linux-kernel - Re: [BUG] x86 : i486 reporting to be vulnerable to Meltdown/Spectre_V1/Spectre

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Message-ID: <20180208205240.0c53631f@alans-desktop>
Date:   Thu, 8 Feb 2018 20:52:40 +0000
From:   Alan Cox <gnomes@...rguk.ukuu.org.uk>
To:     tedheadster <tedheadster@...il.com>
Cc:     whiteheadm@....org, David Laight <David.Laight@...lab.com>,
        Arnd Bergmann <arnd@...db.de>,
        Ondrej Zary <linux@...nbow-software.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Jiri Kosina <jikos@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Kees Cook <keescook@...omium.org>,
        Jamie Iles <jamie@...ieiles.com>,
        Eduardo Valentin <eduval@...zon.com>,
        Laura Abbott <labbott@...hat.com>,
        Rik van Riel <riel@...riel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] x86 : i486 reporting to be vulnerable to
 Meltdown/Spectre_V1/Spectre_V2

> > Also worth nothing that the difference between the cpu and memory
> > speeds is much lower - so far fewer instructions could be speculatively
> > executed while waiting a cache miss.

But they also have more instructions that take a lot of clocks and are
easier to stall - eg by doing things like opening and mmapping
a framebuffer and then doing a floating point double store to it
misaligned.

Meltdown we can at least reasonably test but spectre is hard.

Alan