Re: [git pull] x86 fixes

[Arjan van de Ven]

On Mon, 8 Sep 2008 12:30:02 -0700 (PDT)
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> 
> I think there are realistically three classes:
> 
>  - _really_ old, to the point of being totally useless for SMP.
> 
>    This is really just 386 and clones. We _need_ a working WP for a 
>    race-free access_ok(), and we need cmpxchg (and lately xadd).
> 
>    Smaller pains even on UP: bswap doesn't exist. invlpg doesn't
> exist. 

I'd lump all cpus that don't have cpuid in this bucket too (eg half the
486es) simply because not having cpuid is painful in pretty much the
same way.

>  - old. pre-cmov. i486 and pentium, and some clones.

makes sense
 
>  - "modern 32-bit": PPro and better. Can take CMOV, MMX and TSC for 
>    granted.

again makes sense; question is if it makes sense to take PSE and PAE
for granted as well (although PSE we can do runtime I suppose)

> Hmm? Doesn't that sound like a sane model?

it does to me; the only question is if we hit a new bucket with the
various fancy string instructions that are in upcoming models; doing
string/copy operations inlined for those guys will make a fourth bucket.


-- 
If you want to reach me at my work email, use arjan@xxxxxxxxxxxxxxx
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/