Re: SMP processor rework help needed

From: Gerhard Mack (
Date: Sun Oct 14 2001 - 15:50:50 EST

On 14 Oct 2001, Andi Kleen wrote:

> In article <000b01c154ee$1d6a2610$6400a8c0@it0>,
> "Tommy Faasen" <> 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 Mack

<>< As a computer I find your faith in technology amusing.

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