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

[Laszlo Ersek <lersek@redhat.com>]

On 11/08/16 01:55, Fan, Jeff wrote:
> Laszlo,
> 
> Oh. Sorry for the question mark in my last sentence and confusing you. :-) it should be point. It's my typo.
> 
> MP PPI and the protocol DO exist even there is only one processor in the system.
> 
> Thanks!
> Jeff

Thanks. With that guarantee, the proposed change looks sensible.

I didn't review the patch, but I want to confirm that (with the above
guarantee) I agree with its goal:

Acked-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Laszlo Ersek
> Sent: Monday, November 07, 2016 9:37 PM
> 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 11/07/16 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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