Jiewen, You are right!:) * In the Pentium 4, Intel Xeon, and P6 family processors, when a processor that is designated as an * application processor during an MP initialization sequence is waiting for a startup IPI (SIPI), it is in * a mode where SMIs are masked. However if a SMI is received while an application processor is in * the wait for SIPI mode, the SMI will be pended. The processor then responds on receipt of a SIPI by * immediately servicing the pended SMI and going into SMM before handling the SIPI.
> -----Original Message----- > From: Yao, Jiewen <jiewen....@intel.com> > Sent: Thursday, June 9, 2022 4:53 PM > To: Ni, Ray <ray...@intel.com>; devel@edk2.groups.io > Cc: Kinney, Michael D <michael.d.kin...@intel.com>; Tom Lendacky > <thomas.lenda...@amd.com> > Subject: RE: Why need to put AP in HLT/MWAIT in ExitBootServices callback > > I remember a wait-for-SIPI CPU cannot response to SMI. > > We do want to let AP response SMI to perform some action, because some SMM > code will rely on all APs in SMM. > > Thank you > Yao Jiewen > > > > -----Original Message----- > > From: Ni, Ray <ray...@intel.com> > > Sent: Thursday, June 9, 2022 4:46 PM > > To: devel@edk2.groups.io > > Cc: Ni, Ray <ray...@intel.com>; Kinney, Michael D > > <michael.d.kin...@intel.com>; Tom Lendacky <thomas.lenda...@amd.com>; > > Yao, Jiewen <jiewen....@intel.com> > > Subject: Why need to put AP in HLT/MWAIT in ExitBootServices callback > > > > All, > > When I am reviewing today's MpInitLib code, I don't understand why below > > complex logic is there to put AP in HLT or MWAIT on a ExitBootServices event > > callback. > > https://github.com/tianocore/edk2/blob/ff36b2550f94dc5fac838cf298ae5a23c > > fddf204/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c#L423 > > https://github.com/tianocore/edk2/blob/ff36b2550f94dc5fac838cf298ae5a23c > > fddf204/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm#L424 > > > > The above code is to put AP in a state that when it's woken up by > > interrupts or > > SMIs, it's executing code and using stack in reserved memory. > > (not in BootServices memory which might be overwritten by OS.) > > > > But according to the SDM content below, we can simply send a INIT IPI to > > all APs > > to let AP enter a wait-for-SIPI state. > > Then a simple SendInitIpiAllExcludingSelf() from BSP can replace all the > > complicated code above. > > > > * The MP protocol will be executed only after a power-up or RESET. If the MP > > protocol has been completed and a > > * BSP has been chosen, subsequent INITs (either to a specific processor or > > system wide) do not cause the MP > > * protocol to be repeated. Instead, each processor examines its BSP flag > > (in the > > APIC_BASE MSR) to determine > > * whether it should execute the BIOS boot-strap code (if it is the BSP) or > > enter a > > wait-for-SIPI state (if it is an > > * AP). > > > > Did I miss something here? > > > > Thanks, > > Ray -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#90386): https://edk2.groups.io/g/devel/message/90386 Mute This Topic: https://groups.io/mt/91641523/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
