1 /*
2  * vhost shadow virtqueue
3  *
4  * SPDX-FileCopyrightText: Red Hat, Inc. 2021
5  * SPDX-FileContributor: Author: Eugenio Pérez <eperezma@redhat.com>
6  *
7  * SPDX-License-Identifier: GPL-2.0-or-later
8  */
9 
10 #include "qemu/osdep.h"
11 #include "hw/virtio/vhost-shadow-virtqueue.h"
12 
13 #include "qemu/error-report.h"
14 #include "qapi/error.h"
15 #include "qemu/main-loop.h"
16 #include "qemu/log.h"
17 #include "qemu/memalign.h"
18 #include "linux-headers/linux/vhost.h"
19 
20 /**
21  * Validate the transport device features that both guests can use with the SVQ
22  * and SVQs can use with the device.
23  *
24  * @dev_features: The features
25  * @errp: Error pointer
26  */
27 bool vhost_svq_valid_features(uint64_t features, Error **errp)
28 {
29     bool ok = true;
30     uint64_t svq_features = features;
31 
32     for (uint64_t b = VIRTIO_TRANSPORT_F_START; b <= VIRTIO_TRANSPORT_F_END;
33          ++b) {
34         switch (b) {
35         case VIRTIO_F_ANY_LAYOUT:
36         case VIRTIO_RING_F_EVENT_IDX:
37             continue;
38 
39         case VIRTIO_F_ACCESS_PLATFORM:
40             /* SVQ trust in the host's IOMMU to translate addresses */
41         case VIRTIO_F_VERSION_1:
42             /* SVQ trust that the guest vring is little endian */
43             if (!(svq_features & BIT_ULL(b))) {
44                 svq_features |= BIT_ULL(b);
45                 ok = false;
46             }
47             continue;
48 
49         default:
50             if (svq_features & BIT_ULL(b)) {
51                 svq_features &= ~BIT_ULL(b);
52                 ok = false;
53             }
54         }
55     }
56 
57     if (!ok) {
58         error_setg(errp, "SVQ Invalid device feature flags, offer: 0x%"PRIx64
59                          ", ok: 0x%"PRIx64, features, svq_features);
60     }
61     return ok;
62 }
63 
64 /**
65  * Number of descriptors that the SVQ can make available from the guest.
66  *
67  * @svq: The svq
68  */
69 static uint16_t vhost_svq_available_slots(const VhostShadowVirtqueue *svq)
70 {
71     return svq->num_free;
72 }
73 
74 /**
75  * Translate addresses between the qemu's virtual address and the SVQ IOVA
76  *
77  * @svq: Shadow VirtQueue
78  * @vaddr: Translated IOVA addresses
79  * @iovec: Source qemu's VA addresses
80  * @num: Length of iovec and minimum length of vaddr
81  */
82 static bool vhost_svq_translate_addr(const VhostShadowVirtqueue *svq,
83                                      hwaddr *addrs, const struct iovec *iovec,
84                                      size_t num)
85 {
86     if (num == 0) {
87         return true;
88     }
89 
90     for (size_t i = 0; i < num; ++i) {
91         DMAMap needle = {
92             .translated_addr = (hwaddr)(uintptr_t)iovec[i].iov_base,
93             .size = iovec[i].iov_len,
94         };
95         Int128 needle_last, map_last;
96         size_t off;
97 
98         const DMAMap *map = vhost_iova_tree_find_iova(svq->iova_tree, &needle);
99         /*
100          * Map cannot be NULL since iova map contains all guest space and
101          * qemu already has a physical address mapped
102          */
103         if (unlikely(!map)) {
104             qemu_log_mask(LOG_GUEST_ERROR,
105                           "Invalid address 0x%"HWADDR_PRIx" given by guest",
106                           needle.translated_addr);
107             return false;
108         }
109 
110         off = needle.translated_addr - map->translated_addr;
111         addrs[i] = map->iova + off;
112 
113         needle_last = int128_add(int128_make64(needle.translated_addr),
114                                  int128_make64(iovec[i].iov_len));
115         map_last = int128_make64(map->translated_addr + map->size);
116         if (unlikely(int128_gt(needle_last, map_last))) {
117             qemu_log_mask(LOG_GUEST_ERROR,
118                           "Guest buffer expands over iova range");
119             return false;
120         }
121     }
122 
123     return true;
124 }
125 
126 /**
127  * Write descriptors to SVQ vring
128  *
129  * @svq: The shadow virtqueue
130  * @sg: Cache for hwaddr
131  * @iovec: The iovec from the guest
132  * @num: iovec length
133  * @more_descs: True if more descriptors come in the chain
134  * @write: True if they are writeable descriptors
135  *
136  * Return true if success, false otherwise and print error.
