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Date:   Tue, 5 Apr 2022 15:04:51 +0100
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To:     <alexandre.truong@arm.com>
From:   John Garry <john.garry@huawei.com>
Subject: perf tool: About "perf arm64: Inject missing frames when using 'perf
 record --call-graph=fp'"
CC:     <linux-perf-users@vger.kernel.org>,
        "jolsa@kernel.org >> Jiri Olsa" <jolsa@kernel.org>,
        <german.gomez@arm.com>, <james.clark@arm.com>,
        "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>
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Hi Alexandre,

I notice that with commit b9f6fbb3b2c2 ("perf arm64: Inject missing 
frames when using 'perf record --call-graph=fp'") that I get messages 
spewing the console when running perf record+report, as below:

john@ubuntu:~/linux$sudo tools/perf/perf record -ag fio null12.fio
john@ubuntu:~/linux$sudo tools/perf/perf report > report
unwind: can't read reg 29
unwind: can't read reg 29
unwind: can't read reg 29
unwind: can't read reg 29
...

Do you know the possible cause? I haven't checked...

Thanks,
john