Public bug reported: Having upgraded to Ussuri, we've noted that live migrations now always fail across our hosts with newer Intel CPUs (identified by libvirt as Cascadelake-Server-noTSX).
When processing the CPU's features, the calls made by Nova to libvirt appear to result in an XML segment which includes 'policy' keys for each feature which may be set to 'disable'. When Nova interprets this (see https://github.com/openstack/nova/blob/master/nova/virt/libvirt/host.py#L699 and https://github.com/openstack/nova/blob/master/nova/virt/libvirt/config.py#L670) the 'policy' key does not appear to be handled, resulting in more CPU features being recorded against the hypervisor than it really has. When a live migration is scheduled, these additional feature requirements are then passed to the remote host which compares with its running features and identifies they are incompatible, despite the CPUs being identical. As a result we're currently unable to live migrate any VMs between hosts which use these CPUs. Further debug output is included in http://paste.openstack.org/show/798740/ Nova stable/ussuri 7d556106bfd3e64860dc26226d364876e8bce43c Ubuntu 18.04 libvirt 6.0.0-0ubuntu8.2~cloud0 ** Affects: nova Importance: Undecided Status: New -- You received this bug notification because you are a member of Yahoo! Engineering Team, which is subscribed to OpenStack Compute (nova). https://bugs.launchpad.net/bugs/1898715 Title: Live migration fails despite matching CPUs Status in OpenStack Compute (nova): New Bug description: Having upgraded to Ussuri, we've noted that live migrations now always fail across our hosts with newer Intel CPUs (identified by libvirt as Cascadelake-Server-noTSX). When processing the CPU's features, the calls made by Nova to libvirt appear to result in an XML segment which includes 'policy' keys for each feature which may be set to 'disable'. When Nova interprets this (see https://github.com/openstack/nova/blob/master/nova/virt/libvirt/host.py#L699 and https://github.com/openstack/nova/blob/master/nova/virt/libvirt/config.py#L670) the 'policy' key does not appear to be handled, resulting in more CPU features being recorded against the hypervisor than it really has. When a live migration is scheduled, these additional feature requirements are then passed to the remote host which compares with its running features and identifies they are incompatible, despite the CPUs being identical. As a result we're currently unable to live migrate any VMs between hosts which use these CPUs. Further debug output is included in http://paste.openstack.org/show/798740/ Nova stable/ussuri 7d556106bfd3e64860dc26226d364876e8bce43c Ubuntu 18.04 libvirt 6.0.0-0ubuntu8.2~cloud0 To manage notifications about this bug go to: https://bugs.launchpad.net/nova/+bug/1898715/+subscriptions -- Mailing list: https://launchpad.net/~yahoo-eng-team Post to : yahoo-eng-team@lists.launchpad.net Unsubscribe : https://launchpad.net/~yahoo-eng-team More help : https://help.launchpad.net/ListHelp
