Re: [PATCH 2/6] perf/amd/ibs: Advertise zen4_ibs_extensions as pmu capability attribute

Robert Richter
2022-04-26T10:23:28Z

On 25.04.22 10:13:19, Ravi Bangoria wrote:
> PMU driver can advertise certain feature via capability attribute('caps'
> sysfs directory) which can be consumed by userspace tools like perf. Add
> zen4_ibs_extensions capability attribute for IBS pmus. This attribute
> will be enabled when CPUID_Fn8000001B_EAX[11] is set.
>
> Without patch:
>
> $ ls /sys/bus/event_source/devices/ibs_op/caps
> ls: cannot access '/sys/.../ibs_op/caps': No such file or directory
>
> With patch:
>
> $ ls /sys/bus/event_source/devices/ibs_op/caps
> zen4_ibs_extensions
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
> ---
> arch/x86/events/amd/ibs.c | 34 ++++++++++++++++++++++++++++------
> 1 file changed, 28 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
> index a5303d62060c..54e12bd7843e 100644
> --- a/arch/x86/events/amd/ibs.c
> +++ b/arch/x86/events/amd/ibs.c
> @@ -95,8 +95,10 @@ struct perf_ibs {
> struct cpu_perf_ibs __percpu *pcpu;
>
> struct attribute **format_attrs;
> + struct attribute **caps_attrs;
> struct attribute_group format_group;
> - const struct attribute_group *attr_groups[2];
> + struct attribute_group caps_group;
> + const struct attribute_group *attr_groups[3];

Also add a macro for max groups.

>
> u64 (*get_count)(u64 config);
> };
> @@ -522,10 +524,13 @@ PMU_FORMAT_ATTR(rand_en, "config:57");
> PMU_FORMAT_ATTR(cnt_ctl, "config:19");
> PMU_EVENT_ATTR_STRING(l3missonly, fetch_l3missonly, "config:59");
> PMU_EVENT_ATTR_STRING(l3missonly, op_l3missonly, "config:16");
> +PMU_EVENT_ATTR_STRING(zen4_ibs_extensions, zen4_ibs_extensions, "1");
>
> /* size = nr attrs plus NULL at the end */
> static struct attribute *ibs_fetch_format_attrs[3];
> static struct attribute *ibs_op_format_attrs[3];
> +static struct attribute *ibs_fetch_caps_attrs[2];
> +static struct attribute *ibs_op_caps_attrs[2];
>
> static struct perf_ibs perf_ibs_fetch = {
> .pmu = {
> @@ -548,6 +553,7 @@ static struct perf_ibs perf_ibs_fetch = {
> .offset_mask = { MSR_AMD64_IBSFETCH_REG_MASK },
> .offset_max = MSR_AMD64_IBSFETCH_REG_COUNT,
> .format_attrs = ibs_fetch_format_attrs,
> + .caps_attrs = ibs_fetch_caps_attrs,
>
> .get_count = get_ibs_fetch_count,
> };
> @@ -574,6 +580,7 @@ static struct perf_ibs perf_ibs_op = {
> .offset_mask = { MSR_AMD64_IBSOP_REG_MASK },
> .offset_max = MSR_AMD64_IBSOP_REG_COUNT,
> .format_attrs = ibs_op_format_attrs,
> + .caps_attrs = ibs_op_caps_attrs,
>
> .get_count = get_ibs_op_count,
> };
> @@ -728,6 +735,7 @@ static __init int perf_ibs_pmu_init(struct perf_ibs *perf_ibs, char *name)
> {
> struct cpu_perf_ibs __percpu *pcpu;
> int ret;
> + int i = 0;

'group'? Use a pointer to iterate over groups here same as for attrs?

struct attribute_group **group = &perf_ibs->attr_groups;

>
> pcpu = alloc_percpu(struct cpu_perf_ibs);
> if (!pcpu)
> @@ -736,16 +744,26 @@ static __init int perf_ibs_pmu_init(struct perf_ibs *perf_ibs, char *name)
> perf_ibs->pcpu = pcpu;
>
> /* register attributes */
> + memset(&perf_ibs->attr_groups, 0, sizeof(perf_ibs->attr_groups));

With a termination below this could be dropped.

