virtio/ringtest: fix up need_event math

last kicked event index must be updated unconditionally:
even if we don't need to kick, we do not want to re-check
the same entry for events.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

1 files changed, 15 insertions, 9 deletions

diff --git a/tools/virtio/ringtest/ring.c b/tools/virtio/ringtest/ring.c
index 747c5dd47be8..2b9859beea65 100644
--- a/tools/virtio/ringtest/ring.c
+++ b/tools/virtio/ringtest/ring.c
@@ -188,16 +188,18 @@ bool enable_call()
 
 void kick_available(void)
 {
+        bool need;
+
         /* Flush in previous flags write */
         /* Barrier C (for pairing) */
         smp_mb();
-        if (!need_event(event->kick_index,
-                        guest.avail_idx,
-                        guest.kicked_avail_idx))
-                return;
+        need = need_event(event->kick_index,
+                           guest.avail_idx,
+                           guest.kicked_avail_idx);
 
         guest.kicked_avail_idx = guest.avail_idx;
-        kick();
+        if (need)
+                kick();
 }
 
 /* host side */
@@ -253,14 +255,18 @@ bool use_buf(unsigned *lenp, void **bufp)
 
 void call_used(void)
 {
+        bool need;
+
         /* Flush in previous flags write */
         /* Barrier D (for pairing) */
         smp_mb();
-        if (!need_event(event->call_index,
+
+        need = need_event(event->call_index,
                         host.used_idx,
-                        host.called_used_idx))
-                return;
+                        host.called_used_idx);
 
         host.called_used_idx = host.used_idx;
-        call();
+
+        if (need)
+                call();
 }