virtio-queue: add unit test for queue size

Signed-off-by: George Pisaltu <[email protected]>

Author: georgepisaltu

src/devices/src/virtio/queue.rs

@@ -476,6 +476,24 @@ pub(crate) mod tests {
         assert!(!q.is_valid(m));
         q.size = q.max_size;
 
+        // or when avail_idx - next_avail > max_size
+        q.next_avail = Wrapping(5);
+        assert!(!q.is_valid(m));
+        // avail_ring + 2 is the address of avail_idx in guest mem
+        m.write_obj::<u16>(64 as u16, q.avail_ring.unchecked_add(2))
+            .unwrap();
+        assert!(!q.is_valid(m));
+        m.write_obj::<u16>(5 as u16, q.avail_ring.unchecked_add(2))
+            .unwrap();
+        q.max_size = 2;
+        assert!(!q.is_valid(m));
+
+        // reset dirtied values
+        q.max_size = 16;
+        q.next_avail = Wrapping(0);
+        m.write_obj::<u16>(0, q.avail_ring.unchecked_add(2))
+            .unwrap();
+
         // or if the various addresses are off
 
         q.desc_table = GuestAddress(0xffff_ffff);