[Qemu-devel] Re: Live migration protocol, device features, ABIs and other beasts

[Juan Quintela]

Anthony Liguori <address@hidden> wrote:
> Juan Quintela wrote:
>> Dor Laor <address@hidden> wrote:
>>>     
>>
>> My idea here is that we need to have further use of machine
>> descriptions, once that is done, we need something like a new property
>> for qdev (version?).  Once there, each device could do:
>> - if version != last_version -> die (what it happens now)
>> - do someting sensible, not use the "new" features not existing on that
>>   version
>> - edit the savevm format in an easy way.
>>   
>
> But this would only kick in when using pc-0.11 or something, right?

Yeap.

At this point, pc-0.10 is just:

static QEMUMachine pc_machine_v0_10 = {
    .name = "pc-0.10",
    .desc = "Standard PC, qemu 0.10",
    .init = pc_init_pci,
    .max_cpus = 255,
    .compat_props = (CompatProperty[]) {
        {
            .driver   = "virtio-blk-pci",
            .property = "class",
            .value    = stringify(PCI_CLASS_STORAGE_OTHER),
        },{
            .driver   = "virtio-console-pci",
            .property = "class",
            .value    = stringify(PCI_CLASS_DISPLAY_OTHER),
        },{
            .driver   = "virtio-net-pci",
            .property = "vectors",
            .value    = stringify(0),
        },{
            .driver   = "virtio-blk-pci",
            .property = "vectors",
            .value    = stringify(0),
        },
        { /* end of list */ }
    },

But to really make it work, we need to take a list of each savevm format
change and put it here.  Notice that several changes are needed:
- savevm infrastructure save functions don't know about version id
- devices don't know to "behave" as other version
- other things that I have probably missed

Later, Juan.