Re: [PATCH v2 00/13] kho: simplify state machine and enable dynamic updates

Pasha Tatashin
2025-11-14T22:07:21Z

On Fri, Nov 14, 2025 at 5:00 PM Pasha Tatashin
<pasha.tatashin@soleen.com> wrote:
>
> On Fri, Nov 14, 2025 at 4:44 PM Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > On Fri, 14 Nov 2025 13:59:49 -0500 Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> >
> > > Andrew: This series applies against mm-nonmm-unstable, but should
> > > go right before LUOv5, i.e. on top of:
> > > "liveupdate: kho: use %pe format specifier for error pointer printing"
> > >
> > > Changelog v2:
> > > - Addressed comments from Mike and Pratyush
> > > - Added Review-bys.
> > >
> > > It also replaces the following patches, that once applied should be
> > > dropped from mm-nonmm-unstable:
> > > "liveupdate: kho: when live update add KHO image during kexec load"
> > > "liveupdate: Kconfig: make debugfs optional"
> > > "kho: enable KHO by default"
> > >
> > > This patch series refactors the Kexec Handover subsystem to transition
> > > from a rigid, state-locked model to a dynamic, re-entrant architecture.
> > > It also introduces usability improvements.
> >
> > OK.

Also, with this series, kho_unpreserve_folio() returns void, and LUOv5
requires two small fixes where this function is used:

1. fixup for mm: "memfd_luo: allow preserving memfd"
diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
index e366de627264..ba435590d2cf 100644
--- a/mm/memfd_luo.c
+++ b/mm/memfd_luo.c
@@ -138,7 +138,7 @@ static struct memfd_luo_folio_ser
*memfd_luo_preserve_folios(struct file *file,
err_unpreserve:
i--;
for (; i >= 0; i--)
- WARN_ON_ONCE(kho_unpreserve_folio(folios[i]));
+ kho_unpreserve_folio(folios[i]);
vfree(pfolios);
err_unpin:
unpin_folios(folios, nr_folios);
@@ -170,7 +170,7 @@ static void memfd_luo_unpreserve_folios(void *fdt,
struct memfd_luo_folio_ser *p

folio = pfn_folio(PRESERVED_FOLIO_PFN(pfolio->foliodesc));

- WARN_ON_ONCE(kho_unpreserve_folio(folio));
+ kho_unpreserve_folio(folio);
unpin_folio(folio);
}

2. Fixup for liveupdate: luo_core: integrate with KHO:

diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
index 29a094ee225c..f0bc3ee0a10b 100644
--- a/kernel/liveupdate/luo_core.c
+++ b/kernel/liveupdate/luo_core.c
@@ -305,7 +305,7 @@ void luo_free_unpreserve(void *mem, size_t size)
return;

folio = virt_to_folio(mem);
- WARN_ON_ONCE(kho_unpreserve_folio(folio));
+ kho_unpreserve_folio(folio);
folio_put(folio);
}

> >
> > Where are we with the series "Live Update Orchestrator, v5"?
>
> I am working on LUOv6, it is going to be an incremental update with
> much smaller delta compared to v4->v5, addressing all the comments
> collected so far. I plan to send it out this weekend.
>
> Thank you,
> Pasha
>
> > I'm seeing a couple of review comments which I plan to circle back on:
> >
> > https://lkml.kernel.org/r/aROZi043lxtegqWE@kernel.org
> > https://lkml.kernel.org/r/mafs0ms4tajcs.fsf@kernel.org
> > and a comment from yourself against
> > liveupdate-luo_core-integrate-with-kho.patch which indicates that you
> > plan to update that patch?