Re: [PATCH v3 24/27] KVM: nVMX: Add a prerequisite to existence of VMCS fields

[Xin Li]

On 2/25/2025 8:22 AM, Sean Christopherson wrote:
> On Mon, Sep 30, 2024, Xin Li (Intel) wrote:
> > Add a prerequisite to existence of VMCS fields as some of them exist
> > only on processors that support certain CPU features.
> >
> > This is required to fix KVM unit test VMX_VMCS_ENUM.MAX_INDEX.
>
> If making the KVM-Unit-Test pass is the driving force for this code, then NAK.
> We looked at this in detail a few years back, and came to the conclusion that
> trying to precisely track which fields are/aren't supported would likely do more
> harm than good.

I have to agree, it's no fun to track a VMCS field is added by which 
feature(s), and worst part is that one VMCS field could depend on 2+ 
totally irrelevant features, e.g., the secondary VM exit controls field 
exits on CPU that supports:

1) FRED
2) Prematurely busy shadow stack

Thanks for making the ground rule clear.

BTW, why don't we just remove this VMX_VMCS_ENUM.MAX_INDEX test?

    Xin


> https://lore.kernel.org/all/1629192673-9911-4-git-send-email-robert.hu@xxxxxxxxxxxxxxx