Re: [edk2-devel] [PATCH v1 1/2] UefiCpuPkg: Extend SMM CPU Service with rendezvous support.

["Marvin Häuser" <mhaeuser@posteo.de>]

Hey all,

On 10.02.22 09:18, Siyuan, Fu wrote:
> Hi, Mike
>
>> -----Original Message-----
>> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Michael D
>> Kinney
>> Sent: 2022年2月9日 0:31
>> To: devel@edk2.groups.io; Li, Zhihao <zhihao.li@intel.com>; Kinney, Michael D
>> <michael.d.kinney@intel.com>
>> Cc: Dong, Eric <eric.dong@intel.com>; Ni, Ray <ray.ni@intel.com>; Kumar,
>> Rahul1 <rahul1.kumar@intel.com>
>> Subject: Re: [edk2-devel] [PATCH v1 1/2] UefiCpuPkg: Extend SMM CPU Service
>> with rendezvous support.
>>
>> Hi Zhihao,
>>
>> gEfiSmmCpuServiceProtocolGuid is defined in the UefiCpuPkg and is already an
>> EDK II specific feature protocol.  Adding an Edkii names version of the
>> protocol does not make it clear that there is a relationship between the
>> two versions of this protocol.  You have added one new service to the
>> existing protocol.  The existing protocol does not have a Revision field
>> so we do have to create a new Protocol Name/Protocol GUID.  Based on
>> previous use cases, we have a few options:
>>
>> 1) If Revision field is present, add to end and increase Revision value
>> 2) If Revision field not present
>>    a) Define an _2 or _Ex version of the protocol with new service(s) added
>>       to end of structure and implement original version of the protocol on
>>       top of the _2 version of the protocol.
>>    b) Define a new Protocol with just the new services. (e.g.
>> gEdkiiSmmCpuRedezvousProtocolGuid)
> We previously discussed with Ray when deciding the protocol name and choose
> the edk2 prefix.
> @Ni, Ray
> Any opinion on using an _Ex version protocol name or a separate protocol?

I would strongly suggest to drop the "Ex" naming scheme entirely in the 
future for the simple reason of incrementing further. Some protocols 
already reached major version 3, and it would be awkward to have 
something like "ExExProtocol".

Best regards,
Marvin

>
>> The patch also changes the DEC default value of
>> gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode
>> from 0x00 to 0x01.  Changing the default value of a PCD in a DEC file is a non
>> backwards compatible change.  This should not be done.  Instead, platforms that
>> need
>> the different sync mode should set that PCD in their DSC file.
>>
>> Is a new lib class really required at this time.  The reason to add a new lib
>> class is if there are multiple consumers.
> There are lots of consumers but no in edk2 repo, mostly inside platform code like edk2platforms.
> Technically the SMI handler which require all processors in SMM mode to complete its task (either
> due to security consideration or hardware/silicon restriction) will need to consume this library
> interface to complete the rendezvous in relax AP mode.
>
>> I see the lib instance uses a RegisterProtocolNotify in its constructor.  Is it
>> possible to use a Depex instead and eliminate the additional complexity of a
>> constructor and RegisterProtocolNotify?
> We can't use Depex since this is an optional protocol. It's not required to those platforms
> which only have traditional sync mode support.
>
> Thanks,
> Siyuan
>
>> Best regards,
>>
>> Mike
>>
>>> -----Original Message-----
>>> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Li, Zhihao
>>> Sent: Monday, February 7, 2022 9:36 PM
>>> To: devel@edk2.groups.io
>>> Cc: Dong, Eric <eric.dong@intel.com>; Ni, Ray <ray.ni@intel.com>; Kumar,
>> Rahul1 <rahul1.kumar@intel.com>
>>> Subject: [edk2-devel] [PATCH v1 1/2] UefiCpuPkg: Extend SMM CPU Service
>> with rendezvous support.
