[PATCH 08/13] MdePkg/BaseLib: add support for RMPADJUST instruction

["Brijesh Singh" <brijesh.singh@amd.com>]

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

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

The RMPADJUST instruction will be used by the SEV-SNP guest to modify the
RMP permissions for a guest page. See AMD APM volume 3 for further
details.

Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 MdePkg/Library/BaseLib/BaseLib.inf        |  1 +
 MdePkg/Include/Library/BaseLib.h          | 36 +++++++++++++++++++-
 MdePkg/Include/X64/Nasm.inc               |  8 +++++
 MdePkg/Library/BaseLib/X64/RmpAdjust.nasm | 40 +++++++++++++++++++++++
 4 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 MdePkg/Library/BaseLib/X64/RmpAdjust.nasm

diff --git a/MdePkg/Library/BaseLib/BaseLib.inf b/MdePkg/Library/BaseLib/BaseLib.inf
index 89a52f72c08a..6ccb8997b7e8 100644
--- a/MdePkg/Library/BaseLib/BaseLib.inf
+++ b/MdePkg/Library/BaseLib/BaseLib.inf
@@ -319,6 +319,7 @@ [Sources.X64]
   X64/DisablePaging64.nasm
   X64/Pvalidate.nasm
   X64/RdRand.nasm
+  X64/RmpAdjust.nasm
   X64/XGetBv.nasm
   X64/XSetBv.nasm
   X64/VmgExit.nasm
diff --git a/MdePkg/Include/Library/BaseLib.h b/MdePkg/Include/Library/BaseLib.h
index f177034af6a1..04e58f995b9a 100644
--- a/MdePkg/Include/Library/BaseLib.h
+++ b/MdePkg/Include/Library/BaseLib.h
@@ -4857,9 +4857,43 @@ AsmPvalidate (
   IN   BOOLEAN                 Validate,
   IN   PHYSICAL_ADDRESS        Address
   );
+
+//
+// RDX settings for RMPADJUST
+//
+#define RMPADJUST_VMPL_MAX               3
+#define RMPADJUST_VMPL_MASK              0xFF
+#define RMPADJUST_VMPL_SHIFT             0
+#define RMPADJUST_PERMISSION_MASK_MASK   0xFF
+#define RMPADJUST_PERMISSION_MASK_SHIFT  8
+#define RMPADJUST_VMSA_PAGE_BIT          BIT16
+
+/**
+  Adjusts the permissions of an SEV-SNP guest page.
+
+  Executes a RMPADJUST instruction with the register state specified by Rax,
+  Rcx and Rdx. Returns Eax. This function is only available x64.
+
+  The instruction is available only when CPUID Fn8000_001F_EAX[SNP]=1.
+
+  @param[in]  Rax   The value to load into RAX before executing the RMPADJUST
+                    instruction.
+  @param[in]  Rcx   The value to load into RCX before executing the RMPADJUST
+                    instruction.
+  @param[in]  Rdx   The value to load into RDX before executing the RMPADJUST
+                    instruction.
+
+  @return     Eax
+**/
+UINTN
+EFIAPI
+AsmRmpAdjust (
+  IN      UINTN                     Rax,
+  IN      UINTN                     Rcx,
+  IN      UINTN                     Rdx
+  );
 #endif
 
-
 #if defined (MDE_CPU_IA32) || defined (MDE_CPU_X64)
 ///
 /// IA32 and x64 Specific Functions.
diff --git a/MdePkg/Include/X64/Nasm.inc b/MdePkg/Include/X64/Nasm.inc
index 528bb3385609..cfb14edc9449 100644
--- a/MdePkg/Include/X64/Nasm.inc
+++ b/MdePkg/Include/X64/Nasm.inc
@@ -41,6 +41,14 @@
     DB 0xF2, 0x0F, 0x01, 0xFF
 %endmacro
 
+;
+; Macro for the RMPADJUST instruction, defined in AMD APM volume 3.
+; NASM feature request URL: https://bugzilla.nasm.us/show_bug.cgi?id=3392754
+;
+%macro RMPADJUST       0
+    DB 0xF3, 0x0F, 0x01, 0xFE
+%endmacro
+
 ; NASM provides built-in macros STRUC and ENDSTRUC for structure definition.
 ; For example, to define a structure called mytype containing a longword,
 ; a word, a byte and a string of bytes, you might code
diff --git a/MdePkg/Library/BaseLib/X64/RmpAdjust.nasm b/MdePkg/Library/BaseLib/X64/RmpAdjust.nasm
new file mode 100644
index 000000000000..f2c295b67c9c
--- /dev/null
+++ b/MdePkg/Library/BaseLib/X64/RmpAdjust.nasm
@@ -0,0 +1,40 @@
+;-----------------------------------------------------------------------------
+;
+; Copyright (c) 2021, Advanced Micro Devices, Inc. All rights reserved.<BR>
+; SPDX-License-Identifier: BSD-2-Clause-Patent
+;
+; Module Name:
+;
+;   RmpAdjust.Asm
+;
+; Abstract:
+;
+;   AsmRmpAdjust function
+;
+; Notes:
+;
+;-----------------------------------------------------------------------------
+
+%include "Nasm.inc"
+
+    SECTION .text
+
+;-----------------------------------------------------------------------------
+;  UINTN
+;  EFIAPI
+;  AsmRmpAdjust (
+;    IN  UINTN  Rax,
+;    IN  UINTN  Rcx,
+;    IN  UINTN  Rdx
+;    )
+;-----------------------------------------------------------------------------
+global ASM_PFX(AsmRmpAdjust)
+ASM_PFX(AsmRmpAdjust):
+  mov     rax, rcx       ; Input Rax is in RCX by calling convention
+  mov     rcx, rdx       ; Input Rcx is in RDX by calling convention
+  mov     rdx, r8        ; Input Rdx is in R8  by calling convention
+
+  RMPADJUST
+
+  ; RMPADJUST returns the status in the EAX register.
+  ret
-- 
2.17.1