Revision 61d03862734360aad470019f160d484403a3923e authored by Mark Rutland on 16 February 2023, 14:12:38 UTC, committed by Will Deacon on 16 February 2023, 21:23:52 UTC
Janne reports that perf has been broken on Apple M1 as of commit: bd27568117664b8b ("perf: Rewrite core context handling") That commit replaced the pmu::filter_match() callback with pmu::filter(), whose return value has the opposite polarity, with true implying events should be ignored rather than scheduled. While an attempt was made to update the logic in armv8pmu_filter() and armpmu_filter() accordingly, the return value remains inverted in a couple of cases: * If the arm_pmu does not have an arm_pmu::filter() callback, armpmu_filter() will always return whether the CPU is supported rather than whether the CPU is not supported. As a result, the perf core will not schedule events on supported CPUs, resulting in a loss of events. Additionally, the perf core will attempt to schedule events on unsupported CPUs, but this will be rejected by armpmu_add(), which may result in a loss of events from other PMUs on those unsupported CPUs. * If the arm_pmu does have an arm_pmu::filter() callback, and armpmu_filter() is called on a CPU which is not supported by the arm_pmu, armpmu_filter() will return false rather than true. As a result, the perf core will attempt to schedule events on unsupported CPUs, but this will be rejected by armpmu_add(), which may result in a loss of events from other PMUs on those unsupported CPUs. This means a loss of events can be seen with any arm_pmu driver, but with the ARMv8 PMUv3 driver (which is the only arm_pmu driver with an arm_pmu::filter() callback) the event loss will be more limited and may go unnoticed, which is how this issue evaded testing so far. Fix the CPU filtering by performing this consistently in armpmu_filter(), and remove the redundant arm_pmu::filter() callback and armv8pmu_filter() implementation. Commit bd2756811766 also silently removed the CHAIN event filtering from armv8pmu_filter(), which will be addressed by a separate patch without using the filter callback. Fixes: bd2756811766 ("perf: Rewrite core context handling") Reported-by: Janne Grunau <j@jannau.net> Link: https://lore.kernel.org/asahi/20230215-arm_pmu_m1_regression-v1-1-f5a266577c8d@jannau.net/ Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi Bangoria <ravi.bangoria@amd.com> Cc: Asahi Lina <lina@asahilina.net> Cc: Eric Curtin <ecurtin@redhat.com> Tested-by: Janne Grunau <j@jannau.net> Link: https://lore.kernel.org/r/20230216141240.3833272-2-mark.rutland@arm.com Signed-off-by: Will Deacon <will@kernel.org>
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