Ovmfpkg/CcExitLib: Provide SVSM discovery support

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4654

The SVSM specification documents an alternative method of discovery for
the SVSM using a reserved CPUID bit and a reserved MSR.

For the CPUID support, the #VC handler of an SEV-SNP guest should modify
the returned value in the EAX register for the 0x8000001f CPUID function
by setting bit 28 when an SVSM is present.

For the MSR support, new reserved MSR 0xc001f000 has been defined. A #VC
should be generated when accessing this MSR. The #VC handler is expected
to ignore writes to this MSR and return the physical calling area address
(CAA) on reads of this MSR.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Min Xu <min.m.xu@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>

OvmfPkg/Library/CcExitLib/CcExitLib.inf

@@ -1,7 +1,7 @@
 ## @file
 #  CcExitLib Library.
 #
-#  Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
+#  Copyright (C) 2020 - 2024, Advanced Micro Devices, Inc. All rights reserved.<BR>
 #  Copyright (C) 2020 - 2022, Intel Corporation. All rights reserved.<BR>
 #  SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -41,6 +41,7 @@
   DebugLib
   LocalApicLib
   MemEncryptSevLib
+  AmdSvsmLib
 
 [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidBase