From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39211) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bFI72-00052O-D8 for qemu-devel@nongnu.org; Tue, 21 Jun 2016 05:36:53 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bFI6y-0003J4-6v for qemu-devel@nongnu.org; Tue, 21 Jun 2016 05:36:51 -0400 Received: from smtp.citrix.com ([66.165.176.89]:47599) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bFI6x-0003If-Vi for qemu-devel@nongnu.org; Tue, 21 Jun 2016 05:36:48 -0400 References: <1466445226-19808-1-git-send-email-david.vrabel@citrix.com> <57689C0B.2060108@redhat.com> From: David Vrabel Message-ID: <57690AAA.1060003@citrix.com> Date: Tue, 21 Jun 2016 10:36:42 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCHv2] rtl8139: save/load RxMulOk counter (again) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , Jason Wang , qemu-devel@nongnu.org On 21/06/16 08:35, Paolo Bonzini wrote: > > > On 21/06/2016 03:44, Jason Wang wrote: >> >> >> On 2016年06月21日 01:53, David Vrabel wrote: >>> Commit 9d29cdeaaca3a0383af764000b71492c4fc67c6e (rtl8139: port >>> TallyCounters to vmstate) introduced in incompatibility in the v4 >>> format as it omitted the RxOkMul counter. >>> >>> There are presumably no users that were impacted by the v4 to v4' >>> breakage, so increase the save version to 5 and re-add the field, >>> keeping backward compatibility with v4'. >>> >>> We can't have a field conditional on the section version in >>> vmstate_tally_counters since this version checked would not be the >>> section version (but the version defined in this structure). So, move >>> all the fields into the main state structure. >>> >>> Signed-off-by: David Vrabel >> >> Migration to old version is important for the user and this patch seems >> to break this. How about something like: >> >> - introduce a subsection for RXOKMul >> - only migrate it for new version (e.g >= 2.7) I don't see how this can work with snapshots where the QEMU version that is going to restore the snapshot is not known in advance. > Introducing a subsection is not really necessary if the value is going > to be migrated always, and upstream generally does not have "migrate it > only in some version" checks. This is left for downstreams to implement > if they care. We just don't have the manpower to ensure that migration > to older versions works between all releases of QEMU. So is this patch acceptable as is? David