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

From: H. Peter Anvin
Date: Tue Jul 22 2008 - 20:33:14 EST

Jeff Garzik wrote:

I am pretty sure CONFIG_X86_GENERIC doesn't disable CMOV, and since CMOV is a separate CPUID flag it's all good (if the chip doesn't have it, it'll trap.)

It's generally more an issue of making sure the compiler is not instructed to issue cmov (-march=i686).

You're missing the point, though. The issues at hand are:

- Luis' distributor is compiling kernels without CONFIG_X86_GENERIC.
- VIA has CPUs with family == 6 that don't support long NOPs.
- There is no CPUID flag for long NOPs.

So the VIA chips in question sail through the system that's supposed to warn that the kernel is using an unsupported feature and have a hard crash, instead.

A lot of virtualizers do the same thing, since they don't use proper vendor IDs and instead mimic real chips, sigh.

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