KVM Forum 2021

Upgrading VMMs with live VMs has always been a challenging problem. The currently accepted solution is live migrating VMs outside the host and then upgrading the VMM before the VMs are migrated back. This enforces the cloud infrastructure to maintain spare resources on other nodes to accommodate the incoming VMs. Along with this it incurs huge cost on the upgrade time as well as network usage. In an effort to reduce these costs we propose a novel approach in the upgrade workflow, which can upgrade the VMM without the need to migrate VMs outside of the host. This talk focuses on how with minimal changes in the existing libvirt migration workflow we can transfer the VMs to the new upgraded qemu binary with minimal downtime while preserving external connections and device states.