MdePkg: Add TdxLib to wrap Tdx operations

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

TdxLib is created with functions to perform the related Tdx operation.
This includes functions for:
 - TdAcceptPages   : Accept pending private pages and initialize the pages
                     to all-0 using the TD ephemeral private key.
 - TdExtendRtmr    : Extend measurement to one of the RTMR registers.
 - TdSharedPageMask: Get the Td guest shared page mask which indicates it
                     is a Shared or Private page.
 - TdMaxVCpuNum    : Get the maximum number of virtual CPUs.
 - TdVCpuNum       : Get the number of virtual CPUs.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@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: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>

MdePkg/Library/TdxLib/TdInfo.c

@@ -0,0 +1,115 @@
+/** @file
+
+  Fetch the Tdx info.
+
+  Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Library/BaseLib.h>
+#include <Library/DebugLib.h>
+#include <IndustryStandard/Tdx.h>
+#include <Uefi/UefiBaseType.h>
+#include <Library/TdxLib.h>
+#include <Library/BaseMemoryLib.h>
+
+UINT64   mTdSharedPageMask = 0;
+UINT32   mTdMaxVCpuNum     = 0;
+UINT32   mTdVCpuNum        = 0;
+BOOLEAN  mTdDataReturned   = FALSE;
+
+/**
+  This function call TDCALL_TDINFO to get the TD_RETURN_DATA.
+  If the TDCALL is successful, populate below variables:
+   - mTdSharedPageMask
+   - mTdMaxVCpunum
+   - mTdVCpuNum
+   - mTdDataReturned
+
+  @return TRUE  The TDCALL is successful and above variables are populated.
+  @return FALSE The TDCALL is failed. Above variables are not set.
+**/
+BOOLEAN
+GetTdInfo (
+  VOID
+  )
+{
+  UINT64          Status;
+  TD_RETURN_DATA  TdReturnData;
+  UINT8           Gpaw;
+
+  Status = TdCall (TDCALL_TDINFO, 0, 0, 0, &TdReturnData);
+  if (Status == TDX_EXIT_REASON_SUCCESS) {
+    Gpaw              = (UINT8)(TdReturnData.TdInfo.Gpaw & 0x3f);
+    mTdSharedPageMask = 1ULL << (Gpaw - 1);
+    mTdMaxVCpuNum     = TdReturnData.TdInfo.MaxVcpus;
+    mTdVCpuNum        = TdReturnData.TdInfo.NumVcpus;
+    mTdDataReturned   = TRUE;
+  } else {
+    DEBUG ((DEBUG_ERROR, "Failed call TDCALL_TDINFO. %llx\n", Status));
+    mTdDataReturned = FALSE;
+  }
+
+  return mTdDataReturned;
+}
+
+/**
+  This function gets the Td guest shared page mask.
+
+  The guest indicates if a page is shared using the Guest Physical Address
+  (GPA) Shared (S) bit. If the GPA Width(GPAW) is 48, the S-bit is bit-47.
+  If the GPAW is 52, the S-bit is bit-51.
+
+  @return Shared page bit mask
+**/
+UINT64
+EFIAPI
+TdSharedPageMask (
+  VOID
+  )
+{
+  if (mTdDataReturned) {
+    return mTdSharedPageMask;
+  }
+
+  return GetTdInfo () ? mTdSharedPageMask : 0;
+}
+
+/**
+  This function gets the maximum number of Virtual CPUs that are usable for
+  Td Guest.
+
+  @return maximum Virtual CPUs number
+**/
+UINT32
+EFIAPI
+TdMaxVCpuNum (
+  VOID
+  )
+{
+  if (mTdDataReturned) {
+    return mTdMaxVCpuNum;
+  }
+
+  return GetTdInfo () ? mTdMaxVCpuNum : 0;
+}
+
+/**
+  This function gets the number of Virtual CPUs that are usable for Td
+  Guest.
+
+  @return Virtual CPUs number
+**/
+UINT32
+EFIAPI
+TdVCpuNum (
+  VOID
+  )
+{
+  if (mTdDataReturned) {
+    return mTdVCpuNum;
+  }
+
+  return GetTdInfo () ? mTdVCpuNum : 0;
+}