[deliverable/linux.git] / drivers / virtio / virtio_ring.c

/* Virtio ring implementation.
 *
 *  Copyright 2007 Rusty Russell IBM Corporation
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include <linux/virtio.h>
#include <linux/virtio_ring.h>
#include <linux/virtio_config.h>
#include <linux/device.h>

#ifdef DEBUG
/* For development, we want to crash whenever the ring is screwed. */
#define BAD_RING(_vq, fmt...)			\
	do { dev_err(&(_vq)->vq.vdev->dev, fmt); BUG(); } while(0)
/* Caller is supposed to guarantee no reentry. */
#define START_USE(_vq)						\
	do {							\
		if ((_vq)->in_use)				\
			panic("in_use = %i\n", (_vq)->in_use);	\
		(_vq)->in_use = __LINE__;			\
		mb();						\
	} while(0)
#define END_USE(_vq) \
	do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; mb(); } while(0)
#else
#define BAD_RING(_vq, fmt...)			\
	do { dev_err(&_vq->vq.vdev->dev, fmt); (_vq)->broken = true; } while(0)
#define START_USE(vq)
#define END_USE(vq)
#endif

struct vring_virtqueue
{
	struct virtqueue vq;

	/* Actual memory layout for this queue */
	struct vring vring;

	/* Other side has made a mess, don't try any more. */
	bool broken;

	/* Number of free buffers */
	unsigned int num_free;
	/* Head of free buffer list. */
	unsigned int free_head;
	/* Number we've added since last sync. */
	unsigned int num_added;

	/* Last used index we've seen. */
	u16 last_used_idx;

	/* How to notify other side. FIXME: commonalize hcalls! */
	void (*notify)(struct virtqueue *vq);

#ifdef DEBUG
	/* They're supposed to lock for us. */
	unsigned int in_use;
#endif

	/* Tokens for callbacks. */
	void *data[];
};

#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)

static int vring_add_buf(struct virtqueue *_vq,
			 struct scatterlist sg[],
			 unsigned int out,
			 unsigned int in,
			 void *data)
{
	struct vring_virtqueue *vq = to_vvq(_vq);
	unsigned int i, avail, head, uninitialized_var(prev);

	BUG_ON(data == NULL);
	BUG_ON(out + in > vq->vring.num);
	BUG_ON(out + in == 0);

	START_USE(vq);

	if (vq->num_free < out + in) {
		pr_debug("Can't add buf len %i - avail = %i\n",
			 out + in, vq->num_free);
		/* FIXME: for historical reasons, we force a notify here if
		 * there are outgoing parts to the buffer.  Presumably the
		 * host should service the ring ASAP. */
		if (out)
			vq->notify(&vq->vq);
		END_USE(vq);
		return -ENOSPC;
	}

	/* We're about to use some buffers from the free list. */
	vq->num_free -= out + in;

	head = vq->free_head;
	for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) {
		vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
		vq->vring.desc[i].addr = sg_phys(sg);
		vq->vring.desc[i].len = sg->length;
		prev = i;
		sg++;
	}
	for (; in; i = vq->vring.desc[i].next, in--) {
		vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
		vq->vring.desc[i].addr = sg_phys(sg);
		vq->vring.desc[i].len = sg->length;
		prev = i;
		sg++;
	}
	/* Last one doesn't continue. */
	vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;

	/* Update free pointer */
	vq->free_head = i;

	/* Set token. */
	vq->data[head] = data;

	/* Put entry in available array (but don't update avail->idx until they
	 * do sync).  FIXME: avoid modulus here? */
	avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num;
	vq->vring.avail->ring[avail] = head;

	pr_debug("Added buffer head %i to %p\n", head, vq);
	END_USE(vq);
	return 0;
}

static void vring_kick(struct virtqueue *_vq)
{
	struct vring_virtqueue *vq = to_vvq(_vq);
	START_USE(vq);
	/* Descriptors and available array need to be set before we expose the
	 * new available array entries. */
	wmb();

	vq->vring.avail->idx += vq->num_added;
	vq->num_added = 0;

