NVMe Controller Migration

Overview

NVMe controller migration is the body of prior NVMe technical-proposal work that the PCIe exported NVM subsystem builds upon to enable live VM migration. Two foundational proposals lead the chain. TP4159, presented two years before the 2025 OCP Global Summit talk, performs the actual controller migration — moving tracked changes, controller information, and state so the destination VM continues without missing a beat. TP4165 removes the hypervisor from the IO path by reporting used LBAs, migrating them to the new SSD, and tracking dirtying until few enough dirty blocks remain to stun the VM for the final migration. Alongside these, a quality-of-service technical proposal is in process so that each VM is rate-limited to only the namespace resources it was allotted, preventing noisy-neighbor problems between large and small VMs.

These proposals are the temporal foundation for the newer PCIe exported NVM subsystem work: TP4159 (2023) established controller-state migration, TP4165 added dirty tracking and used-LBA reporting, and as of October 2025 the QoS proposal and the exported-subsystem proposal were still in process.