linux-kernel - Re: [RESEND PATCH] perf/x86/intel: Fix unchecked MSR access error for Alder Lake N

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Message-ID: <YwOKyBL7lNmyaFqs@worktop.programming.kicks-ass.net>
Date:   Mon, 22 Aug 2022 15:55:20 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     acme@...hat.com, linux-kernel@...r.kernel.org,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com,
        Jianfeng Gao <jianfeng.gao@...el.com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>
Subject: Re: [RESEND PATCH] perf/x86/intel: Fix unchecked MSR access error
 for Alder Lake N

On Mon, Aug 22, 2022 at 09:24:57AM -0400, Liang, Kan wrote:
> I think the only issue should be the PMU name. The non-hybrid PMU name
> is "cpu". The hybrid PMU name is "cpu_$coretype". If we move the
> ALDERLAKE_N to the non-hybrid PMU, the PMU name will be changed from
> "cpu_atom" to "cpu". It will be different from the rest of
> {ALDER,RAPTOP}LAKE.
> 
> Also, I think we have to update the perf tool for the events because of
> the PMU name change.
> 
> But I guess it should be OK, since the ALDERLAKE_N was just added and we
> know its an Atom-only system.

cpu/caps/pmu_name should be 'Gracemont', which is exactly like all the
other !hybrid setups. Surely perf-tools already knows about this
pattern.

IOW, if you need to change perf-tools for this, someone did something
wrong somewhere.

(also, I just noticed, 'Tremont' is the *only* PMU that has a
capitalized name, perhaps we don't want Gracemont to follow but instead
fix tremont if that is still possible)