[RFC v3 06/15] OvmfPkg/DxeBmDmaLib: Import DxeBmDmaLib package

[Brijesh Singh <brijesh.ksingh@gmail.com>]

From: Brijesh Singh <brijesh.singh@amd.com>

Import DxeBmDmaLib package in OvmfPkg, we need to modify the package to
include SEV support.

The BmDmaLib is proposed by Leo Duran
https://lists.01.org/pipermail/edk2-devel/2017-March/008109.html

NOTE: This patch is still under discussion and have not been accepted
upstream.


Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/OvmfPkgIa32.dsc                     |   2 +-
 OvmfPkg/OvmfPkgIa32X64.dsc                  |   2 +-
 OvmfPkg/OvmfPkgX64.dsc                      |   2 +-
 OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf |  41 +++
 OvmfPkg/Include/Library/BmDmaLib.h          | 161 +++++++++
 OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c   | 351 ++++++++++++++++++++
 6 files changed, 556 insertions(+), 3 deletions(-)

diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index 04e7e0fe948f..0475e10e484a 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -91,7 +91,7 @@ [LibraryClasses]
   UefiHiiServicesLib|MdeModulePkg/Library/UefiHiiServicesLib/UefiHiiServicesLib.inf
   HiiLib|MdeModulePkg/Library/UefiHiiLib/UefiHiiLib.inf
   SortLib|MdeModulePkg/Library/UefiSortLib/UefiSortLib.inf
-  BmDmaLib|MdeModulePkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
+  BmDmaLib|OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
   UefiBootManagerLib|MdeModulePkg/Library/UefiBootManagerLib/UefiBootManagerLib.inf
   BootLogoLib|MdeModulePkg/Library/BootLogoLib/BootLogoLib.inf
   FileExplorerLib|MdeModulePkg/Library/FileExplorerLib/FileExplorerLib.inf
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index 882dc8daacc8..408ab37e4a88 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -96,7 +96,7 @@ [LibraryClasses]
   UefiHiiServicesLib|MdeModulePkg/Library/UefiHiiServicesLib/UefiHiiServicesLib.inf
   HiiLib|MdeModulePkg/Library/UefiHiiLib/UefiHiiLib.inf
   SortLib|MdeModulePkg/Library/UefiSortLib/UefiSortLib.inf
-  BmDmaLib|MdeModulePkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
+  BmDmaLib|OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
   UefiBootManagerLib|MdeModulePkg/Library/UefiBootManagerLib/UefiBootManagerLib.inf
   BootLogoLib|MdeModulePkg/Library/BootLogoLib/BootLogoLib.inf
   FileExplorerLib|MdeModulePkg/Library/FileExplorerLib/FileExplorerLib.inf
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 3cfd09a3f260..dd3674a5d6dc 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -96,7 +96,7 @@ [LibraryClasses]
   UefiHiiServicesLib|MdeModulePkg/Library/UefiHiiServicesLib/UefiHiiServicesLib.inf
   HiiLib|MdeModulePkg/Library/UefiHiiLib/UefiHiiLib.inf
   SortLib|MdeModulePkg/Library/UefiSortLib/UefiSortLib.inf
-  BmDmaLib|MdeModulePkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
+  BmDmaLib|OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
   UefiBootManagerLib|MdeModulePkg/Library/UefiBootManagerLib/UefiBootManagerLib.inf
   BootLogoLib|MdeModulePkg/Library/BootLogoLib/BootLogoLib.inf
   FileExplorerLib|MdeModulePkg/Library/FileExplorerLib/FileExplorerLib.inf
diff --git a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
new file mode 100644
index 000000000000..4ddb27d578bc
--- /dev/null
+++ b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
@@ -0,0 +1,41 @@
+## @file
+#
+# DMA abstraction library APIs. Based on PCI IO protocol DMA abstractions.
