drivers/scsi/xen-scsifront.c

   1 /*
   2  * Xen SCSI frontend driver
   3  *
   4  * Copyright (c) 2008, FUJITSU Limited
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License version 2
   8  * as published by the Free Software Foundation; or, when distributed
   9  * separately from the Linux kernel or incorporated into other
  10  * software packages, subject to the following license:
  11  *
  12  * Permission is hereby granted, free of charge, to any person obtaining a copy
  13  * of this source file (the "Software"), to deal in the Software without
  14  * restriction, including without limitation the rights to use, copy, modify,
  15  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  16  * and to permit persons to whom the Software is furnished to do so, subject to
  17  * the following conditions:
  18  *
  19  * The above copyright notice and this permission notice shall be included in
  20  * all copies or substantial portions of the Software.
  21  *
  22  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  23  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  24  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  25  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  26  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  27  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  28  * IN THE SOFTWARE.
  29  */
  30
  31 #include <linux/module.h>
  32 #include <linux/kernel.h>
  33 #include <linux/device.h>
  34 #include <linux/wait.h>
  35 #include <linux/interrupt.h>
  36 #include <linux/mutex.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/sched.h>
  39 #include <linux/blkdev.h>
  40 #include <linux/pfn.h>
  41 #include <linux/slab.h>
  42 #include <linux/bitops.h>
  43
  44 #include <scsi/scsi_cmnd.h>
  45 #include <scsi/scsi_device.h>
  46 #include <scsi/scsi.h>
  47 #include <scsi/scsi_host.h>
  48
  49 #include <xen/xen.h>
  50 #include <xen/xenbus.h>
  51 #include <xen/grant_table.h>
  52 #include <xen/events.h>
  53 #include <xen/page.h>
  54
  55 #include <xen/interface/grant_table.h>
  56 #include <xen/interface/io/vscsiif.h>
  57 #include <xen/interface/io/protocols.h>
  58
  59 #include <asm/xen/hypervisor.h>
  60
  61 #define VSCSIFRONT_OP_ADD_LUN   1
  62 #define VSCSIFRONT_OP_DEL_LUN   2
  63 #define VSCSIFRONT_OP_READD_LUN 3
  64
  65 /* Tuning point. */
  66 #define VSCSIIF_DEFAULT_CMD_PER_LUN 10
  67 #define VSCSIIF_MAX_TARGET          64
  68 #define VSCSIIF_MAX_LUN             255
  69
  70 #define VSCSIIF_RING_SIZE       __CONST_RING_SIZE(vscsiif, PAGE_SIZE)
  71 #define VSCSIIF_MAX_REQS        VSCSIIF_RING_SIZE
  72
  73 #define vscsiif_grants_sg(_sg)  (PFN_UP((_sg) *         \
  74                                 sizeof(struct scsiif_request_segment)))
  75
  76 struct vscsifrnt_shadow {
  77         /* command between backend and frontend */
  78         unsigned char act;
  79         uint8_t nr_segments;
  80         uint16_t rqid;
  81         uint16_t ref_rqid;
  82
  83         bool inflight;
  84
  85         unsigned int nr_grants;         /* number of grants in gref[] */
  86         struct scsiif_request_segment *sg;      /* scatter/gather elements */
  87         struct scsiif_request_segment seg[VSCSIIF_SG_TABLESIZE];
  88
  89         /* Do reset or abort function. */
  90         wait_queue_head_t wq_reset;     /* reset work queue           */
  91         int wait_reset;                 /* reset work queue condition */
  92         int32_t rslt_reset;             /* reset response status:     */
  93                                         /* SUCCESS or FAILED or:      */
  94 #define RSLT_RESET_WAITING      0
  95 #define RSLT_RESET_ERR          -1
  96
  97         /* Requested struct scsi_cmnd is stored from kernel. */
  98         struct scsi_cmnd *sc;
  99         int gref[vscsiif_grants_sg(SG_ALL) + SG_ALL];
 100 };
 101
 102 struct vscsifrnt_info {
 103         struct xenbus_device *dev;
 104
 105         struct Scsi_Host *host;
 106         enum {
 107                 STATE_INACTIVE,
 108                 STATE_ACTIVE,
 109                 STATE_ERROR
 110         }  host_active;
 111
 112         unsigned int evtchn;
 113         unsigned int irq;
 114
 115         grant_ref_t ring_ref;
 116         struct vscsiif_front_ring ring;
 117         struct vscsiif_response ring_rsp;
 118
 119         spinlock_t shadow_lock;
 120         DECLARE_BITMAP(shadow_free_bitmap, VSCSIIF_MAX_REQS);
 121         struct vscsifrnt_shadow *shadow[VSCSIIF_MAX_REQS];
 122
 123         /* Following items are protected by the host lock. */
 124         wait_queue_head_t wq_sync;
 125         wait_queue_head_t wq_pause;
 126         unsigned int wait_ring_available:1;
 127         unsigned int waiting_pause:1;
 128         unsigned int pause:1;
 129         unsigned callers;
 130
 131         char dev_state_path[64];
 132         struct task_struct *curr;
 133 };
 134
 135 static DEFINE_MUTEX(scsifront_mutex);
 136
 137 static void scsifront_wake_up(struct vscsifrnt_info *info)
 138 {
 139         info->wait_ring_available = 0;
 140         wake_up(&info->wq_sync);
 141 }
 142
 143 static int scsifront_get_rqid(struct vscsifrnt_info *info)
 144 {
 145         unsigned long flags;
 146         int free;
 147
