Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1775 insertions, 0 deletions

diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
new file mode 100644
index 000000000..7dda59923
--- /dev/null
+++ b/arch/powerpc/perf/hv-24x7.c
@@ -0,0 +1,1775 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hypervisor supplied "24x7" performance counter support
+ *
+ * Author: Cody P Schafer <cody@linux.vnet.ibm.com>
+ * Copyright 2014 IBM Corporation.
+ */
+
+#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 <asm/rtas.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 cpumask_t hv_24x7_cpumask;
+
+static bool domain_is_valid(unsigned int 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 int 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;
+	}
+}
+
+/*
+ * The Processor Module Information system parameter allows transferring
+ * of certain processor module information from the platform to the OS.
+ * Refer PAPR+ document to get parameter token value as '43'.
+ */
+
+#define PROCESSOR_MODULE_INFO   43
+
+static u32 phys_sockets;	/* Physical sockets */
+static u32 phys_chipspersocket;	/* Physical chips per socket*/
+static u32 phys_coresperchip; /* Physical cores per chip */
+
+/*
+ * read_24x7_sys_info()
+ * Retrieve the number of sockets and chips per socket and cores per
+ * chip details through the get-system-parameter rtas call.
+ */
+void read_24x7_sys_info(void)
+{
+	int call_status, len, ntypes;
+
+	spin_lock(&rtas_data_buf_lock);
+
+	/*
+	 * Making system parameter: chips and sockets and cores per chip
+	 * default to 1.
+	 */
+	phys_sockets = 1;
+	phys_chipspersocket = 1;
+	phys_coresperchip = 1;
+
+	call_status = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
+				NULL,
+				PROCESSOR_MODULE_INFO,
+				__pa(rtas_data_buf),
+				RTAS_DATA_BUF_SIZE);
+
+	if (call_status != 0) {
+		pr_err("Error calling get-system-parameter %d\n",
+		       call_status);
+	} else {
+		len = be16_to_cpup((__be16 *)&rtas_data_buf[0]);
+		if (len < 8)
+			goto out;
+
+		ntypes = be16_to_cpup((__be16 *)&rtas_data_buf[2]);
+
+		if (!ntypes)
+			goto out;
+
+		phys_sockets = be16_to_cpup((__be16 *)&rtas_data_buf[4]);
+		phys_chipspersocket = be16_to_cpup((__be16 *)&rtas_data_buf[6]);
+		phys_coresperchip = be16_to_cpup((__be16 *)&rtas_data_buf[8]);
+	}
+
+out:
+	spin_unlock(&rtas_data_buf_lock);
+}
+
+/* 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 int 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 int 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 const 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;
+
+static DEFINE_PER_CPU(int, hv_24x7_txn_flags);
+static DEFINE_PER_CPU(int, hv_24x7_txn_err);
+
+struct hv_24x7_hw {
+	struct perf_event *events[255];
+};
+
+static 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
+static DEFINE_PER_CPU(char, hv_24x7_reqb[H24x7_DATA_BUFFER_SIZE]) __aligned(4096);
+static 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 int 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 int nl = be16_to_cpu(ev->event_name_len);
+	__be16 *desc_len_ = (__be16 *)(ev->remainder + nl - 2);
+	unsigned int 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 int dl, ldl;
+	unsigned int 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 int 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 ssize_t cpumask_show(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return cpumap_print_to_pagebuf(true, buf, &hv_24x7_cpumask);
+}
+
+static ssize_t sockets_show(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", phys_sockets);
+}
+
+static ssize_t chipspersocket_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", phys_chipspersocket);
+}
+
+static ssize_t coresperchip_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", phys_coresperchip);
