main-loop: Calculate poll timeout using timeout argument

The timeout argument was unused up to now,
but it can be used to reduce the poll_timeout when it is infinite
(negative value) or larger than timeout.
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

main-loop.c

@@ -425,7 +425,7 @@ static int os_host_main_loop_wait(uint32_t timeout)
     if (nfds >= 0) {
         ret = select(nfds + 1, &rfds, &wfds, &xfds, &tv0);
         if (ret != 0) {
-            /* TODO. */
+            timeout = 0;
         }
     }
 
@@ -439,6 +439,10 @@ static int os_host_main_loop_wait(uint32_t timeout)
         poll_fds[n_poll_fds + i].events = G_IO_IN;
     }
 
+    if (poll_timeout < 0 || timeout < poll_timeout) {
+        poll_timeout = timeout;
+    }
+
     qemu_mutex_unlock_iothread();
     ret = g_poll(poll_fds, n_poll_fds + w->num, poll_timeout);
     qemu_mutex_lock_iothread();