[net-next-2.6.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, args...)				\
	do {							\
		dev_err(&(_vq)->vq.vdev->dev,			\
			"%s:"fmt, (_vq)->vq.name, ##args);	\
		BUG();						\
	} while (0)
/* Caller is supposed to guarantee no reentry. */
#define START_USE(_vq)						\
	do {							\
		if ((_vq)->in_use)				\
			panic("%s:in_use = %i\n",		\
			      (_vq)->vq.name, (_vq)->in_use);	\
		(_vq)->in_use = __LINE__;			\
	} while (0)
#define END_USE(_vq) \
	do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
#else
#define BAD_RING(_vq, fmt, args...)				\
	do {							\
		dev_err(&_vq->vq.vdev->dev,			\
			"%s:"fmt, (_vq)->vq.name, ##args);	\
		(_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;

	/* Host supports indirect buffers */
	bool indirect;

	/* 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)

/* Set up an indirect table of descriptors and add it to the queue. */
static int vring_add_indirect(struct vring_virtqueue *vq,
			      struct scatterlist sg[],
			      unsigned int out,
			      unsigned int in)
{
	struct vring_desc *desc;
	unsigned head;
	int i;

	desc = kmalloc((out + in) * sizeof(struct vring_desc), GFP_ATOMIC);
	if (!desc)
		return vq->vring.num;

	/* Transfer entries from the sg list into the indirect page */
	for (i = 0; i < out; i++) {
		desc[i].flags = VRING_DESC_F_NEXT;
		desc[i].addr = sg_phys(sg);
		desc[i].len = sg->length;
		desc[i].next = i+1;
		sg++;
	}
	for (; i < (out + in); i++) {
		desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
		desc[i].addr = sg_phys(sg);
		desc[i].len = sg->length;
		desc[i].next = i+1;
		sg++;
	}

	/* Last one doesn't continue. */
	desc[i-1].flags &= ~VRING_DESC_F_NEXT;
	desc[i-1].next = 0;

	/* We're about to use a buffer */
	vq->num_free--;

	/* Use a single buffer which doesn't continue */
	head = vq->free_head;
	vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT;
	vq->vring.desc[head].addr = virt_to_phys(desc);
	vq->vring.desc[head].len = i * sizeof(struct vring_desc);

	/* Update free pointer */
	vq->free_head = vq->vring.desc[head].next;

	return head;
}

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);

	START_USE(vq);

	BUG_ON(data == NULL);

	/* If the host supports indirect descriptor tables, and we have multiple
	 * buffers, then go indirect. FIXME: tune this threshold */
	if (vq->indirect && (out + in) > 1 && vq->num_free) {
		head = vring_add_indirect(vq, sg, out, in);
		if (head != vq->vring.num)
			goto add_head;
	}

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

	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;

add_head:
	/* 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);

	/* If we're indirect, we can fit many (assuming not OOM). */
	if (vq->indirect)
		return vq->num_free ? vq->vring.num : 0;
	return vq->num_free;
}

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;

	/* Free the indirect table */
	if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
		kfree(phys_to_virt(vq->vring.desc[i].addr));

	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;
	}

	/* Only get used array entries after they have been exposed by host. */
	rmb();

	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 *),
				      const char *name)
{
	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->vq.name = name;
	vq->notify = notify;
	vq->broken = false;
	vq->last_used_idx = 0;
	vq->num_added = 0;
	list_add_tail(&vq->vq.list, &vdev->vqs);
#ifdef DEBUG
	vq->in_use = false;
#endif

	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);

