linux-kernel - Re: [PATCH/RFC] Math-emu kills the kernel on Athlon64 X2

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Message-Id: <20061003092339.999d0011.rdunlap@xenotime.net>
Date:	Tue, 3 Oct 2006 09:23:39 -0700
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Linus Torvalds <torvalds@...l.org>
Cc:	akpm <akpm@...l.org>, Jesper Juhl <jesper.juhl@...il.com>,
	Andi Kleen <ak@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH/RFC] Math-emu kills the kernel on Athlon64 X2

On Tue, 3 Oct 2006 08:10:07 -0700 (PDT) Linus Torvalds wrote:

> 
> 
> On Mon, 2 Oct 2006, Randy Dunlap wrote:
> > 
> > OK, how about something more direct and less obtrusive, like this?
> 
> I think this is fine, but I also think it's a bit hacky.
> 
> Wouldn't it make more sense to make the whole "nofxsr" thing just clear 
> the capability, ie just a diff like the appended...
> 
> Does that work for you? If so, we should _also_ make sure that "no387" 
> calls this function too, so that you don't have to do _both_ no387 and 
> nofxsr, which is clearly silly. Once you do no387, the kernel should do 
> the nofxsr for you, methinks..

Yes, that works.

> ---
> diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
> index 2799baa..7ac3c9e 100644
> --- a/arch/i386/kernel/cpu/common.c
> +++ b/arch/i386/kernel/cpu/common.c
> @@ -185,6 +185,7 @@ static void __cpuinit get_cpu_vendor(str
>  static int __init x86_fxsr_setup(char * s)
>  {
>  	disable_x86_fxsr = 1;
> +	clear_bit(X86_FEATURE_FXSR, boot_cpu_data.x86_capability);
>  	return 1;
>  }
>  __setup("nofxsr", x86_fxsr_setup);

---
~Randy
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