perf tool: About "perf arm64: Inject missing frames when using 'perf record --call-graph=fp'"

[John Garry]

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