Re: [PATCHv6 3/3] vhost_net: a kernel-level virtio server

Daniel Walker
2009-11-03T00:05:58Z

Random style issues below .. Part of this is just stuff checkpatch
found.

On Tue, 2009-11-03 at 00:29 +0200, Michael S. Tsirkin wrote:

> +static int move_iovec_hdr(struct iovec *from, struct iovec *to,
> + size_t len, int iov_count)
> +{
> + int seg = 0;
> + size_t size;
> + while (len && seg < iov_count) {
> + size = min(from->iov_len, len);
> + to->iov_base = from->iov_base;
> + to->iov_len = size;
> + from->iov_len -= size;
> + from->iov_base += size;
> + len -= size;
> + ++from;
> + ++to;
> + ++seg;
> + }
> + return seg;
> +}

The code above isn't properly indented .. You need to use tabs.

> +/* Caller must have TX VQ lock */
> +static void tx_poll_stop(struct vhost_net *net)
> +{
> + if (likely(net->tx_poll_state != VHOST_NET_POLL_STARTED))
> + return;
> + vhost_poll_stop(net->poll + VHOST_NET_VQ_TX);
> + net->tx_poll_state = VHOST_NET_POLL_STOPPED;
> +}
> +
> +/* Caller must have TX VQ lock */
> +static void tx_poll_start(struct vhost_net *net, struct socket *sock)
> +{
> + if (unlikely(net->tx_poll_state != VHOST_NET_POLL_STOPPED))
> + return;
> + vhost_poll_start(net->poll + VHOST_NET_VQ_TX, sock->file);
> + net->tx_poll_state = VHOST_NET_POLL_STARTED;
> +}
> +
> +/* Expects to be always run from workqueue - which acts as
> + * read-size critical section for our kind of RCU. */
> +static void handle_tx(struct vhost_net *net)
> +{
> + struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_TX];
> + unsigned head, out, in, s;
> + struct msghdr msg = {
> + .msg_name = NULL,
> + .msg_namelen = 0,
> + .msg_control = NULL,
> + .msg_controllen = 0,
> + .msg_iov = vq->iov,
> + .msg_flags = MSG_DONTWAIT,
> + };
> + size_t len, total_len = 0;
> + int err, wmem;
> + size_t hdr_size;
> + struct socket *sock = rcu_dereference(vq->private_data);
> + if (!sock)
> + return;
> +
> + wmem = atomic_read(&sock->sk->sk_wmem_alloc);
> + if (wmem >= sock->sk->sk_sndbuf)
> + return;
> +
> + use_mm(net->dev.mm);
> + mutex_lock(&vq->mutex);
> + vhost_no_notify(vq);
> +
> + if (wmem < sock->sk->sk_sndbuf * 2)
> + tx_poll_stop(net);
> + hdr_size = vq->hdr_size;
> +
> + for (;;) {
> + head = vhost_get_vq_desc(&net->dev, vq, vq->iov, &out, &in,
> + NULL, NULL);
> + /* Nothing new? Wait for eventfd to tell us they refilled. */
> + if (head == vq->num) {
> + wmem = atomic_read(&sock->sk->sk_wmem_alloc);
> + if (wmem >= sock->sk->sk_sndbuf * 3 / 4) {
> + tx_poll_start(net, sock);
> + set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
> + break;
> + }
> + if (vhost_notify(vq)) {
> + continue;
> + }
> + break;
> + }
> + if (in) {
> + vq_err(vq, "Unexpected descriptor format for TX: "
> + "out %d, int %d\n", out, in);
> + break;
> + }
> + /* Skip header. TODO: support TSO. */
> + s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, out);
> + msg.msg_iovlen = out;
> + len = iov_length(vq->iov, out);
> + /* Sanity check */
> + if (!len) {
> + vq_err(vq, "Unexpected header len for TX: "
> + "%ld expected %zd\n",
> + iov_length(vq->hdr, s), hdr_size);
> + break;
> + }
> + /* TODO: Check specific error and bomb out unless ENOBUFS? */
> + err = sock->ops->sendmsg(NULL, sock, &msg, len);
> + if (unlikely(err < 0)) {
> + vhost_discard_vq_desc(vq);
> + tx_poll_start(net, sock);
> + break;
> + }
> + if (err != len)
> + pr_err("Truncated TX packet: "
> + " len %d != %zd\n", err, len);
> + vhost_add_used_and_trigger(&net->dev, vq, head, 0);
> + total_len += len;
> + if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
> + vhost_poll_queue(&vq->poll);
> + break;
> + }
> + }
> +
> + mutex_unlock(&vq->mutex);
> + unuse_mm(net->dev.mm);
> +}
> +
> +/* Expects to be always run from workqueue - which acts as
> + * read-size critical section for our kind of RCU. */
> +static void handle_rx(struct vhost_net *net)
> +{
> + struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_RX];
> + unsigned head, out, in, log, s;
> + struct vhost_log *vq_log;
> + struct msghdr msg = {
> + .msg_name = NULL,
> + .msg_namelen = 0,
> + .msg_control = NULL, /* FIXME: get and handle RX aux data. */
> + .msg_controllen = 0,
> + .msg_iov = vq->iov,
> + .msg_flags = MSG_DONTWAIT,
> + };
> +
> + struct virtio_net_hdr hdr = {
> + .flags = 0,
> + .gso_type = VIRTIO_NET_HDR_GSO_NONE
> + };
> +
> + size_t len, total_len = 0;
> + int err;
> + size_t hdr_size;
> + struct socket *sock = rcu_dereference(vq->private_data);
> + if (!sock || skb_queue_empty(&sock->sk->sk_receive_queue))
> + return;
> +
> + use_mm(net->dev.mm);
> + mutex_lock(&vq->mutex);
> + vhost_no_notify(vq);
> + hdr_size = vq->hdr_size;
> +
> + vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) ?
