linux-kernel - Re: [PATCH] ftrace: use only 5 byte nops for x86

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Message-ID: <48A6037B.6030202@zytor.com>
Date:	Fri, 15 Aug 2008 15:30:19 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Roland McGrath <roland@...hat.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Gregory Haskins <ghaskins@...ell.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	Clark Williams <williams@...hat.com>, srostedt@...hat.com
Subject: Re: [PATCH] ftrace: use only 5 byte nops for x86

Ingo Molnar wrote:
>>>
>>> TODO: Examine the cpuid to determine the nop to use.
>>>   
>> Don't think that will help in general.  qemu claims its a Pentium II.
> 
> ok. I've applied Steve's patch as it's a good bugfix. The extra paranoia 
> about faulting on 0x90 seems excessive but doesnt hurt ;-)
> 

I think what we need to do is to test the NOPL instruction and create a 
Linux-specific CPUID bit for it.  I'll do that and submit to tip:x86/cpu.

	-hpa
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