hw/9pfs/xen-9p-backend.c

   1 /*
   2  * Xen 9p backend
   3  *
   4  * Copyright Aporeto 2017
   5  *
   6  * Authors:
   7  *  Stefano Stabellini <stefano@aporeto.com>
   8  *
   9  */
  10
  11 /*
  12  * Not so fast! You might want to read the 9p developer docs first:
  13  * https://wiki.qemu.org/Documentation/9p
  14  */
  15
  16 #include "qemu/osdep.h"
  17
  18 #include "hw/9pfs/9p.h"
  19 #include "hw/xen/xen-legacy-backend.h"
  20 #include "hw/9pfs/xen-9pfs.h"
  21 #include "qapi/error.h"
  22 #include "qemu/config-file.h"
  23 #include "qemu/main-loop.h"
  24 #include "qemu/option.h"
  25 #include "qemu/iov.h"
  26 #include "fsdev/qemu-fsdev.h"
  27
  28 #include "trace.h"
  29
  30 #define VERSIONS "1"
  31 #define MAX_RINGS 8
  32 #define MAX_RING_ORDER 9
  33
  34 typedef struct Xen9pfsRing {
  35     struct Xen9pfsDev *priv;
  36
  37     int ref;
  38     xenevtchn_handle   *evtchndev;
  39     int evtchn;
  40     int local_port;
  41     int ring_order;
  42     struct xen_9pfs_data_intf *intf;
  43     unsigned char *data;
  44     struct xen_9pfs_data ring;
  45
  46     struct iovec *sg;
  47     QEMUBH *bh;
  48     Coroutine *co;
  49
  50     /* local copies, so that we can read/write PDU data directly from
  51      * the ring */
  52     RING_IDX out_cons, out_size, in_cons;
  53     bool inprogress;
  54 } Xen9pfsRing;
  55
  56 typedef struct Xen9pfsDev {
  57     struct XenLegacyDevice xendev;  /* must be first */
  58     V9fsState state;
  59     char *path;
  60     char *security_model;
  61     char *tag;
  62     char *id;
  63
  64     int num_rings;
  65     Xen9pfsRing *rings;
  66     MemReentrancyGuard mem_reentrancy_guard;
  67 } Xen9pfsDev;
  68
  69 static void xen_9pfs_disconnect(struct XenLegacyDevice *xendev);
  70
  71 static void xen_9pfs_in_sg(Xen9pfsRing *ring,
  72                            struct iovec *in_sg,
  73                            int *num,
  74                            uint32_t idx,
  75                            uint32_t size)
  76 {
  77     RING_IDX cons, prod, masked_prod, masked_cons;
  78
  79     cons = ring->intf->in_cons;
  80     prod = ring->intf->in_prod;
  81     xen_rmb();
  82     masked_prod = xen_9pfs_mask(prod, XEN_FLEX_RING_SIZE(ring->ring_order));
  83     masked_cons = xen_9pfs_mask(cons, XEN_FLEX_RING_SIZE(ring->ring_order));
  84
  85     if (masked_prod < masked_cons) {
  86         in_sg[0].iov_base = ring->ring.in + masked_prod;
  87         in_sg[0].iov_len = masked_cons - masked_prod;
  88         *num = 1;
  89     } else {
  90         in_sg[0].iov_base = ring->ring.in + masked_prod;
  91         in_sg[0].iov_len = XEN_FLEX_RING_SIZE(ring->ring_order) - masked_prod;
  92         in_sg[1].iov_base = ring->ring.in;
  93         in_sg[1].iov_len = masked_cons;
  94         *num = 2;
  95     }
  96 }
  97
  98 static void xen_9pfs_out_sg(Xen9pfsRing *ring,
  99                             struct iovec *out_sg,
 100                             int *num,
 101                             uint32_t idx)
 102 {
 103     RING_IDX cons, prod, masked_prod, masked_cons;
 104
 105     cons = ring->intf->out_cons;
 106     prod = ring->intf->out_prod;
 107     xen_rmb();
 108     masked_prod = xen_9pfs_mask(prod, XEN_FLEX_RING_SIZE(ring->ring_order));
 109     masked_cons = xen_9pfs_mask(cons, XEN_FLEX_RING_SIZE(ring->ring_order));
 110
 111     if (masked_cons < masked_prod) {
 112         out_sg[0].iov_base = ring->ring.out + masked_cons;
 113         out_sg[0].iov_len = ring->out_size;
 114         *num = 1;
 115     } else {
 116         if (ring->out_size >
 117             (XEN_FLEX_RING_SIZE(ring->ring_order) - masked_cons)) {
 118             out_sg[0].iov_base = ring->ring.out + masked_cons;
 119             out_sg[0].iov_len = XEN_FLEX_RING_SIZE(ring->ring_order) -
