Re: [edk2-devel] [PATCH v3 2/7] MdePkg: MmCommunication: Introduce EFI_MM_COMMUNICATE_HEADER_V3 to MdePkg

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

Hi Ray,

This same header will be commonly used for both MM communicate PPI and 
Protocol. If including this definition in MmCommunicate protocol header, 
the potential PEIM that installs MM communicate PPI will need to include 
a PPI header as well as the aforementioned protocol header, which to me 
seems counter-intuitive.

I think PiMultiPhase header seems to be a file more ideal to resolve the 
entanglement above, as this structure indeed covers multiple phases 
during boot process.

Please let me know if you have any other thoughts.

Thanks,
Kun

On 08/16/2021 22:50, Ni, Ray wrote:
> Can you kindly explain why you choose to define the definitions in PiMultiPhase.h instead of MmCommunication.h?
> 
> Thanks,
> Ray
> 
>> -----Original Message-----
>> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Kun Qin
>> Sent: Tuesday, August 17, 2021 1:08 PM
>> To: devel@edk2.groups.io
>> Cc: Kinney, Michael D <michael.d.kinney@intel.com>; Liming Gao <gaoliming@byosoft.com.cn>; Liu, Zhiguang
>> <zhiguang.liu@intel.com>; Wu, Hao A <hao.a.wu@intel.com>; Marvin Häuser <mhaeuser@posteo.de>; Bret Barkelew
>> <Bret.Barkelew@microsoft.com>; Michael Kubacki <michael.kubacki@microsoft.com>
>> Subject: [edk2-devel] [PATCH v3 2/7] MdePkg: MmCommunication: Introduce EFI_MM_COMMUNICATE_HEADER_V3 to
>> MdePkg
>>
>> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3398
>> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3430
>>
>> This change introduces a new definition for MM communicate header
>> structure, intending to provide better portability between different
>> architectures (IA32 & X64) and adapt to flexible array supported by
>> modern compilers.
>>
>> The original MessageLength field of EFI_MM_COMMUNICATE_HEADER, as a
>> generic definition, was used for both PEI and DXE MM communication. On 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 used. This introduction
>> removes the architecture dependent field by defining this field as
>> UINT64.
>>
>> The new signature could help identifying whether the data received is
>> compiliant with this new data structure, which will help for binary
>> release modules to identify usage of legacy data structure.
>>
>> Version field is also added to indicate the current version of header in
>> case there is need for minor modification in the future.
>>
>> The data field of MM communicate message is replaced with flexible array
>> to allow users not having to consume extra data during communicate and
>> author code more intrinsically.
>>
>> Cc: Michael D Kinney <michael.d.kinney@intel.com>
>> Cc: Liming Gao <gaoliming@byosoft.com.cn>
>> Cc: Zhiguang Liu <zhiguang.liu@intel.com>
>> Cc: Hao A Wu <hao.a.wu@intel.com>
>> Cc: Marvin Häuser <mhaeuser@posteo.de>
>> Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
>> Cc: Michael Kubacki <michael.kubacki@microsoft.com>
>>
>> Signed-off-by: Kun Qin <kuqin12@gmail.com>
>> ---
>>
>> Notes:
>>      v3:
>>      - Newly introduced communicate v3
>>      - Used flexible arrays [Marvin]
>>      - Added static assert [Michael]
>>
>>   MdePkg/Include/Pi/PiMultiPhase.h | 55 ++++++++++++++++++++
>>   MdePkg/MdePkg.dec                |  5 ++
>>   2 files changed, 60 insertions(+)
>>
>> diff --git a/MdePkg/Include/Pi/PiMultiPhase.h b/MdePkg/Include/Pi/PiMultiPhase.h
