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