linux/drivers/vhost/vhost.c
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   1/* Copyright (C) 2009 Red Hat, Inc.
   2 * Copyright (C) 2006 Rusty Russell IBM Corporation
   3 *
   4 * Author: Michael S. Tsirkin <mst@redhat.com>
   5 *
   6 * Inspiration, some code, and most witty comments come from
   7 * Documentation/virtual/lguest/lguest.c, by Rusty Russell
   8 *
   9 * This work is licensed under the terms of the GNU GPL, version 2.
  10 *
  11 * Generic code for virtio server in host kernel.
  12 */
  13
  14#include <linux/eventfd.h>
  15#include <linux/vhost.h>
  16#include <linux/virtio_net.h>
  17#include <linux/mm.h>
  18#include <linux/mmu_context.h>
  19#include <linux/miscdevice.h>
  20#include <linux/mutex.h>
  21#include <linux/rcupdate.h>
  22#include <linux/poll.h>
  23#include <linux/file.h>
  24#include <linux/highmem.h>
  25#include <linux/slab.h>
  26#include <linux/kthread.h>
  27#include <linux/cgroup.h>
  28
  29#include <linux/net.h>
  30#include <linux/if_packet.h>
  31#include <linux/if_arp.h>
  32
  33#include "vhost.h"
  34
  35enum {
  36        VHOST_MEMORY_MAX_NREGIONS = 64,
  37        VHOST_MEMORY_F_LOG = 0x1,
  38};
  39
  40static unsigned vhost_zcopy_mask __read_mostly;
  41
  42#define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
  43#define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])
  44
  45static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
  46                            poll_table *pt)
  47{
  48        struct vhost_poll *poll;
  49
  50        poll = container_of(pt, struct vhost_poll, table);
  51        poll->wqh = wqh;
  52        add_wait_queue(wqh, &poll->wait);
  53}
  54
  55static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
  56                             void *key)
  57{
  58        struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
  59
  60        if (!((unsigned long)key & poll->mask))
  61                return 0;
  62
  63        vhost_poll_queue(poll);
  64        return 0;
  65}
  66
  67void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
  68{
  69        INIT_LIST_HEAD(&work->node);
  70        work->fn = fn;
  71        init_waitqueue_head(&work->done);
  72        work->flushing = 0;
  73        work->queue_seq = work->done_seq = 0;
  74}
  75
  76/* Init poll structure */
  77void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
  78                     unsigned long mask, struct vhost_dev *dev)
  79{
  80        init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
  81        init_poll_funcptr(&poll->table, vhost_poll_func);
  82        poll->mask = mask;
  83        poll->dev = dev;
  84
  85        vhost_work_init(&poll->work, fn);
  86}
  87
  88/* Start polling a file. We add ourselves to file's wait queue. The caller must
  89 * keep a reference to a file until after vhost_poll_stop is called. */
  90void vhost_poll_start(struct vhost_poll *poll, struct file *file)
  91{
  92        unsigned long mask;
  93
  94        mask = file->f_op->poll(file, &poll->table);
  95        if (mask)
  96                vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
  97}
  98
  99/* Stop polling a file. After this function returns, it becomes safe to drop the
 100 * file reference. You must also flush afterwards. */
 101void vhost_poll_stop(struct vhost_poll *poll)
 102{
 103        remove_wait_queue(poll->wqh, &poll->wait);
 104}
 105
 106static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
 107                                unsigned seq)
 108{
 109        int left;
 110
 111        spin_lock_irq(&dev->work_lock);
 112        left = seq - work->done_seq;
 113        spin_unlock_irq(&dev->work_lock);
 114        return left <= 0;
 115}
 116
 117static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
 118{
 119        unsigned seq;
 120        int flushing;
 121
 122        spin_lock_irq(&dev->work_lock);
 123        seq = work->queue_seq;
 124        work->flushing++;
 125        spin_unlock_irq(&dev->work_lock);
 126        wait_event(work->done, vhost_work_seq_done(dev, work, seq));
 127        spin_lock_irq(&dev->work_lock);
 128        flushing = --work->flushing;
 129        spin_unlock_irq(&dev->work_lock);
 130        BUG_ON(flushing < 0);
 131}
 132
 133/* Flush any work that has been scheduled. When calling this, don't hold any
 134 * locks that are also used by the callback. */
 135void vhost_poll_flush(struct vhost_poll *poll)
 136{
 137        vhost_work_flush(poll->dev, &poll->work);
 138}
 139
 140void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 141{
 142        unsigned long flags;
 143
 144        spin_lock_irqsave(&dev->work_lock, flags);
 145        if (list_empty(&work->node)) {
 146                list_add_tail(&work->node, &dev->work_list);
 147                work->queue_seq++;
 148                wake_up_process(dev->worker);
 149        }
 150        spin_unlock_irqrestore(&dev->work_lock, flags);
 151}
 152
 153void vhost_poll_queue(struct vhost_poll *poll)
 154{
 155        vhost_work_queue(poll->dev, &poll->work);
 156}
 157
 158static void vhost_vq_reset(struct vhost_dev *dev,
 159                           struct vhost_virtqueue *vq)
 160{
 161        vq->num = 1;
 162        vq->desc = NULL;
 163        vq->avail = NULL;
 164        vq->used = NULL;
 165        vq->last_avail_idx = 0;
 166        vq->avail_idx = 0;
 167        vq->last_used_idx = 0;
 168        vq->signalled_used = 0;
 169        vq->signalled_used_valid = false;
 170        vq->used_flags = 0;
 171        vq->log_used = false;
 172        vq->log_addr = -1ull;
 173        vq->vhost_hlen = 0;
 174        vq->sock_hlen = 0;
 175        vq->private_data = NULL;
 176        vq->log_base = NULL;
 177        vq->error_ctx = NULL;
 178        vq->error = NULL;
 179        vq->kick = NULL;
 180        vq->call_ctx = NULL;
 181        vq->call = NULL;
 182        vq->log_ctx = NULL;
 183        vq->upend_idx = 0;
 184        vq->done_idx = 0;
 185        vq->ubufs = NULL;
 186}
 187
 188static int vhost_worker(void *data)
 189{
 190        struct vhost_dev *dev = data;
 191        struct vhost_work *work = NULL;
 192        unsigned uninitialized_var(seq);
 193        mm_segment_t oldfs = get_fs();
 194
 195        set_fs(USER_DS);
 196        use_mm(dev->mm);
 197
 198        for (;;) {
 199                /* mb paired w/ kthread_stop */
 200                set_current_state(TASK_INTERRUPTIBLE);
 201
 202                spin_lock_irq(&dev->work_lock);
 203                if (work) {
 204                        work->done_seq = seq;
 205                        if (work->flushing)
 206                                wake_up_all(&work->done);
 207                }
 208
 209                if (kthread_should_stop()) {
 210                        spin_unlock_irq(&dev->work_lock);
 211                        __set_current_state(TASK_RUNNING);
