// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * (c) 2017 Stefano Stabellini <stefano@aporeto.com>
 */

#include <linux/inet.h>
#include <linux/kthread.h>
#include <linux/list.h>
#include <linux/radix-tree.h>
#include <linux/module.h>
#include <linux/semaphore.h>
#include <linux/wait.h>
#include <net/sock.h>
#include <net/inet_common.h>
#include <net/inet_connection_sock.h>
#include <net/request_sock.h>

#include <xen/events.h>
#include <xen/grant_table.h>
#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/interface/io/pvcalls.h>

#define PVCALLS_VERSIONS "1"
#define MAX_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER

static struct pvcalls_back_global {
        struct list_head frontends;
        struct semaphore frontends_lock;
} pvcalls_back_global;

/*
 * Per-frontend data structure. It contains pointers to the command
 * ring, its event channel, a list of active sockets and a tree of
 * passive sockets.
 */
struct pvcalls_fedata {
        struct list_head list;
        struct xenbus_device *dev;
        struct xen_pvcalls_sring *sring;
        struct xen_pvcalls_back_ring ring;
        int irq;
        struct list_head socket_mappings;
        struct radix_tree_root socketpass_mappings;
        struct semaphore socket_lock;
};

struct pvcalls_ioworker {
        struct work_struct register_work;
        struct workqueue_struct *wq;
};

struct sock_mapping {
        struct list_head list;
        struct pvcalls_fedata *fedata;
        struct sockpass_mapping *sockpass;
        struct socket *sock;
        uint64_t id;
        grant_ref_t ref;
        struct pvcalls_data_intf *ring;
        void *bytes;
        struct pvcalls_data data;
        uint32_t ring_order;
        int irq;
        atomic_t read;
        atomic_t write;
        atomic_t io;
        atomic_t release;
        atomic_t eoi;
        void (*saved_data_ready)(struct sock *sk);
        struct pvcalls_ioworker ioworker;
};

struct sockpass_mapping {
        struct list_head list;
        struct pvcalls_fedata *fedata;
        struct socket *sock;
        uint64_t id;
        struct xen_pvcalls_request reqcopy;
        spinlock_t copy_lock;
        struct workqueue_struct *wq;
        struct work_struct register_work;
        void (*saved_data_ready)(struct sock *sk);
};

static irqreturn_t pvcalls_back_conn_event(int irq, void *sock_map);
static int pvcalls_back_release_active(struct xenbus_device *dev,
                                       struct pvcalls_fedata *fedata,
                                       struct sock_mapping *map);

static bool pvcalls_conn_back_read(void *opaque)
{
        struct sock_mapping *map = (struct sock_mapping *)opaque;
        struct msghdr msg;
        struct kvec vec[2];
        RING_IDX cons, prod, size, wanted, array_size, masked_prod, masked_cons;
        int32_t error;
        struct pvcalls_data_intf *intf = map->ring;
        struct pvcalls_data *data = &map->data;
        unsigned long flags;
        int ret;

        array_size = XEN_FLEX_RING_SIZE(map->ring_order);
        cons = intf->in_cons;
        prod = intf->in_prod;
        error = intf->in_error;
        /* read the indexes first, then deal with the data */
        virt_mb();

        if (error)
                return false;

        size = pvcalls_queued(prod, cons, array_size);
        if (size >= array_size)
                return false;
        spin_lock_irqsave(&map->sock->sk->sk_receive_queue.lock, flags);
        if (skb_queue_empty(&map->sock->sk->sk_receive_queue)) {
                atomic_set(&map->read, 0);
                spin_unlock_irqrestore(&map->sock->sk->sk_receive_queue.lock,
                                flags);
                return true;
        }
        spin_unlock_irqrestore(&map->sock->sk->sk_receive_queue.lock, flags);
        wanted = array_size - size;
        masked_prod = pvcalls_mask(prod, array_size);
        masked_cons = pvcalls_mask(cons, array_size);

        memset(&msg, 0, sizeof(msg));
        if (masked_prod < masked_cons) {
                vec[0].iov_base = data->in + masked_prod;
                vec[0].iov_len = wanted;
                iov_iter_kvec(&msg.msg_iter, WRITE, vec, 1, wanted);
        } else {
                vec[0].iov_base = data->in + masked_prod;
                vec[0].iov_len = array_size - masked_prod;
                vec[1].iov_base = data->in;
                vec[1].iov_len = wanted - vec[0].iov_len;
                iov_iter_kvec(&msg.msg_iter, WRITE, vec, 2, wanted);
        }

        atomic_set(&map->read, 0);
        ret = inet_recvmsg(map->sock, &msg, wanted, MSG_DONTWAIT);
        WARN_ON(ret > wanted);
        if (ret == -EAGAIN) /* shouldn't happen */
                return true;
        if (!ret)
                ret = -ENOTCONN;
        spin_lock_irqsave(&map->sock->sk->sk_receive_queue.lock, flags);
        if (ret > 0 && !skb_queue_empty(&map->sock->sk->sk_receive_queue))
                atomic_inc(&map->read);
        spin_unlock_irqrestore(&map->sock->sk->sk_receive_queue.lock, flags);

