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From:   =?UTF-8?Q?Martin=2D=C3=89ric_Racine?= <martin-eric.racine@iki.fi>
Date:   Fri, 19 Aug 2022 14:33:32 +0300
Message-ID: <CAPZXPQe+MPTGD3MH1HORvCZa08HhdbWy=zh7rLSCwA6edM2Ccg@mail.gmail.com>
Subject: Re: [PATCH] x86/speculation: Avoid LFENCE in FILL_RETURN_BUFFER on
 CPUs that lack it
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Ben Hutchings <ben@decadent.org.uk>, x86@kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        1017425@bugs.debian.org, stable@vger.kernel.org,
        regressions@lists.linux.dev,
        Daniel Sneddon <daniel.sneddon@linux.intel.com>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
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On Fri, Aug 19, 2022 at 2:01 PM Peter Zijlstra <peterz@infradead.org> 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-=C3=89ric