[PATCH 05/12] OvmfPkg/MemEncryptSevLib: Add an interface to retrieve the encryption mask

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

From: Tom Lendacky <thomas.lendacky@amd.com>

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3108

The early assembler code performs validation for some of the SEV-related
information, specifically the encryption bit position. To avoid having to
re-validate the encryption bit position as the system proceeds through its
boot phases, use the saved information from the SEV-ES work area during
PEI and PcdPteMemoryEncryptionAddressOrMask (set during PEI) during DXE.

To ensure that we always use a validated encryption mask for an SEV-ES
guest, create a new interface in the MemEncryptSevLib library to return
the encryption mask. This avoids the multiple locations where CPUID is
used to retrieve the value and allows the validated mask to be returned.

Update all locations that use CPUID to calculate the encryption mask to
use the new interface. Also, clean up some call areas where extra masking
was being performed and where a function call was being used instead of
the local variable that was just set using the function.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Rebecca Cran <rebecca@bsdio.com>
Cc: Peter Grehan <grehan@freebsd.org>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Julien Grall <julien@xen.org>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 OvmfPkg/AmdSev/AmdSevX64.dsc                  |   4 +-
 OvmfPkg/Bhyve/BhyveX64.dsc                    |   4 +-
 OvmfPkg/OvmfPkgIa32.dsc                       |   4 +-
 OvmfPkg/OvmfPkgIa32X64.dsc                    |   4 +-
 OvmfPkg/OvmfPkgX64.dsc                        |   4 +-
 OvmfPkg/OvmfXen.dsc                           |   3 +-
 ...SevLib.inf => DxeBaseMemEncryptSevLib.inf} |  13 +-
 .../PeiBaseMemEncryptSevLib.inf               |  56 ++++++
 OvmfPkg/Include/Library/MemEncryptSevLib.h    |  14 ++
 OvmfPkg/Bhyve/PlatformPei/AmdSev.c            |  12 +-
 .../DxeMemEncryptSevLibInternal.c             | 145 ++++++++++++++++
 .../MemEncryptSevLibInternal.c                |  91 +---------
 .../PeiMemEncryptSevLibInternal.c             | 159 ++++++++++++++++++
 .../BaseMemEncryptSevLib/X64/VirtualMemory.c  |  15 +-
 OvmfPkg/PlatformPei/AmdSev.c                  |  12 +-
 OvmfPkg/XenPlatformPei/AmdSev.c               |  12 +-
 OvmfPkg/ResetVector/Ia32/PageTables64.asm     |  10 +-
 OvmfPkg/ResetVector/ResetVector.nasmb         |   1 +
 18 files changed, 422 insertions(+), 141 deletions(-)
 rename OvmfPkg/Library/BaseMemEncryptSevLib/{BaseMemEncryptSevLib.inf => DxeBaseMemEncryptSevLib.inf} (67%)
 create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/PeiBaseMemEncryptSevLib.inf
 create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c
 create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c

diff --git a/OvmfPkg/AmdSev/AmdSevX64.dsc b/OvmfPkg/AmdSev/AmdSevX64.dsc
index bb7697eb324b..c742ec54cb57 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.dsc
+++ b/OvmfPkg/AmdSev/AmdSevX64.dsc
@@ -164,7 +164,7 @@ [LibraryClasses]
   QemuFwCfgSimpleParserLib|OvmfPkg/Library/QemuFwCfgSimpleParserLib/QemuFwCfgSimpleParserLib.inf
   VirtioLib|OvmfPkg/Library/VirtioLib/VirtioLib.inf
   LoadLinuxLib|OvmfPkg/Library/LoadLinuxLib/LoadLinuxLib.inf
-  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/DxeBaseMemEncryptSevLib.inf
   LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
   CustomizedDisplayLib|MdeModulePkg/Library/CustomizedDisplayLib/CustomizedDisplayLib.inf
   FrameBufferBltLib|MdeModulePkg/Library/FrameBufferBltLib/FrameBufferBltLib.inf
@@ -285,6 +285,8 @@ [LibraryClasses.common.PEIM]
   Tpm2DeviceLib|SecurityPkg/Library/Tpm2DeviceLibDTpm/Tpm2DeviceLibDTpm.inf
 !endif
 
