Re: [Patch V2 6/6] UefiCpuPkg: Enhance MpHandOff Handling.

["Ni, Ray" <ray.ni@intel.com>]

Yuanhao,
I suggest we "attack" this "large number of processors" problem in a separate patch series.
There are several things that need to consider:
* Calculate maximum number of processor info within one MP_HAND_OFF hob
* Consumer code should not assume there is only one MP_HAND_OFF hob
* Consumer code should not assume the MP_HAND_OFF hobs are ordered by MP_HAND_OFF.ProcessorIndex
* Consumer code should report error if there is gap (some processors are not covered by any MP_HAND_OFF hob)
* Consumer code should consider to cache the MP_HAND_OFF hobs for performance (iterate the hob list as less as possible)

For this patch series, you could add code to cover following:
* producer code asserts that the total cpu count can be described by one MP_HAND_OFF hob
* consumer code asserts that there is only one MP_HAND_OFF hob instance and this one's ProcessorIndex is 0.



Thanks,
Ray

> -----Original Message-----
> From: Xie, Yuanhao <yuanhao.xie@intel.com>
> Sent: Sunday, June 25, 2023 10:39 PM
> To: devel@edk2.groups.io
> Cc: Gerd Hoffmann <kraxel@redhat.com>; Dong, Eric <eric.dong@intel.com>; Ni,
> Ray <ray.ni@intel.com>; Kumar, Rahul R <rahul.r.kumar@intel.com>; Tom
> Lendacky <thomas.lendacky@amd.com>; Xie, Yuanhao
> <yuanhao.xie@intel.com>
> Subject: [Patch V2 6/6] UefiCpuPkg: Enhance MpHandOff Handling.
> 
> Enhance MpHandOff Handling for Systems with a Large Number of
> Processors.
> 
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Yuanhao Xie <yuanhao.xie@intel.com>
> ---
>  UefiCpuPkg/Library/MpInitLib/MpLib.c    | 128
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> +++------------------------------------------------------------
>  UefiCpuPkg/Library/MpInitLib/MpLib.h    |  22 +++++++++-------------
>  UefiCpuPkg/Library/MpInitLib/PeiMpLib.c |  56
> +++++++++++++++++++++++++++++++++++++++-----------------
>  3 files changed, 116 insertions(+), 90 deletions(-)
> 
> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c
> b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> index 391e6f19ef..087bf3ea92 100644
> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> @@ -1528,32 +1528,48 @@ SwitchContextPerAp (
>    This procedure allows the AP to switch to another section of
>    memory and continue its loop there.
> 
> -  @param[in] MpHandOff  Pointer to MP hand-off data structure.
> +  @param[in] BspNumber  Bsp Number
>  **/
>  VOID
>  SwitchApContext (
> -  IN MP_HAND_OFF  *MpHandOff
> +  IN UINT32  BspNumber
>    )
>  {
> -  UINTN   Index;
> -  UINT32  BspNumber;
> -
> -  BspNumber = GetBspNumber (MpHandOff);
> +  UINTN        Index;
> +  UINTN        LimitationOfMpHandOffHob;
> +  UINTN        NumberOfProcessorsInCurrentHob;
> +  UINTN        CpuCountInCurrentHob;