> + vq->log : NULL;
> +
> + for (;;) {
> + head = vhost_get_vq_desc(&net->dev, vq, vq->iov, &out, &in,
> + vq_log, &log);
> + /* OK, now we need to know about added descriptors. */
> + if (head == vq->num && vhost_notify(vq))
> + /* They could have slipped one in as we were doing that:
> + * check again. */
> + continue;
> + /* Nothing new? Wait for eventfd to tell us they refilled. */
> + if (head == vq->num)
> + break;
> + /* We don't need to be notified again. */
> + vhost_no_notify(vq);
> + if (out) {
> + vq_err(vq, "Unexpected descriptor format for RX: "
> + "out %d, int %d\n",
> + out, in);
> + break;
> + }
> + /* Skip header. TODO: support TSO/mergeable rx buffers. */
> + s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, in);
> + msg.msg_iovlen = in;
> + len = iov_length(vq->iov, in);
> + /* Sanity check */
> + if (!len) {
> + vq_err(vq, "Unexpected header len for RX: "
> + "%zd expected %zd\n",
> + iov_length(vq->hdr, s), hdr_size);
> + break;
> + }
> + err = sock->ops->recvmsg(NULL, sock, &msg,
> + len, MSG_DONTWAIT | MSG_TRUNC);
> + /* TODO: Check specific error and bomb out unless EAGAIN? */
> + if (err < 0) {
> + vhost_discard_vq_desc(vq);
> + break;
> + }
> + /* TODO: Should check and handle checksum. */
> + if (err > len) {
> + pr_err("Discarded truncated rx packet: "
> + " len %d > %zd\n", err, len);
> + vhost_discard_vq_desc(vq);
> + continue;
> + }
> + len = err;
> + err = memcpy_toiovec(vq->hdr, (unsigned char *)&hdr, hdr_size);
> + if (err) {
> + vq_err(vq, "Unable to write vnet_hdr at addr %p: %d\n",
> + vq->iov->iov_base, err);
> + break;
> + }
> + len += hdr_size;
> + vhost_add_used_and_trigger(&net->dev, vq, head, len);
> + if (unlikely(vq_log))
> + vhost_log_write(vq, vq_log, log, len);
> + total_len += len;
> + if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
> + vhost_poll_queue(&vq->poll);
> + break;
> + }
> + }
> +
> + mutex_unlock(&vq->mutex);
> + unuse_mm(net->dev.mm);
> +}
> +
> +static void handle_tx_kick(struct work_struct *work)
> +{
> + struct vhost_virtqueue *vq;
> + struct vhost_net *net;
> + vq = container_of(work, struct vhost_virtqueue, poll.work);
> + net = container_of(vq->dev, struct vhost_net, dev);
> + handle_tx(net);
> +}
> +
> +static void handle_rx_kick(struct work_struct *work)
> +{
> + struct vhost_virtqueue *vq;
> + struct vhost_net *net;
> + vq = container_of(work, struct vhost_virtqueue, poll.work);
> + net = container_of(vq->dev, struct vhost_net, dev);
> + handle_rx(net);
> +}
> +
> +static void handle_tx_net(struct work_struct *work)
> +{
> + struct vhost_net *net;
> + net = container_of(work, struct vhost_net, poll[VHOST_NET_VQ_TX].work);
> + handle_tx(net);
> +}
> +
> +static void handle_rx_net(struct work_struct *work)
> +{
> + struct vhost_net *net;
> + net = container_of(work, struct vhost_net, poll[VHOST_NET_VQ_RX].work);
> + handle_rx(net);
> +}
> +
> +static int vhost_net_open(struct inode *inode, struct file *f)
> +{
> + struct vhost_net *n = kzalloc(sizeof *n, GFP_KERNEL);
> + int r;
> + if (!n)
> + return -ENOMEM;
> + f->private_data = n;
> + n->vqs[VHOST_NET_VQ_TX].handle_kick = handle_tx_kick;
> + n->vqs[VHOST_NET_VQ_RX].handle_kick = handle_rx_kick;
> + r = vhost_dev_init(&n->dev, n->vqs, VHOST_NET_VQ_MAX);
> + if (r < 0) {
> + kfree(n);
> + return r;
> + }
> +
> + vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT);
> + vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN);
> + n->tx_poll_state = VHOST_NET_POLL_DISABLED;
> + return 0;
> +}
> +
> +static void vhost_net_disable_vq(struct vhost_net *n, int index)
> +{
> + if (!n->vqs[index].private_data)
> + return;
> + if (index == VHOST_NET_VQ_TX) {
> + tx_poll_stop(n);
> + n->tx_poll_state = VHOST_NET_POLL_DISABLED;
> + } else
> + vhost_poll_stop(n->poll + VHOST_NET_VQ_RX);
> +}
> +
> +static void vhost_net_enable_vq(struct vhost_net *n, int index)
> +{
> + struct socket *sock = n->vqs[index].private_data;
> + if (!sock)
> + return;
> + if (index == VHOST_NET_VQ_TX) {
> + n->tx_poll_state = VHOST_NET_POLL_STOPPED;
> + tx_poll_start(n, sock);
> + } else
> + vhost_poll_start(n->poll + VHOST_NET_VQ_RX, sock->file);
> +}
> +
> +static struct socket *vhost_net_stop_vq(struct vhost_net *n, int index)
> +{
> + struct socket *sock;
> +
> + mutex_lock(&n->vqs[index].mutex);
> + sock = n->vqs[index].private_data;
> + vhost_net_disable_vq(n, index);
> + rcu_assign_pointer(n->vqs[index].private_data, NULL);
> + mutex_unlock(&n->vqs[index].mutex);
> + return sock;
> +}
> +
> +static void vhost_net_stop(struct vhost_net *n, struct socket **tx_sock,
> + struct socket **rx_sock)
> +{
> + *tx_sock = vhost_net_stop_vq(n, VHOST_NET_VQ_TX);
> + *rx_sock = vhost_net_stop_vq(n, VHOST_NET_VQ_RX);
> +}
> +
> +static void vhost_net_flush_vq(struct vhost_net *n, int index)
> +{
> + vhost_poll_flush(n->poll + index);
> + vhost_poll_flush(&n->dev.vqs[index].poll);
> +}
> +
> +static void vhost_net_flush(struct vhost_net *n)
> +{
> + vhost_net_flush_vq(n, VHOST_NET_VQ_TX);
> + vhost_net_flush_vq(n, VHOST_NET_VQ_RX);
> +}
> +
> +static int vhost_net_release(struct inode *inode, struct file *f)
> +{
> + struct vhost_net *n = f->private_data;
> + struct socket *tx_sock;
> + struct socket *rx_sock;
> +
> + vhost_net_stop(n, &tx_sock, &rx_sock);
> + vhost_net_flush(n);
> + vhost_dev_cleanup(&n->dev);
> + if (tx_sock)
> + fput(tx_sock->file);
> + if (rx_sock)
> + fput(rx_sock->file);
> + /* We do an extra flush before freeing memory,
> + * since jobs can re-queue themselves. */
> + vhost_net_flush(n);
> + kfree(n);
> + return 0;
> +}
> +
> +static struct socket *get_raw_socket(int fd)
> +{
> + struct {
> + struct sockaddr_ll sa;
> + char buf[MAX_ADDR_LEN];
> + } uaddr;
> + int uaddr_len = sizeof uaddr, r;
