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

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Nov 23, 2009 at 03:13:59PM +0100, Juan Quintela wrote:
> Anthony Liguori <anthony@codemonkey.ws> wrote:
> > Juan Quintela wrote:
> >> Dor Laor <dlaor@redhat.com> 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.

Why do you think this the right place for it, I wonder?
This describes the machine, it does not seem to have
anything to do with how we migrate it.

-- 
MST