linux-kernel - Re: FP in kernelspace

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Message-ID: <44CCF63B.6070906@argo.co.il>
Date:	Sun, 30 Jul 2006 21:11:07 +0300
From:	Avi Kivity <avi@...o.co.il>
To:	Andi Kleen <ak@...e.de>
CC:	Jiri Slaby <jirislaby@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: FP in kernelspace

Andi Kleen wrote:
>
> Avi Kivity <avi@...o.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.

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