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yaml
---
r: 256497
b: refs/heads/master
c: bab632d
h: refs/heads/master
i:
  256495: ab526d2
v: v3
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Michael S. Tsirkin authored and David S. Miller committed Jul 18, 2011
1 parent 5131751 commit 4281164
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Showing 4 changed files with 221 additions and 17 deletions.
2 changes: 1 addition & 1 deletion [refs]
View file
Original file line number Diff line number Diff line change
@@ -1,2 +1,2 @@
---
refs/heads/master: 5c74501f76360ce6f410730b9b5e5976f38e8504
refs/heads/master: bab632d69ee48a106e779b60cc01adfe80a72807
77 changes: 76 additions & 1 deletion trunk/drivers/vhost/net.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
#include <linux/virtio_net.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/mutex.h>
#include <linux/workqueue.h>
#include <linux/rcupdate.h>
Expand All @@ -28,10 +29,18 @@

#include "vhost.h"

static int experimental_zcopytx;
module_param(experimental_zcopytx, int, 0444);
MODULE_PARM_DESC(experimental_zcopytx, "Enable Experimental Zero Copy TX");

/* Max number of bytes transferred before requeueing the job.
* Using this limit prevents one virtqueue from starving others. */
#define VHOST_NET_WEIGHT 0x80000

/* MAX number of TX used buffers for outstanding zerocopy */
#define VHOST_MAX_PEND 128
#define VHOST_GOODCOPY_LEN 256

enum {
VHOST_NET_VQ_RX = 0,
VHOST_NET_VQ_TX = 1,
Expand All @@ -54,6 +63,12 @@ struct vhost_net {
enum vhost_net_poll_state tx_poll_state;
};

static bool vhost_sock_zcopy(struct socket *sock)
{
return unlikely(experimental_zcopytx) &&
sock_flag(sock->sk, SOCK_ZEROCOPY);
}

/* Pop first len bytes from iovec. Return number of segments used. */
static int move_iovec_hdr(struct iovec *from, struct iovec *to,
size_t len, int iov_count)
Expand Down Expand Up @@ -129,6 +144,8 @@ static void handle_tx(struct vhost_net *net)
int err, wmem;
size_t hdr_size;
struct socket *sock;
struct vhost_ubuf_ref *uninitialized_var(ubufs);
bool zcopy;

/* TODO: check that we are running from vhost_worker? */
sock = rcu_dereference_check(vq->private_data, 1);
Expand All @@ -149,8 +166,13 @@ static void handle_tx(struct vhost_net *net)
if (wmem < sock->sk->sk_sndbuf / 2)
tx_poll_stop(net);
hdr_size = vq->vhost_hlen;
zcopy = vhost_sock_zcopy(sock);

for (;;) {
/* Release DMAs done buffers first */
if (zcopy)
vhost_zerocopy_signal_used(vq);

head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
ARRAY_SIZE(vq->iov),
&out, &in,
Expand All @@ -166,6 +188,13 @@ static void handle_tx(struct vhost_net *net)
set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
break;
}
/* If more outstanding DMAs, queue the work */
if (unlikely(vq->upend_idx - vq->done_idx >
VHOST_MAX_PEND)) {
tx_poll_start(net, sock);
set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
break;
}
if (unlikely(vhost_enable_notify(&net->dev, vq))) {
vhost_disable_notify(&net->dev, vq);
continue;
Expand All @@ -188,17 +217,48 @@ static void handle_tx(struct vhost_net *net)
iov_length(vq->hdr, s), hdr_size);
break;
}
/* use msg_control to pass vhost zerocopy ubuf info to skb */
if (zcopy) {
vq->heads[vq->upend_idx].id = head;
if (len < VHOST_GOODCOPY_LEN) {
/* copy don't need to wait for DMA done */
vq->heads[vq->upend_idx].len =
VHOST_DMA_DONE_LEN;
msg.msg_control = NULL;
msg.msg_controllen = 0;
ubufs = NULL;
} else {
struct ubuf_info *ubuf = &vq->ubuf_info[head];

