MdePkg/BaseLib: Add support for the XGETBV instruction

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

Under SEV-ES, a CPUID instruction requires the current value of the XCR0
register. In order to retrieve that value, the XGETBV instruction needs
to be executed.

Provide the necessary support to execute the XGETBV instruction.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>

MdePkg/Include/Library/BaseLib.h

@@ -7831,6 +7831,23 @@ AsmLfence (
   VOID
   );
 
+/**
+  Executes a XGETBV instruction
+
+  Executes a XGETBV instruction. This function is only available on IA-32 and
+  x64.
+
+  @param[in] Index        Extended control register index
+
+  @return                 The current value of the extended control register
+**/
+UINT64
+EFIAPI
+AsmXGetBv (
+  IN UINT32  Index
+  );
+
+
 /**
   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

MdePkg/Library/BaseLib/BaseLib.inf

@@ -183,6 +183,7 @@
   Ia32/EnableCache.nasm| GCC
   Ia32/DisableCache.nasm| GCC
   Ia32/RdRand.nasm
+  Ia32/XGetBv.nasm
 
   Ia32/DivS64x64Remainder.c
   Ia32/InternalSwitchStack.c | MSFT
@@ -315,6 +316,7 @@
   X64/EnableDisableInterrupts.nasm
   X64/DisablePaging64.nasm
   X64/RdRand.nasm
+  X64/XGetBv.nasm
   ChkStkGcc.c  | GCC
 
 [Sources.EBC]

MdePkg/Library/BaseLib/Ia32/XGetBv.nasm

@@ -0,0 +1,31 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
+; SPDX-License-Identifier: BSD-2-Clause-Patent
+;
+; Module Name:
+;
+;   XGetBv.Asm
+;
+; Abstract:
+;
+;   AsmXgetBv function
+;
+; Notes:
+;
+;------------------------------------------------------------------------------
+
+    SECTION .text
+
+;------------------------------------------------------------------------------
+; UINT64
+; EFIAPI
+; AsmXGetBv (
+;   IN UINT32  Index
+;   );
+;------------------------------------------------------------------------------
+global ASM_PFX(AsmXGetBv)
+ASM_PFX(AsmXGetBv):
+    mov     ecx, [esp + 4]
+    xgetbv
+    ret

MdePkg/Library/BaseLib/X64/XGetBv.nasm

@@ -0,0 +1,34 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
+; SPDX-License-Identifier: BSD-2-Clause-Patent
+;
+; Module Name:
+;
+;   XGetBv.Asm
+;
+; Abstract:
+;
+;   AsmXgetBv function
+;
+; Notes:
+;
+;------------------------------------------------------------------------------
+
+    DEFAULT REL
+    SECTION .text
+
+;------------------------------------------------------------------------------
+; UINT64
+; EFIAPI
+; AsmXGetBv (
+;   IN UINT32  Index
+;   );
+;------------------------------------------------------------------------------
+global ASM_PFX(AsmXGetBv)
+ASM_PFX(AsmXGetBv):
+    xgetbv
+    shl     rdx, 32
+    or      rax, rdx
+    ret
+