virtio_console.c

Go to the documentation of this file.

/*
 * Copyright (C) 2006, 2007, 2009 Rusty Russell, IBM Corporation
 * Copyright (C) 2009, 2010, 2011 Red Hat, Inc.
 * Copyright (C) 2009, 2010, 2011 Amit Shah <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <linux/cdev.h>
#include <linux/debugfs.h>
#include <linux/completion.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/freezer.h>
#include <linux/fs.h>
#include <linux/splice.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/virtio.h>
#include <linux/virtio_console.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <linux/module.h>
#include "../tty/hvc/hvc_console.h"

/*
 * This is a global struct for storing common data for all the devices
 * this driver handles.
 *
 * Mainly, it has a linked list for all the consoles in one place so
 * that callbacks from hvc for get_chars(), put_chars() work properly
 * across multiple devices and multiple ports per device.
 */
struct ports_driver_data {
    /* Used for registering chardevs */
    struct class *class;

    /* Used for exporting per-port information to debugfs */
    struct dentry *debugfs_dir;

    /* List of all the devices we're handling */
    struct list_head portdevs;

    /* Number of devices this driver is handling */
    unsigned int index;

    /*
     * This is used to keep track of the number of hvc consoles
     * spawned by this driver.  This number is given as the first
     * argument to hvc_alloc().  To correctly map an initial
     * console spawned via hvc_instantiate to the console being
     * hooked up via hvc_alloc, we need to pass the same vtermno.
     *
     * We also just assume the first console being initialised was
     * the first one that got used as the initial console.
     */
    unsigned int next_vtermno;

    /* All the console devices handled by this driver */
    struct list_head consoles;
};
static struct ports_driver_data pdrvdata;

DEFINE_SPINLOCK(pdrvdata_lock);
DECLARE_COMPLETION(early_console_added);

/* This struct holds information that's relevant only for console ports */
struct console {
    /* We'll place all consoles in a list in the pdrvdata struct */
    struct list_head list;

    /* The hvc device associated with this console port */
    struct hvc_struct *hvc;

    /* The size of the console */
    struct winsize ws;

    /*
     * This number identifies the number that we used to register
     * with hvc in hvc_instantiate() and hvc_alloc(); this is the
     * number passed on by the hvc callbacks to us to
     * differentiate between the other console ports handled by
     * this driver
     */
    u32 vtermno;
};

struct port_buffer {
    char *buf;

    /* size of the buffer in *buf above */
    size_t size;

    /* used length of the buffer */
    size_t len;
    /* offset in the buf from which to consume data */
    size_t offset;
};

/*
 * This is a per-device struct that stores data common to all the
 * ports for that device (vdev->priv).
 */
struct ports_device {
    /* Next portdev in the list, head is in the pdrvdata struct */
    struct list_head list;

    /*
     * Workqueue handlers where we process deferred work after
     * notification
     */
    struct work_struct control_work;

    struct list_head ports;

    /* To protect the list of ports */
    spinlock_t ports_lock;

    /* To protect the vq operations for the control channel */
    spinlock_t cvq_lock;

    /* The current config space is stored here */
    struct virtio_console_config config;

    /* The virtio device we're associated with */
    struct virtio_device *vdev;

    /*
     * A couple of virtqueues for the control channel: one for
     * guest->host transfers, one for host->guest transfers
     */
    struct virtqueue *c_ivq, *c_ovq;

    /* Array of per-port IO virtqueues */
    struct virtqueue **in_vqs, **out_vqs;

    /* Used for numbering devices for sysfs and debugfs */
    unsigned int drv_index;

    /* Major number for this device.  Ports will be created as minors. */
    int chr_major;
};

struct port_stats {
    unsigned long bytes_sent, bytes_received, bytes_discarded;
};

/* This struct holds the per-port data */
struct port {
    /* Next port in the list, head is in the ports_device */
    struct list_head list;

    /* Pointer to the parent virtio_console device */
    struct ports_device *portdev;

    /* The current buffer from which data has to be fed to readers */
    struct port_buffer *inbuf;

    /*
     * To protect the operations on the in_vq associated with this
     * port.  Has to be a spinlock because it can be called from
     * interrupt context (get_char()).
     */
    spinlock_t inbuf_lock;

    /* Protect the operations on the out_vq. */
    spinlock_t outvq_lock;

    /* The IO vqs for this port */
    struct virtqueue *in_vq, *out_vq;

