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Date: Tue, 5 Mar 2024 22:16:13 +0800
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Subject: Re: [PATCH] arch/s390/perf: Register cpumf_pmu with type =
 PERF_TYPE_RAW
To: Mark Rutland <mark.rutland@arm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>, Vasily Gorbik <gor@linux.ibm.com>,
 Alexander Gordeev <agordeev@linux.ibm.com>,
 Christian Borntraeger <borntraeger@linux.ibm.com>,
 Sven Schnelle <svens@linux.ibm.com>, linux-s390@vger.kernel.org,
 linux-kernel@vger.kernel.org
References: <20240304022701.7362-1-jialong.yang@shingroup.cn>
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 <ACE696AA8DB8D91B+458ebdd8-6951-4f72-a188-b21dc9863b90@shingroup.cn>
 <ZecStMBA4YgQaBEZ@FVFF77S0Q05N>
From: Jialong Yang <jialong.yang@shingroup.cn>
In-Reply-To: <ZecStMBA4YgQaBEZ@FVFF77S0Q05N>
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在 2024/3/5 20:40, Mark Rutland 写道:
> On Tue, Mar 05, 2024 at 09:43:16AM +0800, Yang Jialong 杨佳龙 wrote:
>> 在 2024/3/4 17:34, Mark Rutland 写道:
>>> On Mon, Mar 04, 2024 at 10:27:01AM +0800, JiaLong.Yang wrote:
>>>> The struct pmu cpumf_pmu has handled generic events. So it need some
>>>> flags to tell core this thing.
>>> It's not necessary to register as PERF_TYPE_RAW in order to handle raw events,
>>> and PERF_TYPE_RAW is not a flag.
>>>
>>> Have you encountered a functional problem, or was this found by inspection?
>> As you expected, I'm trying to confirm which one pmu has the capability to
>> handle generic events in registering pmus instead of test generic events in
>> each pmus when opening.
> If we want to do that, then we need a new flag on struct pmu to restrict which
> events we try to open on a PMU.
>
> If you want to do that, you need to Cc the perf maintainers and discuss that
> rather than point-hacking individual drivers.
>
>> We can confirm that before using. We have pay more in handling them when
>> opening.
>> So most driver developers use PERF_TYPE_RAW. x86 and arm use
>> PERF_PMU_CAP_EXTENDED_HW_TYPE. Others use struct pmu::task_ctx_nr =
>> perf_hw_context.
>> I think PERF_TYPE_RAW will be a easily accepted way. So ...
> No, this is a hack, and it doesn't solve the problem you describe above.
>
> If we want to remove the need for most PMUs to look at perf_event_attr::type,
> then we should have a new PERF_PMU_CAP_ flag on the PMU to say "this PMU
> supports generic events" (or separate flags for the generic RAW/HW/CACHE
> types), and update all relevant PMUs accordingly.
>
> Please do not try to overload pmu::type with additional semantics; it's messy
> enough as-is.

OK. Thanks for guiding.


>
> Mark.
>