From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39022) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dVKGF-0004Gb-Aj for qemu-devel@nongnu.org; Wed, 12 Jul 2017 12:13:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dVKGB-0006e2-4g for qemu-devel@nongnu.org; Wed, 12 Jul 2017 12:13:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38510) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dVKGA-0006dK-RB for qemu-devel@nongnu.org; Wed, 12 Jul 2017 12:13:07 -0400 Date: Wed, 12 Jul 2017 17:12:54 +0100 From: "Daniel P. Berrange" Message-ID: <20170712161254.GJ5237@redhat.com> Reply-To: "Daniel P. Berrange" References: <1499847753-8513-1-git-send-email-thuth@redhat.com> <20170712150400.GH5237@redhat.com> <9d51d348-7ad6-a98d-3f6d-89e8af5e3a16@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <9d51d348-7ad6-a98d-3f6d-89e8af5e3a16@redhat.com> Subject: Re: [Qemu-devel] [PATCH v3] hw/i386: Deprecate the machines pc-0.10 to pc-1.2 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth Cc: qemu-devel@nongnu.org, Paolo Bonzini , "Michael S. Tsirkin" , Eduardo Habkost , Marcel Apfelbaum , Igor Mammedov , Gerd Hoffmann , Richard Henderson On Wed, Jul 12, 2017 at 06:00:46PM +0200, Thomas Huth wrote: > On 12.07.2017 17:04, Daniel P. Berrange wrote: > > On Wed, Jul 12, 2017 at 10:22:33AM +0200, Thomas Huth wrote: > >> We don't want to carry along old machine types forever. If we are able to > >> remove the pc machines up to 0.13 one day for example, this would allow > >> us to eventually kill the code for rombar=0 (i.e. where QEMU copies ROM > >> BARs directly to low memory). Everything up to pc-1.2 is also known to > >> have issues with migration. So let's start with a deprecation message > >> for the old machine types so that the (hopefully) few users of these old > >> systems start switching over to newer machine types instead. > > > > I think we must document & agree on our support policy for machine > > types, before we start marking them as deprecated. eg please consider > > the following document before accepting this deprecation patch: > > > > https://lists.gnu.org/archive/html/qemu-devel/2017-07/msg00652.html > > > > Note in that proposal there, I say we do *not* go through trouble of > > explicitly marking machines as deprecated. We just document upfront > > the intended lifecycle and then delete them when it is done. > > > > Just use deprecation warnings for things where there is no predictable > > lifecycle upfront. > > I'm still not 100% sure whether that auto-deprecation of machine types > is such a good idea ... since we might need to maintain machines in > downstream a little bit longer than specified there, it might be better > to rather deprecate them manually from time to time. Downstreams usually maintain custom machine types, so fact that the upstream machine types get deleted is not a problem in itself. The problem comes if followup internal code removal then prevents downstream from creating their custom machine type. I don't think we need tie these issues together. We can remove old machine types, without immediately removing features that our harm creation of downstream machine types. > Anyway, concerning my patch - I'll stop here and won't send another > version. There is too much bikeshed painting going on in this area for > my taste, and since I'm rather a powerpc / s390x guy, I'm also fine if > the pc-0.x machines stay around forever. If somebody else wants to push > this topic instead, feel free to do so. FWIW, I think your proposals have been very useful in general. It has been way overdue to have this kind of discussion. I just want us to focus on defining a policy, rather than making adhoc decisions each time around, as the later is rather unpredictable for users of qemu. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|