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authorMark Rutland <mark.rutland@arm.com>2023-02-16 17:12:38 +0300
committerWill Deacon <will@kernel.org>2023-02-17 00:23:52 +0300
commit61d03862734360aad470019f160d484403a3923e (patch)
tree23719bfe5d8b65378521db90354a938b143f0409 /drivers
parenta428eb4b99ab80454f06ad256b25e930fe8a4954 (diff)
downloadlinux-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 'drivers')
-rw-r--r--drivers/perf/arm_pmu.c8
1 files changed, 1 insertions, 7 deletions
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index 9b593f985805..40f70f83daba 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -550,13 +550,7 @@ static void armpmu_disable(struct pmu *pmu)
static bool armpmu_filter(struct pmu *pmu, int cpu)
{
struct arm_pmu *armpmu = to_arm_pmu(pmu);
- bool ret;
-
- ret = cpumask_test_cpu(cpu, &armpmu->supported_cpus);
- if (ret && armpmu->filter)
- return armpmu->filter(pmu, cpu);
-
- return ret;
+ return !cpumask_test_cpu(cpu, &armpmu->supported_cpus);
}
static ssize_t cpus_show(struct device *dev,