Re: [PATCH v2 02/17] ArmPkg/Drivers: Add EFI_MM_COMMUNICATION_PROTOCOL DXE driver.

[Supreeth Venkatesh <supreeth.venkatesh@arm.com>]

On Wed, 2018-05-09 at 20:52 +0000, Udit Kumar wrote:
> 
> > 
> > -----Original Message-----
> > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf
> > Of
> > Supreeth Venkatesh
> > Sent: Saturday, May 5, 2018 2:11 AM
> > To: edk2-devel@lists.01.org
> > Cc: ard.biesheuvel@linaro.org; leif.lindholm@linaro.org; jiewen.yao
> > @intel.com;
> > liming.gao@intel.com; michael.d.kinney@intel.com
> > Subject: [edk2] [PATCH v2 02/17] ArmPkg/Drivers: Add
> > EFI_MM_COMMUNICATION_PROTOCOL DXE driver.
> > 
> > PI v1.5 Specification Volume 4 defines Management Mode Core
> > Interface
> > and defines EFI_MM_COMMUNICATION_PROTOCOL. This protocol provides a
> > means of communicating between drivers outside of MM and MMI
> > handlers inside of MM.
> > 
> > This patch implements the EFI_MM_COMMUNICATION_PROTOCOL DXE
> > runtime
> > driver for AARCH64 platforms. It uses SMCs allocated from the
> > standard
> > SMC range defined in DEN0060A_ARM_MM_Interface_Specification.pdf
> > to communicate with the standalone MM environment in the secure
> > world.
> > 
> > This patch also adds the MM Communication driver (.inf) file to
> > define entry point for this driver and other compile
> > related information the driver needs.
> > 
> > Contributed-under: TianoCore Contribution Agreement 1.1
> > Signed-off-by: Achin Gupta <achin.gupta@arm.com>
> > Signed-off-by: Supreeth Venkatesh <supreeth.venkatesh@arm.com>
> > ---
> >  .../Drivers/MmCommunicationDxe/MmCommunication.c   | 408
> > +++++++++++++++++++++
> >  .../Drivers/MmCommunicationDxe/MmCommunication.inf |  50 +++
> >  2 files changed, 458 insertions(+)
> >  create mode 100644
> > ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.c
> >  create mode 100644
> > ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.inf
> > 
> > diff --git a/ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.c
> > b/ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.c
> > new file mode 100644
> > index 0000000000..8ba1790af9
> > --- /dev/null
> > +++ b/ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.c
> > @@ -0,0 +1,408 @@
> > +/** @file
> > +
> > +  Copyright (c) 2016-2018, ARM Limited. All rights reserved.
> > +
> > +  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
> > +
> > https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fo
> > penso
> > urce.org%2Flicenses%2Fbsd-
> > license.php&data=02%7C01%7Cudit.kumar%40nxp.com%7Cc6986ed63017483b
> > 89dd08d5b1ff6c2d%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63
> > 6610632972644435&sdata=CoYRxTy3iCIKcy2xXEF6BJl1qNQEPZTLHBX9pXmrHR
> > w%3D&reserved=0
> > +
> > +  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 <Library/ArmLib.h>
> > +#include <Library/ArmSmcLib.h>
> > +#include <Library/BaseMemoryLib.h>
> > +#include <Library/DebugLib.h>
> > +#include <Library/DxeServicesTableLib.h>
> > +#include <Library/HobLib.h>
> > +#include <Library/PcdLib.h>
> > +#include <Library/UefiBootServicesTableLib.h>
> > +#include <Library/UefiRuntimeServicesTableLib.h>
> > +
> > +#include <Protocol/MmCommunication.h>
> > +
> > +#include <IndustryStandard/ArmStdSmc.h>
> > +
> > +#define MM_MAJOR_VER_MASK        0xFFFF0000
> > +#define MM_MINOR_VER_MASK        0x0000FFFF
> > +#define MM_MAJOR_VER_SHIFT       16
> > +
> > +const UINT32 MM_MAJOR_VER = 1;
> > +const UINT32 MM_MINOR_VER = 0;
> This should be UINT16 , as compare is done against UINT16
As per the interface spec, The version number is a 31-bit unsigned
integer, with the upper 15 bits denoting the major revision, and the
lower 16 bits denoting the minor revision.

