Re: [PATCH v5 05/22] liveupdate: kho: when live update add KHO image during kexec load

Mike Rapoport
2025-11-11T20:19:11Z

On Mon, Nov 10, 2025 at 10:31:23AM -0500, Pasha Tatashin wrote:
> On Mon, Nov 10, 2025 at 7:47 AM Mike Rapoport <rppt@kernel.org> wrote:
> >
> > On Fri, Nov 07, 2025 at 04:03:03PM -0500, Pasha Tatashin wrote:
> > > In case KHO is driven from within kernel via live update, finalize will
> > > always happen during reboot, so add the KHO image unconditionally.
> > >
> > > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> > > ---
> > > kernel/liveupdate/kexec_handover.c | 3 ++-
> > > 1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> > > index 9f0913e101be..b54ca665e005 100644
> > > --- a/kernel/liveupdate/kexec_handover.c
> > > +++ b/kernel/liveupdate/kexec_handover.c
> > > @@ -15,6 +15,7 @@
> > > #include <linux/kexec_handover.h>
> > > #include <linux/libfdt.h>
> > > #include <linux/list.h>
> > > +#include <linux/liveupdate.h>
> > > #include <linux/memblock.h>
> > > #include <linux/page-isolation.h>
> > > #include <linux/vmalloc.h>
> > > @@ -1489,7 +1490,7 @@ int kho_fill_kimage(struct kimage *image)
> > > int err = 0;
> > > struct kexec_buf scratch;
> > >
> > > - if (!kho_out.finalized)
> > > + if (!kho_out.finalized && !liveupdate_enabled())
> > > return 0;
> >
> > This feels backwards, I don't think KHO should call liveupdate methods.
>
> It is backward, but it is a requirement until KHO becomes stateless.
> LUO does not have dependencies on userspace state of when kexec is
> loaded. In fact the next kernel must be loaded before the brownout as
> it is an expensive operation. The sequence of events should:
>
> 1. Load the next kernel in memory
> 2. Preserve resources via LUO
> 3. Do Kexec reboot

I believe that when my concerns about "[PATCH v5 02/22] liveupdate:
luo_core: integrate with KHO" [1] are resolved this patch won't be needed.

[1] https://lore.kernel.org/all/aROZi043lxtegqWE@kernel.org/

> Pasha

--
Sincerely yours,
Mike.