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From: Andi Kleen <andi@firstfloor.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
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        Peter Zijlstra <peterz@infradead.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Byungchul Park <byungchul.park@lge.com>,
        Nilay Vaish <nilayvaish@gmail.com>
Subject: Re: [PATCH 5/8] x86/head: remove useless zeroed word
References: <cover.1471535549.git.jpoimboe@redhat.com>
        <b056855c295bbb3825b97c1e9f7958539a4d6cf2.1471535549.git.jpoimboe@redhat.com>
Date: Mon, 22 Aug 2016 14:48:46 -0700
In-Reply-To: <b056855c295bbb3825b97c1e9f7958539a4d6cf2.1471535549.git.jpoimboe@redhat.com>
        (Josh Poimboeuf's message of "Thu, 18 Aug 2016 10:59:05 -0500")
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Josh Poimboeuf <jpoimboe@redhat.com> writes:

> This zeroed word has no apparent purpose, so remove it.
>
> Brian Gerst says:
>
>   "FYI the word used to be the SS segment selector for the LSS
>   instruction, which isn't needed in 64-bit mode."
>

Seems dangerous. It wouldn't surprise me if some CPUs or x86 emulations
load it anyways and trigger page faults if there is really nothing
there.

-Andi