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/uio.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#include <linux/module.h>
  29
  30#include "vhost.h"
  31
  32enum {
  33        VHOST_MEMORY_MAX_NREGIONS = 64,
  34        VHOST_MEMORY_F_LOG = 0x1,
  35};
  36
  37#define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
  38#define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])
  39
  40static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
  41                            poll_table *pt)
  42{
  43        struct vhost_poll *poll;
  44
  45        poll = container_of(pt, struct vhost_poll, table);
  46        poll->wqh = wqh;
  47        add_wait_queue(wqh, &poll->wait);
  48}
  49
  50static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
  51                             void *key)
  52{
  53        struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
  54
  55        if (!((unsigned long)key & poll->mask))
  56                return 0;
  57
  58        vhost_poll_queue(poll);
  59        return 0;
  60}
  61
  62void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
  63{
  64        INIT_LIST_HEAD(&work->node);
  65        work->fn = fn;
  66        init_waitqueue_head(&work->done);
  67        work->flushing = 0;
  68        work->queue_seq = work->done_seq = 0;
  69}
  70EXPORT_SYMBOL_GPL(vhost_work_init);
  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}
  84EXPORT_SYMBOL_GPL(vhost_poll_init);
  85
  86/* Start polling a file. We add ourselves to file's wait queue. The caller must
  87 * keep a reference to a file until after vhost_poll_stop is called. */
  88int vhost_poll_start(struct vhost_poll *poll, struct file *file)
  89{
  90        unsigned long mask;
  91        int ret = 0;
  92
  93        if (poll->wqh)
  94                return 0;
  95
  96        mask = file->f_op->poll(file, &poll->table);
  97        if (mask)
  98                vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
  99        if (mask & POLLERR) {
 100                if (poll->wqh)
 101                        remove_wait_queue(poll->wqh, &poll->wait);
 102                ret = -EINVAL;
 103        }
 104
 105        return ret;
 106}
 107EXPORT_SYMBOL_GPL(vhost_poll_start);
 108
 109/* Stop polling a file. After this function returns, it becomes safe to drop the
 110 * file reference. You must also flush afterwards. */
 111void vhost_poll_stop(struct vhost_poll *poll)
 112{
 113        if (poll->wqh) {
 114                remove_wait_queue(poll->wqh, &poll->wait);
 115                poll->wqh = NULL;
 116        }
 117}
 118EXPORT_SYMBOL_GPL(vhost_poll_stop);
 119
 120static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
 121                                unsigned seq)
 122{
 123        int left;
 124
 125        spin_lock_irq(&dev->work_lock);
 126        left = seq - work->done_seq;
 127        spin_unlock_irq(&dev->work_lock);
 128        return left <= 0;
 129}
 130
 131void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
 132{
 133        unsigned seq;
 134        int flushing;
 135
 136        spin_lock_irq(&dev->work_lock);
 137        seq = work->queue_seq;
 138        work->flushing++;
 139        spin_unlock_irq(&dev->work_lock);
 140        wait_event(work->done, vhost_work_seq_done(dev, work, seq));
 141        spin_lock_irq(&dev->work_lock);
 142        flushing = --work->flushing;
 143        spin_unlock_irq(&dev->work_lock);
 144        BUG_ON(flushing < 0);
 145}
 146EXPORT_SYMBOL_GPL(vhost_work_flush);
 147
 148/* Flush any work that has been scheduled. When calling this, don't hold any
 149 * locks that are also used by the callback. */
 150void vhost_poll_flush(struct vhost_poll *poll)
 151{
 152        vhost_work_flush(poll->dev, &poll->work);
 153}
 154EXPORT_SYMBOL_GPL(vhost_poll_flush);
 155
 156void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 157{
 158        unsigned long flags;
 159
 160        spin_lock_irqsave(&dev->work_lock, flags);
 161        if (list_empty(&work->node)) {
 162                list_add_tail(&work->node, &dev->work_list);
 163                work->queue_seq++;
 164                spin_unlock_irqrestore(&dev->work_lock, flags);
 165                wake_up_process(dev->worker);
 166        } else {
 167                spin_unlock_irqrestore(&dev->work_lock, flags);
 168        }
 169}
 170EXPORT_SYMBOL_GPL(vhost_work_queue);
 171
 172void vhost_poll_queue(struct vhost_poll *poll)
 173{
 174        vhost_work_queue(poll->dev, &poll->work);
 175}
 176EXPORT_SYMBOL_GPL(vhost_poll_queue);
 177
 178static void vhost_vq_reset(struct vhost_dev *dev,
 179                           struct vhost_virtqueue *vq)
 180{
 181        vq->num = 1;
 182        vq->desc = NULL;
 183        vq->avail = NULL;
 184        vq->used = NULL;
 185        vq->last_avail_idx = 0;
 186        vq->avail_idx = 0;
 187        vq->last_used_idx = 0;
 188        vq->signalled_used = 0;
 189        vq->signalled_used_valid = false;
 190        vq->used_flags = 0;
 191        vq->log_used = false;
 192        vq->log_addr = -1ull;
 193        vq->private_data = NULL;
 194        vq->log_base = NULL;
 195        vq->error_ctx = NULL;
 196        vq->error = NULL;
 197        vq->kick = NULL;
 198        vq->call_ctx = NULL;
 199        vq->call = NULL;
 200        vq->log_ctx = NULL;
 201}
 202
 203static int vhost_worker(void *data)
 204{
 205        struct vhost_dev *dev = data;
 206        struct vhost_work *work = NULL;
 207        unsigned uninitialized_var(seq);
 208        mm_segment_t oldfs = get_fs();
 209
 210        set_fs(USER_DS);
 211        use_mm(dev->mm);
 212
 213        for (;;) {
 214                /* mb paired w/ kthread_stop */
 215                set_current_state(TASK_INTERRUPTIBLE);
 216
 217                spin_lock_irq(&dev->work_lock);
 218                if (work) {
 219                        work->done_seq = seq;
 220                        if (work->flushing)
 221                                wake_up_all(&work->done);
 222                }
 223
 224                if (kthread_should_stop()) {
 225                        spin_unlock_irq(&dev->work_lock);
 226                        __set_current_state(TASK_RUNNING);
 227                        break;
 228                }
 229                if (!list_empty(&dev->work_list)) {
 230                        work = list_first_entry(&dev->work_list,
 231                                                struct vhost_work, node);
 232                        list_del_init(&work->node);
 233                        seq = work->queue_seq;
 234                } else
 235                        work = NULL;
 236                spin_unlock_irq(&dev->work_lock);
 237
 238                if (work) {
 239                        __set_current_state(TASK_RUNNING);
 240                        work->fn(work);
 241                        if (need_resched())
 242                                schedule();