I can modify this, if you like, but it is a cosmetic change.
>  
> 
> > 
> > +
> > +//
> > +// Address, Length of the pre-allocated buffer for communication
> > with the
> > secure
> > +// world.
> > +//
> > +STATIC ARM_MEMORY_REGION_DESCRIPTOR  mNsCommBuffMemRegion;
> > +
> > +// Notification event when virtual address map is set.
> > +STATIC EFI_EVENT  mSetVirtualAddressMapEvent;
> > +
> > +//
> > +// Handle to install the MM Communication Protocol
> > +//
> > +STATIC EFI_HANDLE  mMmCommunicateHandle;
> > +
> > +/**
> > +  Communicates with a registered handler.
> > +
> > +  This function provides an interface to send and receive messages
> > to the
> > +  Standalone MM environment on behalf of UEFI services.  This
> > function is part
> > +  of the MM Communication Protocol that may be called in physical
> > mode prior
> > to
> > +  SetVirtualAddressMap() and in virtual mode after
> > SetVirtualAddressMap().
> > +
> > +  @param[in]      This                The
> > EFI_MM_COMMUNICATION_PROTOCOL
> > +                                      instance.
> > +  @param[in, out] CommBuffer          A pointer to the buffer to
> > convey
> > +                                      into MMRAM.
> > +  @param[in, out] CommSize            The size of the data buffer
> > being
> > +                                      passed in. This is optional.
> > +
> > +  @retval EFI_SUCCESS                 The message was successfully
> > posted.
> > +  @retval EFI_INVALID_PARAMETER       The CommBuffer was NULL.
> > +  @retval EFI_BAD_BUFFER_SIZE         The buffer size is incorrect
> > for the MM
> > +                                      implementation. If this
> > error is
> > +                                      returned, the MessageLength
> > field in
> > +                                      the CommBuffer header or the
> > integer
> > +                                      pointed by CommSize are
> > updated to reflect
> > +                                      the maximum payload size the
> > +                                      implementation can
> > accommodate.
> > +  @retval EFI_ACCESS_DENIED           The CommunicateBuffer
> > parameter
> > +                                      or CommSize parameter, if
> > not omitted,
> > +                                      are in address range that
> > cannot be
> > +                                      accessed by the MM
> > environment
> > +**/
> > +STATIC
> > +EFI_STATUS
> > +EFIAPI
> > +MmCommunicationCommunicate (
> > +  IN CONST EFI_MM_COMMUNICATION_PROTOCOL  *This,
> > +  IN OUT VOID                             *CommBuffer,
> > +  IN OUT UINTN                            *CommSize OPTIONAL
> > +  )
> > +{
> > +  EFI_MM_COMMUNICATE_HEADER   *CommunicateHeader;
> > +  ARM_SMC_ARGS                CommunicateSmcArgs;
> > +  EFI_STATUS                  Status;
> > +  UINTN                       BufferSize;
> > +
> > +  Status = EFI_ACCESS_DENIED;
> > +  BufferSize = 0;
> > +
> > +  ZeroMem (&CommunicateSmcArgs, sizeof (ARM_SMC_ARGS));
> > +
> > +  //
> > +  // Check parameters
> > +  //
> > +  if (CommBuffer == NULL) {
> > +    return EFI_INVALID_PARAMETER;
> > +  }
> You can do, parameter check before doing zero-mem
> In case of bad parameters, it will save few CPU cycles 