+#
+#  Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
+#  Copyright (c) 2017, AMD Inc. All rights reserved.<BR>
+#
+#  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
+#  http://opensource.org/licenses/bsd-license.php
+#
+#  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                    = 0x00010005
+  BASE_NAME                      = DxeBmDmaLib
+  FILE_GUID                      = daa403e0-071d-44ef-95cf-7f2472e4a4d5
+  MODULE_TYPE                    = DXE_DRIVER
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = BmDmaLib|DXE_DRIVER
+
+[Sources.common]
+  DxeBmDmaLib.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  MdeModulePkg/MdeModulePkg.dec
+
+[LibraryClasses]
+  BaseLib
+  BaseMemoryLib
+  DebugLib
+  DxeServicesTableLib
+  MemoryAllocationLib
+  UefiBootServicesTableLib
+
+
diff --git a/OvmfPkg/Include/Library/BmDmaLib.h b/OvmfPkg/Include/Library/BmDmaLib.h
new file mode 100644
index 000000000000..070340c9cca8
--- /dev/null
+++ b/OvmfPkg/Include/Library/BmDmaLib.h
@@ -0,0 +1,161 @@
+/** @file
+  DMA abstraction library APIs. Based on PCI IO protocol DMA abstractions.
+
+  Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
+  Copyright (c) 2017, AMD Inc. All rights reserved.<BR>
+
+  DMA Bus Master Read Operation:
+    Call BmDmaMap() for DmaOperationBusMasterRead.
+    Program the DMA Bus Master with the DeviceAddress returned by BmDmaMap().
+    Start the DMA Bus Master.
+    Wait for DMA Bus Master to complete the read operation.
+    Call BmDmaUnmap().
+
+  DMA Bus Master Write Operation:
+    Call BmDmaMap() for DmaOperationBusMasterWrite.
+    Program the DMA Bus Master with the DeviceAddress returned by BmDmaMap().
+    Start the DMA Bus Master.
+    Wait for DMA Bus Master to complete the write operation.
+    Call BmDmaUnmap().
+
+  DMA Bus Master Common Buffer Operation:
+    Call BmDmaAllocateBuffer() to allocate a common buffer.
+    Call BmDmaMap() for DmaOperationBusMasterCommonBuffer.
+    Program the DMA Bus Master with the DeviceAddress returned by BmDmaMap().
+    The common buffer can now be accessed equally by the processor and the DMA bus master.
+    Call BmDmaUnmap().
+    Call BmDmaFreeBuffer().
+
+  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
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+ Derived from:
+   EmbeddedPkg/Include/Library/DmaLib.h
+
+**/
+
+#ifndef __BM_DMA_LIB_H__
+#define __BM_DMA_LIB_H__
+
+
+typedef enum {
+  ///
+  /// A read operation from system memory by a bus master.
+  ///
+  DmaOperationBusMasterRead,
+  ///
+  /// A write operation from system memory by a bus master.
+  ///
+  DmaOperationBusMasterWrite,
+  ///
+  /// Provides both read and write access to system memory by both the processor and a
+  /// bus master. The buffer is coherent from both the processor's and the bus master's point of view.
+  ///
+  DmaOperationBusMasterCommonBuffer,
+  DmaOperationBusMasterMaximum
+} BM_DMA_OPERATION;
+
+
+/**
+  Provides the DMA controller-specific addresses needed to access system memory.
+
+  Operation is relative to the DMA bus master.
+
+  @param  DmaAbove4GB           Indicates capability of DMA operations above 4GB.
+  @param  Operation             Indicates if the bus master is going to read or write to system memory.
+  @param  HostAddress           The system memory address to map to the DMA controller.
+  @param  NumberOfBytes         On input the number of bytes to map. On output the number of bytes
+                                that were mapped.
+  @param  DeviceAddress         The resulting map address for the bus master controller to use to
+                                access the hosts HostAddress.