	/* 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)
{
	list_del(&vq->list);
	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) {
		case VIRTIO_RING_F_INDIRECT_DESC:
			break;
		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. */
9499f5e7 RR	26	#define BAD_RING(_vq, fmt, args...) \
	27	do { \
	28	dev_err(&(_vq)->vq.vdev->dev, \
	29	"%s:"fmt, (_vq)->vq.name, ##args); \
	30	BUG(); \
	31	} while (0)
c5f841f1 RR	32	/* Caller is supposed to guarantee no reentry. */
	33	#define START_USE(_vq) \
	34	do { \
	35	if ((_vq)->in_use) \
9499f5e7 RR	36	panic("%s:in_use = %i\n", \
9499f5e7 RR	37	(_vq)->vq.name, (_vq)->in_use); \
c5f841f1	38	(_vq)->in_use = __LINE__; \
9499f5e7	39	} while (0)
3a35ce7d	40	#define END_USE(_vq) \
97a545ab	41	do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
0a8a69dd	42	#else
9499f5e7 RR	43	#define BAD_RING(_vq, fmt, args...) \
	44	do { \
	45	dev_err(&_vq->vq.vdev->dev, \
	46	"%s:"fmt, (_vq)->vq.name, ##args); \
	47	(_vq)->broken = true; \
	48	} while (0)
0a8a69dd RR	49	#define START_USE(vq)
	50	#define END_USE(vq)
	51	#endif
	52
	53	struct vring_virtqueue
	54	{
	55	struct virtqueue vq;
	56
	57	/* Actual memory layout for this queue */
	58	struct vring vring;
	59
	60	/* Other side has made a mess, don't try any more. */
	61	bool broken;
	62
9fa29b9d MM	63	/* Host supports indirect buffers */
	64	bool indirect;
	65
0a8a69dd RR	66	/* Number of free buffers */
	67	unsigned int num_free;
	68	/* Head of free buffer list. */
	69	unsigned int free_head;
	70	/* Number we've added since last sync. */
	71	unsigned int num_added;
	72
	73	/* Last used index we've seen. */
1bc4953e	74	u16 last_used_idx;
0a8a69dd RR	75
	76	/* How to notify other side. FIXME: commonalize hcalls! */
	77	void (notify)(struct virtqueue vq);
	78
	79	#ifdef DEBUG
	80	/* They're supposed to lock for us. */
	81	unsigned int in_use;
	82	#endif
	83
	84	/* Tokens for callbacks. */
	85	void *data[];
	86	};
	87
	88	#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
	89
9fa29b9d MM	90	/* Set up an indirect table of descriptors and add it to the queue. */
	91	static int vring_add_indirect(struct vring_virtqueue *vq,
	92	struct scatterlist sg[],
	93	unsigned int out,
	94	unsigned int in)
	95	{
	96	struct vring_desc *desc;
	97	unsigned head;
	98	int i;
	99
	100	desc = kmalloc((out + in) * sizeof(struct vring_desc), GFP_ATOMIC);
	101	if (!desc)
	102	return vq->vring.num;
	103
	104	/* Transfer entries from the sg list into the indirect page */
	105	for (i = 0; i < out; i++) {
	106	desc[i].flags = VRING_DESC_F_NEXT;
	107	desc[i].addr = sg_phys(sg);
	108	desc[i].len = sg->length;
	109	desc[i].next = i+1;
	110	sg++;
	111	}
	112	for (; i < (out + in); i++) {
	113	desc[i].flags = VRING_DESC_F_NEXT\|VRING_DESC_F_WRITE;
	114	desc[i].addr = sg_phys(sg);
	115	desc[i].len = sg->length;
	116	desc[i].next = i+1;
	117	sg++;
	118	}
	119
	120	/* Last one doesn't continue. */
	121	desc[i-1].flags &= ~VRING_DESC_F_NEXT;
	122	desc[i-1].next = 0;
	123
	124	/* We're about to use a buffer */
	125	vq->num_free--;
	126
	127	/* Use a single buffer which doesn't continue */
	128	head = vq->free_head;
	129	vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT;
	130	vq->vring.desc[head].addr = virt_to_phys(desc);
	131	vq->vring.desc[head].len = i * sizeof(struct vring_desc);
	132
	133	/* Update free pointer */
	134	vq->free_head = vq->vring.desc[head].next;
	135
	136	return head;
	137	}
	138
0a8a69dd RR	139	static int vring_add_buf(struct virtqueue *_vq,
	140	struct scatterlist sg[],
	141	unsigned int out,
	142	unsigned int in,
	143	void *data)
	144	{
	145	struct vring_virtqueue *vq = to_vvq(_vq);
	146	unsigned int i, avail, head, uninitialized_var(prev);
	147
9fa29b9d MM	148	START_USE(vq);
9fa29b9d MM	149
0a8a69dd	150	BUG_ON(data == NULL);
9fa29b9d MM	151
	152	/* If the host supports indirect descriptor tables, and we have multiple
	153	* buffers, then go indirect. FIXME: tune this threshold */
	154	if (vq->indirect && (out + in) > 1 && vq->num_free) {
	155	head = vring_add_indirect(vq, sg, out, in);
	156	if (head != vq->vring.num)
	157	goto add_head;
	158	}