 212                        break;
 213                }
 214                if (!list_empty(&dev->work_list)) {
 215                        work = list_first_entry(&dev->work_list,
 216                                                struct vhost_work, node);
 217                        list_del_init(&work->node);
 218                        seq = work->queue_seq;
 219                } else
 220                        work = NULL;
 221                spin_unlock_irq(&dev->work_lock);
 222
 223                if (work) {
 224                        __set_current_state(TASK_RUNNING);
 225                        work->fn(work);
 226                        if (need_resched())
 227                                schedule();
 228                } else
 229                        schedule();
 230
 231        }
 232        unuse_mm(dev->mm);
 233        set_fs(oldfs);
 234        return 0;
 235}
 236
 237static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
 238{
 239        kfree(vq->indirect);
 240        vq->indirect = NULL;
 241        kfree(vq->log);
 242        vq->log = NULL;
 243        kfree(vq->heads);
 244        vq->heads = NULL;
 245        kfree(vq->ubuf_info);
 246        vq->ubuf_info = NULL;
 247}
 248
 249void vhost_enable_zcopy(int vq)
 250{
 251        vhost_zcopy_mask |= 0x1 << vq;
 252}
 253
 254/* Helper to allocate iovec buffers for all vqs. */
 255static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
 256{
 257        int i;
 258        bool zcopy;
 259
 260        for (i = 0; i < dev->nvqs; ++i) {
 261                dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
 262                                               UIO_MAXIOV, GFP_KERNEL);
 263                dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
 264                                          GFP_KERNEL);
 265                dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
 266                                            UIO_MAXIOV, GFP_KERNEL);
 267                zcopy = vhost_zcopy_mask & (0x1 << i);
 268                if (zcopy)
 269                        dev->vqs[i].ubuf_info =
 270                                kmalloc(sizeof *dev->vqs[i].ubuf_info *
 271                                        UIO_MAXIOV, GFP_KERNEL);
 272                if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
 273                        !dev->vqs[i].heads ||
 274                        (zcopy && !dev->vqs[i].ubuf_info))
 275                        goto err_nomem;
 276        }
 277        return 0;
 278
 279err_nomem:
 280        for (; i >= 0; --i)
 281                vhost_vq_free_iovecs(&dev->vqs[i]);
 282        return -ENOMEM;
 283}
 284
 285static void vhost_dev_free_iovecs(struct vhost_dev *dev)
 286{
 287        int i;
 288
 289        for (i = 0; i < dev->nvqs; ++i)
 290                vhost_vq_free_iovecs(&dev->vqs[i]);
 291}
 292
 293long vhost_dev_init(struct vhost_dev *dev,
 294                    struct vhost_virtqueue *vqs, int nvqs)
 295{
 296        int i;
 297
 298        dev->vqs = vqs;
 299        dev->nvqs = nvqs;
 300        mutex_init(&dev->mutex);
 301        dev->log_ctx = NULL;
 302        dev->log_file = NULL;
 303        dev->memory = NULL;
 304        dev->mm = NULL;
 305        spin_lock_init(&dev->work_lock);
 306        INIT_LIST_HEAD(&dev->work_list);
 307        dev->worker = NULL;
 308
 309        for (i = 0; i < dev->nvqs; ++i) {
 310                dev->vqs[i].log = NULL;
 311                dev->vqs[i].indirect = NULL;
 312                dev->vqs[i].heads = NULL;
 313                dev->vqs[i].ubuf_info = NULL;
 314                dev->vqs[i].dev = dev;
 315                mutex_init(&dev->vqs[i].mutex);
 316                vhost_vq_reset(dev, dev->vqs + i);
 317                if (dev->vqs[i].handle_kick)
 318                        vhost_poll_init(&dev->vqs[i].poll,
 319                                        dev->vqs[i].handle_kick, POLLIN, dev);
 320        }
 321
 322        return 0;
 323}
 324
 325/* Caller should have device mutex */
 326long vhost_dev_check_owner(struct vhost_dev *dev)
 327{
 328        /* Are you the owner? If not, I don't think you mean to do that */
 329        return dev->mm == current->mm ? 0 : -EPERM;
 330}
 331
 332struct vhost_attach_cgroups_struct {
 333        struct vhost_work work;
 334        struct task_struct *owner;
 335        int ret;
 336};
 337
 338static void vhost_attach_cgroups_work(struct vhost_work *work)
 339{
 340        struct vhost_attach_cgroups_struct *s;
 341
 342        s = container_of(work, struct vhost_attach_cgroups_struct, work);
 343        s->ret = cgroup_attach_task_all(s->owner, current);
 344}
 345
 346static int vhost_attach_cgroups(struct vhost_dev *dev)
 347{
 348        struct vhost_attach_cgroups_struct attach;
 349
 350        attach.owner = current;
 351        vhost_work_init(&attach.work, vhost_attach_cgroups_work);
 352        vhost_work_queue(dev, &attach.work);
 353        vhost_work_flush(dev, &attach.work);
 354        return attach.ret;
 355}
 356
 357/* Caller should have device mutex */
 358static long vhost_dev_set_owner(struct vhost_dev *dev)
 359{
 360        struct task_struct *worker;
 361        int err;
 362
 363        /* Is there an owner already? */
 364        if (dev->mm) {
 365                err = -EBUSY;
 366                goto err_mm;
 367        }
 368
 369        /* No owner, become one */
 370        dev->mm = get_task_mm(current);
 371        worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
 372        if (IS_ERR(worker)) {
 373                err = PTR_ERR(worker);
 374                goto err_worker;
 375        }
 376
 377        dev->worker = worker;
 378        wake_up_process(worker);        /* avoid contributing to loadavg */
 379
 380        err = vhost_attach_cgroups(dev);
 381        if (err)
 382                goto err_cgroup;
 383
 384        err = vhost_dev_alloc_iovecs(dev);
 385        if (err)
 386                goto err_cgroup;
 387
 388        return 0;
 389err_cgroup:
 390        kthread_stop(worker);
 391        dev->worker = NULL;
 392err_worker:
 393        if (dev->mm)
 394                mmput(dev->mm);
 395        dev->mm = NULL;
 396err_mm:
 397        return err;
 398}
 399
 400/* Caller should have device mutex */
 401long vhost_dev_reset_owner(struct vhost_dev *dev)
 402{
 403        struct vhost_memory *memory;
 404
 405        /* Restore memory to default empty mapping. */
 406        memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
 407        if (!memory)
 408                return -ENOMEM;
 409
 410        vhost_dev_cleanup(dev, true);
 411
 412        memory->nregions = 0;
 413        RCU_INIT_POINTER(dev->memory, memory);
 414        return 0;
 415}
 416
 417/* In case of DMA done not in order in lower device driver for some reason.
