From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55988) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fQC2E-0006kk-Iv for qemu-devel@nongnu.org; Tue, 05 Jun 2018 09:30:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fQC2A-0003OF-JO for qemu-devel@nongnu.org; Tue, 05 Jun 2018 09:30:02 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:50126 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 1fQC2A-0003O5-Ds for qemu-devel@nongnu.org; Tue, 05 Jun 2018 09:29:58 -0400 Date: Tue, 5 Jun 2018 14:29:48 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20180605132948.GH32286@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> <53c37321-52d2-732c-19fb-8f6a9542c714@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <53c37321-52d2-732c-19fb-8f6a9542c714@gmail.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: Marcel Apfelbaum Cc: Gerd Hoffmann , pbonzini@redhat.com, rth@twiddle.net, qemu-devel@nongnu.org, ehabkost@redhat.com, "Michael S. Tsirkin" On Tue, Jun 05, 2018 at 04:20:46PM +0300, Marcel Apfelbaum wrote: >=20 >=20 > On 06/05/2018 11:43 AM, Daniel P. Berrang=C3=A9 wrote: > > On Tue, Jun 05, 2018 at 09:27:46AM +0200, Gerd Hoffmann wrote: > > > Hi, > > >=20 > > > > > Add to that shortcuts like -cdrom > > > > > stop working, > > > > Maybe is fixable. > > > Already fixed for ages. > > >=20 > > > > I see marking Q35 as the default machine a first step. > > > Maybe the better option is to go the arm route: Just don't define = a > > > default, so users have to specify pc or q35. That will make them n= otice > > > there is a world beside 'pc', and we also avoid breaking things > > > silently. >=20 > It can work, sure. And we can add user hints: "Use q35 for ...., select= pc > if..." >=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 > Can't libvirt preserve 'pc' for existing domains, while defaulting to q= 35 > the creation of new domains ? This way it aligns with Gerd's proposal o= f no > default x86 machine. Existing domains wasn't the case I was concerned about. Consider you have libvirt 4.4.0 intsalled and you deploy a *new* domain from a prebuilt disk image "foo". Now update to a libvirt or QEMU which changes to q35 and try to deploy another new domain from the same prebuilt disk image "foo". It may not work now if that disk image doesn't support q35. That would be a regression from the user's POV, whether libvirt or qemu has changed the default. 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 :|