    /* File in the debugfs directory that exposes this port's information */
    struct dentry *debugfs_file;

    /*
     * Keep count of the bytes sent, received and discarded for
     * this port for accounting and debugging purposes.  These
     * counts are not reset across port open / close events.
     */
    struct port_stats stats;

    /*
     * The entries in this struct will be valid if this port is
     * hooked up to an hvc console
     */
    struct console cons;

    /* Each port associates with a separate char device */
    struct cdev *cdev;
    struct device *dev;

    /* Reference-counting to handle port hot-unplugs and file operations */
    struct kref kref;

    /* A waitqueue for poll() or blocking read operations */
    wait_queue_head_t waitqueue;

    /* The 'name' of the port that we expose via sysfs properties */
    char *name;

    /* We can notify apps of host connect / disconnect events via SIGIO */
    struct fasync_struct *async_queue;

    /* The 'id' to identify the port with the Host */
    u32 id;

    bool outvq_full;

    /* Is the host device open */
    bool host_connected;

    /* We should allow only one process to open a port */
    bool guest_connected;
};

/* This is the very early arch-specified put chars function. */
static int (*early_put_chars)(u32, const char *, int);

static struct port *find_port_by_vtermno(u32 vtermno)
{
    struct port *port;
    struct console *cons;
    unsigned long flags;

    spin_lock_irqsave(&pdrvdata_lock, flags);
    list_for_each_entry(cons, &pdrvdata.consoles, list) {
        if (cons->vtermno == vtermno) {
            port = container_of(cons, struct port, cons);
            goto out;
        }
    }
    port = NULL;
out:
    spin_unlock_irqrestore(&pdrvdata_lock, flags);
    return port;
}

static struct port *find_port_by_devt_in_portdev(struct ports_device *portdev,
                         dev_t dev)
{
    struct port *port;
    unsigned long flags;

    spin_lock_irqsave(&portdev->ports_lock, flags);
    list_for_each_entry(port, &portdev->ports, list)
        if (port->cdev->dev == dev)
            goto out;
    port = NULL;
out:
    spin_unlock_irqrestore(&portdev->ports_lock, flags);

    return port;
}

static struct port *find_port_by_devt(dev_t dev)
{
    struct ports_device *portdev;
    struct port *port;
    unsigned long flags;

    spin_lock_irqsave(&pdrvdata_lock, flags);
    list_for_each_entry(portdev, &pdrvdata.portdevs, list) {
        port = find_port_by_devt_in_portdev(portdev, dev);
        if (port)
            goto out;
    }
    port = NULL;
out:
    spin_unlock_irqrestore(&pdrvdata_lock, flags);
    return port;
}

static struct port *find_port_by_id(struct ports_device *portdev, u32 id)
{
    struct port *port;
    unsigned long flags;

    spin_lock_irqsave(&portdev->ports_lock, flags);
    list_for_each_entry(port, &portdev->ports, list)
        if (port->id == id)
            goto out;
    port = NULL;
out:
    spin_unlock_irqrestore(&portdev->ports_lock, flags);

    return port;
}

static struct port *find_port_by_vq(struct ports_device *portdev,
                    struct virtqueue *vq)
{
    struct port *port;
    unsigned long flags;

    spin_lock_irqsave(&portdev->ports_lock, flags);
    list_for_each_entry(port, &portdev->ports, list)
        if (port->in_vq == vq || port->out_vq == vq)
            goto out;
    port = NULL;
out:
    spin_unlock_irqrestore(&portdev->ports_lock, flags);
    return port;
}

static bool is_console_port(struct port *port)
{
    if (port->cons.hvc)
        return true;
    return false;
}

static inline bool use_multiport(struct ports_device *portdev)
{
    /*
     * This condition can be true when put_chars is called from
     * early_init
     */
    if (!portdev->vdev)
        return 0;
    return portdev->vdev->features[0] & (1 << VIRTIO_CONSOLE_F_MULTIPORT);
}

static void free_buf(struct port_buffer *buf)
{
    kfree(buf->buf);
    kfree(buf);
}

static struct port_buffer *alloc_buf(size_t buf_size)
{
    struct port_buffer *buf;

    buf = kmalloc(sizeof(*buf), GFP_KERNEL);
    if (!buf)
        goto fail;
    buf->buf = kzalloc(buf_size, GFP_KERNEL);
    if (!buf->buf)
        goto free_buf;
    buf->len = 0;
    buf->offset = 0;
    buf->size = buf_size;
    return buf;

free_buf:
    kfree(buf);
fail:
    return NULL;
}

/* Callers should take appropriate locks */
static struct port_buffer *get_inbuf(struct port *port)
{
    struct port_buffer *buf;
    unsigned int len;

    if (port->inbuf)
        return port->inbuf;

    buf = virtqueue_get_buf(port->in_vq, &len);
    if (buf) {
        buf->len = len;
        buf->offset = 0;
        port->stats.bytes_received += len;
    }
    return buf;
}

