From 1d4c17a6ef1a06023cb533d108556c419bdb1fed Mon Sep 17 00:00:00 2001
From: Star Zeng <star.zeng@intel.com>
Date: Wed, 17 Jan 2018 19:33:30 +0800
Subject: [PATCH 1/1] IntelSiliconPkg IntelVTdDxe: Fix DMA does not work issue

Fix DMA does not work issue when system memory is not
greater than 4G.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
---
 .../Feature/VTd/IntelVTdDxe/TranslationTable.c         | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/TranslationTable.c b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/TranslationTable.c
index cecb5d23ef..7bdc4a5146 100644
--- a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/TranslationTable.c
+++ b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/TranslationTable.c
@@ -286,9 +286,13 @@ CreateSecondLevelPagingEntry (
   if (SecondLevelPagingEntry == NULL) {
     return NULL;
   }
-  SecondLevelPagingEntry = CreateSecondLevelPagingEntryTable (VtdIndex, SecondLevelPagingEntry, SIZE_4GB, mAbove4GMemoryLimit, IoMmuAccess);
-  if (SecondLevelPagingEntry == NULL) {
-    return NULL;
+
+  if (mAbove4GMemoryLimit != 0) {
+    ASSERT (mAbove4GMemoryLimit > BASE_4GB);
+    SecondLevelPagingEntry = CreateSecondLevelPagingEntryTable (VtdIndex, SecondLevelPagingEntry, SIZE_4GB, mAbove4GMemoryLimit, IoMmuAccess);
+    if (SecondLevelPagingEntry == NULL) {
+      return NULL;
+    }
   }
 
   return SecondLevelPagingEntry;
-- 
2.39.2