hw/char/virtio-console.c - qemu - Git at Google

 /*
  * Virtio Console and Generic Serial Port Devices
  *
  * Copyright Red Hat, Inc. 2009, 2010
  *
  * Authors:
  *  Amit Shah <amit.shah@redhat.com>
  *
  * This work is licensed under the terms of the GNU GPL, version 2.  See
  * the COPYING file in the top-level directory.
  */

 #include "qemu/osdep.h"
 #include "chardev/char-fe.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)

 typedef struct VirtConsole {
     VirtIOSerialPort parent_obj;

     CharBackend chr;
     guint watch;
 } VirtConsole;

 /*
  * Callback function that's called from chardevs when backend becomes
  * writable.
  */
 static gboolean chr_write_unblocked(GIOChannel *chan, GIOCondition cond,
                                     void *opaque)
 {
     VirtConsole *vcon = opaque;

     vcon->watch = 0;
     virtio_serial_throttle_port(VIRTIO_SERIAL_PORT(vcon), false);
     return FALSE;
 }

 /* Callback function that's called when the guest sends us data */
 static ssize_t flush_buf(VirtIOSerialPort *port,
                          const uint8_t *buf, ssize_t len)
 {
     VirtConsole *vcon = VIRTIO_CONSOLE(port);
     ssize_t ret;

     if (!qemu_chr_fe_backend_connected(&vcon->chr)) {
         /* If there's no backend, we can just say we consumed all data. */
         return len;
     }

     ret = qemu_chr_fe_write(&vcon->chr, buf, len);
     trace_virtio_console_flush_buf(port->id, len, ret);

     if (ret < len) {
         VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);

         /*
          * Ideally we'd get a better error code than just -1, but
          * that's what the chardev interface gives us right now.  If
          * we had a finer-grained message, like -EPIPE, we could close
          * this connection.
          */
         if (ret < 0)
             ret = 0;

         /* XXX we should be queuing data to send later for the
          * console devices too rather than silently dropping
          * console data on EAGAIN. The Linux virtio-console
          * hvc driver though does sends with spinlocks held,
          * so if we enable throttling that'll stall the entire
          * guest kernel, not merely the process writing to the
          * console.
          *
          * While we could queue data for later write without
          * enabling throttling, this would result in the guest
          * being able to trigger arbitrary memory usage in QEMU
          * buffering data for later writes.
          *
          * So fixing this problem likely requires fixing the
          * Linux virtio-console hvc driver to not hold spinlocks
          * while writing, and instead merely block the process
          * that's writing. QEMU would then need some way to detect
          * if the guest had the fixed driver too, before we can
          * use throttling on host side.
          */
         if (!k->is_console) {
             virtio_serial_throttle_port(port, true);
             if (!vcon->watch) {
                 vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
                                                     G_IO_OUT|G_IO_HUP,
                                                     chr_write_unblocked, vcon);
             }
         }
     }
     return ret;
 }

 /* 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);
     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);

     if (!k->is_console) {
         qemu_chr_fe_set_open(&vcon->chr, guest_connected);
     }

     if (dev->id) {
         qapi_event_send_vserport_change(dev->id, guest_connected,
                                         &error_abort);
     }
 }

 static void guest_writable(VirtIOSerialPort *port)
 {
     VirtConsole *vcon = VIRTIO_CONSOLE(port);

     qemu_chr_fe_accept_input(&vcon->chr);
 }

 /* Readiness of the guest to accept data on a port */
 static int chr_can_read(void *opaque)
 {
     VirtConsole *vcon = opaque;

     return virtio_serial_guest_ready(VIRTIO_SERIAL_PORT(vcon));
 }

 /* Send data from a char device over to the guest */
 static void chr_read(void *opaque, const uint8_t *buf, int size)
 {
     VirtConsole *vcon = opaque;
     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);

     trace_virtio_console_chr_read(port->id, size);
     virtio_serial_write(port, buf, size);
 }

 static void chr_event(void *opaque, int event)
 {
     VirtConsole *vcon = opaque;
     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);

     trace_virtio_console_chr_event(port->id, event);
     switch (event) {
     case CHR_EVENT_OPENED:
         virtio_serial_open(port);
         break;
     case CHR_EVENT_CLOSED:
         if (vcon->watch) {
             g_source_remove(vcon->watch);
             vcon->watch = 0;
         }
         virtio_serial_close(port);
         break;
     }
 }

 static int chr_be_change(void *opaque)
 {
     VirtConsole *vcon = opaque;
     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);

     if (k->is_console) {
         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
                                  NULL, chr_be_change, vcon, NULL, true);
     } else {
         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
                                  chr_event, chr_be_change, vcon, NULL, false);
     }

     if (vcon->watch) {
         g_source_remove(vcon->watch);
         vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
                                             G_IO_OUT | G_IO_HUP,
                                             chr_write_unblocked, vcon);
     }