+  @param  Mapping               A resulting value to pass to BmDmaUnmap().
+
+  @retval EFI_SUCCESS           The range was mapped for the returned NumberOfBytes.
+  @retval EFI_UNSUPPORTED       The HostAddress cannot be mapped as a common buffer.
+  @retval EFI_INVALID_PARAMETER One or more parameters are invalid.
+  @retval EFI_OUT_OF_RESOURCES  The request could not be completed due to a lack of resources.
+  @retval EFI_DEVICE_ERROR      The system hardware could not map the requested address.
+
+**/
+EFI_STATUS
+EFIAPI
+BmDmaMap (
+  IN     BOOLEAN           DmaAbove4GB,
+  IN     BM_DMA_OPERATION  Operation,
+  IN     VOID              *HostAddress,
+  IN OUT UINTN             *NumberOfBytes,
+  OUT    PHYSICAL_ADDRESS  *DeviceAddress,
+  OUT    VOID              **Mapping
+  );
+
+
+/**
+  Completes the DmaOperationBusMasterRead/Write/CommonBuffer operation
+  and releases any corresponding resources.
+
+  @param  Mapping               The mapping value returned from BmDmaMap().
+
+  @retval EFI_SUCCESS           The range was unmapped.
+  @retval EFI_DEVICE_ERROR      The data was not committed to the target system memory.
+
+**/
+EFI_STATUS
+EFIAPI
+BmDmaUnmap (
+  IN  VOID                 *Mapping
+  );
+
+
+/**
+  Allocates pages that are suitable for a BmDmaMap() of type DmaOperationBusMasterCommonBuffer.
+
+  @param  DmaAbove4GB           Indicates capability of DMA operations above 4GB.
+  @param  MemoryType            The type of memory to allocate: EfiBootServicesData or
+                                EfiRuntimeServicesData.
+  @param  Pages                 The number of pages to allocate.
+  @param  HostAddress           A pointer to store the base system memory address of the
+                                allocated range.
+
+  @retval EFI_SUCCESS           The requested memory pages were allocated.
+  @retval EFI_UNSUPPORTED       Attributes is unsupported. The only legal attribute bits are
+                                MEMORY_WRITE_COMBINE and MEMORY_CACHED.
+  @retval EFI_INVALID_PARAMETER One or more parameters are invalid.
+  @retval EFI_OUT_OF_RESOURCES  The memory pages could not be allocated.
+
+**/
+EFI_STATUS
+EFIAPI
+BmDmaAllocateBuffer (
+  IN  BOOLEAN              DmaAbove4GB,
+  IN  EFI_MEMORY_TYPE      MemoryType,
+  IN  UINTN                Pages,
+  OUT VOID                 **HostAddress
+  );
+
+
+/**
+  Frees memory that was allocated with BmDmaAllocateBuffer().
+
+  @param  HostAddress           The base system memory address of the allocated range.
+  @param  Pages                 The number of pages to free.
+
+  @retval EFI_SUCCESS           The requested memory pages were freed.
+  @retval EFI_INVALID_PARAMETER The memory range specified by HostAddress and Pages
+                                was not allocated with BmDmaAllocateBuffer().
+
+**/
+EFI_STATUS
+EFIAPI
+BmDmaFreeBuffer (
+  IN  VOID                 *HostAddress,
+  IN  UINTN                Pages
+  );
+
+
+#endif
+
diff --git a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
new file mode 100644
index 000000000000..4a6a704f9aa5
--- /dev/null
+++ b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
@@ -0,0 +1,351 @@
+/** @file
+  DMA abstraction library APIs. Based on PCI IO protocol DMA abstractions.
