Re: [PATCH v6 03/22] coco/tdx-host: Expose TDX module version

[Xiaoyao Li]

On 3/26/2026 4:43 PM, Chao Gao wrote:
> For TDX module updates, userspace needs to select compatible update
> versions based on the current module version. This design delegates
> module selection complexity to userspace because TDX module update
> policies are complex and version series are platform-specific.
>
> For example, the 1.5.x series is for certain platform generations, while
> the 2.0.x series is intended for others. And TDX module 1.5.x may be
> updated to 1.5.y but not to 1.5.y+1.
>
> Expose the TDX module version to userspace via sysfs to aid module
> selection. Since the TDX faux device will drive module updates, expose
> the version as its attribute.
>
> One bonus of exposing TDX module version via sysfs is: TDX module
> version information remains available even after dmesg logs are cleared.
>
> == Background ==
>
> The "faux device + device attribute" approach compares to other update
> mechanisms as follows:
>
> 1. AMD SEV leverages an existing PCI device for the PSP to expose
>     metadata. TDX uses a faux device as it doesn't have PCI device
>     in its architecture.
>
> 2. Microcode uses per-CPU virtual devices to report microcode revisions
>     because CPUs can have different revisions. But, there is only a
>     single TDX module, so exposing the TDX module version through a global
>     TDX faux device is appropriate
>
> 3. ARM's CCA implementation isn't in-tree yet, but will likely follow a
>     similar faux device approach, though it's unclear whether they need
>     to expose firmware version information
>
> Signed-off-by: Chao Gao<chao.gao@xxxxxxxxx>
> Reviewed-by: Binbin Wu<binbin.wu@xxxxxxxxxxxxxxx>
> Reviewed-by: Tony Lindgren<tony.lindgren@xxxxxxxxxxxxxxx>
> Reviewed-by: Xu Yilun<yilun.xu@xxxxxxxxxxxxxxx>
> Reviewed-by: Kai Huang<kai.huang@xxxxxxxxx>
> Reviewed-by: Kiryl Shutsemau (Meta)<kas@xxxxxxxxxx>

Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>