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Janne reports that perf has been broken on Apple M1 as of commit:
bd27568117 ("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 bd27568117 also silently removed the CHAIN event filtering from
armv8pmu_filter(), which will be addressed by a separate patch without
using the filter callback.
Fixes: bd27568117 ("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>
61d0386273