Re: [PATCH v7 06/22] coco/tdx-host: Expose P-SEAMLDR information via sysfs

Chao Gao
2026-04-14T11:21:13Z

On Tue, Apr 14, 2026 at 03:08:33AM +0800, Edgecombe, Rick P wrote:
>On Tue, 2026-03-31 at 05:41 -0700, Chao Gao wrote:
>> TDX module updates require userspace to select the appropriate module
>> to load. Expose necessary information to facilitate this decision. Two
>> values are needed:
>>
>> - P-SEAMLDR version: for compatibility checks between TDX module and
>>      P-SEAMLDR
>> - num_remaining_updates: indicates how many updates can be performed
>
>Can you explain how all of these overlap?
> - TDX module supports module update
> - SEAMLDR supports NUM_REMAINING_UPDATES info
> - SEAMLDR supports VERSION info
>
>If the TDX module supports module update, do we know the SEAMLDR supports this
>other stuff somehow? It might be worth a comment the reasoning.

VERSION and NUM_REMAINING_UPDATES are always available for any P-SEAMLDR. They
don't depend on TDX module's update support.

>
>>
>> Expose them as tdx-host device attributes. Make seamldr attributes
>> visible only when the update feature is supported, as that's their sole
>> purpose.
>>
>> Unconditional exposure is also problematic because reading them
>> triggers P-SEAMLDR calls that break KVM on CPUs with a specific erratum
>> (to be enumerated and handled in a later patch).
>
>Since this is later handled with the errata check, what is the point being made
>here?

I will drop it. Dave also questioned mentioning the erratum here.