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From: "H. Peter Anvin" <hpa@zytor.com>
To: "Borislav Petkov" <bp@alien8.de>,
	"Geert Uytterhoeven" <geert@linux-m68k.org>,
	"Borislav Petkov" <borislav.petkov@amd.com>,
	"Toralf Förster" <toralf.foerster@gmx.de>,
	user-mode-linux-devel@lists.sourceforge.net,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86, hweight: Fix UML boot crash
Date: Sun, 30 May 2010 11:36:16 -0700	[thread overview]
Message-ID: <4C02B020.2040103@zytor.com> (raw)
In-Reply-To: <20100530170346.GC1565@liondog.tnic>

On 05/30/2010 10:03 AM, Borislav Petkov wrote:
> Obviously UML cannot stomach callee reg-saving trickery
> introduced with d61931d89be506372d01a90d1755f6d0a9fafe2d (x86:
> Add optimized popcnt variants) and oopses during boot:
> http://marc.info/?l=linux-kernel&m=127522065202435&w=2
> 
> Go ahead and fall back to the software hweight* routines on UML.

I actually don't understand why UML can't stomach that... it would work
exactly the same in userspace as in kernel space.  The only thing that I
can think of is if UML overrides the CFLAGS including the per-file
CFLAGS, but that would seem to cause all kinds of other issues.

I would also be a lot happier if this was handled in
<asm/arch_hweight.h> than in <asm/bitops.h>.  Finally, if UML really
can't handle this, then ARCH_HWEIGHT_CFLAGS should be disabled on UML.

This bothers me, because it really feels like something is fundamentally
broken in UML tryingto track the upstream architecture, and this is just
a bandage.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.


  reply	other threads:[~2010-05-30 18:40 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-05-27 17:44 current git kernel crashes UML system during boot Toralf Förster
2010-05-30 11:39 ` Geert Uytterhoeven
2010-05-30 11:57   ` Geert Uytterhoeven
2010-05-30 15:02     ` Borislav Petkov
2010-05-30 15:18       ` Geert Uytterhoeven
2010-05-30 15:46         ` Borislav Petkov
2010-05-30 15:28       ` Toralf Förster
2010-05-30 17:03         ` [PATCH] x86, hweight: Fix UML boot crash Borislav Petkov
2010-05-30 18:36           ` H. Peter Anvin [this message]
2010-05-30 19:39             ` Borislav Petkov
2010-05-30 20:17               ` Borislav Petkov
2010-05-30 21:09                 ` H. Peter Anvin
2010-06-12 13:34                   ` [uml-devel] " Paolo Giarrusso
2010-06-12 14:18                     ` Borislav Petkov
2010-06-12 16:01                       ` Paolo Giarrusso
2010-06-12 16:34                         ` Borislav Petkov
2010-06-12 18:37                           ` Geert Uytterhoeven
2010-06-13  6:58                             ` Borislav Petkov
2010-05-31 13:55                 ` Toralf Förster
2010-05-31 14:10                   ` Borislav Petkov
2010-05-31 14:36                     ` Toralf Förster
2010-05-31 14:36                       ` Toralf Förster
2010-06-14  9:49                     ` Toralf Förster
2010-06-14  9:49                       ` Toralf Förster
2010-06-14 10:26                       ` [uml-devel] " Paolo Giarrusso
2010-06-14 12:54                         ` Toralf Förster
2010-06-14 13:00                       ` Borislav Petkov
2010-06-14 13:00                         ` Borislav Petkov
2010-06-14 13:44                         ` Toralf Förster
2010-06-14 13:44                           ` Toralf Förster
2010-06-14 14:39                           ` Geert Uytterhoeven
2010-06-14 15:11                             ` Toralf Förster
2010-06-14 15:20                               ` H. Peter Anvin
2010-05-31 14:25                   ` [uml-devel] " Boaz Harrosh
2010-05-31  2:32               ` Jeff Dike
2010-05-31 13:51                 ` Borislav Petkov
2010-05-31 15:56                   ` Jeff Dike
2010-05-31 16:29                     ` Borislav Petkov
     [not found]           ` <tip-cc7f0a7b3004a4ca0bfef0e1ca79f2e0da6ca1b0@git.kernel.org>
2010-06-09 22:43             ` [tip:x86/urgent] " H. Peter Anvin
2010-06-10  5:32               ` Geert Uytterhoeven
2010-06-10  6:26                 ` H. Peter Anvin
2010-06-09  8:04 ` [PATCH resend] um, " Boaz Harrosh
2010-06-09  8:09   ` [uml-devel] " Boaz Harrosh
2010-06-09  8:46     ` Geert Uytterhoeven
2010-06-09  9:08       ` Boaz Harrosh
2010-06-09  9:32       ` Américo Wang
2010-06-09 18:29       ` H. Peter Anvin
2010-06-14 16:08         ` Boaz Harrosh
2010-06-14 16:41           ` H. Peter Anvin
2010-06-14 18:18             ` Boaz Harrosh
2010-06-09 16:39   ` Boaz Harrosh
2010-06-10 23:43   ` [tip:x86/urgent] um, hweight: Fix UML boot crash due to x86 optimized hweight tip-bot for Borislav Petkov

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