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