13. DXE Boot Services Protocol

13.1. Overview

This chapter defines the services required for the Multiprocessor (MP) Services Protocol of Platform Initialization Specification. This specification does the following:

Describes the basic components of the MP Services Protocol
Provides code definitions for the MP Services Protocol and the MP-related type definitions.

13.2. Conventions and Abbreviations

The following terms are used throughout this specification.

AP: Application processor. All other processors in a computer system other than the boot-strap processor are called application processors.
BSP: Boot-strap processor. A processor in an MP platform that is chosen to execute the modules that are necessary for booting the system. It is not necessary that the same processor that was selected earlier as a BSP shall remain a BSP throughout an entire boot session.
DXE: Driver Execute Environment. Environment to support running modular code in the form of EFI drivers; common to all platforms; typically in C language.
EFI: Extensible Firmware Interface - the specification containing interface definitions for firmware. This includes both interfaces used by the operating system for booting as well as interfaces that are used for internal construction of firmware.
MP: Multiprocessor.

13.3. MP Services Protocol Overview

The MP Services Protocol provides a generalized way of performing following tasks:

Retrieving information of multi-processor environment and MP-related status of specific processors.
Dispatching user-provided function to APs.
Maintain MP-related processor status.

The MP Services Protocol must be produced on any system with more than one logical processor.

The Protocol is available only during boot time.

MP Services Protocol is hardware-independent. Most of the logic of this protocol is architecturally neutral. It abstracts the multi-processor environment and status of processors, and provides interfaces to retrieve information, maintain, and dispatch.

MP Services Protocol may be consumed by ACPI module. The ACPI module may use this protocol to retrieve data that are needed for an MP platform and report them to OS.

MP Services Protocol may also be used to program and configure processors, such as MTRR synchronization for memory space attributes setting in DXE Services.

MP Services Protocol may be used by non-CPU DXE drivers to speed up platform boot by taking advantage of the processing capabilities of the APs, for example, using APs to help test system memory in parallel with other device initialization.

Diagnostics applications may also use this protocol for multi-processor.

13.4. MP Services Protocol

This section contains the basic definitions of the MP Services Protocol.

13.4.1. EFI_MP_SERVICES_PROTOCOL

Summary

When installed, the MP Services Protocol produces a collection of services that are needed for MP management.

GUID

#define EFI_MP_SERVICES_PROTOCOL_GUID \
  {0x3fdda605,0xa76e,0x4f46,{0xad,0x29,0x12,0xf4,\
  0x53,0x1b,0x3d,0x08}}

Protocol Interface Structure

typedef struct _EFI_MP_SERVICES_PROTOCOL {
  EFI_MP_SERVICES_GET_NUMBER_OF_PROCESSORS  GetNumberOfProcessors;
  EFI_MP_SERVICES_GET_PROCESSOR_INFO        GetProcessorInfo;
  EFI_MP_SERVICES_STARTUP_ALL_APS           StartupAllAPs;
  EFI_MP_SERVICES_STARTUP_THIS_AP           StartupThisAP;
  EFI_MP_SERVICES_SWITCH_BSP                SwitchBSP;
  EFI_MP_SERVICES_ENABLEDISABLEAP           EnableDisableAP;
  EFI_MP_SERVICES_WHOAMI                    WhoAmI;
} EFI_MP_SERVICES_PROTOCOL;

Parameters

GetNumberOfProcessors: Gets the number of logical processors and the number of enabled logical processors in the system.

GetProcessorInfo: Gets detailed information on the requested processor at the instant this call is made.

StartupAllAPs: Starts up all the enabled APs in the system to run the function provided by the caller.

StartupThisAP: Starts up the requested AP to run the function provided by the caller.

SwitchBSP: Switches the requested AP to be the BSP from that point onward. This service changes the BSP for all purposes.

EnableDisableAP: Enables and disables the given AP from that point onward.

