Root/drivers/vhost/vhost.c

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/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/miscdevice.h>
19#include <linux/mutex.h>
20#include <linux/workqueue.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
27#include <linux/net.h>
28#include <linux/if_packet.h>
29#include <linux/if_arp.h>
30
31#include <net/sock.h>
32
33#include "vhost.h"
34
35enum {
36    VHOST_MEMORY_MAX_NREGIONS = 64,
37    VHOST_MEMORY_F_LOG = 0x1,
38};
39
40static struct workqueue_struct *vhost_workqueue;
41
42static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
43                poll_table *pt)
44{
45    struct vhost_poll *poll;
46    poll = container_of(pt, struct vhost_poll, table);
47
48    poll->wqh = wqh;
49    add_wait_queue(wqh, &poll->wait);
50}
51
52static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
53                 void *key)
54{
55    struct vhost_poll *poll;
56    poll = container_of(wait, struct vhost_poll, wait);
57    if (!((unsigned long)key & poll->mask))
58        return 0;
59
60    queue_work(vhost_workqueue, &poll->work);
61    return 0;
62}
63
64/* Init poll structure */
65void vhost_poll_init(struct vhost_poll *poll, work_func_t func,
66             unsigned long mask)
67{
68    INIT_WORK(&poll->work, func);
69    init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
70    init_poll_funcptr(&poll->table, vhost_poll_func);
71    poll->mask = mask;
72}
73
74/* Start polling a file. We add ourselves to file's wait queue. The caller must
75 * keep a reference to a file until after vhost_poll_stop is called. */
76void vhost_poll_start(struct vhost_poll *poll, struct file *file)
77{
78    unsigned long mask;
79    mask = file->f_op->poll(file, &poll->table);
80    if (mask)
81        vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
82}
83
84/* Stop polling a file. After this function returns, it becomes safe to drop the
85 * file reference. You must also flush afterwards. */
86void vhost_poll_stop(struct vhost_poll *poll)
87{
88    remove_wait_queue(poll->wqh, &poll->wait);
89}
90
91/* Flush any work that has been scheduled. When calling this, don't hold any
92 * locks that are also used by the callback. */
93void vhost_poll_flush(struct vhost_poll *poll)
94{
95    flush_work(&poll->work);
96}
97
98void vhost_poll_queue(struct vhost_poll *poll)
99{
100    queue_work(vhost_workqueue, &poll->work);
101}
102
103static void vhost_vq_reset(struct vhost_dev *dev,
104               struct vhost_virtqueue *vq)
105{
106    vq->num = 1;
107    vq->desc = NULL;
108    vq->avail = NULL;
109    vq->used = NULL;
110    vq->last_avail_idx = 0;
111    vq->avail_idx = 0;
112    vq->last_used_idx = 0;
113    vq->used_flags = 0;
114    vq->used_flags = 0;
115    vq->log_used = false;
116    vq->log_addr = -1ull;
117    vq->hdr_size = 0;
118    vq->private_data = NULL;
119    vq->log_base = NULL;
120    vq->error_ctx = NULL;
121    vq->error = NULL;
122    vq->kick = NULL;
123    vq->call_ctx = NULL;
124    vq->call = NULL;
125    vq->log_ctx = NULL;
126}
127
128long vhost_dev_init(struct vhost_dev *dev,
129            struct vhost_virtqueue *vqs, int nvqs)
130{
131    int i;
132    dev->vqs = vqs;
133    dev->nvqs = nvqs;
134    mutex_init(&dev->mutex);
135    dev->log_ctx = NULL;
136    dev->log_file = NULL;
137    dev->memory = NULL;
138    dev->mm = NULL;
139
140    for (i = 0; i < dev->nvqs; ++i) {
141        dev->vqs[i].dev = dev;
142        mutex_init(&dev->vqs[i].mutex);
143        vhost_vq_reset(dev, dev->vqs + i);
144        if (dev->vqs[i].handle_kick)
145            vhost_poll_init(&dev->vqs[i].poll,
146                    dev->vqs[i].handle_kick,
147                    POLLIN);
148    }
149    return 0;
150}
151
152/* Caller should have device mutex */
153long vhost_dev_check_owner(struct vhost_dev *dev)
154{
155    /* Are you the owner? If not, I don't think you mean to do that */
156    return dev->mm == current->mm ? 0 : -EPERM;
157}
158
159/* Caller should have device mutex */
160static long vhost_dev_set_owner(struct vhost_dev *dev)
161{
162    /* Is there an owner already? */
163    if (dev->mm)
164        return -EBUSY;
165    /* No owner, become one */
166    dev->mm = get_task_mm(current);
167    return 0;
168}
169
170/* Caller should have device mutex */
171long vhost_dev_reset_owner(struct vhost_dev *dev)
172{
173    struct vhost_memory *memory;
174
175    /* Restore memory to default empty mapping. */
