linux-kernel - Re: [PATCH 2/2] x86, pti: fix boot warning from Global-bit setting

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Date:   Fri, 20 Apr 2018 12:16:46 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, mceier@...il.com,
        aaro.koskinen@...ia.com, aarcange@...hat.com, luto@...nel.org,
        arjan@...ux.intel.com, bp@...en8.de, dan.j.williams@...el.com,
        dwmw2@...radead.org, gregkh@...uxfoundation.org, hughd@...gle.com,
        jpoimboe@...hat.com, jgross@...e.com, keescook@...gle.com,
        torvalds@...ux-foundation.org, namit@...are.com,
        peterz@...radead.org
Subject: Re: [PATCH 2/2] x86, pti: fix boot warning from Global-bit setting

On Tue, 17 Apr 2018, Dave Hansen wrote:

> 
> These are _very_ lightly tested.  I'm throwing them out there for
> folks are looking for a fix.
> 
> ---
> 
> From: Dave Hansen <dave.hansen@...ux.intel.com>
> 
> pageattr.c is not friendly when it encounters empty (zero) PTEs.  The
> kernel linear map is exempt from these checks, but kernel text is not.
> This patch adds the code to also exempt kernel text from these checks.

Bah. Changelogs should tell the WHY and not the WHAT

> The proximate cause of these warnings was most likely an __init area
> that spanned a 2MB page boundary that resulted in a "zero" PMD.

This doesn't make any sense at all. 

Thanks,

	tglx