Re: [PATCH] UefiCpuPkg/MpInitLib: Do not wakeup AP if only one processor supported

[Laszlo Ersek <lersek@redhat.com>]

On 11/04/16 09:18, Jeff Fan wrote:
> If MaxLogicalProcessorNumber is only 1, we needn't to wake up APs at all
> and needn't to register callback functions.
> 
> It could improve boot performance on single supported system.
> 
> https://bugzilla.tianocore.org/show_bug.cgi?id=204
> 
> Cc: Feng Tian <feng.tian@intel.com>
> Cc: Liming Gao <liming.gao@intel.com>
> Cc: Michael Kinney <michael.d.kinney@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Jeff Fan <jeff.fan@intel.com>
> ---
>  UefiCpuPkg/Library/MpInitLib/DxeMpLib.c |  7 ++++++
>  UefiCpuPkg/Library/MpInitLib/MpLib.c    | 39 +++++++++++++++++++--------------
>  UefiCpuPkg/Library/MpInitLib/PeiMpLib.c |  8 +++++++
>  3 files changed, 37 insertions(+), 17 deletions(-)

The MP services protocol and PPI that depend on this library will remain
available to callers, right?

Thanks
Laszlo

> diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> index b399f1c..eb36d6f 100644
> --- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> @@ -290,6 +290,13 @@ InitMpGlobalData (
>  
>    SaveCpuMpData (CpuMpData);
>  
> +  if (CpuMpData->CpuCount == 1) {
> +    //
> +    // If only BSP exists, return
> +    //
> +    return;
> +  }
> +
>    //
>    // Avoid APs access invalid buff data which allocated by BootServices,
>    // so we will allocate reserved data for AP loop code.
> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> index 56b870e..a0edc55 100644
> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> @@ -1143,6 +1143,7 @@ MpInitLibInitialize (
>    } else {
>      MaxLogicalProcessorNumber = OldCpuMpData->CpuCount;
>    }
> +  ASSERT (MaxLogicalProcessorNumber != 0);
>  
>    AsmGetAddressMap (&AddressMap);
>    ApResetVectorSize = AddressMap.RendezvousFunnelSize + sizeof (MP_CPU_EXCHANGE_INFO);
> @@ -1209,10 +1210,12 @@ MpInitLibInitialize (
>    MtrrGetAllMtrrs (&CpuMpData->MtrrTable);
>  
>    if (OldCpuMpData == NULL) {
> -    //
> -    // Wakeup all APs and calculate the processor count in system
> -    //
> -    CollectProcessorCount (CpuMpData);
> +    if (MaxLogicalProcessorNumber > 1) {
> +      //
> +      // Wakeup all APs and calculate the processor count in system
> +      //
> +      CollectProcessorCount (CpuMpData);
> +    }
>    } else {
>      //
>      // APs have been wakeup before, just get the CPU Information
> @@ -1238,19 +1241,21 @@ MpInitLibInitialize (
>          sizeof (CPU_VOLATILE_REGISTERS)
>          );
>      }
> -    //
> -    // Wakeup APs to do some AP initialize sync
> -    //
> -    WakeUpAP (CpuMpData, TRUE, 0, ApInitializeSync, CpuMpData);
> -    //
> -    // Wait for all APs finished initialization
> -    //
> -    while (CpuMpData->FinishedCount < (CpuMpData->CpuCount - 1)) {
> -      CpuPause ();
> -    }
> -    CpuMpData->InitFlag = ApInitDone;
> -    for (Index = 0; Index < CpuMpData->CpuCount; Index++) {
> -      SetApState (&CpuMpData->CpuData[Index], CpuStateIdle);
> +    if (MaxLogicalProcessorNumber > 1) {
> +      //
> +      // Wakeup APs to do some AP initialize sync
> +      //
> +      WakeUpAP (CpuMpData, TRUE, 0, ApInitializeSync, CpuMpData);
> +      //
> +      // Wait for all APs finished initialization
> +      //
> +      while (CpuMpData->FinishedCount < (CpuMpData->CpuCount - 1)) {
> +        CpuPause ();
> +      }
> +      CpuMpData->InitFlag = ApInitDone;
> +      for (Index = 0; Index < CpuMpData->CpuCount; Index++) {
> +        SetApState (&CpuMpData->CpuData[Index], CpuStateIdle);
> +      }
>      }
>    }
>  
> diff --git a/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c b/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c
> index e242d37..1f2fcb8 100644
> --- a/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c
> @@ -321,6 +321,14 @@ InitMpGlobalData (
>    EFI_STATUS      Status;
>  
>    SaveCpuMpData (CpuMpData);
> +
> +  if (CpuMpData->CpuCount == 1) {
> +    //
> +    // If only BSP exists, return
> +    //
> +    return;
> +  }
> +
>    //
>    // Register an event for EndOfPei
>    //
>