> +  MP_HAND_OFF  *MpHandOff;
> +  BOOLEAN      BspFound;
> +
> +  BspFound = FALSE;
> +
> +  MpHandOff                = GetMpHandOffHob ();
> +  CpuCountInCurrentHob     = 0;
> +  LimitationOfMpHandOffHob = (0xFFF8 - sizeof (EFI_HOB_GUID_TYPE) - sizeof
> (MP_HAND_OFF)) / sizeof (PROCESSOR_HAND_OFF);
> +  while (CpuCountInCurrentHob < MpHandOff->CpuCount) {
> +    //
> +    // Get the processor number for the BSP
> +    //
> +    NumberOfProcessorsInCurrentHob = MIN (MpHandOff->CpuCount -
> CpuCountInCurrentHob, LimitationOfMpHandOffHob);
> 
> -  for (Index = 0; Index < MpHandOff->CpuCount; Index++) {
> -    if (Index != BspNumber) {
> -      *(UINTN *)(UINTN)MpHandOff->Info[Index].StartupProcedureAddress =
> (UINTN)SwitchContextPerAp;
> -      *(UINT32 *)(UINTN)MpHandOff->Info[Index].StartupSignalAddress   =
> MpHandOff->StartupSignalValue;
> +    for (Index = 0; Index < NumberOfProcessorsInCurrentHob; Index++) {
> +      if ((Index == BspNumber) && (BspFound == FALSE)) {
> +        BspFound = TRUE;
> +      } else {
> +        *(UINTN *)(UINTN)MpHandOff->Info[Index].StartupProcedureAddress =
> (UINTN)SwitchContextPerAp;
> +        *(UINT32 *)(UINTN)MpHandOff->Info[Index].StartupSignalAddress   =
> MpHandOff->StartupSignalValue;
> +        WaitApWakeup ((UINT32 *)(UINTN)(MpHandOff-
> >Info[Index].StartupSignalAddress));
> +      }
>      }
> -  }
> 
> -  //
> -  // Wait all APs waken up if this is not the 1st broadcast of SIPI
> -  //
> -  for (Index = 0; Index < MpHandOff->CpuCount; Index++) {
> -    if (Index != BspNumber) {
> -      WaitApWakeup ((UINT32 *)(UINTN)(MpHandOff-
> >Info[Index].StartupSignalAddress));
> +    if (CpuCountInCurrentHob + NumberOfProcessorsInCurrentHob >=
> MpHandOff->CpuCount) {
> +      break;
>      }
> +
> +    MpHandOff = (MP_HAND_OFF *)((UINT8 *)MpHandOff + sizeof
> (MP_HAND_OFF) + sizeof (EFI_HOB_GUID_TYPE) + sizeof
> (PROCESSOR_HAND_OFF) * NumberOfProcessorsInCurrentHob);
> +
> +    CpuCountInCurrentHob += NumberOfProcessorsInCurrentHob;
>    }
>  }
> 
> @@ -1909,37 +1925,6 @@ CheckAllAPs (
>    return EFI_NOT_READY;
>  }
> 
> -/**
> -  This function Get BspNumber.
> -
> -  @param[in] MpHandOff        Pointer to MpHandOff
> -  @return                     BspNumber
> -**/
> -UINT32
> -GetBspNumber (
> -  IN CONST MP_HAND_OFF  *MpHandOff
> -  )
> -{
> -  UINT32  ApicId;
> -  UINT32  BspNumber;
> -  UINT32  Index;
> -
> -  //
> -  // Get the processor number for the BSP
> -  //
> -  BspNumber = MAX_UINT32;
> -  ApicId    = GetInitialApicId ();
> -  for (Index = 0; Index < MpHandOff->CpuCount; Index++) {
> -    if (MpHandOff->Info[Index].ApicId == ApicId) {
> -      BspNumber = Index;
> -    }
> -  }
> -
> -  ASSERT (BspNumber != MAX_UINT32);
> -
> -  return BspNumber;
> -}
> -
>  /**
>    Get pointer to CPU MP Data structure from GUIDed HOB.
