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

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

On Mon, Jun 20, 2011 at 3:05 AM, Jan Kiszka <jan.kiszka@siemens.com> wrote:
> On 2011-06-19 22:46, Cam Macdonell wrote:
>> 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.
>
> So you are fine with breaking the interface? Everyone else as well? Then
> I'll cook a patch to sort at least this out for 0.15.
>

To be clear, this would break the interface in that a device cannot
specify whether it's migratable via a parameter?

> Jan
>
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>