linux-kernel - Re: [PATCH 1/2] perf/x86/rapl: Add support for Intel Meteor Lake

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Message-ID: <Y7f6RhF8FuK9R399@zn.tnic>
Date:   Fri, 6 Jan 2023 11:39:02 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Zhang, Rui" <rui.zhang@...el.com>
Cc:     "Hansen, Dave" <dave.hansen@...el.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "kan.liang@...ux.intel.com" <kan.liang@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] perf/x86/rapl: Add support for Intel Meteor Lake

On Fri, Jan 06, 2023 at 06:05:41AM +0000, Zhang, Rui wrote:
> But I still have a question.
> Take RAPL feature for example, the feature is not architectural,
> although 80% of the platforms may follow the same behavior, but there
> are still cases that behave differently. And so far, there are 8
> different behaviors based on different models.
> 
> In this case, can we have several different flags for the RAPL feature
> and make the RAPL driver probe on different RAPL flags? Or else, a
> model list is still needed.

Well, you asked about detecting CPUs supporting RAPL.

Now you're asking about different RAPL "subfunctionality" or whatever.

You could do the synthetic flag for feature detection because apparently giving
it a CPUID flag is soo expensive (/sarcastic eyeroll) and then you can pick
apart subfeatures in the RAPL code and do flags there, away from the x86 arch
code because no one should see that.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette