Re: Question: Using floating point in the kernel

From: Alan Cox (alan@lxorguk.ukuu.org.uk)
Date: Thu Sep 21 2000 - 18:04:56 EDT

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> On Wed, 20 Sep 2000, Lyle Coder wrote:
> >You cannot use MMX registers in the kernel either, since the kernel doesen't
> >save and restore FX state (fxsave, fxrstor) either (just like
> >(fsave/frstor).
>
> You might want to tell the software RAID maintainers that... RAID5 CRC
> calculations can be done with MMX. (I'm sure they save and restore the
> FPU state, however. Yes, the save/restore cycle is _damned_ expensive.)

The raid5 folks include Ingo who knows precisely what he is doing to get
away with it. For 2.4 its a bit cleaner and there is infrastructure for it

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