[edk2-devel] [PATCH v4] UefiCpuPkg/PiSmmCpu: Don't allocate Token for SmmStartupThisAp

[Laszlo Ersek]

On 03/10/21 11:12, Ray Ni wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3199
> 
> When Token points to mSmmStartupThisApToken, this routine is called
> from SmmStartupThisAp() in non-blocking mode due to
> PcdCpuSmmBlockStartupThisAp == FALSE.
> 
> In this case, caller wants to startup AP procedure in non-blocking
> mode and cannot get the completion status from the Token because there
> is no way to return the Token to caller from SmmStartupThisAp().
> Caller needs to use its specific way to query the completion status.
> 
> There is no need to allocate a token for such case so the 3 overheads
> can be avoided:
> 1. Call AllocateTokenBuffer() when there is no free token.
> 2. Get a free token from the token buffer.
> 3. Call ReleaseToken() in APHandler().
> 
> Signed-off-by: Ray Ni <ray.ni at intel.com>
> Reviewed-by: Eric Dong <eric.dong at intel.com>
> Reviewed-by: Laszlo Ersek <lersek at redhat.com>
> Cc: Rahul Kumar <rahul1.kumar at intel.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 30 ++++++++++++++++++++-------
>  1 file changed, 23 insertions(+), 7 deletions(-)

Thanks for the update, Ray!
Laszlo

> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> index 6227b2428a..fd6583f9d1 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> @@ -1,7 +1,7 @@
>  /** @file
>  SMM MP service implementation
>  
> -Copyright (c) 2009 - 2020, Intel Corporation. All rights reserved.<BR>
> +Copyright (c) 2009 - 2021, Intel Corporation. All rights reserved.<BR>
>  Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
>  
>  SPDX-License-Identifier: BSD-2-Clause-Patent
> @@ -22,6 +22,7 @@ UINTN                                       mSemaphoreSize;
>  SPIN_LOCK                                   *mPFLock = NULL;
>  SMM_CPU_SYNC_MODE                           mCpuSmmSyncMode;
>  BOOLEAN                                     mMachineCheckSupported = FALSE;
> +MM_COMPLETION                               mSmmStartupThisApToken;
>  
>  extern UINTN mSmmShadowStackSize;
>  
> @@ -1240,9 +1241,26 @@ InternalSmmStartupThisAp (
>    mSmmMpSyncData->CpuData[CpuIndex].Procedure = Procedure;
>    mSmmMpSyncData->CpuData[CpuIndex].Parameter = ProcArguments;
>    if (Token != NULL) {
> -    ProcToken= GetFreeToken (1);
> -    mSmmMpSyncData->CpuData[CpuIndex].Token = ProcToken;
> -    *Token = (MM_COMPLETION)ProcToken->SpinLock;
> +    if (Token != &mSmmStartupThisApToken) {
> +      //
> +      // When Token points to mSmmStartupThisApToken, this routine is called
> +      // from SmmStartupThisAp() in non-blocking mode (PcdCpuSmmBlockStartupThisAp == FALSE).
> +      //
> +      // In this case, caller wants to startup AP procedure in non-blocking
> +      // mode and cannot get the completion status from the Token because there
> +      // is no way to return the Token to caller from SmmStartupThisAp().
> +      // Caller needs to use its implementation specific way to query the completion status.
> +      //
> +      // There is no need to allocate a token for such case so the 3 overheads
> +      // can be avoided:
> +      // 1. Call AllocateTokenBuffer() when there is no free token.
> +      // 2. Get a free token from the token buffer.
> +      // 3. Call ReleaseToken() in APHandler().
> +      //
> +      ProcToken = GetFreeToken (1);
> +      mSmmMpSyncData->CpuData[CpuIndex].Token = ProcToken;
> +      *Token = (MM_COMPLETION)ProcToken->SpinLock;
> +    }
>    }
>    mSmmMpSyncData->CpuData[CpuIndex].Status    = CpuStatus;
>    if (mSmmMpSyncData->CpuData[CpuIndex].Status != NULL) {
> @@ -1474,8 +1492,6 @@ SmmStartupThisAp (
>    IN OUT  VOID                      *ProcArguments OPTIONAL
>    )
>  {
> -  MM_COMPLETION               Token;
> -
>    gSmmCpuPrivate->ApWrapperFunc[CpuIndex].Procedure = Procedure;
>    gSmmCpuPrivate->ApWrapperFunc[CpuIndex].ProcedureArgument = ProcArguments;
>  
> @@ -1486,7 +1502,7 @@ SmmStartupThisAp (
>      ProcedureWrapper,
>      CpuIndex,
>      &gSmmCpuPrivate->ApWrapperFunc[CpuIndex],
> -    FeaturePcdGet (PcdCpuSmmBlockStartupThisAp) ? NULL : &Token,
> +    FeaturePcdGet (PcdCpuSmmBlockStartupThisAp) ? NULL : &mSmmStartupThisApToken,
>      0,
>      NULL
>      );
> 



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