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

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Date:	Mon, 08 Sep 2008 10:12:12 -0700
From:	"H. Peter Anvin" <hpa@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Andi Kleen <andi@...stfloor.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

H. Peter Anvin wrote:
> 
> Yes, it does:
> 
>   /* We need to decide which NOP sequence to use for 32bit and
>      64bit. When -mtune= is used:
> 
>      1. For PROCESSOR_I386, PROCESSOR_I486, PROCESSOR_PENTIUM and
>      PROCESSOR_GENERIC32, f32_patt will be used.
>      2. For PROCESSOR_PENTIUMPRO, PROCESSOR_PENTIUM4, PROCESSOR_NOCONA,
>      PROCESSOR_CORE, PROCESSOR_CORE2, and PROCESSOR_GENERIC64,
>      alt_long_patt will be used.
>      3. For PROCESSOR_ATHLON, PROCESSOR_K6, PROCESSOR_K8 and
>      PROCESSOR_AMDFAM10, alt_short_patt will be used.
> 
>      When -mtune= isn't used, alt_long_patt will be used if
>      cpu_arch_isa_flags has Cpu686. Otherwise, f32_patt will
>      be used.
> 
> "alt_long_patt" uses NOPL and its variants.
> 

I should point out that the code above is from binutils (gas), not from 
gcc.  It is entirely possible that doing something like
"-mtune=core2 -Wa,-mtune=generic" might actually work, but I have not 
dug through the gcc code proper to figure out if that (a) would work, 
and (b) will remain the case...

	-hpa
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