linux-kernel - Re: [PATCH 8/8] x86, cleanups: Simplify sync

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Message-ID: <50B7CE4C.80201@linux.intel.com>
Date:	Thu, 29 Nov 2012 13:06:20 -0800
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Mario Gzuk <mariogzuk@...hnikz.de>
Subject: Re: [PATCH 8/8] x86, cleanups: Simplify sync_core() in the case of
 no CPUID

On 11/29/2012 01:13 AM, Borislav Petkov wrote:
> 
> RCX gets correctly cleaned to 0 and *then* we call CPUID.
> 
> And the asm output is the same except that RCX gets correctly cleaned up
> before calling CPUID.
> 
> So what am I missing?
> 

It doesn't matter in that context, as the surrounding MSR references
have barriers, but what I'm refering to is the "memory" barrier.

The value of ECX doesn't matter when EAX=1.

	-hpa


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