Re: Bug on 2.6.26 - x86 VIA Nehemiah CentaurHauls processor cannotboot

From: Ingo Molnar
Date: Tue Jul 22 2008 - 09:46:27 EST

* H. Peter Anvin <hpa@xxxxxxxxx> wrote:

> Ingo Molnar wrote:
>>> Not a bug.
>> it would still be nice to get a nice printk and panic during bootup
>> instead of some obscure crash, hm?
> Yes. The fundamental problem is that Centaur has a set of CPUs which
> report family == 6 but don't have the long NOP instructions. We would
> need an exact CPUID criterion for these CPUs in order to be able to
> report it as an error. An alternative would be to attempt trapping in
> the real-mode code (#UD is one of the *very* few CPU exceptions which
> can be reliably captured in real mode on a BIOS system), but doing so
> would probably mean breaking Loadlin at the very least.
> We can't "printk and panic" because we never get that far in the
> kernel proper, for obvious reasons: the code is quite littered with
> these buggers.

hm. How about to default to a safe NOP all the way up to where we can
fix up alternatives and install a different NOP. (which we could also
test first via intentionally jumping on it and catching any exception
via a special exception handler)

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