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* Virtio Serial / Console Support
* Copyright IBM, Corp. 2008
* Copyright Red Hat, Inc. 2009, 2010
* Authors:
* Christian Ehrhardt <>
* Amit Shah <>
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
#include "qdev.h"
#include "virtio.h"
/* == Interface shared between the guest kernel and qemu == */
/* The Virtio ID for virtio console / serial ports */
/* Features supported */
#define VIRTIO_CONSOLE_BAD_ID (~(uint32_t)0)
struct virtio_console_config {
* These two fields are used by VIRTIO_CONSOLE_F_SIZE which
* isn't implemented here yet
uint16_t cols;
uint16_t rows;
uint32_t max_nr_ports;
} __attribute__((packed));
struct virtio_console_control {
uint32_t id; /* Port number */
uint16_t event; /* The kind of control event (see below) */
uint16_t value; /* Extra information for the key */
struct virtio_serial_conf {
/* Max. number of ports we can have for a virtio-serial device */
uint32_t max_virtserial_ports;
/* Some events for the internal messages (control packets) */
/* == In-qemu interface == */
typedef struct VirtIOSerial VirtIOSerial;
typedef struct VirtIOSerialBus VirtIOSerialBus;
typedef struct VirtIOSerialPort VirtIOSerialPort;
typedef struct VirtIOSerialPortInfo VirtIOSerialPortInfo;
* This is the state that's shared between all the ports. Some of the
* state is configurable via command-line options. Some of it can be
* set by individual devices in their initfn routines. Some of the
* state is set by the generic qdev device init routine.
struct VirtIOSerialPort {
DeviceState dev;
QTAILQ_ENTRY(VirtIOSerialPort) next;
* This field gives us the virtio device as well as the qdev bus
* that we are associated with
VirtIOSerial *vser;
VirtQueue *ivq, *ovq;
* This name is sent to the guest and exported via sysfs.
* The guest could create symlinks based on this information.
* The name is in the reverse fqdn format, like org.qemu.console.0
char *name;
* This id helps identify ports between the guest and the host.
* The guest sends a "header" with this id with each data packet
* that it sends and the host can then find out which associated
* device to send out this data to
uint32_t id;
* This is the elem that we pop from the virtqueue. A slow
* backend that consumes guest data (e.g. the file backend for
* qemu chardevs) can cause the guest to block till all the output
* is flushed. This isn't desired, so we keep a note of the last
* element popped and continue consuming it once the backend
* becomes writable again.
VirtQueueElement elem;
* The index and the offset into the iov buffer that was popped in
* elem above.
uint32_t iov_idx;
uint64_t iov_offset;
* When unthrottling we use a bottom-half to call flush_queued_data.
/* Is the corresponding guest device open? */
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 {
DeviceInfo qdev;
/* Is this a device that binds with hvc in the guest? */
bool is_console;
* The per-port (or per-app) init function that's called when a
* new device is found on the bus.
int (*init)(VirtIOSerialPort *port);
* Per-port exit function that's called when a port gets
* hot-unplugged or removed.
int (*exit)(VirtIOSerialPort *port);
/* Callbacks for guest events */
/* Guest opened device. */
void (*guest_open)(VirtIOSerialPort *port);
/* Guest closed device. */
void (*guest_close)(VirtIOSerialPort *port);
/* Guest is now ready to accept data (virtqueues set up). */
void (*guest_ready)(VirtIOSerialPort *port);
* Guest wrote some data to the port. This data is handed over to
* the app via this callback. The app can return a size less than
* 'len'. In this case, throttling will be enabled for this port.
ssize_t (*have_data)(VirtIOSerialPort *port, const uint8_t *buf,
size_t len);
/* Interface to the virtio-serial bus */
* Individual ports/apps should call this function to register the port
* with the virtio-serial bus
void virtio_serial_port_qdev_register(VirtIOSerialPortInfo *info);
* Open a connection to the port
* Returns 0 on success (always).
int virtio_serial_open(VirtIOSerialPort *port);
* Close the connection to the port
* Returns 0 on success (always).
int virtio_serial_close(VirtIOSerialPort *port);
* Send data to Guest
ssize_t virtio_serial_write(VirtIOSerialPort *port, const uint8_t *buf,
size_t size);
* Query whether a guest is ready to receive data.
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);