAIN_PHYS_CORE:
                idx = event_get_core(event);
                break;
        default:
                idx = event_get_vcpu(event);
        }

        req_size = H24x7_REQUEST_SIZE(request_buffer->interface_version);

        i = request_buffer->num_requests++;
        req = (void *) request_buffer->requests + i * req_size;

        req->performance_domain = event_get_domain(event);
        req->data_size = cpu_to_be16(8);
        req->data_offset = cpu_to_be32(event_get_offset(event));
        req->starting_lpar_ix = cpu_to_be16(event_get_lpar(event));
        req->max_num_lpars = cpu_to_be16(1);
        req->starting_ix = cpu_to_be16(idx);
        req->max_ix = cpu_to_be16(1);

        if (request_buffer->interface_version > 1) {
                if (domain_needs_aggregation(req->performance_domain))
                        req->max_num_thread_groups = -1;
                else if (req->performance_domain != HV_PERF_DOMAIN_PHYS_CHIP) {
                        req->starting_thread_group_ix = idx % 2;
                        req->max_num_thread_groups = 1;
                }
        }

        return 0;
}

/**
 * get_count_from_result - get event count from all result elements in result
 *
 * If the event corresponding to this result needs aggregation of the result
 * element values, then this function does that.
 *
 * @event:      Event associated with @res.
 * @resb:       Result buffer containing @res.
 * @res:        Result to work on.
 * @countp:     Output variable containing the event count.
 * @next:       Optional output variable pointing to the next result in @resb.
 */
static int get_count_from_result(struct perf_event *event,
                                 struct hv_24x7_data_result_buffer *resb,
                                 struct hv_24x7_result *res, u64 *countp,
                                 struct hv_24x7_result **next)
{
        u16 num_elements = be16_to_cpu(res->num_elements_returned);
        u16 data_size = be16_to_cpu(res->result_element_data_size);
        unsigned int data_offset;
        void *element_data;
        int i;
        u64 count;

        /*
         * We can bail out early if the result is empty.
         */
        if (!num_elements) {
                pr_debug("Result of request %hhu is empty, nothing to do\n",
                         res->result_ix);

                if (next)
                        *next = (struct hv_24x7_result *) res->elements;

                return -ENODATA;
        }

        /*
         * Since we always specify 1 as the maximum for the smallest resource
         * we're requesting, there should to be only one element per result.
         * Except when an event needs aggregation, in which case there are more.
         */
        if (num_elements != 1 &&
            !domain_needs_aggregation(event_get_domain(event))) {
                pr_err("Error: result of request %hhu has %hu elements\n",
                       res->result_ix, num_elements);

                return -EIO;
        }

        if (data_size != sizeof(u64)) {
                pr_debug("Error: result of request %hhu has data of %hu bytes\n",
                         res->result_ix, data_size);

                return -ENOTSUPP;
        }

        if (resb->interface_version == 1)
                data_offset = offsetof(struct hv_24x7_result_element_v1,
                                       element_data);
        else
                data_offset = offsetof(struct hv_24x7_result_element_v2,
                                       element_data);

        /* Go through the result elements in the result. */
        for (i = count = 0, element_data = res->elements + data_offset;
             i < num_elements;
             i++, element_data += data_size + data_offset)
                count += be64_to_cpu(*((u64 *) element_data));

        *countp = count;

        /* The next result is after the last result element. */
        if (next)
                *next = element_data - data_offset;

        return 0;
}

static int single_24x7_request(struct perf_event *event, u64 *count)
{
        int ret;
        struct hv_24x7_request_buffer *request_buffer;
        struct hv_24x7_data_result_buffer *result_buffer;

        BUILD_BUG_ON(sizeof(*request_buffer) > 4096);
        BUILD_BUG_ON(sizeof(*result_buffer) > 4096);

        request_buffer = (void *)get_cpu_var(hv_24x7_reqb);
        result_buffer = (void *)get_cpu_var(hv_24x7_resb);

        init_24x7_request(request_buffer, result_buffer);

        ret = add_event_to_24x7_request(event, request_buffer);
        if (ret)
                goto out;

        ret = make_24x7_request(request_buffer, result_buffer);
        if (ret)
                goto out;

        /* process result from hcall */
        ret = get_count_from_result(event, result_buffer,
                                    result_buffer->results, count, NULL);

out:
        put_cpu_var(hv_24x7_reqb);
        put_cpu_var(hv_24x7_resb);
        return ret;
}


static int h_24x7_event_init(struct perf_event *event)
{
        struct hv_perf_caps caps;
        unsigned domain;
        unsigned long hret;
        u64 ct;

        /* Not our event */
        if (event->attr.type != event->pmu->type)
                return -ENOENT;

        /* Unused areas must be 0 */
        if (event_get_reserved1(event) ||
            event_get_reserved2(event) ||
            event_get_reserved3(event)) {
                pr_devel("reserved set when forbidden 0x%llx(0x%llx) 0x%llx(0x%llx) 0x%llx(0x%llx)\n",
                                event->attr.config,
                                event_get_reserved1(event),
                                event->attr.config1,
                                event_get_reserved2(event),
                                event->attr.config2,
                                event_get_reserved3(event));
                return -EINVAL;
        }

