linux-kernel - RE: [tip:x86/urgent] x86-64, init: Do not set NX bits on non-NX capable hardware

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Date:	Fri, 10 May 2013 22:57:06 -0700
From:	Yuhong Bao <yuhongbao_386@...mail.com>
To:	"mingo@...nel.org" <mingo@...nel.org>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hpa@...or.com" <hpa@...or.com>,
	"fernando@....ntt.co.jp" <fernando@....ntt.co.jp>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...ux.intel.com" <hpa@...ux.intel.com>
Subject: RE: [tip:x86/urgent] x86-64, init:  Do not set NX bits on non-NX
 capable hardware

(resending as plaintext)
> During early init, we would incorrectly set the NX bit even if the NX
> feature was not supported.  Instead, only set this bit if NX is
> actually available and enabled.  We already do very early detection of
> the NX bit to enable it in EFER, this simply extends this detection to
> the early page table mask.
AFAIK the only production x86-64 processor that don't support NX that I know of is the original Nocona D0 stepping.
Must more common are the problem of BIOSes disabling the NX feature.


Yuhong Bao 		 	   		  --
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