[Qemu-devel] [PATCH v6 16/18] virtio-serial: Discard data that guest sends us when ports aren't connected

[Amit Shah <amit.shah@redhat.com>]

Before the earlier patch, we relied on incorrect virtio api usage to
signal to the guest that a particular buffer wasn't consumed by the
host.

After fixing that, we now just discard the data the guest sends us while
a host port is disconnected or doesn't have a handler registered for
consuming data.

This commit really doesn't change anything from the current behaviour,
just makes the code slightly better by spinning off data handling to
ports in another function.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 hw/virtio-serial-bus.c |   69 ++++++++++++++++++++++-------------------------
 1 files changed, 32 insertions(+), 37 deletions(-)

diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
index ad44127..8d07152 100644
--- a/hw/virtio-serial-bus.c
+++ b/hw/virtio-serial-bus.c
@@ -111,6 +111,30 @@ static size_t write_to_port(VirtIOSerialPort *port,
     return offset;
 }
 
+static void flush_queued_data(VirtIOSerialPort *port, VirtQueue *vq,
+                              VirtIODevice *vdev, bool discard)
+{
+    VirtQueueElement elem;
+
+    assert(port || discard);
+
+    while (virtqueue_pop(vq, &elem)) {
+        uint8_t *buf;
+        size_t ret, buf_size;
+
+        if (!discard) {
+            buf_size = iov_size(elem.out_sg, elem.out_num);
+            buf = qemu_malloc(buf_size);
+            ret = iov_to_buf(elem.out_sg, elem.out_num, buf, 0, buf_size);
+
+            port->info->have_data(port, buf, ret);
+            qemu_free(buf);
+        }
+        virtqueue_push(vq, &elem, 0);
+    }
+    virtio_notify(vdev, vq);
+}
+
 static size_t send_control_msg(VirtIOSerialPort *port, void *buf, size_t len)
 {
     VirtQueueElement elem;
@@ -345,47 +369,18 @@ static void control_out(VirtIODevice *vdev, VirtQueue *vq)
 static void handle_output(VirtIODevice *vdev, VirtQueue *vq)
 {
     VirtIOSerial *vser;
-    VirtQueueElement elem;
+    VirtIOSerialPort *port;
+    bool discard;
 
     vser = DO_UPCAST(VirtIOSerial, vdev, vdev);
+    port = find_port_by_vq(vser, vq);
 
-    while (virtqueue_pop(vq, &elem)) {
-        VirtIOSerialPort *port;
-        uint8_t *buf;
-        size_t ret, buf_size;
-
-        port = find_port_by_vq(vser, vq);
-        if (!port) {
-            ret = 0;
-            goto next_buf;
-        }
-
-	if (!port->host_connected) {
-            ret = 0;
-            goto next_buf;
-        }
-
-        /*
-         * A port may not have any handler registered for consuming the
-         * data that the guest sends or it may not have a chardev associated
-         * with it. Just ignore the data in that case.
-         */
-        if (!port->info->have_data) {
-            ret = 0;
-            goto next_buf;
-        }
-
-        buf_size = iov_size(elem.out_sg, elem.out_num);
-        buf = qemu_malloc(buf_size);
-        ret = iov_to_buf(elem.out_sg, elem.out_num, buf, 0, buf_size);
-
-        port->info->have_data(port, buf, ret);
-        qemu_free(buf);
-
-    next_buf:
-        virtqueue_push(vq, &elem, 0);
+    discard = false;
+    if (!port || !port->host_connected || !port->info->have_data) {
+        discard = true;
     }
-    virtio_notify(vdev, vq);
+
+    flush_queued_data(port, vq, vdev, discard);
 }
 
 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
-- 
1.6.2.5