 148         spin_lock_irqsave(&info->shadow_lock, flags);
 149
 150         free = find_first_bit(info->shadow_free_bitmap, VSCSIIF_MAX_REQS);
 151         __clear_bit(free, info->shadow_free_bitmap);
 152
 153         spin_unlock_irqrestore(&info->shadow_lock, flags);
 154
 155         return free;
 156 }
 157
 158 static int _scsifront_put_rqid(struct vscsifrnt_info *info, uint32_t id)
 159 {
 160         int empty = bitmap_empty(info->shadow_free_bitmap, VSCSIIF_MAX_REQS);
 161
 162         __set_bit(id, info->shadow_free_bitmap);
 163         info->shadow[id] = NULL;
 164
 165         return empty || info->wait_ring_available;
 166 }
 167
 168 static void scsifront_put_rqid(struct vscsifrnt_info *info, uint32_t id)
 169 {
 170         unsigned long flags;
 171         int kick;
 172
 173         spin_lock_irqsave(&info->shadow_lock, flags);
 174         kick = _scsifront_put_rqid(info, id);
 175         spin_unlock_irqrestore(&info->shadow_lock, flags);
 176
 177         if (kick)
 178                 scsifront_wake_up(info);
 179 }
 180
 181 static int scsifront_do_request(struct vscsifrnt_info *info,
 182                                 struct vscsifrnt_shadow *shadow)
 183 {
 184         struct vscsiif_front_ring *ring = &(info->ring);
 185         struct vscsiif_request *ring_req;
 186         struct scsi_cmnd *sc = shadow->sc;
 187         uint32_t id;
 188         int i, notify;
 189
 190         if (RING_FULL(&info->ring))
 191                 return -EBUSY;
 192
 193         id = scsifront_get_rqid(info);  /* use id in response */
 194         if (id >= VSCSIIF_MAX_REQS)
 195                 return -EBUSY;
 196
 197         info->shadow[id] = shadow;
 198         shadow->rqid = id;
 199
 200         ring_req = RING_GET_REQUEST(&(info->ring), ring->req_prod_pvt);
 201         ring->req_prod_pvt++;
 202
 203         ring_req->rqid        = id;
 204         ring_req->act         = shadow->act;
 205         ring_req->ref_rqid    = shadow->ref_rqid;
 206         ring_req->nr_segments = shadow->nr_segments;
 207
 208         ring_req->id      = sc->device->id;
 209         ring_req->lun     = sc->device->lun;
 210         ring_req->channel = sc->device->channel;
 211         ring_req->cmd_len = sc->cmd_len;
 212
 213         BUG_ON(sc->cmd_len > VSCSIIF_MAX_COMMAND_SIZE);
 214
 215         memcpy(ring_req->cmnd, sc->cmnd, sc->cmd_len);
 216
 217         ring_req->sc_data_direction   = (uint8_t)sc->sc_data_direction;
 218         ring_req->timeout_per_command = scsi_cmd_to_rq(sc)->timeout / HZ;
 219
 220         for (i = 0; i < (shadow->nr_segments & ~VSCSIIF_SG_GRANT); i++)
 221                 ring_req->seg[i] = shadow->seg[i];
 222
 223         shadow->inflight = true;
 224
 225         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(ring, notify);
 226         if (notify)
 227                 notify_remote_via_irq(info->irq);
 228
 229         return 0;
 230 }
 231
 232 static void scsifront_set_error(struct vscsifrnt_info *info, const char *msg)
 233 {
 234         shost_printk(KERN_ERR, info->host, KBUILD_MODNAME "%s\n"
 235                      "Disabling device for further use\n", msg);
 236         info->host_active = STATE_ERROR;
 237 }
 238
 239 static void scsifront_gnttab_done(struct vscsifrnt_info *info,
 240                                   struct vscsifrnt_shadow *shadow)
 241 {
 242         int i;
 243
 244         if (shadow->sc->sc_data_direction == DMA_NONE)
 245                 return;
 246
 247         for (i = 0; i < shadow->nr_grants; i++) {
 248                 if (unlikely(!gnttab_try_end_foreign_access(shadow->gref[i]))) {
 249                         scsifront_set_error(info, "grant still in use by backend");
 250                         return;
 251                 }
 252         }
 253
 254         kfree(shadow->sg);
 255 }
 256
 257 static unsigned int scsifront_host_byte(int32_t rslt)
 258 {
 259         switch (XEN_VSCSIIF_RSLT_HOST(rslt)) {
 260         case XEN_VSCSIIF_RSLT_HOST_OK:
 261                 return DID_OK;
 262         case XEN_VSCSIIF_RSLT_HOST_NO_CONNECT:
 263                 return DID_NO_CONNECT;
 264         case XEN_VSCSIIF_RSLT_HOST_BUS_BUSY:
 265                 return DID_BUS_BUSY;
 266         case XEN_VSCSIIF_RSLT_HOST_TIME_OUT:
 267                 return DID_TIME_OUT;
 268         case XEN_VSCSIIF_RSLT_HOST_BAD_TARGET:
 269                 return DID_BAD_TARGET;
 270         case XEN_VSCSIIF_RSLT_HOST_ABORT:
 271                 return DID_ABORT;
 272         case XEN_VSCSIIF_RSLT_HOST_PARITY:
 273                 return DID_PARITY;
 274         case XEN_VSCSIIF_RSLT_HOST_ERROR:
 275                 return DID_ERROR;
 276         case XEN_VSCSIIF_RSLT_HOST_RESET:
 277                 return DID_RESET;
 278         case XEN_VSCSIIF_RSLT_HOST_BAD_INTR:
 279                 return DID_BAD_INTR;
 280         case XEN_VSCSIIF_RSLT_HOST_PASSTHROUGH:
 281                 return DID_PASSTHROUGH;
 282         case XEN_VSCSIIF_RSLT_HOST_SOFT_ERROR:
 283                 return DID_SOFT_ERROR;
 284         case XEN_VSCSIIF_RSLT_HOST_IMM_RETRY:
 285                 return DID_IMM_RETRY;
 286         case XEN_VSCSIIF_RSLT_HOST_REQUEUE:
 287                 return DID_REQUEUE;
 288         case XEN_VSCSIIF_RSLT_HOST_TRANSPORT_DISRUPTED:
