axienet: Flush queued packets when rx is done

eth_can_rx checks s->rxsize and returns false if it is non-zero. Because
of the .can_receive semantics change, this will make the incoming queue
disabled by peer, until it is explicitly flushed. So we should flush it
when s->rxsize is becoming zero.

Squash eth_can_rx semantics into etx_rx and drop .can_receive()
callback, also add flush when rx buffer becomes available again after a
packet gets queued.

The other conditions, "!axienet_rx_resetting(s) &&
axienet_rx_enabled(s)" are OK because enet_write already calls
qemu_flush_queued_packets when the register bits are changed.

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1436955553-22791-13-git-send-email-famz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

hw/net/xilinx_axienet.c

@@ -401,6 +401,9 @@ struct XilinxAXIEnet {
 
     uint8_t rxapp[CONTROL_PAYLOAD_SIZE];
     uint32_t rxappsize;
+
+    /* Whether axienet_eth_rx_notify should flush incoming queue. */
+    bool need_flush;
 };
 
 static void axienet_rx_reset(XilinxAXIEnet *s)
@@ -658,10 +661,8 @@ static const MemoryRegionOps enet_ops = {
     .endianness = DEVICE_LITTLE_ENDIAN,
 };
 
-static int eth_can_rx(NetClientState *nc)
+static int eth_can_rx(XilinxAXIEnet *s)
 {
-    XilinxAXIEnet *s = qemu_get_nic_opaque(nc);
-
     /* RX enabled?  */
     return !s->rxsize && !axienet_rx_resetting(s) && axienet_rx_enabled(s);
 }
@@ -701,6 +702,10 @@ static void axienet_eth_rx_notify(void *opaque)
         s->rxpos += ret;
         if (!s->rxsize) {
             s->regs[R_IS] |= IS_RX_COMPLETE;
+            if (s->need_flush) {
+                s->need_flush = false;
+                qemu_flush_queued_packets(qemu_get_queue(s->nic));
+            }
         }
     }
     enet_update_irq(s);
@@ -721,6 +726,11 @@ static ssize_t eth_rx(NetClientState *nc, const uint8_t *buf, size_t size)
 
     DENET(qemu_log("%s: %zd bytes\n", __func__, size));
 
+    if (!eth_can_rx(s)) {
+        s->need_flush = true;
+        return 0;
+    }
+
     unicast = ~buf[0] & 0x1;
     broadcast = memcmp(buf, sa_bcast, 6) == 0;
     multicast = !unicast && !broadcast;
@@ -925,7 +935,6 @@ xilinx_axienet_data_stream_push(StreamSlave *obj, uint8_t *buf, size_t size)
 static NetClientInfo net_xilinx_enet_info = {
     .type = NET_CLIENT_OPTIONS_KIND_NIC,
     .size = sizeof(NICState),
-    .can_receive = eth_can_rx,
     .receive = eth_rx,
 };