 418 * upend_idx is used to track end of used idx, done_idx is used to track head
 419 * of used idx. Once lower device DMA done contiguously, we will signal KVM
 420 * guest used idx.
 421 */
 422int vhost_zerocopy_signal_used(struct vhost_virtqueue *vq)
 423{
 424        int i;
 425        int j = 0;
 426
 427        for (i = vq->done_idx; i != vq->upend_idx; i = (i + 1) % UIO_MAXIOV) {
 428                if ((vq->heads[i].len == VHOST_DMA_DONE_LEN)) {
 429                        vq->heads[i].len = VHOST_DMA_CLEAR_LEN;
 430                        vhost_add_used_and_signal(vq->dev, vq,
 431                                                  vq->heads[i].id, 0);
 432                        ++j;
 433                } else
 434                        break;
 435        }
 436        if (j)
 437                vq->done_idx = i;
 438        return j;
 439}
 440
 441/* Caller should have device mutex if and only if locked is set */
 442void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
 443{
 444        int i;
 445
 446        for (i = 0; i < dev->nvqs; ++i) {
 447                if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
 448                        vhost_poll_stop(&dev->vqs[i].poll);
 449                        vhost_poll_flush(&dev->vqs[i].poll);
 450                }
 451                /* Wait for all lower device DMAs done. */
 452                if (dev->vqs[i].ubufs)
 453                        vhost_ubuf_put_and_wait(dev->vqs[i].ubufs);
 454
 455                /* Signal guest as appropriate. */
 456                vhost_zerocopy_signal_used(&dev->vqs[i]);
 457
 458                if (dev->vqs[i].error_ctx)
 459                        eventfd_ctx_put(dev->vqs[i].error_ctx);
 460                if (dev->vqs[i].error)
 461                        fput(dev->vqs[i].error);
 462                if (dev->vqs[i].kick)
 463                        fput(dev->vqs[i].kick);
 464                if (dev->vqs[i].call_ctx)
 465                        eventfd_ctx_put(dev->vqs[i].call_ctx);
 466                if (dev->vqs[i].call)
 467                        fput(dev->vqs[i].call);
 468                vhost_vq_reset(dev, dev->vqs + i);
 469        }
 470        vhost_dev_free_iovecs(dev);
 471        if (dev->log_ctx)
 472                eventfd_ctx_put(dev->log_ctx);
 473        dev->log_ctx = NULL;
 474        if (dev->log_file)
 475                fput(dev->log_file);
 476        dev->log_file = NULL;
 477        /* No one will access memory at this point */
 478        kfree(rcu_dereference_protected(dev->memory,
 479                                        locked ==
 480                                                lockdep_is_held(&dev->mutex)));
 481        RCU_INIT_POINTER(dev->memory, NULL);
 482        WARN_ON(!list_empty(&dev->work_list));
 483        if (dev->worker) {
 484                kthread_stop(dev->worker);
 485                dev->worker = NULL;
 486        }
 487        if (dev->mm)
 488                mmput(dev->mm);
 489        dev->mm = NULL;
 490}
 491
 492static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 493{
 494        u64 a = addr / VHOST_PAGE_SIZE / 8;
 495
 496        /* Make sure 64 bit math will not overflow. */
 497        if (a > ULONG_MAX - (unsigned long)log_base ||
 498            a + (unsigned long)log_base > ULONG_MAX)
 499                return 0;
 500
 501        return access_ok(VERIFY_WRITE, log_base + a,
 502                         (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
 503}
 504
 505/* Caller should have vq mutex and device mutex. */
 506static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
 507                               int log_all)
 508{
 509        int i;
 510
 511        if (!mem)
 512                return 0;
 513
 514        for (i = 0; i < mem->nregions; ++i) {
 515                struct vhost_memory_region *m = mem->regions + i;
 516                unsigned long a = m->userspace_addr;
 517                if (m->memory_size > ULONG_MAX)
 518                        return 0;
 519                else if (!access_ok(VERIFY_WRITE, (void __user *)a,
 520                                    m->memory_size))
 521                        return 0;
 522                else if (log_all && !log_access_ok(log_base,
 523                                                   m->guest_phys_addr,
 524                                                   m->memory_size))
 525                        return 0;
 526        }
 527        return 1;
 528}
 529
 530/* Can we switch to this memory table? */
 531/* Caller should have device mutex but not vq mutex */
 532static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
 533                            int log_all)
 534{
 535        int i;
 536
 537        for (i = 0; i < d->nvqs; ++i) {
 538                int ok;
 539                mutex_lock(&d->vqs[i].mutex);
 540                /* If ring is inactive, will check when it's enabled. */
 541                if (d->vqs[i].private_data)
 542                        ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
 543                                                 log_all);
 544                else
 545                        ok = 1;
 546                mutex_unlock(&d->vqs[i].mutex);
 547                if (!ok)
 548                        return 0;
 549        }
 550        return 1;
 551}
 552
 553static int vq_access_ok(struct vhost_dev *d, unsigned int num,
 554                        struct vring_desc __user *desc,
 555                        struct vring_avail __user *avail,
 556                        struct vring_used __user *used)
 557{
 558        size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 559        return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
 560               access_ok(VERIFY_READ, avail,
 561                         sizeof *avail + num * sizeof *avail->ring + s) &&
 562               access_ok(VERIFY_WRITE, used,
 563                        sizeof *used + num * sizeof *used->ring + s);
 564}
 565
 566/* Can we log writes? */
 567/* Caller should have device mutex but not vq mutex */
 568int vhost_log_access_ok(struct vhost_dev *dev)
 569{
 570        struct vhost_memory *mp;
 571
 572        mp = rcu_dereference_protected(dev->memory,
 573                                       lockdep_is_held(&dev->mutex));
 574        return memory_access_ok(dev, mp, 1);
 575}
 576
 577/* Verify access for write logging. */
 578/* Caller should have vq mutex and device mutex */
 579static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue *vq,
 580                            void __user *log_base)
 581{
 582        struct vhost_memory *mp;
 583        size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 584
 585        mp = rcu_dereference_protected(vq->dev->memory,
 586                                       lockdep_is_held(&vq->mutex));
 587        return vq_memory_access_ok(log_base, mp,
 588                            vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
 589                (!vq->log_used || log_access_ok(log_base, vq->log_addr,
 590                                        sizeof *vq->used +
 591                                        vq->num * sizeof *vq->used->ring + s));
 592}
 593
 594/* Can we start vq? */
 595/* Caller should have vq mutex and device mutex */
 596int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 597{
 598        return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail, vq->used) &&
 599                vq_log_access_ok(vq->dev, vq, vq->log_base);
 600}
 601
 602static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 603{
 604        struct vhost_memory mem, *newmem, *oldmem;
 605        unsigned long size = offsetof(struct vhost_memory, regions);
 606
 607        if (copy_from_user(&mem, m, size))
 608                return -EFAULT;
 609        if (mem.padding)
 610                return -EOPNOTSUPP;
 611        if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
 612                return -E2BIG;
 613        newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
 614        if (!newmem)
 615                return -ENOMEM;
 616
 617        memcpy(newmem, &mem, size);
 618        if (copy_from_user(newmem->regions, m->regions,
 619                           mem.nregions * sizeof *m->regions)) {
 620                kfree(newmem);
 621                return -EFAULT;
 622        }
 623
 624        if (!memory_access_ok(d, newmem,
 625                              vhost_has_feature(d, VHOST_F_LOG_ALL))) {
 626                kfree(newmem);
 627                return -EFAULT;
 628        }
 629        oldmem = rcu_dereference_protected(d->memory,
 630                                           lockdep_is_held(&d->mutex));
 631        rcu_assign_pointer(d->memory, newmem);
 632        synchronize_rcu();
 633        kfree(oldmem);
 634        return 0;
 635}
 636
 637static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 638{
 639        struct file *eventfp, *filep = NULL,
 640                    *pollstart = NULL, *pollstop = NULL;
 641        struct eventfd_ctx *ctx = NULL;
 642        u32 __user *idxp = argp;
 643        struct vhost_virtqueue *vq;
 644        struct vhost_vring_state s;
 645        struct vhost_vring_file f;
 646        struct vhost_vring_addr a;
 647        u32 idx;
 648        long r;
 649
 650        r = get_user(idx, idxp);
 651        if (r < 0)
 652                return r;
 653        if (idx >= d->nvqs)
 654                return -ENOBUFS;
 655
 656        vq = d->vqs + idx;
 657
 658        mutex_lock(&vq->mutex);
 659
 660        switch (ioctl) {
 661        case VHOST_SET_VRING_NUM:
 662                /* Resizing ring with an active backend?
