Re: [PATCH v2 2/6] x86: reduce CET-SS related #ifdef-ary

[Jan Beulich <jbeulich@xxxxxxxx>]

On 13.10.2020 13:20, Andrew Cooper wrote:
> On 28/09/2020 13:30, Jan Beulich wrote:
>> Commit b586a81b7a90 ("x86/CET: Fix build following c/s 43b98e7190") had
>> to introduce a number of #ifdef-s to make the build work with older tool
>> chains. Introduce an assembler macro covering for tool chains not
>> knowing of CET-SS, allowing some conditionals where just SETSSBSY is the
>> problem to be dropped again.
>>
>> No change to generated code.
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>> ---
>> Now that I've done this I'm no longer sure which direction is better to
>> follow: On one hand this introduces dead code (even if just NOPs) into
>> CET-SS-disabled builds. Otoh this is a step towards breaking the tool
>> chain version dependency of the feature.
> 
> I've said before.  You cannot break the toolchain dependency without
> hardcoding memory operands.  I'm not prepared to let that happen.
> 
> There is no problem requiring newer toolchains for newer features
> (you're definitely not having CET-IBT, for example), and there is a
> (unacceptably, IMO) large cost to this work.

I'm aware of your view. What remains unclear to me is whether your
reply is merely a remark on this post-commit-message comment, or
whether it is an objection to the tidying (as I view it) the patch
does.

Jan