176    memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
177    if (!memory)
178        return -ENOMEM;
179
180    vhost_dev_cleanup(dev);
181
182    memory->nregions = 0;
183    dev->memory = memory;
184    return 0;
185}
186
187/* Caller should have device mutex */
188void vhost_dev_cleanup(struct vhost_dev *dev)
189{
190    int i;
191    for (i = 0; i < dev->nvqs; ++i) {
192        if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
193            vhost_poll_stop(&dev->vqs[i].poll);
194            vhost_poll_flush(&dev->vqs[i].poll);
195        }
196        if (dev->vqs[i].error_ctx)
197            eventfd_ctx_put(dev->vqs[i].error_ctx);
198        if (dev->vqs[i].error)
199            fput(dev->vqs[i].error);
200        if (dev->vqs[i].kick)
201            fput(dev->vqs[i].kick);
202        if (dev->vqs[i].call_ctx)
203            eventfd_ctx_put(dev->vqs[i].call_ctx);
204        if (dev->vqs[i].call)
205            fput(dev->vqs[i].call);
206        vhost_vq_reset(dev, dev->vqs + i);
207    }
208    if (dev->log_ctx)
209        eventfd_ctx_put(dev->log_ctx);
210    dev->log_ctx = NULL;
211    if (dev->log_file)
212        fput(dev->log_file);
213    dev->log_file = NULL;
214    /* No one will access memory at this point */
215    kfree(dev->memory);
216    dev->memory = NULL;
217    if (dev->mm)
218        mmput(dev->mm);
219    dev->mm = NULL;
220}
221
222static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
223{
224    u64 a = addr / VHOST_PAGE_SIZE / 8;
225    /* Make sure 64 bit math will not overflow. */
226    if (a > ULONG_MAX - (unsigned long)log_base ||
227        a + (unsigned long)log_base > ULONG_MAX)
228        return -EFAULT;
229
230    return access_ok(VERIFY_WRITE, log_base + a,
231             (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
232}
233
234/* Caller should have vq mutex and device mutex. */
235static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
236                   int log_all)
237{
238    int i;
239
240        if (!mem)
241                return 0;
242
243    for (i = 0; i < mem->nregions; ++i) {
244        struct vhost_memory_region *m = mem->regions + i;
245        unsigned long a = m->userspace_addr;
246        if (m->memory_size > ULONG_MAX)
247            return 0;
248        else if (!access_ok(VERIFY_WRITE, (void __user *)a,
249                    m->memory_size))
250            return 0;
251        else if (log_all && !log_access_ok(log_base,
252                           m->guest_phys_addr,
253                           m->memory_size))
254            return 0;
255    }
256    return 1;
257}
258
259/* Can we switch to this memory table? */
260/* Caller should have device mutex but not vq mutex */
261static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
262                int log_all)
263{
264    int i;
265    for (i = 0; i < d->nvqs; ++i) {
266        int ok;
267        mutex_lock(&d->vqs[i].mutex);
268        /* If ring is inactive, will check when it's enabled. */
269        if (d->vqs[i].private_data)
270            ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
271                         log_all);
272        else
273            ok = 1;
274        mutex_unlock(&d->vqs[i].mutex);
275        if (!ok)
276            return 0;
277    }
278    return 1;
279}
280
281static int vq_access_ok(unsigned int num,
282            struct vring_desc __user *desc,
283            struct vring_avail __user *avail,
284            struct vring_used __user *used)
285{
286    return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
287           access_ok(VERIFY_READ, avail,
288             sizeof *avail + num * sizeof *avail->ring) &&
289           access_ok(VERIFY_WRITE, used,
290            sizeof *used + num * sizeof *used->ring);
291}
292
293/* Can we log writes? */
294/* Caller should have device mutex but not vq mutex */
295int vhost_log_access_ok(struct vhost_dev *dev)
296{
297    return memory_access_ok(dev, dev->memory, 1);
298}
299
300/* Verify access for write logging. */
301/* Caller should have vq mutex and device mutex */
302static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
303{
304    return vq_memory_access_ok(log_base, vq->dev->memory,
305                vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
306        (!vq->log_used || log_access_ok(log_base, vq->log_addr,
307                    sizeof *vq->used +
308                    vq->num * sizeof *vq->used->ring));