> 
> @@ -1994,8 +1979,13 @@ MpInitLibInitialize (
>    UINTN                    ApResetVectorSizeAbove1Mb;
>    UINTN                    BackupBufferAddr;
>    UINTN                    ApIdtBase;
> +  UINTN                    LimitationOfMpHandOffHob;
> +  UINTN                    NumberOfProcessorsInCurrentHob;
> +  UINTN                    ProcessedCpuCount;
> +  UINTN                    CurrentProcessorIndex;
> 
>    MpHandOff = GetMpHandOffHob ();
> +
>    if (MpHandOff == NULL) {
>      MaxLogicalProcessorNumber = PcdGet32
> (PcdCpuMaxLogicalProcessorNumber);
>    } else {
> @@ -2156,17 +2146,35 @@ MpInitLibInitialize (
>      // from HOB
>      //
>      AmdSevUpdateCpuMpData (CpuMpData);
> -    CpuMpData->CpuCount  = MpHandOff->CpuCount;
> -    CpuMpData->BspNumber = GetBspNumber (MpHandOff);
> -    CpuInfoInHob         = (CPU_INFO_IN_HOB *)(UINTN)CpuMpData-
> >CpuInfoInHob;
> -    for (Index = 0; Index < CpuMpData->CpuCount; Index++) {
> -      InitializeSpinLock (&CpuMpData->CpuData[Index].ApLock);
> -      CpuMpData->CpuData[Index].CpuHealthy = (MpHandOff->Info[Index].Health
> == 0) ? TRUE : FALSE;
> -      CpuMpData->CpuData[Index].ApFunction = 0;
> -      CpuInfoInHob[Index].InitialApicId    = MpHandOff->Info[Index].ApicId;
> -      CpuInfoInHob[Index].ApTopOfStack     = CpuMpData->Buffer + (Index + 1) *
> CpuMpData->CpuApStackSize;
> -      CpuInfoInHob[Index].ApicId           = MpHandOff->Info[Index].ApicId;
> -      CpuInfoInHob[Index].Health           = MpHandOff->Info[Index].Health;
> +    CpuMpData->CpuCount = MpHandOff->CpuCount;
> +    CpuInfoInHob        = (CPU_INFO_IN_HOB *)(UINTN)CpuMpData-
> >CpuInfoInHob;
> +
> +    LimitationOfMpHandOffHob = (0xFFF8 - sizeof (EFI_HOB_GUID_TYPE) - sizeof
> (MP_HAND_OFF)) / sizeof (PROCESSOR_HAND_OFF);
> +    ProcessedCpuCount        = 0;
> +    while (ProcessedCpuCount < MpHandOff->CpuCount) {
> +      NumberOfProcessorsInCurrentHob = MIN (MpHandOff->CpuCount -
> ProcessedCpuCount, LimitationOfMpHandOffHob);
> +
> +      for (Index = 0; Index < NumberOfProcessorsInCurrentHob; Index++) {
> +        CurrentProcessorIndex = Index+MpHandOff->ProcessorIndex;
> +        if (MpHandOff->Info[Index].ApicId == GetInitialApicId ()) {
> +          CpuMpData->BspNumber = (UINT32)Index;
> +        }
> +
> +        InitializeSpinLock (&CpuMpData-
> >CpuData[CurrentProcessorIndex].ApLock);
> +        CpuMpData->CpuData[CurrentProcessorIndex].CpuHealthy = (MpHandOff-
> >Info[Index].Health == 0) ? TRUE : FALSE;
> +        CpuMpData->CpuData[CurrentProcessorIndex].ApFunction = 0;
> +        CpuInfoInHob[CurrentProcessorIndex].InitialApicId    = MpHandOff-
> >Info[Index].ApicId;
> +        CpuInfoInHob[CurrentProcessorIndex].ApTopOfStack     = CpuMpData-
> >Buffer + (Index + 1) * CpuMpData->CpuApStackSize;
> +        CpuInfoInHob[CurrentProcessorIndex].ApicId           = MpHandOff-
> >Info[Index].ApicId;
> +        CpuInfoInHob[CurrentProcessorIndex].Health           = MpHandOff-
> >Info[Index].Health;
> +      }
> +
> +      if (ProcessedCpuCount+NumberOfProcessorsInCurrentHob >= MpHandOff-
> >CpuCount) {
> +        break;
> +      }
> +
> +      MpHandOff          = (MP_HAND_OFF *)((UINT8 *)MpHandOff + sizeof
> (MP_HAND_OFF) + sizeof (EFI_HOB_GUID_TYPE) + sizeof
> (PROCESSOR_HAND_OFF) * NumberOfProcessorsInCurrentHob);
