On Fri, Nov 14 2025, Pasha Tatashin wrote:
> Currently, kho_preserve_* and kho_unpreserve_* return -EBUSY if
> KHO is finalized. This enforces a rigid "freeze" on the KHO memory
> state.
>
> With the introduction of re-entrant finalization, this restriction is
> no longer necessary. Users should be allowed to modify the preservation
> set (e.g., adding new pages or freeing old ones) even after an initial
> finalization.
>
> The intended workflow for updates is now:
> 1. Modify state (preserve/unpreserve).
> 2. Call kho_finalize() again to refresh the serialized metadata.
>
> Remove the kho_out.finalized checks to enable this dynamic behavior.
>
> Signed-off-by: Pasha Tatashin <[email protected]>
> ---
> kernel/liveupdate/kexec_handover.c | 13 -------------
> 1 file changed, 13 deletions(-)
>
> diff --git a/kernel/liveupdate/kexec_handover.c
> b/kernel/liveupdate/kexec_handover.c
> index 27ef20565a5f..87e9b488237d 100644
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c
> @@ -183,10 +183,6 @@ static int __kho_preserve_order(struct kho_mem_track
> *track, unsigned long pfn,
> const unsigned long pfn_high = pfn >> order;
>
> might_sleep();
> -
> - if (kho_out.finalized)
> - return -EBUSY;
> -
> physxa = xa_load(&track->orders, order);
> if (!physxa) {
> int err;
> @@ -815,9 +811,6 @@ int kho_unpreserve_folio(struct folio *folio)
This can be void now. This would make consumers a bit simpler, since
right now, the memfd preservation logic does a WARN_ON() if this
function fails. That can be dropped now that the function can never
fail.
Same for kho_unpreserve_pages() and kho_unpreserve_vmalloc().
> const unsigned int order = folio_order(folio);
> struct kho_mem_track *track = &kho_out.track;
>
> - if (kho_out.finalized)
> - return -EBUSY;
> -
> __kho_unpreserve_order(track, pfn, order);
> return 0;
> }
> @@ -885,9 +878,6 @@ int kho_unpreserve_pages(struct page *page, unsigned int
> nr_pages)
> const unsigned long start_pfn = page_to_pfn(page);
> const unsigned long end_pfn = start_pfn + nr_pages;
>
> - if (kho_out.finalized)
> - return -EBUSY;
> -
> __kho_unpreserve(track, start_pfn, end_pfn);
>
> return 0;
> @@ -1066,9 +1056,6 @@ EXPORT_SYMBOL_GPL(kho_preserve_vmalloc);
> */
> int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
> {
> - if (kho_out.finalized)
> - return -EBUSY;
> -
> kho_vmalloc_free_chunks(preservation);
>
> return 0;
--
Regards,
Pratyush Yadav
