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