Re: [Qemu-devel] [PATCH] vmstate: Add unmigratable flag

[Cam Macdonell <cam@cs.ualberta.ca>]

On Thu, Jun 9, 2011 at 2:39 PM, Jan Kiszka <jan.kiszka@web.de> wrote:
> On 2011-06-09 22:00, Anthony Liguori wrote:
>> On 06/09/2011 11:44 AM, Jan Kiszka wrote:
>>> A first step towards getting rid of register_device_unmigratable
>>> (ivshmem and lacking vmstate support in virtio are blocking this):
>>>
>>> Allow to register an unmigratable vmstate via qdev, i.e. tag a device
>>> declaratively.
>>
>> I thought part of the problem with this was that for some devices (like
>> ivshmem), whether it can be migrated was dynamic.  It depends on
>> configuration, state, etc.
>
> That only applies to ivshmem (the other user is device assignment which
> is unconditionally unmigratable). And the ivshmem issue could easily be
> solved by defining two devices, ivshmem-peer (or just ivshmem) and
> ivshmem-master, eliminating the need for the role property.
>
> I don't think there will ever be a use case for a "transformer" device
> that becomes unmigratable during runtime (would be a nightmare for
> management apps anyway).
>
> If breaking the user interface of ivshmem for this is OK, I'll post a patch.
>
> Jan
>
>

The migratability of ivshmem is not dynamic in that it doesn't change
at runtime, it's set when the device is created, either role=peer or
role=master is specified.  So iiuc, this could work with ivshmem.

Cam