Re: [PATCH v5 2/2] powerpc/hv-24x7: Add sysfs files inside hv-24x7 device to show cpumask

[Madhavan Srinivasan <maddy@linux.ibm.com>]

On 7/9/20 10:48 AM, 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/interface/cpumask
> 0


Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com>

> Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
> ---
>   .../ABI/testing/sysfs-bus-event_source-devices-hv_24x7    | 7 +++++++
>   arch/powerpc/perf/hv-24x7.c                               | 8 ++++++++
>   2 files changed, 15 insertions(+)
>
> 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..f7e32f218f73 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/interface/cpumask
> +Date:		July 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 93b4700dcf8c..acc34148ad09 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_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)
>   {
> @@ -1115,6 +1121,7 @@ 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,
> @@ -1128,6 +1135,7 @@ static struct attribute *if_attrs[] = {
>   	&dev_attr_sockets.attr,
>   	&dev_attr_chipspersocket.attr,
>   	&dev_attr_coresperchip.attr,
> +	&dev_attr_cpumask.attr,
>   	NULL,
>   };
>