Subject: [PATCH v3 3/7] mm/hotplug: Allow architecture to override memmap on memory support check

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Tue, 11 Jul 2023 10:18:29 +0530

Some architectures would want different restrictions. Hence add an
architecture-specific override.

Both the PMD_SIZE check and pageblock alignment check are moved there.

Signed-off-by: Aneesh Kumar K.V <[email-masked]>
---
 mm/memory_hotplug.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 1b19462f4e72..07c99b0cc371 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1247,12 +1247,20 @@ static int online_memory_block(struct memory_block *mem, void *arg)
 	return device_online(&mem->dev);
 }
 
-static bool mhp_supports_memmap_on_memory(unsigned long size)
+#ifndef arch_supports_memmap_on_memory
+static inline bool arch_supports_memmap_on_memory(unsigned long size)
 {
-	unsigned long nr_vmemmap_pages = size / PAGE_SIZE;
+	unsigned long nr_vmemmap_pages = size >> PAGE_SHIFT;
 	unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
 	unsigned long remaining_size = size - vmemmap_size;
 
+	return IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
+		IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT));
+}
+#endif
+
+static bool mhp_supports_memmap_on_memory(unsigned long size)
+{
 	/*
 	 * Besides having arch support and the feature enabled at runtime, we
 	 * need a few more assumptions to hold true:
@@ -1280,9 +1288,8 @@ static bool mhp_supports_memmap_on_memory(unsigned long size)
 	 *       populate a single PMD.
 	 */
 	return mhp_memmap_on_memory() &&
-	       size == memory_block_size_bytes() &&
-	       IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
-	       IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT));
+		size == memory_block_size_bytes() &&
+		arch_supports_memmap_on_memory(size);
 }
 
 /*
-- 
2.41.0