Re: x86 setup rewrite tree ready for flamage^W review

[Eric W. Biederman]

"H. Peter Anvin" <hpa@xxxxxxxxx> writes:

> Eric W. Biederman wrote:
>> 
>> Even on 386 and 486 class cpus?
>> 
>
> Yes, even on 386 and 486 class CPUs.  I have personally tested this on
> machines as old as the original "double sigma" 386-16.

Ok.  If you have tested on a wide variety of machines then I won't
worry about it.

I guess if a cr0 write has always been synchronizing things should be
a safe practice.  The practical danger is if you write to cr0 and the
pipeline is not flushed and the segment loads might execute as 16bit
mode segment register loads.  I think this is more of a 486 or 586/Pentium
danger actually then a 386 one.

Hmm. I'm not certain about enabling protected mode but enabling paging
at least does appear to be documented to require a jump, before the P6
core.  Which may be why it is recommended for initializing protected
mode.

Eric
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