From: Kan Liang kan.liang@linux.intel.com
Perf doesn't work with a low freq.
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 freq mode.
Fixes: c46e665f0377 ("perf/x86: Add INST_RETIRED.ALL workarounds") Closes: https://lore.kernel.org/lkml/20250115154949.3147-1-ravi.bangoria@amd.com/ Signed-off-by: Kan Liang kan.liang@linux.intel.com Cc: Andi Kleen ak@linux.intel.com Cc: Ravi Bangoria ravi.bangoria@amd.com Cc: stable@vger.kernel.org --- arch/x86/events/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index 7b6430e5a77b..20ad5cca6ad2 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -630,7 +630,7 @@ 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)
From: Kan Liang kan.liang@linux.intel.com
A low freq cannot be set via IOC_PERIOD on some platforms.
The perf_event_check_period() introduced in commit 81ec3f3c4c4d ("perf/x86: Add check_period PMU callback") intended to check the period, rather than the freq. A low freq may be mistakenly rejected by the limit_period().
Fixes: 81ec3f3c4c4d ("perf/x86: Add check_period PMU callback") Closes: https://lore.kernel.org/lkml/20250115154949.3147-1-ravi.bangoria@amd.com/ Signed-off-by: Kan Liang kan.liang@linux.intel.com Cc: Jiri Olsa jolsa@redhat.com Cc: Ravi Bangoria ravi.bangoria@amd.com Cc: stable@vger.kernel.org --- kernel/events/core.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c index f91ba29048ce..a9a04d4f3619 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5960,14 +5960,15 @@ 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);
On 17-Jan-25 8:49 PM, kan.liang@linux.intel.com wrote:
From: Kan Liang kan.liang@linux.intel.com
A low freq cannot be set via IOC_PERIOD on some platforms.
The perf_event_check_period() introduced in commit 81ec3f3c4c4d ("perf/x86: Add check_period PMU callback") intended to check the period, rather than the freq. A low freq may be mistakenly rejected by the limit_period().
Fixes: 81ec3f3c4c4d ("perf/x86: Add check_period PMU callback") Closes: https://lore.kernel.org/lkml/20250115154949.3147-1-ravi.bangoria@amd.com/ Signed-off-by: Kan Liang kan.liang@linux.intel.com Cc: Jiri Olsa jolsa@redhat.com Cc: Ravi Bangoria ravi.bangoria@amd.com Cc: stable@vger.kernel.org
Reviewed-by: Ravi Bangoria ravi.bangoria@amd.com
Thanks, Ravi
On 17-Jan-25 8:49 PM, kan.liang@linux.intel.com wrote:
From: Kan Liang kan.liang@linux.intel.com
Perf doesn't work with a low freq.
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 freq mode.
Fixes: c46e665f0377 ("perf/x86: Add INST_RETIRED.ALL workarounds") Closes: https://lore.kernel.org/lkml/20250115154949.3147-1-ravi.bangoria@amd.com/ Signed-off-by: Kan Liang kan.liang@linux.intel.com Cc: Andi Kleen ak@linux.intel.com Cc: Ravi Bangoria ravi.bangoria@amd.com Cc: stable@vger.kernel.org
Reviewed-by: Ravi Bangoria ravi.bangoria@amd.com
Thanks, Ravi
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Ravi Bangoria