Re: [PATCH 1/2][4.15?] x86/shadow: suppress "fast fault path" optimization when running virtualized

[Ian Jackson <iwj@xxxxxxxxxxxxxx>]

Andrew Cooper writes ("Re: [PATCH 1/2][4.15?] x86/shadow: suppress "fast fault 
path" optimization when running virtualized"):
> This wants backporting to stable releases, so I would recommend for 4.15
> even at this point.

Can someone explain to me the implications of not taking these patch,
and the risks of taking them ?

AFIACT the implications of not taking 1/ are that we would misbehave
in a security relevant way, sometimes, when we are running under
another hypervisor ?

And the implications of not taking 2/ is a performance problem ?

As to the risks, 1/ looks obviously correct even to me.

2/ seems complex.  What would go wrong if there were a misplaced ) or
confused bit-twiddling or something ?

Ian.