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SubjectRe: [PATCH v5 03/17] x86/acrn: Introduce an API to check if a VM is privileged
On Tue  3.Nov'20 at 11:25:38 +0100, Borislav Petkov wrote:
>On Tue, Nov 03, 2020 at 02:27:18PM +0800, Shuo A Liu wrote:
>> The code just followed KVM style (see kvm_arch_para_features()).
>
>Do you see Documentation/virt/kvm/cpuid.rst?

OK. It documents the leaf number.

>
>Now where is yours explaining what your hypervisor is doing?

Currently, it is in arch/x86/include/asm/acrn.h.

>
>> I can change to use
>> cpuid_eax(acrn_cpuid_base() + 1)...
>> If you prefer to.
>
>Yes please.

Sure.

If the leaf numbers be documented explicitly (like kvm), i think i can
use them as eax of cpuid_eax() directly (back to your first comment).
cpuid_eax(ACRN_CPUID_FEATURES)...

If you looking at implementation of acrn-hypervisor, you will found the
leaf number is hardcoded in the hypervisor. So, they also can be
documented explicitly.

>
>> hypervisor_cpuid_base() implies the base is variable, no? We use
>> this function to detect the base.
>
>Yes, but you need to document all that and make it clear and
>understandable. If Linux is supposed to run as an acrn guest, that
>interface better be documented just like KVM does.

OK. I can add a similar cpuid.rst for acrn.

>
>Also, if there's a bug in the KVM guest/host interface, we might be able
>to fix it modulo ABI. Is that possible with acrn?
>
>I'm guessing the answer to that is yes if I'm looking at
>
>https://github.com/projectacrn/acrn-hypervisor
>
>?

Yes. Fix patches are always welcome.

>
>> OK. Then i will define acrn_cpuid_base() as a static inline function
>> in asm/acrn.h for callers.
>
>Yah, that function is simple enough.


Thanks
shuo

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