To the kernel code base LinuxThe 6.19 release, which will be based on the 6.19 kernel in early February, uses the code from the LUO (Live Update Orchestrator) subsystem, developed by Google for updating the kernel in Live mode without a physical reboot. The subsystem is based on the KHO (Kexec HandOver) mechanism, previously added to the 6.16 kernel and enabling the launch of a new kernel from an old one without losing the system state.
Live Update Orchestrator enables a full reboot and kernel update without interrupting operation or losing the state of the system, devices, and processes. In addition to the KHO functionality, the LUO subsystem preserves the state of devices and RAM, and ensures the continuity of operations related to DMA and interrupt handling. This state is preserved before switching to a new kernel and is restored after the new kernel is activated without disrupting the continuous device operations performed by the system and user-space applications.
A special feature of the new patch series is the ability to save memfd file descriptors to maintain the state of important data in memory between reboots, such as the contents of RAM. virtual machinesRapid updating is mentioned as the main area of use of the subsystem. servers with virtualization systems based on the KVM hypervisor to eliminate security and stability issues while minimizing virtual machine downtime. Google is already using this technology in its production environments.
Unlike livepatch, Ksplice, kpatch, kGraft, and other hot-patching mechanisms, the new subsystem is not limited to applying individual patches to a running kernel; it allows for complete kernel replacement. Unlike kexec, the LUO subsystem preserves the state of devices and kernel subsystems across reboots, while kexec functions solely as a bootloader, launching a new kernel with a complete system reinitialization (the equivalent of a reboot, but without transferring control to the firmware).
Source: opennet.ru