 243                } else
 244                        schedule();
 245
 246        }
 247        unuse_mm(dev->mm);
 248        set_fs(oldfs);
 249        return 0;
 250}
 251
 252static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
 253{
 254        kfree(vq->indirect);
 255        vq->indirect = NULL;
 256        kfree(vq->log);
 257        vq->log = NULL;
 258        kfree(vq->heads);
 259        vq->heads = NULL;
 260}
 261
 262/* Helper to allocate iovec buffers for all vqs. */
 263static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
 264{
 265        struct vhost_virtqueue *vq;
 266        int i;
 267
 268        for (i = 0; i < dev->nvqs; ++i) {
 269                vq = dev->vqs[i];
 270                vq->indirect = kmalloc(sizeof *vq->indirect * UIO_MAXIOV,
 271                                       GFP_KERNEL);
 272                vq->log = kmalloc(sizeof *vq->log * UIO_MAXIOV, GFP_KERNEL);
 273                vq->heads = kmalloc(sizeof *vq->heads * UIO_MAXIOV, GFP_KERNEL);
 274                if (!vq->indirect || !vq->log || !vq->heads)
 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        struct vhost_virtqueue *vq;
 297        int i;
 298
 299        dev->vqs = vqs;
 300        dev->nvqs = nvqs;
 301        mutex_init(&dev->mutex);
 302        dev->log_ctx = NULL;
 303        dev->log_file = NULL;
 304        dev->memory = NULL;
 305        dev->mm = NULL;
 306        spin_lock_init(&dev->work_lock);
 307        INIT_LIST_HEAD(&dev->work_list);
 308        dev->worker = NULL;
 309
 310        for (i = 0; i < dev->nvqs; ++i) {
 311                vq = dev->vqs[i];
 312                vq->log = NULL;
 313                vq->indirect = NULL;
 314                vq->heads = NULL;
 315                vq->dev = dev;
 316                mutex_init(&vq->mutex);
 317                vhost_vq_reset(dev, vq);
 318                if (vq->handle_kick)
 319                        vhost_poll_init(&vq->poll, vq->handle_kick,
 320                                        POLLIN, dev);
 321        }
 322
 323        return 0;
 324}
 325EXPORT_SYMBOL_GPL(vhost_dev_init);
 326
 327/* Caller should have device mutex */
 328long vhost_dev_check_owner(struct vhost_dev *dev)
 329{
 330        /* Are you the owner? If not, I don't think you mean to do that */
 331        return dev->mm == current->mm ? 0 : -EPERM;
 332}
 333EXPORT_SYMBOL_GPL(vhost_dev_check_owner);
 334
 335struct vhost_attach_cgroups_struct {
 336        struct vhost_work work;
 337        struct task_struct *owner;
 338        int ret;
 339};
 340
 341static void vhost_attach_cgroups_work(struct vhost_work *work)
 342{
 343        struct vhost_attach_cgroups_struct *s;
 344
 345        s = container_of(work, struct vhost_attach_cgroups_struct, work);
 346        s->ret = cgroup_attach_task_all(s->owner, current);
 347}
 348
 349static int vhost_attach_cgroups(struct vhost_dev *dev)
 350{
 351        struct vhost_attach_cgroups_struct attach;
 352
 353        attach.owner = current;
 354        vhost_work_init(&attach.work, vhost_attach_cgroups_work);
 355        vhost_work_queue(dev, &attach.work);
 356        vhost_work_flush(dev, &attach.work);
 357        return attach.ret;
 358}
 359
 360/* Caller should have device mutex */
 361bool vhost_dev_has_owner(struct vhost_dev *dev)
 362{
 363        return dev->mm;
 364}
 365EXPORT_SYMBOL_GPL(vhost_dev_has_owner);
 366
 367/* Caller should have device mutex */
 368long vhost_dev_set_owner(struct vhost_dev *dev)
 369{
 370        struct task_struct *worker;
 371        int err;
 372
 373        /* Is there an owner already? */
 374        if (vhost_dev_has_owner(dev)) {
 375                err = -EBUSY;
 376                goto err_mm;
 377        }
 378
 379        /* No owner, become one */
 380        dev->mm = get_task_mm(current);
 381        worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
 382        if (IS_ERR(worker)) {
 383                err = PTR_ERR(worker);
 384                goto err_worker;
 385        }
 386
 387        dev->worker = worker;
 388        wake_up_process(worker);        /* avoid contributing to loadavg */
 389
 390        err = vhost_attach_cgroups(dev);
 391        if (err)
 392                goto err_cgroup;
 393
 394        err = vhost_dev_alloc_iovecs(dev);
 395        if (err)
 396                goto err_cgroup;
 397
 398        return 0;
 399err_cgroup:
 400        kthread_stop(worker);
 401        dev->worker = NULL;
 402err_worker:
 403        if (dev->mm)
 404                mmput(dev->mm);
 405        dev->mm = NULL;
 406err_mm:
 407        return err;
 408}
 409EXPORT_SYMBOL_GPL(vhost_dev_set_owner);
 410
 411struct vhost_memory *vhost_dev_reset_owner_prepare(void)
 412{
 413        return kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
 414}
 415EXPORT_SYMBOL_GPL(vhost_dev_reset_owner_prepare);
 416
 417/* Caller should have device mutex */
 418void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_memory *memory)
 419{
 420        vhost_dev_cleanup(dev, true);
 421
 422        /* Restore memory to default empty mapping. */
 423        memory->nregions = 0;
 424        RCU_INIT_POINTER(dev->memory, memory);
 425}
 426EXPORT_SYMBOL_GPL(vhost_dev_reset_owner);
 427
 428void vhost_dev_stop(struct vhost_dev *dev)
 429{
 430        int i;
 431
 432        for (i = 0; i < dev->nvqs; ++i) {
 433                if (dev->vqs[i]->kick && dev->vqs[i]->handle_kick) {
 434                        vhost_poll_stop(&dev->vqs[i]->poll);
 435                        vhost_poll_flush(&dev->vqs[i]->poll);
 436                }
 437        }
 438}
 439EXPORT_SYMBOL_GPL(vhost_dev_stop);
 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]->error_ctx)
 448                        eventfd_ctx_put(dev->vqs[i]->error_ctx);
 449                if (dev->vqs[i]->error)
 450                        fput(dev->vqs[i]->error);
 451                if (dev->vqs[i]->kick)
 452                        fput(dev->vqs[i]->kick);
 453                if (dev->vqs[i]->call_ctx)
 454                        eventfd_ctx_put(dev->vqs[i]->call_ctx);
 455                if (dev->vqs[i]->call)
 456                        fput(dev->vqs[i]->call);
 457                vhost_vq_reset(dev, dev->vqs[i]);
 458        }
 459        vhost_dev_free_iovecs(dev);
 460        if (dev->log_ctx)
 461                eventfd_ctx_put(dev->log_ctx);
 462        dev->log_ctx = NULL;
 463        if (dev->log_file)
 464                fput(dev->log_file);
 465        dev->log_file = NULL;
 466        /* No one will access memory at this point */
 467        kfree(rcu_dereference_protected(dev->memory,
 468                                        locked ==
 469                                                lockdep_is_held(&dev->mutex)));
 470        RCU_INIT_POINTER(dev->memory, NULL);
 471        WARN_ON(!list_empty(&dev->work_list));
 472        if (dev->worker) {
 473                kthread_stop(dev->worker);
