linux-kernel - Re: [BUG] x86 kenel won't boot under Virtual PC

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Message-ID: <48C54704.2040101@zytor.com>
Date:	Mon, 08 Sep 2008 08:38:44 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux@...dersweb.net, linux-kernel@...r.kernel.org,
	the arch/x86 maintainers <x86@...nel.org>,
	Andi Kleen <andi-suse@...stfloor.org>
Subject: Re: [BUG] x86 kenel won't boot under Virtual PC

Ingo Molnar wrote:
>>
>> I thought you agreed that CPU virtualization can be a problem? That 
>> was the whole excuse for why the dynamic code was changed. Why would 
>> it not be true for the static code?
>>
>> The fact is, if you want to run on a Core2 or other modern CPU, then 
>> "Virtual PC" is apparently buggy in this respect. You worked around it 
>> for the dynamic choice - but that's totally _pointless_ if you then 
>> don't want to work around it for the static one.
> 
> 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.
> 

It almost certainly never gets as far as detect_nopl().

	-hpa
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