Re: [Fwd: CPU detection revamp (Request for comments)]

["H. Peter Anvin" <hpa@transmeta.com>]

davej@suse.de wrote:
> 
> Hi hpa,
> 
>  First test, the AMD K6-2.
> 
> Before your patch..
>         cpu family      : 5
>         model           : 8
>         stepping        : 12
> 
> After..
> 
>         cpu family      : 5
>         model           : 8
>         stepping        : 4
> 
> Line 1826 of setup.c
> 
>         c->x86_mask = tfms & 7;
> 
> Should be..
> 
>         c->x86_mask = tfms & 15;
> 
> I think?
> 
> Also, look at the feature flags:
> before:
> flags           : fpu vme de pse tsc msr mce cx8 sep mtrr pge mmx 3dnow
> 
> after:
> features        : fpu vme de pse tsc msr mce cx8 pge mmx syscall 3dnow
> 
> Note, I lost MTRR & sep. This may be related to the stepping bug
> though. I'll recompile a kernel with the &15 fix, and see if that cures
> all.
> 

That is actually correct -- the K6-2 doesn't actually have mtrr and sep,
but has syscall and k6_mtrr instead (the stepping bug causes k6_mtrr not
to show up.)  Part of the bugginess of the old system was using one flag
for multiple purposes.  This was Linux' doing, not AMD's, by the way.

> btw, whilst all this is getting a shakedown, how about renaming
> that 'x86_mask' field to the more obvious 'x86_stepping' ?
> c->x86 would make more sense as c->x86_family too thinking about it.
> 

-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt
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