MdePkg/BaseLib: add support for RMPADJUST instruction

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>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Message-Id: <20210519181949.6574-9-brijesh.singh@amd.com>

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
+
+;-----------------------------------------------------------------------------
+;  UINT32
+;  EFIAPI
+;  AsmRmpAdjust (
+;    IN  UINT64  Rax,
+;    IN  UINT64  Rcx,
+;    IN  UINT64  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