Hi Mike, On Thu, Feb 6, 2025 at 5:28 AM Mike Rapoport <rppt@xxxxxxxxxx> wrote: > We introduce a metadata file that the kernels pass between each other. How > they pass it is architecture specific. The file's format is a Flattened > Device Tree (fdt) which has a generator and parser already included in > Linux. When the root user enables KHO through /sys/kernel/kho/active, the > kernel invokes callbacks to every driver that supports KHO to serialize > its state. When the actual kexec happens, the fdt is part of the image > set that we boot into. In addition, we keep a "scratch regions" available > for kexec: A physically contiguous memory regions that is guaranteed to > not have any memory that KHO would preserve. The new kernel bootstraps > itself using the scratch regions and sets all handed over memory as in use. > When drivers initialize that support KHO, they introspect the fdt and > recover their state from it. This includes memory reservations, where the > driver can either discard or claim reservations. I have gone through your entire patchset, if you could provide an example of a specific driver that supports KHO it would help a lot for people to understand and more importantly help driver developers to adopt. Even with a simulated driver, e.g. netdevsim, it would be greatly helpful. Thanks.
