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Date:   Fri, 19 Aug 2022 14:15:46 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Ben Hutchings <ben@decadent.org.uk>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org,
        1017425@bugs.debian.org,
        =?iso-8859-1?Q?Martin-=C9ric?= Racine <martin-eric.racine@iki.fi>,
        stable@vger.kernel.org, regressions@lists.linux.dev,
        Daniel Sneddon <daniel.sneddon@linux.intel.com>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Subject: Re: [PATCH] x86/speculation: Avoid LFENCE in FILL_RETURN_BUFFER on
 CPUs that lack it
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On Fri, Aug 19, 2022 at 01:38:27PM +0200, Ben Hutchings wrote:

> So that puts the whole __FILL_RETURN_BUFFER inside an alternative, and
> we can't have nested alternatives.  That's unfortunate.

Well, both alternatives end with the LFENCE instruction, so I could pull
it out and do two consequtive ALTs, but unrolling the loop for i386 is
a better solution in that the sequence, while larger, removes the need
for the LFENCE.