liveupdate: kho: two regression fixes

* fix order calculation for kho_unpreserve_pages() to make sure sure that
   the order calculation in kho_unpreserve_pages() mathes the order
   calculation in kho_preserve_pages().
 * fix math in calculation of KHO_TREE_MAX_DEPTH to make it work with 16KB
   pages.
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Merge tag 'liveupdate-fixes-2026-05-30' of git://git.kernel.org/pub/scm/linux/kernel/git/liveupdate/linux

Pull liveupdate fixes from Mike Rapoport:
 "Two kexec handover regression fixes:

   - fix order calculation for kho_unpreserve_pages() to make sure sure
     that the order calculation in kho_unpreserve_pages() mathes the
     order calculation in kho_preserve_pages().

   - fix math in calculation of KHO_TREE_MAX_DEPTH to make it work with
     16KB pages"

* tag 'liveupdate-fixes-2026-05-30' of git://git.kernel.org/pub/scm/linux/kernel/git/liveupdate/linux:
  kho: fix order calculation for kho_unpreserve_pages()
  kho: fix KHO_TREE_MAX_DEPTH for non-4KB page sizes

include/linux/kho/abi/kexec_handover.h

@@ -274,7 +274,7 @@ enum kho_radix_consts {
 	 * and 1 bitmap level.
 	 */
 	KHO_TREE_MAX_DEPTH =
-		DIV_ROUND_UP(KHO_ORDER_0_LOG2 - KHO_BITMAP_SIZE_LOG2,
+		DIV_ROUND_UP(KHO_ORDER_0_LOG2 - KHO_BITMAP_SIZE_LOG2 + 1,
 			     KHO_TABLE_SIZE_LOG2) + 1,
 };
 

kernel/liveupdate/kexec_handover.c

@@ -357,20 +357,6 @@ int kho_radix_walk_tree(struct kho_radix_tree *tree,
 }
 EXPORT_SYMBOL_GPL(kho_radix_walk_tree);
 
-static void __kho_unpreserve(struct kho_radix_tree *tree,
-			     unsigned long pfn, unsigned long end_pfn)
-{
-	unsigned int order;
-
-	while (pfn < end_pfn) {
-		order = min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
-
-		kho_radix_del_page(tree, pfn, order);
-
-		pfn += 1 << order;
-	}
-}
-
 /* For physically contiguous 0-order pages. */
 static void kho_init_pages(struct page *page, unsigned long nr_pages)
 {
@@ -860,6 +846,37 @@ void kho_unpreserve_folio(struct folio *folio)
 }
 EXPORT_SYMBOL_GPL(kho_unpreserve_folio);
 
+static unsigned int __kho_preserve_pages_order(unsigned long start_pfn,
+					       unsigned long end_pfn)
+{
+	unsigned int order = min(count_trailing_zeros(start_pfn),
+				 ilog2(end_pfn - start_pfn));
+
+	/*
+	 * Make sure all the pages in a single preservation are in the same NUMA
+	 * node. The restore machinery can not cope with a preservation spanning
+	 * multiple NUMA nodes.
+	 */
+	while (pfn_to_nid(start_pfn) != pfn_to_nid(start_pfn + (1UL << order) - 1))
+		order--;
+
+	return order;
+}
+
+static void __kho_unpreserve(struct kho_radix_tree *tree,
+			     unsigned long pfn, unsigned long end_pfn)
+{
+	unsigned int order;
+
+	while (pfn < end_pfn) {
+		order = __kho_preserve_pages_order(pfn, end_pfn);
+
+		kho_radix_del_page(tree, pfn, order);
+
+		pfn += 1 << order;
+	}
+}
+
 /**
  * kho_preserve_pages - preserve contiguous pages across kexec
  * @page: first page in the list.
@@ -885,16 +902,7 @@ int kho_preserve_pages(struct page *page, unsigned long nr_pages)
 	}
 
 	while (pfn < end_pfn) {
-		unsigned int order =
+		unsigned int order = __kho_preserve_pages_order(pfn, end_pfn);
-			min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
-
-		/*
-		 * Make sure all the pages in a single preservation are in the
-		 * same NUMA node. The restore machinery can not cope with a
-		 * preservation spanning multiple NUMA nodes.
-		 */
-		while (pfn_to_nid(pfn) != pfn_to_nid(pfn + (1UL << order) - 1))
-			order--;
 
 		err = kho_radix_add_page(tree, pfn, order);
 		if (err) {