 663                 * You don't want to do that. */
 664                if (vq->private_data) {
 665                        r = -EBUSY;
 666                        break;
 667                }
 668                if (copy_from_user(&s, argp, sizeof s)) {
 669                        r = -EFAULT;
 670                        break;
 671                }
 672                if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
 673                        r = -EINVAL;
 674                        break;
 675                }
 676                vq->num = s.num;
 677                break;
 678        case VHOST_SET_VRING_BASE:
 679                /* Moving base with an active backend?
 680                 * You don't want to do that. */
 681                if (vq->private_data) {
 682                        r = -EBUSY;
 683                        break;
 684                }
 685                if (copy_from_user(&s, argp, sizeof s)) {
 686                        r = -EFAULT;
 687                        break;
 688                }
 689                if (s.num > 0xffff) {
 690                        r = -EINVAL;
 691                        break;
 692                }
 693                vq->last_avail_idx = s.num;
 694                /* Forget the cached index value. */
 695                vq->avail_idx = vq->last_avail_idx;
 696                break;
 697        case VHOST_GET_VRING_BASE:
 698                s.index = idx;
 699                s.num = vq->last_avail_idx;
 700                if (copy_to_user(argp, &s, sizeof s))
 701                        r = -EFAULT;
 702                break;
 703        case VHOST_SET_VRING_ADDR:
 704                if (copy_from_user(&a, argp, sizeof a)) {
 705                        r = -EFAULT;
 706                        break;
 707                }
 708                if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
 709                        r = -EOPNOTSUPP;
 710                        break;
 711                }
 712                /* For 32bit, verify that the top 32bits of the user
 713                   data are set to zero. */
 714                if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
 715                    (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
 716                    (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
 717                        r = -EFAULT;
 718                        break;
 719                }
 720                if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
 721                    (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
 722                    (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
 723                        r = -EINVAL;
 724                        break;
 725                }
 726
 727                /* We only verify access here if backend is configured.
 728                 * If it is not, we don't as size might not have been setup.
 729                 * We will verify when backend is configured. */
 730                if (vq->private_data) {
 731                        if (!vq_access_ok(d, vq->num,
 732                                (void __user *)(unsigned long)a.desc_user_addr,
 733                                (void __user *)(unsigned long)a.avail_user_addr,
 734                                (void __user *)(unsigned long)a.used_user_addr)) {
 735                                r = -EINVAL;
 736                                break;
 737                        }
 738
 739                        /* Also validate log access for used ring if enabled. */
 740                        if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
 741                            !log_access_ok(vq->log_base, a.log_guest_addr,
 742                                           sizeof *vq->used +
 743                                           vq->num * sizeof *vq->used->ring)) {
 744                                r = -EINVAL;
 745                                break;
 746                        }
 747                }
 748
 749                vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
 750                vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
 751                vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
 752                vq->log_addr = a.log_guest_addr;
 753                vq->used = (void __user *)(unsigned long)a.used_user_addr;
 754                break;
 755        case VHOST_SET_VRING_KICK:
 756                if (copy_from_user(&f, argp, sizeof f)) {
 757                        r = -EFAULT;
 758                        break;
 759                }
 760                eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 761                if (IS_ERR(eventfp)) {
 762                        r = PTR_ERR(eventfp);
 763                        break;
 764                }
 765                if (eventfp != vq->kick) {
 766                        pollstop = filep = vq->kick;
 767                        pollstart = vq->kick = eventfp;
 768                } else
 769                        filep = eventfp;
 770                break;
 771        case VHOST_SET_VRING_CALL:
 772                if (copy_from_user(&f, argp, sizeof f)) {
 773                        r = -EFAULT;
 774                        break;
 775                }
 776                eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 777                if (IS_ERR(eventfp)) {
 778                        r = PTR_ERR(eventfp);
 779                        break;
 780                }
 781                if (eventfp != vq->call) {
 782                        filep = vq->call;
 783                        ctx = vq->call_ctx;
 784                        vq->call = eventfp;
 785                        vq->call_ctx = eventfp ?
 786                                eventfd_ctx_fileget(eventfp) : NULL;
 787                } else
 788                        filep = eventfp;
 789                break;
 790        case VHOST_SET_VRING_ERR:
 791                if (copy_from_user(&f, argp, sizeof f)) {
 792                        r = -EFAULT;
 793                        break;
 794                }
 795                eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 796                if (IS_ERR(eventfp)) {
 797                        r = PTR_ERR(eventfp);
 798                        break;
 799                }
 800                if (eventfp != vq->error) {
 801                        filep = vq->error;
 802                        vq->error = eventfp;
 803                        ctx = vq->error_ctx;
 804                        vq->error_ctx = eventfp ?
