Felix: Sorry for the late response. > -----Original Message----- > From: Felix Polyudov [mailto:fel...@ami.com] > Sent: Friday, May 24, 2019 8:53 PM > To: devel@edk2.groups.io; Gao, Zhichao <zhichao....@intel.com> > Cc: Wang, Jian J <jian.j.w...@intel.com>; Wu, Hao A <hao.a...@intel.com>; Ni, > Ray <ray...@intel.com>; Zeng, Star > <star.z...@intel.com>; Gao, Liming <liming....@intel.com>; Sean Brogan > <sean.bro...@microsoft.com>; Michael Turner > <michael.tur...@microsoft.com>; Bret Barkelew <bret.barke...@microsoft.com>; > Kinney, Michael D <michael.d.kin...@intel.com>; > Dong, Eric <eric.d...@intel.com>; Laszlo Ersek <ler...@redhat.com>; Andrew > Fish (af...@apple.com) <af...@apple.com> > Subject: RE: [edk2-devel] [PATCH 0/6] Fix race condition and add event > protocol > > I think there is a bigger problem with the idle event signaling by > CoreWaitForEvent. > On every iteration CoreWaitForEvent checks user events, and, if none is > signaled, the function signals special idle event. > This itself is not a problem. However, on many (most?) platforms CPU driver > installs idle event handler that calls CpuSleep > (f.i. refer to IdleLoopEventCallback in UefiCpuPkg/CpuDxe/CpuDxe.c and > ArmPkg/Drivers/CpuDxe/CpuDxe.c). > CpuSleep "places the CPU in a sleep state until an interrupt is received", > which changes the nature of the WaitForEvent function arguably > violating the UEFI specification. > > According to the UEFI specification: > "The list of events in the Event array are evaluated in order from first to > last, and this evaluation is repeated until an event is signaled or an > error is detected." > > The sentence above implies continues evaluation (polling model).
Here is repeat. It is not identical to polling model. A check per timer period is also a repeat implementation. So, it follows UEFI spec. > An idle event callback that sends CPU to a sleep state, converts WaitForEvent > from > a continues polling function into a poll-once-per-timer-period function > (timer is typically the only enabled HW interrupt), > which reduces quality of service provided by WaitForEvent and can lead to > missed events. > > For example, UEFI application that reads key strokes using > gBS->WaitForEvent(..)/ConIn->ReadKey(...) sequence > will be losing key strokes if they are coming faster than 18.2 keys per > second on a system based on legacy timer. This case may not be real case. Idle event is added since 2011 year @54cd17e9842d82dae3cd78686e05c4dc37a3540d. I don't get the real issue report. Have you meet with some real issue in the production? > > So, should idle event support be removed from CoreWaitForEvent? > I think we can still keep it. It is edk2 implementation. Thanks Liming > -----Original Message----- > From: devel@edk2.groups.io [mailto:devel@edk2.groups.io] On Behalf Of Gao, > Zhichao > Sent: Friday, May 24, 2019 1:05 AM > To: devel@edk2.groups.io > Cc: Jian J Wang; Hao A Wu; Ray Ni; Star Zeng; Liming gao; Sean Brogan; > Michael Turner; Bret Barkelew; Michael D Kinney; Eric Dong; > Laszlo Ersek > Subject: [edk2-devel] [PATCH 0/6] Fix race condition and add event protocol > > There is a race condition in CoreWaitForEvent function: > If an interrupt happens between CheckEvent and gIdleLoopEvent, > there would be a event pending during cpu sleep. > So it is required to check the gEventPending with the interrupt > disabled. > Implement a gEfiCpu2ProtocolGuid to fix that. The protocol include > one interface to enable interrupt and put the cpu to sleep. > > Add a event protocol gEdkiiCommonEventProtocolGuid to support > all TPL event. It is require for PI drivers that use HW interrput. > > Cc: Jian J Wang <jian.j.w...@intel.com> > Cc: Hao A Wu <hao.a...@intel.com> > cc: Ray Ni <ray...@intel.com> > Cc: Star Zeng <star.z...@intel.com> > Cc: Liming gao <liming....@intel.com> > Cc: Sean Brogan <sean.bro...@microsoft.com> > Cc: Michael Turner <michael.tur...@microsoft.com> > Cc: Bret Barkelew <bret.barke...@microsoft.com> > Cc: Michael D Kinney <michael.d.kin...@intel.com> > Cc: Eric Dong <eric.d...@intel.com> > Cc: Laszlo Ersek <ler...@redhat.com> > > Sean Brogan (5): > MdeModulePkg: Add gEdkiiCommonEventProtocolGuid for event > MdePkg/BaseLib.h: Add EnableInterruptsAndSleep function declare > MdePkg/BaseLib: Implement EnableInterruptsAndSleep > MdePkg: Add gEfiCpu2ProtocolGuid and header file > MdeModulePkg/DxeMain: Implement common event protocol > > Zhichao Gao (1): > UefiCpuPkg/CpuDxe: Implement Cpu2 protocol > > MdeModulePkg/Core/Dxe/DxeMain.h | 64 ++++++++++- > MdeModulePkg/Core/Dxe/DxeMain.inf | 1 + > MdeModulePkg/Core/Dxe/DxeMain/DxeMain.c | 22 ++++ > .../Core/Dxe/DxeMain/DxeProtocolNotify.c | 1 + > MdeModulePkg/Core/Dxe/Event/Event.c | 102 ++++++++++++++++-- > MdeModulePkg/Core/Dxe/Event/Event.h | 2 +- > MdeModulePkg/Include/Protocol/CommonEvent.h | 18 ++++ > MdeModulePkg/MdeModulePkg.dec | 3 + > MdePkg/Include/Library/BaseLib.h | 11 ++ > MdePkg/Include/Protocol/Cpu2.h | 43 ++++++++ > .../Library/BaseLib/Ia32/EnableInterrupts.c | 18 +++- > .../BaseLib/Ia32/EnableInterrupts.nasm | 15 ++- > .../Library/BaseLib/X64/EnableInterrupts.nasm | 15 ++- > MdePkg/MdePkg.dec | 3 + > UefiCpuPkg/CpuDxe/CpuDxe.c | 40 ++++++- > UefiCpuPkg/CpuDxe/CpuDxe.h | 15 +++ > UefiCpuPkg/CpuDxe/CpuDxe.inf | 3 +- > 17 files changed, 358 insertions(+), 18 deletions(-) > create mode 100644 MdeModulePkg/Include/Protocol/CommonEvent.h > create mode 100644 MdePkg/Include/Protocol/Cpu2.h > > -- > 2.21.0.windows.1 > > > > > > Please consider the environment before printing this email. > > The information contained in this message may be confidential and proprietary > to American Megatrends, Inc. This communication is > intended to be read only by the individual or entity to whom it is addressed > or by their designee. If the reader of this message is not the > intended recipient, you are on notice that any distribution of this message, > in any form, is strictly prohibited. Please promptly notify the > sender by reply e-mail or by telephone at 770-246-8600, and then delete or > destroy all copies of the transmission. -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#42392): https://edk2.groups.io/g/devel/message/42392 Mute This Topic: https://groups.io/mt/31741727/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
