Revert "ArmVirtPkg/FdtClientDxe: install DT configuration table at ReadyToBoot"

This reverts commit 18f6d4df9e.

We realized that DXE drivers that are independent of AcpiPlatformDxe (that
is, independent of QEMU's ACPI generation), such as RamDiskDxe and
BootGraphicsResourceTableDxe, may produce and/or manipulate ACPI tables,
at driver dispatch or even at Ready To Boot.

This makes it unsafe for us to check for ACPI presence in the UEFI system
config table in a Ready To Boot callback, in order to decide about
exposing the DT.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

ArmVirtPkg/FdtClientDxe/FdtClientDxe.c

@@ -20,7 +20,6 @@
 #include <Library/HobLib.h>
 #include <libfdt.h>
 
-#include <Guid/EventGroup.h>
 #include <Guid/Fdt.h>
 #include <Guid/FdtHob.h>
 
@@ -307,30 +306,6 @@ STATIC FDT_CLIENT_PROTOCOL mFdtClientProtocol = {
   GetOrInsertChosenNode,
 };
 
-STATIC
-VOID
-EFIAPI
-OnReadyToBoot (
-  EFI_EVENT       Event,
-  VOID            *Context
-  )
-{
-  EFI_STATUS      Status;
-
-  if (!FeaturePcdGet (PcdPureAcpiBoot)) {
-    //
-    // Only install the FDT as a configuration table if we want to leave it up
-    // to the OS to decide whether it prefers ACPI over DT.
-    //
-    Status = gBS->InstallConfigurationTable (&gFdtTableGuid, mDeviceTreeBase);
-    ASSERT_EFI_ERROR (Status);
-  }
-
-  gBS->CloseEvent (Event);
-}
-
-STATIC EFI_EVENT         mReadyToBootEvent;
-
 EFI_STATUS
 EFIAPI
 InitializeFdtClientDxe (
@@ -358,21 +333,15 @@ InitializeFdtClientDxe (
 
   DEBUG ((EFI_D_INFO, "%a: DTB @ 0x%p\n", __FUNCTION__, mDeviceTreeBase));
 
-  Status = gBS->InstallProtocolInterface (&ImageHandle, &gFdtClientProtocolGuid,
+  if (!FeaturePcdGet (PcdPureAcpiBoot)) {
-                  EFI_NATIVE_INTERFACE, &mFdtClientProtocol);
+    //
-  if (EFI_ERROR (Status)) {
+    // Only install the FDT as a configuration table if we want to leave it up
-    return Status;
+    // to the OS to decide whether it prefers ACPI over DT.
-  }
+    //
-
+    Status = gBS->InstallConfigurationTable (&gFdtTableGuid, DeviceTreeBase);
-  Status = gBS->CreateEventEx (
-                  EVT_NOTIFY_SIGNAL,
-                  TPL_CALLBACK,
-                  OnReadyToBoot,
-                  NULL,
-                  &gEfiEventReadyToBootGuid,
-                  &mReadyToBootEvent
-                  );
     ASSERT_EFI_ERROR (Status);
-
+  }
-  return EFI_SUCCESS;
+
+  return gBS->InstallProtocolInterface (&ImageHandle, &gFdtClientProtocolGuid,
+                EFI_NATIVE_INTERFACE, &mFdtClientProtocol);
 }

ArmVirtPkg/FdtClientDxe/FdtClientDxe.inf

@@ -42,7 +42,6 @@
   gFdtClientProtocolGuid                  ## PRODUCES
 
 [Guids]
-  gEfiEventReadyToBootGuid
   gFdtHobGuid
   gFdtTableGuid