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

[kajoljain]

On 6/19/20 10:35 AM, Gautham R Shenoy wrote:
> On Thu, Jun 18, 2020 at 05:57:13PM +0530, Kajol Jain wrote:
>> 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 at linux.ibm.com>
>> ---
>>  .../sysfs-bus-event_source-devices-hv_24x7    |  6 ++++
>>  arch/powerpc/perf/hv-24x7.c                   | 31 ++++++++++++++++++-
>>  2 files changed, 36 insertions(+), 1 deletion(-)
>>
>> 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..281e7b367733 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 +43,12 @@ 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 at lists.ozlabs.org>
>> +Description:	read only
>> +		This sysfs file exposes cpumask.
> 
> Could you please describe this in little more detail as to what the
> cpumask is ?
> 
Hi Gautham,
       Sure I will update the detail.

>> +
>>  What:		/sys/bus/event_source/devices/hv_24x7/event_descs/<event-name>
>>  Date:		February 2014
>>  Contact:	Linux on PowerPC Developer List <linuxppc-dev at lists.ozlabs.org>
>> diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
>> index fdc4ae155d60..03d870a9fc36 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,
>>  };
>>
>> @@ -1727,8 +1749,15 @@ 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
>> +		 */
>> +		attr_groups[5] = &cpumask_attr_group;
> 
> Since this is only a one-time initialization, wouldn't it be safer to
> iterate through attr_groups[] and assin cpumask_attr_group to the
> first NULL location ?

Yes thats right. Will update that part.

Thanks,
Kajol Jain
> 
>> +	}
>>
>>  	r = perf_pmu_register(&h_24x7_pmu, h_24x7_pmu.name, -1);
>>  	if (r)
>> -- 
>> 2.18.2
>>