 289                 return DID_TRANSPORT_DISRUPTED;
 290         case XEN_VSCSIIF_RSLT_HOST_TRANSPORT_FAILFAST:
 291                 return DID_TRANSPORT_FAILFAST;
 292         case XEN_VSCSIIF_RSLT_HOST_TARGET_FAILURE:
 293                 return DID_TARGET_FAILURE;
 294         case XEN_VSCSIIF_RSLT_HOST_NEXUS_FAILURE:
 295                 return DID_NEXUS_FAILURE;
 296         case XEN_VSCSIIF_RSLT_HOST_ALLOC_FAILURE:
 297                 return DID_ALLOC_FAILURE;
 298         case XEN_VSCSIIF_RSLT_HOST_MEDIUM_ERROR:
 299                 return DID_MEDIUM_ERROR;
 300         case XEN_VSCSIIF_RSLT_HOST_TRANSPORT_MARGINAL:
 301                 return DID_TRANSPORT_MARGINAL;
 302         default:
 303                 return DID_ERROR;
 304         }
 305 }
 306
 307 static void scsifront_cdb_cmd_done(struct vscsifrnt_info *info,
 308                                    struct vscsiif_response *ring_rsp)
 309 {
 310         struct vscsifrnt_shadow *shadow;
 311         struct scsi_cmnd *sc;
 312         uint32_t id;
 313         uint8_t sense_len;
 314
 315         id = ring_rsp->rqid;
 316         shadow = info->shadow[id];
 317         sc = shadow->sc;
 318
 319         BUG_ON(sc == NULL);
 320
 321         scsifront_gnttab_done(info, shadow);
 322         if (info->host_active == STATE_ERROR)
 323                 return;
 324         scsifront_put_rqid(info, id);
 325
 326         set_host_byte(sc, scsifront_host_byte(ring_rsp->rslt));
 327         set_status_byte(sc, XEN_VSCSIIF_RSLT_STATUS(ring_rsp->rslt));
 328         scsi_set_resid(sc, ring_rsp->residual_len);
 329
 330         sense_len = min_t(uint8_t, VSCSIIF_SENSE_BUFFERSIZE,
 331                           ring_rsp->sense_len);
 332
 333         if (sense_len)
 334                 memcpy(sc->sense_buffer, ring_rsp->sense_buffer, sense_len);
 335
 336         scsi_done(sc);
 337 }
 338
 339 static void scsifront_sync_cmd_done(struct vscsifrnt_info *info,
 340                                     struct vscsiif_response *ring_rsp)
 341 {
 342         uint16_t id = ring_rsp->rqid;
 343         unsigned long flags;
 344         struct vscsifrnt_shadow *shadow = info->shadow[id];
 345         int kick;
 346
 347         spin_lock_irqsave(&info->shadow_lock, flags);
 348         shadow->wait_reset = 1;
 349         switch (shadow->rslt_reset) {
 350         case RSLT_RESET_WAITING:
 351                 if (ring_rsp->rslt == XEN_VSCSIIF_RSLT_RESET_SUCCESS)
 352                         shadow->rslt_reset = SUCCESS;
 353                 else
 354                         shadow->rslt_reset = FAILED;
 355                 break;
 356         case RSLT_RESET_ERR:
 357                 kick = _scsifront_put_rqid(info, id);
 358                 spin_unlock_irqrestore(&info->shadow_lock, flags);
 359                 kfree(shadow);
 360                 if (kick)
 361                         scsifront_wake_up(info);
 362                 return;
 363         default:
 364                 scsifront_set_error(info, "bad reset state");
 365                 break;
 366         }
 367         spin_unlock_irqrestore(&info->shadow_lock, flags);
 368
 369         wake_up(&shadow->wq_reset);
 370 }
 371
 372 static void scsifront_do_response(struct vscsifrnt_info *info,
 373                                   struct vscsiif_response *ring_rsp)
 374 {
 375         struct vscsifrnt_shadow *shadow;
 376
 377         if (ring_rsp->rqid >= VSCSIIF_MAX_REQS ||
 378             !info->shadow[ring_rsp->rqid]->inflight) {
 379                 scsifront_set_error(info, "illegal rqid returned by backend!");
 380                 return;
 381         }
 382         shadow = info->shadow[ring_rsp->rqid];
 383         shadow->inflight = false;
 384
 385         if (shadow->act == VSCSIIF_ACT_SCSI_CDB)
 386                 scsifront_cdb_cmd_done(info, ring_rsp);
 387         else
 388                 scsifront_sync_cmd_done(info, ring_rsp);
 389 }
 390
 391 static int scsifront_ring_drain(struct vscsifrnt_info *info,
 392                                 unsigned int *eoiflag)
 393 {
 394         struct vscsiif_response ring_rsp;
 395         RING_IDX i, rp;
 396         int more_to_do = 0;
 397
 398         rp = READ_ONCE(info->ring.sring->rsp_prod);
 399         virt_rmb();     /* ordering required respective to backend */
 400         if (RING_RESPONSE_PROD_OVERFLOW(&info->ring, rp)) {
 401                 scsifront_set_error(info, "illegal number of responses");
 402                 return 0;
 403         }
 404         for (i = info->ring.rsp_cons; i != rp; i++) {
 405                 RING_COPY_RESPONSE(&info->ring, i, &ring_rsp);
 406                 scsifront_do_response(info, &ring_rsp);
 407                 if (info->host_active == STATE_ERROR)
 408                         return 0;
 409                 *eoiflag &= ~XEN_EOI_FLAG_SPURIOUS;
 410         }
 411
 412         info->ring.rsp_cons = i;
 413
 414         if (i != info->ring.req_prod_pvt)
 415                 RING_FINAL_CHECK_FOR_RESPONSES(&info->ring, more_to_do);
 416         else
 417                 info->ring.sring->rsp_event = i + 1;
 418
 419         return more_to_do;
 420 }
 421
 422 static int scsifront_cmd_done(struct vscsifrnt_info *info,
 423                               unsigned int *eoiflag)
 424 {
 425         int more_to_do;