 805                                eventfd_ctx_fileget(eventfp) : NULL;
 806                } else
 807                        filep = eventfp;
 808                break;
 809        default:
 810                r = -ENOIOCTLCMD;
 811        }
 812
 813        if (pollstop && vq->handle_kick)
 814                vhost_poll_stop(&vq->poll);
 815
 816        if (ctx)
 817                eventfd_ctx_put(ctx);
 818        if (filep)
 819                fput(filep);
 820
 821        if (pollstart && vq->handle_kick)
 822                vhost_poll_start(&vq->poll, vq->kick);
 823
 824        mutex_unlock(&vq->mutex);
 825
 826        if (pollstop && vq->handle_kick)
 827                vhost_poll_flush(&vq->poll);
 828        return r;
 829}
 830
 831/* Caller must have device mutex */
 832long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
 833{
 834        void __user *argp = (void __user *)arg;
 835        struct file *eventfp, *filep = NULL;
 836        struct eventfd_ctx *ctx = NULL;
 837        u64 p;
 838        long r;
 839        int i, fd;
 840
 841        /* If you are not the owner, you can become one */
 842        if (ioctl == VHOST_SET_OWNER) {
 843                r = vhost_dev_set_owner(d);
 844                goto done;
 845        }
 846
 847        /* You must be the owner to do anything else */
 848        r = vhost_dev_check_owner(d);
 849        if (r)
 850                goto done;
 851
 852        switch (ioctl) {
 853        case VHOST_SET_MEM_TABLE:
 854                r = vhost_set_memory(d, argp);
 855                break;
 856        case VHOST_SET_LOG_BASE:
 857                if (copy_from_user(&p, argp, sizeof p)) {
 858                        r = -EFAULT;
 859                        break;
 860                }
 861                if ((u64)(unsigned long)p != p) {
 862                        r = -EFAULT;
 863                        break;
 864                }
 865                for (i = 0; i < d->nvqs; ++i) {
 866                        struct vhost_virtqueue *vq;
 867                        void __user *base = (void __user *)(unsigned long)p;
 868                        vq = d->vqs + i;
 869                        mutex_lock(&vq->mutex);
 870                        /* If ring is inactive, will check when it's enabled. */
 871                        if (vq->private_data && !vq_log_access_ok(d, vq, base))
 872                                r = -EFAULT;
 873                        else
 874                                vq->log_base = base;
 875                        mutex_unlock(&vq->mutex);
 876                }
 877                break;
 878        case VHOST_SET_LOG_FD:
 879                r = get_user(fd, (int __user *)argp);
 880                if (r < 0)
 881                        break;
 882                eventfp = fd == -1 ? NULL : eventfd_fget(fd);
 883                if (IS_ERR(eventfp)) {
 884                        r = PTR_ERR(eventfp);
 885                        break;
 886                }
 887                if (eventfp != d->log_file) {
 888                        filep = d->log_file;
 889                        ctx = d->log_ctx;
 890                        d->log_ctx = eventfp ?
 891                                eventfd_ctx_fileget(eventfp) : NULL;
 892                } else
 893                        filep = eventfp;
 894                for (i = 0; i < d->nvqs; ++i) {
 895                        mutex_lock(&d->vqs[i].mutex);
 896                        d->vqs[i].log_ctx = d->log_ctx;
 897                        mutex_unlock(&d->vqs[i].mutex);
 898                }
 899                if (ctx)
 900                        eventfd_ctx_put(ctx);
 901                if (filep)
 902                        fput(filep);
 903                break;
 904        default:
 905                r = vhost_set_vring(d, ioctl, argp);
 906                break;
 907        }
 908done:
 909        return r;
 910}
 911
 912static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
 913                                                     __u64 addr, __u32 len)
 914{
 915        struct vhost_memory_region *reg;
 916        int i;
 917
 918        /* linear search is not brilliant, but we really have on the order of 6
 919         * regions in practice */
 920        for (i = 0; i < mem->nregions; ++i) {
 921                reg = mem->regions + i;
 922                if (reg->guest_phys_addr <= addr &&
 923                    reg->guest_phys_addr + reg->memory_size - 1 >= addr)
 924                        return reg;
 925        }
 926        return NULL;
 927}
 928
 929/* TODO: This is really inefficient.  We need something like get_user()
 930 * (instruction directly accesses the data, with an exception table entry
 931 * returning -EFAULT). See Documentation/x86/exception-tables.txt.
 932 */
 933static int set_bit_to_user(int nr, void __user *addr)
 934{
 935        unsigned long log = (unsigned long)addr;
 936        struct page *page;
 937        void *base;
 938        int bit = nr + (log % PAGE_SIZE) * 8;
 939        int r;
 940
 941        r = get_user_pages_fast(log, 1, 1, &page);
 942        if (r < 0)
 943                return r;
 944        BUG_ON(r != 1);
 945        base = kmap_atomic(page);
 946        set_bit(bit, base);
 947        kunmap_atomic(base);
 948        set_page_dirty_lock(page);
 949        put_page(page);
 950        return 0;
 951}
 952
 953static int log_write(void __user *log_base,
 954                     u64 write_address, u64 write_length)
 955{
 956        u64 write_page = write_address / VHOST_PAGE_SIZE;
 957        int r;
 958
 959        if (!write_length)
 960                return 0;
 961        write_length += write_address % VHOST_PAGE_SIZE;
 962        for (;;) {
 963                u64 base = (u64)(unsigned long)log_base;
 964                u64 log = base + write_page / 8;
 965                int bit = write_page % 8;
 966                if ((u64)(unsigned long)log != log)
 967                        return -EFAULT;
 968                r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
 969                if (r < 0)
 970                        return r;
 971                if (write_length <= VHOST_PAGE_SIZE)
 972                        break;
 973                write_length -= VHOST_PAGE_SIZE;
 974                write_page += 1;
 975        }
 976        return r;
 977}
 978
 979int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
 980                    unsigned int log_num, u64 len)
 981{
 982        int i, r;
 983
 984        /* Make sure data written is seen before log. */
 985        smp_wmb();
 986        for (i = 0; i < log_num; ++i) {
 987                u64 l = min(log[i].len, len);
 988                r = log_write(vq->log_base, log[i].addr, l);
 989                if (r < 0)
 990                        return r;
 991                len -= l;
 992                if (!len) {
 993                        if (vq->log_ctx)
 994                                eventfd_signal(vq->log_ctx, 1);
 995                        return 0;
 996                }
 997        }
 998        /* Length written exceeds what we have stored. This is a bug. */
 999        BUG();
1000        return 0;
1001}
1002
1003static int vhost_update_used_flags(struct vhost_virtqueue *vq)
1004{
1005        void __user *used;
1006        if (__put_user(vq->used_flags, &vq->used->flags) < 0)
1007                return -EFAULT;
1008        if (unlikely(vq->log_used)) {
1009                /* Make sure the flag is seen before log. */
1010                smp_wmb();
1011                /* Log used flag write. */
1012                used = &vq->used->flags;
1013                log_write(vq->log_base, vq->log_addr +
1014                          (used - (void __user *)vq->used),
1015                          sizeof vq->used->flags);
1016                if (vq->log_ctx)
