OvmfPkg/XenAcpiPlatformDxe: create from AcpiPlatformDxe

Create an almost verbatim copy of the
"OvmfPkg/AcpiPlatformDxe/AcpiPlatformDxe.inf" driver for the OvmfXen
platform. We're going to trim the driver in subsequent patches.
Ultimately, the XenAcpiPlatformDxe driver will duplicate a negligible
amount of code that is currently present in the QemuFwCfgAcpiPlatformDxe
driver.

List the new driver in "Maintainers.txt", in the "OvmfPkg: Xen-related
modules" section.

Switch the OvmfXen platform to the new driver at once.

This patch should be reviewed with "git show --find-copies-harder".

Cc: Andrew Fish <afish@apple.com>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Julien Grall <julien@xen.org>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2122
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20210526201446.12554-12-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Leif Lindholm <leif@nuviainc.com>

OvmfPkg/XenAcpiPlatformDxe/EntryPoint.c

@@ -0,0 +1,95 @@
+/** @file
+  Entry point of OVMF ACPI Platform Driver for Xen guests
+
+  Copyright (C) 2015-2021, Red Hat, Inc.
+  Copyright (c) 2008 - 2015, Intel Corporation. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#include <Guid/RootBridgesConnectedEventGroup.h> // gRootBridgesConnectedEve...
+#include <Library/DebugLib.h>                    // DEBUG()
+#include <Library/PcdLib.h>                      // PcdGetBool()
+#include <Library/UefiBootServicesTableLib.h>    // gBS
+#include <Protocol/AcpiTable.h>                  // EFI_ACPI_TABLE_PROTOCOL
+
+#include "AcpiPlatform.h"
+
+STATIC
+EFI_ACPI_TABLE_PROTOCOL *
+FindAcpiTableProtocol (
+  VOID
+  )
+{
+  EFI_STATUS              Status;
+  EFI_ACPI_TABLE_PROTOCOL *AcpiTable;
+
+  Status = gBS->LocateProtocol (
+                  &gEfiAcpiTableProtocolGuid,
+                  NULL,
+                  (VOID**)&AcpiTable
+                  );
+  ASSERT_EFI_ERROR (Status);
+  return AcpiTable;
+}
+
+
+STATIC
+VOID
+EFIAPI
+OnRootBridgesConnected (
+  IN EFI_EVENT Event,
+  IN VOID      *Context
+  )
+{
+  EFI_STATUS Status;
+
+  DEBUG ((DEBUG_INFO,
+    "%a: root bridges have been connected, installing ACPI tables\n",
+    __FUNCTION__));
+  Status = InstallAcpiTables (FindAcpiTableProtocol ());
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "%a: InstallAcpiTables: %r\n", __FUNCTION__, Status));
+  }
+  gBS->CloseEvent (Event);
+}
+
+
+EFI_STATUS
+EFIAPI
+AcpiPlatformEntryPoint (
+  IN EFI_HANDLE         ImageHandle,
+  IN EFI_SYSTEM_TABLE   *SystemTable
+  )
+{
+  EFI_STATUS Status;
+  EFI_EVENT  RootBridgesConnected;
+
+  //
+  // If the platform doesn't support PCI, or PCI enumeration has been disabled,
+  // install the tables at once, and let the entry point's return code reflect
+  // the full functionality.
+  //
+  if (PcdGetBool (PcdPciDisableBusEnumeration)) {
+    DEBUG ((DEBUG_INFO, "%a: PCI or its enumeration disabled, installing "
+      "ACPI tables\n", __FUNCTION__));
+    return InstallAcpiTables (FindAcpiTableProtocol ());
+  }
+
+  //
+  // Otherwise, delay installing the ACPI tables until root bridges are
+  // connected. The entry point's return status will only reflect the callback
+  // setup. (Note that we're a DXE_DRIVER; our entry point function is invoked
+  // strictly before BDS is entered and can connect the root bridges.)
+  //
+  Status = gBS->CreateEventEx (EVT_NOTIFY_SIGNAL, TPL_CALLBACK,
+                  OnRootBridgesConnected, NULL /* Context */,
+                  &gRootBridgesConnectedEventGroupGuid, &RootBridgesConnected);
+  if (!EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_INFO,
+      "%a: waiting for root bridges to be connected, registered callback\n",
+      __FUNCTION__));
+  }
+
+  return Status;
+}