309}
310
311/* Can we start vq? */
312/* Caller should have vq mutex and device mutex */
313int vhost_vq_access_ok(struct vhost_virtqueue *vq)
314{
315    return vq_access_ok(vq->num, vq->desc, vq->avail, vq->used) &&
316        vq_log_access_ok(vq, vq->log_base);
317}
318
319static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
320{
321    struct vhost_memory mem, *newmem, *oldmem;
322    unsigned long size = offsetof(struct vhost_memory, regions);
323    long r;
324    r = copy_from_user(&mem, m, size);
325    if (r)
326        return r;
327    if (mem.padding)
328        return -EOPNOTSUPP;
329    if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
330        return -E2BIG;
331    newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
332    if (!newmem)
333        return -ENOMEM;
334
335    memcpy(newmem, &mem, size);
336    r = copy_from_user(newmem->regions, m->regions,
337               mem.nregions * sizeof *m->regions);
338    if (r) {
339        kfree(newmem);
340        return r;
341    }
342
343    if (!memory_access_ok(d, newmem, vhost_has_feature(d, VHOST_F_LOG_ALL)))
344        return -EFAULT;
345    oldmem = d->memory;
346    rcu_assign_pointer(d->memory, newmem);
347    synchronize_rcu();
348    kfree(oldmem);
349    return 0;
350}
351
352static int init_used(struct vhost_virtqueue *vq,
353             struct vring_used __user *used)
354{
355    int r = put_user(vq->used_flags, &used->flags);
356    if (r)
357        return r;
358    return get_user(vq->last_used_idx, &used->idx);
359}
360
361static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
362{
363    struct file *eventfp, *filep = NULL,
364            *pollstart = NULL, *pollstop = NULL;
365    struct eventfd_ctx *ctx = NULL;
366    u32 __user *idxp = argp;
367    struct vhost_virtqueue *vq;
368    struct vhost_vring_state s;
369    struct vhost_vring_file f;
370    struct vhost_vring_addr a;
371    u32 idx;
372    long r;
373
374    r = get_user(idx, idxp);
375    if (r < 0)
376        return r;
377    if (idx > d->nvqs)
378        return -ENOBUFS;
379
380    vq = d->vqs + idx;
381
382    mutex_lock(&vq->mutex);
383
384    switch (ioctl) {
385    case VHOST_SET_VRING_NUM:
386        /* Resizing ring with an active backend?
387         * You don't want to do that. */
388        if (vq->private_data) {
389            r = -EBUSY;
390            break;
391        }
392        r = copy_from_user(&s, argp, sizeof s);
393        if (r < 0)
394            break;
395        if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
396            r = -EINVAL;
397            break;
398        }
399        vq->num = s.num;
400        break;
401    case VHOST_SET_VRING_BASE:
402        /* Moving base with an active backend?
403         * You don't want to do that. */
404        if (vq->private_data) {
405            r = -EBUSY;
406            break;
407        }
408        r = copy_from_user(&s, argp, sizeof s);
409        if (r < 0)
410            break;
411        if (s.num > 0xffff) {
412            r = -EINVAL;
413            break;
414        }
415        vq->last_avail_idx = s.num;
416        /* Forget the cached index value. */
417        vq->avail_idx = vq->last_avail_idx;
418        break;
419    case VHOST_GET_VRING_BASE:
420        s.index = idx;
421        s.num = vq->last_avail_idx;
422        r = copy_to_user(argp, &s, sizeof s);
423        break;
424    case VHOST_SET_VRING_ADDR:
425        r = copy_from_user(&a, argp, sizeof a);
426        if (r < 0)
427            break;
428        if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
429            r = -EOPNOTSUPP;
430            break;
431        }
432        /* For 32bit, verify that the top 32bits of the user
433           data are set to zero. */
434        if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
435            (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
436            (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
437            r = -EFAULT;
438            break;
439        }
440        if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
441            (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
442            (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
443            r = -EINVAL;
444            break;
445        }
446
447        /* We only verify access here if backend is configured.
448         * If it is not, we don't as size might not have been setup.
