From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58942) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fUxjp-0001uW-BM for qemu-devel@nongnu.org; Mon, 18 Jun 2018 13:14:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fUxjl-0006kW-9o for qemu-devel@nongnu.org; Mon, 18 Jun 2018 13:14:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37928) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fUxjl-0006k6-0q for qemu-devel@nongnu.org; Mon, 18 Jun 2018 13:14:41 -0400 Date: Mon, 18 Jun 2018 14:14:31 -0300 From: Eduardo Habkost Message-ID: <20180618171431.GK7451@localhost.localdomain> 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> <20180613180508.GD24764@localhost.localdomain> <20180614080948.GF6355@redhat.com> <20180615025056.GB7451@localhost.localdomain> <20180615090314.GA31552@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20180615090314.GA31552@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH RFC] hw/pc: set q35 as the default x86 machine List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Cc: Gerd Hoffmann , "Michael S. Tsirkin" , qemu-devel@nongnu.org, pbonzini@redhat.com, rth@twiddle.net, libvir-list@redhat.com On Fri, Jun 15, 2018 at 10:03:14AM +0100, Daniel P. Berrang=E9 wrote: > On Thu, Jun 14, 2018 at 11:50:56PM -0300, Eduardo Habkost wrote: > > On Thu, Jun 14, 2018 at 09:09:48AM +0100, Daniel P. Berrang=E9 wrote: > > > On Wed, Jun 13, 2018 at 03:05:08PM -0300, Eduardo Habkost wrote: > > > > Getting back to this discussion: > > > >=20 > > > > On Tue, Jun 05, 2018 at 09:43:00AM +0100, Daniel P. Berrang=E9 wr= ote: > > > > > On Tue, Jun 05, 2018 at 09:27:46AM +0200, Gerd Hoffmann wrote: > > > > > > Hi, > > > > > >=20 > > > > > > > > Add to that shortcuts like -cdrom > > > > > > > > stop working, > > > > > > >=20 > > > > > > > Maybe is fixable. > > > > > >=20 > > > > > > Already fixed for ages. > > > > > >=20 > > > > > > > I see marking Q35 as the default machine a first step. > > > > > >=20 > > > > > > Maybe the better option is to go the arm route: Just don't d= efine a > > > > > > default, so users have to specify pc or q35. That will make = them notice > > > > > > there is a world beside 'pc', and we also avoid breaking thin= gs > > > > > > silently. > > > > >=20 > > > > > If QEMU removes the default, then libvirt will have to hardcode > > > > > 'pc' as the default to maintain back compatibility, so I don't > > > > > think that ends up as a net win > > > >=20 > > > > I believe there's consensus that applications blindly relying on > > > > the default machine-type when creating a domain is a bad idea. > > > >=20 > > > > That said, can we deprecate this feature in libvirt, encourage > > > > applications to always specify an explicit machine-type, thus > > > > making it possible to deprecate the i440fx machine-types one day? > > >=20 > > > Well from libvirt's POV this scenario arrives if a mgmt app simply = omits > > > the relevant element/attribute from the XML config. Deprecating som= ething > > > implies that in future we'd drop support for it, but we're never go= ing > > > to make this mandatory in libvirt as that would be a regression in > > > behaviour from libvirt's POV. So I don't think it is something we w= ould > > > deprecate. > >=20 > > Does libvirt really have an option, here? I'm sure that sooner > > or later somebody will distribute QEMU binaries without "pc". >=20 > Sure if someone does that, we'll have no choice, but as long as 'pc' is > shipped we shouldn't gratuitously break apps by changing the default. Right. I just want to make sure "omitting the machine-type may stop working in the future" is documented somehow. --=20 Eduardo