Re: [PATCH v7 16/22] x86/virt/tdx: Update tdx_sysinfo and check features post-update

[Chao Gao]

>+int tdx_module_post_update(struct tdx_sys_info *info)
>+{
>+	struct tdx_sys_info_version *old, *new;
>+	int ret;
>+
>+	/* Shouldn't fail as the update has succeeded. */
>+	ret = get_tdx_sys_info(info);
>+	if (WARN_ONCE(ret, "version retrieval failed after update, replace the TDX module\n"))
>+		return ret;

Dave's comment on another patch applies here too: don't preemptively handle
errors that never occur. The custom error message is unnecessary, and
propagating the error isn't worth it. Will simplify it to:

	/* Shouldn't fail as the update has succeeded. */
	WARN_ON_ONCE(get_tdx_sys_info(info));

>+
>+	old = &tdx_sysinfo.version;
>+	new = &info->version;
>+	pr_info("version " TDX_VERSION_FMT " -> " TDX_VERSION_FMT "\n",
>+		old->major_version, old->minor_version, old->update_version,
>+		new->major_version, new->minor_version, new->update_version);
>+
>+	/*
>+	 * Blindly refreshing the entire tdx_sysinfo could disrupt running
>+	 * software, as it may subtly rely on the previous state unless
>+	 * proven otherwise.
>+	 *
>+	 * Only refresh update_version and handoff version. They don't
>+	 * affect TDX functionality. Major/minor versions do not change
>+	 * across updates, so no refresh is needed.
>+	 */
>+	tdx_sysinfo.version.update_version	= info->version.update_version;
>+	tdx_sysinfo.handoff			= info->handoff;
>+
>+	if (!memcmp(&tdx_sysinfo, info, sizeof(*info)))
>+		return 0;
>+
>+	pr_info("TDX module features have changed after updates, but might not take effect.\n");
>+	pr_info("Please consider updating your BIOS to install the TDX module.\n");
>+	return 0;
>+}