Messages in this thread | | | Date | Mon, 08 Sep 2008 08:36:48 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [BUG] x86 kenel won't boot under Virtual PC |
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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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