+
+  Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
+  Copyright (c) 2017, AMD Inc. All rights reserved.<BR>
+
+  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
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+  Derived from:
+   MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
+
+**/
+
+#include <PiDxe.h>
+#include <Library/BaseLib.h>
+#include <Library/BaseMemoryLib.h>
+#include <Library/DebugLib.h>
+#include <Library/DxeServicesTableLib.h>
+#include <Library/MemoryAllocationLib.h>
+#include <Library/UefiBootServicesTableLib.h>
+#include <Library/BmDmaLib.h>
+
+
+#define FORCE_BELOW_4GB_TRUE   TRUE
+#define FORCE_BELOW_4GB_FALSE  FALSE
+#define NO_MAPPING             (VOID *) (UINTN) -1
+
+
+typedef struct {
+  BM_DMA_OPERATION      Operation;
+  UINTN                 NumberOfBytes;
+  UINTN                 NumberOfPages;
+  EFI_PHYSICAL_ADDRESS  HostAddress;
+  EFI_PHYSICAL_ADDRESS  MappedHostAddress;
+} MAP_INFO;
+
+
+EFI_STATUS
+AllocateBounceBuffer (
+  IN     BOOLEAN               ForceBelow4GB,
+  IN     BM_DMA_OPERATION      Operation,
+  IN     EFI_PHYSICAL_ADDRESS  HostAddress,
+  IN OUT UINTN                 *NumberOfBytes,
+  OUT    PHYSICAL_ADDRESS      *DeviceAddress,
+  OUT    VOID                  **Mapping
+  )
+{
+  EFI_STATUS         Status;
+  MAP_INFO           *MapInfo;
+  EFI_ALLOCATE_TYPE  AllocateType;
+
+  //
+  // Allocate a MAP_INFO structure to remember the mapping when Unmap() is
+  // called later.
+  //
+  MapInfo = AllocatePool (sizeof (MAP_INFO));
+  if (MapInfo == NULL) {
+    *NumberOfBytes = 0;
+    return EFI_OUT_OF_RESOURCES;
+  }
+
+  //
+  // Initialize the MAP_INFO structure
+  //
+  MapInfo->Operation     = Operation;
+  MapInfo->NumberOfBytes = *NumberOfBytes;
+  MapInfo->NumberOfPages = EFI_SIZE_TO_PAGES (MapInfo->NumberOfBytes);
+  MapInfo->HostAddress   = HostAddress;
+
+  if (ForceBelow4GB) {
+    //
+    // Limit allocations to memory below 4GB
+    //
+    AllocateType = AllocateMaxAddress;
+    MapInfo->MappedHostAddress = SIZE_4GB - 1;
+  } else {
+    AllocateType = AllocateAnyPages;
+  }
+
+  //
+  // Allocate DMA bounce buffer
+  //
+  Status = gBS->AllocatePages (
+                  AllocateType,
+                  EfiBootServicesData,
+                  MapInfo->NumberOfPages,
+                  &MapInfo->MappedHostAddress
+                  );
+
+  if (EFI_ERROR (Status)) {
+    FreePool (MapInfo);
+    *NumberOfBytes = 0;
+    return Status;
+  }
+
+  //
+  // If this is a read operation from the Bus Master's point of view,
+  // then copy the contents of the real buffer into the mapped buffer
+  // so the Bus Master can read the contents of the real buffer.
+  //
+  if (Operation ==  DmaOperationBusMasterRead) {
+    CopyMem (
+      (VOID *) (UINTN) MapInfo->MappedHostAddress,
+      (VOID *) (UINTN) MapInfo->HostAddress,
+      MapInfo->NumberOfBytes
+      );
+  }
+
+  //
+  // The DeviceAddress is the address of the mapped buffer
+  //
+  *DeviceAddress = MapInfo->MappedHostAddress;
+
+  //
+  // Return a pointer to the MAP_INFO structure in Mapping
+  //
+  *Mapping = MapInfo;
+
+  return EFI_SUCCESS;
+}
+
+
+/**
+  Provides the DMA controller-specific addresses needed to access system memory.
+
+  Operation is relative to the DMA bus master.