449         * We will verify when backend is configured. */
450        if (vq->private_data) {
451            if (!vq_access_ok(vq->num,
452                (void __user *)(unsigned long)a.desc_user_addr,
453                (void __user *)(unsigned long)a.avail_user_addr,
454                (void __user *)(unsigned long)a.used_user_addr)) {
455                r = -EINVAL;
456                break;
457            }
458
459            /* Also validate log access for used ring if enabled. */
460            if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
461                !log_access_ok(vq->log_base, a.log_guest_addr,
462                       sizeof *vq->used +
463                       vq->num * sizeof *vq->used->ring)) {
464                r = -EINVAL;
465                break;
466            }
467        }
468
469        r = init_used(vq, (struct vring_used __user *)(unsigned long)
470                  a.used_user_addr);
471        if (r)
472            break;
473        vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
474        vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
475        vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
476        vq->log_addr = a.log_guest_addr;
477        vq->used = (void __user *)(unsigned long)a.used_user_addr;
478        break;
479    case VHOST_SET_VRING_KICK:
480        r = copy_from_user(&f, argp, sizeof f);
481        if (r < 0)
482            break;
483        eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
484        if (IS_ERR(eventfp)) {
485            r = PTR_ERR(eventfp);
486            break;
487        }
488        if (eventfp != vq->kick) {
489            pollstop = filep = vq->kick;
490            pollstart = vq->kick = eventfp;
491        } else
492            filep = eventfp;
493        break;
494    case VHOST_SET_VRING_CALL:
495        r = copy_from_user(&f, argp, sizeof f);
496        if (r < 0)
497            break;
498        eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
499        if (IS_ERR(eventfp)) {
500            r = PTR_ERR(eventfp);
501            break;
502        }
503        if (eventfp != vq->call) {
504            filep = vq->call;
505            ctx = vq->call_ctx;
506            vq->call = eventfp;
507            vq->call_ctx = eventfp ?
508                eventfd_ctx_fileget(eventfp) : NULL;
509        } else
510            filep = eventfp;
511        break;
512    case VHOST_SET_VRING_ERR:
513        r = copy_from_user(&f, argp, sizeof f);
514        if (r < 0)
515            break;
516        eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
517        if (IS_ERR(eventfp)) {
518            r = PTR_ERR(eventfp);
519            break;
520        }
521        if (eventfp != vq->error) {
522            filep = vq->error;
523            vq->error = eventfp;
524            ctx = vq->error_ctx;
525            vq->error_ctx = eventfp ?
526                eventfd_ctx_fileget(eventfp) : NULL;
527        } else
528            filep = eventfp;
529        break;
530    default:
531        r = -ENOIOCTLCMD;
532    }
533
534    if (pollstop && vq->handle_kick)
535        vhost_poll_stop(&vq->poll);
536
537    if (ctx)
538        eventfd_ctx_put(ctx);
539    if (filep)
540        fput(filep);
541
542    if (pollstart && vq->handle_kick)
543        vhost_poll_start(&vq->poll, vq->kick);
544
545    mutex_unlock(&vq->mutex);
546
547    if (pollstop && vq->handle_kick)
548        vhost_poll_flush(&vq->poll);
549    return r;
550}
551
552/* Caller must have device mutex */
553long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
554{
555    void __user *argp = (void __user *)arg;
556    struct file *eventfp, *filep = NULL;
557    struct eventfd_ctx *ctx = NULL;
558    u64 p;
559    long r;
560    int i, fd;
561
562    /* If you are not the owner, you can become one */
563    if (ioctl == VHOST_SET_OWNER) {
564        r = vhost_dev_set_owner(d);
565        goto done;
566    }
567
568    /* You must be the owner to do anything else */
569    r = vhost_dev_check_owner(d);
570    if (r)
571        goto done;
572
573    switch (ioctl) {
574    case VHOST_SET_MEM_TABLE:
575        r = vhost_set_memory(d, argp);
576        break;
577    case VHOST_SET_LOG_BASE:
578        r = copy_from_user(&p, argp, sizeof p);
579        if (r < 0)
580            break;
581        if ((u64)(unsigned long)p != p) {
582            r = -EFAULT;
583            break;
584        }
585        for (i = 0; i < d->nvqs; ++i) {
586            struct vhost_virtqueue *vq;
587            void __user *base = (void __user *)(unsigned long)p;
588            vq = d->vqs + i;
589            mutex_lock(&vq->mutex);
590            /* If ring is inactive, will check when it's enabled. */
591            if (vq->private_data && !vq_log_access_ok(vq, base))
592                r = -EFAULT;
593            else
594                vq->log_base = base;
595            mutex_unlock(&vq->mutex);
596        }
597        break;
598    case VHOST_SET_LOG_FD:
599        r = get_user(fd, (int __user *)argp);
600        if (r < 0)
601            break;
602        eventfp = fd == -1 ? NULL : eventfd_fget(fd);
603        if (IS_ERR(eventfp)) {
604            r = PTR_ERR(eventfp);
605            break;
606        }
607        if (eventfp != d->log_file) {
608            filep = d->log_file;
609            ctx = d->log_ctx;
610            d->log_ctx = eventfp ?