137  */
138 static bool vhost_svq_vring_write_descs(VhostShadowVirtqueue *svq, hwaddr *sg,
139                                         const struct iovec *iovec, size_t num,
140                                         bool more_descs, bool write)
141 {
142     uint16_t i = svq->free_head, last = svq->free_head;
143     unsigned n;
144     uint16_t flags = write ? cpu_to_le16(VRING_DESC_F_WRITE) : 0;
145     vring_desc_t *descs = svq->vring.desc;
146     bool ok;
147 
148     if (num == 0) {
149         return true;
150     }
151 
152     ok = vhost_svq_translate_addr(svq, sg, iovec, num);
153     if (unlikely(!ok)) {
154         return false;
155     }
156 
157     for (n = 0; n < num; n++) {
158         if (more_descs || (n + 1 < num)) {
159             descs[i].flags = flags | cpu_to_le16(VRING_DESC_F_NEXT);
160             descs[i].next = cpu_to_le16(svq->desc_next[i]);
161         } else {
162             descs[i].flags = flags;
163         }
164         descs[i].addr = cpu_to_le64(sg[n]);
165         descs[i].len = cpu_to_le32(iovec[n].iov_len);
166 
167         last = i;
168         i = cpu_to_le16(svq->desc_next[i]);
169     }
170 
171     svq->free_head = le16_to_cpu(svq->desc_next[last]);
172     return true;
173 }
174 
175 static bool vhost_svq_add_split(VhostShadowVirtqueue *svq,
176                                 const struct iovec *out_sg, size_t out_num,
177                                 const struct iovec *in_sg, size_t in_num,
178                                 unsigned *head)
179 {
180     unsigned avail_idx;
181     vring_avail_t *avail = svq->vring.avail;
182     bool ok;
183     g_autofree hwaddr *sgs = g_new(hwaddr, MAX(out_num, in_num));
184 
185     *head = svq->free_head;
186 
187     /* We need some descriptors here */
188     if (unlikely(!out_num && !in_num)) {
189         qemu_log_mask(LOG_GUEST_ERROR,
190                       "Guest provided element with no descriptors");
191         return false;
192     }
193 
194     ok = vhost_svq_vring_write_descs(svq, sgs, out_sg, out_num, in_num > 0,
195                                      false);
196     if (unlikely(!ok)) {
197         return false;
198     }
199 
200     ok = vhost_svq_vring_write_descs(svq, sgs, in_sg, in_num, false, true);
201     if (unlikely(!ok)) {
202         return false;
203     }
204 
205     /*
206      * Put the entry in the available array (but don't update avail->idx until
207      * they do sync).
