Commits on Mar 17, 2021

1. UefiCpuPkg/MpInitLib: avoid printing debug messages in AP …

   MpInitLib contains a function MicrocodeDetect() which is called by
   all threads as an AP procedure.
   Today this function contains below code:
   
       if (CurrentRevision != LatestRevision) {
         AcquireSpinLock(&CpuMpData->MpLock);
         DEBUG ((
           EFI_D_ERROR,
           "Updated microcode signature [0x%08x] does not match \
           loaded microcode signature [0x%08x]\n",
           CurrentRevision, LatestRevision
           ));
         ReleaseSpinLock(&CpuMpData->MpLock);
       }
   
   When the if-check is passed, the code may call into PEI services:
   1. AcquireSpinLock
      When the PcdSpinTimeout is not 0, TimerLib
      GetPerformanceCounterProperties() is called. And some of the
      TimerLib implementations would get the information cached in
      HOB. But AP procedure cannot call PEI services to retrieve the
      HOB list.
   
   2. DEBUG
      Certain DebugLib relies on ReportStatusCode services and the
      ReportStatusCode PPI is retrieved through the PEI services.
      DebugLibSerialPort should be used.
      But when SerialPortLib is implemented to depend on PEI services,
      even using DebugLibSerialPort can still cause AP calls PEI
      services resulting hang.
   
   It causes a lot of debugging effort on the platform side.
   
   There are 2 options to fix the problem:
   1. make sure platform DSC chooses the proper DebugLib and set the
      PcdSpinTimeout to 0. So that AcquireSpinLock and DEBUG don't call
      PEI services.
   2. remove the AcquireSpinLock and DEBUG call from the procedure.
   
   Option #2 is preferred because it's not practical to ask every
   platform DSC to be written properly.
   
   Following option #2, there are two sub-options:
   2.A. Just remove the if-check.
   2.B. Capture the CurrentRevision and ExpectedRevision in the memory
        for each AP and print them together from BSP.
   
   The patch follows option 2.B.
   
   Signed-off-by: Ray Ni <[email protected]>
   Reviewed-by: Eric Dong <[email protected]>
   Acked-by: Laszlo Ersek <[email protected]>
   Cc: Rahul Kumar <[email protected]>

   

   niruiyu committed Mar 17, 2021
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