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virtio-serial: Implement flow control for individual ports
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.shah@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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@ -111,14 +111,14 @@ static size_t write_to_port(VirtIOSerialPort *port,
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return offset;
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}
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static void flush_queued_data(VirtIOSerialPort *port, VirtQueue *vq,
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VirtIODevice *vdev, bool discard)
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static void do_flush_queued_data(VirtIOSerialPort *port, VirtQueue *vq,
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VirtIODevice *vdev, bool discard)
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{
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VirtQueueElement elem;
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assert(port || discard);
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while (virtqueue_pop(vq, &elem)) {
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while ((discard || !port->throttled) && virtqueue_pop(vq, &elem)) {
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uint8_t *buf;
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size_t ret, buf_size;
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@ -135,6 +135,13 @@ static void flush_queued_data(VirtIOSerialPort *port, VirtQueue *vq,
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virtio_notify(vdev, vq);
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}
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static void flush_queued_data(VirtIOSerialPort *port, bool discard)
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{
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assert(port || discard);
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do_flush_queued_data(port, port->ovq, &port->vser->vdev, discard);
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}
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static size_t send_control_msg(VirtIOSerialPort *port, void *buf, size_t len)
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{
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VirtQueueElement elem;
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@ -186,6 +193,13 @@ int virtio_serial_open(VirtIOSerialPort *port)
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int virtio_serial_close(VirtIOSerialPort *port)
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{
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port->host_connected = false;
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/*
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* If there's any data the guest sent which the app didn't
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* consume, reset the throttling flag and discard the data.
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*/
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port->throttled = false;
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flush_queued_data(port, true);
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send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN, 0);
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return 0;
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@ -227,6 +241,20 @@ size_t virtio_serial_guest_ready(VirtIOSerialPort *port)
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return 0;
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}
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void virtio_serial_throttle_port(VirtIOSerialPort *port, bool throttle)
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{
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if (!port) {
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return;
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}
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port->throttled = throttle;
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if (throttle) {
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return;
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}
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flush_queued_data(port, false);
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}
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/* Guest wants to notify us of some event */
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static void handle_control_message(VirtIOSerial *vser, void *buf, size_t len)
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{
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@ -380,7 +408,11 @@ static void handle_output(VirtIODevice *vdev, VirtQueue *vq)
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discard = true;
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}
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flush_queued_data(port, vq, vdev, discard);
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if (!discard && port->throttled) {
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return;
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}
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do_flush_queued_data(port, vq, vdev, discard);
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}
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static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
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@ -555,6 +587,8 @@ static void virtser_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent)
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indent, "", port->guest_connected);
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monitor_printf(mon, "%*s dev-prop-int: host_connected: %d\n",
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indent, "", port->host_connected);
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monitor_printf(mon, "%*s dev-prop-int: throttled: %d\n",
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indent, "", port->throttled);
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}
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/* This function is only used if a port id is not provided by the user */
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@ -592,13 +626,17 @@ static void add_port(VirtIOSerial *vser, uint32_t port_id)
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static void remove_port(VirtIOSerial *vser, uint32_t port_id)
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{
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VirtIOSerialPort *port;
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unsigned int i;
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i = port_id / 32;
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vser->ports_map[i] &= ~(1U << (port_id % 32));
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send_control_event(find_port_by_id(vser, port_id),
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VIRTIO_CONSOLE_PORT_REMOVE, 1);
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port = find_port_by_id(vser, port_id);
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/* Flush out any unconsumed buffers first */
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flush_queued_data(port, true);
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send_control_event(port, VIRTIO_CONSOLE_PORT_REMOVE, 1);
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}
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static int virtser_port_qdev_init(DeviceState *qdev, DeviceInfo *base)
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@ -110,6 +110,8 @@ struct VirtIOSerialPort {
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bool guest_connected;
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/* Is this device open for IO on the host? */
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bool host_connected;
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/* Do apps not want to receive data? */
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bool throttled;
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};
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struct VirtIOSerialPortInfo {
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@ -173,4 +175,11 @@ ssize_t virtio_serial_write(VirtIOSerialPort *port, const uint8_t *buf,
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*/
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size_t virtio_serial_guest_ready(VirtIOSerialPort *port);
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/*
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* Flow control: Ports can signal to the virtio-serial core to stop
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* sending data or re-start sending data, depending on the 'throttle'
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* value here.
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*/
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void virtio_serial_throttle_port(VirtIOSerialPort *port, bool throttle);
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#endif
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