Re: [Qemu-devel] Live migration from Qemu 2.12 hosts to Qemu 3.2 hosts, with VMX flag enabled in the guest?

[Paolo Bonzini]

On 18/01/19 11:02, Dr. David Alan Gilbert wrote:
>>
>> It fails if the flag is set, rather than if any nested virtualization has
>> been used before.
>>
>> I'm concerned I will end up with a requirement for *all* guests to be
>> restarted in order to migrate them to the new hosts, rather than just the
>> ones that would have a problem.
> I think you should be able to migrate from 2.12->3.1 like this, but
> you'd hit the problem when you then try and migrate again between your
> new QEMUs.
> 
> I guess we could modify it to wire it to machine type, so that
> older machine types didn't block.

That would also be wrong.  The old machine types _could_ be using KVM
and they have no way to block the live migration.

The solution is to restart the VM using "-cpu host,-vmx".

Paolo