Re: [edk2-devel] [PATCH v4 1/8] UefiCpuPkg/PiSmmCpuDxeSmm: Optimize Semaphore Sync between BSP and AP

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

Reviewed-by: Ray Ni <ray.ni@intel.com>

Thanks,
Ray
> -----Original Message-----
> From: Wu, Jiaxin <jiaxin.wu@intel.com>
> Sent: Friday, December 15, 2023 5:55 PM
> To: devel@edk2.groups.io
> Cc: Laszlo Ersek <lersek@redhat.com>; Dong, Eric <eric.dong@intel.com>; Ni,
> Ray <ray.ni@intel.com>; Zeng, Star <star.zeng@intel.com>; Kumar, Rahul R
> <rahul.r.kumar@intel.com>; Gerd Hoffmann <kraxel@redhat.com>
> Subject: [PATCH v4 1/8] UefiCpuPkg/PiSmmCpuDxeSmm: Optimize
> Semaphore Sync between BSP and AP
> 
> This patch is to define 3 new functions (WaitForBsp & ReleaseBsp &
> ReleaseOneAp) used for the semaphore sync between BSP & AP. With the
> change, BSP and AP Sync flow will be easy understand as below:
> BSP: ReleaseAllAPs or ReleaseOneAp --> AP: WaitForBsp
> BSP: WaitForAllAPs                 <-- AP: ReleaseBsp
> 
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Zeng Star <star.zeng@intel.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 72
> ++++++++++++++++++++++++++++-------
>  1 file changed, 58 insertions(+), 14 deletions(-)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> index b279f5dfcc..54542262a2 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> @@ -120,10 +120,11 @@ LockdownSemaphore (
> 
>    return Value;
>  }
> 
>  /**
> +  Used for BSP to wait all APs.
>    Wait all APs to performs an atomic compare exchange operation to
> release semaphore.
> 
>    @param   NumberOfAPs      AP number
> 
>  **/
> @@ -139,10 +140,11 @@ WaitForAllAPs (
>      WaitForSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);
>    }
>  }
> 
>  /**
> +  Used for BSP to release all APs.
>    Performs an atomic compare exchange operation to release semaphore
>    for each AP.
> 
>  **/
>  VOID
> @@ -157,10 +159,52 @@ ReleaseAllAPs (
>        ReleaseSemaphore (mSmmMpSyncData->CpuData[Index].Run);
>      }
>    }
>  }
> 
> +/**
> +  Used for BSP to release one AP.
> +
> +  @param      ApSem     IN:  32-bit unsigned integer
> +                        OUT: original integer + 1
> +**/
> +VOID
> +ReleaseOneAp   (
> +  IN OUT  volatile UINT32  *ApSem
> +  )
> +{
> +  ReleaseSemaphore (ApSem);
> +}
> +
> +/**
> +  Used for AP to wait BSP.
> +
> +  @param      ApSem      IN:  32-bit unsigned integer
> +                         OUT: original integer - 1
> +**/
> +VOID
> +WaitForBsp  (
> +  IN OUT  volatile UINT32  *ApSem
> +  )
> +{
> +  WaitForSemaphore (ApSem);
> +}
> +
> +/**
> +  Used for AP to release BSP.
> +
> +  @param      BspSem     IN:  32-bit unsigned integer
> +                         OUT: original integer + 1
> +**/
> +VOID
> +ReleaseBsp   (
> +  IN OUT  volatile UINT32  *BspSem
> +  )
> +{
> +  ReleaseSemaphore (BspSem);
> +}
> +
>  /**
>    Check whether the index of CPU perform the package level register
>    programming during System Management Mode initialization.
> 
>    The index of Processor specified by
> mPackageFirstThreadIndex[PackageIndex]
> @@ -632,11 +676,11 @@ BSPHandler (
>        // Signal all APs it's time for backup MTRRs
>        //
>        ReleaseAllAPs ();
> 
>        //
> -      // WaitForSemaphore() may wait for ever if an AP happens to enter
> SMM at
> +      // WaitForAllAPs() may wait for ever if an AP happens to enter SMM
> at
>        // exactly this point. Please make sure PcdCpuSmmMaxSyncLoops
> has been set
>        // to a large enough value to avoid this situation.
>        // Note: For HT capable CPUs, threads within a core share the same
> set of MTRRs.
>        // We do the backup first and then set MTRR to avoid race condition
> for threads
>        // in the same core.
> @@ -652,11 +696,11 @@ BSPHandler (
>        // Let all processors program SMM MTRRs together
>        //
>        ReleaseAllAPs ();
> 
>        //
> -      // WaitForSemaphore() may wait for ever if an AP happens to enter
> SMM at
> +      // WaitForAllAPs() may wait for ever if an AP happens to enter SMM