	159
0a8a69dd RR	160	BUG_ON(out + in > vq->vring.num);
	161	BUG_ON(out + in == 0);
	162
0a8a69dd RR	163	if (vq->num_free < out + in) {
	164	pr_debug("Can't add buf len %i - avail = %i\n",
	165	out + in, vq->num_free);
44653eae RR	166	/* FIXME: for historical reasons, we force a notify here if
	167	* there are outgoing parts to the buffer. Presumably the
	168	* host should service the ring ASAP. */
	169	if (out)
	170	vq->notify(&vq->vq);
0a8a69dd RR	171	END_USE(vq);
	172	return -ENOSPC;
	173	}
	174
	175	/* We're about to use some buffers from the free list. */
	176	vq->num_free -= out + in;
	177
	178	head = vq->free_head;
	179	for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) {
	180	vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
15f9c890	181	vq->vring.desc[i].addr = sg_phys(sg);
0a8a69dd RR	182	vq->vring.desc[i].len = sg->length;
	183	prev = i;
	184	sg++;
	185	}
	186	for (; in; i = vq->vring.desc[i].next, in--) {
	187	vq->vring.desc[i].flags = VRING_DESC_F_NEXT\|VRING_DESC_F_WRITE;
15f9c890	188	vq->vring.desc[i].addr = sg_phys(sg);
0a8a69dd RR	189	vq->vring.desc[i].len = sg->length;
	190	prev = i;
	191	sg++;
	192	}
	193	/* Last one doesn't continue. */
	194	vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;
	195
	196	/* Update free pointer */
	197	vq->free_head = i;
	198
9fa29b9d	199	add_head:
0a8a69dd RR	200	/* Set token. */
	201	vq->data[head] = data;
	202
	203	/* Put entry in available array (but don't update avail->idx until they
	204	* do sync). FIXME: avoid modulus here? */
	205	avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num;
	206	vq->vring.avail->ring[avail] = head;
	207
	208	pr_debug("Added buffer head %i to %p\n", head, vq);
	209	END_USE(vq);
3c1b27d5 RR	210
	211	/* If we're indirect, we can fit many (assuming not OOM). */
	212	if (vq->indirect)
	213	return vq->num_free ? vq->vring.num : 0;
	214	return vq->num_free;
0a8a69dd RR	215	}
	216
	217	static void vring_kick(struct virtqueue *_vq)
	218	{
	219	struct vring_virtqueue *vq = to_vvq(_vq);
	220	START_USE(vq);
	221	/* Descriptors and available array need to be set before we expose the
	222	* new available array entries. */
	223	wmb();
	224
	225	vq->vring.avail->idx += vq->num_added;
	226	vq->num_added = 0;
	227
	228	/* Need to update avail index before checking if we should notify */
	229	mb();
	230
	231	if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
	232	/* Prod other side to tell it about changes. */
	233	vq->notify(&vq->vq);
	234
	235	END_USE(vq);
	236	}
	237
	238	static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
	239	{
	240	unsigned int i;
	241
	242	/* Clear data ptr. */
	243	vq->data[head] = NULL;
	244
	245	/* Put back on free list: find end */
	246	i = head;
9fa29b9d MM	247
	248	/* Free the indirect table */
	249	if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
	250	kfree(phys_to_virt(vq->vring.desc[i].addr));
	251
0a8a69dd RR	252	while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
	253	i = vq->vring.desc[i].next;
	254	vq->num_free++;
	255	}
	256
	257	vq->vring.desc[i].next = vq->free_head;
	258	vq->free_head = head;
	259	/* Plus final descriptor */
	260	vq->num_free++;
	261	}
	262
0a8a69dd RR	263	static inline bool more_used(const struct vring_virtqueue *vq)
	264	{
	265	return vq->last_used_idx != vq->vring.used->idx;
	266	}
	267
	268	static void vring_get_buf(struct virtqueue _vq, unsigned int *len)
	269	{
	270	struct vring_virtqueue *vq = to_vvq(_vq);
	271	void *ret;
	272	unsigned int i;
	273
	274	START_USE(vq);
	275
5ef82752 RR	276	if (unlikely(vq->broken)) {
	277	END_USE(vq);
	278	return NULL;
	279	}
	280
0a8a69dd RR	281	if (!more_used(vq)) {
	282	pr_debug("No more buffers in queue\n");
	283	END_USE(vq);
	284	return NULL;
	285	}
	286
2d61ba95 MT	287	/* Only get used array entries after they have been exposed by host. */
	288	rmb();
	289
0a8a69dd RR	290	i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
	291	*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;
	292
	293	if (unlikely(i >= vq->vring.num)) {
	294	BAD_RING(vq, "id %u out of range\n", i);
	295	return NULL;
	296	}
