Re: [RFC v2-fix-v2 1/1] x86: Introduce generic protected guest abstractionn

[Tom Lendacky]

On 6/4/21 5:15 PM, Borislav Petkov wrote:
> On Fri, Jun 04, 2021 at 05:01:31PM -0500, Tom Lendacky wrote:
>> The first is analogous to sme_active(), the second to sev_active() and the
>> third to mem_encrypt_active(). Just my opinion, though...
> 
> Yeah, or cc_has() where "cc" means "confidential computing". Or "coco"...
> 
> Yeah, no good idea yet.
> 
>> I don't think you want a WARN_ON_ONCE() here. The code will be written to
>> work with either SEV or TDX, so we shouldn't warn on a check for a TDX
>> supported feature when running on AMD (or vice-versa).
> 
> That's an AMD-specific path so it would warn only when a flag is used
> which is unknown/unused yet on AMD.

But the check can happen on Intel or AMD. We have lots of checks for
sme_active() in common code that are executed on Intel today, but they
just return false. It's the same principle, you don't want to WARN on
those, just return false. E.g.:

	/* some common code path */
	if (cc_has(XYZ))
		do_y();

If Intel has XYZ but AMD does not, you don't want to WARN, just return false.

Thanks,
Tom

>