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

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Message-ID: <481CC360.4090506@zytor.com>
Date:	Sat, 03 May 2008 12:56:16 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Mikael Pettersson <mikpe@...uu.se>, jamal <hadi@...erus.ca>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jan Beulich <jbeulich@...ell.com>
Subject: Re: i387/FPU init issues...

Ingo Molnar wrote:
> * H. Peter Anvin <hpa@...or.com> wrote:
> 
>>> This might also be caused by a calibration error. We've seen enough 
>>> of them already.
>> No doubt.  However, there is *something* ugly going on.
> 
> i think a vital clue can be found in the original report:
> 
> |  I am able to reproduce the issue consistently on my laptop using qemu 
> |  (which helped speed debugging a bit). I have also narrowed it down to 
> |  include/asm-x86/i387.h::__save_init_fpu in (32 bit version) - it dies 
> |  somewhere in calling the following line:
> 
> so it might just be incorrect Qemu emulation of a PII's NOP instruction?
> 
> (which btw. probably proves that Linux is the first OS to make 
> intelligent use of those instructions?)
> 

Ah, yes, this is a Qemu bug, then.

And yes, it probably does mean exactly that :)

	-hpa
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