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/Include/Library/MemEncryptSevLib.h

@@ -33,6 +33,16 @@ typedef struct _SEC_SEV_ES_WORK_AREA {
   UINT64   EncryptionMask;
 } SEC_SEV_ES_WORK_AREA;
 
+//
+// Memory encryption address range states.
+//
+typedef enum {
+  MemEncryptSevAddressRangeUnencrypted,
+  MemEncryptSevAddressRangeEncrypted,
+  MemEncryptSevAddressRangeMixed,
+  MemEncryptSevAddressRangeError,
+} MEM_ENCRYPT_SEV_ADDRESS_RANGE_STATE;
+
 /**
   Returns a boolean to indicate whether SEV-ES is enabled.
 
@@ -147,4 +157,27 @@ MemEncryptSevGetEncryptionMask (
   VOID
   );
 
+/**
+  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
+MemEncryptSevGetAddressRangeState (
+  IN PHYSICAL_ADDRESS         Cr3BaseAddress,
+  IN PHYSICAL_ADDRESS         BaseAddress,
+  IN UINTN                    Length
+  );
+
 #endif // _MEM_ENCRYPT_SEV_LIB_H_