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

[Laszlo Ersek <lersek@redhat.com>]

On 11/07/16 01:47, Fan, Jeff wrote:
> Laszlo,
> 
> Yes.  MP PPI and Protocol still be installed even there is only one processor supported or found?

I'm sorry -- are you confirming that the PPI and the protocol will
exist, or are you asking if I would like them to exist?

(I'm confused by the question mark at the end of your second sentence.)

Thanks!
Laszlo

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Laszlo Ersek
> Sent: Saturday, November 05, 2016 12:40 AM
> To: Fan, Jeff; edk2-devel@ml01.01.org
> Cc: Kinney, Michael D; Tian, Feng; Gao, Liming
> Subject: Re: [edk2] [PATCH] UefiCpuPkg/MpInitLib: Do not wakeup AP if only one processor supported
> 
> 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
>>    //
>>
> 
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