Re: [PATCH 03/20] perf/x86/intel: Parse CPUID archPerfmonExt leaves for non-hybrid CPUs

[Liang, Kan]

On 2025-01-23 1:58 p.m., Andi Kleen wrote:
>> +	/*
>> +	 * The archPerfmonExt (0x23) includes an enhanced enumeration of
>> +	 * PMU architectural features with a per-core view. For non-hybrid,
>> +	 * each core has the same PMU capabilities. It's good enough to
>> +	 * update the x86_pmu from the booting CPU. For hybrid, the x86_pmu
>> +	 * is used to keep the common capabilities. Still keep the values
>> +	 * from the leaf 0xa. The core specific update will be done later
>> +	 * when a new type is online.
>> +	 */
>> +	if (!is_hybrid() && boot_cpu_has(X86_FEATURE_ARCH_PERFMON_EXT))
>> +		update_pmu_cap(NULL);
> 
> It seems ugly to have these different code paths. Couldn't non hybrid
> use x86_pmu in the same way? I assume it would be a larger patch.

The current non-hybrid is initialized in the intel_pmu_init(). But some
of the initialization code for the hybrid is in the
intel_pmu_cpu_starting(). Yes, it's better to move it together. It
should be a larger patch. Since it's impacted other features, a separate
patch set should be required.

Thanks,
Kan