From 9fc1b85fd16b1740de66e99a406a08471eeafa61 Mon Sep 17 00:00:00 2001 From: Ray Ni Date: Fri, 31 May 2019 17:42:09 +0800 Subject: [PATCH] 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 Reviewed-by: Laszlo Ersek Reviewed-by: Eric Dong Cc: Nandagopal Sathyanarayanan --- UefiCpuPkg/Library/MpInitLib/MpLib.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c index 3337488892..6f51bc4ebf 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.
+ Copyright (c) 2016 - 2019, Intel Corporation. All rights reserved.
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 -- 2.39.2