Re: [PATCH v19 130/130] RFC: KVM: x86, TDX: Add check for KVM_SET_CPUID2

Edgecombe, Rick P
2024-03-25T15:33:23Z

On Mon, 2024-03-25 at 11:14 +0000, Huang, Kai wrote:
> To confirm, I mean you want to simply make KVM_SET_CPUID2 return error for TDX
> guest?
>
> It is acceptable to me, and I don't see any conflict with Sean's comments.
>
> But I don't know Sean's perference.  As he said, I think  the consistency
> checking is quite straight-forward:
>
> "
> It's not complicated at all.  Walk through the leafs defined during
> TDH.MNG.INIT, reject KVM_SET_CPUID if a leaf isn't present or doesn't match
> exactly.
> "
>
Yea, I'm just thinking if we could take two patches down to one small one it might be a way to
essentially break off this work to another series without affecting the ability to boot a TD. It
*seems* to be the way things are going.

> So to me it's not a big deal.
>
> Either way, we need a patch to handle SET_CPUID2:
>
> 1) if we go option 1) -- that is reject SET_CPUID2 completely -- we need to make
> vcpu's CPUID point to KVM's saved CPUID during TDH.MNG.INIT.

Ah, I missed this part. Can you elaborate? By dropping these two patches it doesn't prevent a TD
boot. If we then reject SET_CPUID, this will break things unless we make other changes? And they are
not small?