1017                        eventfd_signal(vq->log_ctx, 1);
1018        }
1019        return 0;
1020}
1021
1022static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
1023{
1024        if (__put_user(vq->avail_idx, vhost_avail_event(vq)))
1025                return -EFAULT;
1026        if (unlikely(vq->log_used)) {
1027                void __user *used;
1028                /* Make sure the event is seen before log. */
1029                smp_wmb();
1030                /* Log avail event write */
1031                used = vhost_avail_event(vq);
1032                log_write(vq->log_base, vq->log_addr +
1033                          (used - (void __user *)vq->used),
1034                          sizeof *vhost_avail_event(vq));
1035                if (vq->log_ctx)
1036                        eventfd_signal(vq->log_ctx, 1);
1037        }
1038        return 0;
1039}
1040
1041int vhost_init_used(struct vhost_virtqueue *vq)
1042{
1043        int r;
1044        if (!vq->private_data)
1045                return 0;
1046
1047        r = vhost_update_used_flags(vq);
1048        if (r)
1049                return r;
1050        vq->signalled_used_valid = false;
1051        return get_user(vq->last_used_idx, &vq->used->idx);
1052}
1053
1054static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
1055                          struct iovec iov[], int iov_size)
1056{
1057        const struct vhost_memory_region *reg;
1058        struct vhost_memory *mem;
1059        struct iovec *_iov;
1060        u64 s = 0;
1061        int ret = 0;
1062
1063        rcu_read_lock();
1064
1065        mem = rcu_dereference(dev->memory);
1066        while ((u64)len > s) {
1067                u64 size;
1068                if (unlikely(ret >= iov_size)) {
1069                        ret = -ENOBUFS;
1070                        break;
1071                }
1072                reg = find_region(mem, addr, len);
1073                if (unlikely(!reg)) {
1074                        ret = -EFAULT;
1075                        break;
1076                }
1077                _iov = iov + ret;
1078                size = reg->memory_size - addr + reg->guest_phys_addr;
1079                _iov->iov_len = min((u64)len, size);
1080                _iov->iov_base = (void __user *)(unsigned long)
1081                        (reg->userspace_addr + addr - reg->guest_phys_addr);
1082                s += size;
1083                addr += size;
1084                ++ret;
1085        }
1086
1087        rcu_read_unlock();
1088        return ret;
1089}
1090
1091/* Each buffer in the virtqueues is actually a chain of descriptors.  This
1092 * function returns the next descriptor in the chain,
1093 * or -1U if we're at the end. */
1094static unsigned next_desc(struct vring_desc *desc)
1095{
1096        unsigned int next;
1097
1098        /* If this descriptor says it doesn't chain, we're done. */
1099        if (!(desc->flags & VRING_DESC_F_NEXT))
1100                return -1U;
1101
1102        /* Check they're not leading us off end of descriptors. */
1103        next = desc->next;
1104        /* Make sure compiler knows to grab that: we don't want it changing! */
1105        /* We will use the result as an index in an array, so most
1106         * architectures only need a compiler barrier here. */
1107        read_barrier_depends();
1108
1109        return next;
1110}
1111
1112static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1113                        struct iovec iov[], unsigned int iov_size,
1114                        unsigned int *out_num, unsigned int *in_num,
1115                        struct vhost_log *log, unsigned int *log_num,
1116                        struct vring_desc *indirect)
1117{
1118        struct vring_desc desc;
1119        unsigned int i = 0, count, found = 0;
1120        int ret;
1121
1122        /* Sanity check */
1123        if (unlikely(indirect->len % sizeof desc)) {
1124                vq_err(vq, "Invalid length in indirect descriptor: "
1125                       "len 0x%llx not multiple of 0x%zx\n",
1126                       (unsigned long long)indirect->len,
1127                       sizeof desc);
1128                return -EINVAL;
1129        }
1130
1131        ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
1132                             UIO_MAXIOV);
1133        if (unlikely(ret < 0)) {
1134                vq_err(vq, "Translation failure %d in indirect.\n", ret);
1135                return ret;
1136        }
1137
1138        /* We will use the result as an address to read from, so most
1139         * architectures only need a compiler barrier here. */
1140        read_barrier_depends();
1141
1142        count = indirect->len / sizeof desc;
1143        /* Buffers are chained via a 16 bit next field, so
1144         * we can have at most 2^16 of these. */
1145        if (unlikely(count > USHRT_MAX + 1)) {
1146                vq_err(vq, "Indirect buffer length too big: %d\n",
1147                       indirect->len);
1148                return -E2BIG;
1149        }
1150
1151        do {
1152                unsigned iov_count = *in_num + *out_num;
1153                if (unlikely(++found > count)) {
1154                        vq_err(vq, "Loop detected: last one at %u "
1155                               "indirect size %u\n",
1156                               i, count);
1157                        return -EINVAL;
1158                }
1159                if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
1160                                              vq->indirect, sizeof desc))) {
1161                        vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1162                               i, (size_t)indirect->addr + i * sizeof desc);
1163                        return -EINVAL;
1164                }
1165                if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1166                        vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1167                               i, (size_t)indirect->addr + i * sizeof desc);
1168                        return -EINVAL;
1169                }
1170
1171                ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1172                                     iov_size - iov_count);
1173                if (unlikely(ret < 0)) {
1174                        vq_err(vq, "Translation failure %d indirect idx %d\n",
1175                               ret, i);
1176                        return ret;
1177                }
1178                /* If this is an input descriptor, increment that count. */
1179                if (desc.flags & VRING_DESC_F_WRITE) {
1180                        *in_num += ret;
1181                        if (unlikely(log)) {
1182                                log[*log_num].addr = desc.addr;
1183                                log[*log_num].len = desc.len;
1184                                ++*log_num;
1185                        }
1186                } else {
1187                        /* If it's an output descriptor, they're all supposed
1188                         * to come before any input descriptors. */
1189                        if (unlikely(*in_num)) {
1190                                vq_err(vq, "Indirect descriptor "
1191                                       "has out after in: idx %d\n", i);
1192                                return -EINVAL;
1193                        }
1194                        *out_num += ret;
1195                }
1196        } while ((i = next_desc(&desc)) != -1);
1197        return 0;
1198}
1199
1200/* This looks in the virtqueue and for the first available buffer, and converts
1201 * it to an iovec for convenient access.  Since descriptors consist of some
1202 * number of output then some number of input descriptors, it's actually two
1203 * iovecs, but we pack them into one and note how many of each there were.
