hw/xen_backend.c

   1 /*
   2  *  xen backend driver infrastructure
   3  *  (c) 2008 Gerd Hoffmann <kraxel@redhat.com>
   4  *
   5  *  This program is free software; you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation; under version 2 of the License.
   8  *
   9  *  This program is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *  GNU General Public License for more details.
  13  *
  14  *  You should have received a copy of the GNU General Public License along
  15  *  with this program; if not, write to the Free Software Foundation, Inc.,
  16  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  */
  18
  19 /*
  20  * TODO: add some xenbus / xenstore concepts overview here.
  21  */
  22
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <stdarg.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #include <fcntl.h>
  29 #include <inttypes.h>
  30 #include <sys/types.h>
  31 #include <sys/stat.h>
  32 #include <sys/mman.h>
  33 #include <sys/signal.h>
  34
  35 #include <xs.h>
  36 #include <xenctrl.h>
  37 #include <xen/grant_table.h>
  38
  39 #include "hw.h"
  40 #include "qemu-char.h"
  41 #include "xen_backend.h"
  42
  43 /* ------------------------------------------------------------- */
  44
  45 /* public */
  46 int xen_xc;
  47 struct xs_handle *xenstore = NULL;
  48 const char *xen_protocol;
  49
  50 /* private */
  51 static TAILQ_HEAD(XenDeviceHead, XenDevice) xendevs = TAILQ_HEAD_INITIALIZER(xendevs);
  52 static int debug = 0;
  53
  54 /* ------------------------------------------------------------- */
  55
  56 int xenstore_write_str(const char *base, const char *node, const char *val)
  57 {
  58     char abspath[XEN_BUFSIZE];
  59
  60     snprintf(abspath, sizeof(abspath), "%s/%s", base, node);
  61     if (!xs_write(xenstore, 0, abspath, val, strlen(val)))
  62         return -1;
  63     return 0;
  64 }
  65
  66 char *xenstore_read_str(const char *base, const char *node)
  67 {
  68     char abspath[XEN_BUFSIZE];
  69     unsigned int len;
  70     char *str, *ret = NULL;
  71
  72     snprintf(abspath, sizeof(abspath), "%s/%s", base, node);
  73     str = xs_read(xenstore, 0, abspath, &len);
  74     if (str != NULL) {
  75         /* move to qemu-allocated memory to make sure
  76          * callers can savely qemu_free() stuff. */
  77         ret = qemu_strdup(str);
  78         free(str);
  79     }
  80     return ret;
  81 }
  82
  83 int xenstore_write_int(const char *base, const char *node, int ival)
  84 {
  85     char val[32];
  86
  87     snprintf(val, sizeof(val), "%d", ival);
  88     return xenstore_write_str(base, node, val);
  89 }
  90
  91 int xenstore_read_int(const char *base, const char *node, int *ival)
  92 {
  93     char *val;
  94     int rc = -1;
  95
  96     val = xenstore_read_str(base, node);
  97     if (val && 1 == sscanf(val, "%d", ival))
  98         rc = 0;
  99     qemu_free(val);
 100     return rc;
 101 }
 102
 103 int xenstore_write_be_str(struct XenDevice *xendev, const char *node, const char *val)
 104 {
 105     return xenstore_write_str(xendev->be, node, val);
 106 }
 107
 108 int xenstore_write_be_int(struct XenDevice *xendev, const char *node, int ival)
 109 {
 110     return xenstore_write_int(xendev->be, node, ival);
 111 }
 112
 113 char *xenstore_read_be_str(struct XenDevice *xendev, const char *node)
 114 {
 115     return xenstore_read_str(xendev->be, node);
 116 }
 117
 118 int xenstore_read_be_int(struct XenDevice *xendev, const char *node, int *ival)
 119 {
 120     return xenstore_read_int(xendev->be, node, ival);
 121 }
 122
 123 char *xenstore_read_fe_str(struct XenDevice *xendev, const char *node)
 124 {
 125     return xenstore_read_str(xendev->fe, node);
 126 }
 127
 128 int xenstore_read_fe_int(struct XenDevice *xendev, const char *node, int *ival)
 129 {
 130     return xenstore_read_int(xendev->fe, node, ival);
 131 }
 132
