Speaker
Description
As cloud infrastructure continues to push toward zero-downtime host maintenance, extending the capabilities of kexec-based Live Update to minimize guest disruption is becoming increasingly critical. This proposal introduces the architectural concept of an "Orphaned VM"—a virtual machine that actively executes guest instructions on isolated physical hardware while completely decoupled from a host operating system or a VMM during a host reboot. This execution asymmetry is achieved by introducing the "Caretaker," a specialized bare-metal primitive interpose layer that runs within the hypervisor's privileged hardware state to trap and resolve some VM exits locally while the host kernel is offline. This session will explore the mechanisms required to orchestrate this transition using the LUO, focusing on how vcpufd structures are preserved across the reboot gap, how physical CPUs are shielded from boot-time reset signals, and how asynchronous hardware challenges like timekeeping drift, stray interrupts, and guest-to-guest IPI routing are mitigated during the management gap.
RFC Reference & Discussion Thread: For full architectural background and ongoing community feedback, see the original mailing list discussion at https://lore.kernel.org/all/afEwWZksU0Fw61oT@plex