Re: [edk2-devel] [PATCH 1/5] UefiCpuPkg/MpInitLib: Add ProcessorIndex argument to GetMpHandOffHob()

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

>    EFI_HOB_GUID_TYPE  *GuidHob;
>    MP_HAND_OFF        *MpHandOff;
> 
> -  MpHandOff = NULL;
> -  GuidHob   = GetFirstGuidHob (&mMpHandOffGuid);
> -  if (GuidHob != NULL) {
> +  for (GuidHob = GetFirstGuidHob (&mMpHandOffGuid);
> +       GuidHob != NULL;
> +       GuidHob = GetNextGuidHob (&mMpHandOffGuid, GET_NEXT_HOB
> (GuidHob)))
> +  {
>      MpHandOff = (MP_HAND_OFF *)GET_GUID_HOB_DATA (GuidHob);
> +    if (MpHandOff->ProcessorIndex == ProcessorIndex) {
> +      return MpHandOff;
> +    }

Gerd,
The code is doing correctly but I have concerns about the performance impact.

With the prototype GetMpHandOffHob(), callers call it multiple times to enumerate all HOB instances.

But every call is a HOB list enumeration from top of the HOB list which may be slow in a platform
that contains lots of HOB items and the MpHandOff HOB instances happen to be in the very bottom.

How about add another parameter "HobStart" to GetMpHandOffHob()? So that only the first call to
GetMpHandOffHob() is a HOB list enumeration from top, latter calls start from the next HOB of the previous
found MpHandOff HOB instance.


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