> + struct socket *sock = sockfd_lookup(fd, &r);
> + if (!sock)
> + return ERR_PTR(-ENOTSOCK);
> +
> + /* Parameter checking */
> + if (sock->sk->sk_type != SOCK_RAW) {
> + r = -ESOCKTNOSUPPORT;
> + goto err;
> + }
> +
> + r = sock->ops->getname(sock, (struct sockaddr *)&uaddr.sa,
> + &uaddr_len, 0);
> + if (r)
> + goto err;
> +
> + if (uaddr.sa.sll_family != AF_PACKET) {
> + r = -EPFNOSUPPORT;
> + goto err;
> + }
> + return sock;
> +err:
> + fput(sock->file);
> + return ERR_PTR(r);
> +}
> +
> +static struct socket *get_tun_socket(int fd)
> +{
> + struct file *file = fget(fd);
> + struct socket *sock;
> + if (!file)
> + return ERR_PTR(-EBADF);
> + sock = tun_get_socket(file);
> + if (IS_ERR(sock))
> + fput(file);
> + return sock;
> +}
> +
> +static struct socket *get_socket(int fd)
> +{
> + struct socket *sock;
> + if (fd == -1)
> + return NULL;
> + sock = get_raw_socket(fd);
> + if (!IS_ERR(sock))
> + return sock;
> + sock = get_tun_socket(fd);
> + if (!IS_ERR(sock))
> + return sock;
> + return ERR_PTR(-ENOTSOCK);
> +}
> +
> +static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
> +{
> + struct socket *sock, *oldsock = NULL;
> + struct vhost_virtqueue *vq;
> + int r;
> +
> + mutex_lock(&n->dev.mutex);
> + r = vhost_dev_check_owner(&n->dev);
> + if (r)
> + goto done;
> +
> + if (index >= VHOST_NET_VQ_MAX) {
> + r = -ENOBUFS;
> + goto done;
> + }
> + vq = n->vqs + index;
> + mutex_lock(&vq->mutex);
> + sock = get_socket(fd);
> + if (IS_ERR(sock)) {
> + r = PTR_ERR(sock);
> + goto done;
> + }
> +
> + /* start polling new socket */
> + oldsock = vq->private_data;
> + if (sock == oldsock)
> + goto done;
> +
> + vhost_net_disable_vq(n, index);
> + rcu_assign_pointer(vq->private_data, sock);
> + vhost_net_enable_vq(n, index);
> + mutex_unlock(&vq->mutex);
> +done:
> + mutex_unlock(&n->dev.mutex);
> + if (oldsock) {
> + vhost_net_flush_vq(n, index);
> + fput(oldsock->file);
> + }
> + return r;
> +}
> +
> +static long vhost_net_reset_owner(struct vhost_net *n)
> +{
> + struct socket *tx_sock = NULL;
> + struct socket *rx_sock = NULL;
> + long r;
> + mutex_lock(&n->dev.mutex);
> + r = vhost_dev_check_owner(&n->dev);
> + if (r)
> + goto done;
> + vhost_net_stop(n, &tx_sock, &rx_sock);
> + vhost_net_flush(n);
> + r = vhost_dev_reset_owner(&n->dev);
> +done:
> + mutex_unlock(&n->dev.mutex);
> + if (tx_sock)
> + fput(tx_sock->file);
> + if (rx_sock)
> + fput(rx_sock->file);
> + return r;
> +}
> +
> +static void vhost_net_set_features(struct vhost_net *n, u64 features)
> +{
> + size_t hdr_size = features & (1 << VHOST_NET_F_VIRTIO_NET_HDR) ?
> + sizeof(struct virtio_net_hdr) : 0;
> + int i;
> + mutex_unlock(&n->dev.mutex);
> + n->dev.acked_features = features;
> + smp_wmb();
> + for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
> + mutex_lock(&n->vqs[i].mutex);
> + n->vqs[i].hdr_size = hdr_size;
> + mutex_unlock(&n->vqs[i].mutex);
> + }
> + mutex_unlock(&n->dev.mutex);
> + vhost_net_flush(n);
> +}
> +
> +static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
> + unsigned long arg)
> +{
> + struct vhost_net *n = f->private_data;
> + void __user *argp = (void __user *)arg;
> + u32 __user *featurep = argp;
> + struct vhost_vring_file backend;
> + u64 features;
> + int r;
> + switch (ioctl) {
> + case VHOST_NET_SET_BACKEND:
> + r = copy_from_user(&backend, argp, sizeof backend);
> + if (r < 0)
> + return r;
> + return vhost_net_set_backend(n, backend.index, backend.fd);
> + case VHOST_GET_FEATURES:
> + features = VHOST_FEATURES;
> + return put_user(features, featurep);
> + case VHOST_ACK_FEATURES:
> + r = get_user(features, featurep);
> + /* No features for now */
> + if (r < 0)
> + return r;
> + if (features & ~VHOST_FEATURES)
> + return -EOPNOTSUPP;
> + vhost_net_set_features(n, features);
> + return 0;
> + case VHOST_RESET_OWNER:
> + return vhost_net_reset_owner(n);
> + default:
> + r = vhost_dev_ioctl(&n->dev, ioctl, arg);
> + vhost_net_flush(n);
> + return r;
> + }
> +}
> +
> +#ifdef CONFIG_COMPAT
> +static long vhost_net_compat_ioctl(struct file *f, unsigned int ioctl,
> + unsigned long arg)
> +{
> + return vhost_net_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
> +}
> +#endif
> +
> +const static struct file_operations vhost_net_fops = {
> + .owner = THIS_MODULE,
> + .release = vhost_net_release,
> + .unlocked_ioctl = vhost_net_ioctl,
> +#ifdef CONFIG_COMPAT
> + .compat_ioctl = vhost_net_compat_ioctl,
> +#endif
> + .open = vhost_net_open,
> +};
> +
> +static struct miscdevice vhost_net_misc = {
> + VHOST_NET_MINOR,
> + "vhost-net",
> + &vhost_net_fops,
> +};
> +
> +int vhost_net_init(void)
> +{
> + int r = vhost_init();
> + if (r)
> + goto err_init;
> + r = misc_register(&vhost_net_misc);
> + if (r)
> + goto err_reg;
> + return 0;
> +err_reg:
> + vhost_cleanup();
> +err_init:
> + return r;
> +
> +}
> +module_init(vhost_net_init);
> +
> +void vhost_net_exit(void)
> +{
> + misc_deregister(&vhost_net_misc);
> + vhost_cleanup();
> +}
> +module_exit(vhost_net_exit);
> +
> +MODULE_VERSION("0.0.1");
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Michael S. Tsirkin");
> +MODULE_DESCRIPTION("Host kernel accelerator for virtio net");
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> new file mode 100644
> index 0000000..6db2e63
> --- /dev/null
> +++ b/drivers/vhost/vhost.c
> @@ -0,0 +1,968 @@
> +/* Copyright (C) 2009 Red Hat, Inc.
> + * Copyright (C) 2006 Rusty Russell IBM Corporation
> + *
> + * Author: Michael S. Tsirkin <mst@redhat.com>
> + *
> + * Inspiration, some code, and most witty comments come from
> + * Documentation/lguest/lguest.c, by Rusty Russell
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> + *
> + * Generic code for virtio server in host kernel.
