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Re: [Qemu-devel] [PATCHv2] rtl8139: save/load RxMulOk counter (again)

From: Jason Wang
Subject: Re: [Qemu-devel] [PATCHv2] rtl8139: save/load RxMulOk counter (again)
Date: Wed, 22 Jun 2016 13:51:58 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0

On 2016年06月21日 18:11, Paolo Bonzini wrote:
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<address@hidden>
>>>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.
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 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?
I think it is.


Applied to -net.


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