> +      ProcessedCpuCount += NumberOfProcessorsInCurrentHob;
>      }
> 
>      DEBUG ((DEBUG_INFO, "MpHandOff->WaitLoopExecutionMode: %04d, sizeof
> (VOID *): %04d\n", MpHandOff->WaitLoopExecutionMode, sizeof (VOID *)));
> @@ -2183,7 +2191,7 @@ MpInitLibInitialize (
>        CpuMpData->FinishedCount = 0;
>        CpuMpData->InitFlag      = ApInitDone;
>        SaveCpuMpData (CpuMpData);
> -      SwitchApContext (MpHandOff);
> +      SwitchApContext (CpuMpData->BspNumber);
>        ASSERT (CpuMpData->FinishedCount == (CpuMpData->CpuCount - 1));
> 
>        //
> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.h
> b/UefiCpuPkg/Library/MpInitLib/MpLib.h
> index 468d3a5925..6af635a80c 100644
> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.h
> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.h
> @@ -497,17 +497,6 @@ SaveCpuMpData (
>    IN CPU_MP_DATA  *CpuMpData
>    );
> 
> -/**
> -  This function Get BspNumber.
> -
> -  @param[in] MpHandOff        Pointer to MpHandOff
> -  @return                     BspNumber
> -**/
> -UINT32
> -GetBspNumber (
> -  IN CONST MP_HAND_OFF  *MpHandOff
> -  );
> -
>  /**
>    Get available system memory below 1MB by specified size.
> 
> @@ -522,12 +511,19 @@ GetWakeupBuffer (
>    );
> 
>  /**
> -  Switch Context for each AP.
> +  This function is intended to be invoked by the BSP in order
> +  to wake up the AP. The BSP accomplishes this by triggering a
> +  start-up signal, which in turn causes any APs that are
> +  currently in a loop on the PEI-prepared memory to awaken and
> +  begin running the procedure called SwitchContextPerAp.
> +  This procedure allows the AP to switch to another section of
> +  memory and continue its loop there.
> 
> +  @param[in] BspNumber  Bsp Number
>  **/
>  VOID
>  SwitchApContext (
> -  IN MP_HAND_OFF  *MpHandOff
> +  IN UINT32  BspNumber
>    );
> 
>  /**
> diff --git a/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c
> b/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c
> index f80e00edcf..18f83d9ed5 100644
> --- a/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c
> @@ -131,31 +131,53 @@ SaveCpuMpData (
>    CPU_INFO_IN_HOB  *CpuInfoInHob;
>    MP_HAND_OFF      *MpHandOff;
>    UINTN            MpHandOffSize;
> +  UINT32           LimitationOfMpHandOffHob;
> +  UINT32           NumberOfProcessorsInCurrentHob;
> +  UINT32           ProcessedCpuCount;
> +  UINTN            CurrentProcessorIndex;
> 
>    //
>    // When APs are in a state that can be waken up by a store operation to a
> memory address,
>    // report the MP_HAND_OFF data for DXE to use.
>    //
> -  CpuInfoInHob  = (CPU_INFO_IN_HOB *)(UINTN)CpuMpData->CpuInfoInHob;
> -  MpHandOffSize = sizeof (MP_HAND_OFF) + sizeof (PROCESSOR_HAND_OFF) *
> CpuMpData->CpuCount;
> -  MpHandOff     = (MP_HAND_OFF *)BuildGuidHob (&mMpHandOffGuid,
> MpHandOffSize);
> -  ASSERT (MpHandOff != NULL);
> -  ZeroMem (MpHandOff, MpHandOffSize);
> -  MpHandOff->ProcessorIndex = 0;
> -
> -  MpHandOff->CpuCount = CpuMpData->CpuCount;
> -  if (CpuMpData->ApLoopMode != ApInHltLoop) {
> -    MpHandOff->StartupSignalValue    = MP_HAND_OFF_SIGNAL;
> -    MpHandOff->WaitLoopExecutionMode = sizeof (VOID *);
> -  }
> +  CpuInfoInHob = (CPU_INFO_IN_HOB *)(UINTN)CpuMpData->CpuInfoInHob;
> +  //
> +  // Maximum number of processor could be saved in the HOB.
