From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: Configuration vs. compat hints [was Re: [Qemu-devel] [PATCHv3 03/13] qemu: add routines to manage PCI capabilities] Date: Mon, 15 Jun 2009 07:48:22 -0500 Message-ID: <4A364316.5070402@codemonkey.ws> References: <20090610145540.GI19375@poweredge.glommer> <20090610150129.GC28601@redhat.com> <200906101624.30659.paul@codesourcery.com> <20090610174301.GC7416@shareable.org> <20090610182227.GN28601@redhat.com> <20090610192702.GH7416@shareable.org> <1244796209.16425.20.camel@blaa> <4A326C7E.3020309@codemonkey.ws> <1244822007.30522.68.camel@blaa> <4A327E87.6080005@codemonkey.ws> <1244825333.26769.20.camel@blaa> <4A34ADA9.80709@redhat.com> <1245056955.6891.33.camel@blaa> <4A36314A.8040206@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Mark McLoughlin , Jamie Lokier , "Michael S. Tsirkin" , Carsten Otte , kvm@vger.kernel.org, Glauber Costa , Rusty Russell , qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, Blue Swirl , Christian Borntraeger , Paul Brook To: Avi Kivity Return-path: Received: from mail-qy0-f173.google.com ([209.85.221.173]:53781 "EHLO mail-qy0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751974AbZFOMs0 (ORCPT ); Mon, 15 Jun 2009 08:48:26 -0400 Received: by qyk3 with SMTP id 3so232045qyk.33 for ; Mon, 15 Jun 2009 05:48:26 -0700 (PDT) In-Reply-To: <4A36314A.8040206@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > On 06/15/2009 12:09 PM, Mark McLoughlin wrote: >>>>> I think the point is that you don't need version numbers if you >>>>> have a >>>>> proper device tree. >>>>> >>>>> >>>> How do you add a new attribute to the device tree and, when a supplied >>>> device tree lacking said attribute, distinguish between a device tree >>>> from an old version of qemu (i.e. use the old default) and a partial >>>> device tree from the VM manager (i.e. use the new default) ? >>>> >>>> >>> -baseline 0.10 >>> >> >> That's a version number :-) >> >> (I was responding to Anthony's "you don't need a version number") >> > > If you want to prevent incompatibilities, you need to make everything > new (potentially including bugfixes) non-default. Eventually the > default configuration becomes increasingly unusable and you need a new > baseline. You must still be able to fall back to the old baseline for > older guests. I don't think games with configuration files can hide > that. -M pc1 -M pc2 etc. This is pretty easy to maintain with config files. Regards, Anthony Liguori From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MGBc2-0005wK-7f for qemu-devel@nongnu.org; Mon, 15 Jun 2009 08:48:34 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MGBbw-0005s0-6O for qemu-devel@nongnu.org; Mon, 15 Jun 2009 08:48:32 -0400 Received: from [199.232.76.173] (port=46167 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MGBbv-0005rf-Q6 for qemu-devel@nongnu.org; Mon, 15 Jun 2009 08:48:27 -0400 Received: from qw-out-1920.google.com ([74.125.92.150]:13784) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MGBbv-0005KA-DZ for qemu-devel@nongnu.org; Mon, 15 Jun 2009 08:48:27 -0400 Received: by qw-out-1920.google.com with SMTP id 4so1771582qwk.4 for ; Mon, 15 Jun 2009 05:48:26 -0700 (PDT) Message-ID: <4A364316.5070402@codemonkey.ws> Date: Mon, 15 Jun 2009 07:48:22 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: Configuration vs. compat hints [was Re: [Qemu-devel] [PATCHv3 03/13] qemu: add routines to manage PCI capabilities] References: <20090610145540.GI19375@poweredge.glommer> <20090610150129.GC28601@redhat.com> <200906101624.30659.paul@codesourcery.com> <20090610174301.GC7416@shareable.org> <20090610182227.GN28601@redhat.com> <20090610192702.GH7416@shareable.org> <1244796209.16425.20.camel@blaa> <4A326C7E.3020309@codemonkey.ws> <1244822007.30522.68.camel@blaa> <4A327E87.6080005@codemonkey.ws> <1244825333.26769.20.camel@blaa> <4A34ADA9.80709@redhat.com> <1245056955.6891.33.camel@blaa> <4A36314A.8040206@redhat.com> In-Reply-To: <4A36314A.8040206@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: Carsten Otte , Rusty Russell , kvm@vger.kernel.org, Mark McLoughlin , Glauber Costa , "Michael S. Tsirkin" , qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, Blue Swirl , Christian Borntraeger , Paul Brook Avi Kivity wrote: > On 06/15/2009 12:09 PM, Mark McLoughlin wrote: >>>>> I think the point is that you don't need version numbers if you >>>>> have a >>>>> proper device tree. >>>>> >>>>> >>>> How do you add a new attribute to the device tree and, when a supplied >>>> device tree lacking said attribute, distinguish between a device tree >>>> from an old version of qemu (i.e. use the old default) and a partial >>>> device tree from the VM manager (i.e. use the new default) ? >>>> >>>> >>> -baseline 0.10 >>> >> >> That's a version number :-) >> >> (I was responding to Anthony's "you don't need a version number") >> > > If you want to prevent incompatibilities, you need to make everything > new (potentially including bugfixes) non-default. Eventually the > default configuration becomes increasingly unusable and you need a new > baseline. You must still be able to fall back to the old baseline for > older guests. I don't think games with configuration files can hide > that. -M pc1 -M pc2 etc. This is pretty easy to maintain with config files. Regards, Anthony Liguori