Star, You are right. There is no sequence requirement between FinishedCount++ and NumApsExecuting--.
In fact, I have submitted another bugzilla https://bugzilla.tianocore.org/show_bug.cgi?id=3179. With that Bugzilla, the wait on (FinishedCount == CpuCount - 1) will be removed for the 1st wake up case. Thanks, Ray > -----Original Message----- > From: Zeng, Star <star.z...@intel.com> > Sent: Monday, January 25, 2021 4:43 PM > To: Kinney, Michael D <michael.d.kin...@intel.com>; devel@edk2.groups.io > Cc: Dong, Eric <eric.d...@intel.com>; Ni, Ray <ray...@intel.com>; Laszlo > Ersek <ler...@redhat.com>; Kumar, Rahul1 <rahul1.ku...@intel.com>; > Zeng, Star <star.z...@intel.com> > Subject: RE: [edk2-devel] [Patch 1/1] UefiCpuPkg/Library/MpInitLib: Fix AP > VolatileRegisters race condition > > Mike, > > Oh, see it. > There is no sequence dependence between FinishedCount increment and > NumApsExecuting decrement, right? > > InterlockedIncrement ((UINT32 *) &CpuMpData->FinishedCount); > > InterlockedDecrement ((UINT32 *) &CpuMpData->MpCpuExchangeInfo- > >NumApsExecuting); > > > Thanks, > Star > > > -----Original Message----- > > From: Kinney, Michael D <michael.d.kin...@intel.com> > > Sent: Monday, January 25, 2021 1:16 PM > > To: Zeng, Star <star.z...@intel.com>; devel@edk2.groups.io; Kinney, > > Michael D <michael.d.kin...@intel.com> > > Cc: Dong, Eric <eric.d...@intel.com>; Ni, Ray <ray...@intel.com>; Laszlo > > Ersek <ler...@redhat.com>; Kumar, Rahul1 <rahul1.ku...@intel.com> > > Subject: RE: [edk2-devel] [Patch 1/1] UefiCpuPkg/Library/MpInitLib: Fix AP > > VolatileRegisters race condition > > > > Hi Star, > > > > That line is only active when (CpuMpData->SevEsIsEnabled) is TRUE. > > > > The race condition addressed by this BZ is for systems with SecEsIsEnabled > > FALSE. > > > > From comments in this file the SecEsIsEnabled cases have already been > > handled. > > > > Mike > > > > > -----Original Message----- > > > From: Zeng, Star <star.z...@intel.com> > > > Sent: Sunday, January 24, 2021 7:15 PM > > > To: devel@edk2.groups.io; Kinney, Michael D > > > <michael.d.kin...@intel.com> > > > Cc: Dong, Eric <eric.d...@intel.com>; Ni, Ray <ray...@intel.com>; > > > Laszlo Ersek <ler...@redhat.com>; Kumar, Rahul1 > > > <rahul1.ku...@intel.com>; Zeng, Star <star.z...@intel.com> > > > Subject: RE: [edk2-devel] [Patch 1/1] UefiCpuPkg/Library/MpInitLib: > > > Fix AP VolatileRegisters race condition > > > > > > Does > > > > > > https://github.com/tianocore/edk2/blob/master/UefiCpuPkg/Library/MpIni > > > tLib/MpLib.c#L909 (also decrements > > > NumApsExecuting) also need be handled? > > > > > > Thanks, > > > Star > > > > > > > -----Original Message----- > > > > From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of > > > > Michael D Kinney > > > > Sent: Saturday, January 23, 2021 1:10 AM > > > > To: devel@edk2.groups.io > > > > Cc: Dong, Eric <eric.d...@intel.com>; Ni, Ray <ray...@intel.com>; > > > > Laszlo Ersek <ler...@redhat.com>; Kumar, Rahul1 > > > > <rahul1.ku...