+}
+
+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 int ix,
+				       struct hv_24x7_event_data *event,
+				       unsigned int 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 int 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 int ct;
+	unsigned int 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 int d1,
+		       const void *v2, size_t s2, unsigned int 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 int 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 = rb_entry(*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 its 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;
+}
+
+/*
+ * Return true incase of invalid or dummy events with names like RESERVED*
+ */
+static bool ignore_event(const char *name)
+{
+	return strncmp(name, "RESERVED", 8) == 0;
+}
+
+#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 (ignore_event(name)) {
+			junk_events++;
+			continue;
+		}
+		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);
+		if (ignore_event(name))
+			continue;
+
+		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 DEVICE_ATTR_RO(sockets);
+static DEVICE_ATTR_RO(chipspersocket);
+static DEVICE_ATTR_RO(coresperchip);
+static DEVICE_ATTR_RO(cpumask);
+
+static struct bin_attribute *if_bin_attrs[] = {
+	&bin_attr_catalog,
+	NULL,
+};
+
+static struct attribute *cpumask_attrs[] = {
+	&dev_attr_cpumask.attr,
+	NULL,
+};
+
+static const struct attribute_group cpumask_attr_group = {
+	.attrs = cpumask_attrs,
+};
+
+static struct attribute *if_attrs[] = {
+	&dev_attr_catalog_len.attr,
+	&dev_attr_catalog_version.attr,
+	&dev_attr_domains.attr,
+	&dev_attr_sockets.attr,
+	&dev_attr_chipspersocket.attr,
+	&dev_attr_coresperchip.attr,
+	NULL,
+};
+
+static const 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,
+	&cpumask_attr_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 int 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;
+	}
+
+	/* 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  == 0 || 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);
+		}
+
+		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,
+	.capabilities = PERF_PMU_CAP_NO_EXCLUDE,
+};
+
+static int ppc_hv_24x7_cpu_online(unsigned int cpu)
+{
+	if (cpumask_empty(&hv_24x7_cpumask))
+		cpumask_set_cpu(cpu, &hv_24x7_cpumask);
+
+	return 0;
+}
+
+static int ppc_hv_24x7_cpu_offline(unsigned int cpu)
+{
+	int target;
+
+	/* Check if exiting cpu is used for collecting 24x7 events */
+	if (!cpumask_test_and_clear_cpu(cpu, &hv_24x7_cpumask))
+		return 0;
+
+	/* Find a new cpu to collect 24x7 events */
+	target = cpumask_last(cpu_active_mask);
+
+	if (target < 0 || target >= nr_cpu_ids) {
+		pr_err("hv_24x7: CPU hotplug init failed\n");
+		return -1;
+	}
+
+	/* Migrate 24x7 events to the new target */
+	cpumask_set_cpu(target, &hv_24x7_cpumask);
+	perf_pmu_migrate_context(&h_24x7_pmu, cpu, target);
+
+	return 0;
+}
+
+static int hv_24x7_cpu_hotplug_init(void)
+{
+	return cpuhp_setup_state(CPUHP_AP_PERF_POWERPC_HV_24x7_ONLINE,
+			  "perf/powerpc/hv_24x7:online",
+			  ppc_hv_24x7_cpu_online,
+			  ppc_hv_24x7_cpu_offline);
+}
+
+static int hv_24x7_init(void)
+{
+	int r;
+	unsigned long hret;
+	unsigned int pvr = mfspr(SPRN_PVR);
+	struct hv_perf_caps caps;
+
+	if (!firmware_has_feature(FW_FEATURE_LPAR)) {
+		pr_debug("not a virtualized system, not enabling\n");
+		return -ENODEV;
+	}
+
+	/* POWER8 only supports v1, while POWER9 only supports v2. */
+	if (PVR_VER(pvr) == PVR_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;
+
+	/* init cpuhotplug */
+	r = hv_24x7_cpu_hotplug_init();
+	if (r)
+		return r;
+
+	r = perf_pmu_register(&h_24x7_pmu, h_24x7_pmu.name, -1);
+	if (r)
+		return r;
+
+	read_24x7_sys_info();
+
+	return 0;
+}
+
+device_initcall(hv_24x7_init);