Re: 回复: [edk2-devel] [PATCH v1 2/2] MdeModulePkg: Variable: Introduce MM based variable read service in PEI

["Kun Qin" <kuqin12@gmail.com>]

Hi Liming,

Thanks for catching that. I have removed the PCD usage and resend the 
patch here:
https://edk2.groups.io/g/devel/message/106372

Could you please let me know if you have any other feedback?

Per your functionality question, yes, the functionality was verified on 
both virtual
and physical ARM platforms. I also added this statement to the v2 cover 
letter.

Thanks,
Kun

On 6/24/2023 7:23 PM, gaoliming via groups.io wrote:
> Kun:
>    Seemly, PcdMaxVariableSize is not used by this module. It can be removed.
>
>    And, has its functionality been verified in the real platform?
>
> Thanks
> Liming
>> -----邮件原件-----
>> 发件人: devel@edk2.groups.io <devel@edk2.groups.io> 代表 Kun Qin
>> 发送时间: 2023年6月9日 4:45
>> 收件人: devel@edk2.groups.io
>> 抄送: Hao A Wu <hao.a.wu@intel.com>; Liming Gao
>> <gaoliming@byosoft.com.cn>; Jian J Wang <jian.j.wang@intel.com>; Ronny
>> Hansen <hansen.ronny@microsoft.com>; Shriram Masanamuthu
>> Chinnathurai <shriramma@microsoft.com>; Preshit Harlikar
>> <pharlikar@microsoft.com>
>> 主题: [edk2-devel] [PATCH v1 2/2] MdeModulePkg: Variable: Introduce MM
>> based variable read service in PEI
>>
>> From: Kun Qin <kuqin@microsoft.com>
>>
>> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4464
>>
>> This change introduced the Standalone MM based variable read capability
>> in PEI phase for applicable platforms (such as ARM platforms).
>>
>> Similar to the x86 counterpart, MM communicate PPI is used to request
>> variable information from Standalone MM environment.
>>
>> Cc: Hao A Wu <hao.a.wu@intel.com>
>> Cc: Liming Gao <gaoliming@byosoft.com.cn>
>> Cc: Jian J Wang <jian.j.wang@intel.com>
>>
>> Co-authored-by: Ronny Hansen <hansen.ronny@microsoft.com>
>> Co-authored-by: Shriram Masanamuthu Chinnathurai
>> <shriramma@microsoft.com>
>> Co-authored-by: Preshit Harlikar <pharlikar@microsoft.com>
>> Signed-off-by: Kun Qin <kuqin@microsoft.com>
>> ---
>>   MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.c   |
>> 381 ++++++++++++++++++++
>>   MdeModulePkg/MdeModulePkg.dsc
>> |   1 +
>>   MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.h   |
>> 134 +++++++
>>   MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.inf |
>> 43 +++
>>   4 files changed, 559 insertions(+)
>>
>> diff --git
>> a/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.c
>> b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.c
>> new file mode 100644
>> index 000000000000..4f937e22e89e
>> --- /dev/null
>> +++ b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.c
>> @@ -0,0 +1,381 @@
>> +/** @file -- MmVariablePei.c
>>
>> +  Provides interface for reading Secure System Variables during PEI.
>>
>> +
>>
>> +  Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
>>
>> +  Copyright (c) Microsoft Corporation.<BR>
>>
>> +  SPDX-License-Identifier: BSD-2-Clause-Patent
>>
>> +**/
>>
>> +
>>
>> +#include "MmVariablePei.h"
>>
>> +
>>
>> +#define MM_VARIABLE_COMM_BUFFER_OFFSET
>> (SMM_COMMUNICATE_HEADER_SIZE +
>> SMM_VARIABLE_COMMUNICATE_HEADER_SIZE)
>>
>> +
>>
>> +//
>>
>> +// Module globals
>>
>> +//
>>
>> +EFI_PEI_READ_ONLY_VARIABLE2_PPI  mPeiSecureVariableRead = {
>>
>> +  PeiMmGetVariable,
>>
>> +  PeiMmGetNextVariableName
>>
>> +};
>>
>> +
>>
>> +EFI_PEI_PPI_DESCRIPTOR  mPeiMmVariablePpi = {
>>
>> +  (EFI_PEI_PPI_DESCRIPTOR_PPI |
>> EFI_PEI_PPI_DESCRIPTOR_TERMINATE_LIST),
>>
>> +  &gEfiPeiReadOnlyVariable2PpiGuid,
>>
>> +  &mPeiSecureVariableRead
>>
>> +};
>>
>> +
>>
>> +/**
>>
>> +  Entry point of PEI Secure Variable read driver
>>
>> +
>>
>> +  @param  FileHandle   Handle of the file being invoked.
