[PATCH 1/5] powerpc/htm: Add interface to expose HTM trace data via perf

[Athira Rajeev <atrajeev@linux.ibm.com>]

H_HTM (Hardware Trace Macro) hypervisor call is an HCALL to export data
from Hardware Trace Macro (HTM) function. Add support for setup,
configuration and control of HTM function via PMU.

H_HTM is used as an interface for executing Hardware Trace Macro (HTM)
functions, including setup, configuration, control and dumping of the
HTM data. HTM operations can be controlled using the H_HTM hcall. The
hcall can be invoked for any core/chip of the system from within a
partition itself.

To use this, expose event as part of "htm" PMU. The event code or config
is 28 bit value, where user can specify below required fields:

event: "config:0-27"
htm_type: "config:0-3"
nodeindex: "config:4-11"
nodalchipindex: "config:12-19"
coreindexonchip: "config:20-27"

1) nodeindex, nodalchipindex, coreindexonchip: this specifies
   which partition to configure the HTM for.
2) htmtype: specifies the type of HTM.

In htm_event_add: configure and start the tracing using htm_hcall_wrapper
which is defined in plpar_wrappers.h header file
In htm_event_del: stop and deconfigure the tracing using
htm_hcall_wrapper

With the changes:

 # ls /sys/bus/event_source/devices/ |grep htm
 htm

 # ls /sys/bus/event_source/devices/htm/
 events  format  perf_event_mux_interval_ms  power  subsystem  type  uevent

Signed-off-by: Athira Rajeev <atrajeev@linux.ibm.com>
---
 arch/powerpc/perf/Makefile   |   2 +-
 arch/powerpc/perf/htm-perf.c | 307 +++++++++++++++++++++++++++++++++++
 2 files changed, 308 insertions(+), 1 deletion(-)
 create mode 100644 arch/powerpc/perf/htm-perf.c

diff --git a/arch/powerpc/perf/Makefile b/arch/powerpc/perf/Makefile
index 78dd7e25219e..26ef30c0693c 100644
--- a/arch/powerpc/perf/Makefile
+++ b/arch/powerpc/perf/Makefile
@@ -14,7 +14,7 @@ obj-$(CONFIG_PPC_POWERNV)	+= imc-pmu.o
 obj-$(CONFIG_FSL_EMB_PERF_EVENT) += core-fsl-emb.o
 obj-$(CONFIG_FSL_EMB_PERF_EVENT_E500) += e500-pmu.o e6500-pmu.o
 
-obj-$(CONFIG_HV_PERF_CTRS) += hv-24x7.o hv-gpci.o hv-common.o vpa-dtl.o
+obj-$(CONFIG_HV_PERF_CTRS) += hv-24x7.o hv-gpci.o hv-common.o vpa-dtl.o htm-perf.o
 
