audk/UefiCpuPkg/Library/MpInitLib
Ray Ni 030ba3097a 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>
2021-03-17 12:39:31 +00:00
..
Ia32 UefiCpuPkg/MpInitLib: Remove unused Lock from MP_CPU_EXCHANGE_INFO 2021-03-08 02:22:37 +00:00
X64 UefiCpuPkg/MpInitLib: Remove unused Lock from MP_CPU_EXCHANGE_INFO 2021-03-08 02:22:37 +00:00
DxeMpInitLib.inf UefiCpuPkg/MpInitLib: Use NASM struc to avoid hardcode offset 2021-03-08 02:22:37 +00:00
DxeMpInitLib.uni UefiCpuPkg: Replace BSD License with BSD+Patent License 2019-04-09 10:58:28 -07:00
DxeMpLib.c UefiCpuPkg, OvmfPkg: Disable interrupts when using the GHCB 2020-11-10 19:07:55 +00:00
Microcode.c UefiCpuPkg/MpInitLib: avoid printing debug messages in AP 2021-03-17 12:39:31 +00:00
MpEqu.inc UefiCpuPkg/MpInitLib: Remove unused Lock from MP_CPU_EXCHANGE_INFO 2021-03-08 02:22:37 +00:00
MpLib.c UefiCpuPkg/MpInitLib: avoid printing debug messages in AP 2021-03-17 12:39:31 +00:00
MpLib.h UefiCpuPkg/MpInitLib: avoid printing debug messages in AP 2021-03-17 12:39:31 +00:00
PeiMpInitLib.inf UefiCpuPkg/MpInitLib: Use NASM struc to avoid hardcode offset 2021-03-08 02:22:37 +00:00
PeiMpInitLib.uni UefiCpuPkg: Replace BSD License with BSD+Patent License 2019-04-09 10:58:28 -07:00
PeiMpLib.c UefiCpuPkg: Allow AP booting under SEV-ES 2020-08-17 02:46:39 +00:00