[Qemu-devel] [PATCH for-2.1 v2 1/2] virtio-serial: report frontend connection state via monitor

[Laszlo Ersek <lersek@redhat.com>]

Libvirt wants to know about the guest-side connection state of some
virtio-serial ports (in particular the one(s) assigned to guest agent(s)).
Report such states with a new monitor event.

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1080376
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    v2:
    - emit event unconditionally; drop per-port "report_connstate" property
      [Eric]
    - rate-limit the new event [Eric] -- unify it with other
      guest-triggerable events in monitor_qapi_event_init()
    - rebased to Wenchao's qapi-event series
    - introduce one event only, VSERPORT_CHANGE, and make the port status a
      parameter [Eric]

 qapi-event.json          | 16 ++++++++++++++++
 qapi-schema.json         | 16 ++++++++++++++++
 hw/char/virtio-console.c | 15 ++++++++++++---
 monitor.c                |  1 +
 4 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/qapi-event.json b/qapi-event.json
index e7a47f9..0ec20c4 100644
--- a/qapi-event.json
+++ b/qapi-event.json
@@ -315,4 +315,20 @@
 ##
 { 'event': 'QUORUM_REPORT_BAD',
   'data': { '*error': 'str', 'node-name': 'str',
             'sector-num': 'int', 'sector-count': 'int' } }
+
+##
+# @VSERPORT_CHANGE
+#
+# Emitted when the guest takes an action that changes the status of a
+# virtio-serial port (eg. opens or closes it).
+#
+# @id: device identifier of the virtio-serial port
+#
+# @status: new status of the virtio-serial port
+#
+# Since: 2.1
+##
+{ 'event': 'VSERPORT_CHANGE',
+  'data': { 'id': 'str',
+            'status': 'VirtioSerialPortStatus' } }
diff --git a/qapi-schema.json b/qapi-schema.json
index e7727a1..d1dc8be 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3398,5 +3398,21 @@
 ##
 { 'enum': 'GuestPanicAction',
   'data': [ 'pause' ] }
 
+##
+# @VirtioSerialPortStatus
+#
+# An enumeration of the possible / recognized states of virtio-serial ports.
+#
+# @connected: the virtio-serial port has been opened (connected to) in the
+#              guest.
+#
+# @disconnected: the virtio-serial port has been closed (disconnected from) in
+#                the guest.
+#
+# Since: 2.1
+##
+{ 'enum': 'VirtioSerialPortStatus',
+  'data': [ 'connected', 'disconnected' ] }
+
 { 'include': 'qapi-event.json' }
diff --git a/hw/char/virtio-console.c b/hw/char/virtio-console.c
index 6c8be0f..729faac 100644
--- a/hw/char/virtio-console.c
+++ b/hw/char/virtio-console.c
@@ -13,8 +13,9 @@
 #include "sysemu/char.h"
 #include "qemu/error-report.h"
 #include "trace.h"
 #include "hw/virtio/virtio-serial.h"
+#include "qapi-event.h"
 
 #define TYPE_VIRTIO_CONSOLE_SERIAL_PORT "virtserialport"
 #define VIRTIO_CONSOLE(obj) \
     OBJECT_CHECK(VirtConsole, (obj), TYPE_VIRTIO_CONSOLE_SERIAL_PORT)
@@ -80,13 +81,21 @@ static ssize_t flush_buf(VirtIOSerialPort *port,
 /* Callback function that's called when the guest opens/closes the port */
 static void set_guest_connected(VirtIOSerialPort *port, int guest_connected)
 {
     VirtConsole *vcon = VIRTIO_CONSOLE(port);
+    DeviceState *dev = DEVICE(port);
 
-    if (!vcon->chr) {
-        return;
+    if (vcon->chr) {
+        qemu_chr_fe_set_open(vcon->chr, guest_connected);
+    }
+
+    if (dev->id) {
+        VirtioSerialPortStatus status = guest_connected ?
+            VIRTIO_SERIAL_PORT_STATUS_CONNECTED :
+            VIRTIO_SERIAL_PORT_STATUS_DISCONNECTED;
+
+        qapi_event_send_vserport_change(dev->id, status, &error_abort);
     }
-    qemu_chr_fe_set_open(vcon->chr, guest_connected);
 }
 
 /* Readiness of the guest to accept data on a port */
 static int chr_can_read(void *opaque)
diff --git a/monitor.c b/monitor.c
index a8ab600..5fbf987 100644
--- a/monitor.c
+++ b/monitor.c
@@ -584,8 +584,9 @@ static void monitor_qapi_event_init(void)
     /* Limit guest-triggerable events to 1 per second */
     monitor_qapi_event_throttle(QAPI_EVENT_RTC_CHANGE, 1000);
     monitor_qapi_event_throttle(QAPI_EVENT_WATCHDOG, 1000);
     monitor_qapi_event_throttle(QAPI_EVENT_BALLOON_CHANGE, 1000);
+    monitor_qapi_event_throttle(QAPI_EVENT_VSERPORT_CHANGE, 1000);
     /* limit the rate of quorum events to avoid hammering the management */
     monitor_qapi_event_throttle(QAPI_EVENT_QUORUM_REPORT_BAD, 1000);
     monitor_qapi_event_throttle(QAPI_EVENT_QUORUM_FAILURE, 1000);
 
-- 
1.8.3.1