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Date: Mon, 31 May 2010 15:51:32 +0200
From: Borislav Petkov <borislav.petkov@amd.com>
To: Jeff Dike <jdike@addtoit.com>
CC: Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
       Geert Uytterhoeven <geert@linux-m68k.org>,
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	<user-mode-linux-devel@lists.sourceforge.net>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86, hweight: Fix UML boot crash
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From: Jeff Dike <jdike@addtoit.com>
Date: Sun, May 30, 2010 at 10:32:12PM -0400

> On Sun, May 30, 2010 at 09:39:56PM +0200, Borislav Petkov wrote:
> > Which begs the question why _is_ UML sucking in x86 stuff and can anyone
> > provide us with some sensible reasons? Because if there aren't any, it
> > is their includes that should be fixed. Let me see what I can do to
> > redirect hweight stuff properly...
> 
> Generally, UML pulls in the host arch headers because they work.  When
> they are only architecture-dependent (and not, say, depending on the
> host task struct or something), they're fine.
> 
> What's the include path from UML to the x86 hweight stuff?

<arch/x86/include/asm/bitops.h> includes <asm/arch_hweight.h> which are
the optimized variants.

I have a patch which with which UML falls back to the defaults:
http://marc.info/?l=linux-kernel&m=127525067908139&w=2 but hpa's concern
is still valid: UML shouldn't choke on the optimized variants. Anyways,
here's the original commit d61931d89be506372d01a90d1755f6d0a9fafe2d -
you might be able to find something which interferes with UML in there.

Thanks.

-- 
Regards/Gruss,
Boris.

Operating Systems Research Center
Advanced Micro Devices, Inc.