UefiCpuPkg/MpInitLib: Implementation of MpInitLibSwitchBSP()

v4:
  1. Simply the internal function SwitchBSPWorker()'s comment header
     due to it is duplicated with MpInitLibSwitchBSP().

v3:
  1. Rename MpInitLibSwitchBsp to MpInitLibSwitchBSP.

Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Giri P Mudusuru <giri.p.mudusuru@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Michael Kinney <michael.d.kinney@intel.com>

4 files changed, 218 insertions, 7 deletions

diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
index 762d76dd7a..785653be8f 100644
--- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
@@ -389,7 +389,31 @@ MpInitLibSwitchBSP (
   IN BOOLEAN                   EnableOldBSP

   )

 {

-  return EFI_UNSUPPORTED;

+  EFI_STATUS            Status;

+  BOOLEAN               OldInterruptState;

+

+  //

+  // Before send both BSP and AP to a procedure to exchange their roles,

+  // interrupt must be disabled. This is because during the exchange role

+  // process, 2 CPU may use 1 stack. If interrupt happens, the stack will

+  // be corrupted, since interrupt return address will be pushed to stack

+  // by hardware.

+  //

+  OldInterruptState = SaveAndDisableInterrupts ();

+

+  //

+  // Mask LINT0 & LINT1 for the old BSP

+  //

+  DisableLvtInterrupts ();

+

+  Status = SwitchBSPWorker (ProcessorNumber, EnableOldBSP);

+

+  //

+  // Restore interrupt state.

+  //

+  SetInterruptState (OldInterruptState);

+

+  return Status;

 }

 

 /**

diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index 5fbcb26dda..8ae08f4d5d 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -184,6 +184,26 @@ ExtractProcessorLocation (
 }

 

 /**

+  Worker function for SwitchBSP().

+

+  Worker function for SwitchBSP(), assigned to the AP which is intended

+  to become BSP.

+

+  @param[in] Buffer   Pointer to CPU MP Data

+**/

+VOID

+EFIAPI

+FutureBSPProc (

+  IN  VOID            *Buffer

+  )

+{

+  CPU_MP_DATA         *DataInHob;

+

+  DataInHob = (CPU_MP_DATA *) Buffer;

+  AsmExchangeRole (&DataInHob->APInfo, &DataInHob->BSPInfo);

+}

+

+/**

   Get the Application Processors state.

 

   @param[in]  CpuData    The pointer to CPU_AP_DATA of specified AP

@@ -646,11 +666,20 @@ ApWakeupFunction (
           // Invoke AP function here

           //

           Procedure (Parameter);

-          //

-          // Re-get the CPU APICID and Initial APICID

-          //

-          CpuMpData->CpuData[ProcessorNumber].ApicId        = GetApicId ();

-          CpuMpData->CpuData[ProcessorNumber].InitialApicId = GetInitialApicId ();

+          if (CpuMpData->SwitchBspFlag) {

+            //

+            // Re-get the processor number due to BSP/AP maybe exchange in AP function

+            //

+            GetProcessorNumber (CpuMpData, &ProcessorNumber);

+            CpuMpData->CpuData[ProcessorNumber].ApFunction = 0;

+            CpuMpData->CpuData[ProcessorNumber].ApFunctionArgument = 0;

+          } else {

+            //

+            // Re-get the CPU APICID and Initial APICID

+            //

+            CpuMpData->CpuData[ProcessorNumber].ApicId        = GetApicId ();

+            CpuMpData->CpuData[ProcessorNumber].InitialApicId = GetInitialApicId ();

+          }

         }

         SetApState (&CpuMpData->CpuData[ProcessorNumber], CpuStateFinished);

       }

@@ -941,6 +970,7 @@ MpInitLibInitialize (
   CpuMpData->CpuCount         = 1;

   CpuMpData->BspNumber        = 0;

   CpuMpData->WaitEvent        = NULL;

+  CpuMpData->SwitchBspFlag    = FALSE;

   CpuMpData->CpuData          = (CPU_AP_DATA *) (CpuMpData + 1);

   CpuMpData->CpuInfoInHob     = (UINT64) (UINTN) (CpuMpData->CpuData + MaxLogicalProcessorNumber);

   InitializeSpinLock(&CpuMpData->MpLock);

@@ -1103,6 +1133,110 @@ MpInitLibGetProcessorInfo (
   return EFI_SUCCESS;

 }

 

+/**

+  Worker function to switch the requested AP to be the BSP from that point onward.

