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

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Message-ID: <48C55C0A.7070203@zytor.com>
Date:	Mon, 08 Sep 2008 10:08:26 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
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

Linus Torvalds wrote:
> 
> Peter - does gcc actually use NOPL in _32-bit_ code too? It really seems 
> to be a stupid decision to make a binary not run on other CPU's over 
> something as trivial as that. That's something I'd expect out of an Intel 
> compiler just to mess with AMD, not out of gcc.
> 

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.

	-hpa
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