I listen to the Linux kernel mailing list is presented the sixth version of patches implementing the Kexec HandOver (KHO) mechanism, developed by engineers from Amazon, Microsoft, and Google. The patches are already accepted into the mm-everything branch, where changes for the future kernel 6.16 branch related to memory management are accumulated. Based on Kexec HandOver, Google is developing the Live Update Orchestrator (LUO) subsystem, which allows the kernel to be restarted without stopping the operation of devices.
Kexec HandOver provides the ability to start a new kernel from an old one without losing the system state. Currently, the kexec() call functions only as a bootloader, simply launching a new kernel, which then completely reinitializes the system, equivalent to a restart, just without firmware involvement. The proposed series of patches implements a different approach. Before transferring control 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, once in control, restores the serialized state back. From the perspective of other programs, the kernel replacement operation is seamless.
Kexec HandOver can prove useful in situations where downtime is unacceptable, and it is necessary to ensure a continuous workflow 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, preserving their execution state. KVM), without affecting the memory used by virtual machines, and maintaining their execution state.
Kilde: opennet.ru
