[edk2-devel] [PATCH v15 06/46] MdePkg/BaseLib: Add support for the XGETBV instruction

[Lendacky, Thomas]

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

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 at intel.com>
Cc: Liming Gao <liming.gao at intel.com>
Reviewed-by: Liming Gao <liming.gao at intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky at amd.com>
---
 MdePkg/Library/BaseLib/BaseLib.inf      |  2 ++
 MdePkg/Include/Library/BaseLib.h        | 17 ++++++++++
 MdePkg/Library/BaseLib/Ia32/XGetBv.nasm | 31 ++++++++++++++++++
 MdePkg/Library/BaseLib/X64/XGetBv.nasm  | 34 ++++++++++++++++++++
 4 files changed, 84 insertions(+)

diff --git a/MdePkg/Library/BaseLib/BaseLib.inf b/MdePkg/Library/BaseLib/BaseLib.inf
index c740a819cacf..3b93b5db8d24 100644
--- a/MdePkg/Library/BaseLib/BaseLib.inf
+++ b/MdePkg/Library/BaseLib/BaseLib.inf
@@ -183,6 +183,7 @@ [Sources.Ia32]
   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 @@ [Sources.X64]
   X64/EnableDisableInterrupts.nasm
   X64/DisablePaging64.nasm
   X64/RdRand.nasm
+  X64/XGetBv.nasm
   ChkStkGcc.c  | GCC
 
 [Sources.EBC]
diff --git a/MdePkg/Include/Library/BaseLib.h b/MdePkg/Include/Library/BaseLib.h
index 8e7b87cbda4e..7edf0051a0a0 100644
--- a/MdePkg/Include/Library/BaseLib.h
+++ b/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
diff --git a/MdePkg/Library/BaseLib/Ia32/XGetBv.nasm b/MdePkg/Library/BaseLib/Ia32/XGetBv.nasm
new file mode 100644
index 000000000000..9f7b03bbff35
--- /dev/null
+++ b/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
diff --git a/MdePkg/Library/BaseLib/X64/XGetBv.nasm b/MdePkg/Library/BaseLib/X64/XGetBv.nasm
new file mode 100644
index 000000000000..09f3be8ae0a8
--- /dev/null
+++ b/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
+
-- 
2.28.0


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