1/* Virtio ring implementation.
  2 *
  3 *  Copyright 2007 Rusty Russell IBM Corporation
  4 *
  5 *  This program is free software; you can redistribute it and/or modify
  6 *  it under the terms of the GNU General Public License as published by
  7 *  the Free Software Foundation; either version 2 of the License, or
  8 *  (at your option) any later version.
  9 *
 10 *  This program is distributed in the hope that it will be useful,
 11 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 12 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 13 *  GNU General Public License for more details.
 14 *
 15 *  You should have received a copy of the GNU General Public License
 16 *  along with this program; if not, write to the Free Software
 17 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 18 */
 19#include <linux/virtio.h>
 20#include <linux/virtio_ring.h>
 21#include <linux/virtio_config.h>
 22#include <linux/device.h>
 23#include <linux/slab.h>
 24
 25/* virtio guest is communicating with a virtual "device" that actually runs on
 26 * a host processor.  Memory barriers are used to control SMP effects. */
 27#ifdef CONFIG_SMP
 28/* Where possible, use SMP barriers which are more lightweight than mandatory
 29 * barriers, because mandatory barriers control MMIO effects on accesses
 30 * through relaxed memory I/O windows (which virtio does not use). */
 31#define virtio_mb() smp_mb()
 32#define virtio_rmb() smp_rmb()
 33#define virtio_wmb() smp_wmb()
 34#else
 35/* We must force memory ordering even if guest is UP since host could be
 36 * running on another CPU, but SMP barriers are defined to barrier() in that
 37 * configuration. So fall back to mandatory barriers instead. */
 38#define virtio_mb() mb()
 39#define virtio_rmb() rmb()
 40#define virtio_wmb() wmb()
 41#endif
 42
 43#ifdef DEBUG
 44/* For development, we want to crash whenever the ring is screwed. */
 45#define BAD_RING(_vq, fmt, args...)				\
 46	do {							\
 47		dev_err(&(_vq)->vq.vdev->dev,			\
 48			"%s:"fmt, (_vq)->vq.name, ##args);	\
 49		BUG();						\
 50	} while (0)
 51/* Caller is supposed to guarantee no reentry. */
 52#define START_USE(_vq)						\
 53	do {							\
 54		if ((_vq)->in_use)				\
 55			panic("%s:in_use = %i\n",		\
 56			      (_vq)->vq.name, (_vq)->in_use);	\
 57		(_vq)->in_use = __LINE__;			\
 58	} while (0)
 59#define END_USE(_vq) \
 60	do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 61#else
 62#define BAD_RING(_vq, fmt, args...)				\
 63	do {							\
 64		dev_err(&_vq->vq.vdev->dev,			\
 65			"%s:"fmt, (_vq)->vq.name, ##args);	\
 66		(_vq)->broken = true;				\
 67	} while (0)
 68#define START_USE(vq)
 69#define END_USE(vq)
 
 
 
 70#endif
 71
 72struct vring_virtqueue
 73{
 74	struct virtqueue vq;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 75
 76	/* Actual memory layout for this queue */
 
 77	struct vring vring;
 78
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 79	/* Other side has made a mess, don't try any more. */
 80	bool broken;
 81
 82	/* Host supports indirect buffers */
 83	bool indirect;
 84
 85	/* Host publishes avail event idx */
 86	bool event;
 87
 88	/* Number of free buffers */
 89	unsigned int num_free;
 90	/* Head of free buffer list. */
 91	unsigned int free_head;
 92	/* Number we've added since last sync. */
 93	unsigned int num_added;
 94
 95	/* Last used index we've seen. */
 
 
 
 
 
 96	u16 last_used_idx;
 97
 
 
 
 
 
 
 
 
 
 
 
 98	/* How to notify other side. FIXME: commonalize hcalls! */
 99	void (*notify)(struct virtqueue *vq);
 
 
 
 
 
 
100
101#ifdef DEBUG
102	/* They're supposed to lock for us. */
103	unsigned int in_use;
104#endif
105
106	/* Tokens for callbacks. */
107	void *data[];
 
 
108};
109
110#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
 
 
 
 
 
 
 
111
112/* Set up an indirect table of descriptors and add it to the queue. */
113static int vring_add_indirect(struct vring_virtqueue *vq,
114			      struct scatterlist sg[],
115			      unsigned int out,
116			      unsigned int in,
117			      gfp_t gfp)
118{
119	struct vring_desc *desc;
120	unsigned head;
121	int i;
 
