Does https://github.com/tianocore/edk2/blob/master/UefiCpuPkg/Library/MpInitLib/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. View/Reply Online (#70713): https://edk2.groups.io/g/devel/message/70713 Mute This Topic: https://groups.io/mt/80035510/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
