1 /* Virtio ring implementation.
3 * Copyright 2007 Rusty Russell IBM Corporation
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.
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.
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
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>
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. */
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()
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()
44 /* For development, we want to crash whenever the ring is screwed. */
45 #define BAD_RING(_vq, fmt, args...) \
47 dev_err(&(_vq)->vq.vdev->dev, \
48 "%s:"fmt, (_vq)->vq.name, ##args); \
51 /* Caller is supposed to guarantee no reentry. */
52 #define START_USE(_vq) \
55 panic("%s:in_use = %i\n", \
56 (_vq)->vq.name, (_vq)->in_use); \
57 (_vq)->in_use = __LINE__; \
59 #define END_USE(_vq) \
60 do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
62 #define BAD_RING(_vq, fmt, args...) \
64 dev_err(&_vq->vq.vdev->dev, \
65 "%s:"fmt, (_vq)->vq.name, ##args); \
66 (_vq)->broken = true; \
72 struct vring_virtqueue
76 /* Actual memory layout for this queue */
79 /* Other side has made a mess, don't try any more. */
82 /* Host supports indirect buffers */
85 /* Number of free buffers */
86 unsigned int num_free
;
87 /* Head of free buffer list. */
88 unsigned int free_head
;
89 /* Number we've added since last sync. */
90 unsigned int num_added
;
92 /* Last used index we've seen. */
95 void (*notify
)(struct virtqueue
*vq
);
98 /* They're supposed to lock for us. */
102 /* Tokens for callbacks. */
106 #define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
108 /* Set up an indirect table of descriptors and add it to the queue. */
109 static int vring_add_indirect(struct vring_virtqueue
*vq
,
110 struct scatterlist sg
[],
115 struct vring_desc
*desc
;
119 desc
= kmalloc((out
+ in
) * sizeof(struct vring_desc
), gfp
);
123 /* Transfer entries from the sg list into the indirect page */
124 for (i
= 0; i
< out
; i
++) {
125 desc
[i
].flags
= VRING_DESC_F_NEXT
;
126 desc
[i
].addr
= sg_phys(sg
);
127 desc
[i
].len
= sg
->length
;
131 for (; i
< (out
+ in
); i
++) {
132 desc
[i
].flags
= VRING_DESC_F_NEXT
|VRING_DESC_F_WRITE
;
133 desc
[i
].addr
= sg_phys(sg
);
134 desc
[i
].len
= sg
->length
;
139 /* Last one doesn't continue. */
140 desc
[i
-1].flags
&= ~VRING_DESC_F_NEXT
;
143 /* We're about to use a buffer */
146 /* Use a single buffer which doesn't continue */
147 head
= vq
->free_head
;
148 vq
->vring
.desc
[head
].flags
= VRING_DESC_F_INDIRECT
;
149 vq
->vring
.desc
[head
].addr
= virt_to_phys(desc
);
150 vq
->vring
.desc
[head
].len
= i
* sizeof(struct vring_desc
);
152 /* Update free pointer */
153 vq
->free_head
= vq
->vring
.desc
[head
].next
;
158 int virtqueue_add_buf_gfp(struct virtqueue
*_vq
,
159 struct scatterlist sg
[],
165 struct vring_virtqueue
*vq
= to_vvq(_vq
);
166 unsigned int i
, avail
, uninitialized_var(prev
);
171 BUG_ON(data
== NULL
);
173 if (vq
