target/s390x: Improve heuristic for ipte

If only the page index is set, most likely we don't have a valid
virtual address. Let's do a full tlb flush for that case.
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Message-Id: <20170622094151.28633-3-david@redhat.com>
Signed-off-by: NRichard Henderson <rth@twiddle.net>

target/s390x/mem_helper.c

@@ -1630,16 +1630,23 @@ void HELPER(ipte)(CPUS390XState *env, uint64_t pto, uint64_t vaddr,
     /* XXX we exploit the fact that Linux passes the exact virtual
        address here - it's not obliged to! */
     if (m4 & 1) {
-        tlb_flush_page(cs, page);
-    } else {
-        tlb_flush_page_all_cpus_synced(cs, page);
-    }
-
-    /* XXX 31-bit hack */
-    if (m4 & 1) {
-        tlb_flush_page(cs, page ^ 0x80000000);
+        if (vaddr & ~VADDR_PX) {
+            tlb_flush_page(cs, page);
+            /* XXX 31-bit hack */
+            tlb_flush_page(cs, page ^ 0x80000000);
+        } else {
+            /* looks like we don't have a valid virtual address */
+            tlb_flush(cs);
+        }
     } else {
-        tlb_flush_page_all_cpus_synced(cs, page ^ 0x80000000);
+        if (vaddr & ~VADDR_PX) {
+            tlb_flush_page_all_cpus_synced(cs, page);
+            /* XXX 31-bit hack */
+            tlb_flush_page_all_cpus_synced(cs, page ^ 0x80000000);
+        } else {
+            /* looks like we don't have a valid virtual address */
+            tlb_flush_all_cpus_synced(cs);
+        }
     }
 }