accel/tcg: Handle get_page_addr_code() returning -1 in tb_check_watchpoint()

When we support execution from non-RAM MMIO regions, get_page_addr_code()
will return -1 to indicate that there is no RAM at the requested address.
Handle this in tb_check_watchpoint() -- if the exception happened for a
PC which doesn't correspond to RAM then there is no need to invalidate
any TBs, because the one-instruction TB will not have been cached.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Tested-by: NCédric Le Goater <clg@kaod.org>
Message-id: 20180710160013.26559-4-peter.maydell@linaro.org

accel/tcg/translate-all.c

@@ -2121,7 +2121,9 @@ void tb_check_watchpoint(CPUState *cpu)
 
         cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
         addr = get_page_addr_code(env, pc);
-        tb_invalidate_phys_range(addr, addr + 1);
+        if (addr != -1) {
+            tb_invalidate_phys_range(addr, addr + 1);
+        }
     }
 }