linux-kernel - [PATCH v1 11/13] kho: Allow memory preservation state updates after finalization

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Message-ID: <20251114155358.2884014-12-pasha.tatashin@soleen.com>
Date: Fri, 14 Nov 2025 10:53:56 -0500
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: akpm@...ux-foundation.org,
	bhe@...hat.com,
	pasha.tatashin@...een.com,
	rppt@...nel.org,
	jasonmiu@...gle.com,
	arnd@...db.de,
	coxu@...hat.com,
	dave@...ilevsky.ca,
	ebiggers@...gle.com,
	graf@...zon.com,
	kees@...nel.org,
	linux-kernel@...r.kernel.org,
	kexec@...ts.infradead.org,
	linux-mm@...ck.org
Subject: [PATCH v1 11/13] kho: Allow memory preservation state updates after finalization

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 <pasha.tatashin@...een.com>
---
 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)
 	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;
-- 
2.52.0.rc1.455.g30608eb744-goog