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

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Message-ID: <Pine.LNX.4.64.0610030805490.3952@g5.osdl.org>
Date:	Tue, 3 Oct 2006 08:10:07 -0700 (PDT)
From:	Linus Torvalds <torvalds@...l.org>
To:	Randy Dunlap <rdunlap@...otime.net>
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 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..

		Linus

---
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);
-
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