s390x/tcg: MVPG: Properly wrap the addresses

We have to mask of any unused bits. While at it, document what exactly is
missing.
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NDavid Hildenbrand <david@redhat.com>

target/s390x/mem_helper.c

@@ -679,8 +679,15 @@ uint32_t HELPER(mvpg)(CPUS390XState *env, uint64_t r0, uint64_t r1, uint64_t r2)
         s390_program_interrupt(env, PGM_SPECIFICATION, ILEN_AUTO, GETPC());
     }
 
-    /* ??? missing r0 handling, which includes access keys, but more
-       importantly optional suppression of the exception!  */
+    r1 = wrap_address(env, r1 & TARGET_PAGE_MASK);
+    r2 = wrap_address(env, r2 & TARGET_PAGE_MASK);
+
+    /*
+     * TODO:
+     * - Access key handling
+     * - CC-option with surpression of page-translation exceptions
+     * - Store r1/r2 register identifiers at real location 162
+     */
     fast_memmove(env, r1, r2, TARGET_PAGE_SIZE, GETPC());
     return 0; /* data moved */
 }