>>> From: Zhihao Li <zhihao.li@intel.com>
>>>
>>> REF： https://bugzilla.tianocore.org/show_bug.cgi?id=3815
>>>
>>> This patch extends the SMM CPU Service protocol with new interface
>>> SmmWaitForAllProcessor(), which can be used by SMI handler to optionally
>>> wait for other APs to complete SMM rendezvous in relaxed AP mode.
>>>
>>> A new library SmmCpuRendezvousLib is provided to abstract the service
>>> into library API to simple SMI handler code.
>>>
>>> Cc: Eric Dong <eric.dong@intel.com>
>>> Cc: Ray Ni <ray.ni@intel.com>
>>> Cc: Rahul Kumar <rahul1.kumar@intel.com>
>>>
>>> Signed-off-by: Zhihao Li <zhihao.li@intel.com>
>>> ---
>>>   UefiCpuPkg/Library/SmmCpuRendezvousLib/SmmCpuRendezvousLib.c   | 109
>> ++++++++++++++++++++
>>>   UefiCpuPkg/PiSmmCpuDxeSmm/CpuService.c                         |  65
>> ++++++++++++
>>>   UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c                          |  14 ++-
>>>   UefiCpuPkg/PiSmmCpuDxeSmm/SyncTimer.c                          |   2 +-
>>>   UefiCpuPkg/Include/Library/SmmCpuRendezvousLib.h               |  27 +++++
>>>   UefiCpuPkg/Include/Protocol/SmmCpuService.h                    |  40 +++++++
>>>   UefiCpuPkg/Library/SmmCpuRendezvousLib/SmmCpuRendezvousLib.inf |  32
>> ++++++
>>>   UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h                     |  28 +++++
>>>   UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf                   |   3 +-
>>>   UefiCpuPkg/UefiCpuPkg.dec                                      |   5 +-
>>>   10 files changed, 318 insertions(+), 7 deletions(-)
>>>
>>> diff --git
>> a/UefiCpuPkg/Library/SmmCpuRendezvousLib/SmmCpuRendezvousLib.c
>>> b/UefiCpuPkg/Library/SmmCpuRendezvousLib/SmmCpuRendezvousLib.c
>>> new file mode 100644
>>> index 0000000000..3c5cd51d0c
>>> --- /dev/null
>>> +++ b/UefiCpuPkg/Library/SmmCpuRendezvousLib/SmmCpuRendezvousLib.c
>>> @@ -0,0 +1,109 @@
>>> +/** @file
>>>
>>> +SMM CPU Rendezvous library header file.
>>>
>>> +
>>>
>>> +Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>
>>>
>>> +SPDX-License-Identifier: BSD-2-Clause-Patent
>>>
>>> +
>>>
>>> +**/
>>>
>>> +
>>>
>>> +
>>>
>>> +#include <Base.h>
>>>
>>> +#include <Uefi.h>
>>>
>>> +#include <Library/BaseLib.h>
>>>
>>> +#include <Library/DebugLib.h>
>>>
>>> +#include <Library/PcdLib.h>
>>>
>>> +#include <Library/SmmServicesTableLib.h>
>>>
>>> +#include <Protocol/SmmCpuService.h>
>>>
>>> +#include <Library/SmmCpuRendezvousLib.h>
>>>
>>> +
>>>
>>> +STATIC EDKII_SMM_CPU_SERVICE_PROTOCOL  *mSmmCpuService = NULL;
>>>
>>> +
>>>
>>> +/**
>>>
>>> +  This routine wait for all AP processors to arrive in SMM.
>>>
>>> +
>>>
>>> +  @param  BlockingMode  Blocking mode or non-blocking mode.