 474                dev->worker = NULL;
 475        }
 476        if (dev->mm)
 477                mmput(dev->mm);
 478        dev->mm = NULL;
 479}
 480EXPORT_SYMBOL_GPL(vhost_dev_cleanup);
 481
 482static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 483{
 484        u64 a = addr / VHOST_PAGE_SIZE / 8;
 485
 486        /* Make sure 64 bit math will not overflow. */
 487        if (a > ULONG_MAX - (unsigned long)log_base ||
 488            a + (unsigned long)log_base > ULONG_MAX)
 489                return 0;
 490
 491        return access_ok(VERIFY_WRITE, log_base + a,
 492                         (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
 493}
 494
 495/* Caller should have vq mutex and device mutex. */
 496static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
 497                               int log_all)
 498{
 499        int i;
 500
 501        if (!mem)
 502                return 0;
 503
 504        for (i = 0; i < mem->nregions; ++i) {
 505                struct vhost_memory_region *m = mem->regions + i;
 506                unsigned long a = m->userspace_addr;
 507                if (m->memory_size > ULONG_MAX)
 508                        return 0;
 509                else if (!access_ok(VERIFY_WRITE, (void __user *)a,
 510                                    m->memory_size))
 511                        return 0;
 512                else if (log_all && !log_access_ok(log_base,
 513                                                   m->guest_phys_addr,
 514                                                   m->memory_size))
 515                        return 0;
 516        }
 517        return 1;
 518}
 519
 520/* Can we switch to this memory table? */
 521/* Caller should have device mutex but not vq mutex */
 522static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
 523                            int log_all)
 524{
 525        int i;
 526
 527        for (i = 0; i < d->nvqs; ++i) {
 528                int ok;
 529                mutex_lock(&d->vqs[i]->mutex);
 530                /* If ring is inactive, will check when it's enabled. */
 531                if (d->vqs[i]->private_data)
 532                        ok = vq_memory_access_ok(d->vqs[i]->log_base, mem,
 533                                                 log_all);
 534                else
 535                        ok = 1;
 536                mutex_unlock(&d->vqs[i]->mutex);
 537                if (!ok)
 538                        return 0;
 539        }
 540        return 1;
 541}
 542
 543static int vq_access_ok(struct vhost_dev *d, unsigned int num,
 544                        struct vring_desc __user *desc,
 545                        struct vring_avail __user *avail,
 546                        struct vring_used __user *used)
 547{
 548        size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 549        return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
 550               access_ok(VERIFY_READ, avail,
 551                         sizeof *avail + num * sizeof *avail->ring + s) &&
 552               access_ok(VERIFY_WRITE, used,
 553                        sizeof *used + num * sizeof *used->ring + s);
 554}
 555
 556/* Can we log writes? */
 557/* Caller should have device mutex but not vq mutex */
 558int vhost_log_access_ok(struct vhost_dev *dev)
 559{
 560        struct vhost_memory *mp;
 561
 562        mp = rcu_dereference_protected(dev->memory,
 563                                       lockdep_is_held(&dev->mutex));
 564        return memory_access_ok(dev, mp, 1);
 565}
 566EXPORT_SYMBOL_GPL(vhost_log_access_ok);
 567
 568/* Verify access for write logging. */
 569/* Caller should have vq mutex and device mutex */
 570static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue *vq,
 571                            void __user *log_base)
 572{
 573        struct vhost_memory *mp;
 574        size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 575
 576        mp = rcu_dereference_protected(vq->dev->memory,
 577                                       lockdep_is_held(&vq->mutex));
 578        return vq_memory_access_ok(log_base, mp,
 579                            vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
 580                (!vq->log_used || log_access_ok(log_base, vq->log_addr,
 581                                        sizeof *vq->used +
 582                                        vq->num * sizeof *vq->used->ring + s));
 583}
 584
 585/* Can we start vq? */
 586/* Caller should have vq mutex and device mutex */
 587int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 588{
 589        return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail, vq->used) &&
 590                vq_log_access_ok(vq->dev, vq, vq->log_base);
 591}
 592EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
 593
 594static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 595{
 596        struct vhost_memory mem, *newmem, *oldmem;
 597        unsigned long size = offsetof(struct vhost_memory, regions);
 598
 599        if (copy_from_user(&mem, m, size))
 600                return -EFAULT;
 601        if (mem.padding)
 602                return -EOPNOTSUPP;
 603        if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
 604                return -E2BIG;
 605        newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
 606        if (!newmem)
 607                return -ENOMEM;
 608
 609        memcpy(newmem, &mem, size);
 610        if (copy_from_user(newmem->regions, m->regions,
 611                           mem.nregions * sizeof *m->regions)) {
 612                kfree(newmem);
 613                return -EFAULT;
 614        }
 615
 616        if (!memory_access_ok(d, newmem,
 617                              vhost_has_feature(d, VHOST_F_LOG_ALL))) {
 618                kfree(newmem);
 619                return -EFAULT;
 620        }
 621        oldmem = rcu_dereference_protected(d->memory,
 622                                           lockdep_is_held(&d->mutex));
 623        rcu_assign_pointer(d->memory, newmem);
 624        synchronize_rcu();
 625        kfree(oldmem);
 626        return 0;
 627}
 628
 629long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
 630{
 631        struct file *eventfp, *filep = NULL;
 632        bool pollstart = false, pollstop = false;
 633        struct eventfd_ctx *ctx = NULL;
 634        u32 __user *idxp = argp;
 635        struct vhost_virtqueue *vq;
 636        struct vhost_vring_state s;
 637        struct vhost_vring_file f;
 638        struct vhost_vring_addr a;
 639        u32 idx;
 640        long r;
 641
 642        r = get_user(idx, idxp);
 643        if (r < 0)
 644                return r;
 645        if (idx >= d->nvqs)
 646                return -ENOBUFS;
 647
 648        vq = d->vqs[idx];
 649
 650        mutex_lock(&vq->mutex);
 651
 652        switch (ioctl) {
 653        case VHOST_SET_VRING_NUM:
 654                /* Resizing ring with an active backend?
