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SubjectRe: [PATCH] perf/x86/intel: Hide Topdown metrics events if slots is not enumerated
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Ping?

Currently the default "perf stat" may fail on all Icelake KVM VMs.

Thank you very much!

Dongli Zhang

On 9/22/22 13:15, kan.liang@linux.intel.com wrote:
> From: Kan Liang <kan.liang@linux.intel.com>
>
> The below error is observed on Ice Lake VM.
>
> $ perf stat
> Error:
> The sys_perf_event_open() syscall returned with 22 (Invalid argument)
> for event (slots).
> /bin/dmesg | grep -i perf may provide additional information.
>
> In a virtualization env, the Topdown metrics and the slots event haven't
> been supported yet. The guest CPUID doesn't enumerate them. However, the
> current kernel unconditionally exposes the slots event and the Topdown
> metrics events to sysfs, which misleads the perf tool and triggers the
> error.
>
> Hide the perf metrics topdown events and the slots event if the slots
> event is not enumerated.
>
> The big core of a hybrid platform can also supports the perf-metrics
> feature. Fix the hybrid platform as well.
>
> Reported-by: Dongli Zhang <dongli.zhang@oracle.com>
> Tested-by: Dongli Zhang <dongli.zhang@oracle.com>
> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
> ---
> arch/x86/events/intel/core.c | 33 ++++++++++++++++++++++++++++++++-
> 1 file changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index b16c91ac9219..a0a62b67c440 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -5335,6 +5335,19 @@ static struct attribute *intel_pmu_attrs[] = {
> NULL,
> };
>
> +static umode_t
> +td_is_visible(struct kobject *kobj, struct attribute *attr, int i)
> +{
> + /*
> + * Hide the perf metrics topdown events
> + * if the slots is not enumerated.
> + */
> + if (x86_pmu.num_topdown_events)
> + return (x86_pmu.intel_ctrl & INTEL_PMC_MSK_FIXED_SLOTS) ? attr->mode : 0;
> +
> + return attr->mode;
> +}
> +
> static umode_t
> tsx_is_visible(struct kobject *kobj, struct attribute *attr, int i)
> {
> @@ -5370,6 +5383,7 @@ default_is_visible(struct kobject *kobj, struct attribute *attr, int i)
>
> static struct attribute_group group_events_td = {
> .name = "events",
> + .is_visible = td_is_visible,
> };
>
> static struct attribute_group group_events_mem = {
> @@ -5522,6 +5536,23 @@ static inline int hybrid_find_supported_cpu(struct x86_hybrid_pmu *pmu)
> return (cpu >= nr_cpu_ids) ? -1 : cpu;
> }
>
> +static umode_t hybrid_td_is_visible(struct kobject *kobj,
> + struct attribute *attr, int i)
> +{
> + struct device *dev = kobj_to_dev(kobj);
> + struct x86_hybrid_pmu *pmu =
> + container_of(dev_get_drvdata(dev), struct x86_hybrid_pmu, pmu);
> +
> + if (!is_attr_for_this_pmu(kobj, attr))
> + return 0;
> +
> + /* Only check the big core which supports perf metrics */
> + if (pmu->cpu_type == hybrid_big)
> + return (pmu->intel_ctrl & INTEL_PMC_MSK_FIXED_SLOTS) ? attr->mode : 0;
> +
> + return attr->mode;
> +}
> +
> static umode_t hybrid_tsx_is_visible(struct kobject *kobj,
> struct attribute *attr, int i)
> {
> @@ -5548,7 +5579,7 @@ static umode_t hybrid_format_is_visible(struct kobject *kobj,
>
> static struct attribute_group hybrid_group_events_td = {
> .name = "events",
> - .is_visible = hybrid_events_is_visible,
> + .is_visible = hybrid_td_is_visible,
> };
>
> static struct attribute_group hybrid_group_events_mem = {

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