fix(lib/s2tt) : PA must be <= 48 bits for LPA2 disabled Realm

If FEAT_LPA2 is disabled for the realm, add a check to
ensure that PA for some args of RTT related commands is
within 48 bits.

Change-Id: If1647a1848823e63cccf07f46876367c165ef8a5
Signed-off-by: Shruti Gupta <shruti.gupta@arm.com>
diff --git a/lib/s2tt/include/s2tt.h b/lib/s2tt/include/s2tt.h
index cc7d0fd..89a30fc 100644
--- a/lib/s2tt/include/s2tt.h
+++ b/lib/s2tt/include/s2tt.h
@@ -40,8 +40,10 @@
 
 #define S2TT_MIN_IPA_BITS		U(32)
 #define S2TT_MAX_IPA_BITS		U(48)
+#define S2TT_MAX_PA_BITS		U(48)
 
 #define S2TT_MAX_IPA_BITS_LPA2		U(52)
+#define S2TT_MAX_PA_BITS_LPA2		U(52)
 #define S2TT_MAX_IPA_SIZE_LPA2		(UL(1) << S2TT_MAX_IPA_BITS_LPA2)
 
 #define S2TT_MIN_STARTING_LEVEL		(0)
diff --git a/lib/s2tt/src/s2tt.c b/lib/s2tt/src/s2tt.c
index 3ad094c..0cde136 100644
--- a/lib/s2tt/src/s2tt.c
+++ b/lib/s2tt/src/s2tt.c
@@ -563,6 +563,8 @@
 	 * Test that all fields that are not controlled by the host are zero
 	 * and that the output address is correctly aligned. Note that
 	 * the host is permitted to map any physical address outside PAR.
+	 * Note that this also checks for the case when FEAT_LPA2 is disabled
+	 * for the Realm, then the PA in `s2tte` must be <= 48 bits wide.
 	 */
 	if ((s2tte & ~mask) != 0UL) {
 		return false;