 655                 * You don't want to do that. */
 656                if (vq->private_data) {
 657                        r = -EBUSY;
 658                        break;
 659                }
 660                if (copy_from_user(&s, argp, sizeof s)) {
 661                        r = -EFAULT;
 662                        break;
 663                }
 664                if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
 665                        r = -EINVAL;
 666                        break;
 667                }
 668                vq->num = s.num;
 669                break;
 670        case VHOST_SET_VRING_BASE:
 671                /* Moving base with an active backend?
 672                 * You don't want to do that. */
 673                if (vq->private_data) {
 674                        r = -EBUSY;
 675                        break;
 676                }
 677                if (copy_from_user(&s, argp, sizeof s)) {
 678                        r = -EFAULT;
 679                        break;
 680                }
 681                if (s.num > 0xffff) {
 682                        r = -EINVAL;
 683                        break;
 684                }
 685                vq->last_avail_idx = s.num;
 686                /* Forget the cached index value. */
 687                vq->avail_idx = vq->last_avail_idx;
 688                break;
 689        case VHOST_GET_VRING_BASE:
 690                s.index = idx;
 691                s.num = vq->last_avail_idx;
 692                if (copy_to_user(argp, &s, sizeof s))
 693                        r = -EFAULT;
 694                break;
 695        case VHOST_SET_VRING_ADDR:
 696                if (copy_from_user(&a, argp, sizeof a)) {
 697                        r = -EFAULT;
 698                        break;
 699                }
 700                if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
 701                        r = -EOPNOTSUPP;
 702                        break;
 703                }
 704                /* For 32bit, verify that the top 32bits of the user
 705                   data are set to zero. */
 706                if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
 707                    (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
 708                    (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
 709                        r = -EFAULT;
 710                        break;
 711                }
 712                if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
 713                    (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
 714                    (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
 715                        r = -EINVAL;
 716                        break;
 717                }
 718
 719                /* We only verify access here if backend is configured.
 720                 * If it is not, we don't as size might not have been setup.
 721                 * We will verify when backend is configured. */
 722                if (vq->private_data) {
 723                        if (!vq_access_ok(d, vq->num,
 724                                (void __user *)(unsigned long)a.desc_user_addr,
 725                                (void __user *)(unsigned long)a.avail_user_addr,
 726                                (void __user *)(unsigned long)a.used_user_addr)) {
 727                                r = -EINVAL;
 728                                break;
 729                        }
 730
 731                        /* Also validate log access for used ring if enabled. */
 732                        if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
 733                            !log_access_ok(vq->log_base, a.log_guest_addr,
 734                                           sizeof *vq->used +
 735                                           vq->num * sizeof *vq->used->ring)) {
 736                                r = -EINVAL;
 737                                break;
 738                        }
 739                }
 740
 741                vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
 742                vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
 743                vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
 744                vq->log_addr = a.log_guest_addr;
 745                vq->used = (void __user *)(unsigned long)a.used_user_addr;
 746                break;
 747        case VHOST_SET_VRING_KICK:
 748                if (copy_from_user(&f, argp, sizeof f)) {
 749                        r = -EFAULT;
 750                        break;
 751                }
 752                eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 753                if (IS_ERR(eventfp)) {
 754                        r = PTR_ERR(eventfp);
 755                        break;
 756                }
 757                if (eventfp != vq->kick) {
 758                        pollstop = (filep = vq->kick) != NULL;
 759                        pollstart = (vq->kick = eventfp) != NULL;
 760                } else
 761                        filep = eventfp;
 762                break;
 763        case VHOST_SET_VRING_CALL:
 764                if (copy_from_user(&f, argp, sizeof f)) {
 765                        r = -EFAULT;
 766                        break;
 767                }
 768                eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 769                if (IS_ERR(eventfp)) {
 770                        r = PTR_ERR(eventfp);
 771                        break;
 772                }
 773                if (eventfp != vq->call) {
 774                        filep = vq->call;
 775                        ctx = vq->call_ctx;
 776                        vq->call = eventfp;
 777                        vq->call_ctx = eventfp ?
 778                                eventfd_ctx_fileget(eventfp) : NULL;
 779                } else
 780                        filep = eventfp;
 781                break;
 782        case VHOST_SET_VRING_ERR:
 783                if (copy_from_user(&f, argp, sizeof f)) {
 784                        r = -EFAULT;
 785                        break;
 786                }
 787                eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 788                if (IS_ERR(eventfp)) {
 789                        r = PTR_ERR(eventfp);
 790                        break;
 791                }
 792                if (eventfp != vq->error) {
 793                        filep = vq->error;
 794                        vq->error = eventfp;
 795                        ctx = vq->error_ctx;
 796                        vq->error_ctx = eventfp ?