> + */
> +
> +#include <linux/eventfd.h>
> +#include <linux/vhost.h>
> +#include <linux/virtio_net.h>
> +#include <linux/mm.h>
> +#include <linux/miscdevice.h>
> +#include <linux/mutex.h>
> +#include <linux/workqueue.h>
> +#include <linux/rcupdate.h>
> +#include <linux/poll.h>
> +#include <linux/file.h>
> +#include <linux/highmem.h>
> +
> +#include <linux/net.h>
> +#include <linux/if_packet.h>
> +#include <linux/if_arp.h>
> +
> +#include <net/sock.h>
> +
> +#include "vhost.h"
> +
> +enum {
> + VHOST_MEMORY_MAX_NREGIONS = 64,
> + VHOST_MEMORY_F_LOG = 0x1,
> +};
> +
> +static struct workqueue_struct *vhost_workqueue;
> +
> +static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
> + poll_table *pt)
> +{
> + struct vhost_poll *poll;
> + poll = container_of(pt, struct vhost_poll, table);
> +
> + poll->wqh = wqh;
> + add_wait_queue(wqh, &poll->wait);
> +}
> +
> +static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
> + void *key)
> +{
> + struct vhost_poll *poll;
> + poll = container_of(wait, struct vhost_poll, wait);
> + if (!((unsigned long)key & poll->mask))
> + return 0;
> +
> + queue_work(vhost_workqueue, &poll->work);
> + return 0;
> +}
> +
> +/* Init poll structure */
> +void vhost_poll_init(struct vhost_poll *poll, work_func_t func,
> + unsigned long mask)
> +{
> + INIT_WORK(&poll->work, func);
> + init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
> + init_poll_funcptr(&poll->table, vhost_poll_func);
> + poll->mask = mask;
> +}
> +
> +/* Start polling a file. We add ourselves to file's wait queue. The caller must
> + * keep a reference to a file until after vhost_poll_stop is called. */
> +void vhost_poll_start(struct vhost_poll *poll, struct file *file)
> +{
> + unsigned long mask;
> + mask = file->f_op->poll(file, &poll->table);
> + if (mask)
> + vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
> +}
> +
> +/* Stop polling a file. After this function returns, it becomes safe to drop the
> + * file reference. You must also flush afterwards. */
> +void vhost_poll_stop(struct vhost_poll *poll)
> +{
> + remove_wait_queue(poll->wqh, &poll->wait);
> +}
> +
> +/* Flush any work that has been scheduled. When calling this, don't hold any
> + * locks that are also used by the callback. */
> +void vhost_poll_flush(struct vhost_poll *poll)
> +{
> + flush_work(&poll->work);
> +}
> +
> +void vhost_poll_queue(struct vhost_poll *poll)
> +{
> + queue_work(vhost_workqueue, &poll->work);
> +}
> +
> +long vhost_dev_init(struct vhost_dev *dev,
> + struct vhost_virtqueue *vqs, int nvqs)
> +{
> + int i;
> + dev->vqs = vqs;
> + dev->nvqs = nvqs;
> + mutex_init(&dev->mutex);
> +
> + for (i = 0; i < dev->nvqs; ++i) {
> + dev->vqs[i].dev = dev;
> + mutex_init(&dev->vqs[i].mutex);
> + if (dev->vqs[i].handle_kick)
> + vhost_poll_init(&dev->vqs[i].poll,
> + dev->vqs[i].handle_kick,
> + POLLIN);
> + }
> + return 0;
> +}
> +
> +/* Caller should have device mutex */
> +long vhost_dev_check_owner(struct vhost_dev *dev)
> +{
> + /* Are you the owner? If not, I don't think you mean to do that */
> + return dev->mm == current->mm ? 0 : -EPERM;
> +}
> +
> +/* Caller should have device mutex */
> +static long vhost_dev_set_owner(struct vhost_dev *dev)
> +{
> + /* Is there an owner already? */
> + if (dev->mm)
> + return -EBUSY;
> + /* No owner, become one */
> + dev->mm = get_task_mm(current);
> + return 0;
> +}
> +
> +/* Caller should have device mutex */
> +long vhost_dev_reset_owner(struct vhost_dev *dev)
> +{
> + struct vhost_memory *memory;
> +
> + /* Restore memory to default 1:1 mapping. */
> + memory = kzalloc(offsetof(struct vhost_memory, regions) +
> + 2 * sizeof *memory->regions, GFP_KERNEL);
> + if (!memory)
> + return -ENOMEM;
> +
> + vhost_dev_cleanup(dev);
> +
> + memory->nregions = 2;
> + memory->regions[0].guest_phys_addr = 1;
> + memory->regions[0].userspace_addr = 1;
> + memory->regions[0].memory_size = ~0ULL;
> + memory->regions[1].guest_phys_addr = 0;
> + memory->regions[1].userspace_addr = 0;
> + memory->regions[1].memory_size = 1;
> + dev->memory = memory;
> + return 0;
> +}
> +
> +/* Caller should have device mutex */
> +void vhost_dev_cleanup(struct vhost_dev *dev)
> +{
> + int i;
> + for (i = 0; i < dev->nvqs; ++i) {
> + if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
> + vhost_poll_stop(&dev->vqs[i].poll);
> + vhost_poll_flush(&dev->vqs[i].poll);
> + }
> + if (dev->vqs[i].error_ctx)
> + eventfd_ctx_put(dev->vqs[i].error_ctx);
> + if (dev->vqs[i].error)
> + fput(dev->vqs[i].error);
> + if (dev->vqs[i].kick)
> + fput(dev->vqs[i].kick);
> + if (dev->vqs[i].call_ctx)
> + eventfd_ctx_put(dev->vqs[i].call_ctx);
> + if (dev->vqs[i].call)
> + fput(dev->vqs[i].call);
> + dev->vqs[i].error_ctx = NULL;
> + dev->vqs[i].error = NULL;
> + dev->vqs[i].kick = NULL;
> + dev->vqs[i].call_ctx = NULL;
> + dev->vqs[i].call = NULL;
> + }
> + if (dev->log_ctx)
> + eventfd_ctx_put(dev->log_ctx);
> + dev->log_ctx = NULL;
> + if (dev->log_file)
> + fput(dev->log_file);
> + dev->log_file = NULL;
> + /* No one will access memory at this point */
> + kfree(dev->memory);
> + dev->memory = NULL;
> + if (dev->mm)
> + mmput(dev->mm);
> + dev->mm = NULL;
> +}
> +
> +static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
> +{
> + struct vhost_memory mem, *newmem, *oldmem;
> + unsigned long size = offsetof(struct vhost_memory, regions);
> + long r;
> + r = copy_from_user(&mem, m, size);
> + if (r)
> + return r;
> + if (mem.padding)
> + return -EOPNOTSUPP;
> + if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
> + return -E2BIG;
> + newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
> + if (!newmem)
> + return -ENOMEM;
> +
> + memcpy(newmem, &mem, size);
> + r = copy_from_user(newmem->regions, m->regions,
> + mem.nregions * sizeof *m->regions);
> + if (r) {
> + kfree(newmem);
> + return r;
> + }
> + oldmem = d->memory;
> + rcu_assign_pointer(d->memory, newmem);
> + synchronize_rcu();
> + kfree(oldmem);