>>>
>>> +
>>>
>>> +  @retval TRUE   All processors checked in to SMM
>>>
>>> +  @retval FALSE  Some processor not checked in to SMM
>>>
>>> +
>>>
>>> +**/
>>>
>>> +EFI_STATUS
>>>
>>> +EFIAPI
>>>
>>> +SmmWaitForAllProcessor (
>>>
>>> +  IN  BOOLEAN  BlockingMode
>>>
>>> +  )
>>>
>>> +{
>>>
>>> +  EFI_STATUS Status;
>>>
>>> +
>>>
>>> +  if (mSmmCpuService == NULL) {
>>>
>>> +    return TRUE;
>>>
>>> +  }
>>>
>>> +
>>>
>>> +  Status = mSmmCpuService->WaitForAllProcessor (
>>>
>>> +              mSmmCpuService,
>>>
>>> +              BlockingMode
>>>
>>> +              );
>>>
>>> +  return EFI_ERROR(Status) ? FALSE : TRUE;
>>>
>>> +}
>>>
>>> +
>>>
>>> +/**
>>>
>>> +  Register status code callback function only when Report Status Code
>> protocol
>>> +  is installed.
>>>
>>> +
>>>
>>> +  @param Protocol       Points to the protocol's unique identifier.
>>>
>>> +  @param Interface      Points to the interface instance.
>>>
>>> +  @param Handle         The handle on which the interface was installed.
>>>
>>> +
>>>
>>> +  @retval EFI_SUCCESS   Notification runs successfully.
>>>
>>> +
>>>
>>> +**/
>>>
>>> +EFI_STATUS
>>>
>>> +EFIAPI
>>>
>>> +SmmCpuServiceProtocolNotify (
>>>
>>> +  IN CONST EFI_GUID        *Protocol,
>>>
>>> +  IN VOID                  *Interface,
>>>
>>> +  IN EFI_HANDLE            Handle
>>>
>>> +  )
>>>
>>> +{
>>>
>>> +  EFI_STATUS                   Status;
>>>
>>> +
>>>
>>> +  Status = gSmst->SmmLocateProtocol (
>>>
>>> +                    &gEdkiiSmmCpuServiceProtocolGuid,
>>>
>>> +                    NULL,
>>>
>>> +                    (VOID **) &mSmmCpuService
>>>
>>> +                    );
>>>
>>> +  ASSERT_EFI_ERROR (Status);
>>>
>>> +
>>>
>>> +  return EFI_SUCCESS;
>>>
>>> +}
>>>
>>> +
>>>
>>> +/**
>>>
>>> +  The constructor function
>>>
>>> +
>>>
>>> +  @param[in]  ImageHandle  The firmware allocated handle for the EFI image.
>>>
>>> +  @param[in]  SystemTable  A pointer to the EFI System Table.
>>>
>>> +
>>>
>>> +  @retval EFI_SUCCESS      The constructor always returns EFI_SUCCESS.
>>>
>>> +
>>>
>>> +**/
>>>
>>> +EFI_STATUS
>>>
>>> +EFIAPI
>>>
>>> +SmmCpuRendezvousLibConstructor (
>>>
>>> +  IN EFI_HANDLE        ImageHandle,
>>>
>>> +  IN EFI_SYSTEM_TABLE  *SystemTable
>>>
>>> +  )
>>>
>>> +{
>>>
>>> +  EFI_STATUS  Status;
>>>
>>> +  VOID        *Registration;
>>>
>>> +
>>>
>>> +  Status = gSmst->SmmLocateProtocol (&gEdkiiSmmCpuServiceProtocolGuid,
>> NULL, (VOID **) &mSmmCpuService);
>>> +  if (EFI_ERROR (Status)) {
>>>
>>> +    Status = gSmst->SmmRegisterProtocolNotify (
>>>
>>> +                &gEdkiiSmmCpuServiceProtocolGuid,
>>>
>>> +                SmmCpuServiceProtocolNotify,
>>>
>>> +                &Registration
>>>
>>> +                );
>>>
>>> +    ASSERT_EFI_ERROR (Status);
>>>
>>> +  }
>>>
>>> +  return EFI_SUCCESS;
>>>
>>> +}
>>> \ No newline at end of file
>>> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuService.c
>> b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuService.c
>>> index 5d624f8e9e..34019c24ff 100644
>>> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuService.c
>>> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuService.c
>>> @@ -20,6 +20,19 @@ EFI_SMM_CPU_SERVICE_PROTOCOL
>> mSmmCpuService = {
>>>     SmmRegisterExceptionHandler
>>>
>>>   };
>>>
>>>
>>>
>>> +//
>>>
>>> +// EDKII SMM CPU Service Protocol instance
>>>
>>> +//
>>>
>>> +EDKII_SMM_CPU_SERVICE_PROTOCOL  mEdkiiSmmCpuService = {
>>>
>>> +  SmmGetProcessorInfo,
>>>
>>> +  SmmSwitchBsp,
>>>
>>> +  SmmAddProcessor,
>>>
>>> +  SmmRemoveProcessor,
>>>
>>> +  SmmWhoAmI,
>>>
>>> +  SmmRegisterExceptionHandler,
>>>
>>> +  SmmWaitForAllProcessor
>>>
>>> +};
>>>
>>> +
>>>
>>>   /**
>>>
>>>     Gets processor information on the requested processor at the instant this
>> call is made.
