From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36238) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fQEjM-0006Hw-Ad for qemu-devel@nongnu.org; Tue, 05 Jun 2018 12:22:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fQEjL-0002d3-6F for qemu-devel@nongnu.org; Tue, 05 Jun 2018 12:22:44 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:42176 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fQEjL-0002cr-1R for qemu-devel@nongnu.org; Tue, 05 Jun 2018 12:22:43 -0400 Date: Tue, 5 Jun 2018 17:22:39 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20180605162239.GU32286@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20180603092749.107476-1-marcel.apfelbaum@gmail.com> <20180604042928-mutt-send-email-mst@kernel.org> <23040757-b561-e0bf-a41d-38d3c44555ee@gmail.com> <20180605072746.v6xxabsbewiuw7ka@sirius.home.kraxel.org> <20180605084300.GF32286@redhat.com> <20180605130646.GF7451@localhost.localdomain> <20180605131232.GG32286@redhat.com> <20180605191539-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180605191539-mutt-send-email-mst@kernel.org> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] libvirt default machine-type guarantees? (was Re: [PATCH RFC] hw/pc: set q35 as the default x86 machine) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Eduardo Habkost , Gerd Hoffmann , Marcel Apfelbaum , pbonzini@redhat.com, rth@twiddle.net, qemu-devel@nongnu.org, libvir-list@redhat.com On Tue, Jun 05, 2018 at 07:16:56PM +0300, Michael S. Tsirkin wrote: > On Tue, Jun 05, 2018 at 02:12:32PM +0100, Daniel P. Berrang=C3=A9 wrote= : > > eg old OS versions that only work with PC, or more commonly pre-exist= ing > > cloud disk images that were built against PC can't be assumed to just > > work against q35, even if the OS in the image supports it. >=20 > I don't understand that part - when using libvirt domain xml records th= e > machine type used for the install, so it seems that installed images > won't be affected. There's no libvirt XML for distributed cloud images, it is created whenev= er the image is instantiated. Libvirt also doesn't require use of its persis= tent guest feature - it is possible to create so called "transient" guests wit= h libvirt where you just provide an XML doc at each boot up, and libvirt do= es not save this XML between boots. Even if an app is using persistent libvi= rt XML they might not boot the VM on the same host each time, so the previou= s persistent XML may not be available at next boot up. So there's many ways existing deployed guests can be affected by changes in defaults, even whe= n libvirt records info in the XML. Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| |: https://libvirt.org -o- https://fstop138.berrange.c= om :| |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|