[pve-devel] Snapshots / Qemu Version

[Stefan Priebe]

Am 25.05.2013 19:24, schrieb Alexandre DERUMIER:
>> You have:
>> pc-i440fx-1.4 Standard PC (i440FX + PIIX, 1996)
>> and
>> pc-q35-1.4 Standard PC (Q35 + ICH9, 2009)
>>
>
> Yes, q35 is not yet ready, but in the future (maybe next year), it should become the default.
> It's emulated pci-express slots and new things.
>
>
>
>> I think the correct way would be:
>> 1.) always pass the -machine parameter so we "know" our default
>> 2.) save the current machine parameter in config
>> 3.) when creating a snapshot save this value too
>
> I think for snapshot, indeed we should save qemu version.

Mhm qemu version. You mean the result form kvm_version() ? Remember that 
the version might have changed from starting the vm to the snapshot point.

>>> Same problem occours if we have a running VM (qemu 1.4) and we migrate
>>> this one to another server running 1.X. We also need to set the machine
>>> parameter here.
>
> For live migration, I think we can detect with qmp the qemu version, the pass the parameter to the target vm.
> (So it can work with existing vm configs, and we don't need to update the config file when we update qemu).
> Maybe this should be optionnal, because I like to use live migrate to update to new qemu version, without restarting the vm.
> I personnaly never have had problem with live migration from lower to higher qemu version.

To me this works for 1.4 to 1.4.3 and i use it in that case too. But for 
1.3 to 1.4 or 1.4 to 1.5 it seems to fail by 20% for me. So there is no 
guarantee that it works. I think stop and start is the safer way to go here.

Greets,
Stefan