 120                                 masked_cons;
 121             out_sg[1].iov_base = ring->ring.out;
 122             out_sg[1].iov_len = ring->out_size -
 123                                 (XEN_FLEX_RING_SIZE(ring->ring_order) -
 124                                  masked_cons);
 125             *num = 2;
 126         } else {
 127             out_sg[0].iov_base = ring->ring.out + masked_cons;
 128             out_sg[0].iov_len = ring->out_size;
 129             *num = 1;
 130         }
 131     }
 132 }
 133
 134 static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
 135                                      size_t offset,
 136                                      const char *fmt,
 137                                      va_list ap)
 138 {
 139     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
 140     struct iovec in_sg[2];
 141     int num;
 142     ssize_t ret;
 143
 144     xen_9pfs_in_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
 145                    in_sg, &num, pdu->idx, ROUND_UP(offset + 128, 512));
 146
 147     ret = v9fs_iov_vmarshal(in_sg, num, offset, 0, fmt, ap);
 148     if (ret < 0) {
 149         xen_pv_printf(&xen_9pfs->xendev, 0,
 150                       "Failed to encode VirtFS reply type %d\n",
 151                       pdu->id + 1);
 152         xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
 153         xen_9pfs_disconnect(&xen_9pfs->xendev);
 154     }
 155     return ret;
 156 }
 157
 158 static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
 159                                        size_t offset,
 160                                        const char *fmt,
 161                                        va_list ap)
 162 {
 163     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
 164     struct iovec out_sg[2];
 165     int num;
 166     ssize_t ret;
 167
 168     xen_9pfs_out_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
 169                     out_sg, &num, pdu->idx);
 170
 171     ret = v9fs_iov_vunmarshal(out_sg, num, offset, 0, fmt, ap);
 172     if (ret < 0) {
 173         xen_pv_printf(&xen_9pfs->xendev, 0,
 174                       "Failed to decode VirtFS request type %d\n", pdu->id);
 175         xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
 176         xen_9pfs_disconnect(&xen_9pfs->xendev);
 177     }
 178     return ret;
 179 }
 180
 181 static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
 182                                            struct iovec **piov,
 183                                            unsigned int *pniov,
 184                                            size_t size)
 185 {
 186     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
 187     Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
 188     int num;
 189
 190     g_free(ring->sg);
 191
 192     ring->sg = g_new0(struct iovec, 2);
 193     xen_9pfs_out_sg(ring, ring->sg, &num, pdu->idx);
 194     *piov = ring->sg;
 195     *pniov = num;
 196 }
 197
 198 static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
 199                                           struct iovec **piov,
 200                                           unsigned int *pniov,
 201                                           size_t size)
 202 {
 203     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
 204     Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
 205     int num;
 206     size_t buf_size;
 207
 208     g_free(ring->sg);
 209
 210     ring->sg = g_new0(struct iovec, 2);
 211     ring->co = qemu_coroutine_self();
 212     /* make sure other threads see ring->co changes before continuing */
 213     smp_wmb();
 214
 215 again:
 216     xen_9pfs_in_sg(ring, ring->sg, &num, pdu->idx, size);
 217     buf_size = iov_size(ring->sg, num);