 426         unsigned long flags;
 427
 428         spin_lock_irqsave(info->host->host_lock, flags);
 429
 430         more_to_do = scsifront_ring_drain(info, eoiflag);
 431
 432         info->wait_ring_available = 0;
 433
 434         spin_unlock_irqrestore(info->host->host_lock, flags);
 435
 436         wake_up(&info->wq_sync);
 437
 438         return more_to_do;
 439 }
 440
 441 static irqreturn_t scsifront_irq_fn(int irq, void *dev_id)
 442 {
 443         struct vscsifrnt_info *info = dev_id;
 444         unsigned int eoiflag = XEN_EOI_FLAG_SPURIOUS;
 445
 446         if (info->host_active == STATE_ERROR) {
 447                 xen_irq_lateeoi(irq, XEN_EOI_FLAG_SPURIOUS);
 448                 return IRQ_HANDLED;
 449         }
 450
 451         while (scsifront_cmd_done(info, &eoiflag))
 452                 /* Yield point for this unbounded loop. */
 453                 cond_resched();
 454
 455         xen_irq_lateeoi(irq, eoiflag);
 456
 457         return IRQ_HANDLED;
 458 }
 459
 460 static void scsifront_finish_all(struct vscsifrnt_info *info)
 461 {
 462         unsigned int i, dummy;
 463         struct vscsiif_response resp;
 464
 465         scsifront_ring_drain(info, &dummy);
 466
 467         for (i = 0; i < VSCSIIF_MAX_REQS; i++) {
 468                 if (test_bit(i, info->shadow_free_bitmap))
 469                         continue;
 470                 resp.rqid = i;
 471                 resp.sense_len = 0;
 472                 resp.rslt = DID_RESET << 16;
 473                 resp.residual_len = 0;
 474                 scsifront_do_response(info, &resp);
 475         }
 476 }
 477
 478 static int map_data_for_request(struct vscsifrnt_info *info,
 479                                 struct scsi_cmnd *sc,
 480                                 struct vscsifrnt_shadow *shadow)
 481 {
 482         grant_ref_t gref_head;
 483         struct page *page;
 484         int err, ref, ref_cnt = 0;
 485         int grant_ro = (sc->sc_data_direction == DMA_TO_DEVICE);
 486         unsigned int i, off, len, bytes;
 487         unsigned int data_len = scsi_bufflen(sc);
 488         unsigned int data_grants = 0, seg_grants = 0;
 489         struct scatterlist *sg;
 490         struct scsiif_request_segment *seg;
 491
 492         if (sc->sc_data_direction == DMA_NONE || !data_len)
 493                 return 0;
 494
 495         scsi_for_each_sg(sc, sg, scsi_sg_count(sc), i)
 496                 data_grants += PFN_UP(sg->offset + sg->length);
 497
 498         if (data_grants > VSCSIIF_SG_TABLESIZE) {
 499                 if (data_grants > info->host->sg_tablesize) {
 500                         shost_printk(KERN_ERR, info->host, KBUILD_MODNAME
 501                              "Unable to map request_buffer for command!\n");
 502                         return -E2BIG;
 503                 }
 504                 seg_grants = vscsiif_grants_sg(data_grants);
 505                 shadow->sg = kcalloc(data_grants,
 506                         sizeof(struct scsiif_request_segment), GFP_ATOMIC);
 507                 if (!shadow->sg)
 508                         return -ENOMEM;
 509         }
 510         seg = shadow->sg ? : shadow->seg;
 511
 512         err = gnttab_alloc_grant_references(seg_grants + data_grants,
 513                                             &gref_head);
 514         if (err) {
 515                 kfree(shadow->sg);
 516                 shost_printk(KERN_ERR, info->host, KBUILD_MODNAME
 517                              "gnttab_alloc_grant_references() error\n");
 518                 return -ENOMEM;
 519         }
 520
 521         if (seg_grants) {
 522                 page = virt_to_page(seg);
 523                 off = offset_in_page(seg);
 524                 len = sizeof(struct scsiif_request_segment) * data_grants;
 525                 while (len > 0) {
 526                         bytes = min_t(unsigned int, len, PAGE_SIZE - off);
 527
 528                         ref = gnttab_claim_grant_reference(&gref_head);
 529                         BUG_ON(ref == -ENOSPC);
 530
 531                         gnttab_grant_foreign_access_ref(ref,
 532                                 info->dev->otherend_id,
 533                                 xen_page_to_gfn(page), 1);
 534                         shadow->gref[ref_cnt] = ref;
 535                         shadow->seg[ref_cnt].gref   = ref;
 536                         shadow->seg[ref_cnt].offset = (uint16_t)off;
 537                         shadow->seg[ref_cnt].length = (uint16_t)bytes;
 538
 539                         page++;
 540                         len -= bytes;
 541                         off = 0;
 542                         ref_cnt++;
 543                 }
 544                 BUG_ON(seg_grants < ref_cnt);
 545                 seg_grants = ref_cnt;
 546         }
 547
 548         scsi_for_each_sg(sc, sg, scsi_sg_count(sc), i) {
 549                 page = sg_page(sg);
 550                 off = sg->offset;
 551                 len = sg->length;
 552
 553                 while (len > 0 && data_len > 0) {
 554                         /*
 555                          * sg sends a scatterlist that is larger than
 556                          * the data_len it wants transferred for certain
 557                          * IO sizes.