Ok, but zeromem is part of initialization similar to initializing
status and BufferSize. 
> 
> > 
> > +
> > +  CommunicateHeader = CommBuffer;
> > +  // CommBuffer is a mandatory parameter. Hence, Rely on
> > +  // MessageLength + Header to ascertain the
> > +  // total size of the communication payload rather than
> > +  // rely on optional CommSize parameter
> > +  BufferSize = CommunicateHeader->MessageLength +
> > +               sizeof (CommunicateHeader->HeaderGuid) +
> > +               sizeof (CommunicateHeader->MessageLength);
> > +
> > +  // If the length of the CommBuffer is 0 then return the expected
> > length.
> > +  if (CommSize) {
> > +    // This case can be used by the consumer of this driver to
> > find out the
> > +    // max size that can be used for allocating CommBuffer.
> > +    if ((*CommSize == 0) ||
> > +        (*CommSize > mNsCommBuffMemRegion.Length)) {
> > +      *CommSize = mNsCommBuffMemRegion.Length;
> > +      return EFI_BAD_BUFFER_SIZE;
> > +    }
> > +    //
> > +    // CommSize must match MessageLength + sizeof
> > (EFI_MM_COMMUNICATE_HEADER);
> > +    //
> > +    if (*CommSize != BufferSize) {
> > +        return EFI_INVALID_PARAMETER;
> > +    }
> > +  }
> > +
> > +  //
> > +  // If the buffer size is 0 or greater than what can be tolerated
> > by the MM
> > +  // environment then return the expected size.
> > +  //
> > +  if ((BufferSize == 0) ||
> > +      (BufferSize > mNsCommBuffMemRegion.Length)) {
> > +    CommunicateHeader->MessageLength = mNsCommBuffMemRegion.Length
> > -
> > +                                       sizeof (CommunicateHeader-
> > >HeaderGuid) -
> > +                                       sizeof (CommunicateHeader-
> > >MessageLength);
> > +    return EFI_BAD_BUFFER_SIZE;
> > +  }
> > +
> > +  // SMC Function ID
> > +  CommunicateSmcArgs.Arg0 =
> > ARM_SMC_ID_MM_COMMUNICATE_AARCH64;
> > +
> > +  // Reserved for Future. Must be Zero.
> > +  CommunicateSmcArgs.Arg1 = 0;
> > +
> > +  // Copy Communication Payload
> > +  CopyMem ((VOID *)mNsCommBuffMemRegion.VirtualBase, CommBuffer,
> > BufferSize);
> > +
> > +  // For the SMC64 version, this parameter is a 64-bit Physical
> > Address (PA)
> > +  // or Intermediate Physical Address (IPA).
> > +  // For the SMC32 version, this parameter is a 32-bit PA or IPA.
> > +  CommunicateSmcArgs.Arg2 =
> > (UINTN)mNsCommBuffMemRegion.PhysicalBase;
> > +
> > +  // comm_size_address is a PA or an IPA that holds the size of
> > the
> > +  // communication buffer being passed in. This parameter is
> > optional
> > +  // and can be omitted by passing a zero.
> > +  // ARM does not recommend using it since this might require the
> > +  // implementation to create a separate memory mapping for the
> > parameter.
> > +  // ARM recommends storing the buffer size in the buffer itself.
> > +  CommunicateSmcArgs.Arg3 = 0;
> > +
> > +  // Call the Standalone MM environment.
> > +  ArmCallSmc (&CommunicateSmcArgs);
> > +
> > +  switch (CommunicateSmcArgs.Arg0) {
> > +  case ARM_SMC_MM_RET_SUCCESS:
> > +    ZeroMem (CommBuffer, BufferSize);
> > +    // On exit, the size of data being returned is inferred from
> > +    // MessageLength + Header.
> > +    CommunicateHeader = (EFI_MM_COMMUNICATE_HEADER
> > *)mNsCommBuffMemRegion.VirtualBase;
> > +    BufferSize = CommunicateHeader->MessageLength +
