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