> + return 0;
> +}
> +
> +static int init_used(struct vhost_virtqueue *vq)
> +{
> + int r = put_user(vq->used_flags, &vq->used->flags);
> + if (r)
> + return r;
> + return get_user(vq->last_used_idx, &vq->used->idx);
> +}
> +
> +static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
> +{
> + struct file *eventfp, *filep = NULL,
> + *pollstart = NULL, *pollstop = NULL;
> + struct eventfd_ctx *ctx = NULL;
> + u32 __user *idxp = argp;
> + struct vhost_virtqueue *vq;
> + struct vhost_vring_state s;
> + struct vhost_vring_file f;
> + struct vhost_vring_addr a;
> + u32 idx;
> + long r;
> +
> + r = get_user(idx, idxp);
> + if (r < 0)
> + return r;
> + if (idx > d->nvqs)
> + return -ENOBUFS;
> +
> + vq = d->vqs + idx;
> +
> + mutex_lock(&vq->mutex);
> +
> + switch (ioctl) {
> + case VHOST_SET_VRING_NUM:
> + r = copy_from_user(&s, argp, sizeof s);
> + if (r < 0)
> + break;
> + if (s.num > 0xffff) {
> + r = -EINVAL;
> + break;
> + }
> + vq->num = s.num;
> + break;
> + case VHOST_SET_VRING_BASE:
> + r = copy_from_user(&s, argp, sizeof s);
> + if (r < 0)
> + break;
> + if (s.num > 0xffff) {
> + r = -EINVAL;
> + break;
> + }
> + vq->avail_idx = vq->last_avail_idx = s.num;
> + break;
> + case VHOST_GET_VRING_BASE:
> + s.index = idx;
> + s.num = vq->last_avail_idx;
> + r = copy_to_user(argp, &s, sizeof s);
> + break;
> + case VHOST_SET_VRING_DESC:
> + r = copy_from_user(&a, argp, sizeof a);
> + if (r < 0)
> + break;
> + if (a.padding) {
> + r = -EOPNOTSUPP;
> + break;
> + }
> + if ((u64)(unsigned long)a.user_addr != a.user_addr) {
> + r = -EFAULT;
> + break;
> + }
> + vq->desc = (void __user *)(unsigned long)a.user_addr;
> + break;
> + case VHOST_SET_VRING_AVAIL:
> + r = copy_from_user(&a, argp, sizeof a);
> + if (r < 0)
> + break;
> + if (a.padding) {
> + r = -EOPNOTSUPP;
> + break;
> + }
> + if ((u64)(unsigned long)a.user_addr != a.user_addr) {
> + r = -EFAULT;
> + break;
> + }
> + if (a.user_addr & (sizeof *vq->avail->ring - 1)) {
> + r = -EINVAL;
> + break;
> + }
> + vq->avail = (void __user *)(unsigned long)a.user_addr;
> + /* Forget the cached index value. */
> + vq->avail_idx = vq->last_avail_idx;
> + break;
> + case VHOST_SET_VRING_USED:
> + r = copy_from_user(&a, argp, sizeof a);
> + if (r < 0)
> + break;
> + if (a.padding) {
> + r = -EOPNOTSUPP;
> + break;
> + }
> + if ((u64)(unsigned long)a.user_addr != a.user_addr) {
> + r = -EFAULT;
> + break;
> + }
> + if (a.user_addr & (sizeof *vq->used->ring - 1)) {
> + r = -EINVAL;
> + break;
> + }
> + vq->used = (void __user *)(unsigned long)a.user_addr;
> + r = init_used(vq);
> + if (r)
> + break;
> + break;
> + case VHOST_SET_VRING_LOG:
> + r = copy_from_user(&a, argp, sizeof a);
> + if (r < 0)
> + break;
> + if (a.padding) {
> + r = -EOPNOTSUPP;
> + break;
> + }
> + if (a.user_addr == VHOST_VRING_LOG_DISABLE) {
> + vq->log_used = false;
> + break;
> + }
> + if (a.user_addr & (sizeof *vq->used->ring - 1)) {
> + r = -EINVAL;
> + break;
> + }
> + vq->log_used = true;
> + vq->log_addr = a.user_addr;
> + break;
> + case VHOST_SET_VRING_KICK:
> + r = copy_from_user(&f, argp, sizeof f);
> + if (r < 0)
> + break;
> + eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
> + if (IS_ERR(eventfp))
> + return PTR_ERR(eventfp);
> + if (eventfp != vq->kick) {
> + pollstop = filep = vq->kick;
> + pollstart = vq->kick = eventfp;
> + } else
> + filep = eventfp;
> + break;
> + case VHOST_SET_VRING_CALL:
> + r = copy_from_user(&f, argp, sizeof f);
> + if (r < 0)
> + break;
> + eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
> + if (IS_ERR(eventfp))
> + return PTR_ERR(eventfp);
> + if (eventfp != vq->call) {
> + filep = vq->call;
> + ctx = vq->call_ctx;
> + vq->call = eventfp;
> + vq->call_ctx = eventfp ?
> + eventfd_ctx_fileget(eventfp) : NULL;
> + } else
> + filep = eventfp;
> + break;
> + case VHOST_SET_VRING_ERR:
> + r = copy_from_user(&f, argp, sizeof f);
> + if (r < 0)
> + break;
> + eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
> + if (IS_ERR(eventfp))
> + return PTR_ERR(eventfp);
> + if (eventfp != vq->error) {
> + filep = vq->error;
> + vq->error = eventfp;
> + ctx = vq->error_ctx;
> + vq->error_ctx = eventfp ?
> + eventfd_ctx_fileget(eventfp) : NULL;
> + } else
> + filep = eventfp;
> + break;
> + default:
> + r = -ENOIOCTLCMD;
> + }
> +
> + if (pollstop && vq->handle_kick)
> + vhost_poll_stop(&vq->poll);
> +
> + if (ctx)
> + eventfd_ctx_put(ctx);
> + if (filep)
> + fput(filep);
> +
> + if (pollstart && vq->handle_kick)
> + vhost_poll_start(&vq->poll, vq->kick);
> +
> + mutex_unlock(&vq->mutex);
> +
> + if (pollstop && vq->handle_kick)
> + vhost_poll_flush(&vq->poll);
> + return r;
> +}
> +
> +long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
> +{
> + void __user *argp = (void __user *)arg;
> + struct file *eventfp, *filep = NULL;
> + struct eventfd_ctx *ctx = NULL;
> + u64 p;
> + long r;
> + int i, fd;
> +
> + mutex_lock(&d->mutex);
> + /* If you are not the owner, you can become one */
> + if (ioctl == VHOST_SET_OWNER) {
> + r = vhost_dev_set_owner(d);
> + goto done;
> + }
> +
> + /* You must be the owner to do anything else */
> + r = vhost_dev_check_owner(d);
> + if (r)
> + goto done;
> +
> + switch (ioctl) {
> + case VHOST_SET_MEM_TABLE:
> + r = vhost_set_memory(d, argp);
> + break;
> + case VHOST_SET_LOG_BASE:
> + r = get_user(p, (u64 __user *)argp);
> + if (r < 0)
> + break;
> + if ((u64)(unsigned long)p != p) {
> + r = -EFAULT;
> + break;
> + }
> + for (i = 0; i < d->nvqs; ++i) {
> + mutex_lock(&d->vqs[i].mutex);
> + d->vqs[i].log_base = (void __user *)(unsigned long)p;
> + mutex_unlock(&d->vqs[i].mutex);
> + }
> + break;
> + case VHOST_SET_LOG_FD:
> + r = get_user(fd, (int __user *)argp);
> + if (r < 0)
> + break;
> + eventfp = fd == -1 ? NULL : eventfd_fget(fd);
> + if (IS_ERR(eventfp)) {
> + r = PTR_ERR(eventfp);
> + break;
> + }
> + if (eventfp != d->log_file) {
> + filep = d->log_file;
> + ctx = d->log_ctx;
> + d->log_ctx = eventfp ?
