linux-kernel - Re: [PATCH] Revert "x86-64, init: Do not set NX bits on non-NX capable hardware"

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Message-ID: <519A691F.9060007@linux.intel.com>
Date:	Mon, 20 May 2013 11:19:11 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Michal Hocko <mhocko@...e.cz>, "H. Peter Anvin" <hpa@...or.com>,
	Fernando Luis Vázquez Cao 
	<fernando@....ntt.co.jp>, "Rafael J. Wysocki" <rjw@...k.pl>,
	the arch/x86 maintainers <x86@...nel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "x86-64, init: Do not set NX bits on non-NX capable
 hardware"

On 05/20/2013 11:18 AM, Linus Torvalds wrote:
> On Mon, May 20, 2013 at 11:13 AM, H. Peter Anvin <hpa@...ux.intel.com> wrote:
>>
>> Indeed.  Looks like we corrupt a random bit in memory on resume.
> 
> Well, in this case, it's probably the DEBUG_PAGEALLOC that Michal has
> enabled, which causes a page fault - and then a triple fault - at
> secondary CPU startup. And the triple fault then results in a reboot.
> Which explains the symptoms he gets.
> 
> Without DEBUG_PAGEALLOC it ends up being "just" a single-bit corruption, yes.
> 

Good, that explains what made it predictable.  Score one for
DEBUG_PAGEALLOC.

	-hpa


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