> > +                 sizeof (CommunicateHeader->HeaderGuid) +
> > +                 sizeof (CommunicateHeader->MessageLength);
> > +
> > +    // Note: Very important to ensure that the consumer of this
> > driver
> > +    // has allocated CommBuffer sufficiently so that the return
> > data
> > +    // can be copied. Otherwise, this will lead to buffer
> > overflow.
> > +    // Assumption: CommBuffer = malloc
> > (mNsCommBuffMemRegion.Length)
> > +    // This guidance should be in the PI specification. TODO: ECR.
> > +    CopyMem (CommBuffer,
> > +             (const VOID *)mNsCommBuffMemRegion.VirtualBase,
> > +             BufferSize);
> > +    Status = EFI_SUCCESS;
> > +    break;
> > +
> > +  case ARM_SMC_MM_RET_INVALID_PARAMS:
> > +    Status = EFI_INVALID_PARAMETER;
> > +    break;
> > +
> > +  case ARM_SMC_MM_RET_DENIED:
> > +    Status = EFI_ACCESS_DENIED;
> > +    break;
> > +
> > +  case ARM_SMC_MM_RET_NO_MEMORY:
> > +    // Unexpected error since the CommSize was checked for zero
> > length
> > +    // prior to issuing the SMC
> > +  default:
> > +    Status = EFI_ACCESS_DENIED;
> > +    ASSERT (0);
> > +  }
> > +
> > +  return Status;
> > +}
> > +
> > +//
> > +// MM Communication Protocol instance
> > +//
> > +EFI_MM_COMMUNICATION_PROTOCOL  mMmCommunication = {
> > +  MmCommunicationCommunicate
> > +};
> > +
> > +/**
> > +  Notification callback on SetVirtualAddressMap event.
> > +
> > +  This function notifies the MM communication protocol interface
> > on
> > +  SetVirtualAddressMap event and converts pointers used in this
> > driver
> > +  from physical to virtual address.
> > +
> > +  @param  Event          SetVirtualAddressMap event.
> > +  @param  Context        A context when the SetVirtualAddressMap
> > triggered.
> > +
> > +  @retval EFI_SUCCESS    The function executed successfully.
> > +  @retval Other          Some error occurred when executing this
> > function.
> > +
> > +**/
> > +STATIC
> > +VOID
> > +EFIAPI
> > +NotifySetVirtualAddressMap (
> > +  IN EFI_EVENT  Event,
> > +  IN VOID      *Context
> > +  )
> > +{
> > +  EFI_STATUS  Status;
> > +
> > +  Status = gRT->ConvertPointer (EFI_OPTIONAL_PTR,
> > +                                (VOID
> > **)&mNsCommBuffMemRegion.VirtualBase
> > +                               );
> > +  if (EFI_ERROR (Status)) {
> > +    DEBUG ((DEBUG_ERROR, "NotifySetVirtualAddressMap():"
> > +            " Unable to convert MM runtime pointer.
> > Status:0x%r\n", Status));
> > +  }
> > +
> > +}
> > +
> > +STATIC
> > +EFI_STATUS
> > +GetMmVersion ()
> > +{
> > +  EFI_STATUS   Status;
> > +  UINT16       MmMajorVersion;
> > +  UINT16       MmMinorVersion;
> > +  UINT32       MmVersion;
> > +  ARM_SMC_ARGS MmVersionArgs;
> > +
> > +  MmVersionArgs.Arg0 = ARM_SMC_ID_MM_VERSION_AARCH32;
> > +
> > +  ArmCallSmc (&MmVersionArgs);
> > +
> > +  MmVersion = MmVersionArgs.Arg0;
> > +
> > +  MmMajorVersion = ((MmVersion & MM_MAJOR_VER_MASK) >>
> > MM_MAJOR_VER_SHIFT);
> MmVersion >> MM_MAJOR_VER_SHIFT is same as of 
> ((MmVersion & MM_MAJOR_VER_MASK) >> MM_MAJOR_VER_SHIFT);
Yes. However, 
the format of the value is as follows:
• Bit [31]: Must be 0
• Bits [30:16] Major Version: Must be 1 for this revision of MM
• Bits [15:0] Minor Version: Must be 0 for this revision of MM

