Re: [PATCH 7/9] x86/hvm: Disable MPX by default

[Jan Beulich <jbeulich@xxxxxxxx>]

On 17.06.2020 13:28, Andrew Cooper wrote:
> We actually have AVX512 disabled by default in XenServer.  The perf
> implications of letting 1 guest play with it is very severe.
> 
> Now I think about it, I'm tempted to recommend it moves out of default
> generally.

Hmm, I'm tempted to ask whether you're kidding. This is the kind of
feature that I see no reason at all to move out of default. Imo we
shouldn't put in place policy like this - if anything shouldn't be
on by default, it should imo be because of limitations in our
handling (I've recently revived my UMIP emulation patch, which
comes to mind here) or because of uncertainty on some aspects (like
is the case for MOVDIR / ENQCMD for example). Anything else should
be left to the admins to decide.

Jan