Speakers
Description
Orhpaned VMs [0] is proposed to be the next evolution of hypervisor live update. It relies on a specialized micro-hypervisor, called the Caretaker, which handles VM Exits during the time between old kernel shutting down and new kernel booting up. The Caretaker reduces the downtime observed by the VM during live update by servicing VM Exits during this transition period.
The Caretaker is not a full hypervisor or VMM, so it cannot service all the VM Exits. If it cannot handle a VM Exit, it must pause the VM and wait for the next kernel to take over. The success of the Caretaker in reducing observed VM downtime relies on which VM Exits it can and can't service, and how frequently they occur.
In this talk, we will present the types and frequency of VM Exits observed under some sample workloads. We will also categorize the VM Exits into ones which the Caretaker can handle and the ones which it can't.
By combining the frequency of VM Exits and whether they can be handled, we can estimate observed VM downtime, and decide how effective Orhpaned VMs can be.
[0] https://lore.kernel.org/all/afEwWZksU0Fw61oT@plex/