> if (perf_ibs->format_attrs[0]) {
> memset(&perf_ibs->format_group, 0, sizeof(perf_ibs->format_group));
> - perf_ibs->format_group.name = "format";
> - perf_ibs->format_group.attrs = perf_ibs->format_attrs;
> + perf_ibs->format_group.name = "format";
> + perf_ibs->format_group.attrs = perf_ibs->format_attrs;
>
> - memset(&perf_ibs->attr_groups, 0, sizeof(perf_ibs->attr_groups));
> - perf_ibs->attr_groups[0] = &perf_ibs->format_group;
> - perf_ibs->pmu.attr_groups = perf_ibs->attr_groups;
> + perf_ibs->attr_groups[i++] = &perf_ibs->format_group;

So this could be:

*groups++ = &perf_ibs->format_group

> }
>
> + if (perf_ibs->caps_attrs[0]) {
> + memset(&perf_ibs->caps_group, 0, sizeof(perf_ibs->caps_group));
> + perf_ibs->caps_group.name = "caps";
> + perf_ibs->caps_group.attrs = perf_ibs->caps_attrs;
> +
> + perf_ibs->attr_groups[i++] = &perf_ibs->caps_group;

Similar here.

> + }

Add a terminating NULL pointer for groups here.

> +
> + if (i)

if (perf_ibs->attr_groups[0])
...

> + perf_ibs->pmu.attr_groups = perf_ibs->attr_groups;
> +
> ret = perf_pmu_register(&perf_ibs->pmu, name, -1);
> if (ret) {
> perf_ibs->pcpu = NULL;
> @@ -758,6 +776,7 @@ static __init int perf_ibs_pmu_init(struct perf_ibs *perf_ibs, char *name)
> static __init void perf_ibs_fetch_prepare(void)
> {
> struct attribute **format_attrs = perf_ibs_fetch.format_attrs;
> + struct attribute **caps_attr = perf_ibs_fetch.caps_attrs;

Now I see why it was renamed, ok.

>
> /*
> * Some chips fail to reset the fetch count when it is written; instead
> @@ -773,6 +792,7 @@ static __init void perf_ibs_fetch_prepare(void)
> if (ibs_caps & IBS_CAPS_ZEN4IBSEXTENSIONS) {
> perf_ibs_fetch.config_mask |= IBS_FETCH_L3MISSONLY;
> *format_attrs++ = &fetch_l3missonly.attr.attr;
> + *caps_attr++ = &zen4_ibs_extensions.attr.attr;
> }
>
> perf_ibs_pmu_init(&perf_ibs_fetch, "ibs_fetch");
> @@ -781,6 +801,7 @@ static __init void perf_ibs_fetch_prepare(void)
> static __init void perf_ibs_op_prepare(void)
> {
> struct attribute **format_attrs = perf_ibs_op.format_attrs;
> + struct attribute **caps_attr = perf_ibs_op.caps_attrs;
>
> if (ibs_caps & IBS_CAPS_OPCNT) {
> perf_ibs_op.config_mask |= IBS_OP_CNT_CTL;
> @@ -796,6 +817,7 @@ static __init void perf_ibs_op_prepare(void)
> if (ibs_caps & IBS_CAPS_ZEN4IBSEXTENSIONS) {
> perf_ibs_op.config_mask |= IBS_OP_L3MISSONLY;
> *format_attrs++ = &op_l3missonly.attr.attr;
> + *caps_attr++ = &zen4_ibs_extensions.attr.attr;
> }

Also add a termination for caps here.

-Robert

>
> perf_ibs_pmu_init(&perf_ibs_op, "ibs_op");
> --
> 2.27.0
>