WhoAmI: Gets the handle number of the caller processor.

Description

The MP Services Protocol must be produced on any system with more than one logical processor. Before the UEFI event EFI_EVENT_LEGACY_BOOT_GUID or EFI_EVENT_GROUP_EXIT_BOOT_SERVICES is signaled, the module that produces this protocol is required to place all APs into an idle state whenever the APs are disabled or the APs are not executing code as requested through the StartupAllAPs() or StartupThisAP() services. The idle state of an AP is implementation dependent before the UEFI event EFI_EVENT_LEGACY_BOOT_GUID or EFI_EVENT_GROUP_EXIT_BOOT_SERVICES is signaled.

After the UEFI event EFI_EVENT_LEGACY_BOOT_GUID or EFI_EVENT_GROUP_EXIT_BOOT_SERVICES is signaled, all the APs must be placed in the OS compatible CPU state as defined by the UEFI Specification. Implementations of this protocol may use the UEFI event EFI_EVENT_LEGACY_BOOT_GUID or EFI_EVENT_GROUP_EXIT_BOOT_SERVICES to force APs into the OS compatible state as defined by the UEFI Specification. Modules that use this protocol must guarantee that all non-blocking mode requests on all APs have been completed before the UEFI event EFI_EVENT_LEGACY_BOOT_GUID or EFI_EVENT_GROUP_EXIT_BOOT_SERVICES is signaled. Since the order that event notification functions in the same event group are executed is not deterministic, an event of type EFI_EVENT_LEGACY_BOOT_GUID or EFI_EVENT_GROUP_EXIT_BOOT_SERVICES can not be used to guarantee that APs have completed their non-blocking mode requests.

13.4.2. EFI_MP_SERVICES_PROTOCOL.GetNumberOfProcessors()

Summary

This service retrieves the number of logical processor in the platform and the number of those logical processors that are currently enabled. This service may only be called from the BSP.

Prototype

typedef
EFI_STATUS
(EFIAPI *EFI_MP_SERVICES_GET_NUMBER_OF_PROCESSORS) (
  IN EFI_MP_SERVICES_PROTOCOL    *This,
  OUT UINTN                      *NumberOfProcessors,
  OUT UINTN                      *NumberOfEnabledProcessors
  );

Parameters

This: A pointer to the EFI_MP_SERVICES_PROTOCOL instance.

NumberOfProcessors: Pointer to the total number of logical processors in the system, including the BSP and all enabled and disabled APs.

NumberOfEnabledProcessors: Pointer to the number of logical processors in the platform including the BSP that are currently enabled.

Description

This function is used to retrieve the following information:

The number of logical processors that are present in the system
The number of enabled logical processors in the system at the instant this call is made.

Since MP Service Protocol provides services to enable and disable processors dynamically, the number of enabled logical processors may vary during the course of a boot session.

This service may only be called from the BSP.

If this service is called from an AP, then EFI_DEVICE_ERROR is returned. If NumberOfProcessors or NumberOfEnabledProcessors is NULL , then EFI_INVALID_PARAMETER i s returned. Otherwise, the total number of processors is returned in NumberOfProcessors , the number of currently enabled processor is returned in NumberOfEnabledProcessors , and EFI_SUCCESS is returned.

Status Codes Returned

Table 13.3 Status Codes Returned
EFI_SUCCESS	The number of logical processors and enabled logical processors was retrieved.
EFI_DEVICE_ERROR	The calling processor is an AP.
EFI_INVALID_PARAMETER	`NumberOfProcessors` is `NULL`.
EFI_INVALID_PARAMETER	`NumberOfEnabledProcessors` is `NULL`.

13.4.3. EFI_MP_SERVICES_PROTOCOL.GetProcessorInfo()

Summary

Gets detailed MP-related information on the requested processor at the instant this call is made. This service may only be called from the BSP.

