[PATCH edk2-platforms v2 2/4] SbsaQemu: add MM based UEFI secure boot support

["Masahisa Kojima" <masahisa.kojima@linaro.org>]

This implements support for UEFI secure boot on SbsaQemu using
the standalone MM framework. This moves all of the software handling
of the UEFI authenticated variable store into the standalone MM
context residing in a secure partition.

Secure variable storage is located at 0x01000000 in secure NOR Flash.

Non-secure shared memory between UEFI and standalone MM
is allocated at the top of DRAM.
DRAM size of SbsaQemu varies depends on the QEMU parameter,
the non-secure shared memory base address is passed from
trusted-firmware through the device tree "/reserved-memory" node.

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
---
 Platform/Qemu/SbsaQemu/SbsaQemu.dsc           | 43 +++++++---
 .../Qemu/SbsaQemu/SbsaQemuStandaloneMm.dsc    | 39 +++++++++
 Platform/Qemu/SbsaQemu/SbsaQemu.fdf           | 82 +++++++++++++++++--
 .../Qemu/SbsaQemu/SbsaQemuStandaloneMm.fdf    |  7 +-
 .../Library/SbsaQemuLib/SbsaQemuLib.inf       |  2 +
 .../Library/SbsaQemuLib/SbsaQemuMem.c         | 37 ++++++++-
 6 files changed, 190 insertions(+), 20 deletions(-)

diff --git a/Platform/Qemu/SbsaQemu/SbsaQemu.dsc b/Platform/Qemu/SbsaQemu/SbsaQemu.dsc
index c1f8a4696560..a75116ee70fc 100644
--- a/Platform/Qemu/SbsaQemu/SbsaQemu.dsc
+++ b/Platform/Qemu/SbsaQemu/SbsaQemu.dsc
@@ -28,6 +28,8 @@ [Defines]
 
   DEFINE DEBUG_PRINT_ERROR_LEVEL = 0x8000004F
 
+  DEFINE SECURE_BOOT_ENABLE      = FALSE
+
 #
 # Network definition
 #
@@ -152,12 +154,10 @@ [LibraryClasses.common]
   # Secure Boot dependencies
   #
   TpmMeasurementLib|SecurityPkg/Library/DxeTpmMeasurementLib/DxeTpmMeasurementLib.inf
-  AuthVariableLib|SecurityPkg/Library/AuthVariableLib/AuthVariableLib.inf
 
   # re-use the UserPhysicalPresent() dummy implementation from the ovmf tree
   PlatformSecureLib|OvmfPkg/Library/PlatformSecureLib/PlatformSecureLib.inf
 
-  VarCheckLib|MdeModulePkg/Library/VarCheckLib/VarCheckLib.inf
   VariablePolicyLib|MdeModulePkg/Library/VariablePolicyLib/VariablePolicyLib.inf
   VariablePolicyHelperLib|MdeModulePkg/Library/VariablePolicyHelperLib/VariablePolicyHelperLib.inf
 
@@ -171,6 +171,7 @@ [LibraryClasses.common]
   ArmPlatformLib|ArmPlatformPkg/Library/ArmPlatformLibNull/ArmPlatformLibNull.inf
 
   TimerLib|ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.inf
+
   NorFlashPlatformLib|Silicon/Qemu/SbsaQemu/Library/SbsaQemuNorFlashLib/SbsaQemuNorFlashLib.inf
 
   CapsuleLib|MdeModulePkg/Library/DxeCapsuleLibNull/DxeCapsuleLibNull.inf
@@ -300,6 +301,8 @@ [PcdsFeatureFlag.common]
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE
 
+  gEfiMdeModulePkgTokenSpaceGuid.PcdEnableVariableRuntimeCache|FALSE
+
 [PcdsFixedAtBuild.common]
   gEfiMdePkgTokenSpaceGuid.PcdMaximumUnicodeStringLength|1000000
   gEfiMdePkgTokenSpaceGuid.PcdMaximumAsciiStringLength|1000000
@@ -551,6 +554,9 @@ [PcdsDynamicDefault.common]
   gArmVirtSbsaQemuPlatformTokenSpaceGuid.PcdChassisAssetTag|L"AT0000"
   gArmVirtSbsaQemuPlatformTokenSpaceGuid.PcdChassisSKU|L"SK0000"
 
