Re: [PATCH for-7.1 0/4] use dc->vmsd with spapr devices vmstate

[Daniel Henrique Barboza <danielhb413@gmail.com>]

On 3/22/22 22:49, David Gibson wrote:
> On Tue, Mar 22, 2022 at 03:38:50PM -0300, Daniel Henrique Barboza wrote:
>> Hi,
>>
>> This short series converts some spapr devices to use the dc->vmsd
>> interface to register the vmstate. For most of them it was needed
>> to use qdev_set_legacy_instance_id() to keep compatibility with the
>> instance_id being used for awhile.
>>
>> Although no functional changes were made the resulting code is a bit
>> shorter and maintainable. After these patches there are only 3 places
>> where vmstate_register() APIs are being used.
>>
>> No behavior changes were detected when testing migration scenarios with
>> hotplug/unplug of devices.
> 
> Looks good tome.

It looked good to me until, after further testing, I noticed that patch 03
breaks backward migration:

qemu_loadvm_state_section_startfull 560 (spapr_iommu) 0 2
qemu-system-ppc64: Unknown savevm section or instance 'spapr_iommu' 0. Make sure
that your current VM setup matches your saved VM setup, including any hotplugged devices

qemu-system-ppc64: load of migration failed: Invalid argument

I made a follow-up in the instance_id discussion [1] about it. For now patches 1-3 are
compromised. Only patch 04 is worth considering because the spapr_nvdimm device isn't
setting a custom instance_id.


[1] https://lists.gnu.org/archive/html/qemu-devel/2022-03/msg05942.html



Thanks,


Daniel

>