From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36928) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dTV1B-0002vV-Tp for qemu-devel@nongnu.org; Fri, 07 Jul 2017 11:18:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dTV17-0003Mt-Tq for qemu-devel@nongnu.org; Fri, 07 Jul 2017 11:18:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37614) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dTV17-0003MS-Ml for qemu-devel@nongnu.org; Fri, 07 Jul 2017 11:18:01 -0400 Date: Fri, 7 Jul 2017 18:17:57 +0300 From: "Michael S. Tsirkin" Message-ID: <20170707181642-mutt-send-email-mst@kernel.org> References: <1499237876.3041.4.camel@linux.intel.com> <6ad73f55-c48a-c083-e0ef-b8ac162ec989@redhat.com> <5233eee1-a017-ccae-3458-762c9e86902c@redhat.com> <20170707133949.GH10776@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170707133949.GH10776@localhost.localdomain> Subject: Re: [Qemu-devel] change x86 default machine type to Q35? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: Marcel Apfelbaum , Thomas Huth , Chao Peng , qemu-devel@nongnu.org, Paolo Bonzini , "Tian, Kevin" , Laszlo Ersek On Fri, Jul 07, 2017 at 10:39:49AM -0300, Eduardo Habkost wrote: > On Wed, Jul 05, 2017 at 12:32:10PM +0300, Marcel Apfelbaum wrote: > > On 05/07/2017 11:14, Thomas Huth wrote: > > > Hi, > > > > > > > Hi, > > > > > On 05.07.2017 08:57, Chao Peng wrote: > > > > > > > > Q35 has been in QEMU for quite a while. Compared to the current default > > > > i440FX, Q35 is probably not that mature and not widely used, however in > > > > some case, Q35 has advantages, for example, in supporting new features. > > > > For instance, we have some features require PCI-e support which is only > > > > available on Q35 and some others need it for EFI support. It is of > > > > course not necessary to change it as the default but if more and more > > > > features have dependencies on Q35 because of requiring much more modern > > > > features then I think it may be worth to do so. In such case we can have > > > > more people to use it and find problems we may know or not know. > > > > > > > Agreed > > > > > Yes, IMHO at one point in time, we should switch the default machine > > > type to q35. > > > > +1 > > > > > The i440FX is really quite old... > > > > > > > There are certainly some drawbacks: > > > > - Compatibility: current code or script may need adjustment > > > > > > That might be a real concern ... > > > > I am not so sure about that. Developers working on upstream projects > > should expect such changes and, for our case, > > modifying the command line by adding "-M pc" should not be a big deal. > > We could print a warning for 1 or 2 releases when users don't add > a explicit "-M pc" or "-M q35" argument to qemu-system-x86_64, > but: > > > > > The upper layers should manage the defaults by themselves so > > are not supposed to be affected. > > But they would be. libvirt uses the default machine-type from > QEMU. How about extending the command for supported machines with a recommended machine type, and teaching libvirt to use that? This way no existing users will be affected. > > > [...] > > -- > Eduardo