Prototype

typedef
EFI_STATUS
(EFIAPI *EFI_MP_SERVICES_GET_PROCESSOR_INFO) (
  IN EFI_MP_SERVICES_PROTOCOL     *This,
  IN UINTN                        *ProcessorNumber,
  OUT EFI_PROCESSOR_INFORMATION   *ProcessorInfoBuffer
  );

Parameters

this-1: A pointer to the EFI_MP_SERVICES_PROTOCOL instance.
processornumber: The handle number of processor. The range is from 0 to the total number of logical processors minus 1. The total number of logical processors can be retrieved by EFI_MP_SERVICES_PROTOCOL.GetNumberOfProcessors().
processorinfobuffer: A pointer to the buffer where information for the requested processor is deposited. The buffer is allocated by the caller. Type EFI_PROCESSOR_INFORMATION is defined in “Related Definitions” below.

Description

This service retrieves detailed MP-related information about any processor on the platform. Note the following:

The processor information may change during the course of a boot session.
The data of information presented here is entirely MP related.

Information regarding the number of caches and their sizes, frequency of operation, slot numbers is all considered platform-related information and is not provided by this service.

This service may only be called from the BSP.

//*******************************************************
// EFI_PROCESSOR_INFORMATION
//*******************************************************
typedef struct {
  UINT64                            ProcessorId;
  UINT32                            StatusFlag;
  EFI_CPU_PHYSICAL_LOCATION         Location;
  EXTENDED_PROCESSOR_INFORMATION    ExtendedInformation;
} EFI_PROCESSOR_INFORMATION;

ProcessorId: The unique processor ID determined by system hardware. For IPF, the lower 16 bits contains id/eid, and higher bits are reserved.

StatusFlag: Flags indicating if the processor is BSP or AP, if the processor is enabled or disabled, and if the processor is healthy. The bit format is defined below.

Location: The physical location of the processor, including the physical package number that identifies the cartridge, the physical core number within package, and logical thread number within core. Type EFI_PHYSICAL_LOCATION is defined below.

ExtendedInformation: The extended information of the processor. This field is filled only when CPU_V2_EXTENDED_TOPOLOGY is set in parameter ProcessorNumber . Value CPU_V2_EXTENDED_TOPOLOGY and type EXTENDED_PROCESSOR_INFORMATION are defined below.

//*******************************************************
// StatusFlag Bits Definition
//*******************************************************
#define PROCESSOR_AS_BSP_BIT        0x00000001
#define PROCESSOR_ENABLED_BIT       0x00000002
#define PROCESSOR_HEALTH_STATUS_BIT 0x00000004

PROCESSOR_AS_BSP_BIT: This bit indicates whether the processor is playing the role of BSP. If the bit is 1, then the processor is BSP. Otherwise, it is AP.
PROCESSOR_ENABLED_BIT: This bit indicates whether the processor is enabled. If the bit is 1, then the processor is enabled. Otherwise, it is disabled.
PROCESSOR_HEALTH_STATUS_BIT: This bit indicates whether the processor is healthy. If the bit is 1, then the processor is healthy. Otherwise, some fault has been detected for the processor.

Bits 3..31 are reserved and must be 0. The following table shows all the possible combinations of the StatusFlag bits:

Table 13.4 StatusFlag bits
BSP	ENABLED	HEALTH	Description
0	0	0	Unhealthy Disabled AP.
0	0	1	Healthy Disabled AP.
0	1	0	Unhealthy Enabled AP.
0	1	1	Healthy Enabled AP.
1	0	0	Invalid. The BSP can never be in the disabled state.
1	0	1	Invalid. The BSP can never be in the disabled state.
1	1	0	Unhealthy Enabled BSP.
1	1	1	Healthy Enabled BSP.

//*******************************************************
// EFI_CPU_PHYSICAL_LOCATION
//*******************************************************
typedef struct {
  UINT32  Package;
  UINT32  Core;
  UINT32  Thread;
} EFI_CPU_PHYSICAL_LOCATION;

Package: Zero-based physical package number that identifies the cartridge of the processor.