208      */
209     avail_idx = svq->shadow_avail_idx & (svq->vring.num - 1);
210     avail->ring[avail_idx] = cpu_to_le16(*head);
211     svq->shadow_avail_idx++;
212 
213     /* Update the avail index after write the descriptor */
214     smp_wmb();
215     avail->idx = cpu_to_le16(svq->shadow_avail_idx);
216 
217     return true;
218 }
219 
220 static void vhost_svq_kick(VhostShadowVirtqueue *svq)
221 {
222     bool needs_kick;
223 
224     /*
225      * We need to expose the available array entries before checking the used
226      * flags
227      */
228     smp_mb();
229 
230     if (virtio_vdev_has_feature(svq->vdev, VIRTIO_RING_F_EVENT_IDX)) {
231         uint16_t avail_event = *(uint16_t *)(&svq->vring.used->ring[svq->vring.num]);
232         needs_kick = vring_need_event(avail_event, svq->shadow_avail_idx, svq->shadow_avail_idx - 1);
233     } else {
234         needs_kick = !(svq->vring.used->flags & VRING_USED_F_NO_NOTIFY);
235     }
236 
237     if (!needs_kick) {
238         return;
239     }
240 
241     event_notifier_set(&svq->hdev_kick);
242 }
243 
244 /**
245  * Add an element to a SVQ.
246  *
247  * Return -EINVAL if element is invalid, -ENOSPC if dev queue is full
248  */
249 int vhost_svq_add(VhostShadowVirtqueue *svq, const struct iovec *out_sg,
250                   size_t out_num, const struct iovec *in_sg, size_t in_num,
251                   VirtQueueElement *elem)
252 {
253     unsigned qemu_head;
254     unsigned ndescs = in_num + out_num;
255     bool ok;
256 
257     if (unlikely(ndescs > vhost_svq_available_slots(svq))) {
258         return -ENOSPC;
259     }
260 
261     ok = vhost_svq_add_split(svq, out_sg, out_num, in_sg, in_num, &qemu_head);
262     if (unlikely(!ok)) {
263         return -EINVAL;
264     }
265 
266     svq->num_free -= ndescs;
267     svq->desc_state[qemu_head].elem = elem;
268     svq->desc_state[qemu_head].ndescs = ndescs;
269     vhost_svq_kick(svq);
270     return 0;
271 }
272 
273 /* Convenience wrapper to add a guest's element to SVQ */
274 static int vhost_svq_add_element(VhostShadowVirtqueue *svq,
275                                  VirtQueueElement *elem)
276 {
277     return vhost_svq_add(svq, elem->out_sg, elem->out_num, elem->in_sg,
278                          elem->in_num, elem);
279 }
280 
281 /**
282  * Forward available buffers.
283  *
284  * @svq: Shadow VirtQueue
285  *
286  * Note that this function does not guarantee that all guest's available
287  * buffers are available to the device in SVQ avail ring. The guest may have
288  * exposed a GPA / GIOVA contiguous buffer, but it may not be contiguous in
289  * qemu vaddr.
290  *
291  * If that happens, guest's kick notifications will be disabled until the
292  * device uses some buffers.
293  */
294 static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)
295 {
296     /* Clear event notifier */
297     event_notifier_test_and_clear(&svq->svq_kick);
298 
299     /* Forward to the device as many available buffers as possible */
300     do {
301         virtio_queue_set_notification(svq->vq, false);
302 
303         while (true) {
304             g_autofree VirtQueueElement *elem = NULL;
305             int r;
306 
307             if (svq->next_guest_avail_elem) {
308                 elem = g_steal_pointer(&svq->next_guest_avail_elem);
309             } else {
310                 elem = virtqueue_pop(svq->vq, sizeof(*elem));
311             }
312 
313             if (!elem) {
314                 break;
315             }
316 
317             if (svq->ops) {
318                 r = svq->ops->avail_handler(svq, elem, svq->ops_opaque);
319             } else {
320                 r = vhost_svq_add_element(svq, elem);
321             }
322             if (unlikely(r != 0)) {
323                 if (r == -ENOSPC) {
324                     /*
325                      * This condition is possible since a contiguous buffer in
326                      * GPA does not imply a contiguous buffer in qemu's VA
327                      * scatter-gather segments. If that happens, the buffer
328                      * exposed to the device needs to be a chain of descriptors
329                      * at this moment.
330                      *
331                      * SVQ cannot hold more available buffers if we are here:
332                      * queue the current guest descriptor and ignore kicks
333                      * until some elements are used.