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/PeiBaseMemEncryptSevLib.inf
+
 [LibraryClasses.common.DXE_CORE]
   HobLib|MdePkg/Library/DxeCoreHobLib/DxeCoreHobLib.inf
   DxeCoreEntryPoint|MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf
diff --git a/OvmfPkg/Bhyve/BhyveX64.dsc b/OvmfPkg/Bhyve/BhyveX64.dsc
index b93fe30ae4e0..27973bc940d5 100644
--- a/OvmfPkg/Bhyve/BhyveX64.dsc
+++ b/OvmfPkg/Bhyve/BhyveX64.dsc
@@ -163,7 +163,7 @@ [LibraryClasses]
   QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/BaseQemuFwCfgS3LibNull.inf
   BhyveFwCtlLib|OvmfPkg/Library/BhyveFwCtlLib/BhyveFwCtlLib.inf
   VirtioLib|OvmfPkg/Library/VirtioLib/VirtioLib.inf
-  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/DxeBaseMemEncryptSevLib.inf
   LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
 
   CustomizedDisplayLib|MdeModulePkg/Library/CustomizedDisplayLib/CustomizedDisplayLib.inf
@@ -292,6 +292,8 @@ [LibraryClasses.common.PEIM]
   Tpm2DeviceLib|SecurityPkg/Library/Tpm2DeviceLibDTpm/Tpm2DeviceLibDTpm.inf
 !endif
 
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/PeiBaseMemEncryptSevLib.inf
+
 [LibraryClasses.common.DXE_CORE]
   HobLib|MdePkg/Library/DxeCoreHobLib/DxeCoreHobLib.inf
   DxeCoreEntryPoint|MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf
diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index 8eede796a8bd..e433e17dc807 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -169,7 +169,7 @@ [LibraryClasses]
   QemuFwCfgSimpleParserLib|OvmfPkg/Library/QemuFwCfgSimpleParserLib/QemuFwCfgSimpleParserLib.inf
   VirtioLib|OvmfPkg/Library/VirtioLib/VirtioLib.inf
   LoadLinuxLib|OvmfPkg/Library/LoadLinuxLib/LoadLinuxLib.inf
-  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/DxeBaseMemEncryptSevLib.inf
 !if $(SMM_REQUIRE) == FALSE
   LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
 !endif
@@ -309,6 +309,8 @@ [LibraryClasses.common.PEIM]
   Tpm2DeviceLib|SecurityPkg/Library/Tpm2DeviceLibDTpm/Tpm2DeviceLibDTpm.inf
 !endif
 
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/PeiBaseMemEncryptSevLib.inf
+
 [LibraryClasses.common.DXE_CORE]
   HobLib|MdePkg/Library/DxeCoreHobLib/DxeCoreHobLib.inf
   DxeCoreEntryPoint|MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index f9f82a48f4b9..2e2eefbe33f0 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -173,7 +173,7 @@ [LibraryClasses]
   QemuFwCfgSimpleParserLib|OvmfPkg/Library/QemuFwCfgSimpleParserLib/QemuFwCfgSimpleParserLib.inf
   VirtioLib|OvmfPkg/Library/VirtioLib/VirtioLib.inf
   LoadLinuxLib|OvmfPkg/Library/LoadLinuxLib/LoadLinuxLib.inf
-  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/DxeBaseMemEncryptSevLib.inf
 !if $(SMM_REQUIRE) == FALSE
   LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
 !endif
@@ -313,6 +313,8 @@ [LibraryClasses.common.PEIM]
   Tpm2DeviceLib|SecurityPkg/Library/Tpm2DeviceLibDTpm/Tpm2DeviceLibDTpm.inf
 !endif
 
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/PeiBaseMemEncryptSevLib.inf
+
 [LibraryClasses.common.DXE_CORE]
   HobLib|MdePkg/Library/DxeCoreHobLib/DxeCoreHobLib.inf
   DxeCoreEntryPoint|MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index e59ae05b73aa..3e008855fbc1 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -173,7 +173,7 @@ [LibraryClasses]
   QemuFwCfgSimpleParserLib|OvmfPkg/Library/QemuFwCfgSimpleParserLib/QemuFwCfgSimpleParserLib.inf
   VirtioLib|OvmfPkg/Library/VirtioLib/VirtioLib.inf
   LoadLinuxLib|OvmfPkg/Library/LoadLinuxLib/LoadLinuxLib.inf
-  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/DxeBaseMemEncryptSevLib.inf
 !if $(SMM_REQUIRE) == FALSE
   LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
 !endif
@@ -313,6 +313,8 @@ [LibraryClasses.common.PEIM]
   Tpm2DeviceLib|SecurityPkg/Library/Tpm2DeviceLibDTpm/Tpm2DeviceLibDTpm.inf
 !endif
 
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/PeiBaseMemEncryptSevLib.inf
+
 [LibraryClasses.common.DXE_CORE]
   HobLib|MdePkg/Library/DxeCoreHobLib/DxeCoreHobLib.inf
   DxeCoreEntryPoint|MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf
diff --git a/OvmfPkg/OvmfXen.dsc b/OvmfPkg/OvmfXen.dsc
index 12b7a87ee877..44fae364b423 100644
--- a/OvmfPkg/OvmfXen.dsc
+++ b/OvmfPkg/OvmfXen.dsc
@@ -161,7 +161,7 @@ [LibraryClasses]
   SerializeVariablesLib|OvmfPkg/Library/SerializeVariablesLib/SerializeVariablesLib.inf
   QemuFwCfgLib|OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
   QemuLoadImageLib|OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf
-  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/DxeBaseMemEncryptSevLib.inf
   LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
   CustomizedDisplayLib|MdeModulePkg/Library/CustomizedDisplayLib/CustomizedDisplayLib.inf
   FrameBufferBltLib|MdeModulePkg/Library/FrameBufferBltLib/FrameBufferBltLib.inf
@@ -273,6 +273,7 @@ [LibraryClasses.common.PEIM]
   QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/PeiQemuFwCfgS3LibFwCfg.inf
   PcdLib|MdePkg/Library/PeiPcdLib/PeiPcdLib.inf
   QemuFwCfgLib|OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
+  MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/PeiBaseMemEncryptSevLib.inf
 
 [LibraryClasses.common.DXE_CORE]
   HobLib|MdePkg/Library/DxeCoreHobLib/DxeCoreHobLib.inf
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf b/OvmfPkg/Library/BaseMemEncryptSevLib/DxeBaseMemEncryptSevLib.inf
similarity index 67%
rename from OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
rename to OvmfPkg/Library/BaseMemEncryptSevLib/DxeBaseMemEncryptSevLib.inf
index 7c44d0952815..2be6ca1fa737 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/DxeBaseMemEncryptSevLib.inf
@@ -1,7 +1,7 @@
 ## @file
 #  Library provides the helper functions for SEV guest
 #
-# Copyright (c) 2017 Advanced Micro Devices. All rights reserved.<BR>
+# Copyright (c) 2017 - 2020, Advanced Micro Devices. All rights reserved.<BR>
 #
 #  SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -10,11 +10,11 @@
 
 [Defines]
   INF_VERSION                    = 1.25
-  BASE_NAME                      = MemEncryptSevLib
+  BASE_NAME                      = DxeMemEncryptSevLib
   FILE_GUID                      = c1594631-3888-4be4-949f-9c630dbc842b
   MODULE_TYPE                    = BASE
   VERSION_STRING                 = 1.0
-  LIBRARY_CLASS                  = MemEncryptSevLib|PEIM DXE_DRIVER DXE_RUNTIME_DRIVER DXE_SMM_DRIVER UEFI_DRIVER
+  LIBRARY_CLASS                  = MemEncryptSevLib|DXE_DRIVER DXE_RUNTIME_DRIVER DXE_SMM_DRIVER UEFI_DRIVER
 
 #
 # The following information is for reference only and not required by the build
@@ -30,14 +30,16 @@ [Packages]
   UefiCpuPkg/UefiCpuPkg.dec
 
 [Sources.X64]
+  DxeMemEncryptSevLibInternal.c
   MemEncryptSevLibInternal.c
   X64/MemEncryptSevLib.c
   X64/VirtualMemory.c
   X64/VirtualMemory.h
 
 [Sources.IA32]
+  DxeMemEncryptSevLibInternal.c
+  MemEncryptSevLibInternal.c
   Ia32/MemEncryptSevLib.c
-  MemEncryptSevLibInternal.c
 
 [LibraryClasses]
   BaseLib
@@ -49,3 +51,6 @@ [LibraryClasses]
 
 [FeaturePcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire
+
+[Pcd]
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiBaseMemEncryptSevLib.inf b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiBaseMemEncryptSevLib.inf
new file mode 100644
index 000000000000..7bdf8cb5210d
--- /dev/null
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiBaseMemEncryptSevLib.inf
@@ -0,0 +1,56 @@
+## @file
+#  Library provides the helper functions for SEV guest
+#
+# Copyright (c) 2020 Advanced Micro Devices. All rights reserved.<BR>
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+#
+##
+
+[Defines]
+  INF_VERSION                    = 1.25
+  BASE_NAME                      = PeiMemEncryptSevLib
+  FILE_GUID                      = 15d9a694-3d2a-4184-9672-ba55c3070e07
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = MemEncryptSevLib|PEIM
+
+#
+# The following information is for reference only and not required by the build
+# tools.
+#
+# VALID_ARCHITECTURES           = IA32 X64
+#
+
+[Packages]
+  MdeModulePkg/MdeModulePkg.dec
+  MdePkg/MdePkg.dec
+  OvmfPkg/OvmfPkg.dec
+  UefiCpuPkg/UefiCpuPkg.dec
+
+[Sources.X64]
+  PeiMemEncryptSevLibInternal.c
+  MemEncryptSevLibInternal.c
+  X64/MemEncryptSevLib.c
+  X64/VirtualMemory.c
+  X64/VirtualMemory.h
+
+[Sources.IA32]
+  PeiMemEncryptSevLibInternal.c
+  MemEncryptSevLibInternal.c
+  Ia32/MemEncryptSevLib.c
+
+[LibraryClasses]
+  BaseLib
+  CacheMaintenanceLib
+  CpuLib
+  DebugLib
+  MemoryAllocationLib
+  PcdLib
+
+[FeaturePcd]
+  gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire
+
+[FixedPcd]
+  gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase
diff --git a/OvmfPkg/Include/Library/MemEncryptSevLib.h b/OvmfPkg/Include/Library/MemEncryptSevLib.h
index dc09c61e58bb..394065f15bc1 100644
--- a/OvmfPkg/Include/Library/MemEncryptSevLib.h
+++ b/OvmfPkg/Include/Library/MemEncryptSevLib.h
@@ -29,6 +29,8 @@ typedef struct _SEC_SEV_ES_WORK_AREA {
   UINT8    Reserved1[7];
 