>>
>> +                       Type EFI_PEI_FILE_HANDLE is defined in
>> FfsFindNextFile().
>>
>> +  @param  PeiServices  General purpose services available to every
>> PEIM.
>>
>> +
>>
>> +  @retval EFI_SUCCESS  If the interface could be successfully installed
>>
>> +  @retval Others       Returned from PeiServicesInstallPpi()
>>
>> +**/
>>
>> +EFI_STATUS
>>
>> +EFIAPI
>>
>> +PeiMmVariableInitialize (
>>
>> +  IN       EFI_PEI_FILE_HANDLE  FileHandle,
>>
>> +  IN CONST EFI_PEI_SERVICES     **PeiServices
>>
>> +  )
>>
>> +{
>>
>> +  return PeiServicesInstallPpi (&mPeiMmVariablePpi);
>>
>> +}
>>
>> +
>>
>> +/**
>>
>> +  Helper function to populate MM communicate header and variable
>> communicate header
>>
>> +  and then communicate to PEI.
>>
>> +
>>
>> +  @param[in, out] CommunicateBuffer       Size of the variable name.
>>
>> +  @param[in]      CommunicateBufferSize   The entire buffer size to be
>> sent to MM.
>>
>> +  @param[in]      Function                The MM variable function
>> value.
>>
>> +
>>
>> +  @retval EFI_INVALID_PARAMETER      Invalid parameter.
>>
>> +  @retval EFI_SUCCESS                Find the specified variable.
>>
>> +  @retval Others                     Errors returned by MM
>> communicate or variable service.
>>
>> +
>>
>> +**/
>>
>> +EFI_STATUS
>>
>> +PopulateHeaderAndCommunicate (
>>
>> +  IN OUT  UINT8  *CommunicateBuffer,
>>
>> +  IN UINTN       CommunicateBufferSize,
>>
>> +  IN UINTN       Function
>>
>> +  )
>>
>> +{
>>
>> +  EFI_STATUS                       Status;
>>
>> +  EFI_PEI_MM_COMMUNICATION_PPI     *MmCommunicationPpi;
>>
>> +  EFI_MM_COMMUNICATE_HEADER        *MmCommunicateHeader;
>>
>> +  SMM_VARIABLE_COMMUNICATE_HEADER  *MmVarCommsHeader;
>>
>> +
>>
>> +  // Minimal sanity check
>>
>> +  if ((CommunicateBuffer == NULL) ||
>>
>> +      (CommunicateBufferSize <
>> MM_VARIABLE_COMM_BUFFER_OFFSET))
>>
>> +  {
>>
>> +    Status = EFI_INVALID_PARAMETER;
>>
>> +    DEBUG ((DEBUG_ERROR, "%a: Invalid incoming parameters: %p and
>> 0x%x\n", __func__, CommunicateBuffer, CommunicateBufferSize));
>>
>> +    goto Exit;
>>
>> +  }
>>
>> +
>>
>> +  if ((Function !=
>> SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME) &&
>>
>> +      (Function != SMM_VARIABLE_FUNCTION_GET_VARIABLE))
>>
>> +  {
>>
>> +    Status = EFI_INVALID_PARAMETER;
>>
>> +    DEBUG ((DEBUG_ERROR, "%a: Invalid function value: 0x%x\n",
>> __func__, Function));
>>
>> +    goto Exit;
>>
>> +  }
>>
>> +
>>
>> +  Status = PeiServicesLocatePpi (&gEfiPeiMmCommunicationPpiGuid, 0,
>> NULL, (VOID **)&MmCommunicationPpi);
>>
>> +  if (EFI_ERROR (Status)) {
>>
>> +    DEBUG ((DEBUG_ERROR, "%a: Failed to locate PEI MM Communication
>> PPI: %r\n", __func__, Status));
>>
>> +    goto Exit;
>>
>> +  }
>>
>> +
>>
>> +  // Zero the entire Communication Buffer Header
>>
>> +  MmCommunicateHeader = (EFI_MM_COMMUNICATE_HEADER
>> *)CommunicateBuffer;
>>
>> +
>>
>> +  ZeroMem (MmCommunicateHeader,
>> SMM_COMMUNICATE_HEADER_SIZE);
>>
>> +
>>
>> +  // Use gEfiSmmVariableProtocolGuid to request the MM variable service
>> in Standalone MM
>>
>> +  CopyMem ((VOID *)&MmCommunicateHeader->HeaderGuid,
>> &gEfiSmmVariableProtocolGuid, sizeof (GUID));
>>
>> +
>>
>> +  // Program the MM header size
>>
>> +  MmCommunicateHeader->MessageLength = CommunicateBufferSize -
>> SMM_COMMUNICATE_HEADER_SIZE;
>>
>> +
>>
>> +  MmVarCommsHeader = (SMM_VARIABLE_COMMUNICATE_HEADER
>> *)(CommunicateBuffer + SMM_COMMUNICATE_HEADER_SIZE);
>>
>> +
>>
>> +  // We are only supporting GetVariable and GetNextVariableName
>>
>> +  MmVarCommsHeader->Function = Function;
>>
>> +
>>
>> +  // Send the MM request using MmCommunicationPei
>>
>> +  Status = MmCommunicationPpi->Communicate (MmCommunicationPpi,
>> CommunicateBuffer, &CommunicateBufferSize);
>>
>> +  if (EFI_ERROR (Status)) {
>>
>> +    // Received an error from MM interface.
