| Message ID | 20230216141240.3833272-3-mark.rutland@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm_pmu: fix fallout from context handling rewrite | expand |
diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c index 3e43538f6b72..dde06c0f97f3 100644 --- a/arch/arm64/kernel/perf_event.c +++ b/arch/arm64/kernel/perf_event.c @@ -1063,6 +1063,14 @@ static int __armv8_pmuv3_map_event(struct perf_event *event, &armv8_pmuv3_perf_cache_map, ARMV8_PMU_EVTYPE_EVENT); + /* + * CHAIN events only work when paired with an adjacent counter, and it + * never makes sense for a user to open one in isolation, as they'll be + * rotated arbitrarily. + */ + if (hw_event_id == ARMV8_PMUV3_PERFCTR_CHAIN) + return -EINVAL; + if (armv8pmu_event_is_64bit(event)) event->hw.flags |= ARMPMU_EVT_64BIT;
Currently it's possible for a user to open CHAIN events arbitrarily, which we previously tried to rule out in commit: ca2b497253ad01c8 ("arm64: perf: Reject stand-alone CHAIN events for PMUv3") Which allowed the events to be opened, but prevented them from being scheduled by by using an arm_pmu::filter_match hook to reject the relevant events. The CHAIN event filtering in the arm_pmu::filter_match hook was silently removed in commit: bd27568117664b8b ("perf: Rewrite core context handling") As a result, it's now possible for users to open CHAIN events, and for these to be installed arbitrarily. Fix this by rejecting CHAIN events at creation time. This avoids the creation of events which will never count, and doesn't require using the dynamic filtering. Attempting to open a CHAIN event (0x1e) will now be rejected: | # ./perf stat -e armv8_pmuv3/config=0x1e/ ls | perf | | Performance counter stats for 'ls': | | <not supported> armv8_pmuv3/config=0x1e/ | | 0.002197470 seconds time elapsed | | 0.000000000 seconds user | 0.002294000 seconds sys Other events (e.g. CPU_CYCLES / 0x11) will open as usual: | # ./perf stat -e armv8_pmuv3/config=0x11/ ls | perf | | Performance counter stats for 'ls': | | 2538761 armv8_pmuv3/config=0x11/ | | 0.002227330 seconds time elapsed | | 0.002369000 seconds user | 0.000000000 seconds sys Fixes: bd27568117664b8b ("perf: Rewrite core context handling") Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi Bangoria <ravi.bangoria@amd.com> Cc: Will Deacon <will@kernel.org> --- arch/arm64/kernel/perf_event.c | 8 ++++++++ 1 file changed, 8 insertions(+)