Re: [PATCH V3 2/3] arm64/mm/hotplug: Enable MEM_OFFLINE event handling

  arch/arm64/mm/mmu.c | 37 ++++++++++++++++++++++++++++++++-----
  1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index df3b7415b128..6b171bd88bcf 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c

@@ -1482,13 +1482,40 @@ static int prevent_bootmem_remove_notifier(struct notifier_block *nb,
  	unsigned long end_pfn = arg->start_pfn + arg->nr_pages;
  	unsigned long pfn = arg->start_pfn;
  
-	if (action != MEM_GOING_OFFLINE)
+	if ((action != MEM_GOING_OFFLINE) && (action != MEM_OFFLINE))
  		return NOTIFY_OK;
  
-	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
-		ms = __pfn_to_section(pfn);
-		if (early_section(ms))
-			return NOTIFY_BAD;
+	if (action == MEM_GOING_OFFLINE) {
+		for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+			ms = __pfn_to_section(pfn);
+			if (early_section(ms)) {
+				pr_warn("Boot memory offlining attempted\n");
+				return NOTIFY_BAD;
+			}
+		}
+	} else if (action == MEM_OFFLINE) {
+		for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+			ms = __pfn_to_section(pfn);
+			if (early_section(ms)) {
+
+				/*
+				 * This should have never happened. Boot memory
+				 * offlining should have been prevented by this
+				 * very notifier. Probably some memory removal
+				 * procedure might have changed which would then
+				 * require further debug.
+				 */
+				pr_err("Boot memory offlined\n");
+
+				/*
+				 * Core memory hotplug does not process a return
+				 * code from the notifier for MEM_OFFLINE event.
+				 * Error condition has been reported. Report as
+				 * ignored.
+				 */
+				return NOTIFY_DONE;
+			}
+		}
  	}
  	return NOTIFY_OK;
  }