From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43024) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dVfum-0001Co-LH for qemu-devel@nongnu.org; Thu, 13 Jul 2017 11:20:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dVfui-0007t7-G5 for qemu-devel@nongnu.org; Thu, 13 Jul 2017 11:20:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50289) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dVfui-0007ss-A1 for qemu-devel@nongnu.org; Thu, 13 Jul 2017 11:20:24 -0400 Date: Thu, 13 Jul 2017 12:20:10 -0300 From: Eduardo Habkost Message-ID: <20170713152010.GS6020@localhost.localdomain> References: <1499847753-8513-1-git-send-email-thuth@redhat.com> <20170713034755-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170713034755-mutt-send-email-mst@kernel.org> 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: "Michael S. Tsirkin" Cc: Thomas Huth , qemu-devel@nongnu.org, Paolo Bonzini , Richard Henderson , Marcel Apfelbaum , Igor Mammedov , Gerd Hoffmann On Thu, Jul 13, 2017 at 04:00:00AM +0300, Michael S. Tsirkin 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. > > > > Signed-off-by: Thomas Huth > > --- > > Note: Even if we mark all these old machines as deprecated, this ofcourse > > doesn't mean that we also have to remove them all at once later when we > > decide to finally really remove some. We could then also start by removing > > 0.10 and 0.11 only, for example (since there should really be no users left > > for these), or only up to 0.13 (to be able to kill rombar=0). > > So I generally think the main issue is that machine types are conflating > two things. One is saying "I want to be able to migrate from/to QEMU X". > Another is saying "I want to look to guests as if I am QEMU X > but I restart gurst on the new QEMU". > > First is generally a superset of the second, but only a subset of > users needs the first. And while there's a very good chance we > are actually pretty close to supporting the second even for very > old machine types, I doubt we are actually able to migrate to/from > these old QEMU versions since it is so hard to test. > > So IMHO, a more significant step with a long term impact would be to > support splitting these things up. I agree they are different things, but do we really have volunteers willing to maintain a machine-type just because of the latter? Setting the same deprecation policy for the two features sounds simpler to me. -- Eduardo