1 files changed, 30 insertions, 4 deletions

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index f35c66c5959a..b92591fa8970 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1230,17 +1230,43 @@ const char *arch_vma_name(struct vm_area_struct *vma)
         return NULL;
 }
 
-#ifdef CONFIG_X86_UV
-unsigned long memory_block_size_bytes(void)
+static unsigned long probe_memory_block_size(void)
 {
+        /* start from 2g */
+        unsigned long bz = 1UL<<31;
+
+#ifdef CONFIG_X86_UV
         if (is_uv_system()) {
                 printk(KERN_INFO "UV: memory block size 2GB\n");
                 return 2UL * 1024 * 1024 * 1024;
         }
-        return MIN_MEMORY_BLOCK_SIZE;
-}
 #endif
 
+        /* less than 64g installed */
+        if ((max_pfn << PAGE_SHIFT) < (16UL << 32))
+                return MIN_MEMORY_BLOCK_SIZE;
+
+        /* get the tail size */
+        while (bz > MIN_MEMORY_BLOCK_SIZE) {
+                if (!((max_pfn << PAGE_SHIFT) & (bz - 1)))
+                        break;
+                bz >>= 1;
+        }
+
+        printk(KERN_DEBUG "memory block size : %ldMB\n", bz >> 20);
+
+        return bz;
+}
+
+static unsigned long memory_block_size_probed;
+unsigned long memory_block_size_bytes(void)
+{
+        if (!memory_block_size_probed)
+                memory_block_size_probed = probe_memory_block_size();
+
+        return memory_block_size_probed;
+}
+
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 /*
  * Initialise the sparsemem vmemmap using huge-pages at the PMD level.