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