 133 /* ------------------------------------------------------------- */
 134
 135 const char *xenbus_strstate(enum xenbus_state state)
 136 {
 137         static const char *const name[] = {
 138                 [ XenbusStateUnknown      ] = "Unknown",
 139                 [ XenbusStateInitialising ] = "Initialising",
 140                 [ XenbusStateInitWait     ] = "InitWait",
 141                 [ XenbusStateInitialised  ] = "Initialised",
 142                 [ XenbusStateConnected    ] = "Connected",
 143                 [ XenbusStateClosing      ] = "Closing",
 144                 [ XenbusStateClosed       ] = "Closed",
 145         };
 146         return (state < ARRAY_SIZE(name)) ? name[state] : "INVALID";
 147 }
 148
 149 int xen_be_set_state(struct XenDevice *xendev, enum xenbus_state state)
 150 {
 151     int rc;
 152
 153     rc = xenstore_write_be_int(xendev, "state", state);
 154     if (rc < 0)
 155         return rc;
 156     xen_be_printf(xendev, 1, "backend state: %s -> %s\n",
 157                   xenbus_strstate(xendev->be_state), xenbus_strstate(state));
 158     xendev->be_state = state;
 159     return 0;
 160 }
 161
 162 /* ------------------------------------------------------------- */
 163
 164 struct XenDevice *xen_be_find_xendev(const char *type, int dom, int dev)
 165 {
 166     struct XenDevice *xendev;
 167
 168     TAILQ_FOREACH(xendev, &xendevs, next) {
 169         if (xendev->dom != dom)
 170             continue;
 171         if (xendev->dev != dev)
 172             continue;
 173         if (strcmp(xendev->type, type) != 0)
 174             continue;
 175         return xendev;
 176     }
 177     return NULL;
 178 }
 179
 180 /*
 181  * get xen backend device, allocate a new one if it doesn't exist.
 182  */
 183 static struct XenDevice *xen_be_get_xendev(const char *type, int dom, int dev,
 184                                            struct XenDevOps *ops)
 185 {
 186     struct XenDevice *xendev;
 187     char *dom0;
 188
 189     xendev = xen_be_find_xendev(type, dom, dev);
 190     if (xendev)
 191         return xendev;
 192
 193     /* init new xendev */
 194     xendev = qemu_mallocz(ops->size);
 195     xendev->type  = type;
 196     xendev->dom   = dom;
 197     xendev->dev   = dev;
 198     xendev->ops   = ops;
 199
 200     dom0 = xs_get_domain_path(xenstore, 0);
 201     snprintf(xendev->be, sizeof(xendev->be), "%s/backend/%s/%d/%d",
 202              dom0, xendev->type, xendev->dom, xendev->dev);
 203     snprintf(xendev->name, sizeof(xendev->name), "%s-%d",
 204              xendev->type, xendev->dev);
 205     free(dom0);
 206
 207     xendev->debug      = debug;
 208     xendev->local_port = -1;
 209
 210     xendev->evtchndev = xc_evtchn_open();
 211     if (xendev->evtchndev < 0) {
 212         xen_be_printf(NULL, 0, "can't open evtchn device\n");
 213         qemu_free(xendev);
 214         return NULL;
 215     }
 216     fcntl(xc_evtchn_fd(xendev->evtchndev), F_SETFD, FD_CLOEXEC);
 217
 218     if (ops->flags & DEVOPS_FLAG_NEED_GNTDEV) {
 219         xendev->gnttabdev = xc_gnttab_open();
 220         if (xendev->gnttabdev < 0) {
 221             xen_be_printf(NULL, 0, "can't open gnttab device\n");
 222             xc_evtchn_close(xendev->evtchndev);
 223             qemu_free(xendev);
 224             return NULL;
 225         }
 226     } else {
 227         xendev->gnttabdev = -1;
 228     }
 229
 230     TAILQ_INSERT_TAIL(&xendevs, xendev, next);
 231
 232     if (xendev->ops->alloc)
 233         xendev->ops->alloc(xendev);
 234
 235     return xendev;
 236 }
 237
 238 /*
 239  * release xen backend device.
 240  */
 241 static struct XenDevice *xen_be_del_xendev(int dom, int dev)
 242 {
 243     struct XenDevice *xendev, *xnext;
 244
 245     /*
 246      * This is pretty much like TAILQ_FOREACH(xendev, &xendevs, next) but
 247      * we save the next pointer in xnext because we might free xendev.