	/* Need to update avail index before checking if we should notify */
	mb();

	if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
		/* Prod other side to tell it about changes. */
		vq->notify(&vq->vq);

	END_USE(vq);
}

static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
{
	unsigned int i;

	/* Clear data ptr. */
	vq->data[head] = NULL;

	/* Put back on free list: find end */
	i = head;
	while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
		i = vq->vring.desc[i].next;
		vq->num_free++;
	}

	vq->vring.desc[i].next = vq->free_head;
	vq->free_head = head;
	/* Plus final descriptor */
	vq->num_free++;
}

static inline bool more_used(const struct vring_virtqueue *vq)
{
	return vq->last_used_idx != vq->vring.used->idx;
}

static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len)
{
	struct vring_virtqueue *vq = to_vvq(_vq);
	void *ret;
	unsigned int i;

	START_USE(vq);

	if (unlikely(vq->broken)) {
		END_USE(vq);
		return NULL;
	}

	if (!more_used(vq)) {
		pr_debug("No more buffers in queue\n");
		END_USE(vq);
		return NULL;
	}

	i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
	*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;

	if (unlikely(i >= vq->vring.num)) {
		BAD_RING(vq, "id %u out of range\n", i);
		return NULL;
	}
	if (unlikely(!vq->data[i])) {
		BAD_RING(vq, "id %u is not a head!\n", i);
		return NULL;
	}

	/* detach_buf clears data, so grab it now. */
	ret = vq->data[i];
	detach_buf(vq, i);
	vq->last_used_idx++;
	END_USE(vq);
	return ret;
}

static void vring_disable_cb(struct virtqueue *_vq)
{
	struct vring_virtqueue *vq = to_vvq(_vq);

	vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
}

static bool vring_enable_cb(struct virtqueue *_vq)
{
	struct vring_virtqueue *vq = to_vvq(_vq);

	START_USE(vq);

	/* We optimistically turn back on interrupts, then check if there was
	 * more to do. */
	vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
	mb();
	if (unlikely(more_used(vq))) {
		END_USE(vq);
		return false;
	}

	END_USE(vq);
	return true;
}

irqreturn_t vring_interrupt(int irq, void *_vq)
{
	struct vring_virtqueue *vq = to_vvq(_vq);

	if (!more_used(vq)) {
		pr_debug("virtqueue interrupt with no work for %p\n", vq);
		return IRQ_NONE;
	}

	if (unlikely(vq->broken))
		return IRQ_HANDLED;

	pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
	if (vq->vq.callback)
		vq->vq.callback(&vq->vq);

	return IRQ_HANDLED;
}
EXPORT_SYMBOL_GPL(vring_interrupt);

static struct virtqueue_ops vring_vq_ops = {
	.add_buf = vring_add_buf,
	.get_buf = vring_get_buf,
	.kick = vring_kick,
	.disable_cb = vring_disable_cb,
	.enable_cb = vring_enable_cb,
};

struct virtqueue *vring_new_virtqueue(unsigned int num,
				      unsigned int vring_align,
				      struct virtio_device *vdev,
				      void *pages,
				      void (*notify)(struct virtqueue *),
				      void (*callback)(struct virtqueue *))
{
	struct vring_virtqueue *vq;
	unsigned int i;

	/* We assume num is a power of 2. */
	if (num & (num - 1)) {
		dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
		return NULL;
	}

	vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
	if (!vq)
		return NULL;

	vring_init(&vq->vring, num, pages, vring_align);
	vq->vq.callback = callback;
	vq->vq.vdev = vdev;
	vq->vq.vq_ops = &vring_vq_ops;
	vq->notify = notify;
	vq->broken = false;
	vq->last_used_idx = 0;
	vq->num_added = 0;
#ifdef DEBUG
	vq->in_use = false;
#endif

	/* No callback?  Tell other side not to bother us. */
	if (!callback)
		vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;

	/* Put everything in free lists. */
	vq->num_free = num;
	vq->free_head = 0;
	for (i = 0; i < num-1; i++)
		vq->vring.desc[i].next = i+1;

	return &vq->vq;
}
EXPORT_SYMBOL_GPL(vring_new_virtqueue);

void vring_del_virtqueue(struct virtqueue *vq)
{
	kfree(to_vvq(vq));
}
EXPORT_SYMBOL_GPL(vring_del_virtqueue);