1204 *
1205 * This function returns the descriptor number found, or vq->num (which is
1206 * never a valid descriptor number) if none was found.  A negative code is
1207 * returned on error. */
1208int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1209                      struct iovec iov[], unsigned int iov_size,
1210                      unsigned int *out_num, unsigned int *in_num,
1211                      struct vhost_log *log, unsigned int *log_num)
1212{
1213        struct vring_desc desc;
1214        unsigned int i, head, found = 0;
1215        u16 last_avail_idx;
1216        int ret;
1217
1218        /* Check it isn't doing very strange things with descriptor numbers. */
1219        last_avail_idx = vq->last_avail_idx;
1220        if (unlikely(__get_user(vq->avail_idx, &vq->avail->idx))) {
1221                vq_err(vq, "Failed to access avail idx at %p\n",
1222                       &vq->avail->idx);
1223                return -EFAULT;
1224        }
1225
1226        if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1227                vq_err(vq, "Guest moved used index from %u to %u",
1228                       last_avail_idx, vq->avail_idx);
1229                return -EFAULT;
1230        }
1231
1232        /* If there's nothing new since last we looked, return invalid. */
1233        if (vq->avail_idx == last_avail_idx)
1234                return vq->num;
1235
1236        /* Only get avail ring entries after they have been exposed by guest. */
1237        smp_rmb();
1238
1239        /* Grab the next descriptor number they're advertising, and increment
1240         * the index we've seen. */
1241        if (unlikely(__get_user(head,
1242                                &vq->avail->ring[last_avail_idx % vq->num]))) {
1243                vq_err(vq, "Failed to read head: idx %d address %p\n",
1244                       last_avail_idx,
1245                       &vq->avail->ring[last_avail_idx % vq->num]);
1246                return -EFAULT;
1247        }
1248
1249        /* If their number is silly, that's an error. */
1250        if (unlikely(head >= vq->num)) {
1251                vq_err(vq, "Guest says index %u > %u is available",
1252                       head, vq->num);
1253                return -EINVAL;
1254        }
1255
1256        /* When we start there are none of either input nor output. */
1257        *out_num = *in_num = 0;
1258        if (unlikely(log))
1259                *log_num = 0;
1260
1261        i = head;
1262        do {
1263                unsigned iov_count = *in_num + *out_num;
1264                if (unlikely(i >= vq->num)) {
1265                        vq_err(vq, "Desc index is %u > %u, head = %u",
1266                               i, vq->num, head);
1267                        return -EINVAL;
1268                }
1269                if (unlikely(++found > vq->num)) {
1270                        vq_err(vq, "Loop detected: last one at %u "
1271                               "vq size %u head %u\n",
1272                               i, vq->num, head);
1273                        return -EINVAL;
1274                }
1275                ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
1276                if (unlikely(ret)) {
1277                        vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1278                               i, vq->desc + i);
1279                        return -EFAULT;
1280                }
1281                if (desc.flags & VRING_DESC_F_INDIRECT) {
1282                        ret = get_indirect(dev, vq, iov, iov_size,
1283                                           out_num, in_num,
1284                                           log, log_num, &desc);
1285                        if (unlikely(ret < 0)) {
1286                                vq_err(vq, "Failure detected "
1287                                       "in indirect descriptor at idx %d\n", i);
1288                                return ret;
1289                        }
1290                        continue;
1291                }
1292
1293                ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1294                                     iov_size - iov_count);
1295                if (unlikely(ret < 0)) {
1296                        vq_err(vq, "Translation failure %d descriptor idx %d\n",
1297                               ret, i);
1298                        return ret;
1299                }
1300                if (desc.flags & VRING_DESC_F_WRITE) {
1301                        /* If this is an input descriptor,
1302                         * increment that count. */
1303                        *in_num += ret;
1304                        if (unlikely(log)) {
1305                                log[*log_num].addr = desc.addr;
1306                                log[*log_num].len = desc.len;
1307                                ++*log_num;
1308                        }
1309                } else {
1310                        /* If it's an output descriptor, they're all supposed
1311                         * to come before any input descriptors. */
1312                        if (unlikely(*in_num)) {
1313                                vq_err(vq, "Descriptor has out after in: "
1314                                       "idx %d\n", i);
1315                                return -EINVAL;
1316                        }
1317                        *out_num += ret;
1318                }
1319        } while ((i = next_desc(&desc)) != -1);
1320
1321        /* On success, increment avail index. */
1322        vq->last_avail_idx++;
1323
1324        /* Assume notifications from guest are disabled at this point,
1325         * if they aren't we would need to update avail_event index. */
1326        BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
1327        return head;
1328}
1329
1330/* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1331void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1332{
1333        vq->last_avail_idx -= n;
1334}
1335
1336/* After we've used one of their buffers, we tell them about it.  We'll then
1337 * want to notify the guest, using eventfd. */
1338int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1339{
1340        struct vring_used_elem __user *used;
1341
1342        /* The virtqueue contains a ring of used buffers.  Get a pointer to the
1343         * next entry in that used ring. */
1344        used = &vq->used->ring[vq->last_used_idx % vq->num];
1345        if (__put_user(head, &used->id)) {
1346                vq_err(vq, "Failed to write used id");
1347                return -EFAULT;
1348        }
1349        if (__put_user(len, &used->len)) {
1350                vq_err(vq, "Failed to write used len");
1351                return -EFAULT;
1352        }
1353        /* Make sure buffer is written before we update index. */
1354        smp_wmb();
1355        if (__put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1356                vq_err(vq, "Failed to increment used idx");
1357                return -EFAULT;
1358        }
1359        if (unlikely(vq->log_used)) {
1360                /* Make sure data is seen before log. */
1361                smp_wmb();
1362                /* Log used ring entry write. */
1363                log_write(vq->log_base,
1364                          vq->log_addr +
1365                           ((void __user *)used - (void __user *)vq->used),
1366                          sizeof *used);
1367                /* Log used index update. */
1368                log_write(vq->log_base,
1369                          vq->log_addr + offsetof(struct vring_used, idx),
1370                          sizeof vq->used->idx);
1371                if (vq->log_ctx)
1372                        eventfd_signal(vq->log_ctx, 1);
1373        }
1374        vq->last_used_idx++;
1375        /* If the driver never bothers to signal in a very long while,
1376         * used index might wrap around. If that happens, invalidate
1377         * signalled_used index we stored. TODO: make sure driver
1378         * signals at least once in 2^16 and remove this. */
1379        if (unlikely(vq->last_used_idx == vq->signalled_used))
1380                vq->signalled_used_valid = false;
1381        return 0;
1382}
1383
1384static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1385                            struct vring_used_elem *heads,
1386                            unsigned count)
1387{
1388        struct vring_used_elem __user *used;
1389        u16 old, new;
1390        int start;
1391
1392        start = vq->last_used_idx % vq->num;
1393        used = vq->used->ring + start;
