ArmVirtualizationPkg: introduce QemuFwCfgLib instance for DXE drivers

After reviewing OvmfPkg's use of its own QemuFwCfgLib instances, it is
clear that its only pre-DXE fw_cfg dependency concerns S3 support (the
QemuFwCfgS3Enabled() call in "PlatformPei/Platform.c").

For ARM guests, S3 is in the distant future, but we can see several
shorter term applications for fw_cfg that all reside in DXE:
- controlling boot order (to be implemented in PlatformBdsLib for Intel
  BDS),
- supporting -kernel / -initrd / -append boot on QEMU (to be implemented
  in PlatformBdsLib for Intel BDS, similarly),
- loading and linking ACPI tables,
- installing SMBIOS tables.

Therefore it makes sense to add a simple MMIO-based fw_cfg client library
to ArmVirtualizationPkg that for the moment is only available to
DXE_DRIVER modules.

Because MMIO accesses are costly on KVM/ARM, InternalQemuFwCfgReadBytes()
accesses the fw_cfg data register in full words. This speeds up transfers
almost linearly.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16567 6f19259b-4bc3-4df7-8a09-765794883524

ArmPlatformPkg/ArmVirtualizationPkg/Library/QemuFwCfgLib/QemuFwCfgLib.inf

@@ -0,0 +1,52 @@
+## @file
+#
+#  Stateful, implicitly initialized fw_cfg library.
+#
+#  Copyright (C) 2013 - 2014, Red Hat, Inc.
+#  Copyright (c) 2008 - 2012, Intel Corporation. All rights reserved.<BR>
+#
+#  This program and the accompanying materials are licensed and made available
+#  under the terms and conditions of the BSD License which accompanies this
+#  distribution. The full text of the license may be found at
+#  http://opensource.org/licenses/bsd-license.php
+#
+#  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR
+#  IMPLIED.
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = QemuFwCfgLib
+  FILE_GUID                      = B271F41F-B841-48A9-BA8D-545B4BC2E2BF
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = QemuFwCfgLib|DXE_DRIVER
+
+  CONSTRUCTOR                    = QemuFwCfgInitialize
+
+#
+# The following information is for reference only and not required by the build
+# tools.
+#
+#  VALID_ARCHITECTURES           = ARM AARCH64
+#
+
+[Sources]
+  QemuFwCfgLib.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  OvmfPkg/OvmfPkg.dec
+  ArmPlatformPkg/ArmVirtualizationPkg/ArmVirtualizationPkg.dec
+
+[LibraryClasses]
+  BaseLib
+  BaseMemoryLib
+  IoLib
+  PcdLib
+
+[Pcd]
+  gArmVirtualizationTokenSpaceGuid.PcdFwCfgSelectorAddress
+  gArmVirtualizationTokenSpaceGuid.PcdFwCfgDataAddress