linux-kernel - Re: KVM build warnings

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Message-ID: <20110530124600.GB494@eferding.osrc.amd.com>
Date:	Mon, 30 May 2011 14:46:00 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	takuya.yoshikawa@...il.com
Subject: Re: KVM build warnings

On Mon, May 30, 2011 at 07:14:26PM +0900, Takuya Yoshikawa wrote:
> On Mon, 30 May 2011 11:46:04 +0200
> Borislav Petkov <bp@...en8.de> wrote:
> 
> > I get the following
> > 
> > In file included from arch/x86/kvm/mmu.c:2856:
> > arch/x86/kvm/paging_tmpl.h: In function ‘paging32_walk_addr_generic’:
> > arch/x86/kvm/paging_tmpl.h:124: warning: ‘ptep_user’ may be used uninitialized in this function
> > In file included from arch/x86/kvm/mmu.c:2852:
> > arch/x86/kvm/paging_tmpl.h: In function ‘paging64_walk_addr_generic’:
> > arch/x86/kvm/paging_tmpl.h:124: warning: ‘ptep_user’ may be used uninitialized in this function
> > 
> > when building -rc1. It looks like it is caused by
> > 6e2ca7d1802bf8ed9908435e34daa116662e7790 and sticking uninitialized_var() around
> > the ptep_user declaration looks like the easiest solution. But the code should
> > still be audited by someone who's familiar with it whether shutting up the
> > compiler doesn't cause an actual bug.
> 
> Sorry, it is my commit.
> 
> I think the logic guarantees that ptep_user won't be used until it is
> assigned some value.
> 
> It seems to be safe, IIUC.

Ok, thanks for confirming. I'll send a fix soon if no one beats me to
it.

-- 
Regards/Gruss,
Boris.
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