> at
>        // exactly this point. Please make sure PcdCpuSmmMaxSyncLoops
> has been set
>        // to a large enough value to avoid this situation.
>        //
>        ReplaceOSMtrrs (CpuIndex);
> 
> @@ -898,50 +942,50 @@ APHandler (
> 
>    if ((SyncMode == SmmCpuSyncModeTradition) ||
> SmmCpuFeaturesNeedConfigureMtrrs ()) {
>      //
>      // Notify BSP of arrival at this point
>      //
> -    ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);
> +    ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);
>    }
> 
>    if (SmmCpuFeaturesNeedConfigureMtrrs ()) {
>      //
>      // Wait for the signal from BSP to backup MTRRs
>      //
> -    WaitForSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);
> +    WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);
> 
>      //
>      // Backup OS MTRRs
>      //
>      MtrrGetAllMtrrs (&Mtrrs);
> 
>      //
>      // Signal BSP the completion of this AP
>      //
> -    ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);
> +    ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);
> 
>      //
>      // Wait for BSP's signal to program MTRRs
>      //
> -    WaitForSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);
> +    WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);
> 
>      //
>      // Replace OS MTRRs with SMI MTRRs
>      //
>      ReplaceOSMtrrs (CpuIndex);
> 
>      //
>      // Signal BSP the completion of this AP
>      //
> -    ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);
> +    ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);
>    }
> 
>    while (TRUE) {
>      //
>      // Wait for something to happen
>      //
> -    WaitForSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);
> +    WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);
> 
>      //
>      // Check if BSP wants to exit SMM
>      //
>      if (!(*mSmmMpSyncData->InsideSmm)) {
> @@ -977,16 +1021,16 @@ APHandler (
> 
>    if (SmmCpuFeaturesNeedConfigureMtrrs ()) {
>      //
>      // Notify BSP the readiness of this AP to program MTRRs
>      //
> -    ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);
> +    ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);
> 
>      //
>      // Wait for the signal from BSP to program MTRRs
>      //
> -    WaitForSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);
> +    WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);
> 
>      //
>      // Restore OS MTRRs
>      //
>      SmmCpuFeaturesReenableSmrr ();
> @@ -994,26 +1038,26 @@ APHandler (
>    }
> 
>    //
>    // Notify BSP the readiness of this AP to Reset states/semaphore for this
> processor
>    //
> -  ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);
> +  ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);
> 
>    //
>    // Wait for the signal from BSP to Reset states/semaphore for this
> processor
>    //
> -  WaitForSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);
> +  WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);
> 
>    //
>    // Reset states/semaphore for this processor
>    //
>    *(mSmmMpSyncData->CpuData[CpuIndex].Present) = FALSE;
> 
>    //
>    // Notify BSP the readiness of this AP to exit SMM
>    //
> -  ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);
> +  ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);
>  }
> 
>  /**
>    Checks whether the input token is the current used token.
> 
> @@ -1277,11 +1321,11 @@ InternalSmmStartupThisAp (
>    mSmmMpSyncData->CpuData[CpuIndex].Status = CpuStatus;
>    if (mSmmMpSyncData->CpuData[CpuIndex].Status != NULL) {
>      *mSmmMpSyncData->CpuData[CpuIndex].Status = EFI_NOT_READY;
>    }
> 
> -  ReleaseSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);
> +  ReleaseOneAp (mSmmMpSyncData->CpuData[CpuIndex].Run);
> 
>    if (Token == NULL) {
>      AcquireSpinLock (mSmmMpSyncData->CpuData[CpuIndex].Busy);
>      ReleaseSpinLock (mSmmMpSyncData->CpuData[CpuIndex].Busy);
>    }
> --
> 2.16.2.windows.1



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