/*
 * Create a scatter-gather list representing our input buffer and put
 * it in the queue.
 *
 * Callers should take appropriate locks.
 */
static int add_inbuf(struct virtqueue *vq, struct port_buffer *buf)
{
    struct scatterlist sg[1];
    int ret;

    sg_init_one(sg, buf->buf, buf->size);

    ret = virtqueue_add_buf(vq, sg, 0, 1, buf, GFP_ATOMIC);
    virtqueue_kick(vq);
    return ret;
}

/* Discard any unread data this port has. Callers lockers. */
static void discard_port_data(struct port *port)
{
    struct port_buffer *buf;
    unsigned int err;

    if (!port->portdev) {
        /* Device has been unplugged.  vqs are already gone. */
        return;
    }
    buf = get_inbuf(port);

    err = 0;
    while (buf) {
        port->stats.bytes_discarded += buf->len - buf->offset;
        if (add_inbuf(port->in_vq, buf) < 0) {
            err++;
            free_buf(buf);
        }
        port->inbuf = NULL;
        buf = get_inbuf(port);
    }
    if (err)
        dev_warn(port->dev, "Errors adding %d buffers back to vq\n",
             err);
}

static bool port_has_data(struct port *port)
{
    unsigned long flags;
    bool ret;

    ret = false;
    spin_lock_irqsave(&port->inbuf_lock, flags);
    port->inbuf = get_inbuf(port);
    if (port->inbuf)
        ret = true;

    spin_unlock_irqrestore(&port->inbuf_lock, flags);
    return ret;
}

static ssize_t __send_control_msg(struct ports_device *portdev, u32 port_id,
                  unsigned int event, unsigned int value)
{
    struct scatterlist sg[1];
    struct virtio_console_control cpkt;
    struct virtqueue *vq;
    unsigned int len;

    if (!use_multiport(portdev))
        return 0;

    cpkt.id = port_id;
    cpkt.event = event;
    cpkt.value = value;

    vq = portdev->c_ovq;

    sg_init_one(sg, &cpkt, sizeof(cpkt));
    if (virtqueue_add_buf(vq, sg, 1, 0, &cpkt, GFP_ATOMIC) >= 0) {
        virtqueue_kick(vq);
        while (!virtqueue_get_buf(vq, &len))
            cpu_relax();
    }
    return 0;
}

static ssize_t send_control_msg(struct port *port, unsigned int event,
                unsigned int value)
{
    /* Did the port get unplugged before userspace closed it? */
    if (port->portdev)
        return __send_control_msg(port->portdev, port->id, event, value);
    return 0;
}

struct buffer_token {
    union {
        void *buf;
        struct scatterlist *sg;
    } u;
    /* If sgpages == 0 then buf is used, else sg is used */
    unsigned int sgpages;
};

static void reclaim_sg_pages(struct scatterlist *sg, unsigned int nrpages)
{
    int i;
    struct page *page;

    for (i = 0; i < nrpages; i++) {
        page = sg_page(&sg[i]);
        if (!page)
            break;
        put_page(page);
    }
    kfree(sg);
}

/* Callers must take the port->outvq_lock */
static void reclaim_consumed_buffers(struct port *port)
{
    struct buffer_token *tok;
    unsigned int len;

    if (!port->portdev) {
        /* Device has been unplugged.  vqs are already gone. */
        return;
    }
    while ((tok = virtqueue_get_buf(port->out_vq, &len))) {
        if (tok->sgpages)
            reclaim_sg_pages(tok->u.sg, tok->sgpages);
        else
            kfree(tok->u.buf);
        kfree(tok);
        port->outvq_full = false;
    }
}

static ssize_t __send_to_port(struct port *port, struct scatterlist *sg,
                  int nents, size_t in_count,
                  struct buffer_token *tok, bool nonblock)
{
    struct virtqueue *out_vq;
    ssize_t ret;
    unsigned long flags;
    unsigned int len;

    out_vq = port->out_vq;

    spin_lock_irqsave(&port->outvq_lock, flags);

    reclaim_consumed_buffers(port);

    ret = virtqueue_add_buf(out_vq, sg, nents, 0, tok, GFP_ATOMIC);

