REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3430

In PI Spec v1.7 Errata A, Vol.4, Sec 5.7 MM Communication Protocol, the
MessageLength field of EFI_MM_COMMUNICATE_HEADER (also derived as
EFI_SMM_COMMUNICATE_HEADER) is currently defined as type UINTN.

But this structure, as a generic definition, could be used for both PEI
and DXE MM communication. Thus for a system that supports PEI MM launch,
but operates PEI in 32bit mode and MM foundation in 64bit, the current
EFI_MM_COMMUNICATE_HEADER definition will cause structure parse error due
to UINTN being used.

The suggested change is to make the MessageLength field defined with
definitive size as below:
```
typedef struct {
EFI_GUID HeaderGuid;
UINT64 MessageLength;
UINT8 Data[ANYSIZE_ARRAY];
} EFI_MM_COMMUNICATE_HEADER;
```

Patch v1 branch: https://github.com/kuqin12/edk2/tree/BZ3398-MmCommunicate-Length

Cc: Jian J Wang <jian.j.wang@...>
Cc: Hao A Wu <hao.a.wu@...>
Cc: Eric Dong <eric.dong@...>
Cc: Ray Ni <ray.ni@...>
Cc: Michael D Kinney <michael.d.kinney@...>
Cc: Liming Gao <gaoliming@...>
Cc: Zhiguang Liu <zhiguang.liu@...>
Cc: Andrew Fish <afish@...>
Cc: Laszlo Ersek <lersek@...>
Cc: Leif Lindholm <leif@...>

Kun Qin (5):
EDK2 Code First: PI Specification: EFI_MM_COMMUNICATE_HEADER Update
MdeModulePkg: PiSmmIpl: Update MessageLength calculation for
MmCommunicate
MdeModulePkg: MemoryProfileInfo: Updated MessageLength calculation
MdeModulePkg: SmiHandlerProfileInfo: Updated MessageLength calculation
MdePkg: MmCommunication: Extend MessageLength field size to UINT64

MdeModulePkg/Application/MemoryProfileInfo/MemoryProfileInfo.c | 20 +++--
MdeModulePkg/Application/SmiHandlerProfileInfo/SmiHandlerProfileInfo.c | 8 +-
MdeModulePkg/Core/PiSmmCore/PiSmmIpl.c | 13 ++-
BZ3430-SpecChange.md | 88 ++++++++++++++++++++
MdeModulePkg/Core/PiSmmCore/PiSmmIpl.inf | 1 +
MdePkg/Include/Protocol/MmCommunication.h | 3 +-
6 files changed, 124 insertions(+), 9 deletions(-)
create mode 100644 BZ3430-SpecChange.md