Re: [PATCH v12 07/46] MdePkg/BaseLib: Add support for the VMGEXIT instruction

["Liming Gao" <liming.gao@intel.com>]

Tom:
  I meet with GCC failure on this patch. Can you help check it? If nasm doesn't support the vmmcall instruction in 32-bit mode, you have to use inline assembly to support it. 

Edk2/Build/IntelFsp2Pkg/DEBUG_GCC5/IA32/MdePkg/Library/BaseLib/BaseLib/OUTPUT/Ia32/VmgExit.iii:33: error: elf32 output format does not support 64-bit code
GNUmakefile:741: recipe for target

Thanks
Liming
-----Original Message-----
From: Tom Lendacky <thomas.lendacky@amd.com> 
Sent: 2020年7月27日 23:26
To: devel@edk2.groups.io
Cc: Brijesh Singh <brijesh.singh@amd.com>; Ard Biesheuvel <ard.biesheuvel@arm.com>; Dong, Eric <eric.dong@intel.com>; Justen, Jordan L <jordan.l.justen@intel.com>; Laszlo Ersek <lersek@redhat.com>; Gao, Liming <liming.gao@intel.com>; Kinney, Michael D <michael.d.kinney@intel.com>; Ni, Ray <ray.ni@intel.com>
Subject: [PATCH v12 07/46] MdePkg/BaseLib: Add support for the VMGEXIT instruction

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/VmgExit.nasm | 37 ++++++++++++++++++++++++  MdePkg/Library/BaseLib/X64/VmgExit.nasm  | 32 ++++++++++++++++++++
 4 files changed, 85 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 3b93b5db8d24..3b85c56c3c03 100644
--- a/MdePkg/Library/BaseLib/BaseLib.inf
+++ b/MdePkg/Library/BaseLib/BaseLib.inf
@@ -184,6 +184,7 @@ [Sources.Ia32]
   Ia32/DisableCache.nasm| GCC
   Ia32/RdRand.nasm
   Ia32/XGetBv.nasm
+  Ia32/VmgExit.nasm
 
   Ia32/DivS64x64Remainder.c
   Ia32/InternalSwitchStack.c | MSFT
@@ -317,6 +318,7 @@ [Sources.X64]
   X64/DisablePaging64.nasm
   X64/RdRand.nasm
   X64/XGetBv.nasm
+  X64/VmgExit.nasm
   ChkStkGcc.c  | GCC
 
 [Sources.EBC]
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/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