->indirect
&& (out
+ in
) > 1 && vq
->num_free
) {
174 head
= vring_add_indirect(vq
, sg
, out
, in
, gfp
);
175 if (likely(head
>= 0))
179 BUG_ON(out
+ in
> vq
->vring
.num
);
180 BUG_ON(out
+ in
== 0);
182 if (vq
->num_free
< out
+ in
) {
183 pr_debug("Can't add buf len %i - avail = %i\n",
184 out
+ in
, vq
->num_free
);
191 /* We're about to use some buffers from the free list. */
192 vq
->num_free
-= out
+ in
;
194 head
= vq
->free_head
;
195 for (i
= vq
->free_head
; out
; i
= vq
->vring
.desc
[i
].next
, out
--) {
196 vq
->vring
.desc
[i
].flags
= VRING_DESC_F_NEXT
;
197 vq
->vring
.desc
[i
].addr
= sg_phys(sg
);
198 vq
->vring
.desc
[i
].len
= sg
->length
;
202 for (; in
; i
= vq
->vring
.desc
[i
].next
, in
--) {
203 vq
->vring
.desc
[i
].flags
= VRING_DESC_F_NEXT
|VRING_DESC_F_WRITE
;
204 vq
->vring
.desc
[i
].addr
= sg_phys(sg
);
205 vq
->vring
.desc
[i
].len
= sg
->length
;
209 /* Last one doesn't continue. */
210 vq
->vring
.desc
[prev
].flags
&= ~VRING_DESC_F_NEXT
;
212 /* Update free pointer */
217 vq
->data
[head
] = data
;
219 avail
= (vq
->vring
.avail
->idx
+ vq
->num_added
++) % vq
->vring
.num
;
220 vq
->vring
.avail
->ring
[avail
] = head
;
222 pr_debug("Added buffer head %i to %p\n", head
, vq
);
225 /* If we're indirect, we can fit many (assuming not OOM). */
227 return vq
->num_free
? vq
->vring
.num
: 0;
230 EXPORT_SYMBOL_GPL(virtqueue_add_buf_gfp
);
232 void virtqueue_kick(struct virtqueue
*_vq
)
234 struct vring_virtqueue
*vq
= to_vvq(_vq
);
236 /* Descriptors and available array need to be set before we expose the
237 * new available array entries. */
240 vq
->vring
.avail
->idx
+= vq
->num_added
;
243 /* Need to update avail index before checking if we should notify */
246 if (!(vq
->vring
.used
->flags
& VRING_USED_F_NO_NOTIFY
))
247 /* Prod other side to tell it about changes. */
252 EXPORT_SYMBOL_GPL(virtqueue_kick
);
254 static void detach_buf(struct vring_virtqueue
*vq
, unsigned int head
)
258 /* Clear data ptr. */
259 vq
->data
[head
] = NULL
;
261 /* Put back on free list: find end */
264 /* Free the indirect table */
265 if (vq
->vring
.desc
[i
].flags
& VRING_DESC_F_INDIRECT
)
266 kfree(phys_to_virt(vq
->vring
.desc
[i
].addr
));
268 while (vq
->vring
.desc
[i
].flags
& VRING_DESC_F_NEXT
) {
269 i
= vq
->vring
.desc
[i
].next
;
273 vq
->vring
.desc
[i
].next
= vq
->free_head
;
274 vq
->free_head
= head
;
275 /* Plus final descriptor */
279 static inline bool more_used(const struct vring_virtqueue
*vq
)
281 return vq
->last_used_idx
!= vq
->vring
.used
->idx
;
284 void *virtqueue_get_buf(struct virtqueue
*_vq
, unsigned int *len
)
286 struct vring_virtqueue
*vq
= to_vvq(_vq
);
292 if (unlikely(vq
->broken
)) {
297 if (!more_used(vq
)) {
298 pr_debug("No more buffers in queue\n");
303 /* Only get used array entries after they have been exposed by host. */
306 i
= vq
->vring
.used
->ring
[vq
->last_used_idx
%vq
->vring
.num
].id
;
307 *len
= vq
->vring
.used
->ring
[vq
->last_used_idx
%vq
->vring
.num
