'Get the mapping between the old PCI devices and the new PCI
devices that have been allocated during this migration.  The
correlation is based on PCI request ID which is unique per PCI
devices for SR-IOV ports.
:param context:  The request context.
:param instance: Get PCI mapping for this instance.
:param migration: The migration for this instance.
:Returns: dictionary of mapping {\'<old pci address>\': <New PciDevice>}'

def _get_pci_mapping_for_migration(self, context, instance, migration):

    migration_context = instance.migration_context
    if (not migration_context):
        return {}
    (old_pci_devices, new_pci_devices) = self._get_pci_devices_from_migration_context(migration_context, migration)
    if (old_pci_devices and new_pci_devices):
        LOG.debug('Determining    PCI    devices    mapping    using    migrationcontext:    old_pci_devices:    %(old)s,    new_pci_devices:    %(new)s', {'old': [dev for dev in old_pci_devices], 'new': [dev for dev in new_pci_devices]})
        return {old.address: new for old in old_pci_devices for new in new_pci_devices if (old.request_id == new.request_id)}
    return {}