+

+  @param[in] ProcessorNumber   The handle number of AP that is to become the new BSP.

+  @param[in] EnableOldBSP      If TRUE, then the old BSP will be listed as an

+                               enabled AP. Otherwise, it will be disabled.

+

+  @retval EFI_SUCCESS          BSP successfully switched.

+  @retval others               Failed to switch BSP. 

+

+**/

+EFI_STATUS

+SwitchBSPWorker (

+  IN UINTN                     ProcessorNumber,

+  IN BOOLEAN                   EnableOldBSP

+  )

+{

+  CPU_MP_DATA                  *CpuMpData;

+  UINTN                        CallerNumber;

+  CPU_STATE                    State;

+  MSR_IA32_APIC_BASE_REGISTER  ApicBaseMsr;

+

+  CpuMpData = GetCpuMpData ();

+

+  //

+  // Check whether caller processor is BSP

+  //

+  MpInitLibWhoAmI (&CallerNumber);

+  if (CallerNumber != CpuMpData->BspNumber) {

+    return EFI_SUCCESS;

+  }

+

+  if (ProcessorNumber >= CpuMpData->CpuCount) {

+    return EFI_NOT_FOUND;

+  }

+

+  //

+  // Check whether specified AP is disabled

+  //

+  State = GetApState (&CpuMpData->CpuData[ProcessorNumber]);

+  if (State == CpuStateDisabled) {

+    return EFI_INVALID_PARAMETER;

+  }

+

+  //

+  // Check whether ProcessorNumber specifies the current BSP

+  //

+  if (ProcessorNumber == CpuMpData->BspNumber) {

+    return EFI_INVALID_PARAMETER;

+  }

+

+  //

+  // Check whether specified AP is busy

+  //

+  if (State == CpuStateBusy) {

+    return EFI_NOT_READY;

+  }

+

+  CpuMpData->BSPInfo.State = CPU_SWITCH_STATE_IDLE;

+  CpuMpData->APInfo.State  = CPU_SWITCH_STATE_IDLE;

+  CpuMpData->SwitchBspFlag = TRUE;

+

+  //

+  // Clear the BSP bit of MSR_IA32_APIC_BASE

+  //

+  ApicBaseMsr.Uint64 = AsmReadMsr64 (MSR_IA32_APIC_BASE);

+  ApicBaseMsr.Bits.BSP = 0;

+  AsmWriteMsr64 (MSR_IA32_APIC_BASE, ApicBaseMsr.Uint64);

+

+  //

+  // Need to wakeUp AP (future BSP).

+  //

+  WakeUpAP (CpuMpData, FALSE, ProcessorNumber, FutureBSPProc, CpuMpData);

+

+  AsmExchangeRole (&CpuMpData->BSPInfo, &CpuMpData->APInfo);

+

+  //

+  // Set the BSP bit of MSR_IA32_APIC_BASE on new BSP

+  //

+  ApicBaseMsr.Uint64 = AsmReadMsr64 (MSR_IA32_APIC_BASE);

+  ApicBaseMsr.Bits.BSP = 1;

+  AsmWriteMsr64 (MSR_IA32_APIC_BASE, ApicBaseMsr.Uint64);

+

+  //

+  // Wait for old BSP finished AP task

+  //

+  while (GetApState (&CpuMpData->CpuData[CallerNumber]) != CpuStateFinished) {

+    CpuPause ();

+  }

+

+  CpuMpData->SwitchBspFlag = FALSE;

