Merge tag 'block-5.11-2021-01-10' of git://git.kernel.dk/linux-block

[linux/fpc-iii.git] / drivers / vhost / vsock.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * vhost transport for vsock
 *
 * Copyright (C) 2013-2015 Red Hat, Inc.
 * Author: Asias He <asias@redhat.com>
 *         Stefan Hajnoczi <stefanha@redhat.com>
 */
#include <linux/miscdevice.h>
#include <linux/atomic.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/vmalloc.h>
#include <net/sock.h>
#include <linux/virtio_vsock.h>
#include <linux/vhost.h>
#include <linux/hashtable.h>

#include <net/af_vsock.h>
#include "vhost.h"

#define VHOST_VSOCK_DEFAULT_HOST_CID    2
/* Max number of bytes transferred before requeueing the job.
 * Using this limit prevents one virtqueue from starving others. */
#define VHOST_VSOCK_WEIGHT 0x80000
/* Max number of packets transferred before requeueing the job.
 * Using this limit prevents one virtqueue from starving others with
 * small pkts.
 */
#define VHOST_VSOCK_PKT_WEIGHT 256

enum {
        VHOST_VSOCK_FEATURES = VHOST_FEATURES |
                               (1ULL << VIRTIO_F_ACCESS_PLATFORM)
};

enum {
        VHOST_VSOCK_BACKEND_FEATURES = (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2)
};

/* Used to track all the vhost_vsock instances on the system. */
static DEFINE_MUTEX(vhost_vsock_mutex);
static DEFINE_READ_MOSTLY_HASHTABLE(vhost_vsock_hash, 8);

struct vhost_vsock {
        struct vhost_dev dev;
        struct vhost_virtqueue vqs[2];

        /* Link to global vhost_vsock_hash, writes use vhost_vsock_mutex */
        struct hlist_node hash;

        struct vhost_work send_pkt_work;
        spinlock_t send_pkt_list_lock;
        struct list_head send_pkt_list; /* host->guest pending packets */

        atomic_t queued_replies;

        u32 guest_cid;
};

static u32 vhost_transport_get_local_cid(void)
{
        return VHOST_VSOCK_DEFAULT_HOST_CID;
}

/* Callers that dereference the return value must hold vhost_vsock_mutex or the
 * RCU read lock.
 */
static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
{
        struct vhost_vsock *vsock;

        hash_for_each_possible_rcu(vhost_vsock_hash, vsock, hash, guest_cid) {
                u32 other_cid = vsock->guest_cid;

                /* Skip instances that have no CID yet */
                if (other_cid == 0)
                        continue;

                if (other_cid == guest_cid)
                        return vsock;

        }

        return NULL;
}

static void
vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
                            struct vhost_virtqueue *vq)
{
        struct vhost_virtqueue *tx_vq = &vsock->vqs[VSOCK_VQ_TX];
        int pkts = 0, total_len = 0;
        bool added = false;
        bool restart_tx = false;

        mutex_lock(&vq->mutex);

        if (!vhost_vq_get_backend(vq))
                goto out;

        if (!vq_meta_prefetch(vq))
                goto out;

        /* Avoid further vmexits, we're already processing the virtqueue */
        vhost_disable_notify(&vsock->dev, vq);

        do {
                struct virtio_vsock_pkt *pkt;
                struct iov_iter iov_iter;
                unsigned out, in;
                size_t nbytes;
                size_t iov_len, payload_len;
                int head;

                spin_lock_bh(&vsock->send_pkt_list_lock);
                if (list_empty(&vsock->send_pkt_list)) {
                        spin_unlock_bh(&vsock->send_pkt_list_lock);
                        vhost_enable_notify(&vsock->dev, vq);
                        break;
                }

                pkt = list_first_entry(&vsock->send_pkt_list,
                                       struct virtio_vsock_pkt, list);
                list_del_init(&pkt->list);
                spin_unlock_bh(&vsock->send_pkt_list_lock);

                head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
                                         &out, &in, NULL, NULL);
                if (head < 0) {
                        spin_lock_bh(&vsock->send_pkt_list_lock);
                        list_add(&pkt->list, &vsock->send_pkt_list);
                        spin_unlock_bh(&vsock->send_pkt_list_lock);
                        break;
                }

                if (head == vq->num) {
                        spin_lock_bh(&vsock->send_pkt_list_lock);
                        list_add(&pkt->list, &vsock->send_pkt_list);
                        spin_unlock_bh(&vsock->send_pkt_list_lock);

