Comment 3 for bug 1704071

All,

I have a check on the change history. "VM.assert_can_migrate" was not only for block device migration before this commit:
https://review.openstack.org/#/c/247853/23/nova/virt/xenapi/vmops.py@2194

I don't know the reason why it went in that way.
But anyway I think it's accepted to skip VM.assert_can_migrate for >XS7.0 (platform version is 2.1) basing on the situation that it is only invoked for block live migration.

Bob's suggestion on "only looking at VDI_MAP' is good if we can do it. But unfortunately seems we can't. The reason is that since XS7.0, assert_cam_migrate requires vif_map, vdi_map existing in the input parameters. Actually it ever was to empty vdi_map and vif_map before invoking "assert_cam_migrate".
https://review.openstack.org/#/c/9879/10/nova/virt/xenapi/vmops.py@1550

Also see the errors of "VIF_NOT_IN_MAP" in https://bugs.launchpad.net/nova/+bug/1658877

Regards,
Jianghua