From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49759) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z5GDC-0008FS-Tk for qemu-devel@nongnu.org; Wed, 17 Jun 2015 12:29:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z5GD7-0004d8-UV for qemu-devel@nongnu.org; Wed, 17 Jun 2015 12:29:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33770) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z5GD7-0004bS-Oj for qemu-devel@nongnu.org; Wed, 17 Jun 2015 12:29:09 -0400 Date: Wed, 17 Jun 2015 18:29:05 +0200 From: "Michael S. Tsirkin" Message-ID: <20150617182322-mutt-send-email-mst@redhat.com> References: <1434117956-4929-1-git-send-email-dslutz@verizon.com> <20150617160826-mutt-send-email-mst@redhat.com> <558180A0.8040708@redhat.com> <20150617161716-mutt-send-email-mst@redhat.com> <558183C1.3010402@redhat.com> <20150617162836-mutt-send-email-mst@redhat.com> <55819D8F.3000003@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55819D8F.3000003@redhat.com> Subject: Re: [Qemu-devel] [PATCH v7 0/9] Add limited support of VMware's hyper-call rpc List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Markus Armbruster , qemu-devel@nongnu.org, Don Slutz , Luiz Capitulino , Anthony Liguori , Andreas =?iso-8859-1?Q?F=E4rber?= , Richard Henderson On Wed, Jun 17, 2015 at 06:17:19PM +0200, Paolo Bonzini wrote: > > > On 17/06/2015 16:29, Michael S. Tsirkin wrote: > > On Wed, Jun 17, 2015 at 04:27:13PM +0200, Paolo Bonzini wrote: > >> > >> > >> On 17/06/2015 16:18, Michael S. Tsirkin wrote: > >>>>> Yes, that's what was done for parallel and pcspk as well. There's no > >>>>> infrastructure to avoid it. > >>>>> > >>>>> Paolo > >>> How do you mean? We have multiple ways to keep devices > >>> compatible with old versions. > >>> Set a new property to skip the extra stuff. > >> > >> Not if the device didn't have a vmstate at all, unfortunately. > > > > Skip creating the device completely for old machine types. > > Which device? The vmstate is tied to the same device that has always > been created. Just disable the new functionality. Make it behave in a compatible way. > we enable this thing by default (why do we?) Sigh. There is a very simple way to add a device in qemu: let user request it with -device. If one does this, one gets to maintain the resulting mess without bothering with pc maintainers in any way. But of course, everyone implementing a new feature feels it's such a great thing, and completel zero risk, it must be part of the default machine. Guess what, one then gets to bother with versioning from day 0. > >>> this seems like a big deal ... > >> > >> The PC speaker device is also enabled by default. > > > > This is historical, isn't it? > > Yes, but it has broken 2.3->2.2 migration. > > Let's just stop fighting windmills. > > Paolo I don't see what you are saying. Suddenly guest visible changes within a machine type are ok? So we have a bug, need to fix it, preferably before piling up more features. The best way imho is for 2.4 to avoid this device unless requested explicitly. -- MST