        /* write the data, then modify the indexes */
        virt_wmb();
        if (ret < 0) {
                atomic_set(&map->read, 0);
                intf->in_error = ret;
        } else
                intf->in_prod = prod + ret;
        /* update the indexes, then notify the other end */
        virt_wmb();
        notify_remote_via_irq(map->irq);

        return true;
}

static bool pvcalls_conn_back_write(struct sock_mapping *map)
{
        struct pvcalls_data_intf *intf = map->ring;
        struct pvcalls_data *data = &map->data;
        struct msghdr msg;
        struct kvec vec[2];
        RING_IDX cons, prod, size, array_size;
        int ret;

        cons = intf->out_cons;
        prod = intf->out_prod;
        /* read the indexes before dealing with the data */
        virt_mb();

        array_size = XEN_FLEX_RING_SIZE(map->ring_order);
        size = pvcalls_queued(prod, cons, array_size);
        if (size == 0)
                return false;

        memset(&msg, 0, sizeof(msg));
        msg.msg_flags |= MSG_DONTWAIT;
        if (pvcalls_mask(prod, array_size) > pvcalls_mask(cons, array_size)) {
                vec[0].iov_base = data->out + pvcalls_mask(cons, array_size);
                vec[0].iov_len = size;
                iov_iter_kvec(&msg.msg_iter, READ, vec, 1, size);
        } else {
                vec[0].iov_base = data->out + pvcalls_mask(cons, array_size);
                vec[0].iov_len = array_size - pvcalls_mask(cons, array_size);
                vec[1].iov_base = data->out;
                vec[1].iov_len = size - vec[0].iov_len;
                iov_iter_kvec(&msg.msg_iter, READ, vec, 2, size);
        }

        atomic_set(&map->write, 0);
        ret = inet_sendmsg(map->sock, &msg, size);
        if (ret == -EAGAIN) {
                atomic_inc(&map->write);
                atomic_inc(&map->io);
                return true;
        }

        /* write the data, then update the indexes */
        virt_wmb();
        if (ret < 0) {
                intf->out_error = ret;
        } else {
                intf->out_error = 0;
                intf->out_cons = cons + ret;
                prod = intf->out_prod;
        }
        /* update the indexes, then notify the other end */
        virt_wmb();
        if (prod != cons + ret) {
                atomic_inc(&map->write);
                atomic_inc(&map->io);
        }
        notify_remote_via_irq(map->irq);

        return true;
}

static void pvcalls_back_ioworker(struct work_struct *work)
{
        struct pvcalls_ioworker *ioworker = container_of(work,
                struct pvcalls_ioworker, register_work);
        struct sock_mapping *map = container_of(ioworker, struct sock_mapping,
                ioworker);
        unsigned int eoi_flags = XEN_EOI_FLAG_SPURIOUS;

        while (atomic_read(&map->io) > 0) {
                if (atomic_read(&map->release) > 0) {
                        atomic_set(&map->release, 0);
                        return;
                }

                if (atomic_read(&map->read) > 0 &&
                    pvcalls_conn_back_read(map))
                        eoi_flags = 0;
                if (atomic_read(&map->write) > 0 &&
                    pvcalls_conn_back_write(map))
                        eoi_flags = 0;

                if (atomic_read(&map->eoi) > 0 && !atomic_read(&map->write)) {
                        atomic_set(&map->eoi, 0);
                        xen_irq_lateeoi(map->irq, eoi_flags);
                        eoi_flags = XEN_EOI_FLAG_SPURIOUS;
                }

                atomic_dec(&map->io);
        }
}

static int pvcalls_back_socket(struct xenbus_device *dev,
                struct xen_pvcalls_request *req)
{
        struct pvcalls_fedata *fedata;
        int ret;
        struct xen_pvcalls_response *rsp;

        fedata = dev_get_drvdata(&dev->dev);

        if (req->u.socket.domain != AF_INET ||
            req->u.socket.type != SOCK_STREAM ||
            (req->u.socket.protocol != IPPROTO_IP &&
             req->u.socket.protocol != AF_INET))
                ret = -EAFNOSUPPORT;
        else
                ret = 0;

