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qemu/hw/char/virtio-console.c

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/*
* 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_enable_backend(VirtIOSerialPort *port, bool enable)
{
VirtConsole *vcon = VIRTIO_CONSOLE(port);
if (!qemu_chr_fe_backend_connected(&vcon->chr)) {
return;
}
if (enable) {
VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
k->is_console ? NULL : chr_event,
chr_be_change, vcon, NULL, false);
} else {
qemu_chr_fe_set_handlers(&vcon->chr, NULL, NULL, NULL,
NULL, NULL, NULL, false);
}
}
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->enable_backend = virtconsole_enable_backend;
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)
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