Re: [PATCH V4 1/7] KVM, pkeys: expose CPUID/CR4 to guest

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

On 03/07/2016 07:20 AM, Paolo Bonzini wrote:
>
>
> On 06/03/2016 08:15, Xiao Guangrong wrote:
>>> +    /* cpuid 7.0.ecx*/
>>> +    const u32 kvm_supported_word11_x86_features = F(PKU) | 0 /*OSPKE*/;
>>> +
>>>
>>>                cpuid_mask(&entry->ebx, 9);
>>>                // TSC_ADJUST is emulated
>>>                entry->ebx |= F(TSC_ADJUST);
>>> -        } else
>>> +            entry->ecx &= kvm_supported_word11_x86_features;
>>> +            cpuid_mask(&entry->ecx, 13);
>>
>> Can we use a meaningful name defined by cpuid_leafs instead of the raw
>> number?
>
> This is not a cpuid leaf number, it's the Linux feature word number.  In
> other words, the "11" in kvm_supported_word11_x86_features should have
> matched the "13" in cpuid_mask(&entry->ecx, 13).

But i noticed kernel uses the more meaningful name to update
boot_cpu_data.x86_capability[]:
$ git grep x86_capability arch/x86/
......
arch/x86/kernel/cpu/centaur.c:          c->x86_capability[CPUID_C000_0001_EDX] = cpuid_edx(0xC0000001);
arch/x86/kernel/cpu/common.c:           c->x86_capability[CPUID_1_ECX] = ecx;
arch/x86/kernel/cpu/common.c:           c->x86_capability[CPUID_1_EDX] = edx;
arch/x86/kernel/cpu/common.c:           c->x86_capability[CPUID_7_0_EBX] = ebx;
arch/x86/kernel/cpu/common.c:           c->x86_capability[CPUID_6_EAX] = cpuid_eax(0x00000006);
arch/x86/kernel/cpu/common.c:           c->x86_capability[CPUID_D_1_EAX] = eax;
arch/x86/kernel/cpu/common.c:           c->x86_capability[CPUID_F_0_EDX] = edx;
.....

Why not follow it in KVM?