334                      */
335                     svq->next_guest_avail_elem = g_steal_pointer(&elem);
336                 }
337 
338                 /* VQ is full or broken, just return and ignore kicks */
339                 return;
340             }
341             /* elem belongs to SVQ or external caller now */
342             elem = NULL;
343         }
344 
345         virtio_queue_set_notification(svq->vq, true);
346     } while (!virtio_queue_empty(svq->vq));
347 }
348 
349 /**
350  * Handle guest's kick.
351  *
352  * @n: guest kick event notifier, the one that guest set to notify svq.
353  */
354 static void vhost_handle_guest_kick_notifier(EventNotifier *n)
355 {
356     VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue, svq_kick);
357     event_notifier_test_and_clear(n);
358     vhost_handle_guest_kick(svq);
359 }
360 
361 static bool vhost_svq_more_used(VhostShadowVirtqueue *svq)
362 {
363     uint16_t *used_idx = &svq->vring.used->idx;
364     if (svq->last_used_idx != svq->shadow_used_idx) {
365         return true;
366     }
367 
368     svq->shadow_used_idx = cpu_to_le16(*(volatile uint16_t *)used_idx);
369 
370     return svq->last_used_idx != svq->shadow_used_idx;
371 }
372 
373 /**
374  * Enable vhost device calls after disable them.
375  *
376  * @svq: The svq
377  *
378  * It returns false if there are pending used buffers from the vhost device,
379  * avoiding the possible races between SVQ checking for more work and enabling
380  * callbacks. True if SVQ used vring has no more pending buffers.
381  */
382 static bool vhost_svq_enable_notification(VhostShadowVirtqueue *svq)
383 {
384     if (virtio_vdev_has_feature(svq->vdev, VIRTIO_RING_F_EVENT_IDX)) {
385         uint16_t *used_event = (uint16_t *)&svq->vring.avail->ring[svq->vring.num];
386         *used_event = svq->shadow_used_idx;
387     } else {
388         svq->vring.avail->flags &= ~cpu_to_le16(VRING_AVAIL_F_NO_INTERRUPT);
389     }
390 
391     /* Make sure the event is enabled before the read of used_idx */
392     smp_mb();
393     return !vhost_svq_more_used(svq);
394 }
395 
396 static void vhost_svq_disable_notification(VhostShadowVirtqueue *svq)
397 {
398     /*
399      * No need to disable notification in the event idx case, since used event
400      * index is already an index too far away.
401      */
402     if (!virtio_vdev_has_feature(svq->vdev, VIRTIO_RING_F_EVENT_IDX)) {
403         svq->vring.avail->flags |= cpu_to_le16(VRING_AVAIL_F_NO_INTERRUPT);
404     }
405 }
406 
407 static uint16_t vhost_svq_last_desc_of_chain(const VhostShadowVirtqueue *svq,
408                                              uint16_t num, uint16_t i)
409 {
410     for (uint16_t j = 0; j < (num - 1); ++j) {
411         i = le16_to_cpu(svq->desc_next[i]);
412     }
413 
414     return i;
415 }
416 
417 static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
418                                            uint32_t *len)
419 {
420     const vring_used_t *used = svq->vring.used;
421     vring_used_elem_t used_elem;
422     uint16_t last_used, last_used_chain, num;
423 
424     if (!vhost_svq_more_used(svq)) {
425         return NULL;
426     }
427 
428     /* Only get used array entries after they have been exposed by dev */
429     smp_rmb();
430     last_used = svq->last_used_idx & (svq->vring.num - 1);
431     used_elem.id = le32_to_cpu(used->ring[last_used].id);
432     used_elem.len = le32_to_cpu(used->ring[last_used].len);
433 
434     svq->last_used_idx++;
435     if (unlikely(used_elem.id >= svq->vring.num)) {
436         qemu_log_mask(LOG_GUEST_ERROR, "Device %s says index %u is used",
437                       svq->vdev->name, used_elem.id);
438         return NULL;
439     }
440 
441     if (unlikely(!svq->desc_state[used_elem.id].ndescs)) {
442         qemu_log_mask(LOG_GUEST_ERROR,
443             "Device %s says index %u is used, but it was not available",
444             svq->vdev->name, used_elem.id);
445         return NULL;
446     }
447 
448     num = svq->desc_state[used_elem.id].ndescs;
449     svq->desc_state[used_elem.id].ndescs = 0;
450     last_used_chain = vhost_svq_last_desc_of_chain(svq, num, used_elem.id);
451     svq->desc_next[last_used_chain] = svq->free_head;
452     svq->free_head = used_elem.id;
453     svq->num_free += num;
454 
455     *len = used_elem.len;
456     return g_steal_pointer(&svq->desc_state[used_elem.id].elem);
457 }
458 
459 /**
460  * Push an element to SVQ, returning it to the guest.
