linux-kernel - Re: [PATCH v3] x86: add NOPL and CMOV emulation

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Message-Id: <202106272120.07140.linux@zary.sk>
Date:   Sun, 27 Jun 2021 21:20:06 +0200
From:   Ondrej Zary <linux@...y.sk>
To:     Marcos Del Sol Vives <marcos@...a.pet>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] x86: add NOPL and CMOV emulation

On Saturday 26 June 2021 15:03:14 Marcos Del Sol Vives wrote:
> NOPL and CMOV are a set of instructions that were introduced to the
> x86 architecture with the i686 ISA in 1995, first implemented in the
> Intel Pentium Pro and Pentium II processors.
> 
> While virtually all desktop and server systems are modern enough to
> support these instructions, in the embedded market things are a little
> bit different: DM&P is still manufacturing their i586-only Vortex86
> SoCs, and many embedded devices still in use are stuck on legacy SoCs
> that either are i586-only (AMD Elan, AMD Geode GX1) or implement i686
> but lack the NOPL instructions (Transmeta devices, AMD Geode LX).
> 
> This is a problem because most modern Linux distributions, such as
> Debian and all its derivatives, have started compiling targeting i686,
> leaving old embedded devices using binary distributions without an
> easy upgrade path.
> 
> This ultimately results in most of these embedded devices running
> years old, insecure and obsolete installations, and this itself can be
> seen on the DM&P's own supported OS page where the newest supported
> desktop Linux distro is Ubuntu 18.04, already three years old.
> 
> The emulation of these instructions thus allow upgrading to newer
> distributions just by replacing the kernel, keeping all precompiled
> binaries intact.

Great, this would allow me to update my old Pentium 133 box from unsupported Debian 8 to 9, 10 and even the upcoming 11.

-- 
Ondrej Zary