 218     if (buf_size  < size) {
 219         qemu_coroutine_yield();
 220         goto again;
 221     }
 222     ring->co = NULL;
 223     /* make sure other threads see ring->co changes before continuing */
 224     smp_wmb();
 225
 226     *piov = ring->sg;
 227     *pniov = num;
 228 }
 229
 230 static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
 231 {
 232     RING_IDX prod;
 233     Xen9pfsDev *priv = container_of(pdu->s, Xen9pfsDev, state);
 234     Xen9pfsRing *ring = &priv->rings[pdu->tag % priv->num_rings];
 235
 236     g_free(ring->sg);
 237     ring->sg = NULL;
 238
 239     ring->intf->out_cons = ring->out_cons;
 240     xen_wmb();
 241
 242     prod = ring->intf->in_prod;
 243     xen_rmb();
 244     ring->intf->in_prod = prod + pdu->size;
 245     xen_wmb();
 246
 247     ring->inprogress = false;
 248     qemu_xen_evtchn_notify(ring->evtchndev, ring->local_port);
 249
 250     qemu_bh_schedule(ring->bh);
 251 }
 252
 253 static const V9fsTransport xen_9p_transport = {
 254     .pdu_vmarshal = xen_9pfs_pdu_vmarshal,
 255     .pdu_vunmarshal = xen_9pfs_pdu_vunmarshal,
 256     .init_in_iov_from_pdu = xen_9pfs_init_in_iov_from_pdu,
 257     .init_out_iov_from_pdu = xen_9pfs_init_out_iov_from_pdu,
 258     .push_and_notify = xen_9pfs_push_and_notify,
 259 };
 260
 261 static int xen_9pfs_init(struct XenLegacyDevice *xendev)
 262 {
 263     return 0;
 264 }
 265
 266 static int xen_9pfs_receive(Xen9pfsRing *ring)
 267 {
 268     P9MsgHeader h;
 269     RING_IDX cons, prod, masked_prod, masked_cons, queued;
 270     V9fsPDU *pdu;
 271
 272     if (ring->inprogress) {
 273         return 0;
 274     }
 275
 276     cons = ring->intf->out_cons;
 277     prod = ring->intf->out_prod;
 278     xen_rmb();
 279
 280     queued = xen_9pfs_queued(prod, cons, XEN_FLEX_RING_SIZE(ring->ring_order));
 281     if (queued < sizeof(h)) {
 282         return 0;
 283     }
 284     ring->inprogress = true;
 285
 286     masked_prod = xen_9pfs_mask(prod, XEN_FLEX_RING_SIZE(ring->ring_order));
 287     masked_cons = xen_9pfs_mask(cons, XEN_FLEX_RING_SIZE(ring->ring_order));
 288
 289     xen_9pfs_read_packet((uint8_t *) &h, ring->ring.out, sizeof(h),
 290                          masked_prod, &masked_cons,
 291                          XEN_FLEX_RING_SIZE(ring->ring_order));
 292     if (queued < le32_to_cpu(h.size_le)) {
 293         return 0;
 294     }
 295
 296     /* cannot fail, because we only handle one request per ring at a time */
 297     pdu = pdu_alloc(&ring->priv->state);
 298     ring->out_size = le32_to_cpu(h.size_le);
 299     ring->out_cons = cons + le32_to_cpu(h.size_le);
 300
 301     pdu_submit(pdu, &h);
 302
 303     return 0;
 304 }
 305
 306 static void xen_9pfs_bh(void *opaque)
 307 {
 308     Xen9pfsRing *ring = opaque;
 309     bool wait;
 310
 311 again:
 312     wait = ring->co != NULL && qemu_coroutine_entered(ring->co);
 313     /* paired with the smb_wmb barriers in xen_9pfs_init_in_iov_from_pdu */
 314     smp_rmb();
 315     if (wait) {
 316         cpu_relax();
 317         goto again;
 318     }
 319
 320     if (ring->co != NULL) {
 321         qemu_coroutine_enter_if_inactive(ring->co);
 322     }
 323     xen_9pfs_receive(ring);
 324 }
 325
 326 static void xen_9pfs_evtchn_event(void *opaque)
 327 {
 328     Xen9pfsRing *ring = opaque;
 329     evtchn_port_t port;
 330
 331     port = qemu_xen_evtchn_pending(ring->evtchndev);
 332     qemu_xen_evtchn_unmask(ring->evtchndev, port);
 333
 334     qemu_bh_schedule(ring->bh);
 335 }
 336
 337 static void xen_9pfs_disconnect(struct XenLegacyDevice *xendev)
 338 {
 339     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
 340     int i;
 341
 342     trace_xen_9pfs_disconnect(xendev->name);
 343
 344     for (i = 0; i < xen_9pdev->num_rings; i++) {
