From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52379) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dSgfW-0003x6-1Y for qemu-devel@nongnu.org; Wed, 05 Jul 2017 05:32:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dSgfS-0002fF-R2 for qemu-devel@nongnu.org; Wed, 05 Jul 2017 05:32:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42180) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dSgfS-0002eQ-Gp for qemu-devel@nongnu.org; Wed, 05 Jul 2017 05:32:18 -0400 References: <1499237876.3041.4.camel@linux.intel.com> <6ad73f55-c48a-c083-e0ef-b8ac162ec989@redhat.com> From: Marcel Apfelbaum Message-ID: <5233eee1-a017-ccae-3458-762c9e86902c@redhat.com> Date: Wed, 5 Jul 2017 12:32:10 +0300 MIME-Version: 1.0 In-Reply-To: <6ad73f55-c48a-c083-e0ef-b8ac162ec989@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] change x86 default machine type to Q35? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth , Chao Peng , qemu-devel@nongnu.org Cc: "Tian, Kevin" , Laszlo Ersek , "Michael S. Tsirkin" , Paolo Bonzini , Eduardo Habkost 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. The upper layers should manage the defaults by themselves so are not supposed to be affected. > so I think a good point in time to > switch to the q35 machine type would be when we switch to the next major > version number of QEMU, i.e. when we switch to version 3.0. It does seem a good opportunity. If the users > see a new major version number, they might be more willing to accept > such major changes (yeah, I know, we've discussed in the past that > version numbers are just numbers ... but still, there is some kind of > psychological aspect to this, too, I think) > >> - Quality: we may suffer more bugs on Q35 > > I hope that the q35 machine will become mature soon once it has been > made the default machine. > It will certainly help, the question is the cost. Exposing the bugs by having more developers working on Q35 looks more like an opportunity then a "cost" to me. Thanks, Marcel > Thomas >