1 files changed, 21 insertions, 0 deletions

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 5ecb23a57d2f..d99bc6ac4884 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -741,8 +741,22 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
         /* head if not big page alignment ? */
         start_pfn = start >> PAGE_SHIFT;
         pos = start_pfn << PAGE_SHIFT;
+#ifdef CONFIG_X86_32
+        /*
+         * Don't use a large page for the first 2/4MB of memory
+         * because there are often fixed size MTRRs in there
+         * and overlapping MTRRs into large pages can cause
+         * slowdowns.
+         */
+        if (pos == 0)
+                end_pfn = 1<<(PMD_SHIFT - PAGE_SHIFT);
+        else
+                end_pfn = ((pos + (PMD_SIZE - 1))>>PMD_SHIFT)
+                                 << (PMD_SHIFT - PAGE_SHIFT);
+#else /* CONFIG_X86_64 */
         end_pfn = ((pos + (PMD_SIZE - 1)) >> PMD_SHIFT)
                         << (PMD_SHIFT - PAGE_SHIFT);
+#endif
         if (end_pfn > (end >> PAGE_SHIFT))
                 end_pfn = end >> PAGE_SHIFT;
         if (start_pfn < end_pfn) {
@@ -753,16 +767,22 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
         /* big page (2M) range */
         start_pfn = ((pos + (PMD_SIZE - 1))>>PMD_SHIFT)
                          << (PMD_SHIFT - PAGE_SHIFT);
+#ifdef CONFIG_X86_32
+        end_pfn = (end>>PMD_SHIFT) << (PMD_SHIFT - 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));
+#endif
+
         if (start_pfn < end_pfn) {
                 nr_range = save_mr(mr, nr_range, start_pfn, end_pfn,
                                 page_size_mask & (1<<PG_LEVEL_2M));
                 pos = end_pfn << PAGE_SHIFT;
         }
 
+#ifdef CONFIG_X86_64
         /* big page (1G) range */
         start_pfn = ((pos + (PUD_SIZE - 1))>>PUD_SHIFT)
                          << (PUD_SHIFT - PAGE_SHIFT);
@@ -783,6 +803,7 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
                                 page_size_mask & (1<<PG_LEVEL_2M));
                 pos = end_pfn << PAGE_SHIFT;
         }
+#endif
 
         /* tail is not big page (2M) alignment */
         start_pfn = pos>>PAGE_SHIFT;