perf/core: Fix low freq setting via IOC_PERIOD

A low attr::freq value cannot be set via IOC_PERIOD on some platforms.

The perf_event_check_period() introduced in:

  81ec3f3c4c4d ("perf/x86: Add check_period PMU callback")

was intended to check the period, rather than the frequency.
A low frequency may be mistakenly rejected by limit_period().

Fix it.

Fixes: 81ec3f3c4c4d ("perf/x86: Add check_period PMU callback")
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250117151913.3043942-2-kan.liang@linux.intel.com
Closes: https://lore.kernel.org/lkml/20250115154949.3147-1-ravi.bangoria@amd.com/

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 086d46d0969630cd73e375810e187541fb7d33e0..6364319e2f888720c00eb2bdcafce0326364e402 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5969,14 +5969,15 @@ static int _perf_event_period(struct perf_event *event, u64 value)
        if (!value)
                return -EINVAL;
 
-       if (event->attr.freq && value > sysctl_perf_event_sample_rate)
-               return -EINVAL;
-
-       if (perf_event_check_period(event, value))
-               return -EINVAL;
-
-       if (!event->attr.freq && (value & (1ULL << 63)))
-               return -EINVAL;
+       if (event->attr.freq) {
+               if (value > sysctl_perf_event_sample_rate)
+                       return -EINVAL;
+       } else {
+               if (perf_event_check_period(event, value))
+                       return -EINVAL;
+               if (value & (1ULL << 63))
+                       return -EINVAL;
+       }
 
        event_function_call(event, __perf_event_period, &value);