>>>
>>>
>>> @@ -365,5 +378,57 @@ InitializeSmmCpuServices (
>>>                       &mSmmCpuService
>>>
>>>                       );
>>>
>>>     ASSERT_EFI_ERROR (Status);
>>>
>>> +
>>>
>>> +  Status = gSmst->SmmInstallProtocolInterface (
>>>
>>> +                    &Handle,
>>>
>>> +                    &gEdkiiSmmCpuServiceProtocolGuid,
>>>
>>> +                    EFI_NATIVE_INTERFACE,
>>>
>>> +                    &mEdkiiSmmCpuService
>>>
>>> +                    );
>>>
>>> +  ASSERT_EFI_ERROR (Status);
>>>
>>> +  return Status;
>>>
>>> +}
>>>
>>> +
>>>
>>> +/**
>>>
>>> +  Wait for all processors enterring SMM until all CPUs are already
>> synchronized or not.
>>> +
>>>
>>> +  @param  This                   A pointer to the
>> EDKII_SMM_CPU_SERVICE_PROTOCOL instance.
>>> +  @param  BlockingMode           Blocking mode or non-blocking mode.
>>>
>>> +
>>>
>>> +  @retval EFI_SUCCESS    All avaiable APs arrived.
>>>
>>> +  @retval EFI_TIMEOUT    Wait for all APs until timeout.
>>>
>>> +**/
>>>
>>> +EFI_STATUS
>>>
>>> +EFIAPI
>>>
>>> +SmmWaitForAllProcessor (
>>>
>>> +  IN  EDKII_SMM_CPU_SERVICE_PROTOCOL  *This,
>>>
>>> +  IN  BOOLEAN                          BlockingMode
>>>
>>> +  )
>>>
>>> +{
>>>
>>> +  EFI_STATUS                Status;
>>>
>>> +
>>>
>>> +  //
>>>
>>> +  // Return success immediately if all CPUs are already synchronized.
>>>
>>> +  //
>>>
>>> +  if (mSmmMpSyncData->AllApArrivedWithException) {
>>>
>>> +    Status = EFI_SUCCESS;
>>>
>>> +    goto ON_EXIT;
>>>
>>> +  }
>>>
>>> +
>>>
>>> +  if (!BlockingMode) {
>>>
>>> +    Status = EFI_TIMEOUT;
>>>
>>> +    goto ON_EXIT;
>>>
>>> +  }
>>>
>>> +
>>>
>>> +  //
>>>
>>> +  // There are some APs outside SMM, Wait for all avaiable APs to arrive.