> + eventfd_ctx_fileget(eventfp) : NULL;
> + } else
> + filep = eventfp;
> + for (i = 0; i < d->nvqs; ++i) {
> + mutex_lock(&d->vqs[i].mutex);
> + d->vqs[i].log_ctx = d->log_ctx;
> + mutex_unlock(&d->vqs[i].mutex);
> + }
> + if (ctx)
> + eventfd_ctx_put(ctx);
> + if (filep)
> + fput(filep);
> + break;
> + default:
> + r = vhost_set_vring(d, ioctl, argp);
> + break;
> + }
> +done:
> + mutex_unlock(&d->mutex);
> + return r;
> +}
> +
> +static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
> + __u64 addr, __u32 len)
> +{
> + struct vhost_memory_region *reg;
> + int i;
> + /* linear search is not brilliant, but we really have on the order of 6
> + * regions in practice */
> + for (i = 0; i < mem->nregions; ++i) {
> + reg = mem->regions + i;
> + if (reg->guest_phys_addr <= addr &&
> + reg->guest_phys_addr + reg->memory_size - 1 >= addr)
> + return reg;
> + }
> + return NULL;
> +}
> +
> +/* TODO: This is really inefficient. We need something like get_user()
> + * (instruction directly accesses the data, with an exception table entry
> + * returning -EFAULT). See Documentation/x86/exception-tables.txt.
> + */
> +static int set_bit_to_user(int nr, void __user *addr)
> +{
> + unsigned long log = (unsigned long)addr;
> + struct page *page;
> + void *base;
> + int bit = nr + (log % PAGE_SIZE) * 8;
> + int r;
> + r = get_user_pages_fast(log, 1, 1, &page);
> + if (r)
> + return r;
> + base = kmap_atomic(page, KM_USER0);
> + set_bit(bit, base);
> + kunmap_atomic(base, KM_USERO);
> + set_page_dirty_lock(page);
> + put_page(page);
> + return 0;
> +}
> +
> +static int log_write(void __user *log_base,
> + u64 write_address, u64 write_length)
> +{
> + int r;
> + if (!write_length)
> + return 0;
> + write_address /= VHOST_PAGE_SIZE;
> + for (;;) {
> + u64 base = (u64)log_base;
> + u64 log = base + write_address / 8;
> + int bit = write_address % 8;
> + if ((u64)(unsigned long)log != log)
> + return -EFAULT;
> + r = set_bit_to_user(bit, (void __user *)log);
> + if (r < 0)
> + return r;
> + if (write_length <= VHOST_PAGE_SIZE)
> + break;
> + write_length -= VHOST_PAGE_SIZE;
> + write_address += VHOST_PAGE_SIZE;
> + }
> + return r;
> +}
> +
> +int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
> + unsigned int log_num, u64 len)
> +{
> + int i, r;
> +
> + /* Make sure data written is seen before log. */
> + wmb();
> + for (i = 0; i < log_num; ++i) {
> + u64 l = min(log[i].len, len);
> + r = log_write(vq->log_base, log[i].addr, l);
> + if (r < 0)
> + return r;
> + len -= l;
> + if (!len)
> + return 0;
> + }
> + if (vq->log_ctx)
> + eventfd_signal(vq->log_ctx, 1);
> + /* Length written exceeds what we have stored. This is a bug. */
> + BUG();
> + return 0;
> +}
> +
> +int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
> + struct iovec iov[], int iov_size)
> +{
> + const struct vhost_memory_region *reg;
> + struct vhost_memory *mem;
> + struct iovec *_iov;
> + u64 s = 0;
> + int ret = 0;
> +
> + rcu_read_lock();
> +
> + mem = rcu_dereference(dev->memory);
> + while ((u64)len > s) {
> + u64 size;
> + if (ret >= iov_size) {
> + ret = -ENOBUFS;
> + break;
> + }
> + reg = find_region(mem, addr, len);
> + if (!reg) {
> + ret = -EFAULT;
> + break;
> + }
> + _iov = iov + ret;
> + size = reg->memory_size - addr + reg->guest_phys_addr;
> + _iov->iov_len = min((u64)len, size);
> + _iov->iov_base = (void *)
> + (reg->userspace_addr + addr - reg->guest_phys_addr);
> + s += size;
> + addr += size;
> + ++ret;
> + }
> +
> + rcu_read_unlock();
> + return ret;
> +}
> +
> +/* Each buffer in the virtqueues is actually a chain of descriptors. This
> + * function returns the next descriptor in the chain,
> + * or -1 if we're at the end. */
> +static unsigned next_desc(struct vring_desc *desc)
> +{
> + unsigned int next;
> +
> + /* If this descriptor says it doesn't chain, we're done. */
> + if (!(desc->flags & VRING_DESC_F_NEXT))
> + return -1;
> +
> + /* Check they're not leading us off end of descriptors. */
> + next = desc->next;
> + /* Make sure compiler knows to grab that: we don't want it changing! */
> + /* We will use the result as an index in an array, so most
> + * architectures only need a compiler barrier here. */
> + read_barrier_depends();
> +
> + return next;
> +}
> +
> +static unsigned get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
> + struct iovec iov[],
> + unsigned int *out_num, unsigned int *in_num,
> + struct vhost_log *log, unsigned int *log_num,
> + struct vring_desc *indirect)
> +{
> + struct vring_desc desc;
> + unsigned int i = 0, count, found = 0;
> + int ret;
> +
> + /* Sanity check */
> + if (indirect->len % sizeof desc) {
> + vq_err(vq, "Invalid length in indirect descriptor: "

Need tabs for the line above.

> + "len 0x%llx not multiple of 0x%zx\n",
> + (unsigned long long)indirect->len,
> + sizeof desc);
> + return -EINVAL;
> + }
> +
> + ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
> + ARRAY_SIZE(vq->indirect));
> + if (ret < 0) {
> + vq_err(vq, "Translation failure %d in indirect.\n", ret);
> + return ret;
> + }
> +
> + /* We will use the result as an address to read from, so most
> + * architectures only need a compiler barrier here. */
> + read_barrier_depends();
> +
> + count = indirect->len / sizeof desc;
> + /* Buffers are chained via a 16 bit next field, so
> + * we can have at most 2^16 of these. */
> + if (count > 0x10000) {

Could you wrap that constant in a macro?

> + vq_err(vq, "Indirect buffer length too big: %d\n",
> + indirect->len);
> + return -E2BIG;
> + }
> +
> + do {
> + unsigned iov_count = *in_num + *out_num;
> + if (++found > count) {
> + vq_err(vq, "Loop detected: last one at %u "
> + "indirect size %u\n",
> + i, count);
> + return -EINVAL;
> + }
> + if (memcpy_fromiovec((unsigned char *)&desc, vq->indirect,
> + sizeof desc)) {;
> + vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
> + i, (size_t)indirect->addr + i * sizeof desc);
> + return -EINVAL;
> + }
> + if (desc.flags & VRING_DESC_F_INDIRECT) {
> + vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
> + i, (size_t)indirect->addr + i * sizeof desc);
> + return -EINVAL;
> + }
> +
> + ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
> + VHOST_NET_MAX_SG - iov_count);
> + if (ret < 0) {
> + vq_err(vq, "Translation failure %d indirect idx %d\n",
> + ret, i);
> + return ret;
> + }
> + /* If this is an input descriptor, increment that count. */
> + if (desc.flags & VRING_DESC_F_WRITE) {
> + *in_num += ret;
> + if (unlikely(log)) {
> + log[*log_num].addr = desc.addr;
> + log[*log_num].len = desc.len;
> + ++*log_num;
> + }
> + } else {
> + /* If it's an output descriptor, they're all supposed
> + * to come before any input descriptors. */
> + if (*in_num) {
> + vq_err(vq, "Indirect descriptor "
> + "has out after in: idx %d\n", i);
> + return -EINVAL;
> + }
> + *out_num += ret;
> + }
> + } while ((i = next_desc(&desc)) != -1);
> + return 0;
> +}
> +
> +/* This looks in the virtqueue and for the first available buffer, and converts
> + * it to an iovec for convenient access. Since descriptors consist of some
> + * number of output then some number of input descriptors, it's actually two
> + * iovecs, but we pack them into one and note how many of each there were.
