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Precise cycles event is forwarded to ibs_op// pmu >>>> on AMD. However, IBS has hw issue on certain Zen2 processors where >>>> it might raise NMI without sample_valid bit set, which causes Unknown >>>> NMI warnings. (Erratum #1215: IBS (Instruction Based Sampling) Counter >>>> Valid Value May be Incorrect After Exit From Core C6 (CC6) State.) So, >>>> use non-precise cycles as default event on affected processors. >>> >>> It seems like a kernel issue, do we have a kernel patch not to forward >>> precise cycles or instructions events to IBS on the affected CPUs? >> >> I'm not sure how it's a kernel issue. User can use ibs_op// pmu directly >> and might hit the hw bug. > > Sorry for the late reply. I know it's the user's fault when using ibs_op// > directly but I think the kernel should not forward cycles:pp to IBS. For all AMD zen uarchs, cycles:p is same as ibs_op// (man perf-list has more detail). It's confusing if ibs_op// works but cycles:p fails on the same machine. No strong opinion though. I can prepare a kernel patch, if you want. Thanks, Ravi