].len
;
309 if (unlikely(i
>= vq
->vring
.num
)) {
310 BAD_RING(vq
, "id %u out of range\n", i
);
313 if (unlikely(!vq
->data
[i
])) {
314 BAD_RING(vq
, "id %u is not a head!\n", i
);
318 /* detach_buf clears data, so grab it now. */
325 EXPORT_SYMBOL_GPL(virtqueue_get_buf
);
327 void virtqueue_disable_cb(struct virtqueue
*_vq
)
329 struct vring_virtqueue
*vq
= to_vvq(_vq
);
331 vq
->vring
.avail
->flags
|= VRING_AVAIL_F_NO_INTERRUPT
;
333 EXPORT_SYMBOL_GPL(virtqueue_disable_cb
);
335 bool virtqueue_enable_cb(struct virtqueue
*_vq
)
337 struct vring_virtqueue
*vq
= to_vvq(_vq
);
341 /* We optimistically turn back on interrupts, then check if there was
343 vq
->vring
.avail
->flags
&= ~VRING_AVAIL_F_NO_INTERRUPT
;
345 if (unlikely(more_used(vq
))) {
353 EXPORT_SYMBOL_GPL(virtqueue_enable_cb
);
355 void *virtqueue_detach_unused_buf(struct virtqueue
*_vq
)
357 struct vring_virtqueue
*vq
= to_vvq(_vq
);
363 for (i
= 0; i
< vq
->vring
.num
; i
++) {
366 /* detach_buf clears data, so grab it now. */
372 /* That should have freed everything. */
373 BUG_ON(vq
->num_free
!= vq
->vring
.num
);
378 EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf
);
380 irqreturn_t
vring_interrupt(int irq
, void *_vq
)
382 struct vring_virtqueue
*vq
= to_vvq(_vq
);
384 if (!more_used(vq
)) {
385 pr_debug("virtqueue interrupt with no work for %p\n", vq
);
389 if (unlikely(vq
->broken
))
392 pr_debug("virtqueue callback for %p (%p)\n", vq
, vq
->vq
.callback
);
394 vq
->vq
.callback(&vq
->vq
);
398 EXPORT_SYMBOL_GPL(vring_interrupt
);
400 struct virtqueue
*vring_new_virtqueue(unsigned int num
,
401 unsigned int vring_align
,
402 struct virtio_device
*vdev
,
404 void (*notify
)(struct virtqueue
*),
405 void (*callback
)(struct virtqueue
*),
408 struct vring_virtqueue
*vq
;
411 /* We assume num is a power of 2. */
412 if (num
& (num
- 1)) {
413 dev_warn(&vdev
->dev
, "Bad virtqueue length %u\n", num
);
417 vq
= kmalloc(sizeof(*vq
) + sizeof(void *)*num
, GFP_KERNEL
);
421 vring_init(&vq
->vring
, num
, pages
, vring_align
);
422 vq
->vq
.callback
= callback
;
427 vq
->last_used_idx
= 0;
429 list_add_tail(&vq
->vq
.list
, &vdev
->vqs
);
434 vq
->indirect
= virtio_has_feature(vdev
, VIRTIO_RING_F_INDIRECT_DESC
);
436 /* No callback? Tell other side not to bother us. */
438 vq
->vring
.avail
->flags
|= VRING_AVAIL_F_NO_INTERRUPT
;
440 /* Put everything in free lists. */
443 for (i
= 0; i
< num
-1; i
++) {
444 vq
->vring
.desc
[i
].next
= i
+1;
451 EXPORT_SYMBOL_GPL(vring_new_virtqueue
);
453 void vring_del_virtqueue(struct virtqueue
*vq
)
458 EXPORT_SYMBOL_GPL(vring_del_virtqueue
);
460 /* Manipulates transport-specific feature bits. */
461 void vring_transport_features(struct virtio_device
*vdev
)
465 for (i
= VIRTIO_TRANSPORT_F_START
; i
< VIRTIO_TRANSPORT_F_END
; i
++) {
467 case VIRTIO_RING_F_INDIRECT_DESC
:
470 /* We don't understand this bit. */
471 clear_bit(i
, vdev
->features
);
475 EXPORT_SYMBOL_GPL(vring_transport_features
);
477 MODULE_LICENSE("GPL");