OvmfPkg/MemEncryptSevLib: Address range encryption state interface

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3108

Update the MemEncryptSevLib library to include an interface that can
report the encryption state on a range of memory. The values will
represent the range as being unencrypted, encrypted, a mix of unencrypted
and encrypted, and error (e.g. ranges that aren't mapped).

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <0d98f4d42a2b67310c29bac7bcdcf1eda6835847.1610045305.git.thomas.lendacky@amd.com>

OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.h

@@ -3,7 +3,7 @@
   Virtual Memory Management Services to set or clear the memory encryption bit
 
   Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
-  Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
+  Copyright (c) 2017 - 2020, AMD Incorporated. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -178,7 +178,17 @@ typedef struct {
   UINTN           FreePages;
 } PAGE_TABLE_POOL;
 
+/**
+  Return the pagetable memory encryption mask.
 
+  @return  The pagetable memory encryption mask.
+
+**/
+UINT64
+EFIAPI
+InternalGetMemEncryptionAddressMask (
+  VOID
+  );
 
 /**
   This function clears memory encryption bit for the memory region specified by
@@ -234,4 +244,27 @@ InternalMemEncryptSevSetMemoryEncrypted (
   IN  BOOLEAN                 Flush
   );
 
+/**
+  Returns the encryption state of the specified virtual address range.
+
+  @param[in]  Cr3BaseAddress          Cr3 Base Address (if zero then use
+                                      current CR3)
+  @param[in]  BaseAddress             Base address to check
+  @param[in]  Length                  Length of virtual address range
+
+  @retval MemEncryptSevAddressRangeUnencrypted  Address range is mapped
+                                                unencrypted
+  @retval MemEncryptSevAddressRangeEncrypted    Address range is mapped
+                                                encrypted
+  @retval MemEncryptSevAddressRangeMixed        Address range is mapped mixed
+  @retval MemEncryptSevAddressRangeError        Address range is not mapped
+**/
+MEM_ENCRYPT_SEV_ADDRESS_RANGE_STATE
+EFIAPI
+InternalMemEncryptSevGetAddressRangeState (
+  IN PHYSICAL_ADDRESS         Cr3BaseAddress,
+  IN PHYSICAL_ADDRESS         BaseAddress,
+  IN UINTN                    Length
+  );
+
 #endif