 797                                eventfd_ctx_fileget(eventfp) : NULL;
 798                } else
 799                        filep = eventfp;
 800                break;
 801        default:
 802                r = -ENOIOCTLCMD;
 803        }
 804
 805        if (pollstop && vq->handle_kick)
 806                vhost_poll_stop(&vq->poll);
 807
 808        if (ctx)
 809                eventfd_ctx_put(ctx);
 810        if (filep)
 811                fput(filep);
 812
 813        if (pollstart && vq->handle_kick)
 814                r = vhost_poll_start(&vq->poll, vq->kick);
 815
 816        mutex_unlock(&vq->mutex);
 817
 818        if (pollstop && vq->handle_kick)
 819                vhost_poll_flush(&vq->poll);
 820        return r;
 821}
 822EXPORT_SYMBOL_GPL(vhost_vring_ioctl);
 823
 824/* Caller must have device mutex */
 825long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
 826{
 827        struct file *eventfp, *filep = NULL;
 828        struct eventfd_ctx *ctx = NULL;
 829        u64 p;
 830        long r;
 831        int i, fd;
 832
 833        /* If you are not the owner, you can become one */
 834        if (ioctl == VHOST_SET_OWNER) {
 835                r = vhost_dev_set_owner(d);
 836                goto done;
 837        }
 838
 839        /* You must be the owner to do anything else */
 840        r = vhost_dev_check_owner(d);
 841        if (r)
 842                goto done;
 843
 844        switch (ioctl) {
 845        case VHOST_SET_MEM_TABLE:
 846                r = vhost_set_memory(d, argp);
 847                break;
 848        case VHOST_SET_LOG_BASE:
 849                if (copy_from_user(&p, argp, sizeof p)) {
 850                        r = -EFAULT;
 851                        break;
 852                }
 853                if ((u64)(unsigned long)p != p) {
 854                        r = -EFAULT;
 855                        break;
 856                }
 857                for (i = 0; i < d->nvqs; ++i) {
 858                        struct vhost_virtqueue *vq;
 859                        void __user *base = (void __user *)(unsigned long)p;
 860                        vq = d->vqs[i];
 861                        mutex_lock(&vq->mutex);
 862                        /* If ring is inactive, will check when it's enabled. */
 863                        if (vq->private_data && !vq_log_access_ok(d, vq, base))
 864                                r = -EFAULT;
 865                        else
 866                                vq->log_base = base;
 867                        mutex_unlock(&vq->mutex);
 868                }
 869                break;
 870        case VHOST_SET_LOG_FD:
 871                r = get_user(fd, (int __user *)argp);
 872                if (r < 0)
 873                        break;
 874                eventfp = fd == -1 ? NULL : eventfd_fget(fd);
 875                if (IS_ERR(eventfp)) {
 876                        r = PTR_ERR(eventfp);
 877                        break;
 878                }
 879                if (eventfp != d->log_file) {
 880                        filep = d->log_file;
 881                        ctx = d->log_ctx;
 882                        d->log_ctx = eventfp ?
 883                                eventfd_ctx_fileget(eventfp) : NULL;
 884                } else
 885                        filep = eventfp;
 886                for (i = 0; i < d->nvqs; ++i) {
 887                        mutex_lock(&d->vqs[i]->mutex);
 888                        d->vqs[i]->log_ctx = d->log_ctx;
 889                        mutex_unlock(&d->vqs[i]->mutex);
 890                }
 891                if (ctx)
 892                        eventfd_ctx_put(ctx);
 893                if (filep)
 894                        fput(filep);
 895                break;
 896        default:
 897                r = -ENOIOCTLCMD;
 898                break;
 899        }
 900done:
 901        return r;
 902}
 903EXPORT_SYMBOL_GPL(vhost_dev_ioctl);
 904
 905static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
 906                                                     __u64 addr, __u32 len)
 907{
 908        struct vhost_memory_region *reg;
 909        int i;
 910
 911        /* linear search is not brilliant, but we really have on the order of 6
 912         * regions in practice */
 913        for (i = 0; i < mem->nregions; ++i) {
 914                reg = mem->regions + i;
 915                if (reg->guest_phys_addr <= addr &&
 916                    reg->guest_phys_addr + reg->memory_size - 1 >= addr)
 917                        return reg;
 918        }
 919        return NULL;
 920}
 921
 922/* TODO: This is really inefficient.  We need something like get_user()
 923 * (instruction directly accesses the data, with an exception table entry
 924 * returning -EFAULT). See Documentation/x86/exception-tables.txt.
 925 */
 926static int set_bit_to_user(int nr, void __user *addr)
 927{
 928        unsigned long log = (unsigned long)addr;
 929        struct page *page;
 930        void *base;
 931        int bit = nr + (log % PAGE_SIZE) * 8;
 932        int r;
 933
 934        r = get_user_pages_fast(log, 1, 1, &page);
 935        if (r < 0)
 936                return r;
 937        BUG_ON(r != 1);
 938        base = kmap_atomic(page);
 939        set_bit(bit, base);
 940        kunmap_atomic(base);
 941        set_page_dirty_lock(page);
 942        put_page(page);
 943        return 0;
 944}
 945
 946static int log_write(void __user *log_base,
 947                     u64 write_address, u64 write_length)
 948{
 949        u64 write_page = write_address / VHOST_PAGE_SIZE;
 950        int r;
 951
 952        if (!write_length)
 953                return 0;
 954        write_length += write_address % VHOST_PAGE_SIZE;
 955        for (;;) {
 956                u64 base = (u64)(unsigned long)log_base;
 957                u64 log = base + write_page / 8;
 958                int bit = write_page % 8;
 959                if ((u64)(unsigned long)log != log)
 960                        return -EFAULT;
 961                r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
 962                if (r < 0)
 963                        return r;
 964                if (write_length <= VHOST_PAGE_SIZE)
 965                        break;
 966                write_length -= VHOST_PAGE_SIZE;
 967                write_page += 1;
 968        }
 969        return r;
 970}
 971
 972int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
 973                    unsigned int log_num, u64 len)
 974{
 975        int i, r;
 976
 977        /* Make sure data written is seen before log. */
 978        smp_wmb();
 979        for (i = 0; i < log_num; ++i) {
 980                u64 l = min(log[i].len, len);
 981                r = log_write(vq->log_base, log[i].addr, l);
 982                if (r < 0)
 983                        return r;
 984                len -= l;
 985                if (!len) {
 986                        if (vq->log_ctx)
 987                                eventfd_signal(vq->log_ctx, 1);
 988                        return 0;
 989                }
 990        }
 991        /* Length written exceeds what we have stored. This is a bug. */
 992        BUG();
 993        return 0;
 994}
 995EXPORT_SYMBOL_GPL(vhost_log_write);
 996
 997static int vhost_update_used_flags(struct vhost_virtqueue *vq)
 998{
 999        void __user *used;
1000        if (__put_user(vq->used_flags, &vq->used->flags) < 0)
1001                return -EFAULT;
1002        if (unlikely(vq->log_used)) {
1003                /* Make sure the flag is seen before log. */
1004                smp_wmb();
1005                /* Log used flag write. */
1006                used = &vq->used->flags;
1007                log_write(vq->log_base, vq->log_addr +
1008                          (used - (void __user *)vq->used),
1009                          sizeof vq->used->flags);
1010                if (vq->log_ctx)