/* Manipulates transport-specific feature bits. */
void vring_transport_features(struct virtio_device *vdev)
{
	unsigned int i;

	for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
		switch (i) {
		default:
			/* We don't understand this bit. */
			clear_bit(i, vdev->features);
		}
	}
}
EXPORT_SYMBOL_GPL(vring_transport_features);

MODULE_LICENSE("GPL");
Commit	Line	Data
0a8a69dd RR	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>
e34f8725	21	#include <linux/virtio_config.h>
0a8a69dd RR	22	#include <linux/device.h>
	23
	24	#ifdef DEBUG
	25	/* For development, we want to crash whenever the ring is screwed. */
3a35ce7d	26	#define BAD_RING(_vq, fmt...) \
c5f841f1 RR	27	do { dev_err(&(_vq)->vq.vdev->dev, fmt); BUG(); } while(0)
	28	/* Caller is supposed to guarantee no reentry. */
	29	#define START_USE(_vq) \
	30	do { \
	31	if ((_vq)->in_use) \
	32	panic("in_use = %i\n", (_vq)->in_use); \
	33	(_vq)->in_use = __LINE__; \
	34	mb(); \
	35	} while(0)
3a35ce7d RK	36	#define END_USE(_vq) \
3a35ce7d RK	37	do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; mb(); } while(0)
0a8a69dd	38	#else
3a35ce7d RK	39	#define BAD_RING(_vq, fmt...) \
3a35ce7d RK	40	do { dev_err(&_vq->vq.vdev->dev, fmt); (_vq)->broken = true; } while(0)
0a8a69dd RR	41	#define START_USE(vq)
	42	#define END_USE(vq)
	43	#endif
	44
	45	struct vring_virtqueue
	46	{
	47	struct virtqueue vq;
	48
	49	/* Actual memory layout for this queue */
	50	struct vring vring;
	51
	52	/* Other side has made a mess, don't try any more. */
	53	bool broken;
	54
	55	/* Number of free buffers */
	56	unsigned int num_free;
	57	/* Head of free buffer list. */
	58	unsigned int free_head;
	59	/* Number we've added since last sync. */
	60	unsigned int num_added;
	61
	62	/* Last used index we've seen. */
1bc4953e	63	u16 last_used_idx;
0a8a69dd RR	64
	65	/* How to notify other side. FIXME: commonalize hcalls! */
	66	void (notify)(struct virtqueue vq);
	67
	68	#ifdef DEBUG
	69	/* They're supposed to lock for us. */
	70	unsigned int in_use;
	71	#endif
	72
	73	/* Tokens for callbacks. */
	74	void *data[];
	75	};
	76
	77	#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
	78
	79	static int vring_add_buf(struct virtqueue *_vq,
	80	struct scatterlist sg[],
	81	unsigned int out,
	82	unsigned int in,
	83	void *data)
	84	{
	85	struct vring_virtqueue *vq = to_vvq(_vq);
	86	unsigned int i, avail, head, uninitialized_var(prev);
	87
	88	BUG_ON(data == NULL);
	89	BUG_ON(out + in > vq->vring.num);
	90	BUG_ON(out + in == 0);
	91
	92	START_USE(vq);
	93
	94	if (vq->num_free < out + in) {
	95	pr_debug("Can't add buf len %i - avail = %i\n",
	96	out + in, vq->num_free);
44653eae RR	97	/* FIXME: for historical reasons, we force a notify here if
	98	* there are outgoing parts to the buffer. Presumably the
	99	* host should service the ring ASAP. */
	100	if (out)
	101	vq->notify(&vq->vq);
0a8a69dd RR	102	END_USE(vq);
	103	return -ENOSPC;
	104	}
	105
	106	/* We're about to use some buffers from the free list. */
	107	vq->num_free -= out + in;
	108
	109	head = vq->free_head;
	110	for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) {
	111	vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
15f9c890	112	vq->vring.desc[i].addr = sg_phys(sg);