+  gArmTokenSpaceGuid.PcdMmBufferBase|0x10000000000
+  gArmTokenSpaceGuid.PcdMmBufferSize|0x00200000
+
 ################################################################################
 #
 # Components Section - list of all EDK II Modules needed by this Platform
@@ -604,7 +610,6 @@ [Components.common]
   ArmPlatformPkg/MemoryInitPei/MemoryInitPeim.inf
   ArmPkg/Drivers/CpuPei/CpuPei.inf
 
-
   MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf {
     <LibraryClasses>
       NULL|MdeModulePkg/Library/LzmaCustomDecompressLib/LzmaCustomDecompressLib.inf
@@ -628,24 +633,40 @@ [Components.common]
   #
   ArmPkg/Drivers/CpuDxe/CpuDxe.inf
   MdeModulePkg/Core/RuntimeDxe/RuntimeDxe.inf
-  MdeModulePkg/Universal/Variable/RuntimeDxe/VariableRuntimeDxe.inf {
-    <LibraryClasses>
-      NULL|MdeModulePkg/Library/VarCheckUefiLib/VarCheckUefiLib.inf
-      # don't use unaligned CopyMem () on the UEFI varstore NOR flash region
-      BaseMemoryLib|MdePkg/Library/BaseMemoryLib/BaseMemoryLib.inf
-  }
   MdeModulePkg/Universal/SecurityStubDxe/SecurityStubDxe.inf {
     <LibraryClasses>
+!if $(SECURE_BOOT_ENABLE) == TRUE
       NULL|SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.inf
+!endif
   }
-  SecurityPkg/VariableAuthenticated/SecureBootConfigDxe/SecureBootConfigDxe.inf
   MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleRuntimeDxe.inf
-  MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteDxe.inf
   MdeModulePkg/Universal/MonotonicCounterRuntimeDxe/MonotonicCounterRuntimeDxe.inf
   MdeModulePkg/Universal/ResetSystemRuntimeDxe/ResetSystemRuntimeDxe.inf
   EmbeddedPkg/RealTimeClockRuntimeDxe/RealTimeClockRuntimeDxe.inf
   EmbeddedPkg/MetronomeDxe/MetronomeDxe.inf
 
+  #
+  # Variable services
+  #
+!if $(SECURE_BOOT_ENABLE) == FALSE
+  MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteDxe.inf
+  MdeModulePkg/Universal/Variable/RuntimeDxe/VariableRuntimeDxe.inf {
+    <LibraryClasses>
+      NULL|MdeModulePkg/Library/VarCheckUefiLib/VarCheckUefiLib.inf
+      AuthVariableLib|MdeModulePkg/Library/AuthVariableLibNull/AuthVariableLibNull.inf
+      VarCheckLib|MdeModulePkg/Library/VarCheckLib/VarCheckLib.inf
+      # don't use unaligned CopyMem () on the UEFI varstore NOR flash region
+      BaseMemoryLib|MdePkg/Library/BaseMemoryLib/BaseMemoryLib.inf
+  }
+!else
+  ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.inf {
+    <LibraryClasses>
+      NULL|StandaloneMmPkg/Library/VariableMmDependency/VariableMmDependency.inf
+  }
+  MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeDxe.inf
+  SecurityPkg/VariableAuthenticated/SecureBootConfigDxe/SecureBootConfigDxe.inf
+!endif
+
   MdeModulePkg/Universal/Console/ConPlatformDxe/ConPlatformDxe.inf
   MdeModulePkg/Universal/Console/ConSplitterDxe/ConSplitterDxe.inf
   MdeModulePkg/Universal/Console/GraphicsConsoleDxe/GraphicsConsoleDxe.inf
diff --git a/Platform/Qemu/SbsaQemu/SbsaQemuStandaloneMm.dsc b/Platform/Qemu/SbsaQemu/SbsaQemuStandaloneMm.dsc
index 87f5ee351eaa..b80379acd1ad 100644
--- a/Platform/Qemu/SbsaQemu/SbsaQemuStandaloneMm.dsc
+++ b/Platform/Qemu/SbsaQemu/SbsaQemuStandaloneMm.dsc
@@ -77,6 +77,18 @@ [LibraryClasses.common.MM_STANDALONE]
   HobLib|StandaloneMmPkg/Library/StandaloneMmHobLib/StandaloneMmHobLib.inf
   MmServicesTableLib|MdePkg/Library/StandaloneMmServicesTableLib/StandaloneMmServicesTableLib.inf
   MemoryAllocationLib|StandaloneMmPkg/Library/StandaloneMmMemoryAllocationLib/StandaloneMmMemoryAllocationLib.inf
+  AuthVariableLib|SecurityPkg/Library/AuthVariableLib/AuthVariableLib.inf
+  BaseCryptLib|CryptoPkg/Library/BaseCryptLib/SmmCryptLib.inf
+  IntrinsicLib|CryptoPkg/Library/IntrinsicLib/IntrinsicLib.inf
+  NorFlashPlatformLib|Silicon/Qemu/SbsaQemu/Library/SbsaQemuNorFlashLib/SbsaQemuNorFlashLib.inf
+  OpensslLib|CryptoPkg/Library/OpensslLib/OpensslLib.inf
+  RngLib|MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.inf
+  PlatformSecureLib|SecurityPkg/Library/PlatformSecureLibNull/PlatformSecureLibNull.inf
+  SynchronizationLib|MdePkg/Library/BaseSynchronizationLib/BaseSynchronizationLib.inf
+  TimerLib|ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.inf
+  VarCheckLib|MdeModulePkg/Library/VarCheckLib/VarCheckLib.inf
+  SafeIntLib|MdePkg/Library/BaseSafeIntLib/BaseSafeIntLib.inf
+  ArmGenericTimerCounterLib|ArmPkg/Library/ArmGenericTimerPhyCounterLib/ArmGenericTimerPhyCounterLib.inf
 
