linux-kernel - Re: [tip:x86/smap] x86-32: Start out eflags and cr4 clean

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Message-ID: <50B055C8.2030209@zytor.com>
Date:	Fri, 23 Nov 2012 21:06:16 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yuhong Bao <yuhongbao_386@...mail.com>
CC:	"mingo@...nel.org" <mingo@...nel.org>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>
Subject: Re: [tip:x86/smap] x86-32: Start out eflags and cr4 clean

On 11/23/2012 07:49 PM, Yuhong Bao wrote:
>> + * Specifically, cr4 exists if and only if CPUID exists,
>> + * which in turn exists if and only if EFLAGS.ID exists.
> This may be true for *Intel* 486 CPUs as VME was implemented at the same time as CPUID, but I am not sure that it is true for AMD 486 CPUs.
>
> Yuhong Bao 		 	   		

That is the architecture; if you know of a counterexample speak up.  "I 
am not sure" doesn't count.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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