611                eventfd_ctx_fileget(eventfp) : NULL;
612        } else
613            filep = eventfp;
614        for (i = 0; i < d->nvqs; ++i) {
615            mutex_lock(&d->vqs[i].mutex);
616            d->vqs[i].log_ctx = d->log_ctx;
617            mutex_unlock(&d->vqs[i].mutex);
618        }
619        if (ctx)
620            eventfd_ctx_put(ctx);
621        if (filep)
622            fput(filep);
623        break;
624    default:
625        r = vhost_set_vring(d, ioctl, argp);
626        break;
627    }
628done:
629    return r;
630}
631
632static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
633                             __u64 addr, __u32 len)
634{
635    struct vhost_memory_region *reg;
636    int i;
637    /* linear search is not brilliant, but we really have on the order of 6
638     * regions in practice */
639    for (i = 0; i < mem->nregions; ++i) {
640        reg = mem->regions + i;
641        if (reg->guest_phys_addr <= addr &&
642            reg->guest_phys_addr + reg->memory_size - 1 >= addr)
643            return reg;
644    }
645    return NULL;
646}
647
648/* TODO: This is really inefficient. We need something like get_user()
649 * (instruction directly accesses the data, with an exception table entry
650 * returning -EFAULT). See Documentation/x86/exception-tables.txt.
651 */
652static int set_bit_to_user(int nr, void __user *addr)
653{
654    unsigned long log = (unsigned long)addr;
655    struct page *page;
656    void *base;
657    int bit = nr + (log % PAGE_SIZE) * 8;
658    int r;
659    r = get_user_pages_fast(log, 1, 1, &page);
660    if (r < 0)
661        return r;
662    BUG_ON(r != 1);
663    base = kmap_atomic(page, KM_USER0);
664    set_bit(bit, base);
665    kunmap_atomic(base, KM_USER0);
666    set_page_dirty_lock(page);
667    put_page(page);
668    return 0;
669}
670
671static int log_write(void __user *log_base,
672             u64 write_address, u64 write_length)
673{
674    int r;
675    if (!write_length)
676        return 0;
677    write_address /= VHOST_PAGE_SIZE;
678    for (;;) {
679        u64 base = (u64)(unsigned long)log_base;
680        u64 log = base + write_address / 8;
681        int bit = write_address % 8;
682        if ((u64)(unsigned long)log != log)
683            return -EFAULT;
684        r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
685        if (r < 0)
686            return r;
687        if (write_length <= VHOST_PAGE_SIZE)
688            break;
689        write_length -= VHOST_PAGE_SIZE;
690        write_address += VHOST_PAGE_SIZE;
691    }
692    return r;
693}
694
695int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
696            unsigned int log_num, u64 len)
697{
698    int i, r;
699
700    /* Make sure data written is seen before log. */
701    smp_wmb();
702    for (i = 0; i < log_num; ++i) {
703        u64 l = min(log[i].len, len);
704        r = log_write(vq->log_base, log[i].addr, l);
705        if (r < 0)
706            return r;
707        len -= l;
708        if (!len)
709            return 0;
710    }
711    if (vq->log_ctx)
712        eventfd_signal(vq->log_ctx, 1);
713    /* Length written exceeds what we have stored. This is a bug. */
714    BUG();
715    return 0;
716}
717
718int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
719           struct iovec iov[], int iov_size)
720{
721    const struct vhost_memory_region *reg;
722    struct vhost_memory *mem;
723    struct iovec *_iov;
724    u64 s = 0;
725    int ret = 0;
726
727    rcu_read_lock();
728
729    mem = rcu_dereference(dev->memory);
730    while ((u64)len > s) {
731        u64 size;
732        if (ret >= iov_size) {
733            ret = -ENOBUFS;
734            break;
735        }
736        reg = find_region(mem, addr, len);
737        if (!reg) {
738            ret = -EFAULT;
739            break;
740        }
741        _iov = iov + ret;
742        size = reg->memory_size - addr + reg->guest_phys_addr;
743        _iov->iov_len = min((u64)len, size);
744        _iov->iov_base = (void *)(unsigned long)
745            (reg->userspace_addr + addr - reg->guest_phys_addr);
746        s += size;
747        addr += size;
748        ++ret;
749    }
750
751    rcu_read_unlock();
752    return ret;
753}
754
755/* Each buffer in the virtqueues is actually a chain of descriptors. This
