linux-kernel - Re: [PATCH v6 1/6] perf arm64: Allow version comparisons of CPU IDs

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Message-ID: <80846ab1-1257-bcca-cf43-1a314275762e@oracle.com>
Date:   Thu, 17 Aug 2023 10:51:11 +0100
From:   John Garry <john.g.garry@...cle.com>
To:     James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, irogers@...gle.com,
        renyu.zj@...ux.alibaba.com, acme@...nel.org
Cc:     Will Deacon <will@...nel.org>, Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Haixin Yu <yuhaixin.yhx@...ux.alibaba.com>,
        Nick Forrington <nick.forrington@....com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Eduard Zingerman <eddyz87@...il.com>,
        Sohom Datta <sohomdatta1@...il.com>,
        Rob Herring <robh@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 1/6] perf arm64: Allow version comparisons of CPU IDs

On 16/08/2023 12:47, James Clark wrote:
> Currently variant and revision fields are masked out of the MIDR so
> it's not possible to compare different versions of the same CPU.
> In a later commit a workaround will be removed just for N2 r0p3, so
> enable comparisons on version.
> 
> This has the side effect of changing the MIDR stored in the header of
> the perf.data file to no longer have masked version fields. It also
> affects the lookups in mapfile.csv, but as that currently only has
> zeroed version fields, it has no actual effect. The mapfile.csv
> documentation also states to zero the version fields, so unless this
> isn't done it will continue to have no effect.
> 
> There is an existing weak default strcmp_cpuid_str() function, and an
> x86 version. This adds another version for arm64.
> 
> Signed-off-by: James Clark<james.clark@....com>

Reviewed-by: John Garry <john.g.garry@...cle.com>