                        /* We cannot finish yet if more buffers snuck in while
                         * re-enabling notify.
                         */
                        if (unlikely(vhost_enable_notify(&vsock->dev, vq))) {
                                vhost_disable_notify(&vsock->dev, vq);
                                continue;
                        }
                        break;
                }

                if (out) {
                        virtio_transport_free_pkt(pkt);
                        vq_err(vq, "Expected 0 output buffers, got %u\n", out);
                        break;
                }

                iov_len = iov_length(&vq->iov[out], in);
                if (iov_len < sizeof(pkt->hdr)) {
                        virtio_transport_free_pkt(pkt);
                        vq_err(vq, "Buffer len [%zu] too small\n", iov_len);
                        break;
                }

                iov_iter_init(&iov_iter, READ, &vq->iov[out], in, iov_len);
                payload_len = pkt->len - pkt->off;

                /* If the packet is greater than the space available in the
                 * buffer, we split it using multiple buffers.
                 */
                if (payload_len > iov_len - sizeof(pkt->hdr))
                        payload_len = iov_len - sizeof(pkt->hdr);

                /* Set the correct length in the header */
                pkt->hdr.len = cpu_to_le32(payload_len);

                nbytes = copy_to_iter(&pkt->hdr, sizeof(pkt->hdr), &iov_iter);
                if (nbytes != sizeof(pkt->hdr)) {
                        virtio_transport_free_pkt(pkt);
                        vq_err(vq, "Faulted on copying pkt hdr\n");
                        break;
                }

                nbytes = copy_to_iter(pkt->buf + pkt->off, payload_len,
                                      &iov_iter);
                if (nbytes != payload_len) {
                        virtio_transport_free_pkt(pkt);
                        vq_err(vq, "Faulted on copying pkt buf\n");
                        break;
                }

                /* Deliver to monitoring devices all packets that we
                 * will transmit.
                 */
                virtio_transport_deliver_tap_pkt(pkt);

                vhost_add_used(vq, head, sizeof(pkt->hdr) + payload_len);
                added = true;

                pkt->off += payload_len;
                total_len += payload_len;

                /* If we didn't send all the payload we can requeue the packet
                 * to send it with the next available buffer.
                 */
                if (pkt->off < pkt->len) {
                        /* We are queueing the same virtio_vsock_pkt to handle
                         * the remaining bytes, and we want to deliver it
                         * to monitoring devices in the next iteration.
                         */
                        pkt->tap_delivered = false;

                        spin_lock_bh(&vsock->send_pkt_list_lock);
                        list_add(&pkt->list, &vsock->send_pkt_list);
                        spin_unlock_bh(&vsock->send_pkt_list_lock);
                } else {
                        if (pkt->reply) {
                                int val;

                                val = atomic_dec_return(&vsock->queued_replies);

                                /* Do we have resources to resume tx
                                 * processing?
                                 */
                                if (val + 1 == tx_vq->num)
                                        restart_tx = true;
                        }

                        virtio_transport_free_pkt(pkt);
                }
        } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
        if (added)
                vhost_signal(&vsock->dev, vq);

out:
        mutex_unlock(&vq->mutex);

        if (restart_tx)
                vhost_poll_queue(&tx_vq->poll);
}

static void vhost_transport_send_pkt_work(struct vhost_work *work)
{
        struct vhost_virtqueue *vq;
        struct vhost_vsock *vsock;

        vsock = container_of(work, struct vhost_vsock, send_pkt_work);
        vq = &vsock->vqs[VSOCK_VQ_RX];

        vhost_transport_do_send_pkt(vsock, vq);
}

static int
vhost_transport_send_pkt(struct virtio_vsock_pkt *pkt)
{
        struct vhost_vsock *vsock;
        int len = pkt->len;

        rcu_read_lock();

