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SubjectRe: [BUG] x86 kenel won't boot under Virtual PC
Ingo Molnar wrote:
>
> yes. X86_P6_NOPS is a totally insignificant optimization and if it makes
> _any_ CPU not boot (be that virtual or real), then it's frankly not
> worth it.
>
> David, exactly how does the kernel fail to boot with latest -git?
> (v2.6.27-rc5-313-g64f996f or later) Does detect_nopl() run? It really
> should, and it should detect the non-working instructions.
>

Okay, a few things here...

1. First, I wrote up a patch yesterday to update the CONFIG_X86_GENERIC
description and to make it "default y". It is currently on
x86/defconfig, but I think it should be promoted to mainline immediately.

2. X86_P6_NOPS is not the only source of static NOPLs. If gcc is set to
optimize for specific architectures, then gcc/binutils will generate
static NOPLs. The only way we can prevent that is by not using specific
-march options, as far as I can tell.

3. I'm not positive that CONFIG_X86_GENERIC currently avoid all cases of
(2), but it obviously should. I will verify that today and add a
followup patch to the Makefiles if necessary.

Given all of this, I really think that putting this on
CONFIG_X86_GENERIC, *AND* making CONFIG_X86_GENERIC the default is the
right choice.

-hpa



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