 obj-$(CONFIG_VPA_PMU) += vpa-pmu.o
 
diff --git a/arch/powerpc/perf/htm-perf.c b/arch/powerpc/perf/htm-perf.c
new file mode 100644
index 000000000000..e22a7fdce2f5
--- /dev/null
+++ b/arch/powerpc/perf/htm-perf.c
@@ -0,0 +1,307 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Perf interface to expose HTM Trace data.
+ *
+ * Copyright (C) 2025 Athira Rajeev, IBM Corporation
+ */
+
+#define pr_fmt(fmt) "htm: " fmt
+
+#include <asm/dtl.h>
+#include <linux/perf_event.h>
+#include <asm/plpar_wrappers.h>
+#include <linux/vmalloc.h>
+
+extern void perf_event_wakeup(struct perf_event *event);
+#define EVENT(_name, _code)     enum{_name = _code}
+
+/*
+ * H_HTM (Hardware Trace Macro) hypervisor call is an HCALL to export
+ * data from Hardware Trace Macro (HTM) function.
+ *
+ * Event codes based on HTM type.
+ */
+EVENT(HTM_CORE,         0x2);
+EVENT(HTM_NEST,	        0x1);
+
+GENERIC_EVENT_ATTR(htm_core, HTM_CORE);
+GENERIC_EVENT_ATTR(htm_nest, HTM_NEST);
+
+PMU_FORMAT_ATTR(event, "config:0-27");
+PMU_FORMAT_ATTR(htm_type, "config:0-3");
+PMU_FORMAT_ATTR(nodeindex, "config:4-11");
+PMU_FORMAT_ATTR(nodalchipindex, "config:12-19");
+PMU_FORMAT_ATTR(coreindexonchip, "config:20-27");
+
+static struct attribute *events_attr[] = {
+	GENERIC_EVENT_PTR(HTM_NEST),
+	GENERIC_EVENT_PTR(HTM_CORE),
+	NULL
+};
+
+static struct attribute_group event_group = {
+	.name = "events",
+	.attrs = events_attr,
+};
+
+static struct attribute *format_attrs[] = {
+	&format_attr_event.attr,
+	&format_attr_htm_type.attr,
+	&format_attr_nodeindex.attr,
+	&format_attr_nodalchipindex.attr,
+	&format_attr_coreindexonchip.attr,
+	NULL,
+};
+
+static const struct attribute_group format_group = {
+	.name = "format",
+	.attrs = format_attrs,
+};
+
+static const struct attribute_group *attr_groups[] = {
+	&format_group,
+	&event_group,
+	NULL,
+};
+
+static u64 htmflags = H_HTM_FLAGS_NOWRAP;
+
+/*
+ * Check the return code for H_HTM hcall.
+ * Return non-zero value (1) if either H_PARTIAL or H_SUCCESS
+ * is returned. For other return codes:
+ * Return zero if H_NOT_AVAILABLE.
+ * Return -EBUSY if hcall return busy.
+ * Return -EINVAL if any parameter or operation is not valid.
+ * Return -EPERM if HTM Virtualization Engine Technology code
+ * is not applied.
+ * Return -EIO if the HTM state is not valid.
+ */
+static ssize_t htm_return_check(int rc)
+{
+	switch (rc) {
+	case H_SUCCESS:
+		break;
+	/* H_PARTIAL for the case where all available data can't be
+	 * returned due to buffer size constraint.
+	 */
+	case H_PARTIAL:
+		break;
+	/* H_NOT_AVAILABLE indicates reading from an offset outside the range,
+	 * i.e. past end of file.
+	 */
+	case H_NOT_AVAILABLE:
+		return 0;
+	case H_BUSY:
+	case H_LONG_BUSY_ORDER_1_MSEC:
+	case H_LONG_BUSY_ORDER_10_MSEC:
+	case H_LONG_BUSY_ORDER_100_MSEC:
+	case H_LONG_BUSY_ORDER_1_SEC:
+	case H_LONG_BUSY_ORDER_10_SEC:
+	case H_LONG_BUSY_ORDER_100_SEC:
+		return -EBUSY;
+	case H_PARAMETER:
+		goto out;
+	case H_P2:
+		goto out;
+	case H_P3:
+		goto out;
+	case H_P4:
+		goto out;
+	case H_P5:
+		goto out;
+	case H_P6:
+		return -EINVAL;
+	case H_STATE:
+		return -EIO;
+	case H_AUTHORITY:
+		return -EPERM;
+	}
+
+	/*
+	 * Return 1 for H_SUCCESS/H_PARTIAL
+	 */
+	return 1;
+out:
+	return -EINVAL;
+}
+
+static int htm_event_init(struct perf_event *event)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	u64 config = event->attr.config;
+	u32 htmtype;
+
+	if (event->attr.inherit)
+		return -EOPNOTSUPP;
+
+	/* test the event attr type for PMU enumeration */
+	if (event->attr.type != event->pmu->type)
+		return -ENOENT;
+
+	if (!perfmon_capable())
+		return -EACCES;
+
+	/* Return if this is a counting event */
+	if (!is_sampling_event(event))
+		return -EOPNOTSUPP;
+
+	/* no branch sampling */
+	if (has_branch_stack(event))
+		return -EOPNOTSUPP;