vq->heads[vq->upend_idx].len = len;
ubuf->callback = vhost_zerocopy_callback;
ubuf->arg = vq->ubufs;
ubuf->desc = vq->upend_idx;
msg.msg_control = ubuf;
msg.msg_controllen = sizeof(ubuf);
ubufs = vq->ubufs;
kref_get(&ubufs->kref);
}
vq->upend_idx = (vq->upend_idx + 1) % UIO_MAXIOV;
}
/* TODO: Check specific error and bomb out unless ENOBUFS? */
err = sock->ops->sendmsg(NULL, sock, &msg, len);
if (unlikely(err < 0)) {
if (zcopy) {
if (ubufs)
vhost_ubuf_put(ubufs);
vq->upend_idx = ((unsigned)vq->upend_idx - 1) %
UIO_MAXIOV;
}
vhost_discard_vq_desc(vq, 1);
tx_poll_start(net, sock);
break;
}
if (err != len)
pr_debug("Truncated TX packet: "
" len %d != %zd\n", err, len);
vhost_add_used_and_signal(&net->dev, vq, head, 0);
if (!zcopy)
vhost_add_used_and_signal(&net->dev, vq, head, 0);
total_len += len;
if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
vhost_poll_queue(&vq->poll);
Expand Down Expand Up @@ -603,6 +663,7 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
{
struct socket *sock, *oldsock;
struct vhost_virtqueue *vq;
struct vhost_ubuf_ref *ubufs, *oldubufs = NULL;
int r;

mutex_lock(&n->dev.mutex);
Expand Down Expand Up @@ -632,13 +693,23 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
oldsock = rcu_dereference_protected(vq->private_data,
lockdep_is_held(&vq->mutex));
if (sock != oldsock) {
ubufs = vhost_ubuf_alloc(vq, sock && vhost_sock_zcopy(sock));
if (IS_ERR(ubufs)) {
r = PTR_ERR(ubufs);
goto err_ubufs;
}
oldubufs = vq->ubufs;
vq->ubufs = ubufs;
vhost_net_disable_vq(n, vq);
rcu_assign_pointer(vq->private_data, sock);
vhost_net_enable_vq(n, vq);
}

mutex_unlock(&vq->mutex);

if (oldubufs)
vhost_ubuf_put_and_wait(oldubufs);

if (oldsock) {
vhost_net_flush_vq(n, index);
fput(oldsock->file);
Expand All @@ -647,6 +718,8 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
mutex_unlock(&n->dev.mutex);
return 0;

err_ubufs:
fput(sock->file);
err_vq:
mutex_unlock(&vq->mutex);
err:
Expand Down Expand Up @@ -776,6 +849,8 @@ static struct miscdevice vhost_net_misc = {

static int vhost_net_init(void)
{
if (experimental_zcopytx)
vhost_enable_zcopy(VHOST_NET_VQ_TX);
return misc_register(&vhost_net_misc);
}
module_init(vhost_net_init);
Expand Down
128 changes: 113 additions & 15 deletions trunk/drivers/vhost/vhost.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,8 @@ enum {
VHOST_MEMORY_F_LOG = 0x1,
};

static unsigned vhost_zcopy_mask __read_mostly;

#define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
#define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])

Expand Down Expand Up @@ -179,6 +181,9 @@ static void vhost_vq_reset(struct vhost_dev *dev,
vq->call_ctx = NULL;
vq->call = NULL;
vq->log_ctx = NULL;
vq->upend_idx = 0;
vq->done_idx = 0;
vq->ubufs = NULL;
}

static int vhost_worker(void *data)
Expand Down Expand Up @@ -225,10 +230,28 @@ static int vhost_worker(void *data)
return 0;
}

static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
{
kfree(vq->indirect);
vq->indirect = NULL;
kfree(vq->log);
vq->log = NULL;
kfree(vq->heads);
vq->heads = NULL;
kfree(vq->ubuf_info);
vq->ubuf_info = NULL;
}

void vhost_enable_zcopy(int vq)
{
vhost_zcopy_mask |= 0x1 << vq;
}

/* Helper to allocate iovec buffers for all vqs. */
static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
{
int i;
bool zcopy;

for (i = 0; i < dev->nvqs; ++i) {
dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
Expand All @@ -237,34 +260,30 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
GFP_KERNEL);
dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
UIO_MAXIOV, GFP_KERNEL);

zcopy = vhost_zcopy_mask & (0x1 << i);
if (zcopy)
dev->vqs[i].ubuf_info =
kmalloc(sizeof *dev->vqs[i].ubuf_info *
UIO_MAXIOV, GFP_KERNEL);
if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
!dev->vqs[i].heads)
!dev->vqs[i].heads ||
(zcopy && !dev->vqs[i].ubuf_info))
goto err_nomem;
}
return 0;