>>
>> +    DEBUG ((DEBUG_ERROR, "%a - MM Interface Error: %r\n", __func__,
>> Status));
>>
>> +    goto Exit;
>>
>> +  }
>>
>> +
>>
>> +  // MM request was successfully handled by the framework.
>>
>> +  // Set status to the Variable Service Status Code
>>
>> +  Status = MmVarCommsHeader->ReturnStatus;
>>
>> +  if (EFI_ERROR (Status)) {
>>
>> +    // We received an error from Variable Service.
>>
>> +    // We cant do anymore so return Status
>>
>> +    if (Status != EFI_BUFFER_TOO_SMALL) {
>>
>> +      DEBUG ((DEBUG_ERROR, "%a - Variable Service Error: %r\n",
>> __func__, Status));
>>
>> +    }
>>
>> +
>>
>> +    goto Exit;
>>
>> +  }
>>
>> +
>>
>> +Exit:
>>
>> +  return Status;
>>
>> +}
>>
>> +
>>
>> +/**
>>
>> +  This service retrieves a variable's value using its name and GUID.
>>
>> +
>>
>> +  This function is using the Secure Variable Store. If the Data
>>
>> +  buffer is too small to hold the contents of the variable, the error
>>
>> +  EFI_BUFFER_TOO_SMALL is returned and DataSize is set to the required
>> buffer
>>
>> +  size to obtain the data.
>>
>> +
>>
>> +  @param  This                  A pointer to this instance of the
>> EFI_PEI_READ_ONLY_VARIABLE2_PPI.
>>
>> +  @param  VariableName          A pointer to a null-terminated string
>> that is the variable's name.
>>
>> +  @param  VariableGuid          A pointer to an EFI_GUID that is the
>> variable's GUID. The combination of
>>
>> +                                VariableGuid and VariableName
>> must be unique.
>>
>> +  @param  Attributes            If non-NULL, on return, points to the
>> variable's attributes.
>>
>> +  @param  DataSize              On entry, points to the size in bytes
>> of the Data buffer.
>>
>> +                                On return, points to the size of the
>> data returned in Data.
>>
>> +  @param  Data                  Points to the buffer which will hold
>> the returned variable value.
>>
>> +                                May be NULL with a zero DataSize in
>> order to determine the size of the buffer needed.
>>
>> +
>>
>> +  @retval EFI_SUCCESS           The variable was read successfully.
>>
>> +  @retval EFI_NOT_FOUND         The variable was not found.
>>
>> +  @retval EFI_BUFFER_TOO_SMALL  The DataSize is too small for the
>> resulting data.
>>
>> +                                DataSize is updated with the size
>> required for
>>
>> +                                the specified variable.
>>
>> +  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid, DataSize
>> or Data is NULL.
>>
>> +  @retval EFI_DEVICE_ERROR      The variable could not be retrieved
>> because of a device error.
