From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934078Ab2EXSZi (ORCPT ); Thu, 24 May 2012 14:25:38 -0400 Received: from rcsinet15.oracle.com ([148.87.113.117]:26051 "EHLO rcsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933295Ab2EXSZh (ORCPT ); Thu, 24 May 2012 14:25:37 -0400 Date: Thu, 24 May 2012 14:18:59 -0400 From: Konrad Rzeszutek Wilk To: Stefano Stabellini Cc: "xen-devel@lists.xensource.com" , "linux-kernel@vger.kernel.org" Subject: Re: [Xen-devel] [PATCH 2/4] xen/hvc: Fix error cases around HVM_PARAM_CONSOLE_PFN Message-ID: <20120524181859.GK24934@phenom.dumpdata.com> References: <1337795222-29946-1-git-send-email-konrad.wilk@oracle.com> <1337795222-29946-3-git-send-email-konrad.wilk@oracle.com> <20120524173110.GE24934@phenom.dumpdata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120524173110.GE24934@phenom.dumpdata.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 24, 2012 at 01:31:10PM -0400, Konrad Rzeszutek Wilk wrote: > On Thu, May 24, 2012 at 11:47:12AM +0100, Stefano Stabellini wrote: > > On Wed, 23 May 2012, Konrad Rzeszutek Wilk wrote: > > > We weren't resetting the parameter to be passed in to a > > > known default. Nor were we checking the return value of > > > hvm_get_parameter. > > > > > > CC: stable@kernel.org > > > Signed-off-by: Konrad Rzeszutek Wilk > > > > > > drivers/tty/hvc/hvc_xen.c | 3 ++- > > > 1 files changed, 2 insertions(+), 1 deletions(-) > > > > > > diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c > > > index afc7fc2..3277f0e 100644 > > > --- a/drivers/tty/hvc/hvc_xen.c > > > +++ b/drivers/tty/hvc/hvc_xen.c > > > @@ -219,7 +219,8 @@ static int xen_hvm_console_init(void) > > > if (r < 0) > > > goto err; > > > info->evtchn = v; > > > - hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v); > > > + v = 0; > > > + r = hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v); > > > if (r < 0) > > > goto err; > > > mfn = v; > > > > Is 0 the right default here? > > Maybe something invalid like (~0UL) would be better? > > Perhaps both? The zero is the default non-initialized value. But > -0UL is also a good check value. Somehow I misread your comment as checking the return value, not the default value. I think zero is the right choice as that is the default non-initialized value.