RE: Linux 2.2.11pre2 proposed patch

Jones D (djones2@glam.ac.uk)
Tue, 20 Jul 1999 16:38:50 +0100


> From: Steve Dodd [mailto:dirk@loth.demon.co.uk]
> On Tue, Jul 20, 1999 at 12:41:40PM +0100, BOSZORMENYI Zoltan wrote:
>
> > Well, then will you please remove the f00f bugfix as well
> > and develop a user space tool to switch it on?
> > (The sarcastic taste was intended. :-))
> > IMHO the processor bug workarounds should be in the
> > the kernel.
>
> I personally feel that all the (reasonably small) CPU
> workarounds should be in the kernel, but I seem to have lost that battle.
> The idea that all the distributions are going to include start-up scripts
> which grep /proc/cpuinfo and run set6x86 accordingly is ludicrous wishful
> thinking IMHO.

That would be a really ugly solution.
A somewhat nicer possibility would be to move the stuff into Powertweak
(http://linux.powertweak.com)
I intend to move some of the kernel optimisations there anyway.

> To address your first point, I think the f00f bugfix has to
> be kernel space. It seems to mess with mm things (does this indicate how
> little I understand about it? :)

>From my understanding, the fix involves aligning pages to certain boundaries
or some similar voodoo, so this is done cleaner (and easier) in
kernel-space.

> - do some undocumented magic provided by (or reverse
> engineered from) Cyrix, that seems to modify the CPU behaviour when
> executing the offending instruction, making to do a noop
> afterwards. I don't know of any problems caused by this.

I'm assuming this to be the 'four poke' magic that I found.
Something like this could easily be added to Powertweak, but I've
no 686 to test on.

regards,

Dave.

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