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That means >>>>> it needs to set exclude_kernel bit in the attribute but IBS driver >>>>> would reject it since it has PERF_PMU_CAP_NO_EXCLUDE. This is not what >>>>> we want and I've been getting requests to fix this issue. >>>>> >>>>> This should be done in the hardware, but until we get the HW fix we may >>>>> allow exclude_{kernel,user} in the attribute and silently drop the >>>>> samples in the PMU IRQ handler. It won't guarantee the sampling >>>>> frequency or even it'd miss some with fixed period too. Not ideal, >>>>> but that'd still be helpful to regular users. >>>> >>>> Urgh.... this is really rather bad. And I'm sure a bunch of people are >>>> going to be spending a lot of time trying to figure out why their >>>> results don't make sense. >>> >>> I agree it can be confusing but there are use cases where regular users >>> want IBS information like memory data source, data address and so on. >> >> Sure, but I'm a bit worried about users not being aware of this >> trickery. This makes IBS events that have exclude_kernel=1 behave >> significantly different from those that don't have it. >> >> At the very least you should kill the IBS forward in amd_pmu_hw_config() >> when this is active. But perhaps we should also emit a one time >> KERN_INFO message when such an event gets created? > > What about adding a pseudo config or format for a special event that > allows exclude_kernel=1 and drops samples? Maybe we could use > attr.config = 0xffffffff or attr.config=1 or something. attr.config is directly mapped to bitmaps of IBS_OP_CTL. We can't abuse reserved bits also since they might become valid control bits in future. Maybe use config2 or config3 which are ignored by IBS driver currently. Thanks, Ravi