        /* leave the actual socket allocation for later */

        rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
        rsp->req_id = req->req_id;
        rsp->cmd = req->cmd;
        rsp->u.socket.id = req->u.socket.id;
        rsp->ret = ret;

        return 0;
}

static void pvcalls_sk_state_change(struct sock *sock)
{
        struct sock_mapping *map = sock->sk_user_data;

        if (map == NULL)
                return;

        atomic_inc(&map->read);
        notify_remote_via_irq(map->irq);
}

static void pvcalls_sk_data_ready(struct sock *sock)
{
        struct sock_mapping *map = sock->sk_user_data;
        struct pvcalls_ioworker *iow;

        if (map == NULL)
                return;

        iow = &map->ioworker;
        atomic_inc(&map->read);
        atomic_inc(&map->io);
        queue_work(iow->wq, &iow->register_work);
}

static struct sock_mapping *pvcalls_new_active_socket(
                struct pvcalls_fedata *fedata,
                uint64_t id,
                grant_ref_t ref,
                evtchn_port_t evtchn,
                struct socket *sock)
{
        int ret;
        struct sock_mapping *map;
        void *page;

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

        map->fedata = fedata;
        map->sock = sock;
        map->id = id;
        map->ref = ref;

        ret = xenbus_map_ring_valloc(fedata->dev, &ref, 1, &page);
        if (ret < 0)
                goto out;
        map->ring = page;
        map->ring_order = map->ring->ring_order;
        /* first read the order, then map the data ring */
        virt_rmb();
        if (map->ring_order > MAX_RING_ORDER) {
                pr_warn("%s frontend requested ring_order %u, which is > MAX (%u)\n",
                                __func__, map->ring_order, MAX_RING_ORDER);
                goto out;
        }
        ret = xenbus_map_ring_valloc(fedata->dev, map->ring->ref,
                                     (1 << map->ring_order), &page);
        if (ret < 0)
                goto out;
        map->bytes = page;

        ret = bind_interdomain_evtchn_to_irqhandler_lateeoi(
                        fedata->dev, evtchn,
                        pvcalls_back_conn_event, 0, "pvcalls-backend", map);
        if (ret < 0)
                goto out;
        map->irq = ret;

        map->data.in = map->bytes;
        map->data.out = map->bytes + XEN_FLEX_RING_SIZE(map->ring_order);

        map->ioworker.wq = alloc_workqueue("pvcalls_io", WQ_UNBOUND, 1);
        if (!map->ioworker.wq)
                goto out;
        atomic_set(&map->io, 1);
        INIT_WORK(&map->ioworker.register_work, pvcalls_back_ioworker);

        down(&fedata->socket_lock);
        list_add_tail(&map->list, &fedata->socket_mappings);
        up(&fedata->socket_lock);

        write_lock_bh(&map->sock->sk->sk_callback_lock);
        map->saved_data_ready = map->sock->sk->sk_data_ready;
        map->sock->sk->sk_user_data = map;
        map->sock->sk->sk_data_ready = pvcalls_sk_data_ready;
        map->sock->sk->sk_state_change = pvcalls_sk_state_change;
        write_unlock_bh(&map->sock->sk->sk_callback_lock);

        return map;
out:
        down(&fedata->socket_lock);
        list_del(&map->list);
        pvcalls_back_release_active(fedata->dev, fedata, map);
        up(&fedata->socket_lock);
        return NULL;
}

static int pvcalls_back_connect(struct xenbus_device *dev,
                                struct xen_pvcalls_request *req)
{
        struct pvcalls_fedata *fedata;
        int ret = -EINVAL;
        struct socket *sock;
        struct sock_mapping *map;
        struct xen_pvcalls_response *rsp;
        struct sockaddr *sa = (struct sockaddr *)&req->u.connect.addr;

        fedata = dev_get_drvdata(&dev->dev);

        if (req->u.connect.len < sizeof(sa->sa_family) ||
            req->u.connect.len > sizeof(req->u.connect.addr) ||
            sa->sa_family != AF_INET)
                goto out;

        ret = sock_create(AF_INET, SOCK_STREAM, 0, &sock);
        if (ret < 0)
                goto out;
        ret = inet_stream_connect(sock, sa, req->u.connect.len, 0);
        if (ret < 0) {
                sock_release(sock);
                goto out;
        }

        map = pvcalls_new_active_socket(fedata,
                                        req->u.connect.id,
                                        req->u.connect.ref,
                                        req->u.connect.evtchn,
                                        sock);
        if (!map) {
                ret = -EFAULT;
                sock_release(sock);
        }

out:
        rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
        rsp->req_id = req->req_id;
        rsp->cmd = req->cmd;
        rsp->u.connect.id = req->u.connect.id;
        rsp->ret = ret;

        return 0;
}

static int pvcalls_back_release_active(struct xenbus_device *dev,
                                       struct pvcalls_fedata *fedata,
                                       struct sock_mapping *map)
{
        disable_irq(map->irq);
        if (map->sock->sk != NULL) {
                write_lock_bh(&map->sock->sk->sk_callback_lock);
                map->sock->sk->sk_user_data = NULL;
                map->sock->sk->sk_data_ready = map->saved_data_ready;
                write_unlock_bh(&map->sock->sk->sk_callback_lock);
        }

        atomic_set(&map->release, 1);
        flush_work(&map->ioworker.register_work);

        xenbus_unmap_ring_vfree(dev, map->bytes);
        xenbus_unmap_ring_vfree(dev, (void *)map->ring);
        unbind_from_irqhandler(map->irq, map);

