Re: [PATCH V2 1/2] powerpc/perf: Add support for caps under sysfs in powerpc

Ian Rogers
2022-05-19T04:42:59Z

On Wed, May 18, 2022 at 1:55 AM Athira Rajeev
<atrajeev@linux.vnet.ibm.com> wrote:
>
> Add caps support under "/sys/bus/event_source/devices/<pmu>/"
> for powerpc. This directory can be used to expose some of the
> specific features that powerpc PMU supports to the user.
> Example: pmu_name. The name of PMU registered will depend on
> platform, say power9 or power10 or it could be Generic Compat
> PMU.
>
> Currently the only way to know which is the registered
> PMU is from the dmesg logs. But clearing the dmesg will make it
> difficult to know exact PMU backend used. And even extracting
> from dmesg will be complicated, as we need to parse the dmesg
> logs and add filters for pmu name. Whereas by exposing it via
> caps will make it easy as we just need to directly read it from
> the sysfs.

For ARM and x86 in the perf tool this is normally done through a cpuid
like function, is there a reason to differ on Power?

Thanks,
Ian

> Add a caps directory to /sys/bus/event_source/devices/cpu/
> for power8, power9, power10 and generic compat PMU in respective
> PMU driver code. Update the pmu_name file under caps folder
> in core-book3s using "attr_update".
>
> The information exposed currently:
> - pmu_name : Underlying PMU name from the driver
>
> Example result with power9 pmu:
>
> # ls /sys/bus/event_source/devices/cpu/caps
> pmu_name
>
> # cat /sys/bus/event_source/devices/cpu/caps/pmu_name
> POWER9
>
> Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
> ---
> Changelog:
> v1 -> v2:
> Move the show function as generic in core-book3s
> and update show function using sysfs_emit and ppmu->name
> Added Documention for this ABI in patch 2.
> Notes: The caps directory is implemented in PMU for other
> architectures already. Reference commit for x86:
> commit b00233b53065 ("perf/x86: Export some PMU attributes in caps/ directory")
>
> arch/powerpc/perf/core-book3s.c | 31 ++++++++++++++++++++++++++
> arch/powerpc/perf/generic-compat-pmu.c | 10 +++++++++
> arch/powerpc/perf/power10-pmu.c | 10 +++++++++
> arch/powerpc/perf/power8-pmu.c | 10 +++++++++
> arch/powerpc/perf/power9-pmu.c | 10 +++++++++
> 5 files changed, 71 insertions(+)
>
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index b5b42cf0a703..a208f502a80b 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -2488,6 +2488,33 @@ static int power_pmu_prepare_cpu(unsigned int cpu)
> return 0;
> }
>
> +static ssize_t pmu_name_show(struct device *cdev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + if (ppmu)
> + return sysfs_emit(buf, "%s\n", ppmu->name);
> +
> + return 0;
> +}
> +
> +static DEVICE_ATTR_RO(pmu_name);
> +
> +static struct attribute *pmu_caps_attrs[] = {
> + &dev_attr_pmu_name.attr,
> + NULL
> +};
> +
> +static const struct attribute_group pmu_caps_group = {
> + .name = "caps",
> + .attrs = pmu_caps_attrs,
> +};
> +
> +static const struct attribute_group *pmu_caps_groups[] = {
> + &pmu_caps_group,
> + NULL,
> +};
> +
> int __init register_power_pmu(struct power_pmu *pmu)
> {
> if (ppmu)
> @@ -2498,6 +2525,10 @@ int __init register_power_pmu(struct power_pmu *pmu)
> pmu->name);
>
> power_pmu.attr_groups = ppmu->attr_groups;
> +