    /* Tell Host to go! */
    virtqueue_kick(out_vq);

    if (ret < 0) {
        in_count = 0;
        goto done;
    }

    if (ret == 0)
        port->outvq_full = true;

    if (nonblock)
        goto done;

    /*
     * Wait till the host acknowledges it pushed out the data we
     * sent.  This is done for data from the hvc_console; the tty
     * operations are performed with spinlocks held so we can't
     * sleep here.  An alternative would be to copy the data to a
     * buffer and relax the spinning requirement.  The downside is
     * we need to kmalloc a GFP_ATOMIC buffer each time the
     * console driver writes something out.
     */
    while (!virtqueue_get_buf(out_vq, &len))
        cpu_relax();
done:
    spin_unlock_irqrestore(&port->outvq_lock, flags);

    port->stats.bytes_sent += in_count;
    /*
     * We're expected to return the amount of data we wrote -- all
     * of it
     */
    return in_count;
}

static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count,
            bool nonblock)
{
    struct scatterlist sg[1];
    struct buffer_token *tok;

    tok = kmalloc(sizeof(*tok), GFP_ATOMIC);
    if (!tok)
        return -ENOMEM;
    tok->sgpages = 0;
    tok->u.buf = in_buf;

    sg_init_one(sg, in_buf, in_count);

    return __send_to_port(port, sg, 1, in_count, tok, nonblock);
}

static ssize_t send_pages(struct port *port, struct scatterlist *sg, int nents,
              size_t in_count, bool nonblock)
{
    struct buffer_token *tok;

    tok = kmalloc(sizeof(*tok), GFP_ATOMIC);
    if (!tok)
        return -ENOMEM;
    tok->sgpages = nents;
    tok->u.sg = sg;

    return __send_to_port(port, sg, nents, in_count, tok, nonblock);
}

/*
 * Give out the data that's requested from the buffer that we have
 * queued up.
 */
static ssize_t fill_readbuf(struct port *port, char *out_buf, size_t out_count,
                bool to_user)
{
    struct port_buffer *buf;
    unsigned long flags;

    if (!out_count || !port_has_data(port))
        return 0;

    buf = port->inbuf;
    out_count = min(out_count, buf->len - buf->offset);

    if (to_user) {
        ssize_t ret;

        ret = copy_to_user(out_buf, buf->buf + buf->offset, out_count);
        if (ret)
            return -EFAULT;
    } else {
        memcpy(out_buf, buf->buf + buf->offset, out_count);
    }

    buf->offset += out_count;

    if (buf->offset == buf->len) {
        /*
         * We're done using all the data in this buffer.
         * Re-queue so that the Host can send us more data.
         */
        spin_lock_irqsave(&port->inbuf_lock, flags);
        port->inbuf = NULL;

        if (add_inbuf(port->in_vq, buf) < 0)
            dev_warn(port->dev, "failed add_buf\n");

        spin_unlock_irqrestore(&port->inbuf_lock, flags);
    }
    /* Return the number of bytes actually copied */
    return out_count;
}

/* The condition that must be true for polling to end */
static bool will_read_block(struct port *port)
{
    if (!port->guest_connected) {
        /* Port got hot-unplugged. Let's exit. */
        return false;
    }
    return !port_has_data(port) && port->host_connected;
}

static bool will_write_block(struct port *port)
{
    bool ret;

    if (!port->guest_connected) {
        /* Port got hot-unplugged. Let's exit. */
        return false;
    }
    if (!port->host_connected)
        return true;

    spin_lock_irq(&port->outvq_lock);
    /*
     * Check if the Host has consumed any buffers since we last
     * sent data (this is only applicable for nonblocking ports).
     */
    reclaim_consumed_buffers(port);
    ret = port->outvq_full;
    spin_unlock_irq(&port->outvq_lock);

    return ret;
}

static ssize_t port_fops_read(struct file *filp, char __user *ubuf,
                  size_t count, loff_t *offp)
{
    struct port *port;
    ssize_t ret;