Core: Zero-based physical core number within package of the processor.

Thread: Zero-based logical thread number within core of the processor.

#define CPU_V2_EXTENDED_TOPOLOGY    BIT24
typedef union {
     EFI_CPU_PHYSICAL_LOCATION2     Location2;
} EXTENDED_PROCESSOR_INFORMATION;

Location2: The 6-level physical location of the processor, including the physical package number that identifies the cartridge, the physical module number within package, the physical tile number within the module, the physical die number within the tile, the physical core number within package, and logical thread number within core. Type EFI_CPU_PHYSICAL_LOCATION2 is defined below.

typedef struct {
  UINT32  Package;
  UINT32  Module;
  UINT32  Tile;
  UINT32  Die;
  UINT32  Core;
  UINT32  Thread;
} EFI_CPU_PHYSICAL_LOCATION2;

Package: Zero-based physical package number that identifies the cartridge of the processor.

Module: Zero-based physical module number within package of the processor.

Tile: Zero-based physical tile number within module of the processor.

Die: Zero-based physical die number within tile of the processor.

Core: Zero-based physical core number within die of the processor.

Thread: Zero-based logical thread number within core of the processor.

Status Codes Returned

Table 13.5 Status Codes Returned
EFI_SUCCESS	Processor information was returned.
EFI_DEVICE_ERROR	The calling processor is an AP.
EFI_INVALID_PARAMETER	`ProcessorInfoBuffer` is `NULL`.
EFI_NOT_FOUND	The processor with the handle specified by `ProcessorNumber` does not exist in the platform.

13.4.4. EFI_MP_SERVICES_PROTOCOL.StartupAllAPs()

Summary

This service executes a caller provided function on all enabled APs. APs can run either simultaneously or one at a time in sequence. This service supports both blocking and non-blocking requests. The non-blocking requests use EFI events so the BSP can detect when the APs have finished. See “Non-blocking Execution Support” below for details. This service may only be called from the BSP.

Prototype

typedef
EFI_STATUS
(EFIAPI *EFI_MP_SERVICES_STARTUP_ALL_APS) (
  IN EFI_MP_SERVICES_PROTOCOL  *This,
  IN EFI_AP_PROCEDURE          Procedure,
  IN BOOLEAN                   SingleThread,
  IN EFI_EVENT                 WaitEvent               OPTIONAL,
  IN UINTN                     TimeoutInMicroSeconds,
  IN VOID                      *ProcedureArgument      OPTIONAL,
  OUT UINTN                    **FailedCpuList         OPTIONAL
  );

Parameters

This: A pointer to the EFI_MP_SERVICES_PROTOCOL instance.

Procedure: A pointer to the function to be run on enabled APs of the system. Type EFI_AP_PROCEDURE is defined in the “Related Definitions” of this function, below.

SingleThread

If TRUE , then all the enabled APs execute the function specified by Procedure one by one, in ascending order of processor handle number.

If FALSE , then all the enabled APs execute the function specified by Procedure simultaneously.

WaitEvent

The event created by the caller with CreateEvent() service.

If it is NULL , then execute in blocking mode. BSP waits until all APs finish or TimeoutInMicroSeconds expires.

If it’s not NULL , then execute in non-blocking mode. BSP requests the function specified by Procedure to be started on all the enabled APs, and go on executing immediately. If all return from Procedure or TimeoutInMicroSeconds expires, this event is signaled. The BSP can use the CheckEvent() or WaitForEvent() services to check the state of event.

Type EFI_EVENT is defined in CreateEvent() in the Unified Extensible Firmware Interface Specification (Version 2.0).

TimeoutInMicroseconds

Indicates the time limit in microseconds for APs to return from Procedure , either for blocking or non-blocking mode. Zero means infinity.

