blob: 5777196bf6c9cc873ef07dd6e79eb10f1775379b [file] [log] [blame]
Rusty Russell0a8a69d2007-10-22 11:03:40 +10001/* 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>
Rusty Russelle34f8722008-07-25 12:06:13 -050021#include <linux/virtio_config.h>
Rusty Russell0a8a69d2007-10-22 11:03:40 +100022#include <linux/device.h>
23
24#ifdef DEBUG
25/* For development, we want to crash whenever the ring is screwed. */
26#define BAD_RING(vq, fmt...) \
27 do { dev_err(&vq->vq.vdev->dev, fmt); BUG(); } while(0)
28#define START_USE(vq) \
29 do { if ((vq)->in_use) panic("in_use = %i\n", (vq)->in_use); (vq)->in_use = __LINE__; mb(); } while(0)
30#define END_USE(vq) \
31 do { BUG_ON(!(vq)->in_use); (vq)->in_use = 0; mb(); } while(0)
32#else
33#define BAD_RING(vq, fmt...) \
34 do { dev_err(&vq->vq.vdev->dev, fmt); (vq)->broken = true; } while(0)
35#define START_USE(vq)
36#define END_USE(vq)
37#endif
38
39struct vring_virtqueue
40{
41 struct virtqueue vq;
42
43 /* Actual memory layout for this queue */
44 struct vring vring;
45
46 /* Other side has made a mess, don't try any more. */
47 bool broken;
48
49 /* Number of free buffers */
50 unsigned int num_free;
51 /* Head of free buffer list. */
52 unsigned int free_head;
53 /* Number we've added since last sync. */
54 unsigned int num_added;
55
56 /* Last used index we've seen. */
Anthony Liguori1bc49532007-11-07 15:49:24 -060057 u16 last_used_idx;
Rusty Russell0a8a69d2007-10-22 11:03:40 +100058
59 /* How to notify other side. FIXME: commonalize hcalls! */
60 void (*notify)(struct virtqueue *vq);
61
62#ifdef DEBUG
63 /* They're supposed to lock for us. */
64 unsigned int in_use;
65#endif
66
67 /* Tokens for callbacks. */
68 void *data[];
69};
70
71#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
72
73static int vring_add_buf(struct virtqueue *_vq,
74 struct scatterlist sg[],
75 unsigned int out,
76 unsigned int in,
77 void *data)
78{
79 struct vring_virtqueue *vq = to_vvq(_vq);
80 unsigned int i, avail, head, uninitialized_var(prev);
81
82 BUG_ON(data == NULL);
83 BUG_ON(out + in > vq->vring.num);
84 BUG_ON(out + in == 0);
85
86 START_USE(vq);
87
88 if (vq->num_free < out + in) {
89 pr_debug("Can't add buf len %i - avail = %i\n",
90 out + in, vq->num_free);
Rusty Russell44653ea2008-07-25 12:06:04 -050091 /* FIXME: for historical reasons, we force a notify here if
92 * there are outgoing parts to the buffer. Presumably the
93 * host should service the ring ASAP. */
94 if (out)
95 vq->notify(&vq->vq);
Rusty Russell0a8a69d2007-10-22 11:03:40 +100096 END_USE(vq);
97 return -ENOSPC;
98 }
99
100 /* We're about to use some buffers from the free list. */
101 vq->num_free -= out + in;
102
103 head = vq->free_head;
104 for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) {
105 vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
Rusty Russell15f9c892008-02-04 23:50:05 -0500106 vq->vring.desc[i].addr = sg_phys(sg);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000107 vq->vring.desc[i].len = sg->length;
108 prev = i;
109 sg++;
110 }
111 for (; in; i = vq->vring.desc[i].next, in--) {
112 vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
Rusty Russell15f9c892008-02-04 23:50:05 -0500113 vq->vring.desc[i].addr = sg_phys(sg);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000114 vq->vring.desc[i].len = sg->length;
115 prev = i;
116 sg++;
117 }
118 /* Last one doesn't continue. */
119 vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;
120
121 /* Update free pointer */
122 vq->free_head = i;
123
124 /* Set token. */
125 vq->data[head] = data;
126
127 /* Put entry in available array (but don't update avail->idx until they
128 * do sync). FIXME: avoid modulus here? */
129 avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num;
130 vq->vring.avail->ring[avail] = head;
131
132 pr_debug("Added buffer head %i to %p\n", head, vq);
133 END_USE(vq);
134 return 0;
135}
136
137static void vring_kick(struct virtqueue *_vq)
138{
139 struct vring_virtqueue *vq = to_vvq(_vq);
140 START_USE(vq);
141 /* Descriptors and available array need to be set before we expose the
142 * new available array entries. */
143 wmb();
144
145 vq->vring.avail->idx += vq->num_added;
146 vq->num_added = 0;
147
148 /* Need to update avail index before checking if we should notify */
149 mb();
150
151 if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
152 /* Prod other side to tell it about changes. */
153 vq->notify(&vq->vq);
154
155 END_USE(vq);
156}
157
158static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
159{
160 unsigned int i;
161
162 /* Clear data ptr. */
163 vq->data[head] = NULL;
164
165 /* Put back on free list: find end */
166 i = head;
167 while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
168 i = vq->vring.desc[i].next;
169 vq->num_free++;
170 }
171
172 vq->vring.desc[i].next = vq->free_head;
173 vq->free_head = head;
174 /* Plus final descriptor */
175 vq->num_free++;
176}
177
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000178static inline bool more_used(const struct vring_virtqueue *vq)
179{
180 return vq->last_used_idx != vq->vring.used->idx;
181}
182
183static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len)
184{
