Re: [PATCH] x86/speculation: Avoid LFENCE in FILL_RETURN_BUFFER on CPUs that lack it

[Martin-Éric Racine]

On Fri, Aug 19, 2022 at 2:01 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> I'm not entirly sure what to do here. On the one hand, it's 32bit, so
> who gives a crap, otoh we shouldn't break these ancient chips either I
> suppose.

This is something that I've repeatedly had to bring up, whenever
something breaks because someone meant well by enabling more security
bells and whistles:

x86-32 is by definition legacy hardware. Enabling more bells and
whistles essentially kills support for all but the very latest
variants of the x86-32 family. This is the wrong approach. The right
approach is to accept that building for x86-32 inherently means
building for older and thus less secure architectures.

Martin-Éric