+
+	htmtype = config & 0xf;
+	/* Invalid eventcode */
+	switch (htmtype) {
+	case HTM_CORE:
+	case HTM_NEST:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	htmflags = H_HTM_FLAGS_NOWRAP;
+
+	if (event->attr.freq) {
+		hwc->sample_period = event->attr.sample_period;
+		local64_set(&hwc->period_left, hwc->sample_period);
+		hwc->last_period = hwc->sample_period;
+		event->attr.freq = 0;
+	}
+
+	return 0;
+}
+
+static int htm_event_add(struct perf_event *event, int flags)
+{
+	int rc, ret;
+	unsigned long param1 = -1, param2 = -1;
+	int retries = 0;
+	u64 config = event->attr.config;
+	u32 htmtype, nodeindex, nodalchipindex, coreindexonchip;
+
+	/*
+	 * Invoke H_HTM call with:
+	 * operation as htm configure (H_HTM_OP_CONFIGURE)
+	 * last three values are unused, hence set to zero
+	 */
+	htmtype = config & 0xf;
+	nodeindex = (config >> 4) & 0xff;
+	nodalchipindex = (config >> 12) & 0xff;
+	coreindexonchip = (config >> 20) & 0xff;
+	do {
+		rc = htm_hcall_wrapper(htmflags, nodeindex, nodalchipindex, coreindexonchip,
+			htmtype, H_HTM_OP_CONFIGURE, param1, param2, 0);
+		ret = htm_return_check(rc);
+	} while (ret <= 0 && ++retries < 100);
+	if (ret <= 0)
+		return -1;
+
+	/* Reset retries */
+	retries = 0;
+
+	/*
+	 * Invoke H_HTM call with:
+	 * operation as htm  start (H_HTM_OP_START)
+	 * last three values are unused, hence set to zero
+	 */
+	do {
+		rc = htm_hcall_wrapper(htmflags, nodeindex, nodalchipindex, coreindexonchip,
+				htmtype, H_HTM_OP_START, 0, 0, 0);
+		ret = htm_return_check(rc);
+	} while (ret == -EBUSY && ++retries < 100);
+
+	if (htm_return_check(rc) <= 0)
+		return -1;
+
+	return 0;
+}
+
+static void htm_event_del(struct perf_event *event, int flags)
+{
+	long rc;
+	int ret;
+	int retries = 0;
+	u64 config = event->attr.config;
+	u32 htmtype, nodeindex, nodalchipindex, coreindexonchip;
+
+	/*
+	 * Invoke H_HTM call with:
+	 * operation as htm  stop (H_HTM_OP_STOP)
+	 * last three values are unused, hence set to zero
+	 */
+	htmtype = config & 0xf;
+	nodeindex = (config >> 4) & 0xff;
+	nodalchipindex = (config >> 12) & 0xff;
+	coreindexonchip = (config >> 20) & 0xff;
+	do {
+		rc = htm_hcall_wrapper(htmflags, nodeindex, nodalchipindex, coreindexonchip,
+				htmtype, H_HTM_OP_STOP, 0, 0, 0);
+		ret = htm_return_check(rc);
+	} while (ret == -EBUSY && ++retries < 100);
+
+	/* Reset retries */
+	retries = 0;
+
+	/*
+	 * Invoke H_HTM call with:
+	 * operation as htm configure (H_HTM_OP_DECONFIGURE)
+	 * last three values are unused, hence set to zero
+	 */
+	do {
+		rc = htm_hcall_wrapper(htmflags, nodeindex, nodalchipindex, coreindexonchip,
+			htmtype, H_HTM_OP_DECONFIGURE, 0, 0, 0);
+		ret = htm_return_check(rc);
+	} while (ret <= 0 && ++retries < 100);
+}
+
+/*
+ * This function definition is empty as htm_dump_sample_data
+ * is used to parse and dump the HTM trace data,
+ * to perf data.
+ */
+static void htm_event_read(struct perf_event *event)
+{
+	return;
+}
+
+static void htm_event_start(struct perf_event *event, int flags)
+{
+}
+
+static void htm_event_stop(struct perf_event *event, int flags)
+{
+}
+
+static struct pmu htm_pmu = {
+	.task_ctx_nr = perf_invalid_context,
+
+	.name = "htm",
+	.attr_groups = attr_groups,
+	.event_init  = htm_event_init,
+	.add         = htm_event_add,
+	.del         = htm_event_del,
+	.read        = htm_event_read,
+	.start	     = htm_event_start,
+	.stop	     = htm_event_stop,
+	.capabilities = PERF_PMU_CAP_NO_EXCLUDE | PERF_PMU_CAP_EXCLUSIVE,
+};
+
+static int htm_init(void)
+{
+	int r;
+
+	/* This driver is intended only for L1 host. */
+	if (is_kvm_guest()) {
+		pr_debug("Only supported for L1 host system\n");
+		return -ENODEV;
+	}
+
+	r = perf_pmu_register(&htm_pmu, htm_pmu.name, -1);
+	if (r)
+		return r;
+
+	return 0;
+}
+
+device_initcall(htm_init);
-- 
2.52.0