>>
>> +
>>
>> +**/
>>
>> +EFI_STATUS
>>
>> +EFIAPI
>>
>> +PeiMmGetVariable (
>>
>> +  IN CONST  EFI_PEI_READ_ONLY_VARIABLE2_PPI *This,
>>
>> +  IN CONST  CHAR16 *VariableName,
>>
>> +  IN CONST  EFI_GUID *VariableGuid,
>>
>> +  OUT       UINT32 *Attributes, OPTIONAL
>>
>> +  IN OUT    UINTN                            *DataSize,
>>
>> +  OUT       VOID                             *Data OPTIONAL
>>
>> +  )
>>
>> +{
>>
>> +  EFI_STATUS                                Status;
>>
>> +  UINTN                                     MessageSize;
>>
>> +  SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE
>> *MmVarAccessHeader;
>>
>> +  UINT8
>> *MmCommunicateBuffer;
>>
>> +  UINTN                                     RequiredPages;
>>
>> +
>>
>> +  // Check input parameters
>>
>> +  if ((VariableName == NULL) || (VariableGuid == NULL) || (DataSize ==
>> NULL)) {
>>
>> +    return EFI_INVALID_PARAMETER;
>>
>> +  }
>>
>> +
>>
>> +  if (VariableName[0] == 0) {
>>
>> +    return EFI_NOT_FOUND;
>>
>> +  }
>>
>> +
>>
>> +  if ((*DataSize > 0) && (Data == NULL)) {
>>
>> +    return EFI_INVALID_PARAMETER;
>>
>> +  }
>>
>> +
>>
>> +  // Allocate required pages to send MM request
>>
>> +  MessageSize = MM_VARIABLE_COMM_BUFFER_OFFSET +
>>
>> +                OFFSET_OF
>> (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name) +
>>
>> +                StrSize (VariableName) + *DataSize;
>>
>> +
>>
>> +  RequiredPages       = EFI_SIZE_TO_PAGES (MessageSize);
>>
>> +  MmCommunicateBuffer = (UINT8 *)AllocatePages (RequiredPages);
>>
>> +
>>
>> +  if (MmCommunicateBuffer == NULL) {
>>
>> +    Status = EFI_OUT_OF_RESOURCES;
>>
>> +    DEBUG ((DEBUG_ERROR, "%a: Failed to allocate memory: %r\n",
>> __func__, Status));
>>
>> +    return Status;
>>
>> +  }
>>
>> +
>>
>> +  // Zero the entire Communication Buffer
>>
>> +  ZeroMem (MmCommunicateBuffer, (RequiredPages * EFI_PAGE_SIZE));
>>
>> +
>>
>> +  //
>>
>> +  // Program all payload structure contents
>>
>> +  //
>>
>> +  MmVarAccessHeader =
>> (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE
>> *)(MmCommunicateBuffer + MM_VARIABLE_COMM_BUFFER_OFFSET);
>>
>> +
>>
>> +  // Variable GUID
>>
>> +  CopyMem ((VOID *)&MmVarAccessHeader->Guid, VariableGuid, sizeof
>> (GUID));
>>
>> +
>>
>> +  // Program the max amount of data we accept.
>>
>> +  MmVarAccessHeader->DataSize = *DataSize;
>>
>> +
>>
>> +  // Get size of the variable name
>>
>> +  MmVarAccessHeader->NameSize = StrSize (VariableName);
>>
>> +
>>
>> +  // Populate incoming variable name
>>
>> +  CopyMem ((VOID *)&MmVarAccessHeader->Name, VariableName,
>> MmVarAccessHeader->NameSize);
>>
>> +
>>
>> +  Status = PopulateHeaderAndCommunicate (MmCommunicateBuffer,
>> MessageSize, SMM_VARIABLE_FUNCTION_GET_VARIABLE);
>>
>> +  if (EFI_ERROR (Status)) {
>>
>> +    // We received an error from either communicate or Variable Service.
>>
>> +    if (Status != EFI_BUFFER_TOO_SMALL) {
>>
>> +      DEBUG ((DEBUG_ERROR, "%a - Communite to MM for variable
>> service errored: %r\n", __func__, Status));
>>
>> +    }
>>
>> +
>>
>> +    goto Exit;
>>
>> +  }
>>
>> +
>>
>> +  Status = EFI_SUCCESS;
>>
>> +
>>
>> +  // User provided buffer is too small
>>
>> +  if (*DataSize < MmVarAccessHeader->DataSize) {
>>
>> +    Status = EFI_BUFFER_TOO_SMALL;
>>
>> +  }
>>
>> +
>>
>> +Exit:
>>
>> +  // Check if we need to set Attributes
>>
>> +  if (Attributes != NULL) {
>>
>> +    *Attributes = MmVarAccessHeader->Attributes;
>>
>> +  }
>>
>> +
>>
>> +  *DataSize = MmVarAccessHeader->DataSize;
>>
>> +
>>
>> +  if (Status == EFI_SUCCESS) {
>>
>> +    CopyMem ((VOID *)Data, (UINT8 *)MmVarAccessHeader->Name +
>> MmVarAccessHeader->NameSize, *DataSize);
>>
>> +  }
>>
>> +
>>
>> +  // Free the Communication Buffer
>>
>> +  if (MmCommunicateBuffer != NULL) {
>>
>> +    FreePages (MmCommunicateBuffer, RequiredPages);
>>
>> +  }
>>
>> +
>>
>> +  return Status;
>>
>> +}
>>
>> +
>>
>> +/**
>>
>> +  Return the next variable name and GUID.