1011                        eventfd_signal(vq->log_ctx, 1);
1012        }
1013        return 0;
1014}
1015
1016static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
1017{
1018        if (__put_user(vq->avail_idx, vhost_avail_event(vq)))
1019                return -EFAULT;
1020        if (unlikely(vq->log_used)) {
1021                void __user *used;
1022                /* Make sure the event is seen before log. */
1023                smp_wmb();
1024                /* Log avail event write */
1025                used = vhost_avail_event(vq);
1026                log_write(vq->log_base, vq->log_addr +
1027                          (used - (void __user *)vq->used),
1028                          sizeof *vhost_avail_event(vq));
1029                if (vq->log_ctx)
1030                        eventfd_signal(vq->log_ctx, 1);
1031        }
1032        return 0;
1033}
1034
1035int vhost_init_used(struct vhost_virtqueue *vq)
1036{
1037        int r;
1038        if (!vq->private_data)
1039                return 0;
1040
1041        r = vhost_update_used_flags(vq);
1042        if (r)
1043                return r;
1044        vq->signalled_used_valid = false;
1045        return get_user(vq->last_used_idx, &vq->used->idx);
1046}
1047EXPORT_SYMBOL_GPL(vhost_init_used);
1048
1049static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
1050                          struct iovec iov[], int iov_size)
1051{
1052        const struct vhost_memory_region *reg;
1053        struct vhost_memory *mem;
1054        struct iovec *_iov;
1055        u64 s = 0;
1056        int ret = 0;
1057
1058        rcu_read_lock();
1059
1060        mem = rcu_dereference(dev->memory);
1061        while ((u64)len > s) {
1062                u64 size;
1063                if (unlikely(ret >= iov_size)) {
1064                        ret = -ENOBUFS;
1065                        break;
1066                }
1067                reg = find_region(mem, addr, len);
1068                if (unlikely(!reg)) {
1069                        ret = -EFAULT;
1070                        break;
1071                }
1072                _iov = iov + ret;
1073                size = reg->memory_size - addr + reg->guest_phys_addr;
1074                _iov->iov_len = min((u64)len - s, size);
1075                _iov->iov_base = (void __user *)(unsigned long)
1076                        (reg->userspace_addr + addr - reg->guest_phys_addr);
1077                s += size;
1078                addr += size;
1079                ++ret;
1080        }
1081
1082        rcu_read_unlock();
1083        return ret;
1084}
1085
1086/* Each buffer in the virtqueues is actually a chain of descriptors.  This
1087 * function returns the next descriptor in the chain,
1088 * or -1U if we're at the end. */
1089static unsigned next_desc(struct vring_desc *desc)
1090{
1091        unsigned int next;
1092
1093        /* If this descriptor says it doesn't chain, we're done. */
1094        if (!(desc->flags & VRING_DESC_F_NEXT))
1095                return -1U;
1096
1097        /* Check they're not leading us off end of descriptors. */
1098        next = desc->next;
1099        /* Make sure compiler knows to grab that: we don't want it changing! */
1100        /* We will use the result as an index in an array, so most
1101         * architectures only need a compiler barrier here. */
1102        read_barrier_depends();
1103
1104        return next;
1105}
1106
1107static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1108                        struct iovec iov[], unsigned int iov_size,
1109                        unsigned int *out_num, unsigned int *in_num,
1110                        struct vhost_log *log, unsigned int *log_num,
1111                        struct vring_desc *indirect)
1112{
1113        struct vring_desc desc;
1114        unsigned int i = 0, count, found = 0;
1115        int ret;
1116
1117        /* Sanity check */
1118        if (unlikely(indirect->len % sizeof desc)) {
1119                vq_err(vq, "Invalid length in indirect descriptor: "
1120                       "len 0x%llx not multiple of 0x%zx\n",
1121                       (unsigned long long)indirect->len,
1122                       sizeof desc);
1123                return -EINVAL;
1124        }
1125
1126        ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
1127                             UIO_MAXIOV);
1128        if (unlikely(ret < 0)) {
1129                vq_err(vq, "Translation failure %d in indirect.\n", ret);
1130                return ret;
1131        }
1132
1133        /* We will use the result as an address to read from, so most
1134         * architectures only need a compiler barrier here. */
1135        read_barrier_depends();
1136
1137        count = indirect->len / sizeof desc;
1138        /* Buffers are chained via a 16 bit next field, so
1139         * we can have at most 2^16 of these. */
1140        if (unlikely(count > USHRT_MAX + 1)) {
1141                vq_err(vq, "Indirect buffer length too big: %d\n",
1142                       indirect->len);
1143                return -E2BIG;
1144        }
1145
1146        do {
1147                unsigned iov_count = *in_num + *out_num;
1148                if (unlikely(++found > count)) {
1149                        vq_err(vq, "Loop detected: last one at %u "
1150                               "indirect size %u\n",
1151                               i, count);
1152                        return -EINVAL;
1153                }
1154                if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
1155                                              vq->indirect, sizeof desc))) {
1156                        vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1157                               i, (size_t)indirect->addr + i * sizeof desc);
1158                        return -EINVAL;
1159                }
1160                if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1161                        vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1162                               i, (size_t)indirect->addr + i * sizeof desc);
1163                        return -EINVAL;
1164                }
1165
1166                ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1167                                     iov_size - iov_count);
1168                if (unlikely(ret < 0)) {
1169                        vq_err(vq, "Translation failure %d indirect idx %d\n",
1170                               ret, i);
1171                        return ret;
1172                }
1173                /* If this is an input descriptor, increment that count. */
1174                if (desc.flags & VRING_DESC_F_WRITE) {
1175                        *in_num += ret;
1176                        if (unlikely(log)) {
1177                                log[*log_num].addr = desc.addr;
1178                                log[*log_num].len = desc.len;
1179                                ++*log_num;
1180                        }
1181                } else {
1182                        /* If it's an output descriptor, they're all supposed
1183                         * to come before any input descriptors. */
1184                        if (unlikely(*in_num)) {
1185                                vq_err(vq, "Indirect descriptor "
1186                                       "has out after in: idx %d\n", i);
1187                                return -EINVAL;
1188                        }
1189                        *out_num += ret;
1190                }
1191        } while ((i = next_desc(&desc)) != -1);
1192        return 0;
1193}
1194
1195/* This looks in the virtqueue and for the first available buffer, and converts
1196 * it to an iovec for convenient access.  Since descriptors consist of some
1197 * number of output then some number of input descriptors, it's actually two
1198 * iovecs, but we pack them into one and note how many of each there were.