461  */
462 void vhost_svq_push_elem(VhostShadowVirtqueue *svq,
463                          const VirtQueueElement *elem, uint32_t len)
464 {
465     virtqueue_push(svq->vq, elem, len);
466     if (svq->next_guest_avail_elem) {
467         /*
468          * Avail ring was full when vhost_svq_flush was called, so it's a
469          * good moment to make more descriptors available if possible.
470          */
471         vhost_handle_guest_kick(svq);
472     }
473 }
474 
475 static void vhost_svq_flush(VhostShadowVirtqueue *svq,
476                             bool check_for_avail_queue)
477 {
478     VirtQueue *vq = svq->vq;
479 
480     /* Forward as many used buffers as possible. */
481     do {
482         unsigned i = 0;
483 
484         vhost_svq_disable_notification(svq);
485         while (true) {
486             uint32_t len;
487             g_autofree VirtQueueElement *elem = vhost_svq_get_buf(svq, &len);
488             if (!elem) {
489                 break;
490             }
491 
492             if (unlikely(i >= svq->vring.num)) {
493                 qemu_log_mask(LOG_GUEST_ERROR,
494                          "More than %u used buffers obtained in a %u size SVQ",
495                          i, svq->vring.num);
496                 virtqueue_fill(vq, elem, len, i);
497                 virtqueue_flush(vq, i);
498                 return;
499             }
500             virtqueue_fill(vq, elem, len, i++);
501         }
502 
503         virtqueue_flush(vq, i);
504         event_notifier_set(&svq->svq_call);
505 
506         if (check_for_avail_queue && svq->next_guest_avail_elem) {
507             /*
508              * Avail ring was full when vhost_svq_flush was called, so it's a
509              * good moment to make more descriptors available if possible.
510              */
511             vhost_handle_guest_kick(svq);
512         }
513     } while (!vhost_svq_enable_notification(svq));
514 }
515 
516 /**
517  * Poll the SVQ for one device used buffer.
518  *
519  * This function race with main event loop SVQ polling, so extra
520  * synchronization is needed.
521  *
522  * Return the length written by the device.
523  */
524 size_t vhost_svq_poll(VhostShadowVirtqueue *svq)
525 {
526     int64_t start_us = g_get_monotonic_time();
527     uint32_t len = 0;
528 
529     do {
530         if (vhost_svq_more_used(svq)) {
531             break;
532         }
533 
534         if (unlikely(g_get_monotonic_time() - start_us > 10e6)) {
535             return 0;
536         }
537     } while (true);
538 
539     vhost_svq_get_buf(svq, &len);
540     return len;
541 }
542 
543 /**
544  * Forward used buffers.
545  *
546  * @n: hdev call event notifier, the one that device set to notify svq.
547  *
548  * Note that we are not making any buffers available in the loop, there is no
549  * way that it runs more than virtqueue size times.
