Re: [PATCH v4 00/14] kexec: introduce Kexec HandOver (KHO)

[Cong Wang]

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.