perf/x86: Fix low freqency setting issue

Perf doesn't work at low frequencies:

  $ perf record -e cpu_core/instructions/ppp -F 120
  Error:
  The sys_perf_event_open() syscall returned with 22 (Invalid argument)
  for event (cpu_core/instructions/ppp).
  "dmesg | grep -i perf" may provide additional information.

The limit_period() check avoids a low sampling period on a counter. It
doesn't intend to limit the frequency.

The check in the x86_pmu_hw_config() should be limited to non-freq mode.
The attr.sample_period and attr.sample_freq are union. The
attr.sample_period should not be used to indicate the frequency mode.

Fixes: c46e665f0377 ("perf/x86: Add INST_RETIRED.ALL workarounds")
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/20250117151913.3043942-1-kan.liang@linux.intel.com
Closes: https://lore.kernel.org/lkml/20250115154949.3147-1-ravi.bangoria@amd.com/

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 8f218ac0d445c6f1a691291e8fd1e39507b9ebf4..2092d615333da502787fb3d7dcc723a45434ea9c 100644 (file)
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -628,7 +628,7 @@ int x86_pmu_hw_config(struct perf_event *event)
        if (event->attr.type == event->pmu->type)
                event->hw.config |= x86_pmu_get_event_config(event);
 
-       if (event->attr.sample_period && x86_pmu.limit_period) {
+       if (!event->attr.freq && x86_pmu.limit_period) {
                s64 left = event->attr.sample_period;
                x86_pmu.limit_period(event, &left);
                if (left > event->attr.sample_period)