ArmVirtualizationPkg: clone BasePciExpressLib, cache PCIe config base

The BarExisted() function in
"MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c" raises the TPL to
TPL_HIGH_LEVEL before accessing PCI config space.

The PciExpressLib instance under "MdePkg/Library/BasePciExpressLib" --
serving the PCI config space access -- calls
PcdGet64(PcdPciExpressBaseAddress) in turn, for each such call.

The PcdGet64() function, when issued at TPL_HIGH_LEVEL, triggers an
ASSERT(). PcdGet64() is based on a protocol in this UEFI phase, and
protocol handler services are not allowed above TPL_NOTIFY (see Table 23
"TPL Restrictions" in the UEFI spec).

Clone the library, and in a new constructor, cache the PCD in a global
variable.

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

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16909 6f19259b-4bc3-4df7-8a09-765794883524

ArmPlatformPkg/ArmVirtualizationPkg/Library/BaseCachingPciExpressLib/BaseCachingPciExpressLib.inf

@@ -0,0 +1,46 @@
+## @file
+#  Instance of PCI Express Library using the 256 MB PCI Express MMIO window.
+#
+#  PCI Express Library that uses the 256 MB PCI Express MMIO window to perform
+#  PCI Configuration cycles. Layers on top of an I/O Library instance.
+#
+#  Copyright (c) 2007 - 2014, 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                      = BaseCachingPciExpressLib
+  FILE_GUID                      = 3f3ffd80-04dc-4a2b-9d25-ecca55c2e520
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = PciExpressLib|DXE_DRIVER UEFI_DRIVER UEFI_APPLICATION
+  CONSTRUCTOR                    = PciExpressLibInitialize
+
+#
+#  VALID_ARCHITECTURES           = ARM AARCH64
+#
+
+[Sources]
+  PciExpressLib.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+
+[LibraryClasses]
+  BaseLib
+  PcdLib
+  DebugLib
+  IoLib
+
+[Pcd]
+  gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress  ## CONSUMES
+