From: Star Zeng <star.zeng@intel.com>
Date: Wed, 17 Jan 2018 11:33:30 +0000 (+0800)
Subject: IntelSiliconPkg IntelVTdDxe: Fix DMA does not work issue
X-Git-Tag: edk2-stable201903~2586
X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=commitdiff_plain;h=1d4c17a6ef1a06023cb533d108556c419bdb1fed

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>
---

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;