1394        if (__copy_to_user(used, heads, count * sizeof *used)) {
1395                vq_err(vq, "Failed to write used");
1396                return -EFAULT;
1397        }
1398        if (unlikely(vq->log_used)) {
1399                /* Make sure data is seen before log. */
1400                smp_wmb();
1401                /* Log used ring entry write. */
1402                log_write(vq->log_base,
1403                          vq->log_addr +
1404                           ((void __user *)used - (void __user *)vq->used),
1405                          count * sizeof *used);
1406        }
1407        old = vq->last_used_idx;
1408        new = (vq->last_used_idx += count);
1409        /* If the driver never bothers to signal in a very long while,
1410         * used index might wrap around. If that happens, invalidate
1411         * signalled_used index we stored. TODO: make sure driver
1412         * signals at least once in 2^16 and remove this. */
1413        if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
1414                vq->signalled_used_valid = false;
1415        return 0;
1416}
1417
1418/* After we've used one of their buffers, we tell them about it.  We'll then
1419 * want to notify the guest, using eventfd. */
1420int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1421                     unsigned count)
1422{
1423        int start, n, r;
1424
1425        start = vq->last_used_idx % vq->num;
1426        n = vq->num - start;
1427        if (n < count) {
1428                r = __vhost_add_used_n(vq, heads, n);
1429                if (r < 0)
1430                        return r;
1431                heads += n;
1432                count -= n;
1433        }
1434        r = __vhost_add_used_n(vq, heads, count);
1435
1436        /* Make sure buffer is written before we update index. */
1437        smp_wmb();
1438        if (put_user(vq->last_used_idx, &vq->used->idx)) {
1439                vq_err(vq, "Failed to increment used idx");
1440                return -EFAULT;
1441        }
1442        if (unlikely(vq->log_used)) {
1443                /* Log used index update. */
1444                log_write(vq->log_base,
1445                          vq->log_addr + offsetof(struct vring_used, idx),
1446                          sizeof vq->used->idx);
1447                if (vq->log_ctx)
1448                        eventfd_signal(vq->log_ctx, 1);
1449        }
1450        return r;
1451}
1452
1453static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1454{
1455        __u16 old, new, event;
1456        bool v;
1457        /* Flush out used index updates. This is paired
1458         * with the barrier that the Guest executes when enabling
1459         * interrupts. */
1460        smp_mb();
1461
1462        if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
1463            unlikely(vq->avail_idx == vq->last_avail_idx))
1464                return true;
1465
1466        if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1467                __u16 flags;
1468                if (__get_user(flags, &vq->avail->flags)) {
1469                        vq_err(vq, "Failed to get flags");
1470                        return true;
1471                }
1472                return !(flags & VRING_AVAIL_F_NO_INTERRUPT);
1473        }
1474        old = vq->signalled_used;
1475        v = vq->signalled_used_valid;
1476        new = vq->signalled_used = vq->last_used_idx;
1477        vq->signalled_used_valid = true;
1478
1479        if (unlikely(!v))
1480                return true;
1481
1482        if (get_user(event, vhost_used_event(vq))) {
1483                vq_err(vq, "Failed to get used event idx");
1484                return true;
1485        }
1486        return vring_need_event(event, new, old);
1487}
1488
1489/* This actually signals the guest, using eventfd. */
1490void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1491{
1492        /* Signal the Guest tell them we used something up. */
1493        if (vq->call_ctx && vhost_notify(dev, vq))
1494                eventfd_signal(vq->call_ctx, 1);
1495}
1496
1497/* And here's the combo meal deal.  Supersize me! */
1498void vhost_add_used_and_signal(struct vhost_dev *dev,
1499                               struct vhost_virtqueue *vq,
1500                               unsigned int head, int len)
1501{
1502        vhost_add_used(vq, head, len);
1503        vhost_signal(dev, vq);
1504}
1505
1506/* multi-buffer version of vhost_add_used_and_signal */
1507void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1508                                 struct vhost_virtqueue *vq,
1509                                 struct vring_used_elem *heads, unsigned count)
1510{
1511        vhost_add_used_n(vq, heads, count);
1512        vhost_signal(dev, vq);
1513}
1514
1515/* OK, now we need to know about added descriptors. */
1516bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1517{
1518        u16 avail_idx;
1519        int r;
1520
1521        if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1522                return false;
1523        vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1524        if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1525                r = vhost_update_used_flags(vq);
1526                if (r) {
1527                        vq_err(vq, "Failed to enable notification at %p: %d\n",
1528                               &vq->used->flags, r);
1529                        return false;
1530                }
1531        } else {
1532                r = vhost_update_avail_event(vq, vq->avail_idx);
1533                if (r) {
1534                        vq_err(vq, "Failed to update avail event index at %p: %d\n",
1535                               vhost_avail_event(vq), r);
1536                        return false;
1537                }
1538        }
1539        /* They could have slipped one in as we were doing that: make
1540         * sure it's written, then check again. */
1541        smp_mb();
1542        r = __get_user(avail_idx, &vq->avail->idx);
1543        if (r) {
1544                vq_err(vq, "Failed to check avail idx at %p: %d\n",
1545                       &vq->avail->idx, r);
1546                return false;
1547        }
1548
1549        return avail_idx != vq->avail_idx;
1550}
1551
1552/* We don't need to be notified again. */
1553void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1554{
1555        int r;
1556
1557        if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1558                return;
1559        vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1560        if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1561                r = vhost_update_used_flags(vq);
1562                if (r)
1563                        vq_err(vq, "Failed to enable notification at %p: %d\n",
1564                               &vq->used->flags, r);
1565        }
1566}
1567
1568static void vhost_zerocopy_done_signal(struct kref *kref)
1569{
1570        struct vhost_ubuf_ref *ubufs = container_of(kref, struct vhost_ubuf_ref,
1571                                                    kref);
1572        wake_up(&ubufs->wait);
1573}
1574
1575struct vhost_ubuf_ref *vhost_ubuf_alloc(struct vhost_virtqueue *vq,
1576                                        bool zcopy)
1577{
1578        struct vhost_ubuf_ref *ubufs;
1579        /* No zero copy backend? Nothing to count. */
1580        if (!zcopy)
1581                return NULL;
1582        ubufs = kmalloc(sizeof *ubufs, GFP_KERNEL);
1583        if (!ubufs)
1584                return ERR_PTR(-ENOMEM);
1585        kref_init(&ubufs->kref);
1586        init_waitqueue_head(&ubufs->wait);
1587        ubufs->vq = vq;
1588        return ubufs;
1589}
1590
1591void vhost_ubuf_put(struct vhost_ubuf_ref *ubufs)
1592{
1593        kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
1594}
1595
1596void vhost_ubuf_put_and_wait(struct vhost_ubuf_ref *ubufs)
1597{
1598        kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
1599        wait_event(ubufs->wait, !atomic_read(&ubufs->kref.refcount));
1600        kfree(ubufs);
1601}
1602
1603void vhost_zerocopy_callback(struct ubuf_info *ubuf)
1604{
1605        struct vhost_ubuf_ref *ubufs = ubuf->ctx;
1606        struct vhost_virtqueue *vq = ubufs->vq;
1607
1608        vhost_poll_queue(&vq->poll);
1609        /* set len = 1 to mark this desc buffers done DMA */
1610        vq->heads[ubuf->desc].len = VHOST_DMA_DONE_LEN;
1611        kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
1612}
1613
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