A Linux kernel mailing list announced the sixth version of patches implementing the Kexec HandOver (KHO) mechanism, developed by engineers from Amazon, Microsoft, and Google. The patches have already been accepted into the mm-everything branch, which accumulates changes for the upcoming kernel 6.16 branch related to memory management. Based on Kexec HandOver, Google is developing a Live Update Orchestrator (LUO) subsystem that allows the kernel to be rebooted without interrupting device operations.
Kexec HandOver enables the launching of a new kernel from an old one without losing the system state. Currently, the kexec() call acts only as a bootloader, simply launching a new kernel that then completely reinitializes the system, equivalent to a reboot, but without invoking firmware. The proposed series of patches implements a different approach. Before handing control over to the new kernel version, the state of key kernel subsystems is serialized into a memory region that will not be affected by subsequent operations. The new kernel, upon gaining control, restores the serialized state back. From the perspective of other programs, the kernel replacement operation is seamless.
Kexec HandOver could be useful in situations where stopping is not acceptable, and it's necessary to maintain a continuous operation cycle for individual devices. For example, on virtualization servers, Kexec HandOver can be used to update the kernel (and hypervisor) without affecting the memory occupied by virtual machines while preserving their execution state. KVM), without affecting memory occupied by virtual machines, and preserving their execution state.
Forrás: opennet.ru