        sock_release(map->sock);
        kfree(map);

        return 0;
}

static int pvcalls_back_release_passive(struct xenbus_device *dev,
                                        struct pvcalls_fedata *fedata,
                                        struct sockpass_mapping *mappass)
{
        if (mappass->sock->sk != NULL) {
                write_lock_bh(&mappass->sock->sk->sk_callback_lock);
                mappass->sock->sk->sk_user_data = NULL;
                mappass->sock->sk->sk_data_ready = mappass->saved_data_ready;
                write_unlock_bh(&mappass->sock->sk->sk_callback_lock);
        }
        sock_release(mappass->sock);
        flush_workqueue(mappass->wq);
        destroy_workqueue(mappass->wq);
        kfree(mappass);

        return 0;
}

static int pvcalls_back_release(struct xenbus_device *dev,
                                struct xen_pvcalls_request *req)
{
        struct pvcalls_fedata *fedata;
        struct sock_mapping *map, *n;
        struct sockpass_mapping *mappass;
        int ret = 0;
        struct xen_pvcalls_response *rsp;

        fedata = dev_get_drvdata(&dev->dev);

        down(&fedata->socket_lock);
        list_for_each_entry_safe(map, n, &fedata->socket_mappings, list) {
                if (map->id == req->u.release.id) {
                        list_del(&map->list);
                        up(&fedata->socket_lock);
                        ret = pvcalls_back_release_active(dev, fedata, map);
                        goto out;
                }
        }
        mappass = radix_tree_lookup(&fedata->socketpass_mappings,
                                    req->u.release.id);
        if (mappass != NULL) {
                radix_tree_delete(&fedata->socketpass_mappings, mappass->id);
                up(&fedata->socket_lock);
                ret = pvcalls_back_release_passive(dev, fedata, mappass);
        } else
                up(&fedata->socket_lock);

out:
        rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
        rsp->req_id = req->req_id;
        rsp->u.release.id = req->u.release.id;
        rsp->cmd = req->cmd;
        rsp->ret = ret;
        return 0;
}

static void __pvcalls_back_accept(struct work_struct *work)
{
        struct sockpass_mapping *mappass = container_of(
                work, struct sockpass_mapping, register_work);
        struct sock_mapping *map;
        struct pvcalls_ioworker *iow;
        struct pvcalls_fedata *fedata;
        struct socket *sock;
        struct xen_pvcalls_response *rsp;
        struct xen_pvcalls_request *req;
        int notify;
        int ret = -EINVAL;
        unsigned long flags;

        fedata = mappass->fedata;
        /*
         * __pvcalls_back_accept can race against pvcalls_back_accept.
         * We only need to check the value of "cmd" on read. It could be
         * done atomically, but to simplify the code on the write side, we
         * use a spinlock.
         */
        spin_lock_irqsave(&mappass->copy_lock, flags);
        req = &mappass->reqcopy;
        if (req->cmd != PVCALLS_ACCEPT) {
                spin_unlock_irqrestore(&mappass->copy_lock, flags);
                return;
        }
        spin_unlock_irqrestore(&mappass->copy_lock, flags);

        sock = sock_alloc();
        if (sock == NULL)
                goto out_error;
        sock->type = mappass->sock->type;
        sock->ops = mappass->sock->ops;

        ret = inet_accept(mappass->sock, sock, O_NONBLOCK, true);
        if (ret == -EAGAIN) {
                sock_release(sock);
                return;
        }

        map = pvcalls_new_active_socket(fedata,
                                        req->u.accept.id_new,
                                        req->u.accept.ref,
                                        req->u.accept.evtchn,
                                        sock);
        if (!map) {
                ret = -EFAULT;
                sock_release(sock);
                goto out_error;
        }

        map->sockpass = mappass;
        iow = &map->ioworker;
        atomic_inc(&map->read);
        atomic_inc(&map->io);
        queue_work(iow->wq, &iow->register_work);

out_error:
        rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
        rsp->req_id = req->req_id;
        rsp->cmd = req->cmd;
        rsp->u.accept.id = req->u.accept.id;
        rsp->ret = ret;
        RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&fedata->ring, notify);
        if (notify)
                notify_remote_via_irq(fedata->irq);

        mappass->reqcopy.cmd = 0;
}

static void pvcalls_pass_sk_data_ready(struct sock *sock)
{
        struct sockpass_mapping *mappass = sock->sk_user_data;
        struct pvcalls_fedata *fedata;
        struct xen_pvcalls_response *rsp;
        unsigned long flags;
        int notify;

        if (mappass == NULL)
                return;

        fedata = mappass->fedata;
        spin_lock_irqsave(&mappass->copy_lock, flags);
        if (mappass->reqcopy.cmd == PVCALLS_POLL) {
                rsp = RING_GET_RESPONSE(&fedata->ring,
                                        fedata->ring.rsp_prod_pvt++);
                rsp->req_id = mappass->reqcopy.req_id;
                rsp->u.poll.id = mappass->reqcopy.u.poll.id;
                rsp->cmd = mappass->reqcopy.cmd;
                rsp->ret = 0;

                mappass->reqcopy.cmd = 0;
                spin_unlock_irqrestore(&mappass->copy_lock, flags);

                RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&fedata->ring, notify);
                if (notify)
                        notify_remote_via_irq(mappass->fedata->irq);
        } else {
                spin_unlock_irqrestore(&mappass->copy_lock, flags);
                queue_work(mappass->wq, &mappass->register_work);
        }
}

static int pvcalls_back_bind(struct xenbus_device *dev,
                             struct xen_pvcalls_request *req)
{
        struct pvcalls_fedata *fedata;
        int ret;
        struct sockpass_mapping *map;
        struct xen_pvcalls_response *rsp;

        fedata = dev_get_drvdata(&dev->dev);

        map = kzalloc(sizeof(*map), GFP_KERNEL);
        if (map == NULL) {
                ret = -ENOMEM;
                goto out;
        }

        INIT_WORK(&map->register_work, __pvcalls_back_accept);
        spin_lock_init(&map->copy_lock);
        map->wq = alloc_workqueue("pvcalls_wq", WQ_UNBOUND, 1);
        if (!map->wq) {
                ret = -ENOMEM;
                goto out;
        }

        ret = sock_create(AF_INET, SOCK_STREAM, 0, &map->sock);
        if (ret < 0)
                goto out;

        ret = inet_bind(map->sock, (struct sockaddr *)&req->u.bind.addr,
                        req->u.bind.len);
        if (ret < 0)
                goto out;

        map->fedata = fedata;
        map->id = req->u.bind.id;

        down(&fedata->socket_lock);
        ret = radix_tree_insert(&fedata->socketpass_mappings, map->id,
                                map);
        up(&fedata->socket_lock);
        if (ret)
                goto out;

        write_lock_bh(&map->sock->sk->sk_callback_lock);
        map->saved_data_ready = map->sock->sk->sk_data_ready;
        map->sock->sk->sk_user_data = map;
        map->sock->sk->sk_data_ready = pvcalls_pass_sk_data_ready;
        write_unlock_bh(&map->sock->sk->sk_callback_lock);

out:
        if (ret) {
                if (map && map->sock)
                        sock_release(map->sock);
                if (map && map->wq)
                        destroy_workqueue(map->wq);
                kfree(map);
        }
        rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
        rsp->req_id = req->req_id;
        rsp->cmd = req->cmd;
        rsp->u.bind.id = req->u.bind.id;
        rsp->ret = ret;
        return 0;
}

static int pvcalls_back_listen(struct xenbus_device *dev,
                               struct xen_pvcalls_request *req)
{
        struct pvcalls_fedata *fedata;
        int ret = -EINVAL;
        struct sockpass_mapping *map;
        struct xen_pvcalls_response *rsp;

        fedata = dev_get_drvdata(&dev->dev);

        down(&fedata->socket_lock);
        map = radix_tree_lookup(&fedata->socketpass_mappings, req->u.listen.id);
        up(&fedata->socket_lock);
        if (map == NULL)
                goto out;

        ret = inet_listen(map->sock, req->u.listen.backlog);

out:
        rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
        rsp->req_id = req->req_id;
        rsp->cmd = req->cmd;
        rsp->u.listen.id = req->u.listen.id;
        rsp->ret = ret;
        return 0;
}

static int pvcalls_back_accept(struct xenbus_device *dev,
                               struct xen_pvcalls_request *req)
{
        struct pvcalls_fedata *fedata;
        struct sockpass_mapping *mappass;
        int ret = -EINVAL;
        struct xen_pvcalls_response *rsp;
        unsigned long flags;

        fedata = dev_get_drvdata(&dev->dev);

        down(&fedata->socket_lock);
        mappass = radix_tree_lookup(&fedata->socketpass_mappings,
                req->u.accept.id);
        up(&fedata->socket_lock);
        if (mappass == NULL)
                goto out_error;

        /*
         * Limitation of the current implementation: only support one
         * concurrent accept or poll call on one socket.
         */
        spin_lock_irqsave(&mappass->copy_lock, flags);
        if (mappass->reqcopy.cmd != 0) {
                spin_unlock_irqrestore(&mappass->copy_lock, flags);
                ret = -EINTR;
                goto out_error;
        }

        mappass->reqcopy = *req;
        spin_unlock_irqrestore(&mappass->copy_lock, flags);
        queue_work(mappass->wq, &mappass->register_work);

