MdeModulePkg/Include/Ppi/SmmAccess.h

/** @file
  EFI SMM Access PPI definition.

  This PPI is used to control the visibility of the SMRAM on the platform.
  It abstracts the location and characteristics of SMRAM.  The expectation is
  that the north bridge or memory controller would publish this PPI.

  The principal functionality found in the memory controller includes the following:
  - Exposing the SMRAM to all non-SMM agents, or the "open" state
  - Shrouding the SMRAM to all but the SMM agents, or the "closed" state
  - Preserving the system integrity, or "locking" the SMRAM, such that the settings cannot be
    perturbed by either boot service or runtime agents

Copyright (c) 2010 - 2018, Intel Corporation. All rights reserved.<BR>

SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#ifndef _SMM_ACCESS_PPI_H_
#define _SMM_ACCESS_PPI_H_

#define PEI_SMM_ACCESS_PPI_GUID \
  { 0x268f33a9, 0xcccd, 0x48be, { 0x88, 0x17, 0x86, 0x5, 0x3a, 0xc3, 0x2e, 0xd6 }}

typedef struct _PEI_SMM_ACCESS_PPI PEI_SMM_ACCESS_PPI;

/**
  Opens the SMRAM area to be accessible by a PEIM driver.

  This function "opens" SMRAM so that it is visible while not inside of SMM. The function should
  return EFI_UNSUPPORTED if the hardware does not support hiding of SMRAM. The function
  should return EFI_DEVICE_ERROR if the SMRAM configuration is locked.

  @param  PeiServices            General purpose services available to every PEIM.
  @param  This                   The pointer to the SMM Access Interface.
  @param  DescriptorIndex        The region of SMRAM to Open.

  @retval EFI_SUCCESS            The region was successfully opened.
  @retval EFI_DEVICE_ERROR       The region could not be opened because locked by chipset.
  @retval EFI_INVALID_PARAMETER  The descriptor index was out of bounds.

**/
typedef
EFI_STATUS
(EFIAPI *PEI_SMM_OPEN)(
  IN EFI_PEI_SERVICES                **PeiServices,
  IN PEI_SMM_ACCESS_PPI              *This,
  IN UINTN                           DescriptorIndex
  );

/**
  Inhibits access to the SMRAM.

  This function "closes" SMRAM so that it is not visible while outside of SMM. The function should
  return EFI_UNSUPPORTED if the hardware does not support hiding of SMRAM.

  @param  PeiServices              General purpose services available to every PEIM.
  @param  This                     The pointer to the SMM Access Interface.
  @param  DescriptorIndex          The region of SMRAM to Close.

  @retval EFI_SUCCESS              The region was successfully closed.
  @retval EFI_DEVICE_ERROR         The region could not be closed because locked by chipset.
  @retval EFI_INVALID_PARAMETER    The descriptor index was out of bounds.

**/
typedef
EFI_STATUS
(EFIAPI *PEI_SMM_CLOSE)(
  IN EFI_PEI_SERVICES                **PeiServices,
  IN PEI_SMM_ACCESS_PPI              *This,
  IN UINTN                           DescriptorIndex
  );

/**
  Inhibits access to the SMRAM.

  This function prohibits access to the SMRAM region.  This function is usually implemented such
  that it is a write-once operation.

  @param  PeiServices              General purpose services available to every PEIM.
  @param  This                     The pointer to the SMM Access Interface.
  @param  DescriptorIndex          The region of SMRAM to Close.

  @retval EFI_SUCCESS            The region was successfully locked.
  @retval EFI_DEVICE_ERROR       The region could not be locked because at least
                                 one range is still open.
  @retval EFI_INVALID_PARAMETER  The descriptor index was out of bounds.

**/
typedef
EFI_STATUS
(EFIAPI *PEI_SMM_LOCK)(
  IN EFI_PEI_SERVICES                **PeiServices,
  IN PEI_SMM_ACCESS_PPI              *This,
  IN UINTN                           DescriptorIndex
  );

/**
  Queries the memory controller for the possible regions that will support SMRAM.

  @param  PeiServices           General purpose services available to every PEIM.
  @param This                   The pointer to the SmmAccessPpi Interface.
  @param SmramMapSize           The pointer to the variable containing size of the
                                buffer to contain the description information.
  @param SmramMap               The buffer containing the data describing the Smram
                                region descriptors.

  @retval EFI_BUFFER_TOO_SMALL  The user did not provide a sufficient buffer.
  @retval EFI_SUCCESS           The user provided a sufficiently-sized buffer.

**/
typedef
EFI_STATUS
(EFIAPI *PEI_SMM_CAPABILITIES)(
  IN EFI_PEI_SERVICES                **PeiServices,
  IN PEI_SMM_ACCESS_PPI              *This,
  IN OUT UINTN                       *SmramMapSize,
  IN OUT EFI_SMRAM_DESCRIPTOR        *SmramMap
  );

///
///  EFI SMM Access PPI is used to control the visibility of the SMRAM on the platform.
///  It abstracts the location and characteristics of SMRAM. The platform should report
///  all MMRAM via PEI_SMM_ACCESS_PPI. The expectation is that the north bridge or
///  memory controller would publish this PPI.
///
struct _PEI_SMM_ACCESS_PPI {
  PEI_SMM_OPEN            Open;
  PEI_SMM_CLOSE           Close;
  PEI_SMM_LOCK            Lock;
  PEI_SMM_CAPABILITIES    GetCapabilities;
  BOOLEAN                 LockState;
  BOOLEAN                 OpenState;
};

extern EFI_GUID  gPeiSmmAccessPpiGuid;

#endif