Re: [PATCH v4 3/6] mm/hotplug: Allow architecture to override memmap on memory support check

[David Hildenbrand]

On 18.07.23 04:44, Aneesh Kumar K.V wrote:

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

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

No :)

Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
---
  mm/memory_hotplug.c | 22 +++++++++++++++++++---
  1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 1b19462f4e72..5921c81fcb70 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1247,9 +1247,25 @@ static int online_memory_block(struct memory_block *mem, 
void *arg)
        return device_online(&mem->dev);
  }

+#ifndef arch_supports_memmap_on_memory

+static inline bool arch_supports_memmap_on_memory(unsigned long size)
+{
+       unsigned long nr_vmemmap_pages = size >> PAGE_SHIFT;
+       unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
+
+       /*
+        * As default, we want the vmemmap to span a complete PMD such that we
+        * can map the vmemmap using a single PMD if supported by the
+        * architecture.
+        */
+       return IS_ALIGNED(vmemmap_size, PMD_SIZE);
+}
+#endif
+
  static bool mhp_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;

@@ -1281,8 +1297,8 @@ static bool mhp_supports_memmap_on_memory(unsigned long size)

         */
        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));
+              IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT)) &&
+              arch_supports_memmap_on_memory(size);
  }

/*

Acked-by: David Hildenbrand <da...@redhat.com>

--
Cheers,

David / dhildenb