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 "qemu/module.h"
  17 #include "trace.h"
  18 #include "hw/qdev-properties.h"
  19 #include "hw/qdev-properties-system.h"
  20 #include "hw/virtio/virtio-serial.h"
  21 #include "qapi/error.h"
  22 #include "qapi/qapi-events-char.h"
  23 #include "qom/object.h"
  24
  25 #define TYPE_VIRTIO_CONSOLE_SERIAL_PORT "virtserialport"
  26 typedef struct VirtConsole VirtConsole;
  27 DECLARE_INSTANCE_CHECKER(VirtConsole, VIRTIO_CONSOLE,
  28                          TYPE_VIRTIO_CONSOLE_SERIAL_PORT)
  29
  30 struct VirtConsole {
  31     VirtIOSerialPort parent_obj;
  32
  33     CharBackend chr;
  34     guint watch;
  35 };
  36
  37 /*
  38  * Callback function that's called from chardevs when backend becomes
  39  * writable.
  40  */
  41 static gboolean chr_write_unblocked(void *do_not_use, GIOCondition cond,
  42                                     void *opaque)
  43 {
  44     VirtConsole *vcon = opaque;
  45
  46     vcon->watch = 0;
  47     virtio_serial_throttle_port(VIRTIO_SERIAL_PORT(vcon), false);
  48     return FALSE;
  49 }
  50
  51 /* Callback function that's called when the guest sends us data */
  52 static ssize_t flush_buf(VirtIOSerialPort *port,
  53                          const uint8_t *buf, ssize_t len)
  54 {
  55     VirtConsole *vcon = VIRTIO_CONSOLE(port);
  56     ssize_t ret;
  57
  58     if (!qemu_chr_fe_backend_connected(&vcon->chr)) {
  59         /* If there's no backend, we can just say we consumed all data. */
  60         return len;
  61     }
  62
  63     ret = qemu_chr_fe_write(&vcon->chr, buf, len);
  64     trace_virtio_console_flush_buf(port->id, len, ret);
  65
  66     if (ret < len) {
  67         VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
  68
  69         /*
  70          * Ideally we'd get a better error code than just -1, but
  71          * that's what the chardev interface gives us right now.  If
  72          * we had a finer-grained message, like -EPIPE, we could close
  73          * this connection.
  74          */
  75         if (ret < 0)
  76             ret = 0;
  77
  78         /* XXX we should be queuing data to send later for the
  79          * console devices too rather than silently dropping
  80          * console data on EAGAIN. The Linux virtio-console
  81          * hvc driver though does sends with spinlocks held,
  82          * so if we enable throttling that'll stall the entire
  83          * guest kernel, not merely the process writing to the
  84          * console.
  85          *
  86          * While we could queue data for later write without
  87          * enabling throttling, this would result in the guest
  88          * being able to trigger arbitrary memory usage in QEMU
  89          * buffering data for later writes.
  90          *
  91          * So fixing this problem likely requires fixing the
  92          * Linux virtio-console hvc driver to not hold spinlocks
  93          * while writing, and instead merely block the process
  94          * that's writing. QEMU would then need some way to detect
  95          * if the guest had the fixed driver too, before we can
  96          * use throttling on host side.
  97          */
  98         if (!k->is_console) {
  99             virtio_serial_throttle_port(port, true);
 100             if (!vcon->watch) {
 101                 vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
 102                                                     G_IO_OUT|G_IO_HUP,
 103                                                     chr_write_unblocked, vcon);
 104             }
 105         }
 106     }
 107     return ret;
 108 }
 109
 110 /* Callback function that's called when the guest opens/closes the port */
 111 static void set_guest_connected(VirtIOSerialPort *port, int guest_connected)
 112 {
 113     VirtConsole *vcon = VIRTIO_CONSOLE(port);
 114     DeviceState *dev = DEVICE(port);
 115     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
 116
 117     if (!k->is_console) {
 118         qemu_chr_fe_set_open(&vcon->chr, guest_connected);
 119     }
 120
 121     if (dev->id) {
 122         qapi_event_send_vserport_change(dev->id, guest_connected);
 123     }
 124 }
 125
 126 static void guest_writable(VirtIOSerialPort *port)
 127 {
 128     VirtConsole *vcon = VIRTIO_CONSOLE(port);
 129
 130     qemu_chr_fe_accept_input(&vcon->chr);
 131 }
 132
 133 /* Readiness of the guest to accept data on a port */
 134 static int chr_can_read(void *opaque)
 135 {
 136     VirtConsole *vcon = opaque;
 137
 138     return virtio_serial_guest_ready(VIRTIO_SERIAL_PORT(vcon));
 139 }
 140
 141 /* Send data from a char device over to the guest */
 142 static void chr_read(void *opaque, const uint8_t *buf, int size)
 143 {
 144     VirtConsole *vcon = opaque;
 145     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
 146
 147     trace_virtio_console_chr_read(port->id, size);
 148     virtio_serial_write(port, buf, size);
 149 }
 150
 151 static void chr_event(void *opaque, QEMUChrEvent event)
 152 {
 153     VirtConsole *vcon = opaque;
 154     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
 155
 156     trace_virtio_console_chr_event(port->id, event);
 157     switch (event) {
 158     case CHR_EVENT_OPENED:
 159         virtio_serial_open(port);
 160         break;
 161     case CHR_EVENT_CLOSED:
 162         if (vcon->watch) {
 163             g_source_remove(vcon->watch);
 164             vcon->watch = 0;
 165         }
 166         virtio_serial_close(port);
 167         break;
 168     case CHR_EVENT_BREAK:
 169     case CHR_EVENT_MUX_IN:
 170     case CHR_EVENT_MUX_OUT:
 171         /* Ignore */
 172         break;
 173     }
 174 }
 175
 176 static int chr_be_change(void *opaque)
 177 {
 178     VirtConsole *vcon = opaque;
 179     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
 180     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
 181
 182     if (k->is_console) {
 183         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 184                                  NULL, chr_be_change, vcon, NULL, true);
 185     } else {
 186         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 187                                  chr_event, chr_be_change, vcon, NULL, false);
 188     }
 189
 190     if (vcon->watch) {
 191         g_source_remove(vcon->watch);
 192         vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
 193                                             G_IO_OUT | G_IO_HUP,
 194                                             chr_write_unblocked, vcon);
 195     }
 196
 197     return 0;
 198 }
 199
 200 static void virtconsole_enable_backend(VirtIOSerialPort *port, bool enable)
 201 {
 202     VirtConsole *vcon = VIRTIO_CONSOLE(port);
 203
 204     if (!qemu_chr_fe_backend_connected(&vcon->chr)) {
 205         return;
 206     }
 207
 208     if (enable) {
 209         VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
 210
 211         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 212                                  k->is_console ? NULL : chr_event,
 213                                  chr_be_change, vcon, NULL, false);
 214     } else {
 215         qemu_chr_fe_set_handlers(&vcon->chr, NULL, NULL, NULL,
 216                                  NULL, NULL, NULL, false);
 217     }
 218 }
 219
 220 static void virtconsole_realize(DeviceState *dev, Error **errp)
 221 {
 222     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(dev);
 223     VirtConsole *vcon = VIRTIO_CONSOLE(dev);
 224     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(dev);
 225
 226     if (port->id == 0 && !k->is_console) {
 227         error_setg(errp, "Port number 0 on virtio-serial devices reserved "
 228                    "for virtconsole devices for backward compatibility.");
 229         return;
 230     }
 231
 232     if (qemu_chr_fe_backend_connected(&vcon->chr)) {
 233         /*
 234          * For consoles we don't block guest data transfer just
 235          * because nothing is connected - we'll just let it go
 236          * whetherever the chardev wants - /dev/null probably.
 237          *
 238          * For serial ports we need 100% reliable data transfer
 239          * so we use the opened/closed signals from chardev to
 240          * trigger open/close of the device
 241          */
 242         if (k->is_console) {
 243             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 244                                      NULL, chr_be_change,
 245                                      vcon, NULL, true);
 246             virtio_serial_open(port);
 247         } else {
 248             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 249                                      chr_event, chr_be_change,
 250                                      vcon, NULL, false);
 251         }
 252     }
 253 }
 254
 255 static void virtconsole_unrealize(DeviceState *dev)
 256 {
 257     VirtConsole *vcon = VIRTIO_CONSOLE(dev);
 258
 259     if (vcon->watch) {
 260         g_source_remove(vcon->watch);
 261     }
 262 }
 263
 264 static void virtconsole_class_init(ObjectClass *klass, void *data)
 265 {
 266     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);
 267
 268     k->is_console = true;
 269 }
 270
 271 static const TypeInfo virtconsole_info = {
 272     .name          = "virtconsole",
 273     .parent        = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
 274     .class_init    = virtconsole_class_init,
 275 };
 276
 277 static Property virtserialport_properties[] = {
 278     DEFINE_PROP_CHR("chardev", VirtConsole, chr),
 279     DEFINE_PROP_END_OF_LIST(),
 280 };
 281
 282 static void virtserialport_class_init(ObjectClass *klass, void *data)
 283 {
 284     DeviceClass *dc = DEVICE_CLASS(klass);
 285     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);
 286
 287     k->realize = virtconsole_realize;
 288     k->unrealize = virtconsole_unrealize;
 289     k->have_data = flush_buf;
 290     k->set_guest_connected = set_guest_connected;
 291     k->enable_backend = virtconsole_enable_backend;
 292     k->guest_writable = guest_writable;
 293     device_class_set_props(dc, virtserialport_properties);
 294 }
 295
 296 static const TypeInfo virtserialport_info = {
 297     .name          = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
 298     .parent        = TYPE_VIRTIO_SERIAL_PORT,
 299     .instance_size = sizeof(VirtConsole),
 300     .class_init    = virtserialport_class_init,
 301 };
 302
 303 static void virtconsole_register_types(void)
 304 {
 305     type_register_static(&virtserialport_info);
 306     type_register_static(&virtconsole_info);
 307 }
 308
 309 type_init(virtconsole_register_types)