 248      */
 249     xnext = xendevs.tqh_first;
 250     while (xnext) {
 251         xendev = xnext;
 252         xnext = xendev->next.tqe_next;
 253
 254         if (xendev->dom != dom)
 255             continue;
 256         if (xendev->dev != dev && dev != -1)
 257             continue;
 258
 259         if (xendev->ops->free)
 260             xendev->ops->free(xendev);
 261
 262         if (xendev->fe) {
 263             char token[XEN_BUFSIZE];
 264             snprintf(token, sizeof(token), "fe:%p", xendev);
 265             xs_unwatch(xenstore, xendev->fe, token);
 266             qemu_free(xendev->fe);
 267         }
 268
 269         if (xendev->evtchndev >= 0)
 270             xc_evtchn_close(xendev->evtchndev);
 271         if (xendev->gnttabdev >= 0)
 272             xc_gnttab_close(xendev->gnttabdev);
 273
 274         TAILQ_REMOVE(&xendevs, xendev, next);
 275         qemu_free(xendev);
 276     }
 277     return NULL;
 278 }
 279
 280 /*
 281  * Sync internal data structures on xenstore updates.
 282  * Node specifies the changed field.  node = NULL means
 283  * update all fields (used for initialization).
 284  */
 285 static void xen_be_backend_changed(struct XenDevice *xendev, const char *node)
 286 {
 287     if (node == NULL  ||  strcmp(node, "online") == 0) {
 288         if (xenstore_read_be_int(xendev, "online", &xendev->online) == -1)
 289             xendev->online = 0;
 290     }
 291
 292     if (node) {
 293         xen_be_printf(xendev, 2, "backend update: %s\n", node);
 294         if (xendev->ops->backend_changed)
 295             xendev->ops->backend_changed(xendev, node);
 296     }
 297 }
 298
 299 static void xen_be_frontend_changed(struct XenDevice *xendev, const char *node)
 300 {
 301     int fe_state;
 302
 303     if (node == NULL  ||  strcmp(node, "state") == 0) {
 304         if (xenstore_read_fe_int(xendev, "state", &fe_state) == -1)
 305             fe_state = XenbusStateUnknown;
 306         if (xendev->fe_state != fe_state)
 307             xen_be_printf(xendev, 1, "frontend state: %s -> %s\n",
 308                           xenbus_strstate(xendev->fe_state),
 309                           xenbus_strstate(fe_state));
 310         xendev->fe_state = fe_state;
 311     }
 312     if (node == NULL  ||  strcmp(node, "protocol") == 0) {
 313         qemu_free(xendev->protocol);
 314         xendev->protocol = xenstore_read_fe_str(xendev, "protocol");
 315         if (xendev->protocol)
 316             xen_be_printf(xendev, 1, "frontend protocol: %s\n", xendev->protocol);
 317     }
 318
 319     if (node) {
 320         xen_be_printf(xendev, 2, "frontend update: %s\n", node);
 321         if (xendev->ops->frontend_changed)
 322             xendev->ops->frontend_changed(xendev, node);
 323     }
 324 }
 325
 326 /* ------------------------------------------------------------- */
 327 /* Check for possible state transitions and perform them.        */
 328
 329 /*
 330  * Initial xendev setup.  Read frontend path, register watch for it.
 331  * Should succeed once xend finished setting up the backend device.
 332  *
 333  * Also sets initial state (-> Initializing) when done.  Which
 334  * only affects the xendev->be_state variable as xenbus should
 335  * already be put into that state by xend.
 336  */
 337 static int xen_be_try_setup(struct XenDevice *xendev)
 338 {
 339     char token[XEN_BUFSIZE];
 340     int be_state;
 341
 342     if (xenstore_read_be_int(xendev, "state", &be_state) == -1) {
 343         xen_be_printf(xendev, 0, "reading backend state failed\n");
 344         return -1;
 345     }
 346
 347     if (be_state != XenbusStateInitialising) {
 348         xen_be_printf(xendev, 0, "initial backend state is wrong (%s)\n",
 349                       xenbus_strstate(be_state));
 350         return -1;
 351     }
 352
 353     xendev->fe = xenstore_read_be_str(xendev, "frontend");
 354     if (xendev->fe == NULL) {
 355         xen_be_printf(xendev, 0, "reading frontend path failed\n");
 356         return -1;
 357     }
 358
 359     /* setup frontend watch */
 360     snprintf(token, sizeof(token), "fe:%p", xendev);
 361     if (!xs_watch(xenstore, xendev->fe, token)) {
 362         xen_be_printf(xendev, 0, "watching frontend path (%s) failed\n",
 363                       xendev->fe);
 364         return -1;
 365     }
 366     xen_be_set_state(xendev, XenbusStateInitialising);
 367
 368     xen_be_backend_changed(xendev, NULL);
 369     xen_be_frontend_changed(xendev, NULL);
 370     return 0;
 371 }
 372
 373 /*
 374  * Try initialize xendev.  Prepare everything the backend can do
 375  * without synchronizing with the frontend.  Fakes hotplug-status.  No
 376  * hotplug involved here because this is about userspace drivers, thus
 377  * there are kernel backend devices which could invoke hotplug.
