linux-kernel - Re: KVM build warnings

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Message-Id: <20110530191426.336d23f4.yoshikawa.takuya@oss.ntt.co.jp>
Date:	Mon, 30 May 2011 19:14:26 +0900
From:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
To:	Borislav Petkov <bp@...en8.de>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	takuya.yoshikawa@...il.com
Subject: Re: KVM build warnings

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.

  Takuya
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