diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
new file mode 100644
index 0000000000..e472096320
--- /dev/null
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
@@ -0,0 +1,75 @@
+/** @file
+
+  AMD Sev Dxe driver. This driver is dispatched early in DXE, due to being list
+  in APRIORI. It clears C-bit from MMIO and NonExistent Memory space when SEV is
+  enabled.
+
+  Copyright (c) 2017, AMD Inc. All rights reserved.<BR>
+
+  This program and the accompanying materials
+  are licensed and made available under the terms and conditions of the BSD
+  License which accompanies this distribution.  The full text of the license may
+  be found at http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+
+#include <PiDxe.h>
+
+#include <Library/BaseLib.h>
+#include <Library/DebugLib.h>
+#include <Library/BaseMemoryLib.h>
+#include <Library/MemoryAllocationLib.h>
+#include <Library/UefiBootServicesTableLib.h>
+#include <Library/DxeServicesTableLib.h>
+#include <Library/MemEncryptSevLib.h>
+
+EFI_STATUS
+EFIAPI
+AmdSevDxeEntryPoint (
+  IN EFI_HANDLE         ImageHandle,
+  IN EFI_SYSTEM_TABLE   *SystemTable
+  )
+{
+  EFI_STATUS                       Status;
+  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *AllDescMap;
+  UINTN                            NumEntries;
+  UINTN                            Index;
+
+  //
+  // Do nothing when SEV is not enabled
+  //
+  if (!MemEncryptSevIsEnabled ()) {
+    return EFI_UNSUPPORTED;
+  }
+
+  //
+  // Iterate through the GCD map and clear the C-bit from MMIO and NonExistent
+  // memory space. The NonExistent memory space will be used for mapping the MMIO
+  // space added later (eg PciRootBridge). By clearing both known MMIO and
+  // NonExistent memory space can gurantee that current and furture MMIO adds
+  // will have C-bit cleared.
+  //
+  Status = gDS->GetMemorySpaceMap (&NumEntries, &AllDescMap);
+  if (!EFI_ERROR (Status)) {
+    for (Index = 0; Index < NumEntries; Index++) {
+      CONST EFI_GCD_MEMORY_SPACE_DESCRIPTOR *Desc;
+
+      Desc = &AllDescMap[Index];
+      if (Desc->GcdMemoryType == EfiGcdMemoryTypeMemoryMappedIo ||
+          Desc->GcdMemoryType == EfiGcdMemoryTypeNonExistent) {
+        Status = MemEncryptSevClearPageEncMask (0,
+                                                Desc->BaseAddress,
+                                                EFI_SIZE_TO_PAGES(Desc->Length),
+                                                FALSE);
+        ASSERT_EFI_ERROR (Status);
+      }
+    }
+
+    FreePool (AllDescMap);
+  }
+
+  return EFI_SUCCESS;
+}
diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.inf b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
new file mode 100644
index 0000000000..41635a57a4
--- /dev/null
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
@@ -0,0 +1,43 @@
+#/** @file
+#
+#  Driver clears the encryption attribute from MMIO regions when SEV is enabled
+#
+#  Copyright (c) 2017, AMD Inc. All rights reserved.<BR>
+#
+#  This program and the accompanying materials
+#  are licensed and made available under the terms and conditions of the BSD
+#  License which accompanies this distribution.  The full text of the license may
+#  be found at http://opensource.org/licenses/bsd-license.php
+#
+#  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+#
+#**/
+
+[Defines]
+  INF_VERSION                    = 1.25
+  BASE_NAME                      = AmdSevDxe
+  FILE_GUID                      = 2ec9da37-ee35-4de9-86c5-6d9a81dc38a7
+  MODULE_TYPE                    = DXE_DRIVER
+  VERSION_STRING                 = 1.0
+  ENTRY_POINT                    = AmdSevDxeEntryPoint
+
+[Sources]
+  AmdSevDxe.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  MdeModulePkg/MdeModulePkg.dec
+  OvmfPkg/OvmfPkg.dec
+
+[LibraryClasses]
+  BaseLib
+  UefiLib
+  UefiDriverEntryPoint
+  UefiBootServicesTableLib
+  DxeServicesTableLib
+  DebugLib
+  MemEncryptSevLib
+
+[Depex]
+  TRUE
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index edacd655d1..b3a22c726b 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -825,6 +825,7 @@
 !endif
 
   OvmfPkg/PlatformDxe/Platform.inf
+  OvmfPkg/AmdSevDxe/AmdSevDxe.inf
 
 !if $(SMM_REQUIRE) == TRUE
   OvmfPkg/SmmAccess/SmmAccess2Dxe.inf
diff --git a/OvmfPkg/OvmfPkgIa32X64.fdf b/OvmfPkg/OvmfPkgIa32X64.fdf
index fae82709ae..5cec9982db 100644
--- a/OvmfPkg/OvmfPkgIa32X64.fdf
+++ b/OvmfPkg/OvmfPkgIa32X64.fdf
@@ -191,6 +191,7 @@ READ_LOCK_STATUS   = TRUE
 APRIORI DXE {
   INF  MdeModulePkg/Universal/DevicePathDxe/DevicePathDxe.inf
   INF  MdeModulePkg/Universal/PCD/Dxe/Pcd.inf
+  INF  OvmfPkg/AmdSevDxe/AmdSevDxe.inf
 !if $(SMM_REQUIRE) == FALSE
   INF  OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf
 !endif
@@ -352,6 +353,7 @@ INF  RuleOverride=CSM OvmfPkg/Csm/Csm16/Csm16.inf
 INF  OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
 INF  OvmfPkg/VirtioGpuDxe/VirtioGpu.inf
 INF  OvmfPkg/PlatformDxe/Platform.inf
+INF  OvmfPkg/AmdSevDxe/AmdSevDxe.inf
 
 !if $(SMM_REQUIRE) == TRUE
 INF  OvmfPkg/SmmAccess/SmmAccess2Dxe.inf
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 93933612a3..aba4d907b5 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -823,6 +823,7 @@
 !endif
 
   OvmfPkg/PlatformDxe/Platform.inf
+  OvmfPkg/AmdSevDxe/AmdSevDxe.inf
 
 !if $(SMM_REQUIRE) == TRUE
   OvmfPkg/SmmAccess/SmmAccess2Dxe.inf
diff --git a/OvmfPkg/OvmfPkgX64.fdf b/OvmfPkg/OvmfPkgX64.fdf
index 4da0b19b94..213db6bedb 100644
--- a/OvmfPkg/OvmfPkgX64.fdf
+++ b/OvmfPkg/OvmfPkgX64.fdf
@@ -191,6 +191,7 @@ READ_LOCK_STATUS   = TRUE
 APRIORI DXE {
   INF  MdeModulePkg/Universal/DevicePathDxe/DevicePathDxe.inf
   INF  MdeModulePkg/Universal/PCD/Dxe/Pcd.inf
+  INF  OvmfPkg/AmdSevDxe/AmdSevDxe.inf
 !if $(SMM_REQUIRE) == FALSE
   INF  OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf
 !endif
@@ -352,6 +353,7 @@ INF  RuleOverride=CSM OvmfPkg/Csm/Csm16/Csm16.inf
 INF  OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
 INF  OvmfPkg/VirtioGpuDxe/VirtioGpu.inf
 INF  OvmfPkg/PlatformDxe/Platform.inf
+INF  OvmfPkg/AmdSevDxe/AmdSevDxe.inf
 
 !if $(SMM_REQUIRE) == TRUE
 INF  OvmfPkg/SmmAccess/SmmAccess2Dxe.inf