        /* unsupported modes and filters */
        if (event->attr.exclude_user   ||
            event->attr.exclude_kernel ||
            event->attr.exclude_hv     ||
            event->attr.exclude_idle   ||
            event->attr.exclude_host   ||
            event->attr.exclude_guest)
                return -EINVAL;

        /* no branch sampling */
        if (has_branch_stack(event))
                return -EOPNOTSUPP;

        /* offset must be 8 byte aligned */
        if (event_get_offset(event) % 8) {
                pr_devel("bad alignment\n");
                return -EINVAL;
        }

        domain = event_get_domain(event);
        if (domain >= HV_PERF_DOMAIN_MAX) {
                pr_devel("invalid domain %d\n", domain);
                return -EINVAL;
        }

        hret = hv_perf_caps_get(&caps);
        if (hret) {
                pr_devel("could not get capabilities: rc=%ld\n", hret);
                return -EIO;
        }

        /* Physical domains & other lpars require extra capabilities */
        if (!caps.collect_privileged && (is_physical_domain(domain) ||
                (event_get_lpar(event) != event_get_lpar_max()))) {
                pr_devel("hv permissions disallow: is_physical_domain:%d, lpar=0x%llx\n",
                                is_physical_domain(domain),
                                event_get_lpar(event));
                return -EACCES;
        }

        /* Get the initial value of the counter for this event */
        if (single_24x7_request(event, &ct)) {
                pr_devel("test hcall failed\n");
                return -EIO;
        }
        (void)local64_xchg(&event->hw.prev_count, ct);

        return 0;
}

static u64 h_24x7_get_value(struct perf_event *event)
{
        u64 ct;

        if (single_24x7_request(event, &ct))
                /* We checked this in event init, shouldn't fail here... */
                return 0;

        return ct;
}

static void update_event_count(struct perf_event *event, u64 now)
{
        s64 prev;

        prev = local64_xchg(&event->hw.prev_count, now);
        local64_add(now - prev, &event->count);
}

static void h_24x7_event_read(struct perf_event *event)
{
        u64 now;
        struct hv_24x7_request_buffer *request_buffer;
        struct hv_24x7_hw *h24x7hw;
        int txn_flags;

        txn_flags = __this_cpu_read(hv_24x7_txn_flags);

        /*
         * If in a READ transaction, add this counter to the list of
         * counters to read during the next HCALL (i.e commit_txn()).
         * If not in a READ transaction, go ahead and make the HCALL
         * to read this counter by itself.
         */

        if (txn_flags & PERF_PMU_TXN_READ) {
                int i;
                int ret;

                if (__this_cpu_read(hv_24x7_txn_err))
                        return;

                request_buffer = (void *)get_cpu_var(hv_24x7_reqb);

                ret = add_event_to_24x7_request(event, request_buffer);
                if (ret) {
                        __this_cpu_write(hv_24x7_txn_err, ret);
                } else {
                        /*
                         * Associate the event with the HCALL request index,
                         * so ->commit_txn() can quickly find/update count.
                         */
                        i = request_buffer->num_requests - 1;

                        h24x7hw = &get_cpu_var(hv_24x7_hw);
                        h24x7hw->events[i] = event;
                        put_cpu_var(h24x7hw);
                        /*
                         * Clear the event count so we can compute the _change_
                         * in the 24x7 raw counter value at the end of the txn.
                         *
                         * Note that we could alternatively read the 24x7 value
                         * now and save its value in event->hw.prev_count. But
                         * that would require issuing a hcall, which would then
                         * defeat the purpose of using the txn interface.
                         */
                        local64_set(&event->count, 0);
                }

                put_cpu_var(hv_24x7_reqb);
        } else {
                now = h_24x7_get_value(event);
                update_event_count(event, now);
        }
}

static void h_24x7_event_start(struct perf_event *event, int flags)
{
        if (flags & PERF_EF_RELOAD)
                local64_set(&event->hw.prev_count, h_24x7_get_value(event));
}

static void h_24x7_event_stop(struct perf_event *event, int flags)
{
        h_24x7_event_read(event);
}

static int h_24x7_event_add(struct perf_event *event, int flags)
{
        if (flags & PERF_EF_START)
                h_24x7_event_start(event, flags);

        return 0;
}

/*
 * 24x7 counters only support READ transactions. They are
 * always counting and dont need/support ADD transactions.
 * Cache the flags, but otherwise ignore transactions that
 * are not PERF_PMU_TXN_READ.
 */
static void h_24x7_event_start_txn(struct pmu *pmu, unsigned int flags)
{
        struct hv_24x7_request_buffer *request_buffer;
        struct hv_24x7_data_result_buffer *result_buffer;

        /* We should not be called if we are already in a txn */
        WARN_ON_ONCE(__this_cpu_read(hv_24x7_txn_flags));