    port = filp->private_data;

    if (!port_has_data(port)) {
        /*
         * If nothing's connected on the host just return 0 in
         * case of list_empty; this tells the userspace app
         * that there's no connection
         */
        if (!port->host_connected)
            return 0;
        if (filp->f_flags & O_NONBLOCK)
            return -EAGAIN;

        ret = wait_event_freezable(port->waitqueue,
                       !will_read_block(port));
        if (ret < 0)
            return ret;
    }
    /* Port got hot-unplugged. */
    if (!port->guest_connected)
        return -ENODEV;
    /*
     * We could've received a disconnection message while we were
     * waiting for more data.
     *
     * This check is not clubbed in the if() statement above as we
     * might receive some data as well as the host could get
     * disconnected after we got woken up from our wait.  So we
     * really want to give off whatever data we have and only then
     * check for host_connected.
     */
    if (!port_has_data(port) && !port->host_connected)
        return 0;

    return fill_readbuf(port, ubuf, count, true);
}

static int wait_port_writable(struct port *port, bool nonblock)
{
    int ret;

    if (will_write_block(port)) {
        if (nonblock)
            return -EAGAIN;

        ret = wait_event_freezable(port->waitqueue,
                       !will_write_block(port));
        if (ret < 0)
            return ret;
    }
    /* Port got hot-unplugged. */
    if (!port->guest_connected)
        return -ENODEV;

    return 0;
}

static ssize_t port_fops_write(struct file *filp, const char __user *ubuf,
                   size_t count, loff_t *offp)
{
    struct port *port;
    char *buf;
    ssize_t ret;
    bool nonblock;

    /* Userspace could be out to fool us */
    if (!count)
        return 0;

    port = filp->private_data;

    nonblock = filp->f_flags & O_NONBLOCK;

    ret = wait_port_writable(port, nonblock);
    if (ret < 0)
        return ret;

    count = min((size_t)(32 * 1024), count);

    buf = kmalloc(count, GFP_KERNEL);
    if (!buf)
        return -ENOMEM;

    ret = copy_from_user(buf, ubuf, count);
    if (ret) {
        ret = -EFAULT;
        goto free_buf;
    }

    /*
     * We now ask send_buf() to not spin for generic ports -- we
     * can re-use the same code path that non-blocking file
     * descriptors take for blocking file descriptors since the
     * wait is already done and we're certain the write will go
     * through to the host.
     */
    nonblock = true;
    ret = send_buf(port, buf, count, nonblock);

    if (nonblock && ret > 0)
        goto out;

free_buf:
    kfree(buf);
out:
    return ret;
}

struct sg_list {
    unsigned int n;
    unsigned int size;
    size_t len;
    struct scatterlist *sg;
};

static int pipe_to_sg(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
            struct splice_desc *sd)
{
    struct sg_list *sgl = sd->u.data;
    unsigned int offset, len;

    if (sgl->n == sgl->size)
        return 0;

    /* Try lock this page */
    if (buf->ops->steal(pipe, buf) == 0) {
        /* Get reference and unlock page for moving */
        get_page(buf->page);
        unlock_page(buf->page);

        len = min(buf->len, sd->len);
        sg_set_page(&(sgl->sg[sgl->n]), buf->page, len, buf->offset);
    } else {
        /* Failback to copying a page */
        struct page *page = alloc_page(GFP_KERNEL);
        char *src = buf->ops->map(pipe, buf, 1);
        char *dst;

        if (!page)
            return -ENOMEM;
        dst = kmap(page);

        offset = sd->pos & ~PAGE_MASK;

        len = sd->len;
        if (len + offset > PAGE_SIZE)
            len = PAGE_SIZE - offset;

        memcpy(dst + offset, src + buf->offset, len);

        kunmap(page);
        buf->ops->unmap(pipe, buf, src);

        sg_set_page(&(sgl->sg[sgl->n]), page, len, offset);
    }
    sgl->n++;
    sgl->len += len;

    return len;
}

/* Faster zero-copy write by splicing */
static ssize_t port_fops_splice_write(struct pipe_inode_info *pipe,
                      struct file *filp, loff_t *ppos,
                      size_t len, unsigned int flags)
{
    struct port *port = filp->private_data;
    struct sg_list sgl;
    ssize_t ret;
    struct splice_desc sd = {
        .total_len = len,
        .flags = flags,
        .pos = *ppos,
        .u.data = &sgl,
    };

