Re: [PATCH V2 04/10] OvmfPkg/IntelTdx: Implement other helper functions in SecTdxHelperLib

["Gerd Hoffmann" <kraxel@redhat.com>]

> > > [Jiewen] No. We cannot move to MdePkg.
> > > TCG defines the field to be variable length. Something like below:
> > >
> > > typedef struct {
> > >   UINT8                      TableDescriptionSize;
> > >   UINT8                      TableDescription[TableDescriptionSize];
> > >   UINT64                     NumberOfTables;
> > >   EFI_CONFIGURATION_TABLE    TableEntry[NumberOfTables];
> > > } HANDOFF_TABLE_POINTERS2;
> > >
> > > typedef struct {
> > >   UINT8                   BlobDescriptionSize;
> > >   UINT8                   BlobDescription[BlobDescriptionSize];
> > >   EFI_PHYSICAL_ADDRESS    BlobBase;
> > >   UINT64                  BlobLength;
> > > } HANDOFF_TABLE_POINTERS2;
> > >
> > > The implementation can choose its own length as they wish.
> > 
> > Why doesn't follow TDX standard TCG practices here?
> > 
> As Jiewen mentioned TCG defines the field to be variable length. The implementation can choose its own length. Below are some examples.
> Tcg2Pei defines its FV_HANDOFF_TABLE_POINTERS2. (https://github.com/tianocore/edk2/blob/master/SecurityPkg/Tcg/Tcg2Pei/Tcg2Pei.c#L126-L136)
> SmbiosMeasurementDxe defines its SMBIOS_HANDOFF_TABLE_POINTERS2 (https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Universal/SmbiosMeasurementDxe/SmbiosMeasurementDxe.c#L113-L123)
> TcgEventLogRecordLib defines the PLATFORM_FIRMWARE_BLOB2_STRUCT and HANDOFF_TABLE_POINTERS2_STRUCT. https://github.com/tianocore/edk2/blob/master/SecurityPkg/Include/Library/TcgEventLogRecordLib.h#L14-L32

> I think TDX follow the same practice above to define its own
> TDX_HANDOFF_TABLE_POINTERS2 and FV_HANDOFF_TABLE_POINTERS2.
> (FV_HANDOFF_TABLE_POINTERS2 happens to be same as the one in Tcg2Pei.)

Ok, that makes sense.  The TdHob is tdx-specific, measuring a firmware
volume is not.  I'm still wondering why the structs for standard events
(like the firmware volume) are not in some shared header file ...

take care,
  Gerd