 ################################################################################
 #
@@ -94,6 +106,20 @@ [PcdsFixedAtBuild]
 
   gEfiMdePkgTokenSpaceGuid.PcdMaximumGuidedExtractHandler|0x2
 
+  gArmTokenSpaceGuid.PcdFdBaseAddress|0x01000000
+  gArmTokenSpaceGuid.PcdFdSize|0x000C0000
+
+  gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000
+  gEfiSecurityPkgTokenSpaceGuid.PcdUserPhysicalPresence|TRUE
+  gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x2800
+
+  gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableBase|0x01000000
+  gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableSize|0x00040000
+  gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingBase|0x01040000
+  gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingSize|0x00040000
+  gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareBase|0x01080000
+  gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize|0x00040000
+
 ###################################################################################################
 #
 # Components Section - list of the modules and components that will be processed by compilation
@@ -118,6 +144,19 @@ [Components.common]
   #
   StandaloneMmPkg/Core/StandaloneMmCore.inf
   StandaloneMmPkg/Drivers/StandaloneMmCpu/AArch64/StandaloneMmCpu.inf
+  ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashStandaloneMm.inf
+  MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteStandaloneMm.inf
+
+  MdeModulePkg/Universal/Variable/RuntimeDxe/VariableStandaloneMm.inf {
+    <LibraryClasses>
+      DevicePathLib|MdePkg/Library/UefiDevicePathLib/UefiDevicePathLib.inf
+      NULL|MdeModulePkg/Library/VarCheckUefiLib/VarCheckUefiLib.inf
+      NULL|MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLibStandaloneMm.inf
+      # don't use unaligned CopyMem () on the UEFI varstore NOR flash region
+      BaseMemoryLib|MdePkg/Library/BaseMemoryLib/BaseMemoryLib.inf
+      VariablePolicyLib|MdeModulePkg/Library/VariablePolicyLib/VariablePolicyLib.inf
+      VariablePolicyHelperLib|MdeModulePkg/Library/VariablePolicyHelperLib/VariablePolicyHelperLib.inf
+  }
 
 ###################################################################################################
 #
diff --git a/Platform/Qemu/SbsaQemu/SbsaQemu.fdf b/Platform/Qemu/SbsaQemu/SbsaQemu.fdf
index b61ae1891233..a46a47063ccc 100644
--- a/Platform/Qemu/SbsaQemu/SbsaQemu.fdf
+++ b/Platform/Qemu/SbsaQemu/SbsaQemu.fdf
@@ -21,10 +21,10 @@
 
 [FD.SBSA_FLASH0]
 BaseAddress   = 0x00000000
-Size          = 0x00400000
+Size          = 0x01100000
 ErasePolarity = 1
 BlockSize     = 0x00001000
-NumBlocks     = 0x400
+NumBlocks     = 0x1100
 
