[PATCH v2 2/2] powerpc/hv-24x7: Add sysfs files inside hv-24x7 device to show cpumask

[Kajol Jain <kjain@linux.ibm.com>]

Patch here adds a cpumask attr to hv_24x7 pmu along with ABI documentation.

command:# cat /sys/devices/hv_24x7/cpumask
0

Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
---
 .../sysfs-bus-event_source-devices-hv_24x7    |  7 ++++
 arch/powerpc/perf/hv-24x7.c                   | 36 +++++++++++++++++--
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7 b/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7
index e8698afcd952..f9dd3755b049 100644
--- a/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7
+++ b/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7
@@ -43,6 +43,13 @@ Description:	read only
 		This sysfs interface exposes the number of cores per chip
 		present in the system.
 
+What:		/sys/devices/hv_24x7/cpumask
+Date:		June 2020
+Contact:	Linux on PowerPC Developer List <linuxppc-dev@lists.ozlabs.org>
+Description:	read only
+		This sysfs file exposes the cpumask which is designated to make
+		HCALLs to retrive hv-24x7 pmu event counter data.
+
 What:		/sys/bus/event_source/devices/hv_24x7/event_descs/<event-name>
 Date:		February 2014
 Contact:	Linux on PowerPC Developer List <linuxppc-dev@lists.ozlabs.org>
diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
index ce4739e2b407..3c699612d29f 100644
--- a/arch/powerpc/perf/hv-24x7.c
+++ b/arch/powerpc/perf/hv-24x7.c
@@ -448,6 +448,12 @@ static ssize_t device_show_string(struct device *dev,
 	return sprintf(buf, "%s\n", (char *)d->var);
 }
 
+static ssize_t cpumask_get_attr(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)
 {
@@ -1116,6 +1122,17 @@ static DEVICE_ATTR_RO(sockets);
 static DEVICE_ATTR_RO(chipspersocket);
 static DEVICE_ATTR_RO(coresperchip);
 
+static DEVICE_ATTR(cpumask, S_IRUGO, cpumask_get_attr, NULL);
+
+static struct attribute *cpumask_attrs[] = {
+	&dev_attr_cpumask.attr,
+	NULL,
+};
+
+static struct attribute_group cpumask_attr_group = {
+	.attrs = cpumask_attrs,
+};
+
 static struct bin_attribute *if_bin_attrs[] = {
 	&bin_attr_catalog,
 	NULL,
@@ -1143,6 +1160,11 @@ static const struct attribute_group *attr_groups[] = {
 	&event_desc_group,
 	&event_long_desc_group,
 	&if_group,
+	/*
+	 * This NULL is a placeholder for the cpumask attr which will update
+	 * onlyif cpuhotplug registration is successful
+	 */
+	NULL,
 	NULL,
 };
 
@@ -1683,7 +1705,7 @@ static int hv_24x7_cpu_hotplug_init(void)
 
 static int hv_24x7_init(void)
 {
-	int r;
+	int r, i = -1;
 	unsigned long hret;
 	struct hv_perf_caps caps;
 
@@ -1727,8 +1749,18 @@ static int hv_24x7_init(void)
 
 	/* init cpuhotplug */
 	r = hv_24x7_cpu_hotplug_init();
-	if (r)
+	if (r) {
 		pr_err("hv_24x7: CPU hotplug init failed\n");
+	} else {
+		/*
+		 * Cpu hotplug init is successful, add the
+		 * cpumask file as part of pmu attr group and
+		 * assign it to very first NULL location.
+		 */
+		while (attr_groups[++i])
+			/* nothing */;
+		attr_groups[i] = &cpumask_attr_group;
+	}
 
 	r = perf_pmu_register(&h_24x7_pmu, h_24x7_pmu.name, -1);
 	if (r)
-- 
2.18.2