linux-kernel - Re: [PATCH v4 02/30] kho: make debugfs interface optional

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Message-ID: <CA+CK2bCN-__524n+2wti+m8K6JntCudsR1--cFH6cW9CTXnmiA@mail.gmail.com>
Date: Mon, 6 Oct 2025 14:02:53 -0400
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: Pratyush Yadav <pratyush@...nel.org>
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Subject: Re: [PATCH v4 02/30] kho: make debugfs interface optional

On Mon, Oct 6, 2025 at 12:31 PM Pratyush Yadav <pratyush@...nel.org> wrote:
>
> On Mon, Sep 29 2025, Pasha Tatashin wrote:
>
> > Currently, KHO is controlled via debugfs interface, but once LUO is
> > introduced, it can control KHO, and the debug interface becomes
> > optional.
> >
> > Add a separate config CONFIG_KEXEC_HANDOVER_DEBUG that enables
> > the debugfs interface, and allows to inspect the tree.
> >
> > Move all debugfs related code to a new file to keep the .c files
> > clear of ifdefs.
> >
> > Co-developed-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
> > Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
> > Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
> > ---
> >  MAINTAINERS                      |   3 +-
> >  kernel/Kconfig.kexec             |  10 ++
> >  kernel/Makefile                  |   1 +
> >  kernel/kexec_handover.c          | 255 +++++--------------------------
> >  kernel/kexec_handover_debug.c    | 218 ++++++++++++++++++++++++++
> >  kernel/kexec_handover_internal.h |  44 ++++++
> >  6 files changed, 311 insertions(+), 220 deletions(-)
> >  create mode 100644 kernel/kexec_handover_debug.c
> >  create mode 100644 kernel/kexec_handover_internal.h
> >
> [...]
> > --- a/kernel/Kconfig.kexec
> > +++ b/kernel/Kconfig.kexec
> > @@ -109,6 +109,16 @@ config KEXEC_HANDOVER
> >         to keep data or state alive across the kexec. For this to work,
> >         both source and target kernels need to have this option enabled.
> >
> > +config KEXEC_HANDOVER_DEBUG
>
> Nit: can we call it KEXEC_HANDOVER_DEBUGFS instead? I think we would
> like to add a KEXEC_HANDOVER_DEBUG at some point to control debug
> asserts for KHO, and the naming would get confusing. And renaming config
> symbols is kind of a pain.

Done.

>
> > +     bool "kexec handover debug interface"
> > +     depends on KEXEC_HANDOVER
> > +     depends on DEBUG_FS
> > +     help
> > +       Allow to control kexec handover device tree via debugfs
> > +       interface, i.e. finalize the state or aborting the finalization.
> > +       Also, enables inspecting the KHO fdt trees with the debugfs binary
> > +       blobs.
> > +
> [...]
>
> --
> Regards,
> Pratyush Yadav