        /* Find the vhost_vsock according to guest context id  */
        vsock = vhost_vsock_get(le64_to_cpu(pkt->hdr.dst_cid));
        if (!vsock) {
                rcu_read_unlock();
                virtio_transport_free_pkt(pkt);
                return -ENODEV;
        }

        if (pkt->reply)
                atomic_inc(&vsock->queued_replies);

        spin_lock_bh(&vsock->send_pkt_list_lock);
        list_add_tail(&pkt->list, &vsock->send_pkt_list);
        spin_unlock_bh(&vsock->send_pkt_list_lock);

        vhost_work_queue(&vsock->dev, &vsock->send_pkt_work);

        rcu_read_unlock();
        return len;
}

static int
vhost_transport_cancel_pkt(struct vsock_sock *vsk)
{
        struct vhost_vsock *vsock;
        struct virtio_vsock_pkt *pkt, *n;
        int cnt = 0;
        int ret = -ENODEV;
        LIST_HEAD(freeme);

        rcu_read_lock();

        /* Find the vhost_vsock according to guest context id  */
        vsock = vhost_vsock_get(vsk->remote_addr.svm_cid);
        if (!vsock)
                goto out;

        spin_lock_bh(&vsock->send_pkt_list_lock);
        list_for_each_entry_safe(pkt, n, &vsock->send_pkt_list, list) {
                if (pkt->vsk != vsk)
                        continue;
                list_move(&pkt->list, &freeme);
        }
        spin_unlock_bh(&vsock->send_pkt_list_lock);

        list_for_each_entry_safe(pkt, n, &freeme, list) {
                if (pkt->reply)
                        cnt++;
                list_del(&pkt->list);
                virtio_transport_free_pkt(pkt);
        }

        if (cnt) {
                struct vhost_virtqueue *tx_vq = &vsock->vqs[VSOCK_VQ_TX];
                int new_cnt;

                new_cnt = atomic_sub_return(cnt, &vsock->queued_replies);
                if (new_cnt + cnt >= tx_vq->num && new_cnt < tx_vq->num)
                        vhost_poll_queue(&tx_vq->poll);
        }

        ret = 0;
out:
        rcu_read_unlock();
        return ret;
}

static struct virtio_vsock_pkt *
vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
                      unsigned int out, unsigned int in)
{
        struct virtio_vsock_pkt *pkt;
        struct iov_iter iov_iter;
        size_t nbytes;
        size_t len;

        if (in != 0) {
                vq_err(vq, "Expected 0 input buffers, got %u\n", in);
                return NULL;
        }

        pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
        if (!pkt)
                return NULL;

        len = iov_length(vq->iov, out);
        iov_iter_init(&iov_iter, WRITE, vq->iov, out, len);

        nbytes = copy_from_iter(&pkt->hdr, sizeof(pkt->hdr), &iov_iter);
        if (nbytes != sizeof(pkt->hdr)) {
                vq_err(vq, "Expected %zu bytes for pkt->hdr, got %zu bytes\n",
                       sizeof(pkt->hdr), nbytes);
                kfree(pkt);
                return NULL;
        }

        if (le16_to_cpu(pkt->hdr.type) == VIRTIO_VSOCK_TYPE_STREAM)
                pkt->len = le32_to_cpu(pkt->hdr.len);

        /* No payload */
        if (!pkt->len)
                return pkt;

        /* The pkt is too big */
        if (pkt->len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) {
                kfree(pkt);
                return NULL;
        }

        pkt->buf = kmalloc(pkt->len, GFP_KERNEL);
        if (!pkt->buf) {
                kfree(pkt);
                return NULL;
        }

        pkt->buf_len = pkt->len;

        nbytes = copy_from_iter(pkt->buf, pkt->len, &iov_iter);
        if (nbytes != pkt->len) {
                vq_err(vq, "Expected %u byte payload, got %zu bytes\n",
                       pkt->len, nbytes);
                virtio_transport_free_pkt(pkt);
                return NULL;
        }

        return pkt;
}

/* Is there space left for replies to rx packets? */
static bool vhost_vsock_more_replies(struct vhost_vsock *vsock)
{
        struct vhost_virtqueue *vq = &vsock->vqs[VSOCK_VQ_TX];
        int val;

        smp_rmb(); /* paired with atomic_inc() and atomic_dec_return() */
        val = atomic_read(&vsock->queued_replies);

        return val < vq->num;
}

static struct virtio_transport vhost_transport = {
        .transport = {
                .module                   = THIS_MODULE,

