A Linux kernel codebase, on which release 6.19 will be based in early February, has accepted the code for the LUO (Live Update Orchestrator) subsystem developed by Google to update the kernel in live mode without physical rebooting. The subsystem is based on the KHO (Kexec HandOver) mechanism, previously added in kernel 6.16, which enables launching a new kernel from an old one without losing the system state.
The Live Update Orchestrator allows for a complete reboot and update of the kernel without stopping operations and without losing the system state, devices, and processes. In addition to the functionality of KHO, the LUO subsystem saves the state of devices and RAM and ensures the continuity of operations related to DMA and interrupt handling. The state is saved until switching to the new kernel and is restored after the new kernel is activated without interrupting continuous operations with devices carried out by the system and applications in user space.
A feature of the new series of patches is the ability to preserve memfd file descriptors to maintain the state of critical data in memory between reboots, such as the contents of RAM. virtuális gépekhezThe primary area of use for the subsystem is cited as rapid updates szerverek with virtualization systems based on the KVM hypervisor, to eliminate security and stability issues with minimal downtime for virtual machines. Google already uses this technology in its working environments.
Unlike livepatch, Ksplice, kpatch, kGraft, and other hot-patch overlay mechanisms, the new subsystem is not limited to applying individual fixes to the running kernel and allows for a complete kernel replacement. Unlike the kexec call, the LUO subsystem preserves the state of devices and kernel subsystems between reboots, while the kexec call only serves as a loader that launches a new kernel with a complete system reinitialization (equivalent to rebooting, but without transferring control to the firmware).
Forrás: opennet.ru