 378  *
 379  * Goes to InitWait on success.
 380  */
 381 static int xen_be_try_init(struct XenDevice *xendev)
 382 {
 383     int rc = 0;
 384
 385     if (!xendev->online) {
 386         xen_be_printf(xendev, 1, "not online\n");
 387         return -1;
 388     }
 389
 390     if (xendev->ops->init)
 391         rc = xendev->ops->init(xendev);
 392     if (rc != 0) {
 393         xen_be_printf(xendev, 1, "init() failed\n");
 394         return rc;
 395     }
 396
 397     xenstore_write_be_str(xendev, "hotplug-status", "connected");
 398     xen_be_set_state(xendev, XenbusStateInitWait);
 399     return 0;
 400 }
 401
 402 /*
 403  * Try to connect xendev.  Depends on the frontend being ready
 404  * for it (shared ring and evtchn info in xenstore, state being
 405  * Initialised or Connected).
 406  *
 407  * Goes to Connected on success.
 408  */
 409 static int xen_be_try_connect(struct XenDevice *xendev)
 410 {
 411     int rc = 0;
 412
 413     if (xendev->fe_state != XenbusStateInitialised  &&
 414         xendev->fe_state != XenbusStateConnected) {
 415         if (xendev->ops->flags & DEVOPS_FLAG_IGNORE_STATE) {
 416             xen_be_printf(xendev, 2, "frontend not ready, ignoring\n");
 417         } else {
 418             xen_be_printf(xendev, 2, "frontend not ready (yet)\n");
 419             return -1;
 420         }
 421     }
 422
 423     if (xendev->ops->connect)
 424         rc = xendev->ops->connect(xendev);
 425     if (rc != 0) {
 426         xen_be_printf(xendev, 0, "connect() failed\n");
 427         return rc;
 428     }
 429
 430     xen_be_set_state(xendev, XenbusStateConnected);
 431     return 0;
 432 }
 433
 434 /*
 435  * Teardown connection.
 436  *
 437  * Goes to Closed when done.
 438  */
 439 static void xen_be_disconnect(struct XenDevice *xendev, enum xenbus_state state)
 440 {
 441     if (xendev->be_state != XenbusStateClosing &&
 442         xendev->be_state != XenbusStateClosed  &&
 443         xendev->ops->disconnect)
 444         xendev->ops->disconnect(xendev);
 445     if (xendev->be_state != state)
 446         xen_be_set_state(xendev, state);
 447 }
 448
 449 /*
 450  * Try to reset xendev, for reconnection by another frontend instance.
