UefiCpuPkg: Implement library support for VMGEXIT

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

To support handling #VC exceptions and issuing VMGEXIT instructions,
create a library with functions that can be used to perform these
#VC/VMGEXIT related operations. This includes functions for:
  - Handling #VC exceptions
  - Preparing for and issuing a VMGEXIT
  - Performing MMIO-related write operations to support flash emulation
  - Performing AP related boot opeations

The base functions in this driver will not do anything and will return
an error if a return value is required. It is expected that other packages
(like OvmfPkg) will create a version of the library to fully support an
SEV-ES guest.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>

UefiCpuPkg/Library/VmgExitLibNull/VmgExitLibNull.c

@@ -0,0 +1,121 @@
+/** @file
+  VMGEXIT Base Support Library.
+
+  Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Base.h>
+#include <Uefi.h>
+#include <Library/VmgExitLib.h>
+
+/**
+  Perform VMGEXIT.
+
+  Sets the necessary fields of the GHCB, invokes the VMGEXIT instruction and
+  then handles the return actions.
+
+  The base library function returns an error in the form of a
+  GHCB_EVENT_INJECTION representing a GP_EXCEPTION.
+
+  @param[in, out]  Ghcb       A pointer to the GHCB
+  @param[in]       ExitCode   VMGEXIT code to be assigned to the SwExitCode
+                              field of the GHCB.
+  @param[in]       ExitInfo1  VMGEXIT information to be assigned to the
+                              SwExitInfo1 field of the GHCB.
+  @param[in]       ExitInfo2  VMGEXIT information to be assigned to the
+                              SwExitInfo2 field of the GHCB.
+
+  @retval  0                  VMGEXIT succeeded.
+  @return                     Exception number to be propagated, VMGEXIT
+                              processing did not succeed.
+
+**/
+UINT64
+EFIAPI
+VmgExit (
+  IN OUT GHCB                *Ghcb,
+  IN     UINT64              ExitCode,
+  IN     UINT64              ExitInfo1,
+  IN     UINT64              ExitInfo2
+  )
+{
+  GHCB_EVENT_INJECTION  Event;
+
+  Event.Uint64 = 0;
+  Event.Elements.Vector = GP_EXCEPTION;
+  Event.Elements.Type   = GHCB_EVENT_INJECTION_TYPE_EXCEPTION;
+  Event.Elements.Valid  = 1;
+
+  return Event.Uint64;
+}
+
+/**
+  Perform pre-VMGEXIT initialization/preparation.
+
+  Performs the necessary steps in preparation for invoking VMGEXIT. Must be
+  called before setting any fields within the GHCB.
+
+  The base library function does nothing.
+
+  @param[in, out]  Ghcb       A pointer to the GHCB
+
+**/
+VOID
+EFIAPI
+VmgInit (
+  IN OUT GHCB                *Ghcb
+  )
+{
+}
+
+/**
+  Perform post-VMGEXIT cleanup.
+
+  Performs the necessary steps to cleanup after invoking VMGEXIT. Must be
+  called after obtaining needed fields within the GHCB.
+
+  The base library function does nothing.
+
+  @param[in, out]  Ghcb       A pointer to the GHCB
+
+**/
+VOID
+EFIAPI
+VmgDone (
+  IN OUT GHCB                *Ghcb
+  )
+{
+}
+
+/**
+  Handle a #VC exception.
+
+  Performs the necessary processing to handle a #VC exception.
+
+  The base library function returns an error equal to VC_EXCEPTION,
+  to be propagated to the standard exception handling stack.
+
+  @param[in, out]  ExceptionType  Pointer to an EFI_EXCEPTION_TYPE to be set
+                                  as value to use on error.
+  @param[in, out]  SystemContext  Pointer to EFI_SYSTEM_CONTEXT
+
+  @retval  EFI_SUCCESS            Exception handled
+  @retval  EFI_UNSUPPORTED        #VC not supported, (new) exception value to
+                                  propagate provided
+  @retval  EFI_PROTOCOL_ERROR     #VC handling failed, (new) exception value to
+                                  propagate provided
+
+**/
+EFI_STATUS
+EFIAPI
+VmgExitHandleVc (
+  IN OUT EFI_EXCEPTION_TYPE  *ExceptionType,
+  IN OUT EFI_SYSTEM_CONTEXT  SystemContext
+  )
+{
+  *ExceptionType = VC_EXCEPTION;
+
+  return EFI_UNSUPPORTED;
+}

UefiCpuPkg/Library/VmgExitLibNull/VmgExitLibNull.inf

@@ -0,0 +1,27 @@
+## @file
+#  VMGEXIT Support Library.
+#
+#  Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = VmgExitLibNull
+  MODULE_UNI_FILE                = VmgExitLibNull.uni
+  FILE_GUID                      = 3cd7368f-ef9b-4a9b-9571-2ed93813677e
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = VmgExitLib
+
+[Sources.common]
+  VmgExitLibNull.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  UefiCpuPkg/UefiCpuPkg.dec
+
+[LibraryClasses]
+  BaseLib
+

UefiCpuPkg/Library/VmgExitLibNull/VmgExitLibNull.uni

@@ -0,0 +1,15 @@
+// /** @file
+// VMGEXIT support library instance.
+//
+// VMGEXIT support library instance.
+//
+// Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
+// SPDX-License-Identifier: BSD-2-Clause-Patent
+//
+// **/
+
+
+#string STR_MODULE_ABSTRACT             #language en-US "VMGEXIT support NULL library instance"
+
+#string STR_MODULE_DESCRIPTION          #language en-US "VMGEXIT support NULL library instance."
+