>>
>> +
>>
>> +  This function is called multiple times to retrieve the VariableName
>>
>> +  and VariableGuid of all variables currently available in the system.
>>
>> +  On each call, the previous results are passed into the interface,
>>
>> +  and, on return, the interface returns the data for the next
>>
>> +  interface. When the entire variable list has been returned,
>>
>> +  EFI_NOT_FOUND is returned.
>>
>> +
>>
>> +  @param  This              A pointer to this instance of the
>> EFI_PEI_READ_ONLY_VARIABLE2_PPI.
>>
>> +
>>
>> +  @param  VariableNameSize  On entry, points to the size of the buffer
>> pointed to by VariableName.
>>
>> +                            On return, the size of the variable name
>> buffer.
>>
>> +  @param  VariableName      On entry, a pointer to a null-terminated
>> string that is the variable's name.
>>
>> +                            On return, points to the next variable's
>> null-terminated name string.
>>
>> +
>>
>> +  @param  VariableGuid      On entry, a pointer to an EFI_GUID that is
>> the variable's GUID.
>>
>> +                            On return, a pointer to the next variable's
>> GUID.
>>
>> +
>>
>> +  @retval EFI_SUCCESS           The variable was read successfully.
>>
>> +  @retval EFI_NOT_FOUND         The variable could not be found.
>>
>> +  @retval EFI_BUFFER_TOO_SMALL  The VariableNameSize is too small
>> for the resulting
>>
>> +                                data. VariableNameSize is updated
>> with the size
>>
>> +                                required for the specified variable.
>>
>> +  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid or
>>
>> +                                VariableNameSize is NULL.
>>
>> +  @retval EFI_DEVICE_ERROR      The variable could not be retrieved
>> because of a device error.
>>
>> +**/
>>
>> +EFI_STATUS
>>
>> +EFIAPI
>>
>> +PeiMmGetNextVariableName (
>>
>> +  IN CONST  EFI_PEI_READ_ONLY_VARIABLE2_PPI  *This,
>>
>> +  IN OUT UINTN                               *VariableNameSize,
>>
>> +  IN OUT CHAR16                              *VariableName,
>>
>> +  IN OUT EFI_GUID                            *VariableGuid
>>
>> +  )
>>
>> +{
>>
>> +  EFI_STATUS                                       Status;
>>
>> +  UINTN
>> MessageSize;
>>
>> +  UINT8
>> *MmCommunicateBuffer;
>>
>> +  SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME
>> *MmVarGetNextVarHeader;
>>
>> +  UINTN
>> RequiredPages;
>>
>> +
>>
>> +  // Check input parameters
>>
>> +  if ((VariableName == NULL) ||
>>
>> +      (VariableGuid == NULL) ||
>>
>> +      (VariableNameSize == NULL) ||
>>
>> +      (*VariableNameSize == 0))
>>
>> +  {
>>
>> +    return EFI_INVALID_PARAMETER;
>>
>> +  }
>>
>> +
>>
>> +  // Allocate required pages to send MM request
>>
>> +  MessageSize = MM_VARIABLE_COMM_BUFFER_OFFSET +
>>
>> +                OFFSET_OF
>> (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name) +
>>
>> +                StrSize (VariableName) + *VariableNameSize;
>>
>> +
>>
>> +  RequiredPages       = EFI_SIZE_TO_PAGES (MessageSize);
>>
>> +  MmCommunicateBuffer = (UINT8 *)AllocatePages (RequiredPages);
>>
>> +
>>
>> +  if (MmCommunicateBuffer == NULL) {
>>
>> +    Status = EFI_OUT_OF_RESOURCES;
>>
>> +    DEBUG ((DEBUG_ERROR, "%a: Failed to allocate memory: %r\n",
>> __func__, Status));
>>
>> +    return Status;
>>
>> +  }
>>
>> +
>>
>> +  // Zero the entire Communication Buffer
>>
>> +  ZeroMem (MmCommunicateBuffer, (RequiredPages * EFI_PAGE_SIZE));
>>
>> +
>>
>> +  //
>>
>> +  // Program all payload structure contents
>>
>> +  //
>>
>> +  MmVarGetNextVarHeader =
>> (SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME
>> *)(MmCommunicateBuffer + MM_VARIABLE_COMM_BUFFER_OFFSET);
>>
>> +
>>
>> +  // Variable GUID
>>
>> +  CopyMem ((VOID *)&MmVarGetNextVarHeader->Guid, VariableGuid,
>> sizeof (GUID));
>>
>> +
>>
>> +  // Program the maximal length of name we can accept.
>>
>> +  MmVarGetNextVarHeader->NameSize = *VariableNameSize;
>>
>> +
>>
>> +  // Populate incoming variable name
>>
>> +  CopyMem ((VOID *)&MmVarGetNextVarHeader->Name, VariableName,
>> MmVarGetNextVarHeader->NameSize);
>>
>> +
>>
>> +  // Send the MM request using MmCommunicationPei
>>
>> +  Status = PopulateHeaderAndCommunicate (MmCommunicateBuffer,
>> MessageSize, SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME);
>>
>> +  if (EFI_ERROR (Status)) {
>>
>> +    // We received an error from either communicate or Variable Service.
>>
>> +    if (Status != EFI_BUFFER_TOO_SMALL) {
>>
>> +      DEBUG ((DEBUG_ERROR, "%a - Communite to MM for variable
>> service errored: %r\n", __func__, Status));
>>
>> +    }
>>
>> +
>>
>> +    goto Exit;
>>
>> +  }
>>
>> +
>>
>> +  Status = EFI_SUCCESS;
>>
>> +
>>
>> +  // User provided buffer is too small
>>
>> +  if (*VariableNameSize < MmVarGetNextVarHeader->NameSize) {
>>
>> +    Status = EFI_BUFFER_TOO_SMALL;
>>
>> +  }
>>
>> +
>>
>> +Exit:
>>
>> +  // Update the name size to be returned
>>
>> +  *VariableNameSize = MmVarGetNextVarHeader->NameSize;
>>
>> +
>>
>> +  if (Status == EFI_SUCCESS) {
>>
>> +    CopyMem ((VOID *)VariableName, (UINT8
>> *)MmVarGetNextVarHeader->Name, *VariableNameSize);
>>
>> +    CopyMem ((VOID *)VariableGuid, (UINT8
>> *)&(MmVarGetNextVarHeader->Guid), sizeof (EFI_GUID));
>>
>> +  }
>>
>> +
>>
>> +  // Free the Communication Buffer
>>
>> +  if (MmCommunicateBuffer != NULL) {
>>
>> +    FreePages (MmCommunicateBuffer, RequiredPages);
>>
>> +  }
>>
>> +
>>
>> +  return Status;
>>
>> +}
>>
>> diff --git a/MdeModulePkg/MdeModulePkg.dsc
>> b/MdeModulePkg/MdeModulePkg.dsc
>> index 5b1f50e9c084..1aedfe280ae1 100644
>> --- a/MdeModulePkg/MdeModulePkg.dsc
>> +++ b/MdeModulePkg/MdeModulePkg.dsc
>> @@ -400,6 +400,7 @@ [Components]
>>     MdeModulePkg/Application/VariableInfo/VariableInfo.inf
>>
>>
>> MdeModulePkg/Universal/FaultTolerantWritePei/FaultTolerantWritePei.inf
>>
>>     MdeModulePkg/Universal/Variable/Pei/VariablePei.inf
>>
>> +  MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.inf
>>
>>     MdeModulePkg/Universal/WatchdogTimerDxe/WatchdogTimer.inf
>>
>>     MdeModulePkg/Universal/TimestampDxe/TimestampDxe.inf
>>
>>
>> MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteDxe.inf
>>
>> diff --git
>> a/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.h
>> b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.h
>> new file mode 100644
>> index 000000000000..0feed8cd1cb6
>> --- /dev/null
>> +++ b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.h
>> @@ -0,0 +1,134 @@
>> +/** @file -- MmVariablePei.h
>>
>> +  Provides interface for reading Secure System Variables during PEI.
>>
>> +
>>
>> +  Copyright (c) Microsoft Corporation.
>>
>> +  SPDX-License-Identifier: BSD-2-Clause-Patent
>>
>> +**/
>>
>> +
>>
>> +#ifndef PEI_MM_VARIABLE_LIB_H_
>>
>> +#define PEI_MM_VARIABLE_LIB_H_
>>
>> +
>>
>> +#include <PiPei.h>
>>
>> +#include <Uefi/UefiSpec.h>
>>
>> +
>>
>> +#include <Library/DebugLib.h>
>>
>> +#include <Library/PcdLib.h>
>>
>> +#include <Library/BaseMemoryLib.h>
>>
>> +#include <Library/PeimEntryPoint.h>
>>
>> +#include <Library/PeiServicesLib.h>
>>
>> +#include <Library/MemoryAllocationLib.h>
>>
>> +#include <Library/HobLib.h>
>>
>> +
>>
>> +#include <Guid/SmmVariableCommon.h>
>>
>> +
>>
>> +#include <Ppi/ReadOnlyVariable2.h>
>>
>> +#include <Ppi/MmCommunication.h>
>>
>> +
>>
>> +#include <Protocol/SmmVariable.h>
>>
>> +#include <Protocol/MmCommunication.h>
>>
>> +
>>
>> +/**
>>
>> +  Entry point of PEI Secure Variable read driver
>>
>> +
>>
>> +  @param  FileHandle   Handle of the file being invoked.
