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