185 struct vring_virtqueue *vq = to_vvq(_vq);
186 void *ret;
187 unsigned int i;
188
189 START_USE(vq);
190
Rusty Russell5ef82752008-05-02 21:50:43 -0500191 if (unlikely(vq->broken)) {
192 END_USE(vq);
193 return NULL;
194 }
195
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000196 if (!more_used(vq)) {
197 pr_debug("No more buffers in queue\n");
198 END_USE(vq);
199 return NULL;
200 }
201
202 i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
203 *len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;
204
205 if (unlikely(i >= vq->vring.num)) {
206 BAD_RING(vq, "id %u out of range\n", i);
207 return NULL;
208 }
209 if (unlikely(!vq->data[i])) {
210 BAD_RING(vq, "id %u is not a head!\n", i);
211 return NULL;
212 }
213
214 /* detach_buf clears data, so grab it now. */
215 ret = vq->data[i];
216 detach_buf(vq, i);
217 vq->last_used_idx++;
218 END_USE(vq);
219 return ret;
220}
221
Rusty Russell18445c42008-02-04 23:49:57 -0500222static void vring_disable_cb(struct virtqueue *_vq)
223{
224 struct vring_virtqueue *vq = to_vvq(_vq);
225
Rusty Russell18445c42008-02-04 23:49:57 -0500226 vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
Rusty Russell18445c42008-02-04 23:49:57 -0500227}
228
229static bool vring_enable_cb(struct virtqueue *_vq)
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000230{
231 struct vring_virtqueue *vq = to_vvq(_vq);
232
233 START_USE(vq);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000234
235 /* We optimistically turn back on interrupts, then check if there was
236 * more to do. */
237 vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
238 mb();
239 if (unlikely(more_used(vq))) {
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000240 END_USE(vq);
241 return false;
242 }
243
244 END_USE(vq);
245 return true;
246}
247
248irqreturn_t vring_interrupt(int irq, void *_vq)
249{
250 struct vring_virtqueue *vq = to_vvq(_vq);
251
252 if (!more_used(vq)) {
253 pr_debug("virtqueue interrupt with no work for %p\n", vq);
254 return IRQ_NONE;
255 }
256
257 if (unlikely(vq->broken))
258 return IRQ_HANDLED;
259
260 pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
Rusty Russell18445c42008-02-04 23:49:57 -0500261 if (vq->vq.callback)
262 vq->vq.callback(&vq->vq);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000263
264 return IRQ_HANDLED;
265}
Rusty Russellc6fd4702008-02-04 23:50:05 -0500266EXPORT_SYMBOL_GPL(vring_interrupt);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000267
268static struct virtqueue_ops vring_vq_ops = {
269 .add_buf = vring_add_buf,
270 .get_buf = vring_get_buf,
271 .kick = vring_kick,
Rusty Russell18445c42008-02-04 23:49:57 -0500272 .disable_cb = vring_disable_cb,
273 .enable_cb = vring_enable_cb,
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000274};
275
276struct virtqueue *vring_new_virtqueue(unsigned int num,
Rusty Russell87c7d572008-12-30 09:26:03 -0600277 unsigned int vring_align,
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000278 struct virtio_device *vdev,
279 void *pages,
280 void (*notify)(struct virtqueue *),
Rusty Russell18445c42008-02-04 23:49:57 -0500281 void (*callback)(struct virtqueue *))
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000282{
283 struct vring_virtqueue *vq;
284 unsigned int i;
285
Rusty Russell42b36cc2007-11-12 13:39:18 +1100286 /* We assume num is a power of 2. */
287 if (num & (num - 1)) {
288 dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
289 return NULL;
290 }
291
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000292 vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
293 if (!vq)
294 return NULL;
295
Rusty Russell87c7d572008-12-30 09:26:03 -0600296 vring_init(&vq->vring, num, pages, vring_align);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000297 vq->vq.callback = callback;
298 vq->vq.vdev = vdev;
299 vq->vq.vq_ops = &vring_vq_ops;
300 vq->notify = notify;
301 vq->broken = false;
302 vq->last_used_idx = 0;
303 vq->num_added = 0;
304#ifdef DEBUG
305 vq->in_use = false;
306#endif
307
308 /* No callback? Tell other side not to bother us. */
309 if (!callback)
310 vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
311
312 /* Put everything in free lists. */
313 vq->num_free = num;
314 vq->free_head = 0;
315 for (i = 0; i < num-1; i++)
316 vq->vring.desc[i].next = i+1;
317
318 return &vq->vq;
319}
Rusty Russellc6fd4702008-02-04 23:50:05 -0500320EXPORT_SYMBOL_GPL(vring_new_virtqueue);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000321
322void vring_del_virtqueue(struct virtqueue *vq)
323{
324 kfree(to_vvq(vq));
325}
Rusty Russellc6fd4702008-02-04 23:50:05 -0500326EXPORT_SYMBOL_GPL(vring_del_virtqueue);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000327
Rusty Russelle34f8722008-07-25 12:06:13 -0500328/* Manipulates transport-specific feature bits. */
329void vring_transport_features(struct virtio_device *vdev)
330{
331 unsigned int i;
332
333 for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
334 switch (i) {
335 default:
336 /* We don't understand this bit. */
337 clear_bit(i, vdev->features);
338 }
339 }
340}
341EXPORT_SYMBOL_GPL(vring_transport_features);
342
Rusty Russellc6fd4702008-02-04 23:50:05 -0500343MODULE_LICENSE("GPL");