If the timeout expires before all APs return from Procedure , then Procedure on the failed APs is terminated. All enabled APs are available for next function assigned by EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() or EFI_MP_SERVICES_PROTOCOL.StartupThisAP().

If the timeout expires in blocking mode, BSP returns EFI_TIMEOUT .

If the timeout expires in non-blocking mode, WaitEvent is signaled with SignalEvent() .

ProcedureArgument: The parameter passed into Procedure for all APs.

FailedCpuList

If NULL , this parameter is ignored.

Otherwise, if all APs finish successfully, then its content is set to NULL . If not all APs finish before timeout expires, then its content is set to address of the buffer holding handle numbers of the failed APs. The buffer is allocated by MP Service Protocol, and it’s the caller’s responsibility to free the buffer with FreePool() service.

In blocking mode, it is ready for consumption when the call returns. In non-blocking mode, it is ready when WaitEvent is signaled.

The list of failed CPU is terminated by END_OF_CPU_LIST . It is defined in “Related Definitions” below.

Description

This function is used to dispatch all the enabled APs to the function specified by Procedure .

If any enabled AP is busy, then EFI_NOT_READY is returned immediately and Procedure is not started on any AP.

If SingleThread is TRUE , all the enabled APs execute the function specified by Procedure one by one, in ascending order of processor handle number. Otherwise, all the enabled APs execute the function specified by Procedure simultaneously.

If WaitEvent is NULL , execution is in blocking mode. The BSP waits until all APs finish or TimeoutInMicroSecs expires. Otherwise, execution is in non-blocking mode, and the BSP returns from this service without waiting for APs.

If a non-blocking mode is requested after the UEFI Event EFI_EVENT_GROUP_READY_TO_BOOT is signaled, then EFI_UNSUPPORTED must be returned.

If the timeout specified by TimeoutInMicroseconds expires before all APs return from Procedure , then Procedure on the failed APs is terminated. All enabled APs are always available for further calls to EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() and EFI_MP_SERVICES_PROTOCOL.StartupThisAP() . If FailedCpuList is not NULL , its content points to the list of processor handle numbers in which Procedure was terminated.

This service may only be called from the BSP.

Note: It is the responsibility of the consumer of the EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() to make sure that the nature of the code that is executed on the BSP and the dispatched APs is well controlled. The MP Services Protocol does not guarantee that the Procedure function is MP-safe. Hence, the tasks that can be run in parallel are limited to certain independent tasks and well-controlled exclusive code. EFI services and protocols may not be called by APs unless otherwise specified.

#define END_OF_CPU_LIST     0xffffffff

typedef
VOID
(EFIAPI *EFI_AP_PROCEDURE) (
  IN VOID   *ProcedureArgument
);

ProcedureArgument: Pointer to the procedure’s argument

Non-Blocking Execution Support

The following usage guidelines must be followed for non-blocking execution support.

In blocking execution mode, BSP waits until all APs finish or TimeoutInMicroSeconds expires.

In non-blocking execution mode, BSP is freed to return to the caller and then proceed to the next task without having to wait for APs. The following sequence needs to occur in a non-blocking execution mode:

The caller that intends to use this MP Services Protocol in non-blocking mode creates WaitEvent by calling the EFI CreateEvent() service.

The caller invokes EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() . If the parameter WaitEvent is not NULL , then StartupAllAPs() executes in non-blocking mode. It requests the function specified by Procedure to be started on all the enabled APs, and releases the BSP to continue with other tasks.

The caller can use the CheckEvent() and WaitForEvent() services to check the state of the WaitEvent created in step 1.
When the APs complete their task or TimeoutInMicroSecondss expires, the MP Service signals WaitEvent by calling the EFI SignalEvent() function. If FailedCpuList is not NULL, its content is available when WaitEvent is signaled. If all APs returned from Procedure prior to the timeout, then FailedCpuList is set to NULL . If not all APs return from Procedure before the timeout, then FailedCpuList is filled in with the list of the failed APs. The buffer is allocated by MP Service Protocol using AllocatePool() . It is the caller’s responsibility to free the buffer with FreePool() service.
This invocation of SignalEvent() function informs the caller that invoked EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() that either all the APs completed the specified task or a timeout occurred. The contents of FailedCpuList can be examined to determine which APs did not complete the specified task prior to the timeout.

