On Thu, May 01, 2025 at 03:54:24PM -0700, Changyuan Lyu wrote: > +This document expects that you are familiar with the base KHO > +:ref:`concepts <concepts>`. If you have not read The reference label is generic and can collide with future patches. It should've been disambiguated as kho_concepts instead. > +them yet, please do so now. > + > +Prerequisites > +============= > + > +KHO is available when the ``CONFIG_KEXEC_HANDOVER`` config option is set to y > +at compile time. Every KHO producer may have its own config option that you when the kernel is compiled with ``CONFIG_KEXEC_HANDOVER`` set to y. > +need to enable if you would like to preserve their respective state across > +kexec. > + > <snipped>... > +First, before you perform a KHO kexec, you need to move the system into > +the :ref:`KHO finalization phase <finalization_phase>` ::
kho_finalization_phase to disambiguate label. > +Next, load the target payload and kexec into it. It is important that you > +use the ``-s`` parameter to use the in-kernel kexec file loader, as user > +space kexec tooling currently has no support for KHO with the user space > +based file loader :: > + > + # kexec -l Image --initrd=initrd -s > + # kexec -e Use full paths to kernel and initramfs image. > +``/sys/kernel/debug/kho/out/scratch_len`` > + To support continuous KHO kexecs, we need to reserve > + physically contiguous memory regions that will always stay > + available for future kexec allocations. This file describes > + the length of these memory regions. Kexec user space tooling > + can use this to determine where it should place its payload > + images. "Length of KHO scratch region, which is a physically contiguous memory regions that will always available for future kexec allocations. Kexec user space tools can use this file to determine where it should place its payload images." > + > +``/sys/kernel/debug/kho/out/scratch_phys`` > + To support continuous KHO kexecs, we need to reserve > + physically contiguous memory regions that will always stay > + available for future kexec allocations. This file describes > + the physical location of these memory regions. Kexec user space > + tooling can use this to determine where it should place its > + payload images. "Physical location of KHO scratch region. Kexec user space tools can use this file in conjunction to scratch_phys to determine where it should place its payload images." > +.. SPDX-License-Identifier: GPL-2.0-or-later > +.. _concepts: The label can be ambiguous. It should've been _kho_concepts instead. > +.. _finalization_phase: The label should be _kho_finalization_phase. > +Generally, A KHO user serialize its state into its own FDT and instructs "Generally, a KHO user ..." > +KHO to preserve the underlying memory, such that after kexec, the new kernel > +can recover its state from the preserved FDT. > + Thanks. -- An old man doll... just what I always wanted! - Clara
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