Messages in this thread | | | Subject | Re: Bug on 2.6.26 - x86 VIA Nehemiah CentaurHauls processor cannot boot | From | Andi Kleen <> | Date | Sat, 26 Jul 2008 20:31:09 +0200 |
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"H. Peter Anvin" <hpa@zytor.com> writes:
> 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.
This was originally supposed to be handled in the early real mode head.S code. That is why I put the CPUID checking code in there to error out early when you can still print to the console using the BIOS functions.
I suspect this regressed when that code was moved to C, because now the C compiler generates CMOV early.
How about always building the real mode C code with -march=i386? It is not performance critical so that is ok.
-Andi
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