[Qemu-devel] [PATCH v5 11/13] virtio-console: chardev hotswap support

[Anton Nefedov <anton.nefedov@virtuozzo.com>]

In case of a backend change, the handler functions and the watch have
to be reset.
Also, avoid unsafe qemu_chr_fe_get_driver() usage even though the pointer
is not really stored.

Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 hw/char/virtio-console.c | 35 ++++++++++++++++++++++++++++++-----
 1 file changed, 30 insertions(+), 5 deletions(-)

diff --git a/hw/char/virtio-console.c b/hw/char/virtio-console.c
index afb4949..198b2a8 100644
--- a/hw/char/virtio-console.c
+++ b/hw/char/virtio-console.c
@@ -49,7 +49,7 @@ static ssize_t flush_buf(VirtIOSerialPort *port,
     VirtConsole *vcon = VIRTIO_CONSOLE(port);
     ssize_t ret;
 
-    if (!qemu_chr_fe_get_driver(&vcon->chr)) {
+    if (!qemu_chr_fe_backend_connected(&vcon->chr)) {
         /* If there's no backend, we can just say we consumed all data. */
         return len;
     }
@@ -163,12 +163,35 @@ static void chr_event(void *opaque, int event)
     }
 }
 
+static int chr_be_change(void *opaque)
+{
+    VirtConsole *vcon = opaque;
+    VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
+    VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
+
+    if (k->is_console) {
+        qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
+                                 NULL, chr_be_change, vcon, NULL, true);
+    } else {
+        qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
+                                 chr_event, chr_be_change, vcon, NULL, false);
+    }
+
+    if (vcon->watch) {
+        g_source_remove(vcon->watch);
+        vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
+                                            G_IO_OUT | G_IO_HUP,
+                                            chr_write_unblocked, vcon);
+    }
+
+    return 0;
+}
+
 static void virtconsole_realize(DeviceState *dev, Error **errp)
 {
     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(dev);
     VirtConsole *vcon = VIRTIO_CONSOLE(dev);
     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(dev);
-    Chardev *chr = qemu_chr_fe_get_driver(&vcon->chr);
 
     if (port->id == 0 && !k->is_console) {
         error_setg(errp, "Port number 0 on virtio-serial devices reserved "
@@ -176,7 +199,7 @@ static void virtconsole_realize(DeviceState *dev, Error **errp)
         return;
     }
 
-    if (chr) {
+    if (qemu_chr_fe_backend_connected(&vcon->chr)) {
         /*
          * For consoles we don't block guest data transfer just
          * because nothing is connected - we'll just let it go
@@ -188,11 +211,13 @@ static void virtconsole_realize(DeviceState *dev, Error **errp)
          */
         if (k->is_console) {
             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
-                                     NULL, NULL, vcon, NULL, true);
+                                     NULL, chr_be_change,
+                                     vcon, NULL, true);
             virtio_serial_open(port);
         } else {
             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
-                                     chr_event, NULL, vcon, NULL, false);
+                                     chr_event, chr_be_change,
+                                     vcon, NULL, false);
         }
     }
 }
-- 
2.7.4