+
+  @param  DmaAbove4GB           Indicates capability of DMA operations above 4GB.
+  @param  Operation             Indicates if the bus master is going to read or write to system memory.
+  @param  HostAddress           The system memory address to map to the DMA controller.
+  @param  NumberOfBytes         On input the number of bytes to map. On output the number of bytes
+                                that were mapped.
+  @param  DeviceAddress         The resulting map address for the bus master controller to use to
+                                access the hosts HostAddress.
+  @param  Mapping               A resulting value to pass to BmDmaUnmap().
+
+  @retval EFI_SUCCESS           The range was mapped for the returned NumberOfBytes.
+  @retval EFI_UNSUPPORTED       The HostAddress cannot be mapped as a common buffer.
+  @retval EFI_INVALID_PARAMETER One or more parameters are invalid.
+  @retval EFI_OUT_OF_RESOURCES  The request could not be completed due to a lack of resources.
+  @retval EFI_DEVICE_ERROR      The system hardware could not map the requested address.
+
+**/
+EFI_STATUS
+EFIAPI
+BmDmaMap (
+  IN     BOOLEAN           DmaAbove4GB,
+  IN     BM_DMA_OPERATION  Operation,
+  IN     VOID              *HostAddress,
+  IN OUT UINTN             *NumberOfBytes,
+  OUT    PHYSICAL_ADDRESS  *DeviceAddress,
+  OUT    VOID              **Mapping
+  )
+{
+  EFI_PHYSICAL_ADDRESS  PhysicalAddress;
+
+  //
+  // Check for invalid inputs
+  //
+  if (HostAddress == NULL || NumberOfBytes == NULL || DeviceAddress == NULL ||
+      Mapping == NULL || (UINT32) Operation >= DmaOperationBusMasterMaximum) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  PhysicalAddress = (EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress;
+  if (DmaAbove4GB || (PhysicalAddress + *NumberOfBytes) <= SIZE_4GB) {
+    //
+    // If we CAN handle DMA above 4GB or the transfer is below 4GB,
+    // the DeviceAddress is simply the HostAddress
+    //
+    *DeviceAddress = PhysicalAddress;
+    *Mapping       = NO_MAPPING;
+
+    return EFI_SUCCESS;
+  }
+
+  //
+  // If we cannot handle DMA above 4GB and any part of the DMA transfer
+  // being is above 4GB, then map the DMA transfer to a buffer below 4GB.
+  //
+  if (Operation == DmaOperationBusMasterCommonBuffer) {
+    //
+    // Common Buffer operations cannot be remapped, so return an error.
+    //
+    return EFI_UNSUPPORTED;
+  }
+
+  return AllocateBounceBuffer (
+           FORCE_BELOW_4GB_TRUE,
+           Operation,
+           PhysicalAddress,
+           NumberOfBytes,
+           DeviceAddress,
+           Mapping
+           );
+}
+
+
+/**
+  Completes the DmaOperationBusMasterRead/Write/CommonBuffer operation
+  and releases any corresponding resources.
+
+  @param  Mapping               The mapping value returned from BmDmaMap().
+
+  @retval EFI_SUCCESS           The range was unmapped.
+  @retval EFI_DEVICE_ERROR      The data was not committed to the target system memory.
+
+**/
+EFI_STATUS
+EFIAPI
+BmDmaUnmap (
+  IN  VOID                 *Mapping
+  )
+{
+  MAP_INFO  *MapInfo;
+
+  //
+  // Check for invalid inputs
+  //
+  if (Mapping == NULL) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  //
+  // See if the Map() operation associated with this Unmap() required a mapping
+  // buffer. If a mapping buffer was not required, then this function simply
+  // returns EFI_SUCCESS.
+  //
+  if (Mapping == NO_MAPPING) {
+    return EFI_SUCCESS;
+  }
+
+  //
+  // If this is a write operation from the Bus Master's point of view,
+  // then copy the contents of the mapped buffer into the real buffer
+  // so the processor can read the contents of the real buffer.
