UefiCpuPkg/CpuDxe: Put APs in wait for SIPI state at ExitBootServices

when gBS->ExitBootServices() is called, the APs should avoid to access
the unsafed buff datas which were allocated by boot services.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
Tested-by: Gabriel Somlo <somlo@cmu.edu>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16397 6f19259b-4bc3-4df7-8a09-765794883524

UefiCpuPkg/CpuDxe/CpuMp.c

@@ -21,6 +21,7 @@ UINTN gPollInterval = 100; // 100 microseconds
 
 MP_SYSTEM_DATA mMpSystemData;
 EFI_HANDLE     mMpServiceHandle       = NULL;
+EFI_EVENT      mExitBootServicesEvent = (EFI_EVENT)NULL;
 
 VOID *mCommonStack = 0;
 VOID *mTopOfApCommonStack = 0;
@@ -1464,6 +1465,28 @@ InitMpSystemData (
   return EFI_SUCCESS;
 }
 
+/**
+  Callback function for ExitBootServices.
+
+  @param  Event                 Event whose notification function is being invoked.
+  @param  Context               The pointer to the notification function's context,
+                                which is implementation-dependent.
+
+**/
+VOID
+EFIAPI
+ExitBootServicesCallback (
+  IN EFI_EVENT                Event,
+  IN VOID                     *Context
+  )
+{
+  //
+  // Avoid APs access invalid buff datas which allocated by BootServices,
+  // so we send INIT IPI to APs to let them wait for SIPI state.
+  //
+  SendInitIpiAllExcludingSelf ();
+}
+
 /**
   Initialize Multi-processor support.
 
@@ -1531,4 +1554,13 @@ InitializeMpSupport (
                                 (gMaxLogicalProcessorNumber - mMpSystemData.NumberOfProcessors) *
                                 gApStackSize));
   }
+
+  Status = gBS->CreateEvent (
+                  EVT_SIGNAL_EXIT_BOOT_SERVICES,
+                  TPL_CALLBACK,
+                  ExitBootServicesCallback,
+                  NULL,
+                  &mExitBootServicesEvent
+                  );
+  ASSERT_EFI_ERROR (Status);
 }