From: Tom Lendacky <thomas.lendacky@amd.com>

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

VMGEXIT is a new instruction used for Hypervisor/Guest communication when
running as an SEV-ES guest. A VMGEXIT will cause an automatic exit (AE)
to occur, resulting in a #VMEXIT with an exit code value of 0x403.

Provide the necessary support to execute the VMGEXIT instruction, which
is "rep; vmmcall".

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 MdePkg/Library/BaseLib/BaseLib.inf       |  2 ++
 MdePkg/Include/Library/BaseLib.h         | 14 +++++++++
 MdePkg/Library/BaseLib/Ia32/GccInline.c  | 17 +++++++++++
 MdePkg/Library/BaseLib/X64/GccInline.c   | 17 +++++++++++
 MdePkg/Library/BaseLib/Ia32/VmgExit.nasm | 37 ++++++++++++++++++++++++
 MdePkg/Library/BaseLib/X64/VmgExit.nasm  | 32 ++++++++++++++++++++
 6 files changed, 119 insertions(+)
 create mode 100644 MdePkg/Library/BaseLib/Ia32/VmgExit.nasm
 create mode 100644 MdePkg/Library/BaseLib/X64/VmgExit.nasm

diff --git a/MdePkg/Library/BaseLib/BaseLib.inf b/MdePkg/Library/BaseLib/BaseLib.inf
index e26c0d8cb0ac..1bcc90d5a4c9 100644
--- a/MdePkg/Library/BaseLib/BaseLib.inf
+++ b/MdePkg/Library/BaseLib/BaseLib.inf
@@ -154,6 +154,7 @@ [Sources.Ia32]
   Ia32/EnableCache.c | MSFT
   Ia32/DisableCache.c | MSFT
   Ia32/XGetBv.nasm | MSFT
+  Ia32/VmgExit.nasm | MSFT
 
 
   Ia32/GccInline.c | GCC
@@ -290,6 +291,7 @@ [Sources.X64]
   X64/ReadCr0.nasm| MSFT
   X64/ReadEflags.nasm| MSFT
   X64/XGetBv.nasm | MSFT
+  X64/VmgExit.nasm | MSFT
 
 
   X64/Non-existing.c
diff --git a/MdePkg/Include/Library/BaseLib.h b/MdePkg/Include/Library/BaseLib.h
index 7edf0051a0a0..04fb329eaabb 100644
--- a/MdePkg/Include/Library/BaseLib.h
+++ b/MdePkg/Include/Library/BaseLib.h
@@ -7848,6 +7848,20 @@ 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
diff --git a/MdePkg/Library/BaseLib/Ia32/GccInline.c b/MdePkg/Library/BaseLib/Ia32/GccInline.c
index c2565ab9a183..26732acd8431 100644
--- a/MdePkg/Library/BaseLib/Ia32/GccInline.c
+++ b/MdePkg/Library/BaseLib/Ia32/GccInline.c
@@ -612,3 +612,20 @@ AsmXGetBv (
 
   return Data;
 }
+
+
+/**
+  Executes a VMGEXIT instruction.
+
+  Executes a VMGEXIT instruction. This function is only available on IA-32 and
+  X64.
+
+**/
+VOID
+EFIAPI
+AsmVmgExit (
+  VOID
+  )
+{
+  __asm__ __volatile__ ("rep; vmmcall":::"memory");
+}
diff --git a/MdePkg/Library/BaseLib/X64/GccInline.c b/MdePkg/Library/BaseLib/X64/GccInline.c
index 65f864e35922..1f584b6e50fe 100644
--- a/MdePkg/Library/BaseLib/X64/GccInline.c
+++ b/MdePkg/Library/BaseLib/X64/GccInline.c
@@ -590,3 +590,20 @@ AsmXGetBv (
 
   return (((UINT64)HighData) << 32) | LowData;
 }
+
+
+/**
+  Executes a VMGEXIT instruction.
+
+  Executes a VMGEXIT instruction. This function is only available on IA-32 and
+  X64.
+
+**/
+VOID
+EFIAPI
+AsmVmgExit (
+  VOID
+  )
+{
+  __asm__ __volatile__ ("rep; vmmcall":::"memory");
+}
diff --git a/MdePkg/Library/BaseLib/Ia32/VmgExit.nasm b/MdePkg/Library/BaseLib/Ia32/VmgExit.nasm
new file mode 100644
index 000000000000..a4b37385cc7a
--- /dev/null
+++ b/MdePkg/Library/BaseLib/Ia32/VmgExit.nasm
@@ -0,0 +1,37 @@
+;------------------------------------------------------------------------------
+;
+; 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, so work around
+; this by temporarily switching to 64-bit mode.
+;
+BITS    64
+    rep     vmmcall
+BITS    32
+    ret
+
diff --git a/MdePkg/Library/BaseLib/X64/VmgExit.nasm b/MdePkg/Library/BaseLib/X64/VmgExit.nasm
new file mode 100644
index 000000000000..26f034593c67
--- /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
+
-- 
2.27.0


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