   UINT64   RandomData;
+
+  UINT64   EncryptionMask;
 } SEC_SEV_ES_WORK_AREA;
 
 /**
@@ -133,4 +135,16 @@ MemEncryptSevLocateInitialSmramSaveStateMapPages (
   OUT UINTN *BaseAddress,
   OUT UINTN *NumberOfPages
   );
+
+/**
+  Returns the SEV encryption mask.
+
+  @return  The SEV pagtable encryption mask
+**/
+UINT64
+EFIAPI
+MemEncryptSevGetEncryptionMask (
+  VOID
+  );
+
 #endif // _MEM_ENCRYPT_SEV_LIB_H_
diff --git a/OvmfPkg/Bhyve/PlatformPei/AmdSev.c b/OvmfPkg/Bhyve/PlatformPei/AmdSev.c
index e484f4b311fe..e3ed78581c1b 100644
--- a/OvmfPkg/Bhyve/PlatformPei/AmdSev.c
+++ b/OvmfPkg/Bhyve/PlatformPei/AmdSev.c
@@ -1,7 +1,7 @@
 /**@file
   Initialize Secure Encrypted Virtualization (SEV) support
 
-  Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
+  Copyright (c) 2017 - 2020, Advanced Micro Devices. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -15,8 +15,6 @@
 #include <Library/MemEncryptSevLib.h>
 #include <Library/PcdLib.h>
 #include <PiPei.h>
-#include <Register/Amd/Cpuid.h>
-#include <Register/Cpuid.h>
 #include <Register/Intel/SmramSaveStateMap.h>
 
 #include "Platform.h"
@@ -32,7 +30,6 @@ AmdSevInitialize (
   VOID
   )
 {
-  CPUID_MEMORY_ENCRYPTION_INFO_EBX  Ebx;
   UINT64                            EncryptionMask;
   RETURN_STATUS                     PcdStatus;
 
@@ -43,15 +40,10 @@ AmdSevInitialize (
     return;
   }
 
-  //
-  // CPUID Fn8000_001F[EBX] Bit 0:5 (memory encryption bit position)
-  //
-  AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, NULL, &Ebx.Uint32, NULL, NULL);
-  EncryptionMask = LShiftU64 (1, Ebx.Bits.PtePosBits);
-
   //
   // Set Memory Encryption Mask PCD
   //
+  EncryptionMask = MemEncryptSevGetEncryptionMask ();
   PcdStatus = PcdSet64S (PcdPteMemoryEncryptionAddressOrMask, EncryptionMask);
   ASSERT_RETURN_ERROR (PcdStatus);
 
