[PATCH kexec-tools 0/4] ppc64: Support kexec with initrd and DTB together

[Shivang Upadhyay]

On Tue, Nov 11, 2025 at 01:47:01PM +0000, Simon Horman wrote:
> On Wed, Oct 22, 2025 at 07:16:05PM +0530, Shivang Upadhyay wrote:
> > Currently, on ppc64 systems, kexec cannot directly use a
> > user-provided devicetreeblob (dtb) when booting a new
> > kernel with an initrd. This limitation exists because the
> > dtb must be modified at runtime — for example, to include
> > the initrd’s memory location and size, and to add
> > /memreserve/ entries based on the current system memory
> > layout.
> > 
> > Previously, kexec handled this by generating a fresh dtb in
> > memory from the running system’s /proc/device-tree directory.
> > However, this approach prevents users from making
> > intentional modifications to the dtb — such as changin boot
> > arguments, enabling or disabling devices, or testing kernel
> > changes that depend on specific device tree properties.
> > 
> > Adding support for user-provided dtb (with appropriate
> > patching by kexec) allows more control for developers,
> > particularly when experimenting with custom kernels or
> > hardware configurations.
> > 
> > This patch series lifts this restriction and ensures that
> > the necessary /memreserve/ sections are properly added to
> > the new DTB. on ppc64, it is mandatory, for the rebooting
> > cpu to be present in the new kernel’s dtb, so additional
> > logic has been added to identify and mark one of available
> > cpu as reboot cpu on currect system.
> > 
> > A new architecture-specific function, arch_do_unload(), has
> > been introduced to perform the necessary cleanup during
> > kexec unload. in ppc64, the reboot CPU changes due to kexec,
> > and it gets reset back on kexec unload.
> > 
> > Shivang Upadhyay (4):
> >   ppc64: ensure /memreserve/ sections exist in user-provided FDT
> >   ppc64: handle reboot CPU in case of user provided DTB
> >   Add arch_do_unload hook for arch-specific cleanup
> >   ppc64: life the dtb and initrd restriction
> 
> Thanks, applied.
Thanks Simon

~Shivang.