0a8a69dd RR	113	vq->vring.desc[i].len = sg->length;
	114	prev = i;
	115	sg++;
	116	}
	117	for (; in; i = vq->vring.desc[i].next, in--) {
	118	vq->vring.desc[i].flags = VRING_DESC_F_NEXT\|VRING_DESC_F_WRITE;
15f9c890	119	vq->vring.desc[i].addr = sg_phys(sg);
0a8a69dd RR	120	vq->vring.desc[i].len = sg->length;
	121	prev = i;
	122	sg++;
	123	}
	124	/* Last one doesn't continue. */
	125	vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;
	126
	127	/* Update free pointer */
	128	vq->free_head = i;
	129
	130	/* Set token. */
	131	vq->data[head] = data;
	132
	133	/* Put entry in available array (but don't update avail->idx until they
	134	* do sync). FIXME: avoid modulus here? */
	135	avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num;
	136	vq->vring.avail->ring[avail] = head;
	137
	138	pr_debug("Added buffer head %i to %p\n", head, vq);
	139	END_USE(vq);
	140	return 0;
	141	}
	142
	143	static void vring_kick(struct virtqueue *_vq)
	144	{
	145	struct vring_virtqueue *vq = to_vvq(_vq);
	146	START_USE(vq);
	147	/* Descriptors and available array need to be set before we expose the
	148	* new available array entries. */
	149	wmb();
	150
	151	vq->vring.avail->idx += vq->num_added;
	152	vq->num_added = 0;
	153
	154	/* Need to update avail index before checking if we should notify */
	155	mb();
	156
	157	if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
	158	/* Prod other side to tell it about changes. */
	159	vq->notify(&vq->vq);
	160
	161	END_USE(vq);
	162	}
	163
	164	static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
	165	{
	166	unsigned int i;
	167
	168	/* Clear data ptr. */
	169	vq->data[head] = NULL;
	170
	171	/* Put back on free list: find end */
	172	i = head;
	173	while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
	174	i = vq->vring.desc[i].next;
	175	vq->num_free++;
	176	}
	177
	178	vq->vring.desc[i].next = vq->free_head;
	179	vq->free_head = head;
	180	/* Plus final descriptor */
	181	vq->num_free++;
	182	}
	183
0a8a69dd RR	184	static inline bool more_used(const struct vring_virtqueue *vq)
	185	{
	186	return vq->last_used_idx != vq->vring.used->idx;
	187	}
	188
	189	static void vring_get_buf(struct virtqueue _vq, unsigned int *len)
	190	{
	191	struct vring_virtqueue *vq = to_vvq(_vq);
	192	void *ret;
	193	unsigned int i;
	194
	195	START_USE(vq);
	196
5ef82752 RR	197	if (unlikely(vq->broken)) {
	198	END_USE(vq);
	199	return NULL;
	200	}
	201
0a8a69dd RR	202	if (!more_used(vq)) {
	203	pr_debug("No more buffers in queue\n");
	204	END_USE(vq);
	205	return NULL;
	206	}
	207
	208	i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
	209	*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;
	210
	211	if (unlikely(i >= vq->vring.num)) {
	212	BAD_RING(vq, "id %u out of range\n", i);
	213	return NULL;
	214	}
	215	if (unlikely(!vq->data[i])) {
	216	BAD_RING(vq, "id %u is not a head!\n", i);
	217	return NULL;
	218	}
	219
	220	/* detach_buf clears data, so grab it now. */
	221	ret = vq->data[i];
	222	detach_buf(vq, i);
	223	vq->last_used_idx++;
	224	END_USE(vq);
	225	return ret;
	226	}
	227
18445c4d RR	228	static void vring_disable_cb(struct virtqueue *_vq)
	229	{
	230	struct vring_virtqueue *vq = to_vvq(_vq);
	231
18445c4d	232	vq->vring.avail->flags \|= VRING_AVAIL_F_NO_INTERRUPT;