        __this_cpu_write(hv_24x7_txn_flags, flags);
        if (flags & ~PERF_PMU_TXN_READ)
                return;

        request_buffer = (void *)get_cpu_var(hv_24x7_reqb);
        result_buffer = (void *)get_cpu_var(hv_24x7_resb);

        init_24x7_request(request_buffer, result_buffer);

        put_cpu_var(hv_24x7_resb);
        put_cpu_var(hv_24x7_reqb);
}

/*
 * Clean up transaction state.
 *
 * NOTE: Ignore state of request and result buffers for now.
 *       We will initialize them during the next read/txn.
 */
static void reset_txn(void)
{
        __this_cpu_write(hv_24x7_txn_flags, 0);
        __this_cpu_write(hv_24x7_txn_err, 0);
}

/*
 * 24x7 counters only support READ transactions. They are always counting
 * and dont need/support ADD transactions. Clear ->txn_flags but otherwise
 * ignore transactions that are not of type PERF_PMU_TXN_READ.
 *
 * For READ transactions, submit all pending 24x7 requests (i.e requests
 * that were queued by h_24x7_event_read()), to the hypervisor and update
 * the event counts.
 */
static int h_24x7_event_commit_txn(struct pmu *pmu)
{
        struct hv_24x7_request_buffer *request_buffer;
        struct hv_24x7_data_result_buffer *result_buffer;
        struct hv_24x7_result *res, *next_res;
        u64 count;
        int i, ret, txn_flags;
        struct hv_24x7_hw *h24x7hw;

        txn_flags = __this_cpu_read(hv_24x7_txn_flags);
        WARN_ON_ONCE(!txn_flags);

        ret = 0;
        if (txn_flags & ~PERF_PMU_TXN_READ)
                goto out;

        ret = __this_cpu_read(hv_24x7_txn_err);
        if (ret)
                goto out;

        request_buffer = (void *)get_cpu_var(hv_24x7_reqb);
        result_buffer = (void *)get_cpu_var(hv_24x7_resb);

        ret = make_24x7_request(request_buffer, result_buffer);
        if (ret)
                goto put_reqb;

        h24x7hw = &get_cpu_var(hv_24x7_hw);

        /* Go through results in the result buffer to update event counts. */
        for (i = 0, res = result_buffer->results;
             i < result_buffer->num_results; i++, res = next_res) {
                struct perf_event *event = h24x7hw->events[res->result_ix];

                ret = get_count_from_result(event, result_buffer, res, &count,
                                            &next_res);
                if (ret)
                        break;

                update_event_count(event, count);
        }

        put_cpu_var(hv_24x7_hw);

put_reqb:
        put_cpu_var(hv_24x7_resb);
        put_cpu_var(hv_24x7_reqb);
out:
        reset_txn();
        return ret;
}

/*
 * 24x7 counters only support READ transactions. They are always counting
 * and dont need/support ADD transactions. However, regardless of type
 * of transaction, all we need to do is cleanup, so we don't have to check
 * the type of transaction.
 */
static void h_24x7_event_cancel_txn(struct pmu *pmu)
{
        WARN_ON_ONCE(!__this_cpu_read(hv_24x7_txn_flags));
        reset_txn();
}

static struct pmu h_24x7_pmu = {
        .task_ctx_nr = perf_invalid_context,

        .name = "hv_24x7",
        .attr_groups = attr_groups,
        .event_init  = h_24x7_event_init,
        .add         = h_24x7_event_add,
        .del         = h_24x7_event_stop,
        .start       = h_24x7_event_start,
        .stop        = h_24x7_event_stop,
        .read        = h_24x7_event_read,
        .start_txn   = h_24x7_event_start_txn,
        .commit_txn  = h_24x7_event_commit_txn,
        .cancel_txn  = h_24x7_event_cancel_txn,
};

static int hv_24x7_init(void)
{
        int r;
        unsigned long hret;
        struct hv_perf_caps caps;

        if (!firmware_has_feature(FW_FEATURE_LPAR)) {
                pr_debug("not a virtualized system, not enabling\n");
                return -ENODEV;
        } else if (!cur_cpu_spec->oprofile_cpu_type)
                return -ENODEV;

        /* POWER8 only supports v1, while POWER9 only supports v2. */
        if (!strcmp(cur_cpu_spec->oprofile_cpu_type, "ppc64/power8"))
                interface_version = 1;
        else {
                interface_version = 2;

                /* SMT8 in POWER9 needs to aggregate result elements. */
                if (threads_per_core == 8)
                        aggregate_result_elements = true;
        }

        hret = hv_perf_caps_get(&caps);
        if (hret) {
                pr_debug("could not obtain capabilities, not enabling, rc=%ld\n",
                                hret);
                return -ENODEV;
        }

        hv_page_cache = kmem_cache_create("hv-page-4096", 4096, 4096, 0, NULL);
        if (!hv_page_cache)
                return -ENOMEM;

        /* sampling not supported */
        h_24x7_pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT;

        r = create_events_from_catalog(&event_group.attrs,
                                   &event_desc_group.attrs,
                                   &event_long_desc_group.attrs);

        if (r)
                return r;

        r = perf_pmu_register(&h_24x7_pmu, h_24x7_pmu.name, -1);
        if (r)
                return r;

        return 0;
}

device_initcall(hv_24x7_init);