Re: Qemu-KVM Livate Migration 0.12.2 -> 0.12.3/4 broken?

[Juan Quintela <quintela@redhat.com>]

Jan Kiszka <jan.kiszka@web.de> wrote:
> Juan Quintela wrote:
>> Lack of "proper" subsections.  IDE is something like:
>> 
>> const VMStateDescription vmstate_ide_drive = {
>>     .version_id = 4,
>> ....
>> }
>> 
>> static const VMStateDescription vmstate_bmdma = {
>>     .name = "ide bmdma",
>>     .version_id = 4,
>> ...
>> }
>> 
>> const VMStateDescription vmstate_ide_pci = {
>>     .name = "ide",
>>     .version_id = 4,
>> ....
>>         VMSTATE_STRUCT_ARRAY(bmdma, PCIIDEState, 2, 0,
>>                      vmstate_bmdma, BMDMAState),
>>         VMSTATE_IDE_DRIVES(bus[0].ifs, PCIIDEState),
>>         VMSTATE_IDE_DRIVES(bus[1].ifs, PCIIDEState),
>> ....
>> }
>> 
>> 
>> Notice that everything is at version 4.  It used to be everything at
>> version 3.  Now the problem is that when migrating from v3 -> v4.  We
>> put in one place v3, But we only have a version number at the toplevel,
>> rest of "subsections" don't sent a version number.  There is no way to
>> fix it in the general case.  We can hack something around for ide, but
>> that will just be a hack, or we can backport marcelo change and port it
>> as a proper subsection (that is my plan).  I expect to have time at the
>> end of next time to work on this.
>
> BTW, the IDE subsystem is yet lacking a proper vmstate section split-up
> along qdev boundaries (ie. vmstate_ide_pci should not contain drive
> structures). Do you plan to address this as well?

Not for Friday, and not for 0.12.

That is 0.13 material, and have to get one agreement on how to go.
We can go for:
- good structure
- backward compatibility

I can't see any good way to get both at this stage :(  But I am open to
sugestions.

Later, Juan.

PD. BTW, very good work with printing the vmstate, that was one of the goals
    when we added it, that was the next step after porting everything to
    vmstate :)