>>>
>>> +  //
>>>
>>> +  SmmWaitForApArrival (BlockingMode);
>>>
>>> +  Status = mSmmMpSyncData->AllApArrivedWithException ? EFI_SUCCESS :
>> EFI_TIMEOUT;
>>> +
>>>
>>> +ON_EXIT:
>>>
>>> +  if (!mSmmMpSyncData->AllApArrivedWithException){
>>>
>>> +    DEBUG ((EFI_D_INFO, "EdkiiSmmWaitForAllApArrival: Timeout to wait all
>> APs arrival\n"));
>>> +  }
>>>
>>>     return Status;
>>>
>>>   }
>>>
>>> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
>> b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
>>> index 882dee4fe2..9c7b16728a 100644
>>> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
>>> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
>>> @@ -261,7 +261,7 @@ IsLmceSignaled (
>>>   **/
>>>
>>>   VOID
>>>
>>>   SmmWaitForApArrival (
>>>
>>> -  VOID
>>>
>>> +  IN  BOOLEAN  BlockingMode
>>>
>>>     )
>>>
>>>   {
>>>
>>>     UINT64   Timer;
>>>
>>> @@ -270,7 +270,14 @@ SmmWaitForApArrival (
>>>     BOOLEAN  LmceSignal;
>>>
>>>
>>>
>>>     ASSERT (*mSmmMpSyncData->Counter <= mNumberOfCpus);
>>>
>>> -
>>>
>>> +
>>>
>>> +  //
>>>
>>> +  // if block is False, do not wait and return immediately.
>>>
>>> +  //
>>>
>>> +  if (!BlockingMode){
>>>
>>> +    return;
>>>
>>> +  }
>>>
>>> +
>>>
>>>     LmceEn     = FALSE;
>>>
>>>     LmceSignal = FALSE;
>>>
>>>     if (mMachineCheckSupported) {
>>>
>>> @@ -511,7 +518,7 @@ BSPHandler (
>>>       //
>>>
>>>       // Wait for APs to arrive
>>>
>>>       //
>>>
>>> -    SmmWaitForApArrival ();
>>>
>>> +    SmmWaitForApArrival(TRUE);
>>>
>>>
>>>
>>>       //
>>>
>>>       // Lock the counter down and retrieve the number of APs
>>>
>>> @@ -1886,6 +1893,7 @@ InitializeMpSyncData (
>>>       *mSmmMpSyncData->Counter       = 0;
>>>
>>>       *mSmmMpSyncData->InsideSmm     = FALSE;
>>>
>>>       *mSmmMpSyncData->AllCpusInSync = FALSE;
>>>
>>> +    mSmmMpSyncData->AllApArrivedWithException = FALSE;
>>>
>>>
>>>
>>>       for (CpuIndex = 0; CpuIndex < gSmmCpuPrivate-
>>> SmmCoreEntryContext.NumberOfCpus; CpuIndex++) {
>>>
>>>         mSmmMpSyncData->CpuData[CpuIndex].Busy =
>>>
>>> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/SyncTimer.c
>> b/UefiCpuPkg/PiSmmCpuDxeSmm/SyncTimer.c
>>> index 0c070c5736..844263f889 100644
>>> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/SyncTimer.c
>>> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/SyncTimer.c
>>> @@ -8,7 +8,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
>>>
>>>
>>>   #include "PiSmmCpuDxeSmm.h"
>>>
>>>
>>>
>>> -UINT64  mTimeoutTicker = 0;
>>>
>>> +UINT64   mTimeoutTicker = 0;
>>>
>>>   //
>>>
>>>   //  Number of counts in a roll-over cycle of the performance counter.
>>>
>>>   //
>>>
>>> diff --git a/UefiCpuPkg/Include/Library/SmmCpuRendezvousLib.h
>> b/UefiCpuPkg/Include/Library/SmmCpuRendezvousLib.h
>>> new file mode 100644
>>> index 0000000000..f245c3a1c9
>>> --- /dev/null
>>> +++ b/UefiCpuPkg/Include/Library/SmmCpuRendezvousLib.h
>>> @@ -0,0 +1,27 @@
>>> +/** @file
>>>
>>> +SMM CPU Rendezvous library header file.
>>>
>>> +
>>>
>>> +Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>
>>>
>>> +SPDX-License-Identifier: BSD-2-Clause-Patent
>>>
>>> +
>>>
>>> +**/
>>>
>>> +
>>>
>>> +#ifndef _SMM_CPU_RENDEZVOUS_H_
>>>
>>> +#define _SMM_CPU_RENDEZVOUS_H_
>>>
>>> +
>>>
>>> +/**
>>>
>>> +  This routine wait for all AP processors to arrive in SMM.
