Individual ports can now signal to the virtio-serial core to stop
sending data if the ports cannot immediately handle new data. When a
port later unthrottles, any data queued up in the virtqueue are sent to
the port.
Disable throttling once a port is closed (and we discard all the
unconsumed buffers in the vq).
The guest kernel can reclaim the buffers when it receives the port close
event or when a port is being removed. Ensure we free up the buffers
before we send out any events to the guest.
Signed-off-by: Amit Shah <amit.s...@redhat.com>
---
hw/virtio-serial-bus.c | 37 ++++++++++++++++++++++++++++++++++---
hw/virtio-serial.h | 9 +++++++++
2 files changed, 43 insertions(+), 3 deletions(-)
diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
index 0166780..de64154 100644
--- a/hw/virtio-serial-bus.c
+++ b/hw/virtio-serial-bus.c
@@ -117,7 +117,7 @@ static void flush_queued_data(VirtIOSerialPort *port, bool
discard)
VirtQueueElement elem;
vq = port->ovq;
- while (virtqueue_pop(vq, &elem)) {
+ while ((discard || !port->throttled) && virtqueue_pop(vq, &elem)) {
uint8_t *buf;
size_t ret, buf_size;
@@ -185,6 +185,13 @@ int virtio_serial_open(VirtIOSerialPort *port)
int virtio_serial_close(VirtIOSerialPort *port)
{
port->host_connected = false;
+ /*
+ * If there's any data the guest sent which the app didn't
+ * consume, reset the throttling flag and discard the data.
+ */
+ port->throttled = false;
+ flush_queued_data(port, true);
+
send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN, 0);
return 0;
@@ -226,6 +233,20 @@ size_t virtio_serial_guest_ready(VirtIOSerialPort *port)
return 0;
}
+void virtio_serial_throttle_port(VirtIOSerialPort *port, bool throttle)
+{
+ if (!port) {
+ return;
+ }
+
+ port->throttled = throttle;
+ if (throttle) {
+ return;
+ }
+
+ flush_queued_data(port, false);
+}
+
/* Guest wants to notify us of some event */
static void handle_control_message(VirtIOSerial *vser, void *buf, size_t len)
{
@@ -379,6 +400,10 @@ static void handle_output(VirtIODevice *vdev, VirtQueue
*vq)
discard = true;
}
+ if (!discard && port->throttled) {
+ return;
+ }
+
flush_queued_data(port, discard);
}
@@ -554,6 +579,8 @@ static void virtser_bus_dev_print(Monitor *mon, DeviceState
*qdev, int indent)
indent, "", port->guest_connected);
monitor_printf(mon, "%*s dev-prop-int: host_connected: %d\n",
indent, "", port->host_connected);
+ monitor_printf(mon, "%*s dev-prop-int: throttled: %d\n",
+ indent, "", port->throttled);
}
/* This function is only used if a port id is not provided by the user */
@@ -591,13 +618,17 @@ static void add_port(VirtIOSerial *vser, uint32_t port_id)
static void remove_port(VirtIOSerial *vser, uint32_t port_id)
{
+ VirtIOSerialPort *port;
unsigned int i;
i = port_id / 32;
vser->ports_map[i] &= ~(1U << (port_id % 32));
- send_control_event(find_port_by_id(vser, port_id),
- VIRTIO_CONSOLE_PORT_REMOVE, 1);
+ port = find_port_by_id(vser, port_id);
+ /* Flush out any unconsumed buffers first */
+ flush_queued_data(port, true);
+
+ send_control_event(port, VIRTIO_CONSOLE_PORT_REMOVE, 1);
}
static int virtser_port_qdev_init(DeviceState *qdev, DeviceInfo *base)
diff --git a/hw/virtio-serial.h b/hw/virtio-serial.h
index 62d76a2..a93b545 100644
--- a/hw/virtio-serial.h
+++ b/hw/virtio-serial.h
@@ -110,6 +110,8 @@ struct VirtIOSerialPort {
bool guest_connected;
/* Is this device open for IO on the host? */
bool host_connected;
+ /* Do apps not want to receive data? */
+ bool throttled;
};
struct VirtIOSerialPortInfo {
@@ -173,4 +175,11 @@ ssize_t virtio_serial_write(VirtIOSerialPort *port, const
uint8_t *buf,
*/
size_t virtio_serial_guest_ready(VirtIOSerialPort *port);
+/*
+ * Flow control: Ports can signal to the virtio-serial core to stop
+ * sending data or re-start sending data, depending on the 'throttle'
+ * value here.
+ */
+void virtio_serial_throttle_port(VirtIOSerialPort *port, bool throttle);
+
#endif
--
1.6.2.5