                .get_local_cid            = vhost_transport_get_local_cid,

                .init                     = virtio_transport_do_socket_init,
                .destruct                 = virtio_transport_destruct,
                .release                  = virtio_transport_release,
                .connect                  = virtio_transport_connect,
                .shutdown                 = virtio_transport_shutdown,
                .cancel_pkt               = vhost_transport_cancel_pkt,

                .dgram_enqueue            = virtio_transport_dgram_enqueue,
                .dgram_dequeue            = virtio_transport_dgram_dequeue,
                .dgram_bind               = virtio_transport_dgram_bind,
                .dgram_allow              = virtio_transport_dgram_allow,

                .stream_enqueue           = virtio_transport_stream_enqueue,
                .stream_dequeue           = virtio_transport_stream_dequeue,
                .stream_has_data          = virtio_transport_stream_has_data,
                .stream_has_space         = virtio_transport_stream_has_space,
                .stream_rcvhiwat          = virtio_transport_stream_rcvhiwat,
                .stream_is_active         = virtio_transport_stream_is_active,
                .stream_allow             = virtio_transport_stream_allow,

                .notify_poll_in           = virtio_transport_notify_poll_in,
                .notify_poll_out          = virtio_transport_notify_poll_out,
                .notify_recv_init         = virtio_transport_notify_recv_init,
                .notify_recv_pre_block    = virtio_transport_notify_recv_pre_block,
                .notify_recv_pre_dequeue  = virtio_transport_notify_recv_pre_dequeue,
                .notify_recv_post_dequeue = virtio_transport_notify_recv_post_dequeue,
                .notify_send_init         = virtio_transport_notify_send_init,
                .notify_send_pre_block    = virtio_transport_notify_send_pre_block,
                .notify_send_pre_enqueue  = virtio_transport_notify_send_pre_enqueue,
                .notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
                .notify_buffer_size       = virtio_transport_notify_buffer_size,

        },

        .send_pkt = vhost_transport_send_pkt,
};

static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
{
        struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
                                                  poll.work);
        struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
                                                 dev);
        struct virtio_vsock_pkt *pkt;
        int head, pkts = 0, total_len = 0;
        unsigned int out, in;
        bool added = false;

        mutex_lock(&vq->mutex);

        if (!vhost_vq_get_backend(vq))
                goto out;

        if (!vq_meta_prefetch(vq))
                goto out;

        vhost_disable_notify(&vsock->dev, vq);
        do {
                u32 len;

                if (!vhost_vsock_more_replies(vsock)) {
                        /* Stop tx until the device processes already
                         * pending replies.  Leave tx virtqueue
                         * callbacks disabled.
                         */
                        goto no_more_replies;
                }

                head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
                                         &out, &in, NULL, NULL);
                if (head < 0)
                        break;

                if (head == vq->num) {
                        if (unlikely(vhost_enable_notify(&vsock->dev, vq))) {
                                vhost_disable_notify(&vsock->dev, vq);
                                continue;
                        }
                        break;
                }

                pkt = vhost_vsock_alloc_pkt(vq, out, in);
                if (!pkt) {
                        vq_err(vq, "Faulted on pkt\n");
                        continue;
                }

                len = pkt->len;

                /* Deliver to monitoring devices all received packets */
                virtio_transport_deliver_tap_pkt(pkt);

                /* Only accept correctly addressed packets */
                if (le64_to_cpu(pkt->hdr.src_cid) == vsock->guest_cid &&
                    le64_to_cpu(pkt->hdr.dst_cid) ==
                    vhost_transport_get_local_cid())
                        virtio_transport_recv_pkt(&vhost_transport, pkt);
                else
                        virtio_transport_free_pkt(pkt);

                len += sizeof(pkt->hdr);
                vhost_add_used(vq, head, len);
                total_len += len;
                added = true;
        } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));

no_more_replies:
        if (added)
                vhost_signal(&vsock->dev, vq);

out:
        mutex_unlock(&vq->mutex);
}

static void vhost_vsock_handle_rx_kick(struct vhost_work *work)
{
        struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
                                                poll.work);
        struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
                                                 dev);

        vhost_transport_do_send_pkt(vsock, vq);
}

static int vhost_vsock_start(struct vhost_vsock *vsock)
{
        struct vhost_virtqueue *vq;
        size_t i;
        int ret;