 451  */
 452 static int xen_be_try_reset(struct XenDevice *xendev)
 453 {
 454     if (xendev->fe_state != XenbusStateInitialising)
 455         return -1;
 456
 457     xen_be_printf(xendev, 1, "device reset (for re-connect)\n");
 458     xen_be_set_state(xendev, XenbusStateInitialising);
 459     return 0;
 460 }
 461
 462 /*
 463  * state change dispatcher function
 464  */
 465 void xen_be_check_state(struct XenDevice *xendev)
 466 {
 467     int rc = 0;
 468
 469     /* frontend may request shutdown from almost anywhere */
 470     if (xendev->fe_state == XenbusStateClosing ||
 471         xendev->fe_state == XenbusStateClosed) {
 472         xen_be_disconnect(xendev, xendev->fe_state);
 473         return;
 474     }
 475
 476     /* check for possible backend state transitions */
 477     for (;;) {
 478         switch (xendev->be_state) {
 479         case XenbusStateUnknown:
 480             rc = xen_be_try_setup(xendev);
 481             break;
 482         case XenbusStateInitialising:
 483             rc = xen_be_try_init(xendev);
 484             break;
 485         case XenbusStateInitWait:
 486             rc = xen_be_try_connect(xendev);
 487             break;
 488         case XenbusStateClosed:
 489             rc = xen_be_try_reset(xendev);
 490             break;
 491         default:
 492             rc = -1;
 493         }
 494         if (rc != 0)
 495             break;
 496     }
 497 }
 498
 499 /* ------------------------------------------------------------- */
 500
 501 static int xenstore_scan(const char *type, int dom, struct XenDevOps *ops)
 502 {
 503     struct XenDevice *xendev;
 504     char path[XEN_BUFSIZE], token[XEN_BUFSIZE];
 505     char **dev = NULL, *dom0;
 506     unsigned int cdev, j;
 507
 508     /* setup watch */
 509     dom0 = xs_get_domain_path(xenstore, 0);
 510     snprintf(token, sizeof(token), "be:%p:%d:%p", type, dom, ops);
 511     snprintf(path, sizeof(path), "%s/backend/%s/%d", dom0, type, dom);
 512     free(dom0);
 513     if (!xs_watch(xenstore, path, token)) {
 514         xen_be_printf(NULL, 0, "xen be: watching backend path (%s) failed\n", path);
 515         return -1;
 516     }
 517
 518     /* look for backends */
 519     dev = xs_directory(xenstore, 0, path, &cdev);
 520     if (!dev)
 521         return 0;
 522     for (j = 0; j < cdev; j++) {
 523         xendev = xen_be_get_xendev(type, dom, atoi(dev[j]), ops);
 524         if (xendev == NULL)
 525             continue;
 526         xen_be_check_state(xendev);
 527     }
 528     free(dev);
 529     return 0;
 530 }
 531
 532 static void xenstore_update_be(char *watch, char *type, int dom,
 533                                struct XenDevOps *ops)
 534 {
 535     struct XenDevice *xendev;
 536     char path[XEN_BUFSIZE], *dom0;
 537     unsigned int len, dev;
 538
 539     dom0 = xs_get_domain_path(xenstore, 0);
 540     len = snprintf(path, sizeof(path), "%s/backend/%s/%d", dom0, type, dom);
 541     free(dom0);
 542     if (strncmp(path, watch, len) != 0)
 543         return;
 544     if (sscanf(watch+len, "/%u/%255s", &dev, path) != 2) {
 545         strcpy(path, "");
 546         if (sscanf(watch+len, "/%u", &dev) != 1)
 547             dev = -1;
 548     }
 549     if (dev == -1)
 550         return;
 551
 552     if (0) {
 553         /* FIXME: detect devices being deleted from xenstore ... */
 554         xen_be_del_xendev(dom, dev);
 555     }
 556
 557     xendev = xen_be_get_xendev(type, dom, dev, ops);
 558     if (xendev != NULL) {
 559         xen_be_backend_changed(xendev, path);
 560         xen_be_check_state(xendev);
 561     }
 562 }
 563
 564 static void xenstore_update_fe(char *watch, struct XenDevice *xendev)
 565 {
 566     char *node;
 567     unsigned int len;
 568
 569     len = strlen(xendev->fe);
 570     if (strncmp(xendev->fe, watch, len) != 0)
 571         return;
 572     if (watch[len] != '/')
 573         return;
 574     node = watch + len + 1;
 575
 576     xen_be_frontend_changed(xendev, node);
 577     xen_be_check_state(xendev);
 578 }
 579
 580 static void xenstore_update(void *unused)
 581 {
 582     char **vec = NULL;
 583     intptr_t type, ops, ptr;
 584     unsigned int dom, count;
 585