+  //
+  MapInfo = (MAP_INFO *)Mapping;
+  if (MapInfo->Operation == DmaOperationBusMasterWrite) {
+    CopyMem (
+      (VOID *) (UINTN) MapInfo->HostAddress,
+      (VOID *) (UINTN) MapInfo->MappedHostAddress,
+      MapInfo->NumberOfBytes
+      );
+  }
+
+  //
+  // Free the mapped buffer and the MAP_INFO structure.
+  //
+  gBS->FreePages (MapInfo->MappedHostAddress, MapInfo->NumberOfPages);
+  FreePool (Mapping);
+  return EFI_SUCCESS;
+}
+
+
+/**
+  Allocates pages that are suitable for a BmDmaMap() of type DmaOperationBusMasterCommonBuffer.
+
+  @param  DmaAbove4GB           Indicates capability of DMA operations above 4GB.
+  @param  MemoryType            The type of memory to allocate: EfiBootServicesData or
+                                EfiRuntimeServicesData.
+  @param  Pages                 The number of pages to allocate.
+  @param  HostAddress           A pointer to store the base system memory address of the
+                                allocated range.
+
+  @retval EFI_SUCCESS           The requested memory pages were allocated.
+  @retval EFI_UNSUPPORTED       Attributes is unsupported. The only legal attribute bits are
+                                MEMORY_WRITE_COMBINE and MEMORY_CACHED.
+  @retval EFI_INVALID_PARAMETER One or more parameters are invalid.
+  @retval EFI_OUT_OF_RESOURCES  The memory pages could not be allocated.
+
+**/
+EFI_STATUS
+EFIAPI
+BmDmaAllocateBuffer (
+  IN  BOOLEAN              DmaAbove4GB,
+  IN  EFI_MEMORY_TYPE      MemoryType,
+  IN  UINTN                Pages,
+  OUT VOID                 **HostAddress
+  )
+{
+  EFI_STATUS           Status;
+  EFI_PHYSICAL_ADDRESS PhysicalAddress;
+  EFI_ALLOCATE_TYPE    AllocateType;
+
+  //
+  // Check for invalid inputs
+  //
+  if (HostAddress == NULL) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  //
+  // The only valid memory types are EfiBootServicesData and
+  // EfiRuntimeServicesData
+  //
+  if (MemoryType != EfiBootServicesData &&
+      MemoryType != EfiRuntimeServicesData) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  if (DmaAbove4GB) {
+    AllocateType = AllocateAnyPages;
+  } else {
+    //
+    // Limit allocations to memory below 4GB
+    //
+    AllocateType    = AllocateMaxAddress;
+    PhysicalAddress = (EFI_PHYSICAL_ADDRESS) (SIZE_4GB - 1);
+  }
+  Status = gBS->AllocatePages (
+                  AllocateType,
+                  MemoryType,
+                  Pages,
+                  &PhysicalAddress
+                  );
+  if (!EFI_ERROR (Status)) {
+    *HostAddress = (VOID *) (UINTN) PhysicalAddress;
+  }
+
+  return Status;
+}
+
+
+/**
+  Frees memory that was allocated with BmDmaAllocateBuffer().
+
+  @param  HostAddress           The base system memory address of the allocated range.
+  @param  Pages                 The number of pages to free.
+
+  @retval EFI_SUCCESS           The requested memory pages were freed.
+  @retval EFI_INVALID_PARAMETER The memory range specified by HostAddress and Pages
+                                was not allocated with BmDmaAllocateBuffer().
+
+**/
+EFI_STATUS
+EFIAPI
+BmDmaFreeBuffer (
+  IN  VOID                 *HostAddress,
+  IN  UINTN                Pages
+  )
+{
+  return gBS->FreePages ((EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress, Pages);
+}
+
-- 
2.7.4