 558                          */
 559                         bytes = min_t(unsigned int, len, PAGE_SIZE - off);
 560                         bytes = min(bytes, data_len);
 561
 562                         ref = gnttab_claim_grant_reference(&gref_head);
 563                         BUG_ON(ref == -ENOSPC);
 564
 565                         gnttab_grant_foreign_access_ref(ref,
 566                                 info->dev->otherend_id,
 567                                 xen_page_to_gfn(page),
 568                                 grant_ro);
 569
 570                         shadow->gref[ref_cnt] = ref;
 571                         seg->gref   = ref;
 572                         seg->offset = (uint16_t)off;
 573                         seg->length = (uint16_t)bytes;
 574
 575                         page++;
 576                         seg++;
 577                         len -= bytes;
 578                         data_len -= bytes;
 579                         off = 0;
 580                         ref_cnt++;
 581                 }
 582         }
 583
 584         if (seg_grants)
 585                 shadow->nr_segments = VSCSIIF_SG_GRANT | seg_grants;
 586         else
 587                 shadow->nr_segments = (uint8_t)ref_cnt;
 588         shadow->nr_grants = ref_cnt;
 589
 590         return 0;
 591 }
 592
 593 static int scsifront_enter(struct vscsifrnt_info *info)
 594 {
 595         if (info->pause)
 596                 return 1;
 597         info->callers++;
 598         return 0;
 599 }
 600
 601 static void scsifront_return(struct vscsifrnt_info *info)
 602 {
 603         info->callers--;
 604         if (info->callers)
 605                 return;
 606
 607         if (!info->waiting_pause)
 608                 return;
 609
 610         info->waiting_pause = 0;
 611         wake_up(&info->wq_pause);
 612 }
 613
 614 static int scsifront_queuecommand(struct Scsi_Host *shost,
 615                                   struct scsi_cmnd *sc)
 616 {
 617         struct vscsifrnt_info *info = shost_priv(shost);
 618         struct vscsifrnt_shadow *shadow = scsi_cmd_priv(sc);
 619         unsigned long flags;
 620         int err;
 621
 622         if (info->host_active == STATE_ERROR)
 623                 return SCSI_MLQUEUE_HOST_BUSY;
 624
 625         sc->result = 0;
 626
 627         shadow->sc  = sc;
 628         shadow->act = VSCSIIF_ACT_SCSI_CDB;
 629
 630         spin_lock_irqsave(shost->host_lock, flags);
 631         if (scsifront_enter(info)) {
 632                 spin_unlock_irqrestore(shost->host_lock, flags);
 633                 return SCSI_MLQUEUE_HOST_BUSY;
 634         }
 635
 636         err = map_data_for_request(info, sc, shadow);
 637         if (err < 0) {
 638                 pr_debug("%s: err %d\n", __func__, err);
 639                 scsifront_return(info);
 640                 spin_unlock_irqrestore(shost->host_lock, flags);
 641                 if (err == -ENOMEM)
 642                         return SCSI_MLQUEUE_HOST_BUSY;
 643                 sc->result = DID_ERROR << 16;
 644                 scsi_done(sc);
 645                 return 0;
 646         }
 647
 648         if (scsifront_do_request(info, shadow)) {
 649                 scsifront_gnttab_done(info, shadow);
 650                 goto busy;
 651         }
 652
 653         scsifront_return(info);
 654         spin_unlock_irqrestore(shost->host_lock, flags);
 655
 656         return 0;
 657
 658 busy:
 659         scsifront_return(info);
 660         spin_unlock_irqrestore(shost->host_lock, flags);
 661         pr_debug("%s: busy\n", __func__);
 662         return SCSI_MLQUEUE_HOST_BUSY;
 663 }
 664
 665 /*
 666  * Any exception handling (reset or abort) must be forwarded to the backend.
 667  * We have to wait until an answer is returned. This answer contains the
 668  * result to be returned to the requestor.
 669  */
 670 static int scsifront_action_handler(struct scsi_cmnd *sc, uint8_t act)
 671 {
 672         struct Scsi_Host *host = sc->device->host;
 673         struct vscsifrnt_info *info = shost_priv(host);
 674         struct vscsifrnt_shadow *shadow, *s = scsi_cmd_priv(sc);
 675         int err = 0;
 676
 677         if (info->host_active == STATE_ERROR)
 678                 return FAILED;
 679
 680         shadow = kzalloc(sizeof(*shadow), GFP_NOIO);
 681         if (!shadow)
 682                 return FAILED;
 683
 684         shadow->act = act;
 685         shadow->rslt_reset = RSLT_RESET_WAITING;
 686         shadow->sc = sc;
 687         shadow->ref_rqid = s->rqid;
 688         init_waitqueue_head(&shadow->wq_reset);
 689
 690         spin_lock_irq(host->host_lock);
 691
 692         for (;;) {
 693                 if (scsifront_enter(info))
 694                         goto fail;
 695
 696                 if (!scsifront_do_request(info, shadow))
 697                         break;
 698
 699                 scsifront_return(info);
 700                 if (err)
 701                         goto fail;
 702                 info->wait_ring_available = 1;
 703                 spin_unlock_irq(host->host_lock);
 704                 err = wait_event_interruptible(info->wq_sync,
 705                                                !info->wait_ring_available);
 706                 spin_lock_irq(host->host_lock);
 707         }
 708
 709         spin_unlock_irq(host->host_lock);
 710         err = wait_event_interruptible(shadow->wq_reset, shadow->wait_reset);
 711         spin_lock_irq(host->host_lock);
 712
 713         if (!err) {
 714                 err = shadow->rslt_reset;
 715                 scsifront_put_rqid(info, shadow->rqid);
 716                 kfree(shadow);
 717         } else {
 718                 spin_lock(&info->shadow_lock);
 719                 shadow->rslt_reset = RSLT_RESET_ERR;
 720                 spin_unlock(&info->shadow_lock);
 721                 err = FAILED;
 722         }
 723
 724         scsifront_return(info);
 725         spin_unlock_irq(host->host_lock);
 726         return err;
 727
 728 fail:
 729         spin_unlock_irq(host->host_lock);
 730         kfree(shadow);
 731         return FAILED;
 732 }
 733
 734 static int scsifront_eh_abort_handler(struct scsi_cmnd *sc)
 735 {
 736         pr_debug("%s\n", __func__);
 737         return scsifront_action_handler(sc, VSCSIIF_ACT_SCSI_ABORT);
