On 18/07/2017 13:29, Igor Mammedov wrote:
>> It may add a few additional CPU cycles, but I really doubt we can
>> find a workload where CPUID speed has measurable impact. See,
>> for example, how expensive the kernel KVM CPUID code
>> (kvm_cpuid(), kvm_find_cpuid_entry()) is.
>
> I don't expect that it would affect KVM, but for TCG any instruction
> execution is 'fast' path, so I'd leave current cpu_x86_cpuid()
> not to loose those few cycles, it's not worth sacrifice for the sake of
> cleanup.
It's not like this does a QOM property lookup or anything. I think the
patch is a good idea.
Even simpler way to write the cpuid code:
int base = (index - 0x80000002) * 16;
char model[16];
if (strnlen(env->model_id, base) < base) {
memset(model, 0, sizeof(model));
} else {
strncpy(model, env->model_id + base, sizeof(model));
}
*eax = ldl_le_p(&model[0]);
*ebx = ldl_le_p(&model[4]);
*ecx = ldl_le_p(&model[8]);
*edx = ldl_le_p(&model[12]);
Paolo