 345         if (xen_9pdev->rings[i].evtchndev != NULL) {
 346             qemu_set_fd_handler(qemu_xen_evtchn_fd(xen_9pdev->rings[i].evtchndev),
 347                                 NULL, NULL, NULL);
 348             qemu_xen_evtchn_unbind(xen_9pdev->rings[i].evtchndev,
 349                                    xen_9pdev->rings[i].local_port);
 350             xen_9pdev->rings[i].evtchndev = NULL;
 351         }
 352         if (xen_9pdev->rings[i].data != NULL) {
 353             xen_be_unmap_grant_refs(&xen_9pdev->xendev,
 354                                     xen_9pdev->rings[i].data,
 355                                     xen_9pdev->rings[i].intf->ref,
 356                                     (1 << xen_9pdev->rings[i].ring_order));
 357             xen_9pdev->rings[i].data = NULL;
 358         }
 359         if (xen_9pdev->rings[i].intf != NULL) {
 360             xen_be_unmap_grant_ref(&xen_9pdev->xendev,
 361                                    xen_9pdev->rings[i].intf,
 362                                    xen_9pdev->rings[i].ref);
 363             xen_9pdev->rings[i].intf = NULL;
 364         }
 365         if (xen_9pdev->rings[i].bh != NULL) {
 366             qemu_bh_delete(xen_9pdev->rings[i].bh);
 367             xen_9pdev->rings[i].bh = NULL;
 368         }
 369     }
 370
 371     g_free(xen_9pdev->id);
 372     xen_9pdev->id = NULL;
 373     g_free(xen_9pdev->tag);
 374     xen_9pdev->tag = NULL;
 375     g_free(xen_9pdev->path);
 376     xen_9pdev->path = NULL;
 377     g_free(xen_9pdev->security_model);
 378     xen_9pdev->security_model = NULL;
 379     g_free(xen_9pdev->rings);
 380     xen_9pdev->rings = NULL;
 381 }
 382
 383 static int xen_9pfs_free(struct XenLegacyDevice *xendev)
 384 {
 385     trace_xen_9pfs_free(xendev->name);
 386
 387     return 0;
 388 }
 389
 390 static int xen_9pfs_connect(struct XenLegacyDevice *xendev)
 391 {
 392     Error *err = NULL;
 393     int i;
 394     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
 395     V9fsState *s = &xen_9pdev->state;
 396     QemuOpts *fsdev;
 397
 398     trace_xen_9pfs_connect(xendev->name);
 399
 400     if (xenstore_read_fe_int(&xen_9pdev->xendev, "num-rings",
 401                              &xen_9pdev->num_rings) == -1 ||
 402         xen_9pdev->num_rings > MAX_RINGS || xen_9pdev->num_rings < 1) {
 403         return -1;
 404     }
 405
 406     xen_9pdev->rings = g_new0(Xen9pfsRing, xen_9pdev->num_rings);
 407     for (i = 0; i < xen_9pdev->num_rings; i++) {
 408         char *str;
 409         int ring_order;
 410
 411         xen_9pdev->rings[i].priv = xen_9pdev;
 412         xen_9pdev->rings[i].evtchn = -1;
 413         xen_9pdev->rings[i].local_port = -1;
 414
 415         str = g_strdup_printf("ring-ref%u", i);
 416         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
 417                                  &xen_9pdev->rings[i].ref) == -1) {
 418             g_free(str);
 419             goto out;
 420         }
 421         g_free(str);
 422         str = g_strdup_printf("event-channel-%u", i);
 423         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
 424                                  &xen_9pdev->rings[i].evtchn) == -1) {
 425             g_free(str);
 426             goto out;
 427         }
 428         g_free(str);
 429
 430         xen_9pdev->rings[i].intf =
 431             xen_be_map_grant_ref(&xen_9pdev->xendev,
 432                                  xen_9pdev->rings[i].ref,
 433                                  PROT_READ | PROT_WRITE);
 434         if (!xen_9pdev->rings[i].intf) {
 435             goto out;
 436         }
 437         ring_order = xen_9pdev->rings[i].intf->ring_order;
 438         if (ring_order > MAX_RING_ORDER) {
 439             goto out;
 440         }