 738 }
 739
 740 static int scsifront_dev_reset_handler(struct scsi_cmnd *sc)
 741 {
 742         pr_debug("%s\n", __func__);
 743         return scsifront_action_handler(sc, VSCSIIF_ACT_SCSI_RESET);
 744 }
 745
 746 static int scsifront_sdev_configure(struct scsi_device *sdev)
 747 {
 748         struct vscsifrnt_info *info = shost_priv(sdev->host);
 749         int err;
 750
 751         if (info->host_active == STATE_ERROR)
 752                 return -EIO;
 753
 754         if (info && current == info->curr) {
 755                 err = xenbus_printf(XBT_NIL, info->dev->nodename,
 756                               info->dev_state_path, "%d", XenbusStateConnected);
 757                 if (err) {
 758                         xenbus_dev_error(info->dev, err,
 759                                 "%s: writing dev_state_path", __func__);
 760                         return err;
 761                 }
 762         }
 763
 764         return 0;
 765 }
 766
 767 static void scsifront_sdev_destroy(struct scsi_device *sdev)
 768 {
 769         struct vscsifrnt_info *info = shost_priv(sdev->host);
 770         int err;
 771
 772         if (info && current == info->curr) {
 773                 err = xenbus_printf(XBT_NIL, info->dev->nodename,
 774                               info->dev_state_path, "%d", XenbusStateClosed);
 775                 if (err)
 776                         xenbus_dev_error(info->dev, err,
 777                                 "%s: writing dev_state_path", __func__);
 778         }
 779 }
 780
 781 static struct scsi_host_template scsifront_sht = {
 782         .module                 = THIS_MODULE,
 783         .name                   = "Xen SCSI frontend driver",
 784         .queuecommand           = scsifront_queuecommand,
 785         .eh_abort_handler       = scsifront_eh_abort_handler,
 786         .eh_device_reset_handler = scsifront_dev_reset_handler,
 787         .slave_configure        = scsifront_sdev_configure,
 788         .slave_destroy          = scsifront_sdev_destroy,
 789         .cmd_per_lun            = VSCSIIF_DEFAULT_CMD_PER_LUN,
 790         .can_queue              = VSCSIIF_MAX_REQS,
 791         .this_id                = -1,
 792         .cmd_size               = sizeof(struct vscsifrnt_shadow),
 793         .sg_tablesize           = VSCSIIF_SG_TABLESIZE,
 794         .proc_name              = "scsifront",
 795 };
 796
 797 static int scsifront_alloc_ring(struct vscsifrnt_info *info)
 798 {
 799         struct xenbus_device *dev = info->dev;
 800         struct vscsiif_sring *sring;
 801         int err;
 802
 803         /***** Frontend to Backend ring start *****/
 804         err = xenbus_setup_ring(dev, GFP_KERNEL, (void **)&sring, 1,
 805                                 &info->ring_ref);
 806         if (err)
 807                 return err;
 808
 809         XEN_FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
 810
 811         err = xenbus_alloc_evtchn(dev, &info->evtchn);
 812         if (err) {
 813                 xenbus_dev_fatal(dev, err, "xenbus_alloc_evtchn");
 814                 goto free_gnttab;
 815         }
 816
 817         err = bind_evtchn_to_irq_lateeoi(info->evtchn);
 818         if (err <= 0) {
 819                 xenbus_dev_fatal(dev, err, "bind_evtchn_to_irq");
 820                 goto free_gnttab;
 821         }
 822
 823         info->irq = err;
 824
 825         err = request_threaded_irq(info->irq, NULL, scsifront_irq_fn,
 826                                    IRQF_ONESHOT, "scsifront", info);
 827         if (err) {
 828                 xenbus_dev_fatal(dev, err, "request_threaded_irq");
 829                 goto free_irq;
 830         }
 831
 832         return 0;
 833
 834 /* free resource */
 835 free_irq:
 836         unbind_from_irqhandler(info->irq, info);
 837 free_gnttab:
 838         xenbus_teardown_ring((void **)&sring, 1, &info->ring_ref);
 839
 840         return err;
 841 }
 842
 843 static void scsifront_free_ring(struct vscsifrnt_info *info)
 844 {
 845         unbind_from_irqhandler(info->irq, info);
 846         xenbus_teardown_ring((void **)&info->ring.sring, 1, &info->ring_ref);
 847 }
 848
 849 static int scsifront_init_ring(struct vscsifrnt_info *info)
 850 {
 851         struct xenbus_device *dev = info->dev;
 852         struct xenbus_transaction xbt;
 853         int err;
 854
 855         pr_debug("%s\n", __func__);
 856
 857         err = scsifront_alloc_ring(info);
 858         if (err)
 859                 return err;
 860         pr_debug("%s: %u %u\n", __func__, info->ring_ref, info->evtchn);
 861
 862 again:
 863         err = xenbus_transaction_start(&xbt);
 864         if (err)
 865                 xenbus_dev_fatal(dev, err, "starting transaction");
 866
 867         err = xenbus_printf(xbt, dev->nodename, "ring-ref", "%u",
 868                             info->ring_ref);
 869         if (err) {
 870                 xenbus_dev_fatal(dev, err, "%s", "writing ring-ref");
 871                 goto fail;
 872         }
 873
 874         err = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
 875                             info->evtchn);
 876
 877         if (err) {
 878                 xenbus_dev_fatal(dev, err, "%s", "writing event-channel");
 879                 goto fail;
 880         }
 881
 882         err = xenbus_transaction_end(xbt, 0);
 883         if (err) {
 884                 if (err == -EAGAIN)
 885                         goto again;
 886                 xenbus_dev_fatal(dev, err, "completing transaction");
 887                 goto free_sring;
 888         }
 889
 890         return 0;
 891
 892 fail:
 893         xenbus_transaction_end(xbt, 1);
 894 free_sring:
 895         scsifront_free_ring(info);
 896
 897         return err;
 898 }
 899
 900
 901 static int scsifront_probe(struct xenbus_device *dev,
 902                            const struct xenbus_device_id *id)
 903 {
 904         struct vscsifrnt_info *info;
 905         struct Scsi_Host *host;
 906         int err = -ENOMEM;
 907         char name[TASK_COMM_LEN];
 908
 909         host = scsi_host_alloc(&scsifront_sht, sizeof(*info));
 910         if (!host) {
 911                 xenbus_dev_fatal(dev, err, "fail to allocate scsi host");
 912                 return err;
 913         }
