Re: [edk2-devel] [Patch V2 0/3] Move gMpInformationHobGuid from StandaloneMmPkg to UefiCpuPkg.

["duntan" <dun.tan@intel.com>]

I think it's a limitation of the existing implementation. Currently the HobLength in EFI_HOB_GENERIC_HEADER is UINT16.

Thanks,
Dun

-----Original Message-----
From: Ard Biesheuvel <ardb@kernel.org> 
Sent: Wednesday, January 3, 2024 11:11 PM
To: Tan, Dun <dun.tan@intel.com>; Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@arm.com>; Jose Marinho <Jose.Marinho@arm.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>; Ni, Ray <ray.ni@intel.com>; devel@edk2.groups.io
Subject: Re: [edk2-devel] [Patch V2 0/3] Move gMpInformationHobGuid from StandaloneMmPkg to UefiCpuPkg.

(cc Samer and Jose)

Hello Dun Tan,

On Fri, 17 Nov 2023 at 10:57, Tan, Dun <dun.tan@intel.com> wrote:
>
> Hi Ard,
>
> I'm working on moving gMpInformationHobGuid from StandaloneMmPkg to UefiCpuPkg in this patch series. Currently in Edk2, the HOB is only consumed by StandaloneMmCpu.inf.
>
> As we know that this HOB is used to provide a lightweight static information of MP processor. However, there might be a concern that the maximum HOB size 64KB is not large enough when CPU number is 1~2000 or bigger.
>
> May I know if you considered this situation or is there any solution to avoid this issue on Arm?
>

I don't think this has ever come up. Is this maximum HOB size a PI limitation? Or simply a limitation of the existing implementation?





>
> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of duntan
> Sent: Friday, November 17, 2023 5:40 PM
> To: devel@edk2.groups.io
> Subject: [edk2-devel] [Patch V2 0/3] Move gMpInformationHobGuid from StandaloneMmPkg to UefiCpuPkg.
>
> In the V2 patch set: Added more comments in the new MpInformation.h to document that some fields in this HOB may be invalidated.
>
> Move gMpInformationHobGuid from StandaloneMmPkg to UefiCpuPkg.
>
> Previously, the HOB is defined, created and consumed only in StandaloneMmPkg. The HOB contains the number of processors and EFI_PROCESSOR_INFORMATION structure. This is the same as the information that PiSmmCpuDxeSmm uses EfiMpServiceProtocolGuid to get.
>
> The incoming plan is to create gMpInformationHobGuid for both StandaloneMm and legacy DXE_SMM in early phase(for example in CpuMpPei). Then PiSmmCpuDxeSmm can consume the hob, which can simplify code logic in PiSmmCpuDxeSmm driver.
>
> So move this HOB definition to UefiCpuPkg in this patch series.
>
> Dun Tan (3):
>   UefiCpuPkg: Create MpInformation.h in UefiCpuPkg
>   StandaloneMmPkg:Add UefiCpuPkg.dec in DependencyCheck
>   StandaloneMmPkg:Remove MpInformation.h
>
>  StandaloneMmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.inf                       | 1 +
>  StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf | 1 +
>  StandaloneMmPkg/StandaloneMmPkg.ci.yaml                                           | 3 ++-
>  StandaloneMmPkg/StandaloneMmPkg.dec                                               | 1 -
>  {StandaloneMmPkg => UefiCpuPkg}/Include/Guid/MpInformation.h                      | 6 +++++-
>  UefiCpuPkg/UefiCpuPkg.dec                                                         | 3 +++
>  6 files changed, 12 insertions(+), 3 deletions(-)  rename 
> {StandaloneMmPkg => UefiCpuPkg}/Include/Guid/MpInformation.h (71%)
>
> --
> 2.31.1.windows.1
>
>
>
> 
>
>


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