Re: [Qemu-arm] [Qemu-devel] [PATCH for 4.1?] pl330: fix vmstate description

[Damien Hedde]

On 7/24/19 6:38 PM, Dr. David Alan Gilbert wrote:
> * Philippe Mathieu-Daudé (address@hidden) wrote:
>> On 7/24/19 4:35 PM, Damien Hedde wrote:
>>> Fix the pl330 main and queue vmstate description.
>>> There were missing POINTER flags causing crashes during
>>> incoming migration because:
>>> + PL330State chan field is a pointer to an array
>>> + PL330Queue queue field is a pointer to an array
>>>
>>> Also bump corresponding vmsd version numbers.
>>>
>>> Signed-off-by: Damien Hedde <address@hidden>
>>> ---
>>>
>>> I found this while working on reset with xilinx-zynq machine.
>>>
>>> I'm not sure what's the vmsd version policy in such cases (for
>>> backward compatibility). I've simply bumped them since migration
>>> was not working anyway (vmstate_load_state was erasing critical part
>>> of PL330State and causing segfaults while loading following fields).
>>
>> I still not understand versioning and migration
> 
> Incrementing the version (and minimum) is the right thing
> to do if you conclude the old one was hopelessly broken.
> Migration to and from old qemu breaks, but who cares since it was toast
> anyway.
> As far as I can tell pl330 is only on our zynq and exynos models
> so wont break our versioned 'virt' type.
> So from a migration point of view:

Since switching from VARRAY to VARRAY_POINTER does not change the size
of what's migrated, it should be possible to accept migration from old
qemu if we can ignore the data in such cases and default to something
(but what ? put the pl330 in reset state ?)

Thanks,
Damien