So having a mask and shift relates to spec better.

> 
> > 
> > +  MmMinorVersion = ((MmVersion & MM_MINOR_VER_MASK) >> 0);
> > +
> > +  // Different major revision values indicate possibly
> > incompatible functions.
> > +  // For two revisions, A and B, for which the major revision
> > values are
> > +  // identical, if the minor revision value of revision B is
> > greater than
> > +  // the minor revision value of revision A, then every function
> > in
> > +  // revision A must work in a compatible way with revision B.
> > +  // However, it is possible for revision B to have a higher
> > +  // function count than revision A.
> > +  if ((MmMajorVersion == MM_MAJOR_VER) &&
> > +      (MmMinorVersion >= MM_MINOR_VER))
> > +  {
> > +    DEBUG ((DEBUG_INFO, "MM Version: Major=0x%x, Minor=0x%x\n",
> > +           MmMajorVersion, MmMinorVersion));
> > +    Status = EFI_SUCCESS;
> > +  }
> You can do bit soft here, if ATF has less functions then current
> version of MM driver, 
> This is possible that some of additional functions of UEFI side are
> not used for booting. 
> Minor number mismatch should go with warning that some of functions
> may not work
> Instead of denial.
> Your view please   
> 
Please clarify, if I have not understood your statement above properly.

