From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47659) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZAF8g-0001fJ-H0 for qemu-devel@nongnu.org; Wed, 01 Jul 2015 06:21:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZAF8c-0000MB-I6 for qemu-devel@nongnu.org; Wed, 01 Jul 2015 06:21:10 -0400 Received: from e06smtp10.uk.ibm.com ([195.75.94.106]:37451) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZAF8c-0000Lb-95 for qemu-devel@nongnu.org; Wed, 01 Jul 2015 06:21:06 -0400 Received: from /spool/local by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 1 Jul 2015 11:21:05 +0100 Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by d06dlp01.portsmouth.uk.ibm.com (Postfix) with ESMTP id 0E61417D8063 for ; Wed, 1 Jul 2015 11:22:15 +0100 (BST) Received: from d06av12.portsmouth.uk.ibm.com (d06av12.portsmouth.uk.ibm.com [9.149.37.247]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t61AL2Ai35389612 for ; Wed, 1 Jul 2015 10:21:02 GMT Received: from d06av12.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av12.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t61AL1AI010289 for ; Wed, 1 Jul 2015 04:21:01 -0600 Message-ID: <5593BF0B.1010804@de.ibm.com> Date: Wed, 01 Jul 2015 12:20:59 +0200 From: Christian Borntraeger MIME-Version: 1.0 References: <1435742217-62246-1-git-send-email-borntraeger@de.ibm.com> <87egks19rh.fsf@neno.neno> In-Reply-To: <87egks19rh.fsf@neno.neno> Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1/1] s390x/migration: Introduce 2.4 machine List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: quintela@redhat.com Cc: Alexander Graf , qemu-devel , "Dr. David Alan Gilbert" , Jens Freimann , "Jason J. Herne" , Boris Fiuczynski , Cornelia Huck Am 01.07.2015 um 11:56 schrieb Juan Quintela: > Christian Borntraeger wrote: > > First of all > > Reviewed-by: Juan Quintela > > For the patch. > > But one said that, I don't agree with the commint text. So let's just drop this sentence >> While one can argue that section footer should be enabled >> explicitely for new versions instead of disabled for old ones, And rephrase to " This pinpoints to a problem of s390-ccw-machines: it needs to be versioned to allow common code changes to add compat handling. " Conny, want me to resend or can you fixup the patch description when taking this patch? > > >> The section footer changes commit f68945d42bab ("Add a protective >> section footer") and commit 37fb569c0198 ("Disable section footers >> on older machine types") broke migration for any non-versioned >> machines. > > If broke migration for 2.4 -> 2.3 for machines that don't care about > compatibility. If they care, they are versioned O:-) Right now ppc & > x86. I guess that s390 and arm will follow in due curse. yes. That is what my 2nd sentence says: we are not versioned and that is the main issue to solve. >> this pinpoints to a problem of s390-ccw-machines: it needs to >> be versioned to be compatible with future changes in common >> code data structures such as section footers. > > It is done explicitely the other way around. New way is the default > way. If we did it in a special way in the past, we add a switch. If at > some point we remove the old machine type for any reason, we don't have > to change anything on $latest. > > Basically the idea here is that (until now) only x86 cared about > backwards compatibility, so when a migration changed happened because it > was good for any reason, normal devices do changes, and then x86 try to > fix the pieces after the fact. That is going to continue, just that now > more architectures care, and then we should detect this kind of problems > much earlier. > >> Let's introduce a version scheme for s390-ccw-virtio machines. >> We will use the old s390-ccw-virtio name as alias to the latest >> version as all existing libvirt XML for the ccw type were expanded >> by libvirt to that name. >> >> The only downside of this patch is, that the old alias s390-ccw >> will no longer be available as machines can have only one alias, >> but it should not really matter. > > Should we change to a list? list of aliases? Why not, we would use it.