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c
new file mode 100644
index 000000000000..2816f859a0c4
--- /dev/null
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c
@@ -0,0 +1,145 @@
+/** @file
+
+  Secure Encrypted Virtualization (SEV) library helper function
+
+  Copyright (c) 2017 - 2020, AMD Incorporated. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Library/BaseLib.h>
+#include <Library/DebugLib.h>
+#include <Library/MemEncryptSevLib.h>
+#include <Library/PcdLib.h>
+#include <Register/Amd/Cpuid.h>
+#include <Register/Amd/Msr.h>
+#include <Register/Cpuid.h>
+#include <Uefi/UefiBaseType.h>
+
+STATIC BOOLEAN mSevStatus = FALSE;
+STATIC BOOLEAN mSevEsStatus = FALSE;
+STATIC BOOLEAN mSevStatusChecked = FALSE;
+
+STATIC UINT64  mSevEncryptionMask = 0;
+STATIC BOOLEAN mSevEncryptionMaskSaved = FALSE;
+
+/**
+  Reads and sets the status of SEV features.
+
+  **/
+STATIC
+VOID
+EFIAPI
+InternalMemEncryptSevStatus (
+  VOID
+  )
+{
+  UINT32                            RegEax;
+  MSR_SEV_STATUS_REGISTER           Msr;
+  CPUID_MEMORY_ENCRYPTION_INFO_EAX  Eax;
+  BOOLEAN                           ReadSevMsr;
+  UINT64                            EncryptionMask;
+
+  ReadSevMsr = FALSE;
+
+  EncryptionMask = PcdGet64 (PcdPteMemoryEncryptionAddressOrMask);
+  if (EncryptionMask != 0) {
+    //
+    // The MSR has been read before, so it is safe to read it again and avoid
+    // having to validate the CPUID information.
+    //
+    ReadSevMsr = TRUE;
+  } else {
+    //
+    // Check if memory encryption leaf exist
+    //
+    AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
+    if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) {
+      //
+      // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported)
+      //
+      AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL, NULL);
+
+      if (Eax.Bits.SevBit) {
+        ReadSevMsr = TRUE;
+      }
+    }
+  }
+
+  if (ReadSevMsr) {
+    //
+    // Check MSR_0xC0010131 Bit 0 (Sev Enabled)
+    //
+    Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS);
+    if (Msr.Bits.SevBit) {
+      mSevStatus = TRUE;
+    }
+
+    //
+    // Check MSR_0xC0010131 Bit 1 (Sev-Es Enabled)
+    //
+    if (Msr.Bits.SevEsBit) {
+      mSevEsStatus = TRUE;
+    }
+  }
+
+  mSevStatusChecked = TRUE;
+}
+
+/**
+  Returns a boolean to indicate whether SEV-ES is enabled.
+
+  @retval TRUE           SEV-ES is enabled
+  @retval FALSE          SEV-ES is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevEsIsEnabled (
+  VOID
+  )
+{
+  if (!mSevStatusChecked) {
+    InternalMemEncryptSevStatus ();
+  }
+
+  return mSevEsStatus;
+}
+
+/**
+  Returns a boolean to indicate whether SEV is enabled.
+
+  @retval TRUE           SEV is enabled
+  @retval FALSE          SEV is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevIsEnabled (
+  VOID
+  )
+{
+  if (!mSevStatusChecked) {
+    InternalMemEncryptSevStatus ();
+  }
+
+  return mSevStatus;
+}
+
+/**
+  Returns the SEV encryption mask.
+
+  @return  The SEV pagtable encryption mask
+**/
+UINT64
+EFIAPI
+MemEncryptSevGetEncryptionMask (
+  VOID
+  )
+{
+  if (!mSevEncryptionMaskSaved) {
+    mSevEncryptionMask = PcdGet64 (PcdPteMemoryEncryptionAddressOrMask);
+    mSevEncryptionMaskSaved = TRUE;
+  }
+
+  return mSevEncryptionMask;
+}
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/MemEncryptSevLibInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/MemEncryptSevLibInternal.c
index 02b8eb225d81..ec6d02eaefd0 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/MemEncryptSevLibInternal.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/MemEncryptSevLibInternal.c
@@ -2,7 +2,7 @@
 
   Secure Encrypted Virtualization (SEV) library helper function
 
-  Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
+  Copyright (c) 2017 - 2020, AMD Incorporated. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -19,95 +19,6 @@
 #include <Register/SmramSaveStateMap.h>
 #include <Uefi/UefiBaseType.h>
 
