[Qemu-devel] [Query] Live Migration between machines with different processor ids

[Jaggi, Manish]

Hi,

Posting again with my cavium ID and CCing relevant folks


Live Migration between machines with different processorIds

VM Migration between machines with different processorId values throws
error in qemu/kvm. Though this check is appropriate but is overkill where
two machines are of same SoC/arch family and have same core/gic but
delta could be in other parts of Soc which have no effect on VM
operation.

There could be two ways to address this issue by ignoring the
comparison of processorIDs and so need feedback from the
community on this.

a) Maintain a whitelist in qemu:

This will be a set of all processorIds which are compatible and migration can
happen between any of the machines with the Ids from this set. This set can
be statically built within qemu binary.

b) Provide an extra option with migrate command

   migrate tcp:<ip>:<port>:<dest_processor_id>

This is to fake the src_processor_id as dest_processor_id, so the qemu running
on destination machine will not complain. The overhead with this approach is
that the destination machines Id need to be known beforehand.

If there is some better way… please suggest.

Thanks,
Manish