 ################################################################################
 #
@@ -50,6 +50,66 @@ [FD.SBSA_FLASH0]
 0x00008000|0x00300000
 FILE = Platform/Qemu/Sbsa/fip.bin
 
+!if $(SECURE_BOOT_ENABLE)
+## Place for Secure Variables.
+# Must be aligned to Flash Block size 0x40000
+0x01000000|0x00040000
+gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableBase|gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableSize
+#NV_VARIABLE_STORE
+DATA = {
+  ## This is the EFI_FIRMWARE_VOLUME_HEADER
+  # ZeroVector []
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  # FileSystemGuid: gEfiSystemNvDataFvGuid         =
+  #   { 0xFFF12B8D, 0x7696, 0x4C8B,
+  #     { 0xA9, 0x85, 0x27, 0x47, 0x07, 0x5B, 0x4F, 0x50 }}
+  0x8D, 0x2B, 0xF1, 0xFF, 0x96, 0x76, 0x8B, 0x4C,
+  0xA9, 0x85, 0x27, 0x47, 0x07, 0x5B, 0x4F, 0x50,
+  # FvLength: 0xC0000
+  0x00, 0x00, 0x0C, 0x00, 0x00, 0x00, 0x00, 0x00,
+  # Signature "_FVH"       # Attributes
+  0x5f, 0x46, 0x56, 0x48, 0xff, 0xfe, 0x04, 0x00,
+  # HeaderLength # CheckSum # ExtHeaderOffset #Reserved #Revision
+  0x48, 0x00, 0x28, 0x09, 0x00, 0x00, 0x00, 0x02,
+  # Blockmap[0]: 0x3 Blocks * 0x40000 Bytes / Block
+  0x3, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00,
+  # Blockmap[1]: End
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  ## This is the VARIABLE_STORE_HEADER
+  # It is compatible with SECURE_BOOT_ENABLE == FALSE as well.
+  # Signature: gEfiAuthenticatedVariableGuid =
+  #   { 0xaaf32c78, 0x947b, 0x439a,
+  #     { 0xa1, 0x80, 0x2e, 0x14, 0x4e, 0xc3, 0x77, 0x92 }}
+  0x78, 0x2c, 0xf3, 0xaa, 0x7b, 0x94, 0x9a, 0x43,
+  0xa1, 0x80, 0x2e, 0x14, 0x4e, 0xc3, 0x77, 0x92,
+  # Size: 0x40000 (gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableSize) -
+  #         0x48 (size of EFI_FIRMWARE_VOLUME_HEADER) = 0x3ffb8
+  # This can speed up the Variable Dispatch a bit.
+  0xB8, 0xFF, 0x03, 0x00,
+  # FORMATTED: 0x5A #HEALTHY: 0xFE #Reserved: UINT16 #Reserved1: UINT32
+  0x5A, 0xFE, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+}
+
+0x01040000|0x00040000
+gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingBase|gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingSize
+#NV_FTW_WORKING
+DATA = {
+  # EFI_FAULT_TOLERANT_WORKING_BLOCK_HEADER->Signature = gEdkiiWorkingBlockSignatureGuid         =
+  #  { 0x9e58292b, 0x7c68, 0x497d, { 0xa0, 0xce, 0x65,  0x0, 0xfd, 0x9f, 0x1b, 0x95 }}
+  0x2b, 0x29, 0x58, 0x9e, 0x68, 0x7c, 0x7d, 0x49,
+  0xa0, 0xce, 0x65,  0x0, 0xfd, 0x9f, 0x1b, 0x95,
+  # Crc:UINT32            #WorkingBlockValid:1, WorkingBlockInvalid:1, Reserved
+  0x5b, 0xe7, 0xc6, 0x86, 0xFE, 0xFF, 0xFF, 0xFF,
+  # WriteQueueSize: UINT64
+  0xE0, 0xFF, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00
+}
+
+0x01080000|0x00040000
+gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareBase|gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize
+#NV_FTW_SPARE
+!endif
+
 ################################################################################
 #
 # FD Section for FLASH1
@@ -169,15 +229,25 @@ [FV.FvMain]
   INF MdeModulePkg/Core/RuntimeDxe/RuntimeDxe.inf
   INF MdeModulePkg/Universal/SecurityStubDxe/SecurityStubDxe.inf
   INF MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleRuntimeDxe.inf
-  INF MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteDxe.inf
-  INF MdeModulePkg/Universal/Variable/RuntimeDxe/VariableRuntimeDxe.inf
-  INF SecurityPkg/VariableAuthenticated/SecureBootConfigDxe/SecureBootConfigDxe.inf
   INF MdeModulePkg/Universal/MonotonicCounterRuntimeDxe/MonotonicCounterRuntimeDxe.inf
   INF MdeModulePkg/Universal/ResetSystemRuntimeDxe/ResetSystemRuntimeDxe.inf
   INF EmbeddedPkg/RealTimeClockRuntimeDxe/RealTimeClockRuntimeDxe.inf
   INF EmbeddedPkg/MetronomeDxe/MetronomeDxe.inf
   INF MdeModulePkg/Universal/HiiDatabaseDxe/HiiDatabaseDxe.inf
 