 
 
122
123	desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp);
124	if (!desc)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
125		return -ENOMEM;
126
127	/* Transfer entries from the sg list into the indirect page */
128	for (i = 0; i < out; i++) {
129		desc[i].flags = VRING_DESC_F_NEXT;
130		desc[i].addr = sg_phys(sg);
131		desc[i].len = sg->length;
132		desc[i].next = i+1;
133		sg++;
134	}
135	for (; i < (out + in); i++) {
136		desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
137		desc[i].addr = sg_phys(sg);
138		desc[i].len = sg->length;
139		desc[i].next = i+1;
140		sg++;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
141	}
142
143	/* Last one doesn't continue. */
144	desc[i-1].flags &= ~VRING_DESC_F_NEXT;
145	desc[i-1].next = 0;
146
147	/* We're about to use a buffer */
148	vq->num_free--;
 
 
 
 
 
149
150	/* Use a single buffer which doesn't continue */
151	head = vq->free_head;
152	vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT;
153	vq->vring.desc[head].addr = virt_to_phys(desc);
154	vq->vring.desc[head].len = i * sizeof(struct vring_desc);
 
155
156	/* Update free pointer */
157	vq->free_head = vq->vring.desc[head].next;
 
 
 
158
159	return head;
 
 
 
 
 
160}
161
162int virtqueue_add_buf_gfp(struct virtqueue *_vq,
163			  struct scatterlist sg[],
164			  unsigned int out,
165			  unsigned int in,
166			  void *data,
167			  gfp_t gfp)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
168{
169	struct vring_virtqueue *vq = to_vvq(_vq);
170	unsigned int i, avail, uninitialized_var(prev);
 
 
 
171	int head;
 
172
173	START_USE(vq);
174
175	BUG_ON(data == NULL);
 
 
 
 
 
 
 
 
 
 
 
 
176
177	/* If the host supports indirect descriptor tables, and we have multiple
178	 * buffers, then go indirect. FIXME: tune this threshold */
179	if (vq->indirect && (out + in) > 1 && vq->num_free) {
180		head = vring_add_indirect(vq, sg, out, in, gfp);
181		if (likely(head >= 0))
182			goto add_head;
183	}
184
185	BUG_ON(out + in > vq->vring.num);
186	BUG_ON(out + in == 0);
 
 
 
 
 
 
 
 
 
 
 
 
187
188	if (vq->num_free < out + in) {
189		pr_debug("Can't add buf len %i - avail = %i\n",
190			 out + in, vq->num_free);
191		/* FIXME: for historical reasons, we force a notify here if
192		 * there are outgoing parts to the buffer.  Presumably the
193		 * host should service the ring ASAP. */
194		if (out)
195			vq->notify(&vq->vq);
 
 
196		END_USE(vq);
197		return -ENOSPC;
198	}
199
200	/* We're about to use some buffers from the free list. */
201	vq->num_free -= out + in;
202
203	head = vq->free_head;
204	for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) {
205		vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
206		vq->vring.desc[i].addr = sg_phys(sg);
207		vq->vring.desc[i].len = sg->length;
208		prev = i;
209		sg++;
210	}
211	for (; in; i = vq->vring.desc[i].next, in--) {
212		vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
213		vq->vring.desc[i].addr = sg_phys(sg);
214		vq->vring.desc[i].len = sg->length;
215		prev = i;
216		sg++;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
217	}
218	/* Last one doesn't continue. */
219	vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
220
221	/* Update free pointer */
222	vq->free_head = i;
223
224add_head:
225	/* Set token. */
226	vq->data[head] = data;
 
 
 
 
 
 
 
 
 
227
228	/* Put entry in available array (but don't update avail->idx until they
229	 * do sync).  FIXME: avoid modulus here? */
230	avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num;
231	vq->vring.avail->ring[avail] = head;
 
 
 
 
 
 
 
 
232
233	pr_debug("Added buffer head %i to %p\n", head, vq);
234	END_USE(vq);
235
236	return vq->num_free;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
237}
238EXPORT_SYMBOL_GPL(virtqueue_add_buf_gfp);
239
240void virtqueue_kick(struct virtqueue *_vq)
241{
242	struct vring_virtqueue *vq = to_vvq(_vq);
243	u16 new, old;
 