 914         info = (struct vscsifrnt_info *)host->hostdata;
 915
 916         dev_set_drvdata(&dev->dev, info);
 917         info->dev = dev;
 918
 919         bitmap_fill(info->shadow_free_bitmap, VSCSIIF_MAX_REQS);
 920
 921         err = scsifront_init_ring(info);
 922         if (err) {
 923                 scsi_host_put(host);
 924                 return err;
 925         }
 926
 927         init_waitqueue_head(&info->wq_sync);
 928         init_waitqueue_head(&info->wq_pause);
 929         spin_lock_init(&info->shadow_lock);
 930
 931         snprintf(name, TASK_COMM_LEN, "vscsiif.%d", host->host_no);
 932
 933         host->max_id      = VSCSIIF_MAX_TARGET;
 934         host->max_channel = 0;
 935         host->max_lun     = VSCSIIF_MAX_LUN;
 936         host->max_sectors = (host->sg_tablesize - 1) * PAGE_SIZE / 512;
 937         host->max_cmd_len = VSCSIIF_MAX_COMMAND_SIZE;
 938
 939         err = scsi_add_host(host, &dev->dev);
 940         if (err) {
 941                 dev_err(&dev->dev, "fail to add scsi host %d\n", err);
 942                 goto free_sring;
 943         }
 944         info->host = host;
 945         info->host_active = STATE_ACTIVE;
 946
 947         xenbus_switch_state(dev, XenbusStateInitialised);
 948
 949         return 0;
 950
 951 free_sring:
 952         scsifront_free_ring(info);
 953         scsi_host_put(host);
 954         return err;
 955 }
 956
 957 static int scsifront_resume(struct xenbus_device *dev)
 958 {
 959         struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
 960         struct Scsi_Host *host = info->host;
 961         int err;
 962
 963         spin_lock_irq(host->host_lock);
 964
 965         /* Finish all still pending commands. */
 966         scsifront_finish_all(info);
 967
 968         spin_unlock_irq(host->host_lock);
 969
 970         /* Reconnect to dom0. */
 971         scsifront_free_ring(info);
 972         err = scsifront_init_ring(info);
 973         if (err) {
 974                 dev_err(&dev->dev, "fail to resume %d\n", err);
 975                 scsi_host_put(host);
 976                 return err;
 977         }
 978
 979         xenbus_switch_state(dev, XenbusStateInitialised);
 980
 981         return 0;
 982 }
 983
 984 static int scsifront_suspend(struct xenbus_device *dev)
 985 {
 986         struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
 987         struct Scsi_Host *host = info->host;
 988         int err = 0;
 989
 990         /* No new commands for the backend. */
 991         spin_lock_irq(host->host_lock);
 992         info->pause = 1;
 993         while (info->callers && !err) {
 994                 info->waiting_pause = 1;
 995                 info->wait_ring_available = 0;
 996                 spin_unlock_irq(host->host_lock);
 997                 wake_up(&info->wq_sync);
 998                 err = wait_event_interruptible(info->wq_pause,
 999                                                !info->waiting_pause);
1000                 spin_lock_irq(host->host_lock);
1001         }
1002         spin_unlock_irq(host->host_lock);
1003         return err;
1004 }
1005
1006 static int scsifront_remove(struct xenbus_device *dev)
1007 {
1008         struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
1009
1010         pr_debug("%s: %s removed\n", __func__, dev->nodename);
1011
1012         mutex_lock(&scsifront_mutex);
1013         if (info->host_active != STATE_INACTIVE) {
1014                 /* Scsi_host not yet removed */
1015                 scsi_remove_host(info->host);
1016                 info->host_active = STATE_INACTIVE;
1017         }
1018         mutex_unlock(&scsifront_mutex);
1019
1020         scsifront_free_ring(info);
1021         scsi_host_put(info->host);
1022
1023         return 0;
1024 }
1025
1026 static void scsifront_disconnect(struct vscsifrnt_info *info)
1027 {
1028         struct xenbus_device *dev = info->dev;
1029         struct Scsi_Host *host = info->host;
1030
1031         pr_debug("%s: %s disconnect\n", __func__, dev->nodename);
1032
1033         /*
1034          * When this function is executed, all devices of
1035          * Frontend have been deleted.
1036          * Therefore, it need not block I/O before remove_host.
1037          */
1038
1039         mutex_lock(&scsifront_mutex);
1040         if (info->host_active != STATE_INACTIVE) {
1041                 scsi_remove_host(host);
1042                 info->host_active = STATE_INACTIVE;
1043         }
1044         mutex_unlock(&scsifront_mutex);
1045
1046         xenbus_frontend_closed(dev);
1047 }
1048
1049 static void scsifront_do_lun_hotplug(struct vscsifrnt_info *info, int op)
1050 {
1051         struct xenbus_device *dev = info->dev;
1052         int i, err = 0;
1053         char str[64];
1054         char **dir;
1055         unsigned int dir_n = 0;
1056         unsigned int device_state;
1057         unsigned int hst, chn, tgt, lun;
1058         struct scsi_device *sdev;
1059
1060         if (info->host_active == STATE_ERROR)
1061                 return;
1062
1063         dir = xenbus_directory(XBT_NIL, dev->otherend, "vscsi-devs", &dir_n);
1064         if (IS_ERR(dir))
1065                 return;
1066
1067         /* mark current task as the one allowed to modify device states */
1068         BUG_ON(info->curr);
1069         info->curr = current;
1070
1071         for (i = 0; i < dir_n; i++) {
1072                 /* read status */
1073                 snprintf(str, sizeof(str), "vscsi-devs/%s/state", dir[i]);
1074                 err = xenbus_scanf(XBT_NIL, dev->otherend, str, "%u",
1075                                    &device_state);
1076                 if (XENBUS_EXIST_ERR(err))
1077                         continue;
1078
1079                 /* virtual SCSI device */
1080                 snprintf(str, sizeof(str), "vscsi-devs/%s/v-dev", dir[i]);
1081                 err = xenbus_scanf(XBT_NIL, dev->otherend, str,
1082                                    "%u:%u:%u:%u", &hst, &chn, &tgt, &lun);
1083                 if (XENBUS_EXIST_ERR(err))
1084                         continue;
1085
1086                 /*
1087                  * Front device state path, used in slave_configure called
1088                  * on successfull scsi_add_device, and in slave_destroy called
1089                  * on remove of a device.
