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

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Message-ID: <20080503195448.GE25097@elte.hu>
Date:	Sat, 3 May 2008 21:54:48 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"H. Peter Anvin" <hpa@...or.com>
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...

* 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?)

	Ingo
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