 586     vec = xs_read_watch(xenstore, &count);
 587     if (vec == NULL)
 588         goto cleanup;
 589
 590     if (sscanf(vec[XS_WATCH_TOKEN], "be:%" PRIxPTR ":%d:%" PRIxPTR,
 591                &type, &dom, &ops) == 3)
 592         xenstore_update_be(vec[XS_WATCH_PATH], (void*)type, dom, (void*)ops);
 593     if (sscanf(vec[XS_WATCH_TOKEN], "fe:%" PRIxPTR, &ptr) == 1)
 594         xenstore_update_fe(vec[XS_WATCH_PATH], (void*)ptr);
 595
 596 cleanup:
 597     qemu_free(vec);
 598 }
 599
 600 static void xen_be_evtchn_event(void *opaque)
 601 {
 602     struct XenDevice *xendev = opaque;
 603     evtchn_port_t port;
 604
 605     port = xc_evtchn_pending(xendev->evtchndev);
 606     if (port != xendev->local_port) {
 607         xen_be_printf(xendev, 0, "xc_evtchn_pending returned %d (expected %d)\n",
 608                       port, xendev->local_port);
 609         return;
 610     }
 611     xc_evtchn_unmask(xendev->evtchndev, port);
 612
 613     if (xendev->ops->event)
 614         xendev->ops->event(xendev);
 615 }
 616
 617 /* -------------------------------------------------------------------- */
 618
 619 int xen_be_init(void)
 620 {
 621     xenstore = xs_daemon_open();
 622     if (!xenstore) {
 623         xen_be_printf(NULL, 0, "can't connect to xenstored\n");
 624         return -1;
 625     }
 626
 627     if (qemu_set_fd_handler(xs_fileno(xenstore), xenstore_update, NULL, NULL) < 0)
 628         goto err;
 629
 630     xen_xc = xc_interface_open();
 631     if (xen_xc == -1) {
 632         xen_be_printf(NULL, 0, "can't open xen interface\n");
 633         goto err;
 634     }
 635     return 0;
 636
 637 err:
 638     qemu_set_fd_handler(xs_fileno(xenstore), NULL, NULL, NULL);
 639     xs_daemon_close(xenstore);
 640     xenstore = NULL;
 641
 642     return -1;
 643 }
 644
 645 int xen_be_register(const char *type, struct XenDevOps *ops)
 646 {
 647     return xenstore_scan(type, xen_domid, ops);
 648 }
 649
 650 int xen_be_bind_evtchn(struct XenDevice *xendev)
 651 {
 652     if (xendev->local_port != -1)
 653         return 0;
 654     xendev->local_port = xc_evtchn_bind_interdomain
 655         (xendev->evtchndev, xendev->dom, xendev->remote_port);
 656     if (xendev->local_port == -1) {
 657         xen_be_printf(xendev, 0, "xc_evtchn_bind_interdomain failed\n");
 658         return -1;
 659     }
 660     xen_be_printf(xendev, 2, "bind evtchn port %d\n", xendev->local_port);
 661     qemu_set_fd_handler(xc_evtchn_fd(xendev->evtchndev),
 662                         xen_be_evtchn_event, NULL, xendev);
 663     return 0;
 664 }
 665
 666 void xen_be_unbind_evtchn(struct XenDevice *xendev)
 667 {
 668     if (xendev->local_port == -1)
 669         return;
 670     qemu_set_fd_handler(xc_evtchn_fd(xendev->evtchndev), NULL, NULL, NULL);
 671     xc_evtchn_unbind(xendev->evtchndev, xendev->local_port);
 672     xen_be_printf(xendev, 2, "unbind evtchn port %d\n", xendev->local_port);
 673     xendev->local_port = -1;
 674 }
 675
 676 int xen_be_send_notify(struct XenDevice *xendev)
 677 {
 678     return xc_evtchn_notify(xendev->evtchndev, xendev->local_port);
 679 }
 680
 681 /*
 682  * msg_level:
 683  *  0 == errors (stderr + logfile).
 684  *  1 == informative debug messages (logfile only).
 685  *  2 == noisy debug messages (logfile only).
 686  *  3 == will flood your log (logfile only).
 687  */
 688 void xen_be_printf(struct XenDevice *xendev, int msg_level, const char *fmt, ...)
 689 {
 690     va_list args;
 691
 692     if (xendev) {
 693         if (msg_level > xendev->debug)
 694             return;
 695         qemu_log("xen be: %s: ", xendev->name);
 696         if (msg_level == 0)
 697             fprintf(stderr, "xen be: %s: ", xendev->name);
 698     } else {
 699         if (msg_level > debug)
 700             return;
 701         qemu_log("xen be core: ");
 702         if (msg_level == 0)
 703             fprintf(stderr, "xen be core: ");
 704     }
 705     va_start(args, fmt);
 706     qemu_log_vprintf(fmt, args);
 707     va_end(args);
 708     if (msg_level == 0) {
 709         va_start(args, fmt);
 710         vfprintf(stderr, fmt, args);
 711         va_end(args);
 712     }
 713     qemu_log_flush();
 714 }