 
244	START_USE(vq);
245	/* Descriptors and available array need to be set before we expose the
246	 * new available array entries. */
247	virtio_wmb();
248
249	old = vq->vring.avail->idx;
250	new = vq->vring.avail->idx = old + vq->num_added;
251	vq->num_added = 0;
252
253	/* Need to update avail index before checking if we should notify */
254	virtio_mb();
255
256	if (vq->event ?
257	    vring_need_event(vring_avail_event(&vq->vring), new, old) :
258	    !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
259		/* Prod other side to tell it about changes. */
260		vq->notify(&vq->vq);
261
 
 
 
 
 
 
 
 
 
262	END_USE(vq);
 
263}
264EXPORT_SYMBOL_GPL(virtqueue_kick);
265
266static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
 
267{
268	unsigned int i;
 
 
269
270	/* Clear data ptr. */
271	vq->data[head] = NULL;
272
273	/* Put back on free list: find end */
274	i = head;
275
276	/* Free the indirect table */
277	if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
278		kfree(phys_to_virt(vq->vring.desc[i].addr));
279
280	while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
281		i = vq->vring.desc[i].next;
282		vq->num_free++;
 
283	}
284
285	vq->vring.desc[i].next = vq->free_head;
 
286	vq->free_head = head;
 
287	/* Plus final descriptor */
288	vq->num_free++;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
289}
290
291static inline bool more_used(const struct vring_virtqueue *vq)
292{
293	return vq->last_used_idx != vq->vring.used->idx;
 
294}
295
296void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
 
 
297{
298	struct vring_virtqueue *vq = to_vvq(_vq);
299	void *ret;
300	unsigned int i;
 
301
302	START_USE(vq);
303
304	if (unlikely(vq->broken)) {
305		END_USE(vq);
306		return NULL;
307	}
308
309	if (!more_used(vq)) {
310		pr_debug("No more buffers in queue\n");
311		END_USE(vq);
312		return NULL;
313	}
314
315	/* Only get used array entries after they have been exposed by host. */
316	virtio_rmb();
317
318	i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
319	*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;
 
 
 
320
321	if (unlikely(i >= vq->vring.num)) {
322		BAD_RING(vq, "id %u out of range\n", i);
323		return NULL;
324	}
325	if (unlikely(!vq->data[i])) {
326		BAD_RING(vq, "id %u is not a head!\n", i);
327		return NULL;
328	}
329
330	/* detach_buf clears data, so grab it now. */
331	ret = vq->data[i];
332	detach_buf(vq, i);
333	vq->last_used_idx++;
334	/* If we expect an interrupt for the next entry, tell host
335	 * by writing event index and flush out the write before
336	 * the read in the next get_buf call. */
337	if (!(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) {
338		vring_used_event(&vq->vring) = vq->last_used_idx;
339		virtio_mb();
340	}
 
 
341
342	END_USE(vq);
343	return ret;
344}
345EXPORT_SYMBOL_GPL(virtqueue_get_buf);
346
347void virtqueue_disable_cb(struct virtqueue *_vq)
348{
349	struct vring_virtqueue *vq = to_vvq(_vq);
350
351	vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
352}
353EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
354
355bool virtqueue_enable_cb(struct virtqueue *_vq)
356{
357	struct vring_virtqueue *vq = to_vvq(_vq);
 
358
359	START_USE(vq);
360
361	/* We optimistically turn back on interrupts, then check if there was
362	 * more to do. */
363	/* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
364	 * either clear the flags bit or point the event index at the next
365	 * entry. Always do both to keep code simple. */
366	vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
367	vring_used_event(&vq->vring) = vq->last_used_idx;
368	virtio_mb();
369	if (unlikely(more_used(vq))) {
370		END_USE(vq);
371		return false;
372	}
373
 
374	END_USE(vq);
375	return true;
376}
377EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
378
379bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
 
 
 
 
 
 
 
 
380{
381	struct vring_virtqueue *vq = to_vvq(_vq);
382	u16 bufs;
383
384	START_USE(vq);
385
386	/* We optimistically turn back on interrupts, then check if there was
387	 * more to do. */
388	/* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
389	 * either clear the flags bit or point the event index at the next
390	 * entry. Always do both to keep code simple. */
391	vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
 
 
 
 
 
