Re: [PATCH 3/7] target/i386/kvm: init PMU information only once

[Zhao Liu <zhao1.liu@intel.com>]

Hi Dongli,

>  int kvm_arch_init_vcpu(CPUState *cs)
>  {
>      struct {
> @@ -2237,6 +2247,13 @@ int kvm_arch_init_vcpu(CPUState *cs)
>      cpuid_i = kvm_x86_build_cpuid(env, cpuid_data.entries, cpuid_i);
>      cpuid_data.cpuid.nent = cpuid_i;
>  
> +    /*
> +     * Initialize PMU information only once for the first vCPU.
> +     */
> +    if (cs == first_cpu) {
> +        kvm_init_pmu_info(env);
> +    }
> +

Thank you for the optimization. However, I think it’s not necessary
because:

* This is not a hot path and not a performance bottleneck.
* Many CPUID leaves are consistent across CPUs, and 0xA is just one of them.
* And encoding them all in kvm_x86_build_cpuid() is a common pattern.
  Separating out 0xa disrupts code readability and fragments the CPUID encoding.

Therefore, code maintainability and correctness might be more important here,
than performance concern.

>      if (((env->cpuid_version >> 8)&0xF) >= 6
>          && (env->features[FEAT_1_EDX] & (CPUID_MCE | CPUID_MCA)) ==
>             (CPUID_MCE | CPUID_MCA)) {
> -- 
> 2.39.3
>