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

[Dongli Zhang <dongli.zhang@oracle.com>]

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 = {