>>
>> +                       Type EFI_PEI_FILE_HANDLE is defined in
>> FfsFindNextFile().
>>
>> +  @param  PeiServices  General purpose services available to every
>> PEIM.
>>
>> +
>>
>> +  @retval EFI_SUCCESS  If the interface could be successfully installed
>>
>> +  @retval Others       Returned from PeiServicesInstallPpi()
>>
>> +**/
>>
>> +EFI_STATUS
>>
>> +EFIAPI
>>
>> +PeiMmVariableInitialize (
>>
>> +  IN       EFI_PEI_FILE_HANDLE  FileHandle,
>>
>> +  IN CONST EFI_PEI_SERVICES     **PeiServices
>>
>> +  );
>>
>> +
>>
>> +/**
>>
>> +
>>
>> +  This function enables the read of Secure Variables during PEI.
>>
>> +
>>
>> +  This function is using the Secure Variable Store.If the Data
>>
>> +  buffer is too small to hold the contents of the variable, the error
>>
>> +  EFI_BUFFER_TOO_SMALL is returned and DataSize is set to the required
>> buffer
>>
>> +  size to obtain the data.
>>
>> +
>>
>> +  The function performs the following:
>>
>> +
>>
>> +  1) Creates an MM request
>>
>> +  2) Fills out the following data structures for the Secure Variable
> Service
>> +
>> SMM_VARIABLE_COMMUNICATE_HEADER/SMM_VARIABLE_COMMUNICAT
>> E_ACCESS_VARIABLE
>>
>> +  3) Adds the MM data structures to the MM request.
>>
>> +  4) Sends the MM request to EL3 using MmCommunicationPeiLib.
>>
>> +  5) The MM request is sent to S-EL0.
>>
>> +  6) The MM request is then handled by the registered handler with GUID:
>> gEfiSmmVariableProtocolGuid
>>
>> +
>>
>> +  @param  This                  A pointer to this instance of the
>> EFI_PEI_READ_ONLY_VARIABLE2_PPI.
>>
>> +  @param  VariableName          A pointer to a null-terminated string
>> that is the variable's name.
>>
>> +  @param  VariableGuid          A pointer to an EFI_GUID that is the
>> variable's GUID. The combination of
>>
>> +                                VariableGuid and VariableName
>> must be unique.
>>
>> +  @param  Attributes            If non-NULL, on return, points to the
>> variable's attributes.
>>
>> +  @param  DataSize              On entry, points to the size in bytes
>> of the Data buffer.
>>
>> +                                On return, points to the size of the
>> data returned in Data.
>>
>> +  @param  Data                  Points to the buffer which will hold
>> the returned variable value.
>>
>> +                                May be NULL with a zero DataSize in
>> order to determine the size of the buffer needed.
>>
>> +
>>
>> +  @retval EFI_SUCCESS           The variable was read successfully.
>>
>> +  @retval EFI_NOT_FOUND         The variable was not found.
>>
>> +  @retval EFI_BUFFER_TOO_SMALL  The DataSize is too small for the
>> resulting data.
>>
>> +                                DataSize is updated with the size
>> required for
>>
>> +                                the specified variable.
>>
>> +  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid, DataSize
>> or Data is NULL.
>>
>> +  @retval EFI_DEVICE_ERROR      The variable could not be retrieved
>> because of a device error.
>>
>> +
>>
>> +**/
>>
>> +EFI_STATUS
>>
>> +EFIAPI
>>
>> +PeiMmGetVariable (
>>
>> +  IN CONST  EFI_PEI_READ_ONLY_VARIABLE2_PPI  *This,
>>
>> +  IN CONST  CHAR16                           *VariableName,
>>
>> +  IN CONST  EFI_GUID                         *VariableGuid,
>>
>> +  OUT       UINT32                           *Attributes,
>>
>> +  IN OUT    UINTN                            *DataSize,
>>
>> +  OUT       VOID                             *Data OPTIONAL
>>
>> +  );
>>
>> +
>>
>> +/**
>>
>> +  Return the next variable name and GUID.
