OvmfPkg: Update PlatformPei to support Tdx guest

RFC: https://bugzilla.tianocore.org/show_bug.cgi?id=3429

OvmfPkg/PlatformPei is updated to support Tdx guest. There are below
major changes.
 - Set Tdx related PCDs
 - Publish Tdx RamRegions

In this patch there is another new function BuildPlatformInfoHob ().
This function builds EFI_HOB_PLATFORM_INFO which contains the
HostBridgeDevId. The hob is built in both Td guest and Non-Td guest.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>

OvmfPkg/PlatformPei/IntelTdx.c

@@ -0,0 +1,51 @@
+/** @file
+  Initialize Intel TDX support.
+
+  Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <PiPei.h>
+#include <Library/BaseLib.h>
+#include <Library/DebugLib.h>
+#include <Library/HobLib.h>
+#include <Library/BaseMemoryLib.h>
+#include <Library/MemoryAllocationLib.h>
+#include <IndustryStandard/Tdx.h>
+#include <IndustryStandard/QemuFwCfg.h>
+#include <Library/QemuFwCfgLib.h>
+#include <Library/PeiServicesLib.h>
+#include <Library/TdxLib.h>
+#include <Library/PlatformInitLib.h>
+#include <WorkArea.h>
+#include <ConfidentialComputingGuestAttr.h>
+#include "Platform.h"
+
+/**
+  This Function checks if TDX is available, if present then it sets
+  the dynamic PCDs for Tdx guest.
+  **/
+VOID
+IntelTdxInitialize (
+  VOID
+  )
+{
+ #ifdef MDE_CPU_X64
+  RETURN_STATUS  PcdStatus;
+
+  if (!TdIsEnabled ()) {
+    return;
+  }
+
+  PcdStatus = PcdSet64S (PcdConfidentialComputingGuestAttr, CCAttrIntelTdx);
+  ASSERT_RETURN_ERROR (PcdStatus);
+
+  PcdStatus = PcdSet64S (PcdTdxSharedBitMask, TdSharedPageMask ());
+  ASSERT_RETURN_ERROR (PcdStatus);
+
+  PcdStatus = PcdSetBoolS (PcdSetNxForStack, TRUE);
+  ASSERT_RETURN_ERROR (PcdStatus);
+ #endif
+}