linux-kernel - Re: [PATCH 2.6.24] x86: add sysfs interface for cpuid module

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Date:	Tue, 29 Jan 2008 23:17:23 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	yi.y.yang@...el.com
CC:	tglx@...utronix.de, mingo@...hat.com, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH 2.6.24] x86: add sysfs interface for cpuid module

Yi Yang wrote:
>>
>> It's broken, because it doesn't take into account the fact that Intel 
>> broke CPUID level 4 and made it "repeating" (neither did the cpuid char 
>> device, because it predated the Intel braindamage; I've had a patch for 
>> it privately for a while, but didn't push it upstream because paravirt 
>> broke it royally and I wanted the situation to settle down.)

> level 4 doesn't result in repeating on Intel CPU, cpuid module sets
> file offset to level, so cat /dev/cpu/*/cpuid will run cpuid instruction
> continuously.

The issue is that Intel suddenly made CPUID ECX-sensitive, which there 
is no way to represent.

As far as cat /dev/cpu/*/cpuid, that's a user error.

	-hpa

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