Subject: Re: [PATCH v9 22/23] coco/tdx-host: Document TDX module update compatibility criteria
From: Dave Hansen <[email-masked]>
To: [email-masked]

[Draft review generated by x86-maintainer-agent applying Dave_Hansen.txt
 rules to the v9 series.  Strip this banner before sending.]

ABI documentation that names the failure modes ("device-busy",
"firmware-invalid"), explains what userspace can do about each, and
ties firmware-invalid to the "tdx_host/version returns -ENXIO"
observable, is exactly the RULE 13 + RULE 20 surface we need
documented before this lands.

One tightening pass:

> +		"firmware-invalid" may be fatal, causing all TDs and the TDX
> +		module to be lost and preventing further TDX operations. This
> +		occurs when reading /sys/devices/faux/tdx_host/version returns
> +		-ENXIO.

Suggest moving the "-ENXIO" observability hint into the version=
attribute's Description as well (it's currently only mentioned in the
error= attribute's Description, so a user looking at version= alone
has no clue that -ENXIO is "the module is dead" rather than "the
kernel doesn't have this feature").  See review on 05/23 for the
matching code-side comment.

Reviewed-by: Dave Hansen <[email-masked]>  [conditional]