From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49382) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fQEJl-000323-9D for qemu-devel@nongnu.org; Tue, 05 Jun 2018 11:56:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fQEJi-0004el-7u for qemu-devel@nongnu.org; Tue, 05 Jun 2018 11:56:17 -0400 Received: from mail-wr0-x244.google.com ([2a00:1450:400c:c0c::244]:43271) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fQEJi-0004eM-0d for qemu-devel@nongnu.org; Tue, 05 Jun 2018 11:56:14 -0400 Received: by mail-wr0-x244.google.com with SMTP id d2-v6so2975477wrm.10 for ; Tue, 05 Jun 2018 08:56:13 -0700 (PDT) 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> <20180605132948.GH32286@redhat.com> From: Marcel Apfelbaum Message-ID: <0952e6da-a75f-914a-857e-40a6704cad33@gmail.com> Date: Tue, 5 Jun 2018 18:56:09 +0300 MIME-Version: 1.0 In-Reply-To: <20180605132948.GH32286@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US 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: "=?UTF-8?Q?Daniel_P._Berrang=c3=a9?=" Cc: Gerd Hoffmann , pbonzini@redhat.com, rth@twiddle.net, qemu-devel@nongnu.org, ehabkost@redhat.com, "Michael S. Tsirkin" , Laszlo Ersek On 06/05/2018 04:29 PM, Daniel P. Berrangé wrote: > On Tue, Jun 05, 2018 at 04:20:46PM +0300, Marcel Apfelbaum wrote: >> >> On 06/05/2018 11:43 AM, Daniel P. Berrangé wrote: >>> On Tue, Jun 05, 2018 at 09:27:46AM +0200, Gerd Hoffmann wrote: >>>> Hi, >>>> >>>>>> Add to that shortcuts like -cdrom >>>>>> stop working, >>>>> Maybe is fixable. >>>> Already fixed for ages. >>>> >>>>> 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 notice >>>> there is a world beside 'pc', and we also avoid breaking things >>>> silently. >> It can work, sure. And we can add user hints: "Use q35 for ...., select pc >> if..." >> >>> 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 >> Can't libvirt preserve 'pc' for existing domains, while defaulting to q35 >> the creation of new domains ? This way it aligns with Gerd's proposal of 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". Using Laszlo idea (I think):  1) disk image "foo"/no info -> use 'pc' machine.  2) no prebuild image (clean install?) ->  use q35 and add this info to xml In the meantime find a way to embed the supported machine type(s) in the image. (I think the above idea was already discussed, not sure what was the conclusion ) Thanks, Marcel > 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