MdePkg/BaseLib: add support for PVALIDATE instruction

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

The PVALIDATE instruction validates or rescinds validation of a guest
page RMP entry. Upon completion, a return code is stored in EAX, rFLAGS
bits OF, ZF, AF, PF and SF are set based on this return code. If the
instruction completed succesfully, the rFLAGS bit CF indicates if the
contents of the RMP entry were changed or not.

For more information about the instruction see AMD APM volume 3.

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: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Message-Id: <20210519181949.6574-8-brijesh.singh@amd.com>

MdePkg/Include/X64/Nasm.inc

@@ -33,6 +33,14 @@
     DB 0xF3, 0x48, 0x0F, 0xAE, 0xE8
 %endmacro
 
+;
+; Macro for the PVALIDATE instruction, defined in AMD APM volume 3.
+; NASM feature request URL: https://bugzilla.nasm.us/show_bug.cgi?id=3392753
+;
+%macro PVALIDATE       0
+    DB 0xF2, 0x0F, 0x01, 0xFF
+%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