        mutex_lock(&vsock->dev.mutex);

        ret = vhost_dev_check_owner(&vsock->dev);
        if (ret)
                goto err;

        for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
                vq = &vsock->vqs[i];

                mutex_lock(&vq->mutex);

                if (!vhost_vq_access_ok(vq)) {
                        ret = -EFAULT;
                        goto err_vq;
                }

                if (!vhost_vq_get_backend(vq)) {
                        vhost_vq_set_backend(vq, vsock);
                        ret = vhost_vq_init_access(vq);
                        if (ret)
                                goto err_vq;
                }

                mutex_unlock(&vq->mutex);
        }

        /* Some packets may have been queued before the device was started,
         * let's kick the send worker to send them.
         */
        vhost_work_queue(&vsock->dev, &vsock->send_pkt_work);

        mutex_unlock(&vsock->dev.mutex);
        return 0;

err_vq:
        vhost_vq_set_backend(vq, NULL);
        mutex_unlock(&vq->mutex);

        for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
                vq = &vsock->vqs[i];

                mutex_lock(&vq->mutex);
                vhost_vq_set_backend(vq, NULL);
                mutex_unlock(&vq->mutex);
        }
err:
        mutex_unlock(&vsock->dev.mutex);
        return ret;
}

static int vhost_vsock_stop(struct vhost_vsock *vsock)
{
        size_t i;
        int ret;

        mutex_lock(&vsock->dev.mutex);

        ret = vhost_dev_check_owner(&vsock->dev);
        if (ret)
                goto err;

        for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
                struct vhost_virtqueue *vq = &vsock->vqs[i];

                mutex_lock(&vq->mutex);
                vhost_vq_set_backend(vq, NULL);
                mutex_unlock(&vq->mutex);
        }

err:
        mutex_unlock(&vsock->dev.mutex);
        return ret;
}

static void vhost_vsock_free(struct vhost_vsock *vsock)
{
        kvfree(vsock);
}

static int vhost_vsock_dev_open(struct inode *inode, struct file *file)
{
        struct vhost_virtqueue **vqs;
        struct vhost_vsock *vsock;
        int ret;

        /* This struct is large and allocation could fail, fall back to vmalloc
         * if there is no other way.
         */
        vsock = kvmalloc(sizeof(*vsock), GFP_KERNEL | __GFP_RETRY_MAYFAIL);
        if (!vsock)
                return -ENOMEM;

        vqs = kmalloc_array(ARRAY_SIZE(vsock->vqs), sizeof(*vqs), GFP_KERNEL);
        if (!vqs) {
                ret = -ENOMEM;
                goto out;
        }

        vsock->guest_cid = 0; /* no CID assigned yet */

        atomic_set(&vsock->queued_replies, 0);

        vqs[VSOCK_VQ_TX] = &vsock->vqs[VSOCK_VQ_TX];
        vqs[VSOCK_VQ_RX] = &vsock->vqs[VSOCK_VQ_RX];
        vsock->vqs[VSOCK_VQ_TX].handle_kick = vhost_vsock_handle_tx_kick;
        vsock->vqs[VSOCK_VQ_RX].handle_kick = vhost_vsock_handle_rx_kick;

        vhost_dev_init(&vsock->dev, vqs, ARRAY_SIZE(vsock->vqs),
                       UIO_MAXIOV, VHOST_VSOCK_PKT_WEIGHT,
                       VHOST_VSOCK_WEIGHT, true, NULL);

        file->private_data = vsock;
        spin_lock_init(&vsock->send_pkt_list_lock);
        INIT_LIST_HEAD(&vsock->send_pkt_list);
        vhost_work_init(&vsock->send_pkt_work, vhost_transport_send_pkt_work);
        return 0;

out:
        vhost_vsock_free(vsock);
        return ret;
}

static void vhost_vsock_flush(struct vhost_vsock *vsock)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++)
                if (vsock->vqs[i].handle_kick)
                        vhost_poll_flush(&vsock->vqs[i].poll);
        vhost_work_flush(&vsock->dev, &vsock->send_pkt_work);
}

static void vhost_vsock_reset_orphans(struct sock *sk)
{
        struct vsock_sock *vsk = vsock_sk(sk);

