From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=32900 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PSU3W-0007xk-Lk for qemu-devel@nongnu.org; Tue, 14 Dec 2010 07:32:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PSU3V-00019B-C6 for qemu-devel@nongnu.org; Tue, 14 Dec 2010 07:32:34 -0500 Received: from mx1.redhat.com ([209.132.183.28]:26780) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PSU3V-00018d-0k for qemu-devel@nongnu.org; Tue, 14 Dec 2010 07:32:33 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id oBECWVKX029252 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 14 Dec 2010 07:32:32 -0500 Date: Tue, 14 Dec 2010 14:32:09 +0200 From: "Michael S. Tsirkin" Message-ID: <20101214123209.GC19950@redhat.com> References: <1292262202.2857.114.camel@x201> <20101213175010.GD7182@redhat.com> <1292263244.2857.120.camel@x201> <20101213185437.GB9554@redhat.com> <1292266756.2857.122.camel@x201> <20101213190619.GD9554@redhat.com> <1292267708.2857.123.camel@x201> <20101214044342.GE9554@redhat.com> <1292302848.2857.148.camel@x201> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1292302848.2857.148.camel@x201> Subject: [Qemu-devel] Re: [PATCH] rtl8139: IO memory is not part of vmstate List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex Williamson Cc: qemu-devel@nongnu.org, quintela@redhat.com On Mon, Dec 13, 2010 at 10:00:48PM -0700, Alex Williamson wrote: > On Tue, 2010-12-14 at 06:43 +0200, Michael S. Tsirkin wrote: > > On Mon, Dec 13, 2010 at 12:15:08PM -0700, Alex Williamson wrote: > > > On Mon, 2010-12-13 at 21:06 +0200, Michael S. Tsirkin wrote: > > > > On Mon, Dec 13, 2010 at 11:59:16AM -0700, Alex Williamson wrote: > > > > > On Mon, 2010-12-13 at 20:54 +0200, Michael S. Tsirkin wrote: > > > > > > On Mon, Dec 13, 2010 at 11:00:44AM -0700, Alex Williamson wrote: > > > > > > > On Mon, 2010-12-13 at 19:50 +0200, Michael S. Tsirkin wrote: > > > > > > > > On Mon, Dec 13, 2010 at 10:43:22AM -0700, Alex Williamson wrote: > > > > > > > > > So, unfortunately, I stand by my original patch. > > > > > > > > > > > > > > > > What about the one that put -1 in saved index for a hotplugged device? > > > > > > > > > > > > > > There are still examples that don't work even without hotplug (example 2 > > > > > > > and example 3 after the reboot). That hack limits the damage, but still > > > > > > > leaves a latent bug for reboot and doesn't address the non-hotplug > > > > > > > scenarios. So, I don't think it's worthwhile to pursue, and we > > > > > > > shouldn't pretend we can use it to avoid bumping the version_id. > > > > > > > Thanks, > > > > > > > > > > > > > > Alex > > > > > > > > > > > > I guess when we bump it we tell users: migration is completely > > > > > > borken to the old version, don't even try it. > > > > > > > > > > > > Is there a way for libvirt to discover such incompatibilities > > > > > > and avoid the migration? > > > > > > > > > > I don't know if libvirt has a way to query this in advance. If a > > > > > migration is attempted, the target will report: > > > > > > > > > > savevm: unsupported version 5 for '0000:00:03.0/rtl8139' v4 > > > > > > > > > > And the source will continue running. We waste plenty of bits getting > > > > > to that point, > > > > > > > > Yes, this happens after all of memory has been migrated. > > > > > > Better late than never :^\ > > > > One other question: can we do the same by creating a new (empty) > > section? As was discussed in the past this is easier for > > downstreams to cherry-pick. > > The only way I can think to do that would be to have a subsection that > is always included, but saves no data. That would force a failure on > new->old migration, but I don't think it really matches the intended > purpose of subsections and feels like it's adding cruft for no gain. > Maybe I'm missing something. Juan, is there any advantage to trapping > this in a subsection? Thanks, > > Alex Maybe in this particular case the advantage is minimal. But it seems easier to stick to a rule of no more version bumps than argue about each case. -- MST