1199 *
1200 * This function returns the descriptor number found, or vq->num (which is
1201 * never a valid descriptor number) if none was found.  A negative code is
1202 * returned on error. */
1203int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1204                      struct iovec iov[], unsigned int iov_size,
1205                      unsigned int *out_num, unsigned int *in_num,
1206                      struct vhost_log *log, unsigned int *log_num)
1207{
1208        struct vring_desc desc;
1209        unsigned int i, head, found = 0;
1210        u16 last_avail_idx;
1211        int ret;
1212
1213        /* Check it isn't doing very strange things with descriptor numbers. */
1214        last_avail_idx = vq->last_avail_idx;
1215        if (unlikely(__get_user(vq->avail_idx, &vq->avail->idx))) {
1216                vq_err(vq, "Failed to access avail idx at %p\n",
1217                       &vq->avail->idx);
1218                return -EFAULT;
1219        }
1220
1221        if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1222                vq_err(vq, "Guest moved used index from %u to %u",
1223                       last_avail_idx, vq->avail_idx);
1224                return -EFAULT;
1225        }
1226
1227        /* If there's nothing new since last we looked, return invalid. */
1228        if (vq->avail_idx == last_avail_idx)
1229                return vq->num;
1230
1231        /* Only get avail ring entries after they have been exposed by guest. */
1232        smp_rmb();
1233
1234        /* Grab the next descriptor number they're advertising, and increment
1235         * the index we've seen. */
1236        if (unlikely(__get_user(head,
1237                                &vq->avail->ring[last_avail_idx % vq->num]))) {
1238                vq_err(vq, "Failed to read head: idx %d address %p\n",
1239                       last_avail_idx,
1240                       &vq->avail->ring[last_avail_idx % vq->num]);
1241                return -EFAULT;
1242        }
1243
1244        /* If their number is silly, that's an error. */
1245        if (unlikely(head >= vq->num)) {
1246                vq_err(vq, "Guest says index %u > %u is available",
1247                       head, vq->num);
1248                return -EINVAL;
1249        }
1250
1251        /* When we start there are none of either input nor output. */
1252        *out_num = *in_num = 0;
1253        if (unlikely(log))
1254                *log_num = 0;
1255
1256        i = head;
1257        do {
1258                unsigned iov_count = *in_num + *out_num;
1259                if (unlikely(i >= vq->num)) {
1260                        vq_err(vq, "Desc index is %u > %u, head = %u",
1261                               i, vq->num, head);
1262                        return -EINVAL;
1263                }
1264                if (unlikely(++found > vq->num)) {
1265                        vq_err(vq, "Loop detected: last one at %u "
1266                               "vq size %u head %u\n",
1267                               i, vq->num, head);
1268                        return -EINVAL;
1269                }
1270                ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
1271                if (unlikely(ret)) {
1272                        vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1273                               i, vq->desc + i);
1274                        return -EFAULT;
1275                }
1276                if (desc.flags & VRING_DESC_F_INDIRECT) {
1277                        ret = get_indirect(dev, vq, iov, iov_size,
1278                                           out_num, in_num,
1279                                           log, log_num, &desc);
1280                        if (unlikely(ret < 0)) {
1281                                vq_err(vq, "Failure detected "
1282                                       "in indirect descriptor at idx %d\n", i);
1283                                return ret;
1284                        }
1285                        continue;
1286                }
1287
1288                ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1289                                     iov_size - iov_count);
1290                if (unlikely(ret < 0)) {
1291                        vq_err(vq, "Translation failure %d descriptor idx %d\n",
1292                               ret, i);
1293                        return ret;
1294                }
1295                if (desc.flags & VRING_DESC_F_WRITE) {
1296                        /* If this is an input descriptor,
1297                         * increment that count. */
1298                        *in_num += ret;
1299                        if (unlikely(log)) {
1300                                log[*log_num].addr = desc.addr;
1301                                log[*log_num].len = desc.len;
1302                                ++*log_num;
1303                        }
1304                } else {
1305                        /* If it's an output descriptor, they're all supposed
1306                         * to come before any input descriptors. */
1307                        if (unlikely(*in_num)) {
1308                                vq_err(vq, "Descriptor has out after in: "
1309                                       "idx %d\n", i);
1310                                return -EINVAL;
1311                        }
1312                        *out_num += ret;
1313                }
1314        } while ((i = next_desc(&desc)) != -1);
1315
1316        /* On success, increment avail index. */
1317        vq->last_avail_idx++;
1318
1319        /* Assume notifications from guest are disabled at this point,
1320         * if they aren't we would need to update avail_event index. */
1321        BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
1322        return head;
1323}
1324EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
1325
1326/* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1327void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1328{
1329        vq->last_avail_idx -= n;
1330}
1331EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);
1332
1333/* After we've used one of their buffers, we tell them about it.  We'll then
1334 * want to notify the guest, using eventfd. */
1335int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1336{
1337        struct vring_used_elem heads = { head, len };
1338
1339        return vhost_add_used_n(vq, &heads, 1);
1340}
1341EXPORT_SYMBOL_GPL(vhost_add_used);
1342
1343static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1344                            struct vring_used_elem *heads,
1345                            unsigned count)
1346{
1347        struct vring_used_elem __user *used;
1348        u16 old, new;
1349        int start;
1350
1351        start = vq->last_used_idx % vq->num;
1352        used = vq->used->ring + start;
1353        if (count == 1) {
1354                if (__put_user(heads[0].id, &used->id)) {
1355                        vq_err(vq, "Failed to write used id");
1356                        return -EFAULT;
1357                }
1358                if (__put_user(heads[0].len, &used->len)) {
1359                        vq_err(vq, "Failed to write used len");
1360                        return -EFAULT;
1361                }
1362        } else if (__copy_to_user(used, heads, count * sizeof *used)) {
1363                vq_err(vq, "Failed to write used");
1364                return -EFAULT;