        /* vmci_transport.c doesn't take sk_lock here either.  At least we're
         * under vsock_table_lock so the sock cannot disappear while we're
         * executing.
         */

        /* If the peer is still valid, no need to reset connection */
        if (vhost_vsock_get(vsk->remote_addr.svm_cid))
                return;

        /* If the close timeout is pending, let it expire.  This avoids races
         * with the timeout callback.
         */
        if (vsk->close_work_scheduled)
                return;

        sock_set_flag(sk, SOCK_DONE);
        vsk->peer_shutdown = SHUTDOWN_MASK;
        sk->sk_state = SS_UNCONNECTED;
        sk->sk_err = ECONNRESET;
        sk->sk_error_report(sk);
}

static int vhost_vsock_dev_release(struct inode *inode, struct file *file)
{
        struct vhost_vsock *vsock = file->private_data;

        mutex_lock(&vhost_vsock_mutex);
        if (vsock->guest_cid)
                hash_del_rcu(&vsock->hash);
        mutex_unlock(&vhost_vsock_mutex);

        /* Wait for other CPUs to finish using vsock */
        synchronize_rcu();

        /* Iterating over all connections for all CIDs to find orphans is
         * inefficient.  Room for improvement here. */
        vsock_for_each_connected_socket(vhost_vsock_reset_orphans);

        vhost_vsock_stop(vsock);
        vhost_vsock_flush(vsock);
        vhost_dev_stop(&vsock->dev);

        spin_lock_bh(&vsock->send_pkt_list_lock);
        while (!list_empty(&vsock->send_pkt_list)) {
                struct virtio_vsock_pkt *pkt;

                pkt = list_first_entry(&vsock->send_pkt_list,
                                struct virtio_vsock_pkt, list);
                list_del_init(&pkt->list);
                virtio_transport_free_pkt(pkt);
        }
        spin_unlock_bh(&vsock->send_pkt_list_lock);

        vhost_dev_cleanup(&vsock->dev);
        kfree(vsock->dev.vqs);
        vhost_vsock_free(vsock);
        return 0;
}

static int vhost_vsock_set_cid(struct vhost_vsock *vsock, u64 guest_cid)
{
        struct vhost_vsock *other;

        /* Refuse reserved CIDs */
        if (guest_cid <= VMADDR_CID_HOST ||
            guest_cid == U32_MAX)
                return -EINVAL;

        /* 64-bit CIDs are not yet supported */
        if (guest_cid > U32_MAX)
                return -EINVAL;

        /* Refuse if CID is assigned to the guest->host transport (i.e. nested
         * VM), to make the loopback work.
         */
        if (vsock_find_cid(guest_cid))
                return -EADDRINUSE;

        /* Refuse if CID is already in use */
        mutex_lock(&vhost_vsock_mutex);
        other = vhost_vsock_get(guest_cid);
        if (other && other != vsock) {
                mutex_unlock(&vhost_vsock_mutex);
                return -EADDRINUSE;
        }

        if (vsock->guest_cid)
                hash_del_rcu(&vsock->hash);

        vsock->guest_cid = guest_cid;
        hash_add_rcu(vhost_vsock_hash, &vsock->hash, vsock->guest_cid);
        mutex_unlock(&vhost_vsock_mutex);

        return 0;
}

static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
{
        struct vhost_virtqueue *vq;
        int i;

        if (features & ~VHOST_VSOCK_FEATURES)
                return -EOPNOTSUPP;

        mutex_lock(&vsock->dev.mutex);
        if ((features & (1 << VHOST_F_LOG_ALL)) &&
            !vhost_log_access_ok(&vsock->dev)) {
                goto err;
        }

        if ((features & (1ULL << VIRTIO_F_ACCESS_PLATFORM))) {
                if (vhost_init_device_iotlb(&vsock->dev, true))
                        goto err;
        }

        for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
                vq = &vsock->vqs[i];
                mutex_lock(&vq->mutex);
                vq->acked_features = features;
                mutex_unlock(&vq->mutex);
        }
        mutex_unlock(&vsock->dev.mutex);
        return 0;

err:
        mutex_unlock(&vsock->dev.mutex);
        return -EFAULT;
}

static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl,
                                  unsigned long arg)
{
        struct vhost_vsock *vsock = f->private_data;
        void __user *argp = (void __user *)arg;
        u64 guest_cid;
        u64 features;
        int start;
        int r;