+  //

+  // Set old BSP enable state

+  //

+  if (!EnableOldBSP) {

+    SetApState (&CpuMpData->CpuData[CallerNumber], CpuStateDisabled);

+  }

+  //

+  // Save new BSP number

+  //

+  CpuMpData->BspNumber = (UINT32) ProcessorNumber;

+

+  return EFI_SUCCESS;

+}

 

 /**

   This return the handle number for the calling processor.  This service may be

diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.h b/UefiCpuPkg/Library/MpInitLib/MpLib.h
index 84e09702b9..bfc7fb72e0 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.h
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.h
@@ -43,6 +43,23 @@
   }

 

 //

+//  The MP data for switch BSP

+//

+#define CPU_SWITCH_STATE_IDLE   0

+#define CPU_SWITCH_STATE_STORED 1

+#define CPU_SWITCH_STATE_LOADED 2

+

+//

+// CPU exchange information for switch BSP

+//

+typedef struct {

+  UINT8             State;        // offset 0

+  UINTN             StackPointer; // offset 4 / 8

+  IA32_DESCRIPTOR   Gdtr;         // offset 8 / 16

+  IA32_DESCRIPTOR   Idtr;         // offset 14 / 26

+} CPU_EXCHANGE_ROLE_INFO;

+

+//

 // AP loop state when APs are in idle state

 // It's value is the same with PcdCpuApLoopMode

 //

@@ -198,6 +215,9 @@ struct _CPU_MP_DATA {
 

   AP_INIT_STATE                  InitFlag;

   BOOLEAN                        X2ApicEnable;

+  BOOLEAN                        SwitchBspFlag;

+  CPU_EXCHANGE_ROLE_INFO         BSPInfo;

+  CPU_EXCHANGE_ROLE_INFO         APInfo;

   MTRR_SETTINGS                  MtrrTable;

   UINT8                          ApLoopMode;

   UINT8                          ApTargetCState;

@@ -243,6 +263,22 @@ AsmGetAddressMap (
   );

 

 /**

+  This function is called by both the BSP and the AP which is to become the BSP to

+  Exchange execution context including stack between them. After return from this

+  function, the BSP becomes AP and the AP becomes the BSP.

+

+  @param[in] MyInfo      Pointer to buffer holding the exchanging information for the executing processor.

+  @param[in] OthersInfo  Pointer to buffer holding the exchanging information for the peer.

+

+**/

+VOID

+EFIAPI

+AsmExchangeRole (

+  IN CPU_EXCHANGE_ROLE_INFO    *MyInfo,

+  IN CPU_EXCHANGE_ROLE_INFO    *OthersInfo

+  );

+

+/**

   Get the pointer to CPU MP Data structure.

 

   @return  The pointer to CPU MP Data structure.

@@ -312,6 +348,23 @@ InitMpGlobalData (
   );

 

 /**

+  Worker function to switch the requested AP to be the BSP from that point onward.

+

+  @param[in] ProcessorNumber   The handle number of AP that is to become the new BSP.

+  @param[in] EnableOldBSP      If TRUE, then the old BSP will be listed as an

+                               enabled AP. Otherwise, it will be disabled.

+

+  @retval EFI_SUCCESS          BSP successfully switched.

+  @retval others               Failed to switch BSP. 

+

+**/

+EFI_STATUS

+SwitchBSPWorker (

+  IN UINTN                     ProcessorNumber,

+  IN BOOLEAN                   EnableOldBSP

+  );

+

+/**

   Get pointer to CPU MP Data structure from GUIDed HOB.

 

   @return  The pointer to CPU MP Data structure.

diff --git a/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c b/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c
index a7e1cdeac1..cdec0108c5 100644
--- a/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c
@@ -563,7 +563,7 @@ MpInitLibSwitchBSP (
   IN  BOOLEAN                  EnableOldBSP

   )

 {

-  return EFI_UNSUPPORTED;

+  return SwitchBSPWorker (ProcessorNumber, EnableOldBSP);

 }

 

 /**