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author | Mark Rutland <mark.rutland@arm.com> | 2023-02-16 17:12:38 +0300 |
---|---|---|
committer | Will Deacon <will@kernel.org> | 2023-02-17 00:23:52 +0300 |
commit | 61d03862734360aad470019f160d484403a3923e (patch) | |
tree | 23719bfe5d8b65378521db90354a938b143f0409 /include/linux | |
parent | a428eb4b99ab80454f06ad256b25e930fe8a4954 (diff) | |
download | linux-61d03862734360aad470019f160d484403a3923e.tar.xz |
arm_pmu: fix event CPU filtering
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>
Diffstat (limited to 'include/linux')
-rw-r--r-- | include/linux/perf/arm_pmu.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h index ef914a600087..525b5d64e394 100644 --- a/include/linux/perf/arm_pmu.h +++ b/include/linux/perf/arm_pmu.h @@ -100,7 +100,6 @@ struct arm_pmu { void (*stop)(struct arm_pmu *); void (*reset)(void *); int (*map_event)(struct perf_event *event); - bool (*filter)(struct pmu *pmu, int cpu); int num_events; bool secure_access; /* 32-bit ARM only */ #define ARMV8_PMUV3_MAX_COMMON_EVENTS 0x40 |