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/error.h"
  19 #include "qapi/qapi-events-char.h"
  20
  21 #define TYPE_VIRTIO_CONSOLE_SERIAL_PORT "virtserialport"
  22 #define VIRTIO_CONSOLE(obj) \
  23     OBJECT_CHECK(VirtConsole, (obj), TYPE_VIRTIO_CONSOLE_SERIAL_PORT)
  24
  25 typedef struct VirtConsole {
  26     VirtIOSerialPort parent_obj;
  27
  28     CharBackend chr;
  29     guint watch;
  30 } VirtConsole;
  31
  32 /*
  33  * Callback function that's called from chardevs when backend becomes
  34  * writable.
  35  */
  36 static gboolean chr_write_unblocked(GIOChannel *chan, GIOCondition cond,
  37                                     void *opaque)
  38 {
  39     VirtConsole *vcon = opaque;
  40
  41     vcon->watch = 0;
  42     virtio_serial_throttle_port(VIRTIO_SERIAL_PORT(vcon), false);
  43     return FALSE;
  44 }
  45
  46 /* Callback function that's called when the guest sends us data */
  47 static ssize_t flush_buf(VirtIOSerialPort *port,
  48                          const uint8_t *buf, ssize_t len)
  49 {
  50     VirtConsole *vcon = VIRTIO_CONSOLE(port);
  51     ssize_t ret;
  52
  53     if (!qemu_chr_fe_backend_connected(&vcon->chr)) {
  54         /* If there's no backend, we can just say we consumed all data. */
  55         return len;
  56     }
  57
  58     ret = qemu_chr_fe_write(&vcon->chr, buf, len);
  59     trace_virtio_console_flush_buf(port->id, len, ret);
  60
  61     if (ret < len) {
  62         VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
  63
  64         /*
  65          * Ideally we'd get a better error code than just -1, but
  66          * that's what the chardev interface gives us right now.  If
  67          * we had a finer-grained message, like -EPIPE, we could close
  68          * this connection.
  69          */
  70         if (ret < 0)
  71             ret = 0;
  72
  73         /* XXX we should be queuing data to send later for the
  74          * console devices too rather than silently dropping
  75          * console data on EAGAIN. The Linux virtio-console
  76          * hvc driver though does sends with spinlocks held,
  77          * so if we enable throttling that'll stall the entire
  78          * guest kernel, not merely the process writing to the
  79          * console.
  80          *
  81          * While we could queue data for later write without
  82          * enabling throttling, this would result in the guest
  83          * being able to trigger arbitrary memory usage in QEMU
  84          * buffering data for later writes.
  85          *
  86          * So fixing this problem likely requires fixing the
  87          * Linux virtio-console hvc driver to not hold spinlocks
  88          * while writing, and instead merely block the process
  89          * that's writing. QEMU would then need some way to detect
  90          * if the guest had the fixed driver too, before we can
  91          * use throttling on host side.
