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SubjectRe: Bug on 2.6.26 - x86 VIA Nehemiah CentaurHauls processor cannot boot
H. Peter Anvin wrote:
> Jeff Garzik wrote:
>>>
>>> Thanks for taking a look at this. So well, it would be a
>>> misconfiguration bug by the distribution then to try to support a
>>> generic 686 kernel wihtout GENERIC then.
>>
>> Well, it may be intentional -- some distros simply exclude support for
>> the lower-volume VIA processors, since that might imply building their
>> "generic 686 kernel" sans CMOV and some other instructions, and
>> changing the compiler's instruction scheduling to something less
>> optimal for the majority. :/
>>
>
> X86_GENERIC shouldn't disable CMOV?

I said "generic 686 kernel" not a specific Kconfig option (for reasons
stated below), which is a bit different.


> We're only referring specifically to the family == 6 VIA processors here.

To be specific, I was merely saying that VIA processors where
c->x86_model==6 may lack CMOV.

I have not kept track of what current Kconfig options will set, but in
the past it was quite easy to build a "generic 686 kernel" that required
CMOV and thus excluded these VIA processors.

Distros in the past often wound up intentionally -not- supporting some
of these VIA processors, because they did not want to create a non-CMOV
kernel. (This policy obviously excluded older x86 as well)

If these things have been addressed recently (< 12-18 months) then all good.

Jeff






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