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

Ravi Bangoria
2022-04-26T11:41:14Z

On 26-Apr-22 3:27 PM, Robert Richter wrote:
> 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.

Same as previous patch, except defining size of the array, it won't
be used anywhere else.

>
>>
>> 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;

Sure.

>
>>
>> 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.

I think we can just remove this line. perf_ibs points to either perf_ibs_fetch
or perf_ibs_op, both of which are global variables and would be preinitialized
with 0s.

>
>> 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.

Yup.

Thanks for the review,
Ravi