756 * function returns the next descriptor in the chain,
757 * or -1U if we're at the end. */
758static unsigned next_desc(struct vring_desc *desc)
759{
760    unsigned int next;
761
762    /* If this descriptor says it doesn't chain, we're done. */
763    if (!(desc->flags & VRING_DESC_F_NEXT))
764        return -1U;
765
766    /* Check they're not leading us off end of descriptors. */
767    next = desc->next;
768    /* Make sure compiler knows to grab that: we don't want it changing! */
769    /* We will use the result as an index in an array, so most
770     * architectures only need a compiler barrier here. */
771    read_barrier_depends();
772
773    return next;
774}
775
776static unsigned get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
777                 struct iovec iov[], unsigned int iov_size,
778                 unsigned int *out_num, unsigned int *in_num,
779                 struct vhost_log *log, unsigned int *log_num,
780                 struct vring_desc *indirect)
781{
782    struct vring_desc desc;
783    unsigned int i = 0, count, found = 0;
784    int ret;
785
786    /* Sanity check */
787    if (indirect->len % sizeof desc) {
788        vq_err(vq, "Invalid length in indirect descriptor: "
789               "len 0x%llx not multiple of 0x%zx\n",
790               (unsigned long long)indirect->len,
791               sizeof desc);
792        return -EINVAL;
793    }
794
795    ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
796                 ARRAY_SIZE(vq->indirect));
797    if (ret < 0) {
798        vq_err(vq, "Translation failure %d in indirect.\n", ret);
799        return ret;
800    }
801
802    /* We will use the result as an address to read from, so most
803     * architectures only need a compiler barrier here. */
804    read_barrier_depends();
805
806    count = indirect->len / sizeof desc;
807    /* Buffers are chained via a 16 bit next field, so
808     * we can have at most 2^16 of these. */
809    if (count > USHORT_MAX + 1) {
810        vq_err(vq, "Indirect buffer length too big: %d\n",
811               indirect->len);
812        return -E2BIG;
813    }
814
815    do {
816        unsigned iov_count = *in_num + *out_num;
817        if (++found > count) {
818            vq_err(vq, "Loop detected: last one at %u "
819                   "indirect size %u\n",
820                   i, count);
821            return -EINVAL;
822        }
823        if (memcpy_fromiovec((unsigned char *)&desc, vq->indirect,
824                     sizeof desc)) {
825            vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
826                   i, (size_t)indirect->addr + i * sizeof desc);
827            return -EINVAL;
828        }
829        if (desc.flags & VRING_DESC_F_INDIRECT) {
830            vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
831                   i, (size_t)indirect->addr + i * sizeof desc);
832            return -EINVAL;
833        }
834
835        ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
836                     iov_size - iov_count);
837        if (ret < 0) {
838            vq_err(vq, "Translation failure %d indirect idx %d\n",
839                   ret, i);
840            return ret;
841        }
842        /* If this is an input descriptor, increment that count. */
843        if (desc.flags & VRING_DESC_F_WRITE) {
844            *in_num += ret;
845            if (unlikely(log)) {
846                log[*log_num].addr = desc.addr;
847                log[*log_num].len = desc.len;
848                ++*log_num;
849            }
850        } else {
851            /* If it's an output descriptor, they're all supposed
852             * to come before any input descriptors. */
853            if (*in_num) {
854                vq_err(vq, "Indirect descriptor "
855                       "has out after in: idx %d\n", i);
856                return -EINVAL;
857            }
858            *out_num += ret;
859        }
860    } while ((i = next_desc(&desc)) != -1);
861    return 0;
862}
863
864/* This looks in the virtqueue and for the first available buffer, and converts
865 * it to an iovec for convenient access. Since descriptors consist of some
866 * number of output then some number of input descriptors, it's actually two
867 * iovecs, but we pack them into one and note how many of each there were.
