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UefiCpuPkg/MpInitLib: Decrease NumApsExecuting only for ApInitConfig 

The patch fixes the bug that the memory under 1MB is modified by
firmware in S3 boot.

Root cause is a racing condition in MpInitLib:
1. BSP: WakeUpByInitSipiSipi is set by NotifyOnS3SmmInitDonePpi()
2. BSP: WakeUpAP() wakes all APs to run certain procedure.
  2.1. AllocateResetVector() uses <1MB memory for wake up vector.
  2.1. FillExchangeInfoData() resets NumApsExecuting to 0.
  2.2. WaitApWakeup() waits AP to clear WAKEUP_AP_SIGNAL.
3. AP: ApWakeupFunction() clears WAKEUP_AP_SIGNAL to inform BSP.
5. BSP: FreeResetVector() restores the <1MB memory
4. AP: ApWakeupFunction() calls the certain procedure.
  4.1. NumApsExecuting is decreased.

#4.1 happens after the 1MB memory is restored so the result is
memory below 1MB is changed by #4.1
It happens only when the AP executes procedure a bit longer.
AP returns back to ApWakeupFunction() from procedure after
BSP restores the <1MB memory.

Since NumApsExecuting is only used when InitFlag == ApInitConfig
for counting the processor count.
The patch moves the NumApsExecuting decrease to the path when
InitFlag == ApInitConfig.

Signed-off-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Cc: Nandagopal Sathyanarayanan <nandagopal.sathyanarayanan@intel.com>
This commit is contained in:
Ray Ni 2019-05-31 17:42:09 +08:00
parent 5b9b0a8da6
commit 9fc1b85fd1
1 changed files with 3 additions and 2 deletions
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5
UefiCpuPkg/Library/MpInitLib/MpLib.c
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@ -1,7 +1,7 @@
/** @file
CPU MP Initialize Library common functions.
Copyright (c) 2016 - 2018, Intel Corporation. All rights reserved.<BR>
Copyright (c) 2016 - 2019, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
@ -619,6 +619,8 @@ ApWakeupFunction (
RestoreVolatileRegisters (&CpuMpData->CpuData[0].VolatileRegisters, FALSE);
InitializeApData (CpuMpData, ProcessorNumber, BistData, ApTopOfStack);
ApStartupSignalBuffer = CpuMpData->CpuData[ProcessorNumber].StartupApSignal;
InterlockedDecrement ((UINT32 *) &CpuMpData->MpCpuExchangeInfo->NumApsExecuting);
} else {
//
// Execute AP function if AP is ready
@ -698,7 +700,6 @@ ApWakeupFunction (
// AP finished executing C code
//
InterlockedIncrement ((UINT32 *) &CpuMpData->FinishedCount);
InterlockedDecrement ((UINT32 *) &CpuMpData->MpCpuExchangeInfo->NumApsExecuting);
//
// Place AP is specified loop mode