linux-kernel - Re: [PATCH v2] x86: Early-boot serial I/O support

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Date:	Sun, 11 Jul 2010 01:55:54 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Pekka Enberg <penberg@...helsinki.fi>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH v2] x86: Early-boot serial I/O support

On Sat, Jul 10, 2010 at 02:37:01PM -0700, H. Peter Anvin wrote:
> On 07/10/2010 02:07 PM, Cyrill Gorcunov wrote:
> > On Sat, Jul 10, 2010 at 10:40:20PM +0300, Pekka Enberg wrote:
> >> This patch adds serial I/O support to very early boot printf(). It's useful for
> >> debugging boot code when running Linux under KVM, for example. The actual code
> >>  
> >> +#define cpu_relax()	asm volatile("rep; nop" ::: "memory")
> >> +
> 
> We don't need "memory" here since the early boot environment is
> single-threaded.
> 
> 	-hpa
> 

I rather wonder -- can't we use cpu_relax() from processor.h? Or there
is some type conflicts?

	-- Cyrill
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