Status Codes Returned

Table 13.6 Status Codes Returned
EFI_SUCCESS	In blocking mode, all APs have finished before the timeout expired.
EFI_SUCCESS	In non blocking mode, function has been dispatched to all enabled APs.
EFI_UNSUPPORTED	A non blocking mode request was made after the UEFI event `EFI_EVENT_GROUP_READY_TO_BOOT` was signaled.
EFI_DEVICE_ERROR	Caller processor is AP.
EFI_NOT_STARTED	No enabled APs exist in the system.
EFI_NOT_READY	Any enabled APs are busy.
EFI_TIMEOUT	In blocking mode, the timeout expired before all enabled APs have finished.
EFI_INVALID_PARAMETER	`Procedure` is `NULL`.

13.4.5. EFI_MP_SERVICES_PROTOCOL.StartupThisAP()

Summary

This service lets the caller get one enabled AP to execute a caller-provided function. The caller can request the BSP to either wait for the completion of the AP or just proceed with the next task by using the EFI event mechanism. See the “Non-blocking Execution Support” section in EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() for more details. This service may only be called from the BSP.

Prototype

typedef
EFI_STATUS
(EFIAPI *EFI_MP_SERVICES_STARTUP_THIS_AP) (
  IN EFI_MP_SERVICES_PROTOCOL  *This,
  IN EFI_AP_PROCEDURE          Procedure,
  IN UINTN                     ProcessorNumber,
  IN EFI_EVENT                 WaitEvent               OPTIONAL,
  IN UINTN                     TimeoutInMicroseconds,
  IN VOID                      *ProcedureArgument      OPTIONAL,
  OUT BOOLEAN                  *Finished               OPTIONAL
  );

Parameters

This: A pointer to the EFI_MP_SERVICES_PROTOCOL instance.

Procedure: A pointer to the function to be run on the designated AP. Type EFI_AP_PROCEDURE is defined in EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() .

ProcessorNumber: The handle number of the AP. The range is from 0 to the total number of logical processors minus 1. The total number of logical processors can be retrieved by EFI_MP_SERVICES_PROTOCOL.GetNumberOfProcessors() .

WaitEvent

The event created by the caller with CreateEvent() service.

If it is NULL , then execute in blocking mode. BSP waits until this AP finishes or TimeoutInMicroSeconds expires.

If it’s not NULL , then execute in non-blocking mode. BSP requests the function specified by Procedure to be started on the AP, and go on executing immediately. If this AP finishes or TimeoutInMicroSeconds expires, this event is signaled. BSP can use the CheckEvent() and WaitForEvent() services to check the state of event.

Type EFI_EVENT is defined in CreateEvent() in the Unified Extensible Firmware Interface Specification (Version 2.0)

TimeoutInMicrosecsond

Indicates the time limit in microseconds for this AP to finish the function, either for blocking or non-blocking mode. Zero means infinity.

If the timeout expires before this AP returns from Procedure, then Procedure on the AP is terminated. The AP is available for subsequent calls to EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() and EFI_MP_SERVICES_PROTOCOL.StartupThisAP() .

If the timeout expires in blocking mode, BSP returns EFI_TIMEOUT .

If the timeout expires in non-blocking mode, WaitEvent is signaled with SignalEvent() .

ProcedureArgument: The parameter passed into Procedure on the specified AP.

Finished

If NULL , this parameter is ignored.

In blocking mode, this parameter is ignored.