err_nomem:
for (; i >= 0; --i) {
kfree(dev->vqs[i].indirect);
kfree(dev->vqs[i].log);
kfree(dev->vqs[i].heads);
}
for (; i >= 0; --i)
vhost_vq_free_iovecs(&dev->vqs[i]);
return -ENOMEM;
}

static void vhost_dev_free_iovecs(struct vhost_dev *dev)
{
int i;

for (i = 0; i < dev->nvqs; ++i) {
kfree(dev->vqs[i].indirect);
dev->vqs[i].indirect = NULL;
kfree(dev->vqs[i].log);
dev->vqs[i].log = NULL;
kfree(dev->vqs[i].heads);
dev->vqs[i].heads = NULL;
}
for (i = 0; i < dev->nvqs; ++i)
vhost_vq_free_iovecs(&dev->vqs[i]);
}

long vhost_dev_init(struct vhost_dev *dev,
Expand All @@ -287,6 +306,7 @@ long vhost_dev_init(struct vhost_dev *dev,
dev->vqs[i].log = NULL;
dev->vqs[i].indirect = NULL;
dev->vqs[i].heads = NULL;
dev->vqs[i].ubuf_info = NULL;
dev->vqs[i].dev = dev;
mutex_init(&dev->vqs[i].mutex);
vhost_vq_reset(dev, dev->vqs + i);
Expand Down Expand Up @@ -390,6 +410,30 @@ long vhost_dev_reset_owner(struct vhost_dev *dev)
return 0;
}

/* In case of DMA done not in order in lower device driver for some reason.
* upend_idx is used to track end of used idx, done_idx is used to track head
* of used idx. Once lower device DMA done contiguously, we will signal KVM
* guest used idx.
*/
int vhost_zerocopy_signal_used(struct vhost_virtqueue *vq)
{
int i;
int j = 0;

for (i = vq->done_idx; i != vq->upend_idx; i = (i + 1) % UIO_MAXIOV) {
if ((vq->heads[i].len == VHOST_DMA_DONE_LEN)) {
vq->heads[i].len = VHOST_DMA_CLEAR_LEN;
vhost_add_used_and_signal(vq->dev, vq,
vq->heads[i].id, 0);
++j;
} else
break;
}
if (j)
vq->done_idx = i;
return j;
}

/* Caller should have device mutex */
void vhost_dev_cleanup(struct vhost_dev *dev)
{
Expand All @@ -400,6 +444,13 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
vhost_poll_stop(&dev->vqs[i].poll);
vhost_poll_flush(&dev->vqs[i].poll);
}
/* Wait for all lower device DMAs done. */
if (dev->vqs[i].ubufs)
vhost_ubuf_put_and_wait(dev->vqs[i].ubufs);

/* Signal guest as appropriate. */
vhost_zerocopy_signal_used(&dev->vqs[i]);

if (dev->vqs[i].error_ctx)
eventfd_ctx_put(dev->vqs[i].error_ctx);
if (dev->vqs[i].error)
Expand Down Expand Up @@ -1486,3 +1537,50 @@ void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
&vq->used->flags, r);
}
}

static void vhost_zerocopy_done_signal(struct kref *kref)
{
struct vhost_ubuf_ref *ubufs = container_of(kref, struct vhost_ubuf_ref,
kref);
wake_up(&ubufs->wait);
}

struct vhost_ubuf_ref *vhost_ubuf_alloc(struct vhost_virtqueue *vq,
bool zcopy)
{
struct vhost_ubuf_ref *ubufs;
/* No zero copy backend? Nothing to count. */
if (!zcopy)
return NULL;
ubufs = kmalloc(sizeof *ubufs, GFP_KERNEL);
if (!ubufs)
return ERR_PTR(-ENOMEM);
kref_init(&ubufs->kref);
kref_get(&ubufs->kref);
init_waitqueue_head(&ubufs->wait);
ubufs->vq = vq;
return ubufs;
}

void vhost_ubuf_put(struct vhost_ubuf_ref *ubufs)
{
kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
}

void vhost_ubuf_put_and_wait(struct vhost_ubuf_ref *ubufs)
{
kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
wait_event(ubufs->wait, !atomic_read(&ubufs->kref.refcount));
kfree(ubufs);
}

void vhost_zerocopy_callback(void *arg)
{
struct ubuf_info *ubuf = arg;
struct vhost_ubuf_ref *ubufs = ubuf->arg;
struct vhost_virtqueue *vq = ubufs->vq;

/* set len = 1 to mark this desc buffers done DMA */
vq->heads[ubuf->desc].len = VHOST_DMA_DONE_LEN;
kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
}
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