From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NCw0J-0003RG-Vz for qemu-devel@nongnu.org; Tue, 24 Nov 2009 09:04:28 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NCw0F-0003No-5L for qemu-devel@nongnu.org; Tue, 24 Nov 2009 09:04:27 -0500 Received: from [199.232.76.173] (port=48071 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NCw0F-0003Nj-2E for qemu-devel@nongnu.org; Tue, 24 Nov 2009 09:04:23 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35752) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NCw0E-0001oR-Ge for qemu-devel@nongnu.org; Tue, 24 Nov 2009 09:04:22 -0500 Received: from int-mx03.intmail.prod.int.phx2.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.16]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id nAOE4L4Z000555 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 24 Nov 2009 09:04:21 -0500 Date: Tue, 24 Nov 2009 16:01:44 +0200 From: "Michael S. Tsirkin" Message-ID: <20091124140144.GK2405@redhat.com> References: <4B0952C9.9010803@redhat.com> <4B0BB7F6.5090103@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4B0BB7F6.5090103@redhat.com> Subject: [Qemu-devel] Re: Live migration protocol, device features, ABIs and other beasts List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Dor Laor Cc: qemu-devel , Juan Quintela On Tue, Nov 24, 2009 at 12:39:50PM +0200, Dor Laor wrote: > On 11/23/2009 02:15 PM, Juan Quintela wrote: >> Dor Laor wrote: >>> > In the last couple of days we discovered some issues regarding stable >>> > ABI and the robustness of the live migration protocol. Let's just jump >>> > right into it, ordered by complexity: >>> > >>> > 1. Control*every* feature exposed to the guest by qemu cmdline: >>> > >>> > While thinking on cross version migration, and reviewing some >>> > patches, I noticed that there are many times that we use feature bits >>> > in order to expose functionality for the guest driver - example: >>> > VIRTIO_BLK_F_BARRIER, but we do not control it from qemu cmdline. >> In my opinion this is madness, qemu command line is already too >> complicated. I agree with anthony to put it in the command line. > > Qemu's cmdline is currently our config file.. Actually there is nothing > wrong with it. Human users shouldn't be interested with these changes > and management software should not have problem manipulating it. > We do need flexibility of controlling our features like any other > software component. > >> I will go further, and think that this kind of issues should be put into >> the machine type. >> >> If you start qemu with -M pc-0.10, it should save the state in a 0.10 >> compatible way (that don't happens at the moment, but it should work >> that way). > > That's the idea - to keep it part of qdev and by default use it with -M. I think we want to keep these things separate: machine description should be for things that are both guest visible and not changeable by guest, so it absolutely must stay constant as long as guest it alive. -- MST