Re: [PATCH v1 0/5] EDK2 Code First: PI Specification: Update EFI_MM_COMMUNICATE_HEADER

Marvin Häuser

Good day,

May I ask about two small things?

1) Was there any rationale as to e.g. code compatibility with choosing UINT64 for the data length? I understand that this is the maximum of the two as of currently, but I wonder whether a message length that exceeds the UINT32 range (4 GB!) can possibly be considered sane or a good idea.

2) Is it feasible yet with the current set of supported compilers to support flexible arrays?

Thank you for your work!

Best regards,

On 10.06.21 03:42, Kun Qin wrote:

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;

Patch v1 branch:

Cc: Jian J Wang <>
Cc: Hao A Wu <>
Cc: Eric Dong <>
Cc: Ray Ni <>
Cc: Michael D Kinney <>
Cc: Liming Gao <>
Cc: Zhiguang Liu <>
Cc: Andrew Fish <>
Cc: Laszlo Ersek <>
Cc: Leif Lindholm <>

Kun Qin (5):
EDK2 Code First: PI Specification: EFI_MM_COMMUNICATE_HEADER Update
MdeModulePkg: PiSmmIpl: Update MessageLength calculation for
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 ++- | 88 ++++++++++++++++++++
MdeModulePkg/Core/PiSmmCore/PiSmmIpl.inf | 1 +
MdePkg/Include/Protocol/MmCommunication.h | 3 +-
6 files changed, 124 insertions(+), 9 deletions(-)
create mode 100644

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