Re: [PATCH v3 0/4] KVM: TDX: Validate directly configurable CPUID bits

[Xiaoyao Li]

On 9/2/2026 9:53 PM, Edgecombe, Rick P wrote:
> On Wed, 2026-09-02 at 21:39 +0800, Xiaoyao Li wrote:
>>> I don't think they have agreed to it yet (Binbin?), but I think it mostly
>>> works this way already. Why do you think it is a burden on TDX module
>>> developers?
>>
>> Because it can bring confusion to TDX module developers. VM_EXIT_LOAD_XXX
>> control is used by SEAM VMCS to load states for TDX module execution context.
>> And I think for most features SEAM VMCS doesn't set it (I don't check it
>> though).
>>
>> SEAMCALL is kind of a VM exit, and SEAMRET is kind of a VM entry. To
>> automatically save and restore the host state, what TDX needs are
>> VM_EXIT_SAVE_XXX, VM_ENTRY_LOAD_XXX, and vmcs guest state for XXX.
> 
> I'd think we could avoid adding options for configuration that won't be used. If
> we did have a clobber control interface, matching VMX bits is an interesting
> idea.
> 
> I'm a bit torn between wanting to fix the area once and for all with a full
> solution, and wanting to get this increasingly blocking CPUID bit fix in. 

> I'm
> leaning towards just do the bit filtering and give the save/restore guidelines.

I agree.

I always believe the bit filtering introduced by this series makes KVM
safer and it's anyway useful, while how TDX/TDX module save/restore host
states can be another separate topic.

> Then we can do a save/restore control later if we find the guidelines are not
> sufficient.