> + if (ppmu->flags & PPMU_ARCH_207S)
> + power_pmu.attr_update = pmu_caps_groups;
> +
> power_pmu.capabilities |= (ppmu->capabilities & PERF_PMU_CAP_EXTENDED_REGS);
>
> #ifdef MSR_HV
> diff --git a/arch/powerpc/perf/generic-compat-pmu.c b/arch/powerpc/perf/generic-compat-pmu.c
> index f3db88aee4dd..817c69863038 100644
> --- a/arch/powerpc/perf/generic-compat-pmu.c
> +++ b/arch/powerpc/perf/generic-compat-pmu.c
> @@ -151,9 +151,19 @@ static const struct attribute_group generic_compat_pmu_format_group = {
> .attrs = generic_compat_pmu_format_attr,
> };
>
> +static struct attribute *generic_compat_pmu_caps_attrs[] = {
> + NULL
> +};
> +
> +static struct attribute_group generic_compat_pmu_caps_group = {
> + .name = "caps",
> + .attrs = generic_compat_pmu_caps_attrs,
> +};
> +
> static const struct attribute_group *generic_compat_pmu_attr_groups[] = {
> &generic_compat_pmu_format_group,
> &generic_compat_pmu_events_group,
> + &generic_compat_pmu_caps_group,
> NULL,
> };
>
> diff --git a/arch/powerpc/perf/power10-pmu.c b/arch/powerpc/perf/power10-pmu.c
> index c6d51e7093cf..d1adcd9f52e2 100644
> --- a/arch/powerpc/perf/power10-pmu.c
> +++ b/arch/powerpc/perf/power10-pmu.c
> @@ -258,6 +258,15 @@ static const struct attribute_group power10_pmu_format_group = {
> .attrs = power10_pmu_format_attr,
> };
>
> +static struct attribute *power10_pmu_caps_attrs[] = {
> + NULL
> +};
> +
> +static struct attribute_group power10_pmu_caps_group = {
> + .name = "caps",
> + .attrs = power10_pmu_caps_attrs,
> +};
> +
> static const struct attribute_group *power10_pmu_attr_groups_dd1[] = {
> &power10_pmu_format_group,
> &power10_pmu_events_group_dd1,
> @@ -267,6 +276,7 @@ static const struct attribute_group *power10_pmu_attr_groups_dd1[] = {
> static const struct attribute_group *power10_pmu_attr_groups[] = {
> &power10_pmu_format_group,
> &power10_pmu_events_group,
> + &power10_pmu_caps_group,
> NULL,
> };
>
> diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c
> index e37b1e714d2b..2518f5375d4a 100644
> --- a/arch/powerpc/perf/power8-pmu.c
> +++ b/arch/powerpc/perf/power8-pmu.c
> @@ -187,9 +187,19 @@ static const struct attribute_group power8_pmu_events_group = {
> .attrs = power8_events_attr,
> };
>
> +static struct attribute *power8_pmu_caps_attrs[] = {
> + NULL
> +};
> +
> +static struct attribute_group power8_pmu_caps_group = {
> + .name = "caps",
> + .attrs = power8_pmu_caps_attrs,
> +};
> +
> static const struct attribute_group *power8_pmu_attr_groups[] = {
> &isa207_pmu_format_group,
> &power8_pmu_events_group,
> + &power8_pmu_caps_group,
> NULL,
> };
>
> diff --git a/arch/powerpc/perf/power9-pmu.c b/arch/powerpc/perf/power9-pmu.c
> index c393e837648e..5c654ce1a417 100644
> --- a/arch/powerpc/perf/power9-pmu.c
> +++ b/arch/powerpc/perf/power9-pmu.c
> @@ -258,9 +258,19 @@ static const struct attribute_group power9_pmu_format_group = {
> .attrs = power9_pmu_format_attr,
> };
>
> +static struct attribute *power9_pmu_caps_attrs[] = {
> + NULL
> +};
> +
> +static struct attribute_group power9_pmu_caps_group = {
> + .name = "caps",
> + .attrs = power9_pmu_caps_attrs,
> +};
> +
> static const struct attribute_group *power9_pmu_attr_groups[] = {
> &power9_pmu_format_group,
> &power9_pmu_events_group,
> + &power9_pmu_caps_group,
> NULL,
> };
>
> --
> 2.31.1
>