It's just 1 more way linux can be more flexible with hardware.
----- Original Message -----
From: "Gerhard Mack" <gmack@innerfire.net>
To: "Andi Kleen" <ak@muc.de>
Cc: "Tommy Faasen" <tommy@vuurwerk.nl>; <linux-kernel@vger.kernel.org>
Sent: Sunday, October 14, 2001 10:50 PM
Subject: Re: SMP processor rework help needed
> On 14 Oct 2001, Andi Kleen wrote:
>
> > In article <000b01c154ee$1d6a2610$6400a8c0@it0>,
> > "Tommy Faasen" <tommy@vuurwerk.nl> writes:
> > > Hi,
> > > I have this unique situation where cpu 1 has less features (like fxsr)
then
> > > cpu 0.
> >
> > I used to have such an AMP machine too: a dual PII-300 with one Katmai
and one
> > Deschutes. It's technically a violation of the specs; the Intel SMP spec
> > requires that the non boot cpus need to have a superset of the features
> > of the boot CPU. One CPU died, so it is symmetric now.
> >
> > For most capabilities it should already work in 2.4 after hpa's cpu
> > set rewrite, but FXSAVE is unfortunately a bit of a special case because
> > it is used in the scheduler context switch and that is required early
> > in the initialization for SMP bootup and changing it would be very
> > intrusive.
> >
> > In the 2.2 SuSE kernel it was fixed instead by adding a new kernel
> > command line option nofxsave that overrides the FXSAVE bit on the first
> > CPU. That is ok because such setup is very rare and is only generated by
> > people who build their own boxes; and these should also know how to pass
> > kernel command line arguments.
>
> This may sound like a dumb question but wouldn't simply swapping the CPUs
> have the same affect?
>
> Gerhard
>
>
>
> --
> Gerhard Mack
>
> gmack@innerfire.net
>
> <>< As a computer I find your faith in technology amusing.
>
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