1090                  */
1091                 snprintf(info->dev_state_path, sizeof(info->dev_state_path),
1092                          "vscsi-devs/%s/state", dir[i]);
1093
1094                 switch (op) {
1095                 case VSCSIFRONT_OP_ADD_LUN:
1096                         if (device_state != XenbusStateInitialised)
1097                                 break;
1098
1099                         if (scsi_add_device(info->host, chn, tgt, lun)) {
1100                                 dev_err(&dev->dev, "scsi_add_device\n");
1101                                 err = xenbus_printf(XBT_NIL, dev->nodename,
1102                                               info->dev_state_path,
1103                                               "%d", XenbusStateClosed);
1104                                 if (err)
1105                                         xenbus_dev_error(dev, err,
1106                                                 "%s: writing dev_state_path", __func__);
1107                         }
1108                         break;
1109                 case VSCSIFRONT_OP_DEL_LUN:
1110                         if (device_state != XenbusStateClosing)
1111                                 break;
1112
1113                         sdev = scsi_device_lookup(info->host, chn, tgt, lun);
1114                         if (sdev) {
1115                                 scsi_remove_device(sdev);
1116                                 scsi_device_put(sdev);
1117                         }
1118                         break;
1119                 case VSCSIFRONT_OP_READD_LUN:
1120                         if (device_state == XenbusStateConnected) {
1121                                 err = xenbus_printf(XBT_NIL, dev->nodename,
1122                                               info->dev_state_path,
1123                                               "%d", XenbusStateConnected);
1124                                 if (err)
1125                                         xenbus_dev_error(dev, err,
1126                                                 "%s: writing dev_state_path", __func__);
1127                         }
1128                         break;
1129                 default:
1130                         break;
1131                 }
1132         }
1133
1134         info->curr = NULL;
1135
1136         kfree(dir);
1137 }
1138
1139 static void scsifront_read_backend_params(struct xenbus_device *dev,
1140                                           struct vscsifrnt_info *info)
1141 {
1142         unsigned int sg_grant, nr_segs;
1143         struct Scsi_Host *host = info->host;
1144
1145         sg_grant = xenbus_read_unsigned(dev->otherend, "feature-sg-grant", 0);
1146         nr_segs = min_t(unsigned int, sg_grant, SG_ALL);
1147         nr_segs = max_t(unsigned int, nr_segs, VSCSIIF_SG_TABLESIZE);
1148         nr_segs = min_t(unsigned int, nr_segs,
1149                         VSCSIIF_SG_TABLESIZE * PAGE_SIZE /
1150                         sizeof(struct scsiif_request_segment));
1151
1152         if (!info->pause && sg_grant)
1153                 dev_info(&dev->dev, "using up to %d SG entries\n", nr_segs);
1154         else if (info->pause && nr_segs < host->sg_tablesize)
1155                 dev_warn(&dev->dev,
1156                          "SG entries decreased from %d to %u - device may not work properly anymore\n",
1157                          host->sg_tablesize, nr_segs);
1158
1159         host->sg_tablesize = nr_segs;
1160         host->max_sectors = (nr_segs - 1) * PAGE_SIZE / 512;
1161 }
1162
1163 static void scsifront_backend_changed(struct xenbus_device *dev,
1164                                       enum xenbus_state backend_state)
1165 {
1166         struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
1167
1168         pr_debug("%s: %p %u %u\n", __func__, dev, dev->state, backend_state);
1169
1170         switch (backend_state) {
1171         case XenbusStateUnknown:
1172         case XenbusStateInitialising:
1173         case XenbusStateInitWait:
1174         case XenbusStateInitialised:
1175                 break;
1176
1177         case XenbusStateConnected:
1178                 scsifront_read_backend_params(dev, info);
1179
1180                 if (info->pause) {
1181                         scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_READD_LUN);
1182                         xenbus_switch_state(dev, XenbusStateConnected);
1183                         info->pause = 0;
1184                         return;
1185                 }
1186
1187                 if (xenbus_read_driver_state(dev->nodename) ==
1188                     XenbusStateInitialised)
1189                         scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
1190
1191                 if (dev->state != XenbusStateConnected)
1192                         xenbus_switch_state(dev, XenbusStateConnected);
1193                 break;
1194
1195         case XenbusStateClosed:
1196                 if (dev->state == XenbusStateClosed)
1197                         break;
1198                 fallthrough;    /* Missed the backend's Closing state */
1199         case XenbusStateClosing:
1200                 scsifront_disconnect(info);
1201                 break;
1202
1203         case XenbusStateReconfiguring:
1204                 scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_DEL_LUN);
1205                 xenbus_switch_state(dev, XenbusStateReconfiguring);
1206                 break;
1207
1208         case XenbusStateReconfigured:
1209                 scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
1210                 xenbus_switch_state(dev, XenbusStateConnected);
1211                 break;
1212         }
1213 }
1214
1215 static const struct xenbus_device_id scsifront_ids[] = {
1216         { "vscsi" },
1217         { "" }
1218 };
1219
1220 static struct xenbus_driver scsifront_driver = {
1221         .ids                    = scsifront_ids,
1222         .probe                  = scsifront_probe,
1223         .remove                 = scsifront_remove,
1224         .resume                 = scsifront_resume,
1225         .suspend                = scsifront_suspend,
1226         .otherend_changed       = scsifront_backend_changed,
1227 };
1228
1229 static int __init scsifront_init(void)
1230 {
1231         if (!xen_domain())
1232                 return -ENODEV;
1233
1234         return xenbus_register_frontend(&scsifront_driver);
1235 }
1236 module_init(scsifront_init);
1237
1238 static void __exit scsifront_exit(void)
1239 {
1240         xenbus_unregister_driver(&scsifront_driver);
1241 }
1242 module_exit(scsifront_exit);
1243
1244 MODULE_DESCRIPTION("Xen SCSI frontend driver");
1245 MODULE_LICENSE("GPL");
1246 MODULE_ALIAS("xen:vscsi");
1247 MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");