868 *
869 * This function returns the descriptor number found, or vq->num (which
870 * is never a valid descriptor number) if none was found. */
871unsigned vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
872               struct iovec iov[], unsigned int iov_size,
873               unsigned int *out_num, unsigned int *in_num,
874               struct vhost_log *log, unsigned int *log_num)
875{
876    struct vring_desc desc;
877    unsigned int i, head, found = 0;
878    u16 last_avail_idx;
879    int ret;
880
881    /* Check it isn't doing very strange things with descriptor numbers. */
882    last_avail_idx = vq->last_avail_idx;
883    if (get_user(vq->avail_idx, &vq->avail->idx)) {
884        vq_err(vq, "Failed to access avail idx at %p\n",
885               &vq->avail->idx);
886        return vq->num;
887    }
888
889    if ((u16)(vq->avail_idx - last_avail_idx) > vq->num) {
890        vq_err(vq, "Guest moved used index from %u to %u",
891               last_avail_idx, vq->avail_idx);
892        return vq->num;
893    }
894
895    /* If there's nothing new since last we looked, return invalid. */
896    if (vq->avail_idx == last_avail_idx)
897        return vq->num;
898
899    /* Only get avail ring entries after they have been exposed by guest. */
900    smp_rmb();
901
902    /* Grab the next descriptor number they're advertising, and increment
903     * the index we've seen. */
904    if (get_user(head, &vq->avail->ring[last_avail_idx % vq->num])) {
905        vq_err(vq, "Failed to read head: idx %d address %p\n",
906               last_avail_idx,
907               &vq->avail->ring[last_avail_idx % vq->num]);
908        return vq->num;
909    }
910
911    /* If their number is silly, that's an error. */
912    if (head >= vq->num) {
913        vq_err(vq, "Guest says index %u > %u is available",
914               head, vq->num);
915        return vq->num;
916    }
917
918    /* When we start there are none of either input nor output. */
919    *out_num = *in_num = 0;
920    if (unlikely(log))
921        *log_num = 0;
922
923    i = head;
924    do {
925        unsigned iov_count = *in_num + *out_num;
926        if (i >= vq->num) {
927            vq_err(vq, "Desc index is %u > %u, head = %u",
928                   i, vq->num, head);
929            return vq->num;
930        }
931        if (++found > vq->num) {
932            vq_err(vq, "Loop detected: last one at %u "
933                   "vq size %u head %u\n",
934                   i, vq->num, head);
935            return vq->num;
936        }
937        ret = copy_from_user(&desc, vq->desc + i, sizeof desc);
938        if (ret) {
939            vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
940                   i, vq->desc + i);
941            return vq->num;
942        }
943        if (desc.flags & VRING_DESC_F_INDIRECT) {
944            ret = get_indirect(dev, vq, iov, iov_size,
945                       out_num, in_num,
946                       log, log_num, &desc);
947            if (ret < 0) {
948                vq_err(vq, "Failure detected "
949                       "in indirect descriptor at idx %d\n", i);
950                return vq->num;
951            }
952            continue;
953        }
954
955        ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
956                     iov_size - iov_count);
957        if (ret < 0) {
958            vq_err(vq, "Translation failure %d descriptor idx %d\n",
959                   ret, i);
960            return vq->num;
961        }
962        if (desc.flags & VRING_DESC_F_WRITE) {
963            /* If this is an input descriptor,
964             * increment that count. */
965            *in_num += ret;
966            if (unlikely(log)) {
967                log[*log_num].addr = desc.addr;
968                log[*log_num].len = desc.len;
969                ++*log_num;
970            }
971        } else {
972            /* If it's an output descriptor, they're all supposed
973             * to come before any input descriptors. */
974            if (*in_num) {
975                vq_err(vq, "Descriptor has out after in: "
976                       "idx %d\n", i);
977                return vq->num;
978            }
979            *out_num += ret;
980        }
981    } while ((i = next_desc(&desc)) != -1);
982
983    /* On success, increment avail index. */
984    vq->last_avail_idx++;
985    return head;
986}
987
988/* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
989void vhost_discard_vq_desc(struct vhost_virtqueue *vq)