  92          */
  93         if (!k->is_console) {
  94             virtio_serial_throttle_port(port, true);
  95             if (!vcon->watch) {
  96                 vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
  97                                                     G_IO_OUT|G_IO_HUP,
  98                                                     chr_write_unblocked, vcon);
  99             }
 100         }
 101     }
 102     return ret;
 103 }
 104
 105 /* Callback function that's called when the guest opens/closes the port */
 106 static void set_guest_connected(VirtIOSerialPort *port, int guest_connected)
 107 {
 108     VirtConsole *vcon = VIRTIO_CONSOLE(port);
 109     DeviceState *dev = DEVICE(port);
 110     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
 111
 112     if (!k->is_console) {
 113         qemu_chr_fe_set_open(&vcon->chr, guest_connected);
 114     }
 115
 116     if (dev->id) {
 117         qapi_event_send_vserport_change(dev->id, guest_connected);
 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 int chr_be_change(void *opaque)
 167 {
 168     VirtConsole *vcon = opaque;
 169     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
 170     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
 171
 172     if (k->is_console) {
 173         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 174                                  NULL, chr_be_change, vcon, NULL, true);
 175     } else {
 176         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 177                                  chr_event, chr_be_change, vcon, NULL, false);
 178     }
 179
 180     if (vcon->watch) {
 181         g_source_remove(vcon->watch);
 182         vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
 183                                             G_IO_OUT | G_IO_HUP,
 184                                             chr_write_unblocked, vcon);
 185     }
 186
 187     return 0;
 188 }
 189
 190 static void virtconsole_enable_backend(VirtIOSerialPort *port, bool enable)
 191 {
 192     VirtConsole *vcon = VIRTIO_CONSOLE(port);
 193
 194     if (!qemu_chr_fe_backend_connected(&vcon->chr)) {
 195         return;
 196     }
 197
 198     if (enable) {
 199         VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
 200
 201         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 202                                  k->is_console ? NULL : chr_event,
 203                                  chr_be_change, vcon, NULL, false);
 204     } else {
 205         qemu_chr_fe_set_handlers(&vcon->chr, NULL, NULL, NULL,
 206                                  NULL, NULL, NULL, false);
 207     }
 208 }
 209
 210 static void virtconsole_realize(DeviceState *dev, Error **errp)
 211 {
 212     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(dev);
 213     VirtConsole *vcon = VIRTIO_CONSOLE(dev);
 214     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(dev);
 215
 216     if (port->id == 0 && !k->is_console) {
 217         error_setg(errp, "Port number 0 on virtio-serial devices reserved "
 218                    "for virtconsole devices for backward compatibility.");
 219         return;
 220     }
 221
 222     if (qemu_chr_fe_backend_connected(&vcon->chr)) {
 223         /*
 224          * For consoles we don't block guest data transfer just
 225          * because nothing is connected - we'll just let it go
 226          * whetherever the chardev wants - /dev/null probably.
 227          *
 228          * For serial ports we need 100% reliable data transfer
 229          * so we use the opened/closed signals from chardev to
 230          * trigger open/close of the device
 231          */
 232         if (k->is_console) {
 233             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 234                                      NULL, chr_be_change,
 235                                      vcon, NULL, true);
 236             virtio_serial_open(port);
 237         } else {
 238             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 239                                      chr_event, chr_be_change,
 240                                      vcon, NULL, false);
 241         }
 242     }
 243 }
 244
 245 static void virtconsole_unrealize(DeviceState *dev, Error **errp)
 246 {
 247     VirtConsole *vcon = VIRTIO_CONSOLE(dev);
 248
 249     if (vcon->watch) {
 250         g_source_remove(vcon->watch);
 251     }
 252 }
 253
 254 static void virtconsole_class_init(ObjectClass *klass, void *data)
 255 {
 256     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);
 257
 258     k->is_console = true;
 259 }
 260
 261 static const TypeInfo virtconsole_info = {
 262     .name          = "virtconsole",
 263     .parent        = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
 264     .class_init    = virtconsole_class_init,
 265 };
 266
 267 static Property virtserialport_properties[] = {
 268     DEFINE_PROP_CHR("chardev", VirtConsole, chr),
 269     DEFINE_PROP_END_OF_LIST(),
 270 };
 271
 272 static void virtserialport_class_init(ObjectClass *klass, void *data)
 273 {
 274     DeviceClass *dc = DEVICE_CLASS(klass);
 275     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);
 276
 277     k->realize = virtconsole_realize;
 278     k->unrealize = virtconsole_unrealize;
 279     k->have_data = flush_buf;
 280     k->set_guest_connected = set_guest_connected;
 281     k->enable_backend = virtconsole_enable_backend;
 282     k->guest_writable = guest_writable;
 283     dc->props = virtserialport_properties;
 284 }
 285
 286 static const TypeInfo virtserialport_info = {
 287     .name          = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
 288     .parent        = TYPE_VIRTIO_SERIAL_PORT,
 289     .instance_size = sizeof(VirtConsole),
 290     .class_init    = virtserialport_class_init,
 291 };
 292
 293 static void virtconsole_register_types(void)
 294 {
 295     type_register_static(&virtserialport_info);
 296     type_register_static(&virtconsole_info);
 297 }
 298
 299 type_init(virtconsole_register_types)