>>>
>>> +
>>>
>>> +  @param  BlockingMode  Blocking mode or non-blocking mode.
>>>
>>> +
>>>
>>> +  @retval TRUE   All processors checked in to SMM
>>>
>>> +  @retval FALSE  Some processor not checked in to SMM
>>>
>>> +
>>>
>>> +**/
>>>
>>> +EFI_STATUS
>>>
>>> +EFIAPI
>>>
>>> +SmmWaitForAllProcessor (
>>>
>>> +  IN  BOOLEAN BlockingMode
>>>
>>> +  );
>>>
>>> +
>>>
>>> +#endif
>>>
>>> diff --git a/UefiCpuPkg/Include/Protocol/SmmCpuService.h
>> b/UefiCpuPkg/Include/Protocol/SmmCpuService.h
>>> index 952767afce..0ace5356a9 100644
>>> --- a/UefiCpuPkg/Include/Protocol/SmmCpuService.h
>>> +++ b/UefiCpuPkg/Include/Protocol/SmmCpuService.h
>>> @@ -200,4 +200,44 @@ struct _EFI_SMM_CPU_SERVICE_PROTOCOL {
>>>
>>>
>>>   extern EFI_GUID  gEfiSmmCpuServiceProtocolGuid;
>>>
>>>
>>>
>>> +//
>>>
>>> +//  EDKII_SMM_CPU_SERVICE_PROTOCOL extends the
>> EFI_SMM_CPU_SERVICE_PROTOCOL
>>> +//  with rendezvous service support.
>>>
>>> +//
>>>
>>> +#define EDKII_SMM_CPU_SERVICE_PROTOCOL_GUID \
>>>
>>> +  { \
>>>
>>> +    0xaa00d50b, 0x4911, 0x428f, {0xb9, 0x1a, 0xa5, 0x9d, 0xdb, 0x13, 0xe2,
>> 0x4c} \
>>> +  }
>>>
>>> +
>>>
>>> +typedef struct _EDKII_SMM_CPU_SERVICE_PROTOCOL
>> EDKII_SMM_CPU_SERVICE_PROTOCOL;
>>> +
>>>
>>> +/**
>>>
>>> +  Wait for all APs to arrive SMM mode in given timeout constraint.
>>>
>>> +
>>>
>>> +  @param  This                  A pointer to the SMM_CPU_SERVICE_PROTOCOL
>> instance.
>>> +  @param  BlockingMode          Block or non-block mode.
>>>
>>> +
>>>
>>> +  @retval EFI_SUCCESS           All APs have arrived SMM mode except SMI
>> disabled APs.
>>> +  @retval EFI_TIMEOUT           There are APs not in SMM mode in given
>> timeout constraint.
>>> +
>>>
>>> +**/
>>>
>>> +typedef
>>>
>>> +EFI_STATUS
>>>
>>> +(EFIAPI *EDKII_WAIT_FOR_ALL_PROCESSOR) (
>>>
>>> +  IN  EDKII_SMM_CPU_SERVICE_PROTOCOL  *This,
>>>
>>> +  IN  BOOLEAN                         BlockingMode
>>>
>>> +  );
>>>
>>> +
>>>
>>> +struct _EDKII_SMM_CPU_SERVICE_PROTOCOL {
>>>
>>> +  EFI_SMM_GET_PROCESSOR_INFO          GetProcessorInfo;
>>>
>>> +  EFI_SMM_SWITCH_BSP                  SwitchBsp;
>>>
>>> +  EFI_SMM_ADD_PROCESSOR               AddProcessor;
>>>
>>> +  EFI_SMM_REMOVE_PROCESSOR            RemoveProcessor;
>>>
>>> +  EFI_SMM_WHOAMI                      WhoAmI;
>>>
>>> +  EFI_SMM_REGISTER_EXCEPTION_HANDLER  RegisterExceptionHandler;
>>>
>>> +  EDKII_WAIT_FOR_ALL_PROCESSOR        WaitForAllProcessor;
>>>
>>> +};
>>>
>>> +
>>>
>>> +extern EFI_GUID gEdkiiSmmCpuServiceProtocolGuid;
>>>
>>> +
>>>
>>>   #endif
>>>
>>> diff --git
>> a/UefiCpuPkg/Library/SmmCpuRendezvousLib/SmmCpuRendezvousLib.inf