+  #
+  # Variable services
+  #
+!if $(SECURE_BOOT_ENABLE) == FALSE
+  INF ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashDxe.inf
+  INF MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteDxe.inf
+  INF MdeModulePkg/Universal/Variable/RuntimeDxe/VariableRuntimeDxe.inf
+!else
+  INF ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.inf
+  INF MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeDxe.inf
+  INF SecurityPkg/VariableAuthenticated/SecureBootConfigDxe/SecureBootConfigDxe.inf
+!endif
+
   #
   # Multiple Console IO support
   #
@@ -189,7 +259,6 @@ [FV.FvMain]
 
   INF ArmPkg/Drivers/ArmGic/ArmGicDxe.inf
   INF ArmPkg/Drivers/TimerDxe/TimerDxe.inf
-  INF ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashDxe.inf
   INF MdeModulePkg/Universal/WatchdogTimerDxe/WatchdogTimer.inf
 
   #
@@ -294,6 +363,7 @@ [FV.FVMAIN_COMPACT]
   INF ArmPlatformPkg/MemoryInitPei/MemoryInitPeim.inf
   INF ArmPkg/Drivers/CpuPei/CpuPei.inf
   INF MdeModulePkg/Universal/PCD/Pei/Pcd.inf
+
   INF MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf
 
   # IDE/AHCI Support
diff --git a/Platform/Qemu/SbsaQemu/SbsaQemuStandaloneMm.fdf b/Platform/Qemu/SbsaQemu/SbsaQemuStandaloneMm.fdf
index a1acefcfb0a7..dbe1555c68f2 100644
--- a/Platform/Qemu/SbsaQemu/SbsaQemuStandaloneMm.fdf
+++ b/Platform/Qemu/SbsaQemu/SbsaQemuStandaloneMm.fdf
@@ -19,8 +19,8 @@
 ################################################################################
 
 [FD.STANDALONE_MM]
-BaseAddress   = 0x20001000|gArmTokenSpaceGuid.PcdFdBaseAddress
-Size          = 0x00e00000|gArmTokenSpaceGuid.PcdFdSize # The size in bytes of the device (14MiB).
+BaseAddress   = 0x20002000
+Size          = 0x00e00000
 ErasePolarity = 1
 
 BlockSize     = 0x00001000
@@ -49,6 +49,9 @@ [FV.FVMAIN_COMPACT]
 READ_LOCK_STATUS   = TRUE
 
   INF StandaloneMmPkg/Core/StandaloneMmCore.inf
+  INF ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashStandaloneMm.inf
+  INF MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteStandaloneMm.inf
+  INF MdeModulePkg/Universal/Variable/RuntimeDxe/VariableStandaloneMm.inf
   INF StandaloneMmPkg/Drivers/StandaloneMmCpu/AArch64/StandaloneMmCpu.inf
 
 ################################################################################
diff --git a/Silicon/Qemu/SbsaQemu/Library/SbsaQemuLib/SbsaQemuLib.inf b/Silicon/Qemu/SbsaQemu/Library/SbsaQemuLib/SbsaQemuLib.inf
index c067a80cc715..1d7f12202ecc 100644
--- a/Silicon/Qemu/SbsaQemu/Library/SbsaQemuLib/SbsaQemuLib.inf
+++ b/Silicon/Qemu/SbsaQemu/Library/SbsaQemuLib/SbsaQemuLib.inf
@@ -40,6 +40,8 @@ [Pcd]
   gArmTokenSpaceGuid.PcdSystemMemoryBase
   gArmTokenSpaceGuid.PcdSystemMemorySize
   gArmVirtSbsaQemuPlatformTokenSpaceGuid.PcdDeviceTreeBaseAddress
+  gArmTokenSpaceGuid.PcdMmBufferBase
+  gArmTokenSpaceGuid.PcdMmBufferSize
 
