1 files changed, 29 insertions, 4 deletions

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 45241de66785..dca9abf2b85c 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1328,14 +1328,39 @@ int kern_addr_valid(unsigned long addr)
         return pfn_valid(pte_pfn(*pte));
 }
 
+/*
+ * Block size is the minimum amount of memory which can be hotplugged or
+ * hotremoved. It must be power of two and must be equal or larger than
+ * MIN_MEMORY_BLOCK_SIZE.
+ */
+#define MAX_BLOCK_SIZE (2UL << 30)
+
+/* Amount of ram needed to start using large blocks */
+#define MEM_SIZE_FOR_LARGE_BLOCK (64UL << 30)
+
 static unsigned long probe_memory_block_size(void)
 {
-        unsigned long bz = MIN_MEMORY_BLOCK_SIZE;
+        unsigned long boot_mem_end = max_pfn << PAGE_SHIFT;
+        unsigned long bz;
 
-        /* if system is UV or has 64GB of RAM or more, use large blocks */
-        if (is_uv_system() || ((max_pfn << PAGE_SHIFT) >= (64UL << 30)))
-                bz = 2UL << 30; /* 2GB */
+        /* If this is UV system, always set 2G block size */
+        if (is_uv_system()) {
+                bz = MAX_BLOCK_SIZE;
+                goto done;
+        }
 
+        /* Use regular block if RAM is smaller than MEM_SIZE_FOR_LARGE_BLOCK */
+        if (boot_mem_end < MEM_SIZE_FOR_LARGE_BLOCK) {
+                bz = MIN_MEMORY_BLOCK_SIZE;
+                goto done;
+        }
+
+        /* Find the largest allowed block size that aligns to memory end */
+        for (bz = MAX_BLOCK_SIZE; bz > MIN_MEMORY_BLOCK_SIZE; bz >>= 1) {
+                if (IS_ALIGNED(boot_mem_end, bz))
+                        break;
+        }
+done:
         pr_info("x86/mm: Memory block size: %ldMB\n", bz >> 20);
 
         return bz;