990{
991    vq->last_avail_idx--;
992}
993
994/* After we've used one of their buffers, we tell them about it. We'll then
995 * want to notify the guest, using eventfd. */
996int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
997{
998    struct vring_used_elem *used;
999
1000    /* The virtqueue contains a ring of used buffers. Get a pointer to the
1001     * next entry in that used ring. */
1002    used = &vq->used->ring[vq->last_used_idx % vq->num];
1003    if (put_user(head, &used->id)) {
1004        vq_err(vq, "Failed to write used id");
1005        return -EFAULT;
1006    }
1007    if (put_user(len, &used->len)) {
1008        vq_err(vq, "Failed to write used len");
1009        return -EFAULT;
1010    }
1011    /* Make sure buffer is written before we update index. */
1012    smp_wmb();
1013    if (put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1014        vq_err(vq, "Failed to increment used idx");
1015        return -EFAULT;
1016    }
1017    if (unlikely(vq->log_used)) {
1018        /* Make sure data is seen before log. */
1019        smp_wmb();
1020        /* Log used ring entry write. */
1021        log_write(vq->log_base,
1022              vq->log_addr + ((void *)used - (void *)vq->used),
1023              sizeof *used);
1024        /* Log used index update. */
1025        log_write(vq->log_base,
1026              vq->log_addr + offsetof(struct vring_used, idx),
1027              sizeof vq->used->idx);
1028        if (vq->log_ctx)
1029            eventfd_signal(vq->log_ctx, 1);
1030    }
1031    vq->last_used_idx++;
1032    return 0;
1033}
1034
1035/* This actually signals the guest, using eventfd. */
1036void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1037{
1038    __u16 flags;
1039    /* Flush out used index updates. This is paired
1040     * with the barrier that the Guest executes when enabling
1041     * interrupts. */
1042    smp_mb();
1043
1044    if (get_user(flags, &vq->avail->flags)) {
1045        vq_err(vq, "Failed to get flags");
1046        return;
1047    }
1048
1049    /* If they don't want an interrupt, don't signal, unless empty. */
1050    if ((flags & VRING_AVAIL_F_NO_INTERRUPT) &&
1051        (vq->avail_idx != vq->last_avail_idx ||
1052         !vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY)))
1053        return;
1054
1055    /* Signal the Guest tell them we used something up. */
1056    if (vq->call_ctx)
1057        eventfd_signal(vq->call_ctx, 1);
1058}
1059
1060/* And here's the combo meal deal. Supersize me! */
1061void vhost_add_used_and_signal(struct vhost_dev *dev,
1062                   struct vhost_virtqueue *vq,
1063                   unsigned int head, int len)
1064{
1065    vhost_add_used(vq, head, len);
1066    vhost_signal(dev, vq);
1067}
1068
1069/* OK, now we need to know about added descriptors. */
1070bool vhost_enable_notify(struct vhost_virtqueue *vq)
1071{
1072    u16 avail_idx;
1073    int r;
1074    if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1075        return false;
1076    vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1077    r = put_user(vq->used_flags, &vq->used->flags);
1078    if (r) {
1079        vq_err(vq, "Failed to enable notification at %p: %d\n",
1080               &vq->used->flags, r);
1081        return false;
1082    }
1083    /* They could have slipped one in as we were doing that: make
1084     * sure it's written, then check again. */
1085    smp_mb();
1086    r = get_user(avail_idx, &vq->avail->idx);
1087    if (r) {
1088        vq_err(vq, "Failed to check avail idx at %p: %d\n",
1089               &vq->avail->idx, r);
1090        return false;
1091    }
1092
1093    return avail_idx != vq->last_avail_idx;
1094}
1095
1096/* We don't need to be notified again. */
1097void vhost_disable_notify(struct vhost_virtqueue *vq)
1098{
1099    int r;
1100    if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1101        return;
1102    vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1103    r = put_user(vq->used_flags, &vq->used->flags);
1104    if (r)
1105        vq_err(vq, "Failed to enable notification at %p: %d\n",
1106               &vq->used->flags, r);
1107}
1108
1109int vhost_init(void)
1110{
1111    vhost_workqueue = create_singlethread_workqueue("vhost");
1112    if (!vhost_workqueue)
1113        return -ENOMEM;
1114    return 0;
1115}
1116
1117void vhost_cleanup(void)
1118{
1119    destroy_workqueue(vhost_workqueue);
1120}
1121

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