 [FixedPcd]
   gArmTokenSpaceGuid.PcdFdBaseAddress
diff --git a/Silicon/Qemu/SbsaQemu/Library/SbsaQemuLib/SbsaQemuMem.c b/Silicon/Qemu/SbsaQemu/Library/SbsaQemuLib/SbsaQemuMem.c
index 8c2eb0b6a028..fa164ff455f5 100644
--- a/Silicon/Qemu/SbsaQemu/Library/SbsaQemuLib/SbsaQemuMem.c
+++ b/Silicon/Qemu/SbsaQemu/Library/SbsaQemuLib/SbsaQemuMem.c
@@ -25,15 +25,20 @@ SbsaQemuLibConstructor (
 {
   VOID          *DeviceTreeBase;
   INT32         Node, Prev;
-  UINT64        NewBase, CurBase;
+  UINT64        NewBase, CurBase, NsBufBase;
   UINT64        NewSize, CurSize;
+  UINT32        NsBufSize;
   CONST CHAR8   *Type;
   INT32         Len;
   CONST UINT64  *RegProp;
   RETURN_STATUS PcdStatus;
+  INT32         ParentOffset;
+  INT32         Offset;
 
   NewBase = 0;
   NewSize = 0;
+  NsBufBase = 0;
+  NsBufSize = 0;
 
   DeviceTreeBase = (VOID *)(UINTN)PcdGet64 (PcdDeviceTreeBaseAddress);
   ASSERT (DeviceTreeBase != NULL);
@@ -73,9 +78,39 @@ SbsaQemuLibConstructor (
     }
   }
 
+  // StandaloneMM non-secure shared buffer is allocated at the top of
+  // the system memory by trusted-firmware using "/reserved-memory" node.
+  ParentOffset = fdt_path_offset(DeviceTreeBase, "/reserved-memory");
+  if (ParentOffset < 0) {
+    DEBUG ((DEBUG_ERROR, "%a: reserved-memory node not found\n",
+      __FUNCTION__));
+  }
+  Offset = fdt_subnode_offset(DeviceTreeBase, ParentOffset, "ns-buf-spm-mm");
+  if (Offset < 0) {
+    DEBUG ((DEBUG_ERROR, "%a: ns-buf-spm-mm node not found\n",
+      __FUNCTION__));
+  }
+  // Get the 'reg' property of this node. 8 byte quantities for base address
+  // and 4 byte quantities for size.
+  RegProp = fdt_getprop (DeviceTreeBase, Offset, "reg", &Len);
+  if (RegProp != 0 && Len == (sizeof (UINT64) + sizeof(UINT32))) {
+    NsBufBase = fdt64_to_cpu (ReadUnaligned64 (RegProp));
+    NsBufSize = fdt32_to_cpu (ReadUnaligned32 ((UINT32 *)(RegProp + 1)));
+
+    DEBUG ((DEBUG_INFO, "%a: ns buf @ 0x%lx - 0x%lx\n",
+      __FUNCTION__, NsBufBase, NsBufBase + NsBufSize - 1));
+  } else {
+    DEBUG ((DEBUG_ERROR, "%a: Failed to parse FDT reserved-memory node Len %d\n",
+      __FUNCTION__, Len));
+  }
+
+  NewSize -= NsBufSize;
+
   // Make sure the start of DRAM matches our expectation
   ASSERT (FixedPcdGet64 (PcdSystemMemoryBase) == NewBase);
   PcdStatus = PcdSet64S (PcdSystemMemorySize, NewSize);
+  PcdStatus = PcdSet64S (PcdMmBufferBase, NsBufBase);
+  PcdStatus = PcdSet64S (PcdMmBufferSize, (UINT64)NsBufSize);
   ASSERT_RETURN_ERROR (PcdStatus);
 
   return RETURN_SUCCESS;
-- 
2.17.1