Message-ID: <c5f1c3c2-6de3-a40d-9cf0-c1c7638acfc3@amd.com>
Date:   Fri, 3 Mar 2023 11:24:08 +0530
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Subject: Re: [PATCH 1/2] perf/ibs: Fix interface via core pmu events
Content-Language: en-US
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     peterz@infradead.org, eranian@google.com, acme@kernel.org,
        mark.rutland@arm.com, jolsa@kernel.org, irogers@google.com,
        bp@alien8.de, x86@kernel.org, linux-perf-users@vger.kernel.org,
        linux-kernel@vger.kernel.org, sandipan.das@amd.com,
        ananth.narayan@amd.com, santosh.shukla@amd.com,
        Ravi Bangoria <ravi.bangoria@amd.com>
References: <20230302092109.367-1-ravi.bangoria@amd.com>
 <20230302092109.367-2-ravi.bangoria@amd.com>
 <CAM9d7cjEvjcYwjA+HfsDHKDX8FGZCECTZ8vDMPHBUSqfQSCOfA@mail.gmail.com>
From:   Ravi Bangoria <ravi.bangoria@amd.com>
In-Reply-To: <CAM9d7cjEvjcYwjA+HfsDHKDX8FGZCECTZ8vDMPHBUSqfQSCOfA@mail.gmail.com>
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Hi Namhyung,

>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index a5a51dfdd622..c3f59d937280 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -11633,9 +11633,13 @@ static struct pmu *perf_init_event(struct perf_event *event)
>>                         goto fail;
>>
>>                 ret = perf_try_init_event(pmu, event);
>> -               if (ret == -ENOENT && event->attr.type != type && !extended_type) {
>> -                       type = event->attr.type;
>> -                       goto again;
>> +               if (ret == -ENOENT) {
>> +                       if (event->attr.type != type && !extended_type) {
>> +                               type = event->attr.type;
>> +                               goto again;
>> +                       }
>> +                       if (pmu->capabilities & PERF_PMU_CAP_FORWARD_EVENT)
>> +                               goto try_all;
> 
> Wouldn't it be better to use a different error code to indicate
> it's about precise_ip (or forwarding in general)?  Otherwise
> other invalid config might cause the forwarding unnecessarily..

That would make things easier and we might not need this new capability.
Most appropriate error codes seems ENOENT, EOPNOTSUPP and EINVAL but all
are already used for other purposes. Any other suggestions?

Thanks,
Ravi