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