In non-blocking mode, if AP returns from Procedure before the timeout expires, its content is set to TRUE. Otherwise, the value is set to FALSE . The caller can determine if the AP returned from Procedure by evaluating this value.

Description

This function is used to dispatch one enabled AP to the function specified by Procedure passing in the argument specified by ProcedureArgument .

If WaitEvent is NULL , execution is in blocking mode. The BSP waits until the AP finishes or TimeoutInMicroSecondss expires. Otherwise, execution is in non-blocking mode. BSP proceeds to the next task without waiting for the AP. If a non-blocking mode is requested after the UEFI Event EFI_EVENT_GROUP_READY_TO_BOOT is signaled, then EFI_UNSUPPORTED must be returned.

If the timeout specified by TimeoutInMicroseconds expires before the AP returns from Procedure , then execution of Procedure by the AP is terminated. The AP is available for subsequent calls to EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() and EFI_MP_SERVICES_PROTOCOL.StartupThisAP() .

This service may only be called from the BSP.

Status Codes Returned

Table 13.7 Status Codes Returned
EFI_SUCCESS	In blocking mode, specified AP finished before the timeout expires.
EFI_SUCCESS	In non-blocking mode, the function has been dispatched to specified AP.
EFI_UNSUPPORTED	A non-blocking mode request was made after the UEFI event `EFI_EVENT_GROUP_READY_TO_BOOT` was signaled.
EFI_DEVICE_ERROR	The calling processor is an AP.
EFI_TIMEOUT	In blocking mode, the timeout expired before the specified AP has finished.
EFI_NOT_READY	The specified AP is busy.
EFI_NOT_FOUND	The processor with the handle specified by `ProcessorNumber` does not exist.
EFI_INVALID_PARAMETER	`ProcessorNumber` specifies the BSP or disabled AP.
EFI_INVALID_PARAMETER	`Procedure` is `NULL`.

13.4.6. EFI_MP_SERVICES_PROTOCOL.SwitchBSP()

Summary

This service switches the requested AP to be the BSP from that point onward. This service changes the BSP for all purposes. This service may only be called from the current BSP.

Prototype

typedef
EFI_STATUS
(EFIAPI *EFI_MP_SERVICES_SWITCH_BSP) (
  IN EFI_MP_SERVICES_PROTOCOL    *This,
  IN UINTN                       ProcessorNumber,
  IN BOOLEAN                     EnableOldBSP
  );

Parameters

This A pointer to the EFI_MP_SERVICES_PROTOCOL instance.

ProcessorNumber: The handle number of AP that is to become the new BSP. The range is from 0 to the total number of logical processors minus 1. The total number of logical processors can be retrieved by EFI_MP_SERVICES_PROTOCOL.GetNumberOfProcessors().

EnableOldBSP: If TRUE, then the old BSP will be listed as an enabled AP. Otherwise, it will be disabled.

Description

This service switches the requested AP to be the BSP from that point onward. This service changes the BSP for all purposes. The new BSP can take over the execution of the old BSP and continue seamlessly from where the old one left off. This service may not be supported after the UEFI Event EFI_EVENT_GROUP_READY_TO_BOOT is signaled.

If the BSP cannot be switched prior to the return from this service, then EFI_UNSUPPORTED must be returned.

This call can only be performed by the current BSP.

Status Codes Returned

Table 13.8 Status Codes Returned
EFI_SUCCESS	BSP successfully switched.
EFI_UNSUPPORTED	Switching the BSP cannot be completed prior to this service returning.
EFI_UNSUPPORTED	Switching the BSP is not supported.
EFI_DEVICE_ERROR	The calling processor is an AP.
EFI_NOT_FOUND	The processor with the handle specified by `ProcessorNumber` does not exist.
EFI_INVALID_PARAMETER	`ProcessorNumber` specifies the current BSP or a disabled AP.
EFI_NOT_READY	The specified AP is busy.

