linux-kernel - Re: [PATCH 6/6] cpuid neatening.

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Message-ID: <20060725014151.GB91138@muc.de>
Date:	Tue, 25 Jul 2006 03:41:51 +0200
From:	Andi Kleen <ak@....de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Andrew Morton <akpm@...l.org>,
	Keir Fraser <Keir.Fraser@...cam.ac.uk>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Zachary Amsden <zach@...are.com>, Pratap <pratap@...are.com>,
	Chris Wright <chrisw@...s-sol.org>,
	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/6] cpuid neatening.

On Mon, Jul 24, 2006 at 04:58:07PM -0700, H. Peter Anvin wrote:
> Rusty Russell wrote:
> >Roll all the cpuid asm into one __cpuid call.  It's a little neater,
> >and also means only one place to patch for paravirtualization.
> 
> The whole point of those is to avoid the unnecessary write to memory and 
> pick it back up again.  This patch reintroduces that ugliness.

Modern gcc should optimize this when it is inlined. If it didn't
most abstracted C++ code would be quite unhappy.

Also as far as I know there is only a single time critical CPUID
in the code and it ignores all output arguments.

-Andi
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