On Fri, Jun 26, 2020 at 03:58:24PM +0530, Kajol Jain wrote:
> Patch here adds a cpumask attr to hv_24x7 pmu along with ABI documentation.
>
> Primary use to expose the cpumask is for the perf tool which has the
> capability to parse the driver sysfs folder and understand the
> cpumask file. Having cpumask file will reduce the number of perf command
> line parameters (will avoid "-C" option in the perf tool
> command line). It can also notify the user which is
> the current cpu used to retrieve the counter data.
>
> command:# cat /sys/devices/hv_24x7/cpumask
> 0
>
> Signed-off-by: Kajol Jain <kj...@linux.ibm.com>
This patch looks good to me.
Reviewed-by: Gautham R. Shenoy <e...@linux.vnet.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 retrieve 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
>