13.4.7. EFI_MP_SERVICES_PROTOCOL.EnableDisableAP()

Summary

This service lets the caller enable or disable an AP from this point onward. This service may only be called from the BSP.

Prototype

typedef
EFI_STATUS
(EFIAPI *EFI_MP_SERVICES_ENABLEDISABLEAP) (
  IN EFI_MP_SERVICES_PROTOCOL  *This,
  IN UINTN                     ProcessorNumber,
  IN BOOLEAN                   EnableAP,
  IN UINT32                    *HealthFlag     OPTIONAL
  );

Parameters

This: A pointer to the EFI_MP_SERVICES_PROTOCOL instance.

ProcessorNumber: The handle number of AP. The range is from 0 to the total number of logical processors minus 1. The total number of logical processors can be retrieved by EFI_MP_SERVICES_PROTOCOL.GetNumberOfProcessors().

EnableAP: Specifies the new state for the processor specified by ProcessorNumber. TRUE for enabled, FALSE for disabled.

HealthFlag

If not NULL , a pointer to a value that specifies the new health status of the AP. This flag corresponds to StatusFlag defined in EFI_MP_SERVICES_PROTOCOL.GetProcessorInfo() . Only the PROCESSOR_HEALTH_STATUS_BIT is used. All other bits are ignored.

If it is NULL, this parameter is ignored.

Description

This service allows the caller enable or disable an AP from this point onward. The caller can optionally specify the health status of the AP by Health . If an AP is being disabled, then the state of the disabled AP is implementation dependent. If an AP is enabled, then the implementation must guarantee that a complete initialization sequence is performed on the AP, so the AP is in a state that is compatible with an MP operating system. This service may not be supported after the UEFI Event EFI_EVENT_GROUP_READY_TO_BOOT is signaled.

If the enable or disable AP operation cannot be completed prior to the return from this service, then EFI_UNSUPPORTED must be returned.

This service may only be called from the BSP.

Status Codes Returned

Table 13.9 Status Codes Returned
EFI_SUCCESS	The specified AP successfully enabled or disabled.
EFI_UNSUPPORTED	Enabling or disabling an AP cannot be completed prior to this service returning.
EFI_UNSUPPORTED	Enabling or disabling an AP is not supported.
EFI_DEVICE_ERROR	The calling processor is an AP.
EFI_NOT_FOUND	Processor with the handle specified by `ProcessorNumber` does not exist.
EFI_INVALID_PARAMETER	`ProcessorNumber` specifies the BSP.

13.4.8. EFI_MP_SERVICES_PROTOCOL.WhoAmI()

Summary

This return the handle number for the calling processor. This service may be called from the BSP and APs.

Prototype

typedef
EFI_STATUS
(EFIAPI *EFI_MP_SERVICES_WHOAMI) (
  IN EFI_MP_SERVICES_PROTOCOL   *This,
  OUT UINTN                     *ProcessorNumber
  );

Parameters

This: A pointer to the EFI_MP_SERVICES_PROTOCOL instance.

ProcessorNumber: Pointer to the handle number of AP. The range is from 0 to the total number of logical processors minus 1. The total number of logical processors can be retrieved by EFI_MP_SERVICES_PROTOCOL.GetNumberOfProcessors() .

Description

This service returns the processor handle number for the calling processor. The returned value is in the range from 0 to the total number of logical processors minus 1. The total number of logical processors can be retrieved with EFI_MP_SERVICES_PROTOCOL.GetNumberOfProcessors() . This service may be called from the BSP and APs. If ProcessorNumber is NULL , then EFI_INVALID_PARAMETER is returned. Otherwise, the current processors handle number is returned in ProcessorNumber , and EFI_SUCCESS is returned.

Status Codes Returned

Table 13.10 Status Codes Returned
EFI_SUCCESS	The current processor handle number was returned in `ProcessorNumber`.
EFI_INVALID_PARAMETER	`ProcessorNumber` is `NULL`.