linux-kernel - Re: i387/FPU init issues...

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Message-ID: <20080503173402.GA5292@elte.hu>
Date:	Sat, 3 May 2008 19:34:02 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	jamal <hadi@...erus.ca>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Jan Beulich <jbeulich@...ell.com>
Subject: Re: i387/FPU init issues...


* jamal <hadi@...erus.ca> wrote:

> > we have:
> > #define P6_NOP3 ".byte 0x0f,0x1f,0x00\n"
> 
> Dang - I feel i should have saved myself all that git bisecting
> and just posted the oops ;->

your bisection was still very useful - it pinpointed the NOPs - the 
assembly code around the NOP changed so a different length NOP was 
patched in => which did not work on your CPU. So thanks for that! The 
fix is already in x86.git (we'll update the commit log).

> > So the alternatives code applies the wrong nop padding for your CPU. 
> > This was probably introduced with commit 
> > 32c464f5d9701db45bc1673288594e664065388e.
> > 
> > Jan, are you sure that P3 knows the P6 NOPs ? AFAICT its P4, but I 
> > have to dig up the manuals.
> > 
> > Jamal, does the following patch solve your problem ?
> 
> Indeed it does - thanks.

great. So this NOP is indeed not generally known to all "P6 and later" 
CPUs. (the PII)

	Ingo
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