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 <ray.ni@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>

0 files changed, 0 insertions, 0 deletions