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...@intel.com> Cc: Eric Dong <eric.d...@intel.com> Cc: Nandagopal Sathyanarayanan <nandagopal.sathyanaraya...@intel.com> --- UefiCpuPkg/Library/MpInitLib/MpLib.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c index 3337488892..84f1cb92e3 100644 --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c @@ -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 @@ -805,6 +806,7 @@ FillExchangeInfoData ( ExchangeInfo->CFunction = (UINTN) ApWakeupFunction; ExchangeInfo->ApIndex = 0; ExchangeInfo->NumApsExecuting = 0; + DEBUG ((DEBUG_ERROR, "NumApsExecuting = %p\n", &ExchangeInfo->NumApsExecuting)); ExchangeInfo->InitFlag = (UINTN) CpuMpData->InitFlag; ExchangeInfo->CpuInfo = (CPU_INFO_IN_HOB *) (UINTN) CpuMpData->CpuInfoInHob; ExchangeInfo->CpuMpData = CpuMpData; @@ -1598,6 +1600,7 @@ MpInitLibInitialize ( CpuMpData->Buffer = Buffer; CpuMpData->CpuApStackSize = ApStackSize; CpuMpData->BackupBuffer = BackupBufferAddr; + DEBUG ((DEBUG_ERROR, "BackupBuffer = %p\n", BackupBufferAddr)); CpuMpData->BackupBufferSize = ApResetVectorSize; CpuMpData->WakeupBuffer = (UINTN) -1; CpuMpData->CpuCount = 1; -- 2.21.0.windows.1 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#41727): https://edk2.groups.io/g/devel/message/41727 Mute This Topic: https://groups.io/mt/31878551/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-