>>
>> +
>>
>> +  This function is called multiple times to retrieve the VariableName
>>
>> +  and VariableGuid of all variables currently available in the system.
>>
>> +  On each call, the previous results are passed into the interface,
>>
>> +  and, on return, the interface returns the data for the next
>>
>> +  interface. When the entire variable list has been returned,
>>
>> +  EFI_NOT_FOUND is returned.
>>
>> +
>>
>> +  @param  This              A pointer to this instance of the
>> EFI_PEI_READ_ONLY_VARIABLE2_PPI.
>>
>> +
>>
>> +  @param  VariableNameSize  On entry, points to the size of the buffer
>> pointed to by VariableName.
>>
>> +                            On return, the size of the variable name
>> buffer.
>>
>> +  @param  VariableName      On entry, a pointer to a null-terminated
>> string that is the variable's name.
>>
>> +                            On return, points to the next variable's
>> null-terminated name string.
>>
>> +
>>
>> +  @param  VariableGuid      On entry, a pointer to an EFI_GUID that is
>> the variable's GUID.
>>
>> +                            On return, a pointer to the next variable's
>> GUID.
>>
>> +
>>
>> +  @retval EFI_SUCCESS           The variable was read successfully.
>>
>> +  @retval EFI_NOT_FOUND         The variable could not be found.
>>
>> +  @retval EFI_BUFFER_TOO_SMALL  The VariableNameSize is too small
>> for the resulting
>>
>> +                                data. VariableNameSize is updated
>> with the size
>>
>> +                                required for the specified variable.
>>
>> +  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid or
>>
>> +                                VariableNameSize is NULL.
>>
>> +  @retval EFI_DEVICE_ERROR      The variable could not be retrieved
>> because of a device error.
>>
>> +**/
>>
>> +EFI_STATUS
>>
>> +EFIAPI
>>
>> +PeiMmGetNextVariableName (
>>
>> +  IN CONST  EFI_PEI_READ_ONLY_VARIABLE2_PPI  *This,
>>
>> +  IN OUT UINTN                               *VariableNameSize,
>>
>> +  IN OUT CHAR16                              *VariableName,
>>
>> +  IN OUT EFI_GUID                            *VariableGuid
>>
>> +  );
>>
>> +
>>
>> +#endif /* PEI_MM_VARIABLE_LIB_H_ */
>>
>> diff --git
>> a/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.inf
>> b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.inf
>> new file mode 100644
>> index 000000000000..d122703e9b5d
>> --- /dev/null
>> +++ b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.inf
>> @@ -0,0 +1,43 @@
>> +## @file -- MmVariablePei.inf
>>
>> +# Provides interface for reading Secure System Variables during PEI.
>>
>> +#
>>
>> +# Copyright (c) Microsoft Corporation.
>>
>> +# SPDX-License-Identifier: BSD-2-Clause-Patent
>>
>> +##
>>
>> +
>>
>> +
>>
>> +[Defines]
>>
>> +  INF_VERSION                    = 0x00010005
>>
>> +  BASE_NAME                      = MmVariablePei
>>
>> +  FILE_GUID                      =
>> CD660A87-454B-4346-A35C-3D89BF8ECFAF
>>
>> +  MODULE_TYPE                    = PEIM
>>
>> +  VERSION_STRING                 = 1.0
>>
>> +  ENTRY_POINT                    = PeiMmVariableInitialize
>>
>> +
>>
>> +[Sources]
>>
>> +  MmVariablePei.c
>>
>> +  MmVariablePei.h
>>
>> +
>>
>> +[Packages]
>>
>> +  MdePkg/MdePkg.dec
>>
>> +  MdeModulePkg/MdeModulePkg.dec
>>
>> +
>>
>> +[LibraryClasses]
>>
>> +  PcdLib
>>
>> +  PeiServicesLib
>>
>> +  PeimEntryPoint
>>
>> +  MemoryAllocationLib
>>
>> +  HobLib
>>
>> +
>>
>> +[Pcd]
>>
>> +  gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize
>>
>> +
>>
>> +[Protocols]
>>
>> +  gEfiSmmVariableProtocolGuid             ## CONSUMES
>>
>> +
>>
>> +[Ppis]
>>
>> +  gEfiPeiReadOnlyVariable2PpiGuid         ## PRODUCES
>>
>> +  gEfiPeiMmCommunicationPpiGuid           ## CONSUMES
>>
>> +
>>
>> +[Depex]
>>
>> +  gEfiPeiMmCommunicationPpiGuid
>>
>> --
>> 2.40.1.windows.1
>>
>>
>>
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>> -=-=-=-=-=-=
>>
>
>
>
>
> 
>
>