        /* Tell the caller we don't need to send back a notification yet */
        return -1;

out_error:
        rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
        rsp->req_id = req->req_id;
        rsp->cmd = req->cmd;
        rsp->u.accept.id = req->u.accept.id;
        rsp->ret = ret;
        return 0;
}

static int pvcalls_back_poll(struct xenbus_device *dev,
                             struct xen_pvcalls_request *req)
{
        struct pvcalls_fedata *fedata;
        struct sockpass_mapping *mappass;
        struct xen_pvcalls_response *rsp;
        struct inet_connection_sock *icsk;
        struct request_sock_queue *queue;
        unsigned long flags;
        int ret;
        bool data;

        fedata = dev_get_drvdata(&dev->dev);

        down(&fedata->socket_lock);
        mappass = radix_tree_lookup(&fedata->socketpass_mappings,
                                    req->u.poll.id);
        up(&fedata->socket_lock);
        if (mappass == NULL)
                return -EINVAL;

        /*
         * Limitation of the current implementation: only support one
         * concurrent accept or poll call on one socket.
         */
        spin_lock_irqsave(&mappass->copy_lock, flags);
        if (mappass->reqcopy.cmd != 0) {
                ret = -EINTR;
                goto out;
        }

        mappass->reqcopy = *req;
        icsk = inet_csk(mappass->sock->sk);
        queue = &icsk->icsk_accept_queue;
        data = READ_ONCE(queue->rskq_accept_head) != NULL;
        if (data) {
                mappass->reqcopy.cmd = 0;
                ret = 0;
                goto out;
        }
        spin_unlock_irqrestore(&mappass->copy_lock, flags);

        /* Tell the caller we don't need to send back a notification yet */
        return -1;

out:
        spin_unlock_irqrestore(&mappass->copy_lock, flags);

        rsp = RING_GET_RESPONSE(&fedata->ring, fedata->ring.rsp_prod_pvt++);
        rsp->req_id = req->req_id;
        rsp->cmd = req->cmd;
        rsp->u.poll.id = req->u.poll.id;
        rsp->ret = ret;
        return 0;
}

static int pvcalls_back_handle_cmd(struct xenbus_device *dev,
                                   struct xen_pvcalls_request *req)
{
        int ret = 0;

        switch (req->cmd) {
        case PVCALLS_SOCKET:
                ret = pvcalls_back_socket(dev, req);
                break;
        case PVCALLS_CONNECT:
                ret = pvcalls_back_connect(dev, req);
                break;
        case PVCALLS_RELEASE:
                ret = pvcalls_back_release(dev, req);
                break;
        case PVCALLS_BIND:
                ret = pvcalls_back_bind(dev, req);
                break;
        case PVCALLS_LISTEN:
                ret = pvcalls_back_listen(dev, req);
                break;
        case PVCALLS_ACCEPT:
                ret = pvcalls_back_accept(dev, req);
                break;
        case PVCALLS_POLL:
                ret = pvcalls_back_poll(dev, req);
                break;
        default:
        {
                struct pvcalls_fedata *fedata;
                struct xen_pvcalls_response *rsp;

                fedata = dev_get_drvdata(&dev->dev);
                rsp = RING_GET_RESPONSE(
                                &fedata->ring, fedata->ring.rsp_prod_pvt++);
                rsp->req_id = req->req_id;
                rsp->cmd = req->cmd;
                rsp->ret = -ENOTSUPP;
                break;
        }
        }
        return ret;
}

static void pvcalls_back_work(struct pvcalls_fedata *fedata)
{
        int notify, notify_all = 0, more = 1;
        struct xen_pvcalls_request req;
        struct xenbus_device *dev = fedata->dev;

        while (more) {
                while (RING_HAS_UNCONSUMED_REQUESTS(&fedata->ring)) {
                        RING_COPY_REQUEST(&fedata->ring,
                                          fedata->ring.req_cons++,
                                          &req);

                        if (!pvcalls_back_handle_cmd(dev, &req)) {
                                RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(
                                        &fedata->ring, notify);
                                notify_all += notify;
                        }
                }

                if (notify_all) {
                        notify_remote_via_irq(fedata->irq);
                        notify_all = 0;
                }

                RING_FINAL_CHECK_FOR_REQUESTS(&fedata->ring, more);
        }
}

static irqreturn_t pvcalls_back_event(int irq, void *dev_id)
{
        struct xenbus_device *dev = dev_id;
        struct pvcalls_fedata *fedata = NULL;
        unsigned int eoi_flags = XEN_EOI_FLAG_SPURIOUS;

        if (dev) {
                fedata = dev_get_drvdata(&dev->dev);
                if (fedata) {
                        pvcalls_back_work(fedata);
                        eoi_flags = 0;
                }
        }

        xen_irq_lateeoi(irq, eoi_flags);

        return IRQ_HANDLED;
}

static irqreturn_t pvcalls_back_conn_event(int irq, void *sock_map)
{
        struct sock_mapping *map = sock_map;
        struct pvcalls_ioworker *iow;

        if (map == NULL || map->sock == NULL || map->sock->sk == NULL ||
                map->sock->sk->sk_user_data != map) {
                xen_irq_lateeoi(irq, 0);
                return IRQ_HANDLED;
        }