> + *
> + * This function returns the descriptor number found, or vq->num (which
> + * is never a valid descriptor number) if none was found. */
> +unsigned vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
> + struct iovec iov[],
> + unsigned int *out_num, unsigned int *in_num,
> + struct vhost_log *log, unsigned int *log_num)
> +{
> + struct vring_desc desc;
> + unsigned int i, head, found = 0;
> + u16 last_avail_idx;
> + int ret;
> +
> + /* Check it isn't doing very strange things with descriptor numbers. */
> + last_avail_idx = vq->last_avail_idx;
> + if (get_user(vq->avail_idx, &vq->avail->idx)) {
> + vq_err(vq, "Failed to access avail idx at %p\n",
> + &vq->avail->idx);
> + return vq->num;
> + }
> +
> + if ((u16)(vq->avail_idx - last_avail_idx) > vq->num) {
> + vq_err(vq, "Guest moved used index from %u to %u",
> + last_avail_idx, vq->avail_idx);
> + return vq->num;
> + }
> +
> + /* If there's nothing new since last we looked, return invalid. */
> + if (vq->avail_idx == last_avail_idx)
> + return vq->num;
> +
> + /* Only get avail ring entries after they have been exposed by guest. */
> + rmb();
> +
> + /* Grab the next descriptor number they're advertising, and increment
> + * the index we've seen. */
> + if (get_user(head, &vq->avail->ring[last_avail_idx % vq->num])) {
> + vq_err(vq, "Failed to read head: idx %d address %p\n",
> + last_avail_idx,
> + &vq->avail->ring[last_avail_idx % vq->num]);
> + return vq->num;
> + }
> +
> + /* If their number is silly, that's an error. */
> + if (head >= vq->num) {
> + vq_err(vq, "Guest says index %u > %u is available",
> + head, vq->num);
> + return vq->num;
> + }
> +
> + /* When we start there are none of either input nor output. */
> + *out_num = *in_num = 0;
> + if (unlikely(log))
> + *log_num = 0;
> +
> + i = head;
> + do {
> + unsigned iov_count = *in_num + *out_num;
> + if (i >= vq->num) {
> + vq_err(vq, "Desc index is %u > %u, head = %u",
> + i, vq->num, head);
> + return vq->num;
> + }
> + if (++found > vq->num) {
> + vq_err(vq, "Loop detected: last one at %u "
> + "vq size %u head %u\n",
> + i, vq->num, head);
> + return vq->num;
> + }
> + ret = copy_from_user(&desc, vq->desc + i, sizeof desc);
> + if (ret) {
> + vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
> + i, vq->desc + i);
> + return vq->num;
> + }
> + if (desc.flags & VRING_DESC_F_INDIRECT) {
> + ret = get_indirect(dev, vq, iov, out_num, in_num,
> + log, log_num, &desc);
> + if (ret < 0) {
> + vq_err(vq, "Failure detected "
> + "in indirect descriptor at idx %d\n", i);
> + return vq->num;
> + }
> + continue;
> + }
> +
> + ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
> + VHOST_NET_MAX_SG - iov_count);
> + if (ret < 0) {
> + vq_err(vq, "Translation failure %d descriptor idx %d\n",
> + ret, i);
> + return vq->num;
> + }
> + if (desc.flags & VRING_DESC_F_WRITE) {
> + /* If this is an input descriptor, increment that count. */
> + *in_num += ret;
> + if (unlikely(log)) {
> + log[*log_num].addr = desc.addr;
> + log[*log_num].len = desc.len;
> + ++*log_num;
> + }
> + } else {
> + /* If it's an output descriptor, they're all supposed
> + * to come before any input descriptors. */
> + if (*in_num) {
> + vq_err(vq, "Descriptor has out after in: "
> + "idx %d\n", i);
> + return vq->num;
> + }
> + *out_num += ret;
> + }
> + } while ((i = next_desc(&desc)) != -1);
> +
> + /* On success, increment avail index. */
> + vq->last_avail_idx++;
> + return head;
> +}
> +
> +/* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
> +void vhost_discard_vq_desc(struct vhost_virtqueue *vq)
> +{
> + vq->last_avail_idx--;
> +}
> +
> +/* After we've used one of their buffers, we tell them about it. We'll then
> + * want to send them an interrupt, using vq->call. */
> +int vhost_add_used(struct vhost_virtqueue *vq,
> + unsigned int head, int len)
> +{
> + struct vring_used_elem *used;
> +
> + /* The virtqueue contains a ring of used buffers. Get a pointer to the
> + * next entry in that used ring. */
> + used = &vq->used->ring[vq->last_used_idx % vq->num];
> + if (put_user(head, &used->id)) {
> + vq_err(vq, "Failed to write used id");
> + return -EFAULT;
> + }
> + if (put_user(len, &used->len)) {
> + vq_err(vq, "Failed to write used len");
> + return -EFAULT;
> + }
> + /* Make sure buffer is written before we update index. */
> + wmb();
> + if (put_user(vq->last_used_idx + 1, &vq->used->idx)) {
> + vq_err(vq, "Failed to increment used idx");
> + return -EFAULT;
> + }
> + if (unlikely(vq->log_used)) {
> + /* Make sure data is seen before log. */
> + wmb();
> + log_write(vq->log_base, vq->log_addr + sizeof *vq->used->ring
> + * (vq->last_used_idx % vq->num), sizeof *vq->used->ring);
> + log_write(vq->log_base, vq->log_addr, sizeof *vq->used->ring);
> + if (vq->log_ctx)
> + eventfd_signal(vq->log_ctx, 1);
> + }
> + vq->last_used_idx++;
> + return 0;
> +}
> +
> +/* This actually sends the interrupt for this virtqueue */
> +void vhost_trigger_irq(struct vhost_dev *dev, struct vhost_virtqueue *vq)
> +{
> + __u16 flags = 0;
> + if (get_user(flags, &vq->avail->flags)) {
> + vq_err(vq, "Failed to get flags");
> + return;
> + }
> +
> + /* If they don't want an interrupt, don't send one, unless empty. */
> + if ((flags & VRING_AVAIL_F_NO_INTERRUPT) &&
> + (vq->avail_idx != vq->last_avail_idx ||
> + !vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY)))
> + return;
> +
> + /* Send the Guest an interrupt tell them we used something up. */
> + if (vq->call_ctx)
> + eventfd_signal(vq->call_ctx, 1);
> +}
> +
> +/* And here's the combo meal deal. Supersize me! */
> +void vhost_add_used_and_trigger(struct vhost_dev *dev,
> + struct vhost_virtqueue *vq,
> + unsigned int head, int len)
> +{
> + vhost_add_used(vq, head, len);
> + vhost_trigger_irq(dev, vq);
> +}
> +
> +/* OK, now we need to know about added descriptors. */
> +bool vhost_notify(struct vhost_virtqueue *vq)
