linux-kernel - Re: Bug on 2.6.26 - x86 VIA Nehemiah CentaurHauls processor cannot boot

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Date:	Sat, 26 Jul 2008 20:44:31 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	"Luis R. Rodriguez" <mcgrof@...il.com>,
	linux kernel <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...nel.org>,
	Ivan Seskar <Seskar@...lab.rutgers.edu>,
	jfm3 <jfm3@...lab.rutgers.edu>, Sujith <m.sujith@...il.com>
Subject: Re: Bug on 2.6.26 - x86 VIA Nehemiah CentaurHauls processor cannot boot

"H. Peter Anvin" <hpa@...or.com> writes:
>
> The real mode code *is* compiled with -march=i386, and in the CMOV
> case it will err out with a legible message.
>
> The issue isn't CMOV at all, it's with long NOPs, which don't have a
> CPUID bit -- they're supposed to be supported if family >= 6, but some
> VIA chips violate that condition.

Ah yes I realized that about 1 minute after sending the original mail %)
Sorry for the noise. The only way to handle this is probably to add
special quirks. Should check with Centaur for the exact CPUID signatures
of these CPUs.

Or perhaps just stop using the special nops. It was always unclear
if optimizing nops was really worth it.

-Andi
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