        switch (ioctl) {
        case VHOST_VSOCK_SET_GUEST_CID:
                if (copy_from_user(&guest_cid, argp, sizeof(guest_cid)))
                        return -EFAULT;
                return vhost_vsock_set_cid(vsock, guest_cid);
        case VHOST_VSOCK_SET_RUNNING:
                if (copy_from_user(&start, argp, sizeof(start)))
                        return -EFAULT;
                if (start)
                        return vhost_vsock_start(vsock);
                else
                        return vhost_vsock_stop(vsock);
        case VHOST_GET_FEATURES:
                features = VHOST_VSOCK_FEATURES;
                if (copy_to_user(argp, &features, sizeof(features)))
                        return -EFAULT;
                return 0;
        case VHOST_SET_FEATURES:
                if (copy_from_user(&features, argp, sizeof(features)))
                        return -EFAULT;
                return vhost_vsock_set_features(vsock, features);
        case VHOST_GET_BACKEND_FEATURES:
                features = VHOST_VSOCK_BACKEND_FEATURES;
                if (copy_to_user(argp, &features, sizeof(features)))
                        return -EFAULT;
                return 0;
        case VHOST_SET_BACKEND_FEATURES:
                if (copy_from_user(&features, argp, sizeof(features)))
                        return -EFAULT;
                if (features & ~VHOST_VSOCK_BACKEND_FEATURES)
                        return -EOPNOTSUPP;
                vhost_set_backend_features(&vsock->dev, features);
                return 0;
        default:
                mutex_lock(&vsock->dev.mutex);
                r = vhost_dev_ioctl(&vsock->dev, ioctl, argp);
                if (r == -ENOIOCTLCMD)
                        r = vhost_vring_ioctl(&vsock->dev, ioctl, argp);
                else
                        vhost_vsock_flush(vsock);
                mutex_unlock(&vsock->dev.mutex);
                return r;
        }
}

static ssize_t vhost_vsock_chr_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
        struct file *file = iocb->ki_filp;
        struct vhost_vsock *vsock = file->private_data;
        struct vhost_dev *dev = &vsock->dev;
        int noblock = file->f_flags & O_NONBLOCK;

        return vhost_chr_read_iter(dev, to, noblock);
}

static ssize_t vhost_vsock_chr_write_iter(struct kiocb *iocb,
                                        struct iov_iter *from)
{
        struct file *file = iocb->ki_filp;
        struct vhost_vsock *vsock = file->private_data;
        struct vhost_dev *dev = &vsock->dev;

        return vhost_chr_write_iter(dev, from);
}

static __poll_t vhost_vsock_chr_poll(struct file *file, poll_table *wait)
{
        struct vhost_vsock *vsock = file->private_data;
        struct vhost_dev *dev = &vsock->dev;

        return vhost_chr_poll(file, dev, wait);
}

static const struct file_operations vhost_vsock_fops = {
        .owner          = THIS_MODULE,
        .open           = vhost_vsock_dev_open,
        .release        = vhost_vsock_dev_release,
        .llseek         = noop_llseek,
        .unlocked_ioctl = vhost_vsock_dev_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .read_iter      = vhost_vsock_chr_read_iter,
        .write_iter     = vhost_vsock_chr_write_iter,
        .poll           = vhost_vsock_chr_poll,
};

static struct miscdevice vhost_vsock_misc = {
        .minor = VHOST_VSOCK_MINOR,
        .name = "vhost-vsock",
        .fops = &vhost_vsock_fops,
};

static int __init vhost_vsock_init(void)
{
        int ret;

        ret = vsock_core_register(&vhost_transport.transport,
                                  VSOCK_TRANSPORT_F_H2G);
        if (ret < 0)
                return ret;
        return misc_register(&vhost_vsock_misc);
};

static void __exit vhost_vsock_exit(void)
{
        misc_deregister(&vhost_vsock_misc);
        vsock_core_unregister(&vhost_transport.transport);
};

module_init(vhost_vsock_init);
module_exit(vhost_vsock_exit);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Asias He");
MODULE_DESCRIPTION("vhost transport for vsock ");
MODULE_ALIAS_MISCDEV(VHOST_VSOCK_MINOR);
MODULE_ALIAS("devname:vhost-vsock");