> +{
> + int r;
> + if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
> + return false;
> + vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
> + r = put_user(vq->used_flags, &vq->used->flags);
> + if (r)
> + vq_err(vq, "Failed to disable notification: %d\n", r);
> + /* They could have slipped one in as we were doing that: make
> + * sure it's written, tell caller it needs to check again. */
> + mb();
> + return true;
> +}
> +
> +/* We don't need to be notified again. */
> +void vhost_no_notify(struct vhost_virtqueue *vq)
> +{
> + int r;
> + if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
> + return;
> + vq->used_flags |= VRING_USED_F_NO_NOTIFY;
> + r = put_user(vq->used_flags, &vq->used->flags);
> + if (r)
> + vq_err(vq, "Failed to enable notification: %d\n", r);
> +}
> +
> +int vhost_init(void)
> +{
> + vhost_workqueue = create_singlethread_workqueue("vhost");
> + if (!vhost_workqueue)
> + return -ENOMEM;
> + return 0;
> +}
> +
> +void vhost_cleanup(void)
> +{
> + destroy_workqueue(vhost_workqueue);
> +}
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> new file mode 100644
> index 0000000..ae66b5e
> --- /dev/null
> +++ b/drivers/vhost/vhost.h
> @@ -0,0 +1,158 @@
> +#ifndef _VHOST_H
> +#define _VHOST_H
> +
> +#include <linux/eventfd.h>
> +#include <linux/vhost.h>
> +#include <linux/mm.h>
> +#include <linux/mutex.h>
> +#include <linux/workqueue.h>
> +#include <linux/poll.h>
> +#include <linux/file.h>
> +#include <linux/skbuff.h>
> +#include <linux/uio.h>
> +#include <linux/virtio_config.h>
> +#include <linux/virtio_ring.h>
> +
> +struct vhost_device;
> +
> +enum {
> + VHOST_NET_MAX_SG = MAX_SKB_FRAGS + 2,
> +};
> +
> +/* Poll a file (eventfd or socket) */
> +/* Note: there's nothing vhost specific about this structure. */
> +struct vhost_poll {
> + poll_table table;
> + wait_queue_head_t *wqh;
> + wait_queue_t wait;
> + /* struct which will handle all actual work. */
> + struct work_struct work;
> + unsigned long mask;
> +};
> +
> +void vhost_poll_init(struct vhost_poll *poll, work_func_t func,
> + unsigned long mask);
> +void vhost_poll_start(struct vhost_poll *poll, struct file *file);
> +void vhost_poll_stop(struct vhost_poll *poll);
> +void vhost_poll_flush(struct vhost_poll *poll);
> +void vhost_poll_queue(struct vhost_poll *poll);
> +
> +struct vhost_log {
> + u64 addr;
> + u64 len;
> +};
> +
> +/* The virtqueue structure describes a queue attached to a device. */
> +struct vhost_virtqueue {
> + struct vhost_dev *dev;
> +
> + /* The actual ring of buffers. */
> + struct mutex mutex;
> + unsigned int num;
> + struct vring_desc __user *desc;
> + struct vring_avail __user *avail;
> + struct vring_used __user *used;
> + struct file *kick;
> + struct file *call;
> + struct file *error;
> + struct eventfd_ctx *call_ctx;
> + struct eventfd_ctx *error_ctx;
> + struct eventfd_ctx *log_ctx;
> +
> + struct vhost_poll poll;
> +
> + /* The routine to call when the Guest pings us, or timeout. */
> + work_func_t handle_kick;
> +
> + /* Last available index we saw. */
> + u16 last_avail_idx;
> +
> + /* Caches available index value from user. */
> + u16 avail_idx;
> +
> + /* Last index we used. */
> + u16 last_used_idx;
> +
> + /* Used flags */
> + u16 used_flags;
> +
> + /* Log writes to used structure. */
> + bool log_used;
> + u64 log_addr;
> +
> + struct iovec indirect[VHOST_NET_MAX_SG];
> + struct iovec iov[VHOST_NET_MAX_SG];
> + struct iovec hdr[VHOST_NET_MAX_SG];
> + size_t hdr_size;
> + /* We use a kind of RCU to access private pointer.
> + * All readers access it from workqueue, which makes it possible to
> + * flush the workqueue instead of synchronize_rcu. Therefore readers do
> + * not need to call rcu_read_lock/rcu_read_unlock: the beginning of
> + * work item execution acts instead of rcu_read_lock() and the end of
> + * work item execution acts instead of rcu_read_lock().
> + * Writers use virtqueue mutex. */
> + void *private_data;
> + /* Log write descriptors */
> + void __user *log_base;
> + struct vhost_log log[VHOST_NET_MAX_SG];
> +};
> +
> +struct vhost_dev {
> + /* Readers use RCU to access memory table pointer
> + * log base pointer and features.
> + * Writers use mutex below.*/
> + struct vhost_memory *memory;
> + struct mm_struct *mm;
> + struct mutex mutex;
> + unsigned acked_features;
> + struct vhost_virtqueue *vqs;
> + int nvqs;
> + struct file *log_file;
> + struct eventfd_ctx *log_ctx;
> +};
> +
> +long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue *vqs, int nvqs);
> +long vhost_dev_check_owner(struct vhost_dev *);
> +long vhost_dev_reset_owner(struct vhost_dev *);
> +void vhost_dev_cleanup(struct vhost_dev *);
> +long vhost_dev_ioctl(struct vhost_dev *, unsigned int ioctl, unsigned long arg);
> +
> +unsigned vhost_get_vq_desc(struct vhost_dev *, struct vhost_virtqueue *,
> + struct iovec iov[],
> + unsigned int *out_num, unsigned int *in_num,
> + struct vhost_log *log, unsigned int *log_num);
> +void vhost_discard_vq_desc(struct vhost_virtqueue *);
> +
> +int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len);
> +void vhost_trigger_irq(struct vhost_dev *, struct vhost_virtqueue *);
> +void vhost_add_used_and_trigger(struct vhost_dev *, struct vhost_virtqueue *,
> + unsigned int head, int len);
> +void vhost_no_notify(struct vhost_virtqueue *);
> +bool vhost_notify(struct vhost_virtqueue *);
> +
> +int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
> + unsigned int log_num, u64 len);
> +
> +int vhost_init(void);
> +void vhost_cleanup(void);
> +
> +#define vq_err(vq, fmt, ...) do { \
> + pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \
> + if ((vq)->error_ctx) \
> + eventfd_signal((vq)->error_ctx, 1);\
> + } while (0)
> +
> +enum {
> + VHOST_FEATURES = (1 << VIRTIO_F_NOTIFY_ON_EMPTY) |
> + (1 << VIRTIO_RING_F_INDIRECT_DESC) |

Line above needs more tabs.

Daniel