Hi Zhiguang,

May be a fool question.

If we follow the 1^st solution, do we still have any API to enable/disable AP one by one?

How can we handle any scenario like only enable all Aps with specific core type (only big cores or only Atoms) if this API is changed to enable all Aps.

BRs/Jason

From: Wu, Jiaxin <jiaxin.wu@intel.com>
Sent: Thursday, November 21, 2024 5:54 PM
To: Liu, Zhiguang <zhiguang.liu@intel.com>; devel@edk2.groups.io; Ni, Ray <ray.ni@intel.com>; Tan, Dun <dun.tan@intel.com>; Kumar, Rahul R <rahul.r.kumar@intel.com>; Gerd Hoffmann <kraxel@redhat.com>; Kinney, Michael D <michael.d.kinney@intel.com>; Gao, Liming <gaoliming@byosoft.com.cn>
Cc: Kumar, Chandana C <chandana.c.kumar@intel.com>; Zhao, Jason <jason.zhao@intel.com>; Kuo, Donald <donald.kuo@intel.com>
Subject: RE: UefiCpuPkg: Proposal to enable/disable AP parallel

Solution 1, it’s not kind of spec violating. Instead, it’s to add a new capability to the existing interface, and it’s a compatible change, no impact to existing interface usage. I recall we have a guideline that prioritizes code-first approaches if there are no compatibility issues. Mike and Ray can comment on this. If no objection, I also prefer this way.

Solution 2 cannot handle the PPI case, leading to inconsistent behavior between the protocol and PPI for the mpservice2.

Solutions 3 and 4 are more like workarounds to address the specific issue.

Thanks,

Jiaxin

From: Liu, Zhiguang <zhiguang.liu@intel.com>
Sent: Wednesday, November 20, 2024 3:13 PM
To: devel@edk2.groups.io; Ni, Ray <ray.ni@intel.com>; Wu, Jiaxin <jiaxin.wu@intel.com>; Liu, Zhiguang <zhiguang.liu@intel.com>; Tan, Dun <dun.tan@intel.com>; Kumar, Rahul R <rahul.r.kumar@intel.com>; Gerd Hoffmann <kraxel@redhat.com>; Kinney, Michael D <michael.d.kinney@intel.com>; Gao, Liming <gaoliming@byosoft.com.cn>
Cc: Kumar, Chandana C <chandana.c.kumar@intel.com>; Zhao, Jason <jason.zhao@intel.com>; Kuo, Donald <donald.kuo@intel.com>
Subject: UefiCpuPkg: Proposal to enable/disable AP parallel

Hi MdePkg and UefiCpuPkg maintainers and reviewers

Recently, we met a performance issue when waking up disabled APs.

There is usage where BIOS needs to disable all APs, do something and then enable all APs.

Now, we are using the MpService PPI/Protocol EnableDisableAP(). This function can only enable/disable one AP each time.

To enable one AP, MP service needs to send INIT-SIPI-SIPI, which takes around 10ms.

And now, we will have more than 10 APs in a client platform, and it will take more than 100ms.

The function definition of EnableDisableAP is:

typedef

EFI_STATUS

(EFIAPI *EFI_MP_SERVICES_ENABLEDISABLEAP)(

IN EFI_MP_SERVICES_PROTOCOL *This,

IN UINTN ProcessorNumber,

IN BOOLEAN EnableAP,

IN UINT32 *HealthFlag OPTIONAL

);

The input parameter ProcessorNumber accepts a range from 0 to the total number of logical processors minus 1.

To support enable/disable AP parallel, I have below solutions:

Solution1:

Let input parameter ProcessorNumber accept a MAX_UINTN also. MAX_UINTN means to enable/disable all APs.

The draft PR is at https://github.com/tianocore/edk2/pull/6453 When the parameter is MAX_UINTN, EnableDisableAP() will enable/disable APs in a parallel way.

However, we need to change below header files

MdePkg\Include\Protocol\MpService.h

MdePkg\Include\Ppi\MpServices.h

UefiCpuPkg\Include\Ppi\MpServices2.h

The above two follow PI spec. We need to modify the PI spec first.

Solution2:

Similar with solution1, but to avoid violating spec, add a new Protocol named MpServices2. Only change below header files.

UefiCpuPkg\Include\Ppi\MpServices2.h

UefiCpuPkg\Include\Protocol\MpServices2.h (new)

The MdePkg part remains no change.

Solution3:

MpService create new PPI/Protocol to only contain one function EnableDisableAllAps(), which will enable/disable all APs in a parallel way.

Solution4:

Add PPI/Protocol notify in MpLib. The notify call back function will set WakeUpByInitSipiSipi to True. Similar code is removed in https://github.com/tianocore/edk2/pull/6303/commits/f1f8374381019169d421a65a896ab42ed5338c1e

When users need to disable and then enable cores, the flow will be:

Send Init to all APs. (to disable all APs)
Do things that user need to do when all APs are disabled
Notify callback function
Use StartupAllAPs() from existing PPI/Protocol to wake up all APs.

The flow is similar with how S3 SMM code take control APs and then give the control back in old days.

Personally, I prefer solution1. It is simpler, but it does violate spec.

Please let me know your comments or any new idea, please share.

Thanks

Zhiguang