550  */
551 static void vhost_svq_handle_call(EventNotifier *n)
552 {
553     VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue,
554                                              hdev_call);
555     event_notifier_test_and_clear(n);
556     vhost_svq_flush(svq, true);
557 }
558 
559 /**
560  * Set the call notifier for the SVQ to call the guest
561  *
562  * @svq: Shadow virtqueue
563  * @call_fd: call notifier
564  *
565  * Called on BQL context.
566  */
567 void vhost_svq_set_svq_call_fd(VhostShadowVirtqueue *svq, int call_fd)
568 {
569     if (call_fd == VHOST_FILE_UNBIND) {
570         /*
571          * Fail event_notifier_set if called handling device call.
572          *
573          * SVQ still needs device notifications, since it needs to keep
574          * forwarding used buffers even with the unbind.
575          */
576         memset(&svq->svq_call, 0, sizeof(svq->svq_call));
577     } else {
578         event_notifier_init_fd(&svq->svq_call, call_fd);
579     }
580 }
581 
582 /**
583  * Get the shadow vq vring address.
584  * @svq: Shadow virtqueue
585  * @addr: Destination to store address
586  */
587 void vhost_svq_get_vring_addr(const VhostShadowVirtqueue *svq,
588                               struct vhost_vring_addr *addr)
589 {
590     addr->desc_user_addr = (uint64_t)(uintptr_t)svq->vring.desc;
591     addr->avail_user_addr = (uint64_t)(uintptr_t)svq->vring.avail;
592     addr->used_user_addr = (uint64_t)(uintptr_t)svq->vring.used;
593 }
594 
595 size_t vhost_svq_driver_area_size(const VhostShadowVirtqueue *svq)
596 {
597     size_t desc_size = sizeof(vring_desc_t) * svq->vring.num;
598     size_t avail_size = offsetof(vring_avail_t, ring[svq->vring.num]) +
599                                                               sizeof(uint16_t);
600 
601     return ROUND_UP(desc_size + avail_size, qemu_real_host_page_size());
602 }
603 
604 size_t vhost_svq_device_area_size(const VhostShadowVirtqueue *svq)
605 {
606     size_t used_size = offsetof(vring_used_t, ring[svq->vring.num]) +
607                                                               sizeof(uint16_t);
608     return ROUND_UP(used_size, qemu_real_host_page_size());
609 }
610 
611 /**
612  * Set a new file descriptor for the guest to kick the SVQ and notify for avail
613  *
614  * @svq: The svq
615  * @svq_kick_fd: The svq kick fd
616  *
617  * Note that the SVQ will never close the old file descriptor.
618  */
619 void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd)
620 {
621     EventNotifier *svq_kick = &svq->svq_kick;
622     bool poll_stop = VHOST_FILE_UNBIND != event_notifier_get_fd(svq_kick);
623     bool poll_start = svq_kick_fd != VHOST_FILE_UNBIND;
624 
625     if (poll_stop) {
626         event_notifier_set_handler(svq_kick, NULL);
627     }
628 
629     event_notifier_init_fd(svq_kick, svq_kick_fd);
630     /*
631      * event_notifier_set_handler already checks for guest's notifications if
632      * they arrive at the new file descriptor in the switch, so there is no
633      * need to explicitly check for them.
634      */
635     if (poll_start) {
636         event_notifier_set(svq_kick);
637         event_notifier_set_handler(svq_kick, vhost_handle_guest_kick_notifier);
638     }
639 }
640 
641 /**
642  * Start the shadow virtqueue operation.