18445c4d RR	233	}
	234
	235	static bool vring_enable_cb(struct virtqueue *_vq)
0a8a69dd RR	236	{
	237	struct vring_virtqueue *vq = to_vvq(_vq);
	238
	239	START_USE(vq);
0a8a69dd RR	240
	241	/* We optimistically turn back on interrupts, then check if there was
	242	* more to do. */
	243	vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
	244	mb();
	245	if (unlikely(more_used(vq))) {
0a8a69dd RR	246	END_USE(vq);
	247	return false;
	248	}
	249
	250	END_USE(vq);
	251	return true;
	252	}
	253
	254	irqreturn_t vring_interrupt(int irq, void *_vq)
	255	{
	256	struct vring_virtqueue *vq = to_vvq(_vq);
	257
	258	if (!more_used(vq)) {
	259	pr_debug("virtqueue interrupt with no work for %p\n", vq);
	260	return IRQ_NONE;
	261	}
	262
	263	if (unlikely(vq->broken))
	264	return IRQ_HANDLED;
	265
	266	pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
18445c4d RR	267	if (vq->vq.callback)
18445c4d RR	268	vq->vq.callback(&vq->vq);
0a8a69dd RR	269
	270	return IRQ_HANDLED;
	271	}
c6fd4701	272	EXPORT_SYMBOL_GPL(vring_interrupt);
0a8a69dd RR	273
	274	static struct virtqueue_ops vring_vq_ops = {
	275	.add_buf = vring_add_buf,
	276	.get_buf = vring_get_buf,
	277	.kick = vring_kick,
18445c4d RR	278	.disable_cb = vring_disable_cb,
18445c4d RR	279	.enable_cb = vring_enable_cb,
0a8a69dd RR	280	};
	281
	282	struct virtqueue *vring_new_virtqueue(unsigned int num,
87c7d57c	283	unsigned int vring_align,
0a8a69dd RR	284	struct virtio_device *vdev,
	285	void *pages,
	286	void (notify)(struct virtqueue ),
18445c4d	287	void (callback)(struct virtqueue ))
0a8a69dd RR	288	{
	289	struct vring_virtqueue *vq;
	290	unsigned int i;
	291
42b36cc0 RR	292	/* We assume num is a power of 2. */
	293	if (num & (num - 1)) {
	294	dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
	295	return NULL;
	296	}
	297
0a8a69dd RR	298	vq = kmalloc(sizeof(vq) + sizeof(void )*num, GFP_KERNEL);
	299	if (!vq)
	300	return NULL;
	301
87c7d57c	302	vring_init(&vq->vring, num, pages, vring_align);
0a8a69dd RR	303	vq->vq.callback = callback;
	304	vq->vq.vdev = vdev;
	305	vq->vq.vq_ops = &vring_vq_ops;
	306	vq->notify = notify;
	307	vq->broken = false;
	308	vq->last_used_idx = 0;
	309	vq->num_added = 0;
	310	#ifdef DEBUG
	311	vq->in_use = false;
	312	#endif
	313
	314	/* No callback? Tell other side not to bother us. */
	315	if (!callback)
	316	vq->vring.avail->flags \|= VRING_AVAIL_F_NO_INTERRUPT;
	317
	318	/* Put everything in free lists. */
	319	vq->num_free = num;
	320	vq->free_head = 0;
	321	for (i = 0; i < num-1; i++)
	322	vq->vring.desc[i].next = i+1;
	323
	324	return &vq->vq;
	325	}
c6fd4701	326	EXPORT_SYMBOL_GPL(vring_new_virtqueue);
0a8a69dd RR	327
	328	void vring_del_virtqueue(struct virtqueue *vq)
	329	{
	330	kfree(to_vvq(vq));
	331	}
c6fd4701	332	EXPORT_SYMBOL_GPL(vring_del_virtqueue);
0a8a69dd	333
e34f8725 RR	334	/* Manipulates transport-specific feature bits. */
	335	void vring_transport_features(struct virtio_device *vdev)
	336	{
	337	unsigned int i;
	338
	339	for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
	340	switch (i) {
	341	default:
	342	/* We don't understand this bit. */
	343	clear_bit(i, vdev->features);
	344	}
	345	}
	346	}
	347	EXPORT_SYMBOL_GPL(vring_transport_features);
	348
c6fd4701	349	MODULE_LICENSE("GPL");