diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 8168bf8..0e625e6 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -218,13 +218,11 @@
 	 * slowdowns.
 	 */
 	if (pos == 0)
-		end_pfn = 1<<(PMD_SHIFT - PAGE_SHIFT);
+		end_pfn = PMD_SIZE >> PAGE_SHIFT;
 	else
-		end_pfn = ((pos + (PMD_SIZE - 1))>>PMD_SHIFT)
-				 << (PMD_SHIFT - PAGE_SHIFT);
+		end_pfn = round_up(pos, PMD_SIZE) >> PAGE_SHIFT;
 #else /* CONFIG_X86_64 */
-	end_pfn = ((pos + (PMD_SIZE - 1)) >> PMD_SHIFT)
-			<< (PMD_SHIFT - PAGE_SHIFT);
+	end_pfn = round_up(pos, PMD_SIZE) >> PAGE_SHIFT;
 #endif
 	if (end_pfn > (end >> PAGE_SHIFT))
 		end_pfn = end >> PAGE_SHIFT;
@@ -234,15 +232,13 @@
 	}
 
 	/* big page (2M) range */
-	start_pfn = ((pos + (PMD_SIZE - 1))>>PMD_SHIFT)
-			 << (PMD_SHIFT - PAGE_SHIFT);
+	start_pfn = round_up(pos, PMD_SIZE) >> PAGE_SHIFT;
 #ifdef CONFIG_X86_32
-	end_pfn = (end>>PMD_SHIFT) << (PMD_SHIFT - PAGE_SHIFT);
+	end_pfn = round_down(end, PMD_SIZE) >> PAGE_SHIFT;
 #else /* CONFIG_X86_64 */
-	end_pfn = ((pos + (PUD_SIZE - 1))>>PUD_SHIFT)
-			 << (PUD_SHIFT - PAGE_SHIFT);
-	if (end_pfn > ((end>>PMD_SHIFT)<<(PMD_SHIFT - PAGE_SHIFT)))
-		end_pfn = ((end>>PMD_SHIFT)<<(PMD_SHIFT - PAGE_SHIFT));
+	end_pfn = round_up(pos, PUD_SIZE) >> PAGE_SHIFT;
+	if (end_pfn > (round_down(end, PMD_SIZE) >> PAGE_SHIFT))
+		end_pfn = round_down(end, PMD_SIZE) >> PAGE_SHIFT;
 #endif
 
 	if (start_pfn < end_pfn) {
@@ -253,9 +249,8 @@
 
 #ifdef CONFIG_X86_64
 	/* big page (1G) range */
-	start_pfn = ((pos + (PUD_SIZE - 1))>>PUD_SHIFT)
-			 << (PUD_SHIFT - PAGE_SHIFT);
-	end_pfn = (end >> PUD_SHIFT) << (PUD_SHIFT - PAGE_SHIFT);
+	start_pfn = round_up(pos, PUD_SIZE) >> PAGE_SHIFT;
+	end_pfn = round_down(end, PUD_SIZE) >> PAGE_SHIFT;
 	if (start_pfn < end_pfn) {
 		nr_range = save_mr(mr, nr_range, start_pfn, end_pfn,
 				page_size_mask &
@@ -264,9 +259,8 @@
 	}
 
 	/* tail is not big page (1G) alignment */
-	start_pfn = ((pos + (PMD_SIZE - 1))>>PMD_SHIFT)
-			 << (PMD_SHIFT - PAGE_SHIFT);
-	end_pfn = (end >> PMD_SHIFT) << (PMD_SHIFT - PAGE_SHIFT);
+	start_pfn = round_up(pos, PMD_SIZE) >> PAGE_SHIFT;
+	end_pfn = round_down(end, PMD_SIZE) >> PAGE_SHIFT;
 	if (start_pfn < end_pfn) {
 		nr_range = save_mr(mr, nr_range, start_pfn, end_pfn,
 				page_size_mask & (1<<PG_LEVEL_2M));