     return 0;
 }

 static void virtconsole_realize(DeviceState *dev, Error **errp)
 {
     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(dev);
     VirtConsole *vcon = VIRTIO_CONSOLE(dev);
     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(dev);

     if (port->id == 0 && !k->is_console) {
         error_setg(errp, "Port number 0 on virtio-serial devices reserved "
                    "for virtconsole devices for backward compatibility.");
         return;
     }

     if (qemu_chr_fe_backend_connected(&vcon->chr)) {
         /*
          * For consoles we don't block guest data transfer just
          * because nothing is connected - we'll just let it go
          * whetherever the chardev wants - /dev/null probably.
          *
          * For serial ports we need 100% reliable data transfer
          * so we use the opened/closed signals from chardev to
          * trigger open/close of the device
          */
         if (k->is_console) {
             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
                                      NULL, chr_be_change,
                                      vcon, NULL, true);
             virtio_serial_open(port);
         } else {
             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
                                      chr_event, chr_be_change,
                                      vcon, NULL, false);
         }
     }
 }

 static void virtconsole_unrealize(DeviceState *dev, Error **errp)
 {
     VirtConsole *vcon = VIRTIO_CONSOLE(dev);

     if (vcon->watch) {
         g_source_remove(vcon->watch);
     }
 }

 static void virtconsole_class_init(ObjectClass *klass, void *data)
 {
     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);

     k->is_console = true;
 }

 static const TypeInfo virtconsole_info = {
     .name          = "virtconsole",
     .parent        = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
     .class_init    = virtconsole_class_init,
 };

 static Property virtserialport_properties[] = {
     DEFINE_PROP_CHR("chardev", VirtConsole, chr),
     DEFINE_PROP_END_OF_LIST(),
 };

 static void virtserialport_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);

     k->realize = virtconsole_realize;
     k->unrealize = virtconsole_unrealize;
     k->have_data = flush_buf;
     k->set_guest_connected = set_guest_connected;
     k->guest_writable = guest_writable;
     dc->props = virtserialport_properties;
 }

 static const TypeInfo virtserialport_info = {
     .name          = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
     .parent        = TYPE_VIRTIO_SERIAL_PORT,
     .instance_size = sizeof(VirtConsole),
     .class_init    = virtserialport_class_init,
 };

 static void virtconsole_register_types(void)
 {
     type_register_static(&virtserialport_info);
     type_register_static(&virtconsole_info);
 }

 type_init(virtconsole_register_types)
	/*
	* Virtio Console and Generic Serial Port Devices
	*
	* Copyright Red Hat, Inc. 2009, 2010
	*
	* Authors:
	* Amit Shah <amit.shah@redhat.com>
	*
	* This work is licensed under the terms of the GNU GPL, version 2. See
	* the COPYING file in the top-level directory.
	*/

	#include "qemu/osdep.h"
	#include "chardev/char-fe.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)

	typedef struct VirtConsole {
	VirtIOSerialPort parent_obj;

	CharBackend chr;
	guint watch;
	} VirtConsole;

	/*
	* Callback function that's called from chardevs when backend becomes
	* writable.
	*/
	static gboolean chr_write_unblocked(GIOChannel *chan, GIOCondition cond,
	void *opaque)
	{
	VirtConsole *vcon = opaque;

	vcon->watch = 0;
	virtio_serial_throttle_port(VIRTIO_SERIAL_PORT(vcon), false);
	return FALSE;
	}

	/* Callback function that's called when the guest sends us data */
	static ssize_t flush_buf(VirtIOSerialPort *port,
	const uint8_t *buf, ssize_t len)
	{
	VirtConsole *vcon = VIRTIO_CONSOLE(port);
	ssize_t ret;

	if (!qemu_chr_fe_backend_connected(&vcon->chr)) {
	/* If there's no backend, we can just say we consumed all data. */
	return len;
	}

	ret = qemu_chr_fe_write(&vcon->chr, buf, len);
	trace_virtio_console_flush_buf(port->id, len, ret);

	if (ret < len) {
	VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);

	/*
	* Ideally we'd get a better error code than just -1, but
	* that's what the chardev interface gives us right now. If
	* we had a finer-grained message, like -EPIPE, we could close
	* this connection.
	*/
	if (ret < 0)
	ret = 0;

	/* XXX we should be queuing data to send later for the
	* console devices too rather than silently dropping
	* console data on EAGAIN. The Linux virtio-console
	* hvc driver though does sends with spinlocks held,
	* so if we enable throttling that'll stall the entire
	* guest kernel, not merely the process writing to the
	* console.
	*
	* While we could queue data for later write without
	* enabling throttling, this would result in the guest
	* being able to trigger arbitrary memory usage in QEMU
	* buffering data for later writes.
	*
	* So fixing this problem likely requires fixing the
	* Linux virtio-console hvc driver to not hold spinlocks
	* while writing, and instead merely block the process
	* that's writing. QEMU would then need some way to detect
	* if the guest had the fixed driver too, before we can
	* use throttling on host side.
	*/
	if (!k->is_console) {
	virtio_serial_throttle_port(port, true);
	if (!vcon->watch) {
	vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
	G_IO_OUT\|G_IO_HUP,
	chr_write_unblocked, vcon);
	}
	}
	}
	return ret;
	}