>> index 89280d9d3506..8c60338091b3 100644
>> --- a/MdePkg/Include/Pi/PiMultiPhase.h
>> +++ b/MdePkg/Include/Pi/PiMultiPhase.h
>> @@ -103,6 +103,17 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
>>   #define EFI_SMRAM_CLOSED                EFI_MMRAM_CLOSED
>>   #define EFI_SMRAM_LOCKED                EFI_MMRAM_LOCKED
>>
>> +///
>> +/// MM Communicate header constants
>> +///
>> +#define COMMUNICATE_HEADER_V3_GUID \
>> +  { \
>> +    0x68e8c853, 0x2ba9, 0x4dd7, { 0x9a, 0xc0, 0x91, 0xe1, 0x61, 0x55, 0xc9, 0x35 } \
>> +  }
>> +
>> +#define EFI_MM_COMMUNICATE_HEADER_V3_SIGNATURE  0x4D434833 // "MCH3"
>> +#define EFI_MM_COMMUNICATE_HEADER_V3_VERSION    3
>> +
>>   ///
>>   /// Structure describing a MMRAM region and its accessibility attributes.
>>   ///
>> @@ -149,6 +160,48 @@ typedef struct _EFI_MM_RESERVED_MMRAM_REGION {
>>     UINT64                  MmramReservedSize;
>>   } EFI_MM_RESERVED_MMRAM_REGION;
>>
>> +#pragma pack(1)
>> +
>> +///
>> +/// To avoid confusion in interpreting frames, the buffer communicating to MM core through
>> +/// EFI_MM_COMMUNICATE3 or later should always start with EFI_MM_COMMUNICATE_HEADER_V3.
>> +///
>> +typedef struct {
>> +  ///
>> +  /// Indicator GUID for MM core that the communication buffer is compliant with this v3 header.
>> +  /// Must be gCommunicateHeaderV3Guid.
>> +  ///
>> +  EFI_GUID  HeaderGuid;
>> +  ///
>> +  /// Signature to indicate data is compliant with new MM communicate header structure.
>> +  /// Must be "MCH3".
>> +  ///
>> +  UINT32    Signature;
>> +  ///
>> +  /// MM communicate data format version, MM foundation entry point should check if incoming
>> +  /// data is a supported format before proceeding.
>> +  /// Must be 3.
>> +  ///
>> +  UINT32    Version;
>> +  ///
>> +  /// Allows for disambiguation of the message format.
>> +  ///
>> +  EFI_GUID  MessageGuid;
>> +  ///
>> +  /// Describes the size of MessageData (in bytes) and does not include the size of the header.
>> +  ///
>> +  UINT64    MessageSize;
>> +  ///
>> +  /// Designates an array of bytes that is MessageSize in size.
>> +  ///
>> +  UINT8     MessageData[];
>> +} EFI_MM_COMMUNICATE_HEADER_V3;
>> +
>> +#pragma pack()
>> +
>> +STATIC_ASSERT ((sizeof (EFI_MM_COMMUNICATE_HEADER_V3) == OFFSET_OF (EFI_MM_COMMUNICATE_HEADER_V3,
>> MessageData)), \
>> +  "sizeof (EFI_MM_COMMUNICATE_HEADER_V3) does not align with the beginning of flexible array MessageData");
>> +
>>   typedef enum {
>>     EFI_PCD_TYPE_8,
>>     EFI_PCD_TYPE_16,
>> @@ -208,4 +261,6 @@ EFI_STATUS
>>     IN VOID  *ProcedureArgument
>>   );
>>
>> +extern EFI_GUID   gCommunicateHeaderV3Guid;
>> +
>>   #endif
>> diff --git a/MdePkg/MdePkg.dec b/MdePkg/MdePkg.dec
>> index a28a2daaffa8..411079a4343e 100644
>> --- a/MdePkg/MdePkg.dec
>> +++ b/MdePkg/MdePkg.dec
>> @@ -823,6 +823,11 @@ [Guids]
>>     #
>>     gLinuxEfiInitrdMediaGuid       = {0x5568e427, 0x68fc, 0x4f3d, {0xac, 0x74, 0xca, 0x55, 0x52, 0x31, 0xcc, 0x68}}
>>
>> +  #
>> +  # GUID indicates the MM communication data is compliant with v3 communication header.
>> +  #
>> +  gCommunicateHeaderV3Guid       = { 0x68e8c853, 0x2ba9, 0x4dd7, { 0x9a, 0xc0, 0x91, 0xe1, 0x61, 0x55, 0xc9, 0x35 } }
>> +
>>   [Guids.IA32, Guids.X64]
>>     ## Include/Guid/Cper.h
>>     gEfiIa32X64ErrorTypeCacheCheckGuid = { 0xA55701F5, 0xE3EF, 0x43de, { 0xAC, 0x72, 0x24, 0x9B, 0x57, 0x3F, 0xAD, 0x2C }}
>> --
>> 2.32.0.windows.1
>>
>>
>>
>> 
>>
>