 
392	/* TODO: tune this threshold */
393	bufs = (u16)(vq->vring.avail->idx - vq->last_used_idx) * 3 / 4;
394	vring_used_event(&vq->vring) = vq->last_used_idx + bufs;
395	virtio_mb();
396	if (unlikely((u16)(vq->vring.used->idx - vq->last_used_idx) > bufs)) {
 
 
 
 
397		END_USE(vq);
398		return false;
399	}
400
401	END_USE(vq);
402	return true;
403}
404EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
405
406void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
407{
408	struct vring_virtqueue *vq = to_vvq(_vq);
409	unsigned int i;
410	void *buf;
411
412	START_USE(vq);
413
414	for (i = 0; i < vq->vring.num; i++) {
415		if (!vq->data[i])
416			continue;
417		/* detach_buf clears data, so grab it now. */
418		buf = vq->data[i];
419		detach_buf(vq, i);
420		vq->vring.avail->idx--;
 
 
421		END_USE(vq);
422		return buf;
423	}
424	/* That should have freed everything. */
425	BUG_ON(vq->num_free != vq->vring.num);
426
427	END_USE(vq);
428	return NULL;
429}
430EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
431
432irqreturn_t vring_interrupt(int irq, void *_vq)
 
433{
434	struct vring_virtqueue *vq = to_vvq(_vq);
435
436	if (!more_used(vq)) {
437		pr_debug("virtqueue interrupt with no work for %p\n", vq);
438		return IRQ_NONE;
 
 
 
 
 
 
 
 
439	}
 
440
441	if (unlikely(vq->broken))
442		return IRQ_HANDLED;
 
443
444	pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
445	if (vq->vq.callback)
446		vq->vq.callback(&vq->vq);
447
448	return IRQ_HANDLED;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
449}
450EXPORT_SYMBOL_GPL(vring_interrupt);
451
452struct virtqueue *vring_new_virtqueue(unsigned int num,
453				      unsigned int vring_align,
454				      struct virtio_device *vdev,
455				      void *pages,
456				      void (*notify)(struct virtqueue *),
457				      void (*callback)(struct virtqueue *),
458				      const char *name)
459{
460	struct vring_virtqueue *vq;
461	unsigned int i;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
462
463	/* We assume num is a power of 2. */
464	if (num & (num - 1)) {
465		dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
466		return NULL;
467	}
468
469	vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
470	if (!vq)
471		return NULL;
472
473	vring_init(&vq->vring, num, pages, vring_align);
474	vq->vq.callback = callback;
475	vq->vq.vdev = vdev;
476	vq->vq.name = name;
 
 
 
477	vq->notify = notify;
 
 
 
 
478	vq->broken = false;
479	vq->last_used_idx = 0;
480	vq->num_added = 0;
481	list_add_tail(&vq->vq.list, &vdev->vqs);
482#ifdef DEBUG
483	vq->in_use = false;
484#endif
 
 
485
486	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
 
487	vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
488
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
489	/* No callback?  Tell other side not to bother us. */
490	if (!callback)
491		vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
 
 
 
 
 
 
 
 
 
492
493	/* Put everything in free lists. */
494	vq->num_free = num;
495	vq->free_head = 0;
496	for (i = 0; i < num-1; i++) {
497		vq->vring.desc[i].next = i+1;
498		vq->data[i] = NULL;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
499	}
500	vq->data[i] = NULL;
501
 
 
 
 
 
 
 
 
502	return &vq->vq;
503}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
504EXPORT_SYMBOL_GPL(vring_new_virtqueue);
505
506void vring_del_virtqueue(struct virtqueue *vq)
507{
508	list_del(&vq->list);
509	kfree(to_vvq(vq));
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
510}
511EXPORT_SYMBOL_GPL(vring_del_virtqueue);
512
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
513/* Manipulates transport-specific feature bits. */
514void vring_transport_features(struct virtio_device *vdev)
515{
516	unsigned int i;
517
518	for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
519		switch (i) {
520		case VIRTIO_RING_F_INDIRECT_DESC:
521			break;
522		case VIRTIO_RING_F_EVENT_IDX:
523			break;
 
 
 
 
 
 
 
 
 
 
524		default:
525			/* We don't understand this bit. */
526			clear_bit(i, vdev->features);
527		}
528	}
529}
530EXPORT_SYMBOL_GPL(vring_transport_features);
531
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
532MODULE_LICENSE("GPL");