	297	if (unlikely(!vq->data[i])) {
	298	BAD_RING(vq, "id %u is not a head!\n", i);
	299	return NULL;
	300	}
	301
	302	/* detach_buf clears data, so grab it now. */
	303	ret = vq->data[i];
	304	detach_buf(vq, i);
	305	vq->last_used_idx++;
	306	END_USE(vq);
	307	return ret;
	308	}
	309
18445c4d RR	310	static void vring_disable_cb(struct virtqueue *_vq)
	311	{
	312	struct vring_virtqueue *vq = to_vvq(_vq);
	313
18445c4d	314	vq->vring.avail->flags \|= VRING_AVAIL_F_NO_INTERRUPT;
18445c4d RR	315	}
	316
	317	static bool vring_enable_cb(struct virtqueue *_vq)
0a8a69dd RR	318	{
	319	struct vring_virtqueue *vq = to_vvq(_vq);
	320
	321	START_USE(vq);
0a8a69dd RR	322
	323	/* We optimistically turn back on interrupts, then check if there was
	324	* more to do. */
	325	vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
	326	mb();
	327	if (unlikely(more_used(vq))) {
0a8a69dd RR	328	END_USE(vq);
	329	return false;
	330	}
	331
	332	END_USE(vq);
	333	return true;
	334	}
	335
	336	irqreturn_t vring_interrupt(int irq, void *_vq)
	337	{
	338	struct vring_virtqueue *vq = to_vvq(_vq);
	339
	340	if (!more_used(vq)) {
	341	pr_debug("virtqueue interrupt with no work for %p\n", vq);
	342	return IRQ_NONE;
	343	}
	344
	345	if (unlikely(vq->broken))
	346	return IRQ_HANDLED;
	347
	348	pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
18445c4d RR	349	if (vq->vq.callback)
18445c4d RR	350	vq->vq.callback(&vq->vq);
0a8a69dd RR	351
	352	return IRQ_HANDLED;
	353	}
c6fd4701	354	EXPORT_SYMBOL_GPL(vring_interrupt);
0a8a69dd RR	355
	356	static struct virtqueue_ops vring_vq_ops = {
	357	.add_buf = vring_add_buf,
	358	.get_buf = vring_get_buf,
	359	.kick = vring_kick,
18445c4d RR	360	.disable_cb = vring_disable_cb,
18445c4d RR	361	.enable_cb = vring_enable_cb,
0a8a69dd RR	362	};
	363
	364	struct virtqueue *vring_new_virtqueue(unsigned int num,
87c7d57c	365	unsigned int vring_align,
0a8a69dd RR	366	struct virtio_device *vdev,
	367	void *pages,
	368	void (notify)(struct virtqueue ),
9499f5e7 RR	369	void (callback)(struct virtqueue ),
9499f5e7 RR	370	const char *name)
0a8a69dd RR	371	{
	372	struct vring_virtqueue *vq;
	373	unsigned int i;
	374
42b36cc0 RR	375	/* We assume num is a power of 2. */
	376	if (num & (num - 1)) {
	377	dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
	378	return NULL;
	379	}
	380
0a8a69dd RR	381	vq = kmalloc(sizeof(vq) + sizeof(void )*num, GFP_KERNEL);
	382	if (!vq)
	383	return NULL;
	384
87c7d57c	385	vring_init(&vq->vring, num, pages, vring_align);
0a8a69dd RR	386	vq->vq.callback = callback;
	387	vq->vq.vdev = vdev;
	388	vq->vq.vq_ops = &vring_vq_ops;
9499f5e7	389	vq->vq.name = name;
0a8a69dd RR	390	vq->notify = notify;
	391	vq->broken = false;
	392	vq->last_used_idx = 0;
	393	vq->num_added = 0;
9499f5e7	394	list_add_tail(&vq->vq.list, &vdev->vqs);
0a8a69dd RR	395	#ifdef DEBUG
	396	vq->in_use = false;
	397	#endif
	398
9fa29b9d MM	399	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
9fa29b9d MM	400
0a8a69dd RR	401	/* No callback? Tell other side not to bother us. */
	402	if (!callback)
	403	vq->vring.avail->flags \|= VRING_AVAIL_F_NO_INTERRUPT;
	404
	405	/* Put everything in free lists. */
	406	vq->num_free = num;
	407	vq->free_head = 0;
	408	for (i = 0; i < num-1; i++)
	409	vq->vring.desc[i].next = i+1;
	410
	411	return &vq->vq;
	412	}
c6fd4701	413	EXPORT_SYMBOL_GPL(vring_new_virtqueue);
0a8a69dd RR	414
	415	void vring_del_virtqueue(struct virtqueue *vq)
	416	{
9499f5e7	417	list_del(&vq->list);
0a8a69dd RR	418	kfree(to_vvq(vq));
0a8a69dd RR	419	}
c6fd4701	420	EXPORT_SYMBOL_GPL(vring_del_virtqueue);
0a8a69dd	421
e34f8725 RR	422	/* Manipulates transport-specific feature bits. */
	423	void vring_transport_features(struct virtio_device *vdev)
	424	{
	425	unsigned int i;
	426
	427	for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
	428	switch (i) {
9fa29b9d MM	429	case VIRTIO_RING_F_INDIRECT_DESC:
9fa29b9d MM	430	break;
e34f8725 RR	431	default:
	432	/* We don't understand this bit. */
	433	clear_bit(i, vdev->features);
	434	}
	435	}
	436	}
	437	EXPORT_SYMBOL_GPL(vring_transport_features);
	438
c6fd4701	439	MODULE_LICENSE("GPL");