	/* 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);
	VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);

	if (!k->is_console) {
	qemu_chr_fe_set_open(&vcon->chr, guest_connected);
	}

	if (dev->id) {
	qapi_event_send_vserport_change(dev->id, guest_connected,
	&error_abort);
	}
	}

	static void guest_writable(VirtIOSerialPort *port)
	{
	VirtConsole *vcon = VIRTIO_CONSOLE(port);

	qemu_chr_fe_accept_input(&vcon->chr);
	}

	/* Readiness of the guest to accept data on a port */
	static int chr_can_read(void *opaque)
	{
	VirtConsole *vcon = opaque;

	return virtio_serial_guest_ready(VIRTIO_SERIAL_PORT(vcon));
	}

	/* Send data from a char device over to the guest */
	static void chr_read(void opaque, const uint8_t buf, int size)
	{
	VirtConsole *vcon = opaque;
	VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);

	trace_virtio_console_chr_read(port->id, size);
	virtio_serial_write(port, buf, size);
	}

	static void chr_event(void *opaque, int event)
	{
	VirtConsole *vcon = opaque;
	VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);

	trace_virtio_console_chr_event(port->id, event);
	switch (event) {
	case CHR_EVENT_OPENED:
	virtio_serial_open(port);
	break;
	case CHR_EVENT_CLOSED:
	if (vcon->watch) {
	g_source_remove(vcon->watch);
	vcon->watch = 0;
	}
	virtio_serial_close(port);
	break;
	}
	}

	static int chr_be_change(void *opaque)
	{
	VirtConsole *vcon = opaque;
	VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
	VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);

	if (k->is_console) {
	qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
	NULL, chr_be_change, vcon, NULL, true);
	} else {
	qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
	chr_event, chr_be_change, vcon, NULL, false);
	}

	if (vcon->watch) {
	g_source_remove(vcon->watch);
	vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
	G_IO_OUT \| G_IO_HUP,
	chr_write_unblocked, vcon);
	}

	return 0;
	}

	static void virtconsole_realize(DeviceState dev, Error *errp)
	{
	VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(dev);
	VirtConsole *vcon = VIRTIO_CONSOLE(dev);
	VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(dev);

	if (port->id == 0 && !k->is_console) {
	error_setg(errp, "Port number 0 on virtio-serial devices reserved "
	"for virtconsole devices for backward compatibility.");
	return;
	}

	if (qemu_chr_fe_backend_connected(&vcon->chr)) {
	/*
	* For consoles we don't block guest data transfer just
	* because nothing is connected - we'll just let it go
	* whetherever the chardev wants - /dev/null probably.
	*
	* For serial ports we need 100% reliable data transfer
	* so we use the opened/closed signals from chardev to
	* trigger open/close of the device
	*/
	if (k->is_console) {
	qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
	NULL, chr_be_change,
	vcon, NULL, true);
	virtio_serial_open(port);
	} else {
	qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
	chr_event, chr_be_change,
	vcon, NULL, false);
	}
	}
	}

	static void virtconsole_unrealize(DeviceState dev, Error *errp)
	{
	VirtConsole *vcon = VIRTIO_CONSOLE(dev);

	if (vcon->watch) {
	g_source_remove(vcon->watch);
	}
	}

	static void virtconsole_class_init(ObjectClass klass, void data)
	{
	VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);

	k->is_console = true;
	}

	static const TypeInfo virtconsole_info = {
	.name = "virtconsole",
	.parent = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
	.class_init = virtconsole_class_init,
	};

	static Property virtserialport_properties[] = {
	DEFINE_PROP_CHR("chardev", VirtConsole, chr),
	DEFINE_PROP_END_OF_LIST(),
	};

	static void virtserialport_class_init(ObjectClass klass, void data)
	{
	DeviceClass *dc = DEVICE_CLASS(klass);
	VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);

	k->realize = virtconsole_realize;
	k->unrealize = virtconsole_unrealize;
	k->have_data = flush_buf;
	k->set_guest_connected = set_guest_connected;
	k->guest_writable = guest_writable;
	dc->props = virtserialport_properties;
	}

	static const TypeInfo virtserialport_info = {
	.name = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
	.parent = TYPE_VIRTIO_SERIAL_PORT,
	.instance_size = sizeof(VirtConsole),
	.class_init = virtserialport_class_init,
	};

	static void virtconsole_register_types(void)
	{
	type_register_static(&virtserialport_info);
	type_register_static(&virtconsole_info);
	}

	type_init(virtconsole_register_types)