        iow = &map->ioworker;

        atomic_inc(&map->write);
        atomic_inc(&map->eoi);
        atomic_inc(&map->io);
        queue_work(iow->wq, &iow->register_work);

        return IRQ_HANDLED;
}

static int backend_connect(struct xenbus_device *dev)
{
        int err;
        evtchn_port_t evtchn;
        grant_ref_t ring_ref;
        struct pvcalls_fedata *fedata = NULL;

        fedata = kzalloc(sizeof(struct pvcalls_fedata), GFP_KERNEL);
        if (!fedata)
                return -ENOMEM;

        fedata->irq = -1;
        err = xenbus_scanf(XBT_NIL, dev->otherend, "port", "%u",
                           &evtchn);
        if (err != 1) {
                err = -EINVAL;
                xenbus_dev_fatal(dev, err, "reading %s/event-channel",
                                 dev->otherend);
                goto error;
        }

        err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-ref", "%u", &ring_ref);
        if (err != 1) {
                err = -EINVAL;
                xenbus_dev_fatal(dev, err, "reading %s/ring-ref",
                                 dev->otherend);
                goto error;
        }

        err = bind_interdomain_evtchn_to_irq_lateeoi(dev, evtchn);
        if (err < 0)
                goto error;
        fedata->irq = err;

        err = request_threaded_irq(fedata->irq, NULL, pvcalls_back_event,
                                   IRQF_ONESHOT, "pvcalls-back", dev);
        if (err < 0)
                goto error;

        err = xenbus_map_ring_valloc(dev, &ring_ref, 1,
                                     (void **)&fedata->sring);
        if (err < 0)
                goto error;

        BACK_RING_INIT(&fedata->ring, fedata->sring, XEN_PAGE_SIZE * 1);
        fedata->dev = dev;

        INIT_LIST_HEAD(&fedata->socket_mappings);
        INIT_RADIX_TREE(&fedata->socketpass_mappings, GFP_KERNEL);
        sema_init(&fedata->socket_lock, 1);
        dev_set_drvdata(&dev->dev, fedata);

        down(&pvcalls_back_global.frontends_lock);
        list_add_tail(&fedata->list, &pvcalls_back_global.frontends);
        up(&pvcalls_back_global.frontends_lock);

        return 0;

 error:
        if (fedata->irq >= 0)
                unbind_from_irqhandler(fedata->irq, dev);
        if (fedata->sring != NULL)
                xenbus_unmap_ring_vfree(dev, fedata->sring);
        kfree(fedata);
        return err;
}

static int backend_disconnect(struct xenbus_device *dev)
{
        struct pvcalls_fedata *fedata;
        struct sock_mapping *map, *n;
        struct sockpass_mapping *mappass;
        struct radix_tree_iter iter;
        void **slot;


        fedata = dev_get_drvdata(&dev->dev);

        down(&fedata->socket_lock);

        list_for_each_entry_safe(map, n, &fedata->socket_mappings, list) {
                list_del(&map->list);
                pvcalls_back_release_active(dev, fedata, map);
        }

        radix_tree_for_each_slot(slot, &fedata->socketpass_mappings, &iter, 0) {
                mappass = radix_tree_deref_slot(slot);
                if (!mappass)
                        continue;
                if (radix_tree_exception(mappass)) {
                        if (radix_tree_deref_retry(mappass))
                                slot = radix_tree_iter_retry(&iter);
                } else {
                        radix_tree_delete(&fedata->socketpass_mappings,
                                          mappass->id);
                        pvcalls_back_release_passive(dev, fedata, mappass);
                }
        }
        up(&fedata->socket_lock);

        unbind_from_irqhandler(fedata->irq, dev);
        xenbus_unmap_ring_vfree(dev, fedata->sring);

        list_del(&fedata->list);
        kfree(fedata);
        dev_set_drvdata(&dev->dev, NULL);

        return 0;
}

static int pvcalls_back_probe(struct xenbus_device *dev,
                              const struct xenbus_device_id *id)
{
        int err, abort;
        struct xenbus_transaction xbt;

again:
        abort = 1;

        err = xenbus_transaction_start(&xbt);
        if (err) {
                pr_warn("%s cannot create xenstore transaction\n", __func__);
                return err;
        }

        err = xenbus_printf(xbt, dev->nodename, "versions", "%s",
                            PVCALLS_VERSIONS);
        if (err) {
                pr_warn("%s write out 'versions' failed\n", __func__);
                goto abort;
        }

        err = xenbus_printf(xbt, dev->nodename, "max-page-order", "%u",
                            MAX_RING_ORDER);
        if (err) {
                pr_warn("%s write out 'max-page-order' failed\n", __func__);
                goto abort;
        }

        err = xenbus_printf(xbt, dev->nodename, "function-calls",
                            XENBUS_FUNCTIONS_CALLS);
        if (err) {
                pr_warn("%s write out 'function-calls' failed\n", __func__);
                goto abort;
        }