>>> b/UefiCpuPkg/Library/SmmCpuRendezvousLib/SmmCpuRendezvousLib.inf
>>> new file mode 100644
>>> index 0000000000..aff77c5a18
>>> --- /dev/null
>>> +++ b/UefiCpuPkg/Library/SmmCpuRendezvousLib/SmmCpuRendezvousLib.inf
>>> @@ -0,0 +1,32 @@
>>> +## @file
>>>
>>> +# Component description file for CPU SMM Rendezvous check library
>>>
>>> +##
>>>
>>> +
>>>
>>> +[Defines]
>>>
>>> +  INF_VERSION                    = 0x00010005
>>>
>>> +  BASE_NAME                      = SmmCpuRendezvousLib
>>>
>>> +  FILE_GUID                      = 1509Bb36-9Ba4-438B-B195-Ac5914Db14E2
>>>
>>> +  MODULE_TYPE                    = DXE_SMM_DRIVER
>>>
>>> +  VERSION_STRING                 = 1.0
>>>
>>> +  LIBRARY_CLASS                  = SmmCpuRendezvousLib
>>>
>>> +  CONSTRUCTOR                    = SmmCpuRendezvousLibConstructor
>>>
>>> +
>>>
>>> +[Sources]
>>>
>>> +  SmmCpuRendezvousLib.c
>>>
>>> +
>>>
>>> +[Packages]
>>>
>>> +  MdePkg/MdePkg.dec
>>>
>>> +  UefiCpuPkg/UefiCpuPkg.dec
>>>
>>> +
>>>
>>> +[LibraryClasses]
>>>
>>> +  BaseLib
>>>
>>> +  DebugLib
>>>
>>> +  PcdLib
>>>
>>> +  SmmServicesTableLib
>>>
>>> +
>>>
>>> +[Pcd]
>>>
>>> +  gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout                 ##
>> CONSUMES
>>> +
>>>
>>> +[Protocols]
>>>
>>> +  gEdkiiSmmCpuServiceProtocolGuid
>>>
>>> +
>>>
>>> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
>> b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
>>> index 26d07c5b5e..c6f31ace77 100644
>>> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
>>> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
>>> @@ -428,6 +428,7 @@ typedef struct {
>>>     volatile SMM_CPU_SYNC_MODE    EffectiveSyncMode;
>>>
>>>     volatile BOOLEAN              SwitchBsp;
>>>
>>>     volatile BOOLEAN              *CandidateBsp;
>>>
>>> +  volatile BOOLEAN              AllApArrivedWithException;
>>>
>>>     EFI_AP_PROCEDURE              StartupProcedure;
>>>
>>>     VOID                          *StartupProcArgs;
>>>
>>>   } SMM_DISPATCHER_MP_SYNC_DATA;
>>>
>>> @@ -1488,4 +1489,31 @@ IsRestrictedMemoryAccess (
>>>     VOID
>>>
>>>     );
>>>
>>>
>>>
>>> +/**
>>>
>>> +  Choose blocking or non-blocking mode to Wait for all APs
>>>
>>> +
>>>
>>> +  @param  This                  A pointer to the SMM_CPU_SERVICE_PROTOCOL
>> instance.
>>> +  @param  BlockingMode          Blocking or non-blocking mode
>>>
>>> +
>>>
>>> +  @retval EFI_SUCCESS           All APs have arrived SMM mode except SMI
>> disabled APs.
>>> +  @retval EFI_TIMEOUT           There are APs not in SMM mode in given
>> timeout constraint.
