Re: [PATCH v4 18/24] x86/virt/tdx: Restore TDX Module state

[Huang, Kai]

On Thu, 2026-02-12 at 06:35 -0800, Chao Gao wrote:
> TDX Module state was packed as handoff data during module shutdown. After
> per-CPU initialization, the new module can restore TDX Module state from
> handoff data to preserve running TDs.
> 
> Once the restoration is done, the TDX Module update is complete, which
> means the new module is ready to handle requests from the host and guests.
> 
> Implement the new TDH.SYS.UPDATE SEAMCALL to restore TDX Module state
> and invoke it for one CPU.

Nit:

"for one CPU" -> "on one CPU since it only needs to be called once".

> 
> Note that Intel® Trust Domain Extensions (Intel® TDX) Module Base
> Architecture Specification, Revision 348549-007, Chapter 4.5.5 states:
> 
>   If TDH.SYS.UPDATE returns an error, then the host VMM can continue
>   with the non-update sequence (TDH.SYS.CONFIG, 15 TDH.SYS.KEY.CONFIG
>   etc.). In this case all existing TDs are lost. Alternatively, the host
>   VMM can request the P-SEAMLDR to update to another TDX Module. If that
>   update is successful, existing TDs are preserved
> 
> The two alternative error handling approaches are not implemented due to
> their complexity and unclear benefits.

Nit: use imperative mode:

Don't implement the two alternative ... due to ...
 
> 
> Also note that the location and the format of handoff data is defined by
> the TDX Module. The new module knows where to get handoff data and how
> to parse it. The kernel doesn't need to provide its location, format etc.
> 
> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
> Reviewed-by: Tony Lindgren <tony.lindgren@xxxxxxxxxxxxxxx>

Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx>