Re: [PATCH v3 05/26] coco/tdx-host: Expose TDX Module version

[Dave Hansen]

On 1/23/26 06:55, Chao Gao wrote:
...
> This approach follows the pattern used by microcode updates and
> other CoCo implementations:
> 
> 1. AMD has a PCI device for the PSP for SEV which provides an
> existing place to hang their equivalent metadata.
> 
> 2. ARM CCA will likely have a faux device (although it isn't obvious
> if they have a need to export version information there) [1]
> 
> 3. Microcode revisions are exposed as CPU device attributes

I kinda disagree with the idea that this follows existing patterns. It
uses a *NEW* pattern.

AMD doesn't use a faux device because they *HAVE* a PCI device in their
architecture. TDX doesn't have a PCI device in its hardware architecture.

ARM CCA doesn't exist in the tree.

CPU microcode doesn't use a faux device. For good reason. The microcode
version is *actually* per-cpu. It can differ between CPU cores. The TDX
module version is not per-cpu. There's one and only one global module.
This is the reason that we need a global, unique device for TDX.

I'm not saying that being new is a bad thing. But let's not pretend this
is following any kind of existing pattern. Let's explain *why* it needs
to be different.