hw/char/virtio-console.c

   1 /*
   2  * Virtio Console and Generic Serial Port Devices
   3  *
   4  * Copyright Red Hat, Inc. 2009, 2010
   5  *
   6  * Authors:
   7  *  Amit Shah <amit.shah@redhat.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  */
  12
  13 #include "qemu/osdep.h"
  14 #include "chardev/char-fe.h"
  15 #include "qemu/error-report.h"
  16 #include "trace.h"
  17 #include "hw/virtio/virtio-serial.h"
  18 #include "qapi-event.h"
  19
  20 #define TYPE_VIRTIO_CONSOLE_SERIAL_PORT "virtserialport"
  21 #define VIRTIO_CONSOLE(obj) \
  22     OBJECT_CHECK(VirtConsole, (obj), TYPE_VIRTIO_CONSOLE_SERIAL_PORT)
  23
  24 typedef struct VirtConsole {
  25     VirtIOSerialPort parent_obj;
  26
  27     CharBackend chr;
  28     guint watch;
  29 } VirtConsole;
  30
  31 /*
  32  * Callback function that's called from chardevs when backend becomes
  33  * writable.
  34  */
  35 static gboolean chr_write_unblocked(GIOChannel *chan, GIOCondition cond,
  36                                     void *opaque)
  37 {
  38     VirtConsole *vcon = opaque;
  39
  40     vcon->watch = 0;
  41     virtio_serial_throttle_port(VIRTIO_SERIAL_PORT(vcon), false);
  42     return FALSE;
  43 }
  44
  45 /* Callback function that's called when the guest sends us data */
  46 static ssize_t flush_buf(VirtIOSerialPort *port,
  47                          const uint8_t *buf, ssize_t len)
  48 {
  49     VirtConsole *vcon = VIRTIO_CONSOLE(port);
  50     ssize_t ret;
  51
  52     if (!qemu_chr_fe_get_driver(&vcon->chr)) {
  53         /* If there's no backend, we can just say we consumed all data. */
  54         return len;
  55     }
  56
  57     ret = qemu_chr_fe_write(&vcon->chr, buf, len);
  58     trace_virtio_console_flush_buf(port->id, len, ret);
  59
  60     if (ret < len) {
  61         VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
  62
  63         /*
  64          * Ideally we'd get a better error code than just -1, but
  65          * that's what the chardev interface gives us right now.  If
  66          * we had a finer-grained message, like -EPIPE, we could close
  67          * this connection.
  68          */
  69         if (ret < 0)
  70             ret = 0;
  71
  72         /* XXX we should be queuing data to send later for the
  73          * console devices too rather than silently dropping
  74          * console data on EAGAIN. The Linux virtio-console
  75          * hvc driver though does sends with spinlocks held,
  76          * so if we enable throttling that'll stall the entire
  77          * guest kernel, not merely the process writing to the
  78          * console.
  79          *
  80          * While we could queue data for later write without
  81          * enabling throttling, this would result in the guest
  82          * being able to trigger arbitrary memory usage in QEMU
  83          * buffering data for later writes.
  84          *
  85          * So fixing this problem likely requires fixing the
  86          * Linux virtio-console hvc driver to not hold spinlocks
  87          * while writing, and instead merely block the process
  88          * that's writing. QEMU would then need some way to detect
  89          * if the guest had the fixed driver too, before we can
  90          * use throttling on host side.
