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Date: Sun, 30 Jul 2006 21:11:07 +0300
From: Avi Kivity <avi@argo.co.il>
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To: Andi Kleen <ak@suse.de>
CC: Jiri Slaby <jirislaby@gmail.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: FP in kernelspace
References: <p73u04z2dzu.fsf@verdi.suse.de>
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Andi Kleen wrote:
>
> Avi Kivity <avi@argo.co.il> writes:
> >
> > It's also broken for x86-64, which uses sse for floating point, not
> > the x87 fpu.
>
> Sorry, that doesn't make sense.
>

 > > kernel_fpu_begin();
 > > c = d * 3.14;
 > > kernel_fpu_end();

Cannot work on x86-64, even disregarding fp exceptions, because 
kernel_fpu_begin() doesn't save the sse state which is used by fp math.

No?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.