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.
Signed-off-by: Amit Shah <amit.s...@redhat.com> --- hw/virtio-serial-bus.c | 24 ++++++++++++++++++++++++ hw/virtio-serial.h | 9 +++++++++ 2 files changed, 33 insertions(+), 0 deletions(-) diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c index 757de7c..7b57ed8 100644 --- a/hw/virtio-serial-bus.c +++ b/hw/virtio-serial-bus.c @@ -187,6 +187,11 @@ int virtio_serial_close(VirtIOSerialPort *port) port->host_connected = false; send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN, 0); + /* + * If there's any data the guest sent which the app didn't + * consume, discard it. + */ + flush_queued_data(port, true); return 0; } @@ -226,6 +231,21 @@ size_t virtio_serial_guest_ready(VirtIOSerialPort *port) return 0; } +void virtio_serial_throttle_port(VirtIOSerialPort *port, bool throttle) +{ + if (!port) { + return; + } + + if (throttle) { + port->throttled = true; + return; + } + + port->throttled = false; + 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) { @@ -382,6 +402,10 @@ static void handle_output(VirtIODevice *vdev, VirtQueue *vq) discard = true; } + if (!discard && port->throttled) { + return; + } + flush_queued_data(port, discard); } 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