Gerd,
In another mail with title "MdePkg: Remove Itanium leftover data structure",
we are discussing the HOB EFI_SEC_PLATFORM_INFORMATION_RECORD2 that helps
share the BIST information with CpuDxe driver.
That HOB is of format: <UINT32> ( <UINT32> <UINT32> ) +.
Very similar to the format of SMM_BASE_HOB_DATA: <UINT64> <UINT64>+
So, if we use a pattern here to remove the 8K CPU limitation, the same pattern
will
be used by EFI_SEC_PLATFORM_INFORMATION_RECORD2 as well.
How about a new format as below? + Mike and Vincent for comments since the same
pattern may be used for EFI_SEC_PLATFORM_INFORMATION_RECORD3.
#pragma pack(1)
typedef struct {
UINT32 CpuIndex;
UINT32 NumberOfCpus; // align to
EFI_SEC_PLATFORM_INFORMATION_RECORD2.NumberOfCpus
UINT64 SmBase[];
} SMM_BASE_HOB_DATA;
#pragma pack()
For system with less than 8K CPUs, one HOB is produced. CpuIndex is set to 0
indicating
the HOB describes the CPU from 0 to NumberOfCpus-1.
The HOB list may contains multiple such HOB instances each describing the
information for
CPU from CpuIndex to CpuIndex + NumberOfCpus - 1.
The instance order in the HOB list is random so consumer cannot assume the
CpuIndex
of first instance is 0.
Thanks,
Ray
> -----Original Message-----
> From: Gerd Hoffmann <kra...@redhat.com>
> Sent: Wednesday, January 18, 2023 7:19 PM
> To: Wu, Jiaxin <jiaxin...@intel.com>
> Cc: devel@edk2.groups.io; Dong, Eric <eric.d...@intel.com>; Ni, Ray
> <ray...@intel.com>; Zeng, Star <star.z...@intel.com>; Laszlo Ersek
> <ler...@redhat.com>; Kumar, Rahul R <rahul.r.ku...@intel.com>
> Subject: Re: [PATCH v3 1/5] UefiCpuPkg/SmmBaseHob.h: Add SMM Base HOB
> Data
>
> Hi,
>
> > +#pragma pack(1)
> > +typedef struct {
> > + ///
> > + /// Describes the Number of all max supported processors.
> > + ///
> > + UINT64 NumberOfProcessors;
> > + ///
> > + /// Pointer to SmBase address for each Processors.
> > + ///
> > + UINT64 SmBase[];
> > +} SMM_BASE_HOB_DATA;
> > +#pragma pack()
>
> HOBs are limited to 64k in size. So this can by design support at most
> 8191 processors. Adding such a interface to edk2 doesn't look like a
> good idea to me. It probably is not that far off that we'll hit that
> limit given that high-end systems with 1024+ processors exist today.
>
> take care,
> Gerd
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