UefiCpuPkg/PiSmmCpuDxeSmm: dynamic PcdCpuSmmApSyncTimeout, PcdCpuSmmSyncMode

UefiCpuPkg/PiSmmCpuDxeSmm: dynamic PcdCpuSmmApSyncTimeout, PcdCpuSmmSyncMode

Move the declaration of these PCDs from the

  [PcdsFixedAtBuild, PcdsPatchableInModule]

section of "UefiCpuPkg/UefiCpuPkg.dec" to the

  [PcdsFixedAtBuild, PcdsPatchableInModule, PcdsDynamic, PcdsDynamicEx]

section. Their types, default values, and token values remain unchanged.

Only UefiCpuPkg/PiSmmCpuDxeSmm consumes these PCDs, specifically on the
call stack of its entry point function, and it turns them into static or
dynamically allocated data in SMRAM:

  PiCpuSmmEntry()                            [PiSmmCpuDxeSmm.c]
    InitializeSmmTimer()                     [SyncTimer.c]
      PcdCpuSmmApSyncTimeout
      -> mTimeoutTicker
    InitializeMpServiceData()                [MpService.c]
      InitializeMpSyncData()                 [MpService.c]
        PcdCpuSmmSyncMode
        -> mSmmMpSyncData->EffectiveSyncMode

However, there's another call path to fetching "PcdCpuSmmSyncMode", namely

  SmmInitHandler()                           [PiSmmCpuDxeSmm.c]
    InitializeMpSyncData()                   [MpService.c]
      PcdCpuSmmSyncMode
      -> mSmmMpSyncData->EffectiveSyncMode

and this path is exercised during S3 resume (as stated by the comment in
SmmInitHandler() too, "Initialize private data during S3 resume").

While we can call the PCD protocol (via PcdLib) for fetching dynamic PCDs
in the entry point function, we cannot do that at S3 resume. Therefore
pre-fetch PcdCpuSmmSyncMode into a new global variable (which lives in
SMRAM) in InitializeMpServiceData(), just before calling
InitializeMpSyncData(). This way InitializeMpSyncData() can retrieve the
stashed PCD value from SMRAM, regardless of the boot mode.

Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=230
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>