linux-kernel - RE: PROBLEM: compilation issue, inline assembly arch/x86/kvm/emulate.c fails at -O0

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Date:	Thu, 15 Nov 2012 15:09:50 +0000
From:	"Blower, Melanie" <melanie.blower@...el.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"avi@...hat.com" <avi@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: PROBLEM: compilation issue, inline assembly
 arch/x86/kvm/emulate.c fails at -O0

Thanks for your reply. As you agree there is an actual bug in this code, would you kindly be able to tell me when a fix would be available in the Linux trunk?
Thanks and best regards, Melanie Blower

-----Original Message-----
From: H. Peter Anvin [mailto:hpa@...or.com] 
Sent: Wednesday, November 14, 2012 7:14 PM
To: Blower, Melanie
Cc: tglx@...utronix.de; mingo@...hat.com; avi@...hat.com; x86@...nel.org; kvm@...r.kernel.org; linux-kernel@...r.kernel.org
Subject: Re: PROBLEM: compilation issue, inline assembly arch/x86/kvm/emulate.c fails at -O0

On 11/14/2012 11:45 AM, Blower, Melanie wrote:
> [1.] gcc -O0 assembly arch/x86/kvm/emulate.c gets compilation failure 
> -- incorrect register restrictions [2.] Full description of the problem/report:
> I'm trying to compile this file at -O0, but gcc chokes in register allocation at the inline assembly.
>
> In the ordinary Linux build, this file compiles with gcc at -O2, without compilation errors.

Compiling with -O0 is not really expected to work (although -O1 *is*), although what you are reporting is an actual bug ("+a" : "a" should either be "+a" or "=a" : "a").

	-hpa

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