  91          */
  92         if (!k->is_console) {
  93             virtio_serial_throttle_port(port, true);
  94             if (!vcon->watch) {
  95                 vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
  96                                                     G_IO_OUT|G_IO_HUP,
  97                                                     chr_write_unblocked, vcon);
  98             }
  99         }
 100     }
 101     return ret;
 102 }
 103
 104 /* Callback function that's called when the guest opens/closes the port */
 105 static void set_guest_connected(VirtIOSerialPort *port, int guest_connected)
 106 {
 107     VirtConsole *vcon = VIRTIO_CONSOLE(port);
 108     DeviceState *dev = DEVICE(port);
 109     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
 110
 111     if (!k->is_console) {
 112         qemu_chr_fe_set_open(&vcon->chr, guest_connected);
 113     }
 114
 115     if (dev->id) {
 116         qapi_event_send_vserport_change(dev->id, guest_connected,
 117                                         &error_abort);
 118     }
 119 }
 120
 121 static void guest_writable(VirtIOSerialPort *port)
 122 {
 123     VirtConsole *vcon = VIRTIO_CONSOLE(port);
 124
 125     qemu_chr_fe_accept_input(&vcon->chr);
 126 }
 127
 128 /* Readiness of the guest to accept data on a port */
 129 static int chr_can_read(void *opaque)
 130 {
 131     VirtConsole *vcon = opaque;
 132
 133     return virtio_serial_guest_ready(VIRTIO_SERIAL_PORT(vcon));
 134 }
 135
 136 /* Send data from a char device over to the guest */
 137 static void chr_read(void *opaque, const uint8_t *buf, int size)
 138 {
 139     VirtConsole *vcon = opaque;
 140     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
 141
 142     trace_virtio_console_chr_read(port->id, size);
 143     virtio_serial_write(port, buf, size);
 144 }
 145
 146 static void chr_event(void *opaque, int event)
 147 {
 148     VirtConsole *vcon = opaque;
 149     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
 150
 151     trace_virtio_console_chr_event(port->id, event);
 152     switch (event) {
 153     case CHR_EVENT_OPENED:
 154         virtio_serial_open(port);
 155         break;
 156     case CHR_EVENT_CLOSED:
 157         if (vcon->watch) {
 158             g_source_remove(vcon->watch);
 159             vcon->watch = 0;
 160         }
 161         virtio_serial_close(port);
 162         break;
 163     }
 164 }
 165
 166 static void virtconsole_realize(DeviceState *dev, Error **errp)
 167 {
 168     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(dev);
 169     VirtConsole *vcon = VIRTIO_CONSOLE(dev);
 170     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(dev);
 171     Chardev *chr = qemu_chr_fe_get_driver(&vcon->chr);
 172
 173     if (port->id == 0 && !k->is_console) {
 174         error_setg(errp, "Port number 0 on virtio-serial devices reserved "
 175                    "for virtconsole devices for backward compatibility.");
 176         return;
 177     }
 178
 179     if (chr) {
 180         /*
 181          * For consoles we don't block guest data transfer just
 182          * because nothing is connected - we'll just let it go
 183          * whetherever the chardev wants - /dev/null probably.
 184          *
 185          * For serial ports we need 100% reliable data transfer
 186          * so we use the opened/closed signals from chardev to
 187          * trigger open/close of the device
 188          */
 189         if (k->is_console) {
 190             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 191                                      NULL, vcon, NULL, true);
 192             virtio_serial_open(port);
 193         } else {
 194             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 195                                      chr_event, vcon, NULL, false);
 196         }
 197     }
 198 }
 199
 200 static void virtconsole_unrealize(DeviceState *dev, Error **errp)
 201 {
 202     VirtConsole *vcon = VIRTIO_CONSOLE(dev);
 203
 204     if (vcon->watch) {
 205         g_source_remove(vcon->watch);
 206     }
 207 }
 208
 209 static void virtconsole_class_init(ObjectClass *klass, void *data)
 210 {
 211     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);
 212
 213     k->is_console = true;
 214 }
 215
 216 static const TypeInfo virtconsole_info = {
 217     .name          = "virtconsole",
 218     .parent        = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
 219     .class_init    = virtconsole_class_init,
 220 };
 221
 222 static Property virtserialport_properties[] = {
 223     DEFINE_PROP_CHR("chardev", VirtConsole, chr),
 224     DEFINE_PROP_END_OF_LIST(),
 225 };
 226
 227 static void virtserialport_class_init(ObjectClass *klass, void *data)
 228 {
 229     DeviceClass *dc = DEVICE_CLASS(klass);
 230     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);
 231
 232     k->realize = virtconsole_realize;
 233     k->unrealize = virtconsole_unrealize;
 234     k->have_data = flush_buf;
 235     k->set_guest_connected = set_guest_connected;
 236     k->guest_writable = guest_writable;
 237     dc->props = virtserialport_properties;
 238 }
 239
 240 static const TypeInfo virtserialport_info = {
 241     .name          = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
 242     .parent        = TYPE_VIRTIO_SERIAL_PORT,
 243     .instance_size = sizeof(VirtConsole),
 244     .class_init    = virtserialport_class_init,
 245 };
 246
 247 static void virtconsole_register_types(void)
 248 {
 249     type_register_static(&virtserialport_info);
 250     type_register_static(&virtconsole_info);
 251 }
 252
 253 type_init(virtconsole_register_types)