Hi Zhao,
On 11/10/24 7:29 AM, Zhao Liu wrote:
> 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.
I am going to remove this patch in v2.
Just a reminder, we may have more code in this function by other patches,
including the initialization of both Intel and AMD PMU infortmation (PerfMonV2).
Thank you very much!
Dongli Zhang
>
>> if (((env->cpuid_version >> 8)&0xF) >= 6
>> && (env->features[FEAT_1_EDX] & (CPUID_MCE | CPUID_MCA)) ==
>> (CPUID_MCE | CPUID_MCA)) {
>> --
>> 2.39.3
>>
