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 static 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 }; 525 526 static void xen_9pfs_register_backend(void) 527 { 528 xen_be_register("9pfs", &xen_9pfs_ops); 529 } 530 xen_backend_init(xen_9pfs_register_backend); 531