 441         xen_9pdev->rings[i].ring_order = ring_order;
 442         xen_9pdev->rings[i].data =
 443             xen_be_map_grant_refs(&xen_9pdev->xendev,
 444                                   xen_9pdev->rings[i].intf->ref,
 445                                   (1 << ring_order),
 446                                   PROT_READ | PROT_WRITE);
 447         if (!xen_9pdev->rings[i].data) {
 448             goto out;
 449         }
 450         xen_9pdev->rings[i].ring.in = xen_9pdev->rings[i].data;
 451         xen_9pdev->rings[i].ring.out = xen_9pdev->rings[i].data +
 452                                        XEN_FLEX_RING_SIZE(ring_order);
 453
 454         xen_9pdev->rings[i].bh = qemu_bh_new_guarded(xen_9pfs_bh,
 455                                                      &xen_9pdev->rings[i],
 456                                                      &xen_9pdev->mem_reentrancy_guard);
 457         xen_9pdev->rings[i].out_cons = 0;
 458         xen_9pdev->rings[i].out_size = 0;
 459         xen_9pdev->rings[i].inprogress = false;
 460
 461
 462         xen_9pdev->rings[i].evtchndev = qemu_xen_evtchn_open();
 463         if (xen_9pdev->rings[i].evtchndev == NULL) {
 464             goto out;
 465         }
 466         qemu_set_cloexec(qemu_xen_evtchn_fd(xen_9pdev->rings[i].evtchndev));
 467         xen_9pdev->rings[i].local_port = qemu_xen_evtchn_bind_interdomain
 468                                             (xen_9pdev->rings[i].evtchndev,
 469                                              xendev->dom,
 470                                              xen_9pdev->rings[i].evtchn);
 471         if (xen_9pdev->rings[i].local_port == -1) {
 472             xen_pv_printf(xendev, 0,
 473                           "xenevtchn_bind_interdomain failed port=%d\n",
 474                           xen_9pdev->rings[i].evtchn);
 475             goto out;
 476         }
 477         xen_pv_printf(xendev, 2, "bind evtchn port %d\n", xendev->local_port);
 478         qemu_set_fd_handler(qemu_xen_evtchn_fd(xen_9pdev->rings[i].evtchndev),
 479                             xen_9pfs_evtchn_event, NULL, &xen_9pdev->rings[i]);
 480     }
 481
 482     xen_9pdev->security_model = xenstore_read_be_str(xendev, "security_model");
 483     xen_9pdev->path = xenstore_read_be_str(xendev, "path");
 484     xen_9pdev->id = s->fsconf.fsdev_id =
 485         g_strdup_printf("xen9p%d", xendev->dev);
 486     xen_9pdev->tag = s->fsconf.tag = xenstore_read_fe_str(xendev, "tag");
 487     fsdev = qemu_opts_create(qemu_find_opts("fsdev"),
 488             s->fsconf.tag,
 489             1, NULL);
 490     qemu_opt_set(fsdev, "fsdriver", "local", NULL);
 491     qemu_opt_set(fsdev, "path", xen_9pdev->path, NULL);
 492     qemu_opt_set(fsdev, "security_model", xen_9pdev->security_model, NULL);
 493     qemu_opts_set_id(fsdev, s->fsconf.fsdev_id);
 494     qemu_fsdev_add(fsdev, &err);
 495     if (err) {
 496         error_report_err(err);
 497     }
 498     v9fs_device_realize_common(s, &xen_9p_transport, NULL);
 499
 500     return 0;
 501
 502 out:
 503     xen_9pfs_free(xendev);
 504     return -1;
 505 }
 506
 507 static void xen_9pfs_alloc(struct XenLegacyDevice *xendev)
 508 {
 509     trace_xen_9pfs_alloc(xendev->name);
 510
 511     xenstore_write_be_str(xendev, "versions", VERSIONS);
 512     xenstore_write_be_int(xendev, "max-rings", MAX_RINGS);
 513     xenstore_write_be_int(xendev, "max-ring-page-order", MAX_RING_ORDER);
 514 }
 515
 516 struct XenDevOps xen_9pfs_ops = {
 517     .size       = sizeof(Xen9pfsDev),
 518     .flags      = DEVOPS_FLAG_NEED_GNTDEV,
 519     .alloc      = xen_9pfs_alloc,
 520     .init       = xen_9pfs_init,
 521     .initialise = xen_9pfs_connect,
 522     .disconnect = xen_9pfs_disconnect,
 523     .free       = xen_9pfs_free,
 524 };