-STATIC BOOLEAN mSevStatus = FALSE;
-STATIC BOOLEAN mSevEsStatus = FALSE;
-STATIC BOOLEAN mSevStatusChecked = FALSE;
-
-/**
-  Reads and sets the status of SEV features.
-
-  **/
-STATIC
-VOID
-EFIAPI
-InternalMemEncryptSevStatus (
-  VOID
-  )
-{
-  UINT32                            RegEax;
-  MSR_SEV_STATUS_REGISTER           Msr;
-  CPUID_MEMORY_ENCRYPTION_INFO_EAX  Eax;
-
-  //
-  // Check if memory encryption leaf exist
-  //
-  AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
-  if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) {
-    //
-    // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported)
-    //
-    AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL, NULL);
-
-    if (Eax.Bits.SevBit) {
-      //
-      // Check MSR_0xC0010131 Bit 0 (Sev Enabled)
-      //
-      Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS);
-      if (Msr.Bits.SevBit) {
-        mSevStatus = TRUE;
-      }
-
-      //
-      // Check MSR_0xC0010131 Bit 1 (Sev-Es Enabled)
-      //
-      if (Msr.Bits.SevEsBit) {
-        mSevEsStatus = TRUE;
-      }
-    }
-  }
-
-  mSevStatusChecked = TRUE;
-}
-
-/**
-  Returns a boolean to indicate whether SEV-ES is enabled.
-
-  @retval TRUE           SEV-ES is enabled
-  @retval FALSE          SEV-ES is not enabled
-**/
-BOOLEAN
-EFIAPI
-MemEncryptSevEsIsEnabled (
-  VOID
-  )
-{
-  if (!mSevStatusChecked) {
-    InternalMemEncryptSevStatus ();
-  }
-
-  return mSevEsStatus;
-}
-
-/**
-  Returns a boolean to indicate whether SEV is enabled.
-
-  @retval TRUE           SEV is enabled
-  @retval FALSE          SEV is not enabled
-**/
-BOOLEAN
-EFIAPI
-MemEncryptSevIsEnabled (
-  VOID
-  )
-{
-  if (!mSevStatusChecked) {
-    InternalMemEncryptSevStatus ();
-  }
-
-  return mSevStatus;
-}
-
-
 /**
   Locate the page range that covers the initial (pre-SMBASE-relocation) SMRAM
   Save State Map.
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c
new file mode 100644
index 000000000000..e2fd109d120f
--- /dev/null
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c
@@ -0,0 +1,159 @@
+/** @file
+
+  Secure Encrypted Virtualization (SEV) library helper function
+
+  Copyright (c) 2020, AMD Incorporated. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Library/BaseLib.h>
+#include <Library/DebugLib.h>
+#include <Library/MemEncryptSevLib.h>
+#include <Library/PcdLib.h>
+#include <Register/Amd/Cpuid.h>
+#include <Register/Amd/Msr.h>
+#include <Register/Cpuid.h>
+#include <Uefi/UefiBaseType.h>
+
+STATIC BOOLEAN mSevStatus = FALSE;
+STATIC BOOLEAN mSevEsStatus = FALSE;
+STATIC BOOLEAN mSevStatusChecked = FALSE;
+
+STATIC UINT64  mSevEncryptionMask = 0;
+STATIC BOOLEAN mSevEncryptionMaskSaved = FALSE;
+
+/**
+  Reads and sets the status of SEV features.
+
+  **/
+STATIC
+VOID
+EFIAPI
+InternalMemEncryptSevStatus (
+  VOID
+  )
+{
+  UINT32                            RegEax;
+  MSR_SEV_STATUS_REGISTER           Msr;
+  CPUID_MEMORY_ENCRYPTION_INFO_EAX  Eax;
+  BOOLEAN                           ReadSevMsr;
+  SEC_SEV_ES_WORK_AREA              *SevEsWorkArea;
+
+  ReadSevMsr = FALSE;
+
+  SevEsWorkArea = (SEC_SEV_ES_WORK_AREA *) FixedPcdGet32 (PcdSevEsWorkAreaBase);
+  if (SevEsWorkArea != NULL && SevEsWorkArea->EncryptionMask != 0) {
+    //
+    // The MSR has been read before, so it is safe to read it again and avoid
+    // having to validate the CPUID information.
+    //
+    ReadSevMsr = TRUE;
+  } else {
+    //
+    // Check if memory encryption leaf exist
+    //
+    AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
+    if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) {
+      //
+      // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported)
+      //
+      AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL, NULL);
+
+      if (Eax.Bits.SevBit) {
+        ReadSevMsr = TRUE;
+      }
+    }
+  }
+
+  if (ReadSevMsr) {
+    //
+    // Check MSR_0xC0010131 Bit 0 (Sev Enabled)
+    //
+    Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS);
+    if (Msr.Bits.SevBit) {
+      mSevStatus = TRUE;
+    }
+
+    //
+    // Check MSR_0xC0010131 Bit 1 (Sev-Es Enabled)
+    //
+    if (Msr.Bits.SevEsBit) {
+      mSevEsStatus = TRUE;
+    }
+  }
+
+  mSevStatusChecked = TRUE;
+}
+
+/**
+  Returns a boolean to indicate whether SEV-ES is enabled.
+
+  @retval TRUE           SEV-ES is enabled
+  @retval FALSE          SEV-ES is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevEsIsEnabled (
+  VOID
+  )
+{
+  if (!mSevStatusChecked) {
+    InternalMemEncryptSevStatus ();
+  }
+
+  return mSevEsStatus;
+}
+
+/**
+  Returns a boolean to indicate whether SEV is enabled.
+
+  @retval TRUE           SEV is enabled
+  @retval FALSE          SEV is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevIsEnabled (
+  VOID
+  )
+{
+  if (!mSevStatusChecked) {
+    InternalMemEncryptSevStatus ();
+  }
+
+  return mSevStatus;
+}
+
+/**
+  Returns the SEV encryption mask.
+
+  @return  The SEV pagtable encryption mask
+**/
+UINT64
+EFIAPI
+MemEncryptSevGetEncryptionMask (
+  VOID
+  )
+{
+  if (!mSevEncryptionMaskSaved) {
+    SEC_SEV_ES_WORK_AREA  *SevEsWorkArea;
+
+    SevEsWorkArea = (SEC_SEV_ES_WORK_AREA *) FixedPcdGet32 (PcdSevEsWorkAreaBase);
+    if (SevEsWorkArea != NULL) {
+      mSevEncryptionMask = SevEsWorkArea->EncryptionMask;
+    } else {
+      CPUID_MEMORY_ENCRYPTION_INFO_EBX  Ebx;
+
+      //
+      // CPUID Fn8000_001F[EBX] Bit 0:5 (memory encryption bit position)
+      //
+      AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, NULL, &Ebx.Uint32, NULL, NULL);
+      mSevEncryptionMask = LShiftU64 (1, Ebx.Bits.PtePosBits);
+    }
+
+    mSevEncryptionMaskSaved = TRUE;
+  }
+
+  return mSevEncryptionMask;
+}
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.c
index 5e110c84ff81..6422bc53bd5d 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.c
@@ -3,7 +3,7 @@
   Virtual Memory Management Services to set or clear the memory encryption bit
 
   Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
-  Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
+  Copyright (c) 2017 - 2020, AMD Incorporated. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -12,6 +12,7 @@
 **/
 
 #include <Library/CpuLib.h>
+#include <Library/MemEncryptSevLib.h>
 #include <Register/Amd/Cpuid.h>
 #include <Register/Cpuid.h>
 
@@ -39,17 +40,12 @@ GetMemEncryptionAddressMask (
   )
 {
   UINT64                            EncryptionMask;
-  CPUID_MEMORY_ENCRYPTION_INFO_EBX  Ebx;
 
   if (mAddressEncMaskChecked) {
     return mAddressEncMask;
   }
 
-  //
-  // CPUID Fn8000_001F[EBX] Bit 0:5 (memory encryption bit position)
-  //
-  AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, NULL, &Ebx.Uint32, NULL, NULL);
-  EncryptionMask = LShiftU64 (1, Ebx.Bits.PtePosBits);
+  EncryptionMask = MemEncryptSevGetEncryptionMask ();
 
   mAddressEncMask = EncryptionMask & PAGING_1G_ADDRESS_MASK_64;
   mAddressEncMaskChecked = TRUE;
@@ -289,8 +285,7 @@ SetPageTablePoolReadOnly (
   LevelSize[3] = SIZE_1GB;
   LevelSize[4] = SIZE_512GB;
 
-  AddressEncMask  = GetMemEncryptionAddressMask() &
-                    PAGING_1G_ADDRESS_MASK_64;
+  AddressEncMask  = GetMemEncryptionAddressMask();
   PageTable       = (UINT64 *)(UINTN)PageTableBase;
   PoolUnitSize    = PAGE_TABLE_POOL_UNIT_SIZE;
 
@@ -437,7 +432,7 @@ Split1GPageTo2M (
 
   AddressEncMask = GetMemEncryptionAddressMask ();
   ASSERT (PageDirectoryEntry != NULL);
-  ASSERT (*PageEntry1G & GetMemEncryptionAddressMask ());
+  ASSERT (*PageEntry1G & AddressEncMask);
   //
   // Fill in 1G page entry.
   //
diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
index 4a515a484720..954d53eba4e8 100644
--- a/OvmfPkg/PlatformPei/AmdSev.c
+++ b/OvmfPkg/PlatformPei/AmdSev.c
@@ -1,7 +1,7 @@
 /**@file
   Initialize Secure Encrypted Virtualization (SEV) support
 
-  Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
+  Copyright (c) 2017 - 2020, Advanced Micro Devices. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -17,9 +17,7 @@
 #include <Library/MemoryAllocationLib.h>
 #include <Library/PcdLib.h>
 #include <PiPei.h>
-#include <Register/Amd/Cpuid.h>
 #include <Register/Amd/Msr.h>
-#include <Register/Cpuid.h>
 #include <Register/Intel/SmramSaveStateMap.h>
 
 #include "Platform.h"
@@ -116,7 +114,6 @@ AmdSevInitialize (
   VOID
   )
 {
-  CPUID_MEMORY_ENCRYPTION_INFO_EBX  Ebx;
   UINT64                            EncryptionMask;
   RETURN_STATUS                     PcdStatus;
 