643  *
644  * @svq: Shadow Virtqueue
645  * @vdev: VirtIO device
646  * @vq: Virtqueue to shadow
647  * @iova_tree: Tree to perform descriptors translations
648  */
649 void vhost_svq_start(VhostShadowVirtqueue *svq, VirtIODevice *vdev,
650                      VirtQueue *vq, VhostIOVATree *iova_tree)
651 {
652     size_t desc_size, driver_size, device_size;
653 
654     event_notifier_set_handler(&svq->hdev_call, vhost_svq_handle_call);
655     svq->next_guest_avail_elem = NULL;
656     svq->shadow_avail_idx = 0;
657     svq->shadow_used_idx = 0;
658     svq->last_used_idx = 0;
659     svq->vdev = vdev;
660     svq->vq = vq;
661     svq->iova_tree = iova_tree;
662 
663     svq->vring.num = virtio_queue_get_num(vdev, virtio_get_queue_index(vq));
664     svq->num_free = svq->vring.num;
665     driver_size = vhost_svq_driver_area_size(svq);
666     device_size = vhost_svq_device_area_size(svq);
667     svq->vring.desc = qemu_memalign(qemu_real_host_page_size(), driver_size);
668     desc_size = sizeof(vring_desc_t) * svq->vring.num;
669     svq->vring.avail = (void *)((char *)svq->vring.desc + desc_size);
670     memset(svq->vring.desc, 0, driver_size);
671     svq->vring.used = qemu_memalign(qemu_real_host_page_size(), device_size);
672     memset(svq->vring.used, 0, device_size);
673     svq->desc_state = g_new0(SVQDescState, svq->vring.num);
674     svq->desc_next = g_new0(uint16_t, svq->vring.num);
675     for (unsigned i = 0; i < svq->vring.num - 1; i++) {
676         svq->desc_next[i] = cpu_to_le16(i + 1);
677     }
678 }
679 
680 /**
681  * Stop the shadow virtqueue operation.
682  * @svq: Shadow Virtqueue
683  */
684 void vhost_svq_stop(VhostShadowVirtqueue *svq)
685 {
686     vhost_svq_set_svq_kick_fd(svq, VHOST_FILE_UNBIND);
687     g_autofree VirtQueueElement *next_avail_elem = NULL;
688 
689     if (!svq->vq) {
690         return;
691     }
692 
693     /* Send all pending used descriptors to guest */
694     vhost_svq_flush(svq, false);
695 
696     for (unsigned i = 0; i < svq->vring.num; ++i) {
697         g_autofree VirtQueueElement *elem = NULL;
698         elem = g_steal_pointer(&svq->desc_state[i].elem);
699         if (elem) {
700             /*
701              * TODO: This is ok for networking, but other kinds of devices
702              * might have problems with just unpop these.
703              */
704             virtqueue_unpop(svq->vq, elem, 0);
705         }
706     }
707 
708     next_avail_elem = g_steal_pointer(&svq->next_guest_avail_elem);
709     if (next_avail_elem) {
710         virtqueue_unpop(svq->vq, next_avail_elem, 0);
711     }
712     svq->vq = NULL;
713     g_free(svq->desc_next);
714     g_free(svq->desc_state);
715     qemu_vfree(svq->vring.desc);
716     qemu_vfree(svq->vring.used);
717     event_notifier_set_handler(&svq->hdev_call, NULL);
718 }
719 
720 /**
721  * Creates vhost shadow virtqueue, and instructs the vhost device to use the
722  * shadow methods and file descriptors.
723  *
724  * @ops: SVQ owner callbacks
725  * @ops_opaque: ops opaque pointer
726  */
727 VhostShadowVirtqueue *vhost_svq_new(const VhostShadowVirtqueueOps *ops,
728                                     void *ops_opaque)
729 {
730     VhostShadowVirtqueue *svq = g_new0(VhostShadowVirtqueue, 1);
731 
732     event_notifier_init_fd(&svq->svq_kick, VHOST_FILE_UNBIND);
733     svq->ops = ops;
734     svq->ops_opaque = ops_opaque;
735     return svq;
736 }
737 
738 /**
739  * Free the resources of the shadow virtqueue.
740  *
741  * @pvq: gpointer to SVQ so it can be used by autofree functions.
742  */
743 void vhost_svq_free(gpointer pvq)
744 {
745     VhostShadowVirtqueue *vq = pvq;
746     vhost_svq_stop(vq);
747     g_free(vq);
748 }
749