From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48791) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bFIek-0005dK-01 for qemu-devel@nongnu.org; Tue, 21 Jun 2016 06:11:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bFIee-0002Ku-Sf for qemu-devel@nongnu.org; Tue, 21 Jun 2016 06:11:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43222) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bFIee-0002Kg-NI for qemu-devel@nongnu.org; Tue, 21 Jun 2016 06:11:36 -0400 References: <1466445226-19808-1-git-send-email-david.vrabel@citrix.com> <57689C0B.2060108@redhat.com> <57690AAA.1060003@citrix.com> From: Paolo Bonzini Message-ID: Date: Tue, 21 Jun 2016 12:11:31 +0200 MIME-Version: 1.0 In-Reply-To: <57690AAA.1060003@citrix.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCHv2] rtl8139: save/load RxMulOk counter (again) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Vrabel , Jason Wang , qemu-devel@nongnu.org On 21/06/2016 11:36, David Vrabel wrote: > On 21/06/16 08:35, Paolo Bonzini wrote: >> >> >> On 21/06/2016 03:44, Jason Wang wrote: >>> >>> >>> On 2016=E5=B9=B406=E6=9C=8821=E6=97=A5 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, mo= ve >>>> 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 see= ms >>> to break this. How about something like: >>> >>> - introduce a subsection for RXOKMul >>> - only migrate it for new version (e.g >=3D 2.7) >=20 > I don't see how this can work with snapshots where the QEMU version tha= t > is going to restore the snapshot is not known in advance. By "new version" he meant the versioned machine types, e.g. pc-i440fx-2.6 and older wouldn't migrate it. >> Introducing a subsection is not really necessary if the value is going >> to be migrated always, and upstream generally does not have "migrate i= t >> only in some version" checks. This is left for downstreams to impleme= nt >> if they care. We just don't have the manpower to ensure that migratio= n >> to older versions works between all releases of QEMU. >=20 > So is this patch acceptable as is? I think it is. Paolo