[mirror_ubuntu-hirsute-kernel.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/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,
				      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, PAGE_SIZE);
	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);

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