E.g.,
Secure World 1.0 implements
MM_VERSION, MM_COMMUNICATE

Secure World 1.1 implements
MM_VERSION, MM_COMMUNICATE, MM_GET_ATTRIBUTES

Normal World 1.0 uses
MM_VERSION, MM_COMMUNICATE

Normal World 1.1 uses
MM_VERSION, MM_COMMUNICATE, MM_GET_ATTRIBUTES

Case 1: Normal world uefi is at version 1.1 and secure world is at
version 1.1, this is a valid case and it should work.

Case 2: Normal world uefi is at version 1.1 and secure world is at
version 1.0, this will not work because Normal world 1.1 will use
MM_GET_ATTRIBUTES and however it is not present in secure world.

Case 3: Normal world uefi is at version 1.0 and secure world is at
version 1.1, this will work because Normal World 1.0 uses
MM_VERSION, MM_COMMUNICATE even though secure world supports
MM_GET_ATTRIBUTES, it will not be used by normal world. This is case 
where secure world has a higher function count than what the normal
world will use. 

> > 
> > +  else
> > +  {
> > +    DEBUG ((DEBUG_ERROR, "Incompatible MM Versions.\n Current
> > Version:
> > Major=0x%x, Minor=0x%x.\n Expected: Major=0x%x, Minor>=0x%x.\n",
> > +            MmMajorVersion, MmMinorVersion, MM_MAJOR_VER,
> > MM_MINOR_VER));
> > +    Status = EFI_UNSUPPORTED;
> > +  }
> > +
> > +  return Status;
> > +}
> > +
> > +/**
> > +  The Entry Point for MM Communication
> > +
> > +  This function installs the MM communication protocol interface
> > and finds out
> > +  what type of buffer management will be required prior to
> > invoking the
> > +  communication SMC.
> > +
> > +  @param  ImageHandle    The firmware allocated handle for the EFI
> > image.
> > +  @param  SystemTable    A pointer to the EFI System Table.
> > +
> > +  @retval EFI_SUCCESS    The entry point is executed successfully.
> > +  @retval Other          Some error occurred when executing this
> > entry point.
> > +
> > +**/
> > +EFI_STATUS
> > +EFIAPI
> > +MmCommunicationInitialize (
> > +  IN EFI_HANDLE         ImageHandle,
> > +  IN EFI_SYSTEM_TABLE  *SystemTable
> > +  )
> > +{
> > +  EFI_STATUS                 Status;
> > +
> > +    // Get Secure Partition Manager Version Information
> > +  Status = GetMmVersion ();
> > +  if (EFI_ERROR(Status)) {
> > +    goto ReturnErrorStatus;
> > +  }
> > +
> > +  mNsCommBuffMemRegion.PhysicalBase = PcdGet64 (PcdMmBufferBase);
> > +  // During boot , Virtual and Physical are same
> > +  mNsCommBuffMemRegion.VirtualBase =
> > mNsCommBuffMemRegion.PhysicalBase;
> > +  mNsCommBuffMemRegion.Length = PcdGet64 (PcdMmBufferSize);
> > +
> > +  if (mNsCommBuffMemRegion.PhysicalBase == 0) {
> > +    DEBUG ((DEBUG_ERROR, "MmCommunicateInitialize: "
> > +            "Invalid MM Buffer Base Address.\n"));
> > +    goto ReturnErrorStatus;
> > +  }
> > +
> > +  if (mNsCommBuffMemRegion.Length == 0) {
> > +    DEBUG ((DEBUG_ERROR, "MmCommunicateInitialize: "
> > +            "Maximum Buffer Size is zero.\n"));
> > +    goto ReturnErrorStatus;
> > +  }
> > +
> > +  Status = gDS->AddMemorySpace (EfiGcdMemoryTypeSystemMemory,
> > +                                mNsCommBuffMemRegion.PhysicalBase,
> > +                                mNsCommBuffMemRegion.Length,
> > +                                EFI_MEMORY_WB |
> > +                                EFI_MEMORY_XP |
> > +                                EFI_MEMORY_RUNTIME);
> > +  if (EFI_ERROR (Status)) {
> > +    DEBUG ((DEBUG_ERROR, "MmCommunicateInitialize: "
> > +            "Failed to add MM-NS Buffer Memory Space\n"));
> > +    goto ReturnErrorStatus;
> > +  }
> > +
> > +  Status = gDS->SetMemorySpaceAttributes
> > (mNsCommBuffMemRegion.PhysicalBase,
> > +                                          mNsCommBuffMemRegion.Len
> > gth,
> > +                                          EFI_MEMORY_WB |
> > EFI_MEMORY_XP);
> > +  if (EFI_ERROR (Status)) {
> > +    DEBUG ((DEBUG_ERROR, "MmCommunicateInitialize: "
> > +            "Failed to set MM-NS Buffer Memory attributes\n"));
> > +    goto CleanAddedMemorySpace;
> > +  }
> > +
> > +  Status = gBS->AllocatePages (AllocateAddress,
> > +                               EfiRuntimeServicesData,
> > +                               EFI_SIZE_TO_PAGES
> > (mNsCommBuffMemRegion.Length),
> > +                               &mNsCommBuffMemRegion.PhysicalBase)
> > ;
> > +  if (EFI_ERROR (Status)) {
> > +    DEBUG ((DEBUG_ERROR, "MmCommunicateInitialize: "