@intel.com> > > > > Subject: [edk2-devel] [Patch 1/1] UefiCpuPkg/Library/MpInitLib: Fix > > > > AP VolatileRegisters race condition > > > > > > > > REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3182 > > > > > > > > Fix the order of operations in ApWakeupFunction() when > > > > PcdCpuApLoopMode is set to HLT mode that uses INIT-SIPI-SIPI to > wake > > > > APs. In this mode, volatile state is restored and saved each time a > > > > INIT-SIPI-SIPI is sent to an AP to request a function to be executed > > > > on the AP. When the function is completed the volatile state of the > > > > AP is saved. However, the counters NumApsExecuting and > > > > FinishedCount are updated before the volatile state is saved. This > > > > allows for a race condition window for the BSP that is waiting on > > > > these counters to request a new INIT-SIPI-SIPI before all the APs > > > > have completely saved their volatile state. The fix is to save the > > > > AP volatile state before updating the NumApsExecuting and > > > > FinishedCount counters. > > > > > > > > Cc: Eric Dong <eric.d...@intel.com> > > > > Cc: Ray Ni <ray...@intel.com> > > > > Cc: Laszlo Ersek <ler...@redhat.com> > > > > Cc: Rahul Kumar <rahul1.ku...@intel.com> > > > > Signed-off-by: Michael D Kinney <michael.d.kin...@intel.com> > > > > --- > > > > UefiCpuPkg/Library/MpInitLib/MpLib.c | 31 > > > > ++++++++++++++++------------ > > > > 1 file changed, 18 insertions(+), 13 deletions(-) > > > > > > > > diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c > > > > b/UefiCpuPkg/Library/MpInitLib/MpLib.c > > > > index 681fa79b4cff..8b1f7f84bad6 100644 > > > > --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c > > > > +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c > > > > @@ -769,15 +769,6 @@ ApWakeupFunction ( > > > > RestoreVolatileRegisters > > > > (&CpuMpData->CpuData[0].VolatileRegisters, > > > > FALSE); > > > > InitializeApData (CpuMpData, ProcessorNumber, BistData, > > > > ApTopOfStack); > > > > ApStartupSignalBuffer = CpuMpData- > > > > >CpuData[ProcessorNumber].StartupApSignal; > > > > - > > > > - // > > > > - // Delay decrementing the APs executing count when SEV-ES is > > enabled > > > > - // to allow the APs to issue an AP_RESET_HOLD before the BSP > > possibly > > > > - // performs another INIT-SIPI-SIPI sequence. > > > > - // > > > > - if (!CpuMpData->SevEsIsEnabled) { > > > > - InterlockedDecrement ((UINT32 *) &CpuMpData- > > > > >MpCpuExchangeInfo->NumApsExecuting); > > > > - } > > > > } else { > > > > // > > > > // Execute AP function if AP is ready @@ -866,19 +857,33 @@ > > > > ApWakeupFunction ( > > > > } > > > > } > > > > > > > > + if (CpuMpData->ApLoopMode == ApInHltLoop) { > > > > + // > > > > + // Save AP volatile registers > > > > + // > > > > + SaveVolatileRegisters (&CpuMpData- > > > > >CpuData[ProcessorNumber].VolatileRegisters); > > > > + } > > > > + > > > > // > > > > // AP finished executing C code > > > > // > > > > InterlockedIncrement ((UINT32 *) &CpuMpData->FinishedCount); > > > > > > > > + if (CpuMpData->InitFlag == ApInitConfig) { > > > > + // > > > > + // Delay decrementing the APs executing count when SEV-ES is > > enabled > > > > + // to allow the APs to issue an AP_RESET_HOLD before the BSP > > possibly > > > > + // performs another INIT-SIPI-SIPI sequence. > > > > + // > > > > + if (!CpuMpData->SevEsIsEnabled) { > > > > + InterlockedDecrement ((UINT32 *) &CpuMpData- > > > > >MpCpuExchangeInfo->NumApsExecuting); > > > > + } > > > > + } > > > > + > > > > // > > > > // Place AP is specified loop mode > > > > // > > > > if (CpuMpData->ApLoopMode == ApInHltLoop) { > > > > - // > > > > - // Save AP volatile registers > > > > - // > > > > - SaveVolatileRegisters (&CpuMpData- > > > > >CpuData[ProcessorNumber].VolatileRegisters); > > > > // > > > > // Place AP in HLT-loop > > > > // > > > > -- > > > > 2.29.2.windows.2 > > > > > > > > > > > > > > > > > > > > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. 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