        abort = 0;
abort:
        err = xenbus_transaction_end(xbt, abort);
        if (err) {
                if (err == -EAGAIN && !abort)
                        goto again;
                pr_warn("%s cannot complete xenstore transaction\n", __func__);
                return err;
        }

        if (abort)
                return -EFAULT;

        xenbus_switch_state(dev, XenbusStateInitWait);

        return 0;
}

static void set_backend_state(struct xenbus_device *dev,
                              enum xenbus_state state)
{
        while (dev->state != state) {
                switch (dev->state) {
                case XenbusStateClosed:
                        switch (state) {
                        case XenbusStateInitWait:
                        case XenbusStateConnected:
                                xenbus_switch_state(dev, XenbusStateInitWait);
                                break;
                        case XenbusStateClosing:
                                xenbus_switch_state(dev, XenbusStateClosing);
                                break;
                        default:
                                WARN_ON(1);
                        }
                        break;
                case XenbusStateInitWait:
                case XenbusStateInitialised:
                        switch (state) {
                        case XenbusStateConnected:
                                if (backend_connect(dev))
                                        return;
                                xenbus_switch_state(dev, XenbusStateConnected);
                                break;
                        case XenbusStateClosing:
                        case XenbusStateClosed:
                                xenbus_switch_state(dev, XenbusStateClosing);
                                break;
                        default:
                                WARN_ON(1);
                        }
                        break;
                case XenbusStateConnected:
                        switch (state) {
                        case XenbusStateInitWait:
                        case XenbusStateClosing:
                        case XenbusStateClosed:
                                down(&pvcalls_back_global.frontends_lock);
                                backend_disconnect(dev);
                                up(&pvcalls_back_global.frontends_lock);
                                xenbus_switch_state(dev, XenbusStateClosing);
                                break;
                        default:
                                WARN_ON(1);
                        }
                        break;
                case XenbusStateClosing:
                        switch (state) {
                        case XenbusStateInitWait:
                        case XenbusStateConnected:
                        case XenbusStateClosed:
                                xenbus_switch_state(dev, XenbusStateClosed);
                                break;
                        default:
                                WARN_ON(1);
                        }
                        break;
                default:
                        WARN_ON(1);
                }
        }
}

static void pvcalls_back_changed(struct xenbus_device *dev,
                                 enum xenbus_state frontend_state)
{
        switch (frontend_state) {
        case XenbusStateInitialising:
                set_backend_state(dev, XenbusStateInitWait);
                break;

        case XenbusStateInitialised:
        case XenbusStateConnected:
                set_backend_state(dev, XenbusStateConnected);
                break;

        case XenbusStateClosing:
                set_backend_state(dev, XenbusStateClosing);
                break;

        case XenbusStateClosed:
                set_backend_state(dev, XenbusStateClosed);
                if (xenbus_dev_is_online(dev))
                        break;
                device_unregister(&dev->dev);
                break;
        case XenbusStateUnknown:
                set_backend_state(dev, XenbusStateClosed);
                device_unregister(&dev->dev);
                break;

        default:
                xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
                                 frontend_state);
                break;
        }
}

static int pvcalls_back_remove(struct xenbus_device *dev)
{
        return 0;
}

static int pvcalls_back_uevent(struct xenbus_device *xdev,
                               struct kobj_uevent_env *env)
{
        return 0;
}

static const struct xenbus_device_id pvcalls_back_ids[] = {
        { "pvcalls" },
        { "" }
};

static struct xenbus_driver pvcalls_back_driver = {
        .ids = pvcalls_back_ids,
        .probe = pvcalls_back_probe,
        .remove = pvcalls_back_remove,
        .uevent = pvcalls_back_uevent,
        .otherend_changed = pvcalls_back_changed,
};

static int __init pvcalls_back_init(void)
{
        int ret;

        if (!xen_domain())
                return -ENODEV;

        ret = xenbus_register_backend(&pvcalls_back_driver);
        if (ret < 0)
                return ret;

        sema_init(&pvcalls_back_global.frontends_lock, 1);
        INIT_LIST_HEAD(&pvcalls_back_global.frontends);
        return 0;
}
module_init(pvcalls_back_init);

static void __exit pvcalls_back_fin(void)
{
        struct pvcalls_fedata *fedata, *nfedata;

        down(&pvcalls_back_global.frontends_lock);
        list_for_each_entry_safe(fedata, nfedata,
                                 &pvcalls_back_global.frontends, list) {
                backend_disconnect(fedata->dev);
        }
        up(&pvcalls_back_global.frontends_lock);

        xenbus_unregister_driver(&pvcalls_back_driver);
}

module_exit(pvcalls_back_fin);

MODULE_DESCRIPTION("Xen PV Calls backend driver");
MODULE_AUTHOR("Stefano Stabellini <sstabellini@kernel.org>");
MODULE_LICENSE("GPL");