>>> +
>>>
>>> +**/
>>>
>>> +EFI_STATUS
>>>
>>> +EFIAPI
>>>
>>> +SmmWaitForAllProcessor (
>>>
>>> +  IN  EDKII_SMM_CPU_SERVICE_PROTOCOL  *This,
>>>
>>> +  IN  BOOLEAN                          BlockingMode
>>>
>>> +  );
>>>
>>> +
>>>
>>> +/**
>>>
>>> +  Choose blocking or non-blocking mode to wait for all APs. True for Blocking
>> and false for not.
>>> +  Insure when this function returns, no AP will execute normal mode code
>> before entering SMM, except SMI disabled APs.
>>> +
>>>
>>> +**/
>>>
>>> +VOID
>>>
>>> +SmmWaitForApArrival (
>>>
>>> +  IN  BOOLEAN  BlockingMode
>>>
>>> +  );
>>>
>>> +
>>>
>>>   #endif
>>>
>>> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
>> b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
>>> index 0e88071c70..1af7280d18 100644
>>> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
>>> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
>>> @@ -107,7 +107,8 @@
>>>     gEfiSmmReadyToLockProtocolGuid           ## NOTIFY
>>>
>>>     gEfiSmmCpuServiceProtocolGuid            ## PRODUCES
>>>
>>>     gEdkiiSmmMemoryAttributeProtocolGuid     ## PRODUCES
>>>
>>> -  gEfiMmMpProtocolGuid                    ## PRODUCES
>>>
>>> +  gEfiMmMpProtocolGuid                     ## PRODUCES
>>>
>>> +  gEdkiiSmmCpuServiceProtocolGuid          ## PRODUCES
>>>
>>>
>>>
>>>   [Guids]
>>>
>>>     gEfiAcpiVariableGuid                     ## SOMETIMES_CONSUMES ## HOB # it is
>> used for S3 boot.
>>> diff --git a/UefiCpuPkg/UefiCpuPkg.dec b/UefiCpuPkg/UefiCpuPkg.dec
>>> index 7de66fde67..c170e7d75d 100644
>>> --- a/UefiCpuPkg/UefiCpuPkg.dec
>>> +++ b/UefiCpuPkg/UefiCpuPkg.dec
>>> @@ -77,7 +77,8 @@
>>>
>>>
>>>   [Protocols]
>>>
>>>     ## Include/Protocol/SmmCpuService.h
>>>
>>> -  gEfiSmmCpuServiceProtocolGuid  = { 0x1d202cab, 0xc8ab, 0x4d5c, { 0x94,
>> 0xf7, 0x3c, 0xfc, 0xc0, 0xd3, 0xd3, 0x35 }}
>>> +  gEfiSmmCpuServiceProtocolGuid   = { 0x1d202cab, 0xc8ab, 0x4d5c, { 0x94,
>> 0xf7, 0x3c, 0xfc, 0xc0, 0xd3, 0xd3, 0x35 }}
>>> +  gEdkiiSmmCpuServiceProtocolGuid = { 0xaa00d50b, 0x4911, 0x428f, { 0xb9,
>> 0x1a, 0xa5, 0x9d, 0xdb, 0x13, 0xe2, 0x4c }}
>>>
>>>
>>>     ## Include/Protocol/SmMonitorInit.h
>>>
>>>     gEfiSmMonitorInitProtocolGuid  = { 0x228f344d, 0xb3de, 0x43bb, { 0xa4,
>> 0xd7, 0xea, 0x20, 0xb, 0x1b, 0x14, 0x82 }}
>>> @@ -304,7 +305,7 @@
>>>     #   0x00  - Traditional CPU synchronization method.<BR>
>>>
>>>     #   0x01  - Relaxed CPU synchronization method.<BR>
>>>
>>>     # @Prompt SMM CPU Synchronization Method.
>>>
>>> -
>> gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode|0x00|UINT8|0x60000014
>>> +
>> gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode|0x01|UINT8|0x60000014
>>>
>>>
>>>     ## Specifies the On-demand clock modulation duty cycle when ACPI feature
>> is enabled.
>>>     # @Prompt The encoded values for target duty cycle modulation.
>>>
>>> --
>>> 2.26.2.windows.1
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>
>
> 
>
>