1365        }
1366        if (unlikely(vq->log_used)) {
1367                /* Make sure data is seen before log. */
1368                smp_wmb();
1369                /* Log used ring entry write. */
1370                log_write(vq->log_base,
1371                          vq->log_addr +
1372                           ((void __user *)used - (void __user *)vq->used),
1373                          count * sizeof *used);
1374        }
1375        old = vq->last_used_idx;
1376        new = (vq->last_used_idx += count);
1377        /* If the driver never bothers to signal in a very long while,
1378         * used index might wrap around. If that happens, invalidate
1379         * signalled_used index we stored. TODO: make sure driver
1380         * signals at least once in 2^16 and remove this. */
1381        if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
1382                vq->signalled_used_valid = false;
1383        return 0;
1384}
1385
1386/* After we've used one of their buffers, we tell them about it.  We'll then
1387 * want to notify the guest, using eventfd. */
1388int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1389                     unsigned count)
1390{
1391        int start, n, r;
1392
1393        start = vq->last_used_idx % vq->num;
1394        n = vq->num - start;
1395        if (n < count) {
1396                r = __vhost_add_used_n(vq, heads, n);
1397                if (r < 0)
1398                        return r;
1399                heads += n;
1400                count -= n;
1401        }
1402        r = __vhost_add_used_n(vq, heads, count);
1403
1404        /* Make sure buffer is written before we update index. */
1405        smp_wmb();
1406        if (put_user(vq->last_used_idx, &vq->used->idx)) {
1407                vq_err(vq, "Failed to increment used idx");
1408                return -EFAULT;
1409        }
1410        if (unlikely(vq->log_used)) {
1411                /* Log used index update. */
1412                log_write(vq->log_base,
1413                          vq->log_addr + offsetof(struct vring_used, idx),
1414                          sizeof vq->used->idx);
1415                if (vq->log_ctx)
1416                        eventfd_signal(vq->log_ctx, 1);
1417        }
1418        return r;
1419}
1420EXPORT_SYMBOL_GPL(vhost_add_used_n);
1421
1422static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1423{
1424        __u16 old, new, event;
1425        bool v;
1426        /* Flush out used index updates. This is paired
1427         * with the barrier that the Guest executes when enabling
1428         * interrupts. */
1429        smp_mb();
1430
1431        if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
1432            unlikely(vq->avail_idx == vq->last_avail_idx))
1433                return true;
1434
1435        if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1436                __u16 flags;
1437                if (__get_user(flags, &vq->avail->flags)) {
1438                        vq_err(vq, "Failed to get flags");
1439                        return true;
1440                }
1441                return !(flags & VRING_AVAIL_F_NO_INTERRUPT);
1442        }
1443        old = vq->signalled_used;
1444        v = vq->signalled_used_valid;
1445        new = vq->signalled_used = vq->last_used_idx;
1446        vq->signalled_used_valid = true;
1447
1448        if (unlikely(!v))
1449                return true;
1450
1451        if (get_user(event, vhost_used_event(vq))) {
1452                vq_err(vq, "Failed to get used event idx");
1453                return true;
1454        }
1455        return vring_need_event(event, new, old);
1456}
1457
1458/* This actually signals the guest, using eventfd. */
1459void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1460{
1461        /* Signal the Guest tell them we used something up. */
1462        if (vq->call_ctx && vhost_notify(dev, vq))
1463                eventfd_signal(vq->call_ctx, 1);
1464}
1465EXPORT_SYMBOL_GPL(vhost_signal);
1466
1467/* And here's the combo meal deal.  Supersize me! */
1468void vhost_add_used_and_signal(struct vhost_dev *dev,
1469                               struct vhost_virtqueue *vq,
1470                               unsigned int head, int len)
1471{
1472        vhost_add_used(vq, head, len);
1473        vhost_signal(dev, vq);
1474}
1475EXPORT_SYMBOL_GPL(vhost_add_used_and_signal);
1476
1477/* multi-buffer version of vhost_add_used_and_signal */
1478void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1479                                 struct vhost_virtqueue *vq,
1480                                 struct vring_used_elem *heads, unsigned count)
1481{
1482        vhost_add_used_n(vq, heads, count);
1483        vhost_signal(dev, vq);
1484}
1485EXPORT_SYMBOL_GPL(vhost_add_used_and_signal_n);
1486
1487/* OK, now we need to know about added descriptors. */
1488bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1489{
1490        u16 avail_idx;
1491        int r;
1492
1493        if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1494                return false;
1495        vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1496        if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1497                r = vhost_update_used_flags(vq);
1498                if (r) {
1499                        vq_err(vq, "Failed to enable notification at %p: %d\n",
1500                               &vq->used->flags, r);
1501                        return false;
1502                }
1503        } else {
1504                r = vhost_update_avail_event(vq, vq->avail_idx);
1505                if (r) {
1506                        vq_err(vq, "Failed to update avail event index at %p: %d\n",
1507                               vhost_avail_event(vq), r);
1508                        return false;
1509                }
1510        }
1511        /* They could have slipped one in as we were doing that: make
1512         * sure it's written, then check again. */
1513        smp_mb();
1514        r = __get_user(avail_idx, &vq->avail->idx);
1515        if (r) {
1516                vq_err(vq, "Failed to check avail idx at %p: %d\n",
1517                       &vq->avail->idx, r);
1518                return false;
1519        }
1520
1521        return avail_idx != vq->avail_idx;
1522}
1523EXPORT_SYMBOL_GPL(vhost_enable_notify);
1524
1525/* We don't need to be notified again. */
1526void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1527{
1528        int r;
1529
1530        if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1531                return;
1532        vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1533        if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1534                r = vhost_update_used_flags(vq);
1535                if (r)
1536                        vq_err(vq, "Failed to enable notification at %p: %d\n",
1537                               &vq->used->flags, r);
1538        }
1539}
1540EXPORT_SYMBOL_GPL(vhost_disable_notify);
1541
1542static int __init vhost_init(void)
1543{
1544        return 0;
1545}
1546
1547static void __exit vhost_exit(void)
1548{
1549}
1550
1551module_init(vhost_init);
1552module_exit(vhost_exit);
1553
1554MODULE_VERSION("0.0.1");
1555MODULE_LICENSE("GPL v2");
1556MODULE_AUTHOR("Michael S. Tsirkin");
1557MODULE_DESCRIPTION("Host kernel accelerator for virtio");
1558
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