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

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Message-ID: <aXsOZ4UdLOS0xXeM@yilunxu-OptiPlex-7050>
Date: Thu, 29 Jan 2026 15:38:15 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: Chao Gao <chao.gao@...el.com>
Cc: linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, x86@...nel.org, reinette.chatre@...el.com,
	ira.weiny@...el.com, kai.huang@...el.com, dan.j.williams@...el.com,
	sagis@...gle.com, vannapurve@...gle.com, paulmck@...nel.org,
	nik.borisov@...e.com, zhenzhong.duan@...el.com, seanjc@...gle.com,
	rick.p.edgecombe@...el.com, kas@...nel.org,
	dave.hansen@...ux.intel.com, vishal.l.verma@...el.com
Subject: Re: [PATCH v3 05/26] coco/tdx-host: Expose TDX Module version

On Fri, Jan 23, 2026 at 06:55:13AM -0800, 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.
> 
> 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
> 
> One bonus of exposing TDX Module version via sysfs is: TDX Module
> version information remains available even after dmesg logs are cleared.
> 
> Signed-off-by: Chao Gao <chao.gao@...el.com>
> Link: https://lore.kernel.org/all/2025073035-bulginess-rematch-b92e@gregkh/ # [1]

Reviewed-by: Xu Yilun <yilun.xu@...ux.intel.com>