> > +            "Failed to allocate MM-NS Buffer Memory Space\n"));
> > +    goto CleanAddedMemorySpace;
> > +  }
> > +
> > +  // Install the communication protocol
> > +  Status = gBS->InstallProtocolInterface (&mMmCommunicateHandle,
> > +                                          &gEfiMmCommunicationProt
> > ocolGuid,
> > +                                          EFI_NATIVE_INTERFACE,
> > +                                          &mMmCommunication);
> > +  if (EFI_ERROR(Status)) {
> > +    DEBUG ((DEBUG_ERROR, "MmCommunicationInitialize: "
> > +            "Failed to install MM communication protocol\n"));
> > +    goto CleanAllocatedPages;
> > +  }
> > +
> > +  // Register notification callback when  virtual address is
> > associated
> > +  // with the physical address.
> > +  // Create a Set Virtual Address Map event.
> > +  //
> > +  Status = gBS->CreateEvent
> > (EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE,  //
> > Type
> > +                             TPL_NOTIFY,                         /
> > / NotifyTpl
> > +                             NotifySetVirtualAddressMap,         /
> > / NotifyFunction
> > +                             NULL,                               /
> > / NotifyContext
> > +                             &mSetVirtualAddressMapEvent         /
> > / Event
> > +                            );
> > +  if (Status == EFI_SUCCESS) {
> > +    return Status;
> > +  }
> > +
> > +  gBS->UninstallProtocolInterface(mMmCommunicateHandle,
> > +                                  &gEfiMmCommunicationProtocolGuid
> > ,
> > +                                  &mMmCommunication);
> > +
> > +CleanAllocatedPages:
> > +  gBS->FreePages (mNsCommBuffMemRegion.PhysicalBase,
> > +                  EFI_SIZE_TO_PAGES
> > (mNsCommBuffMemRegion.Length));
> > +
> > +CleanAddedMemorySpace:
> > +  gDS->RemoveMemorySpace (mNsCommBuffMemRegion.PhysicalBase,
> > +                          mNsCommBuffMemRegion.Length);
> > +
> > +ReturnErrorStatus:
> > +  return EFI_INVALID_PARAMETER;
> > +}
> > diff --git a/ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.inf
> > b/ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.inf
> > new file mode 100644
> > index 0000000000..7797e3de74
> > --- /dev/null
> > +++ b/ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.inf
> > @@ -0,0 +1,50 @@
> > +#/** @file
> > +#
> > +#  DXE MM Communicate driver
> > +#
> > +#  Copyright (c) 2016 - 2018, ARM Limited. All rights reserved.
> > +#
> > +#  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
> > +#
> > https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fo
> > penso
> > urce.org%2Flicenses%2Fbsd-
> > license.php&data=02%7C01%7Cudit.kumar%40nxp.com%7Cc6986ed63017483b
> > 89dd08d5b1ff6c2d%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63
> > 6610632972644435&sdata=CoYRxTy3iCIKcy2xXEF6BJl1qNQEPZTLHBX9pXmrHR
> > w%3D&reserved=0
> > +#
> > +#  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                    = 0x0001001A
> > +  BASE_NAME                      = ArmMmCommunication
> > +  FILE_GUID                      = 09EE81D3-F15E-43F4-85B4-
> > CB9873DA5D6B
> > +  MODULE_TYPE                    = DXE_RUNTIME_DRIVER
> > +  VERSION_STRING                 = 1.0
> > +
> > +  ENTRY_POINT                    = MmCommunicationInitialize
> > +
> > +[Sources.AARCH64]
> > +  MmCommunication.c
> > +
> > +[Packages]
> > +  ArmPkg/ArmPkg.dec
> > +  MdePkg/MdePkg.dec
> > +
> > +[LibraryClasses]
> > +  ArmLib
> > +  ArmSmcLib
> > +  BaseMemoryLib
> > +  DebugLib
> > +  DxeServicesTableLib
> > +  HobLib
> > +  UefiDriverEntryPoint
> > +
> > +[Protocols]
> > +  gEfiMmCommunicationProtocolGuid              ## PRODUCES
> > +
> > +[Pcd.common]
> > +  gArmTokenSpaceGuid.PcdMmBufferBase
> > +  gArmTokenSpaceGuid.PcdMmBufferSize
> > +
> > +[Depex]
> > +  gEfiCpuArchProtocolGuid
> > --
> > 2.16.2
> > 
> > _______________________________________________
> > edk2-devel mailing list
> > edk2-devel@lists.01.org
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> > lists.01
> > .org%2Fmailman%2Flistinfo%2Fedk2-
> > devel&data=02%7C01%7Cudit.kumar%40nxp.com%7Cc6986ed63017483b89dd0
> > 8d5b1ff6c2d%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6366106
> > 32972644435&sdata=Jsyaz5Z5jiKFEjuUKi9UGi4l%2FftI9TXEGLPVSfzh%2Bo0%3
> > D
> > &reserved=0