[Qemu-devel] Re: [PATCH v2 1/2] hw/arm_sysctl.c: Add the Versatile Express system registers

[Peter Maydell]

On 5 March 2011 17:04, Paolo Bonzini <address@hidden> wrote:
> On 03/05/2011 05:50 PM, Peter Maydell wrote:
>>
>> (1) Is there supposed to be any kind of guard on trying to
>> do a vmsave on a system with devices that don't implement
>> save/load? IME it just produces a snapshot which doesn't
>> work when you reload it...
>
> I think you're right, devices currently have to call
> register_device_unmigratable manually.

That's a shame, since there are still plenty of devices in
the tree which just don't implement save/restore. It would
be nice if trying to vmsave one of those boards produced
an error listing all the devices that would need support
added for it to work.

> I guess you could add support to
> qdev, so that qdev-ified devices could specify a special "forbid migration"
> value for the vmsd field.

> Alternatively, you could have NULL mean "forbid migration" and a special
> value for "do not save anything, it will just work".

You definitely want the default to be "save/load support status
unknown, forbid migration" (whether the device is qdev or not),
and then you can whitelist devices where somebody's actually
checked the code and confirmed that saving nothing is OK.

-- PMM