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Is >>> the above saying that a host can never IBS profile a guest? >> >> Host can profile a guest with IBS if VIBS is disabled for the guest. This is >> the default behavior. Host can not profile guest if VIBS is enabled for guest. >> >>> >>> Does the current IBS thing assert perf_event_attr::exclude_guest is set? >> >> Unlike AMD core pmu, IBS doesn't have Host/Guest filtering capability, thus >> perf_event_open() fails if exclude_guest is set for an IBS event. > > Then you must not allow VIBS if a host cpu-wide IBS counter exists. > > Also, VIBS reads like it can be (ab)used as a filter. I think I get your point: If host IBS with exclude_guest=0 doesn't capture guest samples because of VIBS, it is an unintended behavior. But if a guest cannot use IBS because a host is using it, that is also unacceptable behavior. Let me think over it and come back. - Manali