Re: [PATCH v2 3/5] x86/virt/tdx: Detect if the extensions initialization is required

[Edgecombe, Rick P]

On Tue, 2026-09-29 at 17:28 +0800, Xu Yilun wrote:
> Another thing is about the addon_features0 argument for TDH.SYS.UPDATE.
> In v1 -> v2, in order to meet the goal of "just restore everything that
> was configured during boot", this bitmap argument is removed. I think
> this argument removal is orthogonal to the TDH.EXT.INIT discussion and
> still has merit.
> 
>   TDH.SYS.UPDATE(v0): TDX module reconfigures same features as specified by
> 		      TDH.SYS.CONFIG, Linux would use this SEAMCALL version.
> 
>   TDH.SYS.UPDATE(v1, addon_featues0): VMM can configure new features specified
> 				      by addon_features0 argument. For other
> VMM.
> 
> Then we can just add one patch based on v2 series:

Yea that seems like a good way to do this.

Some of the nuance that was extracted was that there is a difference between
update and changing configuration. For example TDH.QUOTE.INIT was considered
reconfiguration because it generates a new key. Similarly, changing which add-
ons are enabled seems like reconfiguration. So it could be a separate knob.

Let's follow up internally with the TDX folks to clarify that we don't want to
pass addon bits into update. And see if anyone yells. I'm not sure the previous
discussion covered this case.