@@ -127,15 +124,10 @@ AmdSevInitialize (
     return;
   }
 
-  //
-  // CPUID Fn8000_001F[EBX] Bit 0:5 (memory encryption bit position)
-  //
-  AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, NULL, &Ebx.Uint32, NULL, NULL);
-  EncryptionMask = LShiftU64 (1, Ebx.Bits.PtePosBits);
-
   //
   // Set Memory Encryption Mask PCD
   //
+  EncryptionMask = MemEncryptSevGetEncryptionMask ();
   PcdStatus = PcdSet64S (PcdPteMemoryEncryptionAddressOrMask, EncryptionMask);
   ASSERT_RETURN_ERROR (PcdStatus);
 
diff --git a/OvmfPkg/XenPlatformPei/AmdSev.c b/OvmfPkg/XenPlatformPei/AmdSev.c
index 7ebbb5cc1fd2..4ed448632ae2 100644
--- a/OvmfPkg/XenPlatformPei/AmdSev.c
+++ b/OvmfPkg/XenPlatformPei/AmdSev.c
@@ -1,7 +1,7 @@
 /**@file
   Initialize Secure Encrypted Virtualization (SEV) support
 
-  Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
+  Copyright (c) 2017 - 2020, Advanced Micro Devices. All rights reserved.<BR>
   Copyright (c) 2019, Citrix Systems, Inc.
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
@@ -14,8 +14,6 @@
 #include <Library/MemEncryptSevLib.h>
 #include <Library/PcdLib.h>
 #include <PiPei.h>
-#include <Register/Amd/Cpuid.h>
-#include <Register/Cpuid.h>
 
 #include "Platform.h"
 
@@ -30,7 +28,6 @@ AmdSevInitialize (
   VOID
   )
 {
-  CPUID_MEMORY_ENCRYPTION_INFO_EBX  Ebx;
   UINT64                            EncryptionMask;
   RETURN_STATUS                     PcdStatus;
 
@@ -41,15 +38,10 @@ AmdSevInitialize (
     return;
   }
 
-  //
-  // CPUID Fn8000_001F[EBX] Bit 0:5 (memory encryption bit position)
-  //
-  AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, NULL, &Ebx.Uint32, NULL, NULL);
-  EncryptionMask = LShiftU64 (1, Ebx.Bits.PtePosBits);
-
   //
   // Set Memory Encryption Mask PCD
   //
+  EncryptionMask = MemEncryptSevGetEncryptionMask ();
   PcdStatus = PcdSet64S (PcdPteMemoryEncryptionAddressOrMask, EncryptionMask);
   ASSERT_RETURN_ERROR (PcdStatus);
 
diff --git a/OvmfPkg/ResetVector/Ia32/PageTables64.asm b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
index b08f31157cbf..8c0d432050df 100644
--- a/OvmfPkg/ResetVector/Ia32/PageTables64.asm
+++ b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
@@ -145,13 +145,21 @@ GetSevEncBit:
 
     ; The encryption bit position is always above 31
     sub       ebx, 32
-    jns       SevExit
+    jns       SevSaveMask
 
     ; Encryption bit was reported as 31 or below, enter a HLT loop
 SevEncBitLowHlt:
     hlt
     jmp       SevEncBitLowHlt
 
+SevSaveMask:
+    xor       edx, edx
+    bts       edx, ebx
+
+    mov       dword[SEV_ES_WORK_AREA_ENC_MASK], 0
+    mov       dword[SEV_ES_WORK_AREA_ENC_MASK + 4], edx
+    jmp       SevExit
+
 NoSev:
     ;
     ; Perform an SEV-ES sanity check by seeing if a #VC exception occurred.
diff --git a/OvmfPkg/ResetVector/ResetVector.nasmb b/OvmfPkg/ResetVector/ResetVector.nasmb
index d3aa87982959..5fbacaed5f9d 100644
--- a/OvmfPkg/ResetVector/ResetVector.nasmb
+++ b/OvmfPkg/ResetVector/ResetVector.nasmb
@@ -74,6 +74,7 @@
   %define GHCB_SIZE (FixedPcdGet32 (PcdOvmfSecGhcbSize))
   %define SEV_ES_WORK_AREA (FixedPcdGet32 (PcdSevEsWorkAreaBase))
   %define SEV_ES_WORK_AREA_RDRAND (FixedPcdGet32 (PcdSevEsWorkAreaBase) + 8)
+  %define SEV_ES_WORK_AREA_ENC_MASK (FixedPcdGet32 (PcdSevEsWorkAreaBase) + 16)
   %define SEV_ES_VC_TOP_OF_STACK (FixedPcdGet32 (PcdOvmfSecPeiTempRamBase) + FixedPcdGet32 (PcdOvmfSecPeiTempRamSize))
 %include "Ia32/Flat32ToFlat64.asm"
 %include "Ia32/PageTables64.asm"
-- 
2.28.0