4 files changed, 86 insertions, 0 deletions
diff --git a/MdePkg/Include/Library/BaseLib.h b/MdePkg/Include/Library/BaseLib.h
index 7edf005..04fb329 100644
--- a/MdePkg/Include/Library/BaseLib.h
+++ b/MdePkg/Include/Library/BaseLib.h
@@ -7849,6 +7849,20 @@ AsmXGetBv (
 
 
 /**
+  Executes a VMGEXIT instruction (VMMCALL with a REP prefix)
+
+  Executes a VMGEXIT instruction. This function is only available on IA-32 and
+  x64.
+
+**/
+VOID
+EFIAPI
+AsmVmgExit (
+  VOID
+  );
+
+
+/**
   Patch the immediate operand of an IA32 or X64 instruction such that the byte,
   word, dword or qword operand is encoded at the end of the instruction's
   binary representation.
diff --git a/MdePkg/Library/BaseLib/BaseLib.inf b/MdePkg/Library/BaseLib/BaseLib.inf
index 3b93b5d..3b85c56 100644
--- a/MdePkg/Library/BaseLib/BaseLib.inf
+++ b/MdePkg/Library/BaseLib/BaseLib.inf
@@ -184,6 +184,7 @@
   Ia32/DisableCache.nasm| GCC
   Ia32/RdRand.nasm
   Ia32/XGetBv.nasm
+  Ia32/VmgExit.nasm
 
   Ia32/DivS64x64Remainder.c
   Ia32/InternalSwitchStack.c | MSFT
@@ -317,6 +318,7 @@
   X64/DisablePaging64.nasm
   X64/RdRand.nasm
   X64/XGetBv.nasm
+  X64/VmgExit.nasm
   ChkStkGcc.c  | GCC
 
 [Sources.EBC]
diff --git a/MdePkg/Library/BaseLib/Ia32/VmgExit.nasm b/MdePkg/Library/BaseLib/Ia32/VmgExit.nasm
new file mode 100644
index 0000000..69f7fbf
--- /dev/null
+++ b/MdePkg/Library/BaseLib/Ia32/VmgExit.nasm
@@ -0,0 +1,38 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
+; SPDX-License-Identifier: BSD-2-Clause-Patent
+;
+; Module Name:
+;
+;   VmgExit.Asm
+;
+; Abstract:
+;
+;   AsmVmgExit function
+;
+; Notes:
+;
+;------------------------------------------------------------------------------
+
+    SECTION .text
+
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; AsmVmgExit (
+;   VOID
+;   );
+;------------------------------------------------------------------------------
+global ASM_PFX(AsmVmgExit)
+ASM_PFX(AsmVmgExit):
+;
+; NASM doesn't support the vmmcall instruction in 32-bit mode and NASM versions
+; before 2.12 cannot translate the 64-bit "rep vmmcall" instruction into elf32
+; format. Given that VMGEXIT does not make sense on IA32, provide a stub
+; implementation that is identical to CpuBreakpoint(). In practice, AsmVmgExit()
+; should never be called on IA32.
+;
+    int  3
+    ret
+
diff --git a/MdePkg/Library/BaseLib/X64/VmgExit.nasm b/MdePkg/Library/BaseLib/X64/VmgExit.nasm
new file mode 100644
index 0000000..26f0345
--- /dev/null
+++ b/MdePkg/Library/BaseLib/X64/VmgExit.nasm
@@ -0,0 +1,32 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
+; SPDX-License-Identifier: BSD-2-Clause-Patent
+;
+; Module Name:
+;
+;   VmgExit.Asm
+;
+; Abstract:
+;
+;   AsmVmgExit function
+;
+; Notes:
+;
+;------------------------------------------------------------------------------
+
+    DEFAULT REL
+    SECTION .text
+
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; AsmVmgExit (
+;   VOID
+;   );
+;------------------------------------------------------------------------------
+global ASM_PFX(AsmVmgExit)
+ASM_PFX(AsmVmgExit):
+    rep     vmmcall
+    ret
+