@@ -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>
@@ -28,10 +29,18 @@
#include "vhost.h"
+static int zcopytx;
+module_param(zcopytx, int, 0444);
+MODULE_PARM_DESC(lnksts, "Enable Zero Copy Transmit");
+
/* 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,
@@ -54,6 +63,11 @@ struct vhost_net {
enum vhost_net_poll_state tx_poll_state;
};
+static bool vhost_sock_zcopy(struct socket *sock)
+{
+ return unlikely(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)
@@ -129,6 +143,8 @@ 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);
@@ -149,8 +165,13 @@ 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,
@@ -166,6 +187,12 @@ static void handle_tx(struct vhost_net *net)
set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
break;
}
+ /* If more outstanding DMAs, queue the work */
+ if (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;
@@ -188,9 +215,39 @@ 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;
@@ -198,7 +255,8 @@ static void handle_tx(struct vhost_net *net)
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);
@@ -603,6 +661,7 @@ 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);
@@ -632,6 +691,13 @@ 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);
@@ -639,6 +705,9 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
mutex_unlock(&vq->mutex);
+ if (oldubufs)
+ vhost_ubuf_put_and_wait(oldubufs);
+
if (oldsock) {
vhost_net_flush_vq(n, index);
fput(oldsock->file);
@@ -647,6 +716,8 @@ 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:
@@ -179,6 +179,9 @@ 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)
@@ -237,6 +240,8 @@ 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);
+ 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)
@@ -249,6 +254,7 @@ err_nomem:
kfree(dev->vqs[i].indirect);
kfree(dev->vqs[i].log);
kfree(dev->vqs[i].heads);
+ kfree(dev->vqs[i].ubuf_info);
}
return -ENOMEM;
}
@@ -390,6 +396,30 @@ 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)
{
@@ -400,6 +430,13 @@ 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)
@@ -1486,3 +1523,50 @@ 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);
+}
@@ -13,6 +13,11 @@
#include <linux/virtio_ring.h>
#include <asm/atomic.h>
+/* This is for zerocopy, used buffer len is set to 1 when lower device DMA
+ * done */
+#define VHOST_DMA_DONE_LEN 1
+#define VHOST_DMA_CLEAR_LEN 0
+
struct vhost_device;
struct vhost_work;
@@ -50,6 +55,18 @@ struct vhost_log {
u64 len;
};
+struct vhost_virtqueue;
+
+struct vhost_ubuf_ref {
+ struct kref kref;
+ wait_queue_t wait;
+ struct vhost_virtqueue *vq;
+};
+
+struct vhost_ubuf_ref *vhost_ubuf_alloc(struct vhost_virtqueue *, bool zcopy);
+void vhost_ubuf_put(struct vhost_ubuf_ref *);
+void vhost_ubuf_put_and_wait(struct vhost_ubuf_ref *);
+
/* The virtqueue structure describes a queue attached to a device. */
struct vhost_virtqueue {
struct vhost_dev *dev;
@@ -114,6 +131,16 @@ struct vhost_virtqueue {
/* Log write descriptors */
void __user *log_base;
struct vhost_log *log;
+ /* vhost zerocopy support fields below: */
+ /* last used idx for outstanding DMA zerocopy buffers */
+ int upend_idx;
+ /* first used idx for DMA done zerocopy buffers */
+ int done_idx;
+ /* an array of userspace buffers info */
+ struct ubuf_info *ubuf_info;
+ /* Reference counting for outstanding ubufs.
+ * Protected by vq mutex. Writers must also take device mutex. */
+ struct vhost_ubuf_ref *ubufs;
};
struct vhost_dev {
@@ -160,6 +187,8 @@ bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *);
int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
unsigned int log_num, u64 len);
+void vhost_zerocopy_callback(void *arg);
+int vhost_zerocopy_signal_used(struct vhost_virtqueue *vq);
#define vq_err(vq, fmt, ...) do { \
pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \