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

[Jan Kiszka]

On 2011-06-21 22:25, Cam Macdonell wrote:
> On Mon, Jun 20, 2011 at 3:05 AM, Jan Kiszka <address@hidden> wrote:
>> On 2011-06-19 22:46, Cam Macdonell wrote:
>>> On Thu, Jun 9, 2011 at 2:39 PM, Jan Kiszka <address@hidden> 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?

It will break the interface how to set up a peer or master ivshmem, from
'-device ivshmem,role=X' to '-device ivshmem-X' (with the role property
removed).

Jan

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