To minimize downtime, run all of the SR-IOV commands as a group while the root domain is in delayed reconfiguration or a guest domain is stopped. The SR-IOV commands that are limited in this way are the ldm create-vf, ldm destroy-vf, ldm add-io, and ldm remove-io commands.
Typically, virtual functions are assigned to more than one guest domain. A reboot of the root domain affects all of the guest domains that have been assigned the root domain's virtual functions.
Because an unused InfiniBand virtual function has very little overhead, you can avoid downtime by creating the necessary virtual functions ahead of time, even if they are not used immediately.