> +  //
> +  LimitationOfMpHandOffHob = (0xFFF8 - sizeof (EFI_HOB_GUID_TYPE) - sizeof
> (MP_HAND_OFF)) / sizeof (PROCESSOR_HAND_OFF);
> +  ProcessedCpuCount        = 0;
> +  while (ProcessedCpuCount < CpuMpData->CpuCount) {
> +    NumberOfProcessorsInCurrentHob = MIN ((UINT32)CpuMpData->CpuCount -
> ProcessedCpuCount, LimitationOfMpHandOffHob);
> +    MpHandOffSize                  = sizeof (MP_HAND_OFF) + sizeof
> (PROCESSOR_HAND_OFF) * NumberOfProcessorsInCurrentHob;
> +    MpHandOff                      = (MP_HAND_OFF *)BuildGuidHob (
> +                                                      &mMpHandOffGuid,
> +                                                      MpHandOffSize
> +                                                      );
> +    ASSERT (MpHandOff != NULL);
> +    ZeroMem (MpHandOff, MpHandOffSize);
> +    //
> +    // Each individual processor can be uniquely identified by
> +    // combining the processorIndex with the mMpHandOffGuid.
> +    //
> +    MpHandOff->ProcessorIndex = ProcessedCpuCount;
> +    MpHandOff->CpuCount       = CpuMpData->CpuCount;
> 
> -  for (Index = 0; Index < MpHandOff->CpuCount; Index++) {
> -    MpHandOff->Info[Index].ApicId = CpuInfoInHob[Index].ApicId;
> -    MpHandOff->Info[Index].Health = CpuInfoInHob[Index].Health;
>      if (CpuMpData->ApLoopMode != ApInHltLoop) {
> -      MpHandOff->Info[Index].StartupSignalAddress    =
> (UINT64)(UINTN)CpuMpData->CpuData[Index].StartupApSignal;
> -      MpHandOff->Info[Index].StartupProcedureAddress =
> (UINT64)(UINTN)&CpuMpData->CpuData[Index].ApFunction;
> +      MpHandOff->StartupSignalValue    = MP_HAND_OFF_SIGNAL;
> +      MpHandOff->WaitLoopExecutionMode = sizeof (VOID *);
>      }
> +
> +    for (Index = MpHandOff->ProcessorIndex; Index <
> NumberOfProcessorsInCurrentHob + MpHandOff->ProcessorIndex; Index++) {
> +      CurrentProcessorIndex                         = Index-MpHandOff->ProcessorIndex;
> +      MpHandOff->Info[CurrentProcessorIndex].ApicId =
> CpuInfoInHob[Index].ApicId;
> +      MpHandOff->Info[CurrentProcessorIndex].Health =
> CpuInfoInHob[Index].Health;
> +      if (CpuMpData->ApLoopMode != ApInHltLoop) {
> +        MpHandOff->Info[CurrentProcessorIndex].StartupSignalAddress    =
> (UINT64)(UINTN)CpuMpData->CpuData[Index].StartupApSignal;
> +        MpHandOff->Info[CurrentProcessorIndex].StartupProcedureAddress =
> (UINT64)(UINTN)&CpuMpData->CpuData[Index].ApFunction;
> +      }
> +    }
> +
> +    ProcessedCpuCount += LimitationOfMpHandOffHob;
>    }
> 
>    //
> --
> 2.36.1.windows.1