Re: [Xen-devel] [PATCH 1/3] x86/spec-ctrl: add AMD SSBD LS_CFG in init print

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 01.08.18 at 23:38, <brian.woods@xxxxxxx> wrote:
> On Tue, Jul 31, 2018 at 04:47:48AM -0600, Jan Beulich wrote:
>> Why log the same string twice? Simply OR together both conditions.
>> Also please don't omit the blank before the ? operator. Both remarks
>> apply as well further down.
> 
> Because they're completely different implementation at this point.  I
> thought about naming it something else but couldn't think of something.
> It also reads easier with having them split up where there isn't a ton
> of logic in a single ternary operator.  There can be easily changed.

Well, I'm not going to insist, but I'd prefer things to be as suggested,
to be in line with other similar code. Let's see what Andrew thinks.

>> I've peeked ahead into the following patches, and I can't see
>> why this needs to be a synthetic feature flag. We use such flags
>> for the purpose of alternative instruction patching, but you don't
>> do anything like that.
> 
> I was talking Andy earily about a SSBD (via VIRT_SPEC_CTRL)
> implementation and he mentioned something about ALTERNATIVE C funcs
> which would allow to allow HVM guests to be able control SSBD.  In that
> case having a synthetic feature flag is useful for helping to
> differiate between SSBD via the LS_CFG MSR vs SPEC_CTRL in the future.

I'd much appreciate if such would be introduced once actually
needed, not early on just in case.

Jan



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