[linux-2.6-block.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)
#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. */
	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
	39	struct 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. */
1bc4953e	57	u16 last_used_idx;
0a8a69dd RR	58
	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
	73	static 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);
44653eae RR	91	/* 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);
0a8a69dd RR	96	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;
15f9c890	106	vq->vring.desc[i].addr = sg_phys(sg);
0a8a69dd RR	107	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;
15f9c890	113	vq->vring.desc[i].addr = sg_phys(sg);
0a8a69dd RR	114	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
	137	static 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
	158	static 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
0a8a69dd RR	178	static inline bool more_used(const struct vring_virtqueue *vq)
	179	{
	180	return vq->last_used_idx != vq->vring.used->idx;
	181	}
	182
	183	static 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
5ef82752 RR	191	if (unlikely(vq->broken)) {
	192	END_USE(vq);
	193	return NULL;
	194	}
	195
0a8a69dd RR	196	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
18445c4d RR	222	static void vring_disable_cb(struct virtqueue *_vq)
	223	{
	224	struct vring_virtqueue *vq = to_vvq(_vq);
	225
18445c4d	226	vq->vring.avail->flags \|= VRING_AVAIL_F_NO_INTERRUPT;
18445c4d RR	227	}
	228
	229	static bool vring_enable_cb(struct virtqueue *_vq)
0a8a69dd RR	230	{
	231	struct vring_virtqueue *vq = to_vvq(_vq);
	232
	233	START_USE(vq);
0a8a69dd RR	234
	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))) {
0a8a69dd RR	240	END_USE(vq);
	241	return false;
	242	}
	243
	244	END_USE(vq);
	245	return true;
	246	}
	247
	248	irqreturn_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);
18445c4d RR	261	if (vq->vq.callback)
18445c4d RR	262	vq->vq.callback(&vq->vq);
0a8a69dd RR	263
	264	return IRQ_HANDLED;
	265	}
c6fd4701	266	EXPORT_SYMBOL_GPL(vring_interrupt);
0a8a69dd RR	267
	268	static struct virtqueue_ops vring_vq_ops = {
	269	.add_buf = vring_add_buf,
	270	.get_buf = vring_get_buf,
	271	.kick = vring_kick,
18445c4d RR	272	.disable_cb = vring_disable_cb,
18445c4d RR	273	.enable_cb = vring_enable_cb,
0a8a69dd RR	274	};
	275
	276	struct virtqueue *vring_new_virtqueue(unsigned int num,
87c7d57c	277	unsigned int vring_align,
0a8a69dd RR	278	struct virtio_device *vdev,
	279	void *pages,
	280	void (notify)(struct virtqueue ),
18445c4d	281	void (callback)(struct virtqueue ))
0a8a69dd RR	282	{
	283	struct vring_virtqueue *vq;
	284	unsigned int i;
	285
42b36cc0 RR	286	/* 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
0a8a69dd RR	292	vq = kmalloc(sizeof(vq) + sizeof(void )*num, GFP_KERNEL);
	293	if (!vq)
	294	return NULL;
	295
87c7d57c	296	vring_init(&vq->vring, num, pages, vring_align);
0a8a69dd RR	297	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	}
c6fd4701	320	EXPORT_SYMBOL_GPL(vring_new_virtqueue);
0a8a69dd RR	321
	322	void vring_del_virtqueue(struct virtqueue *vq)
	323	{
	324	kfree(to_vvq(vq));
	325	}
c6fd4701	326	EXPORT_SYMBOL_GPL(vring_del_virtqueue);
0a8a69dd	327
e34f8725 RR	328	/* Manipulates transport-specific feature bits. */
	329	void 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	}
	341	EXPORT_SYMBOL_GPL(vring_transport_features);
	342
c6fd4701	343	MODULE_LICENSE("GPL");