    ret = wait_port_writable(port, filp->f_flags & O_NONBLOCK);
    if (ret < 0)
        return ret;

    sgl.n = 0;
    sgl.len = 0;
    sgl.size = pipe->nrbufs;
    sgl.sg = kmalloc(sizeof(struct scatterlist) * sgl.size, GFP_KERNEL);
    if (unlikely(!sgl.sg))
        return -ENOMEM;

    sg_init_table(sgl.sg, sgl.size);
    ret = __splice_from_pipe(pipe, &sd, pipe_to_sg);
    if (likely(ret > 0))
        ret = send_pages(port, sgl.sg, sgl.n, sgl.len, true);

    return ret;
}

static unsigned int port_fops_poll(struct file *filp, poll_table *wait)
{
    struct port *port;
    unsigned int ret;

    port = filp->private_data;
    poll_wait(filp, &port->waitqueue, wait);

    if (!port->guest_connected) {
        /* Port got unplugged */
        return POLLHUP;
    }
    ret = 0;
    if (!will_read_block(port))
        ret |= POLLIN | POLLRDNORM;
    if (!will_write_block(port))
        ret |= POLLOUT;
    if (!port->host_connected)
        ret |= POLLHUP;

    return ret;
}

static void remove_port(struct kref *kref);

static int port_fops_release(struct inode *inode, struct file *filp)
{
    struct port *port;

    port = filp->private_data;

    /* Notify host of port being closed */
    send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 0);

    spin_lock_irq(&port->inbuf_lock);
    port->guest_connected = false;

    discard_port_data(port);

    spin_unlock_irq(&port->inbuf_lock);

    spin_lock_irq(&port->outvq_lock);
    reclaim_consumed_buffers(port);
    spin_unlock_irq(&port->outvq_lock);

    /*
     * Locks aren't necessary here as a port can't be opened after
     * unplug, and if a port isn't unplugged, a kref would already
     * exist for the port.  Plus, taking ports_lock here would
     * create a dependency on other locks taken by functions
     * inside remove_port if we're the last holder of the port,
     * creating many problems.
     */
    kref_put(&port->kref, remove_port);

    return 0;
}

static int port_fops_open(struct inode *inode, struct file *filp)
{
    struct cdev *cdev = inode->i_cdev;
    struct port *port;
    int ret;

    port = find_port_by_devt(cdev->dev);
    filp->private_data = port;

    /* Prevent against a port getting hot-unplugged at the same time */
    spin_lock_irq(&port->portdev->ports_lock);
    kref_get(&port->kref);
    spin_unlock_irq(&port->portdev->ports_lock);

    /*
     * Don't allow opening of console port devices -- that's done
     * via /dev/hvc
     */
    if (is_console_port(port)) {
        ret = -ENXIO;
        goto out;
    }

    /* Allow only one process to open a particular port at a time */
    spin_lock_irq(&port->inbuf_lock);
    if (port->guest_connected) {
        spin_unlock_irq(&port->inbuf_lock);
        ret = -EMFILE;
        goto out;
    }

    port->guest_connected = true;
    spin_unlock_irq(&port->inbuf_lock);

    spin_lock_irq(&port->outvq_lock);
    /*
     * There might be a chance that we missed reclaiming a few
     * buffers in the window of the port getting previously closed
     * and opening now.
     */
    reclaim_consumed_buffers(port);
    spin_unlock_irq(&port->outvq_lock);

    nonseekable_open(inode, filp);

    /* Notify host of port being opened */
    send_control_msg(filp->private_data, VIRTIO_CONSOLE_PORT_OPEN, 1);

    return 0;
out:
    kref_put(&port->kref, remove_port);
    return ret;
}

static int port_fops_fasync(int fd, struct file *filp, int mode)
{
    struct port *port;

    port = filp->private_data;
    return fasync_helper(fd, filp, mode, &port->async_queue);
}

/*
 * The file operations that we support: programs in the guest can open
 * a console device, read from it, write to it, poll for data and
 * close it.  The devices are at
 *   /dev/vport<device number>p<port number>
 */
static const struct file_operations port_fops = {
    .owner = THIS_MODULE,
    .open  = port_fops_open,
    .read  = port_fops_read,
    .write = port_fops_write,
    .splice_write = port_fops_splice_write,
    .poll  = port_fops_poll,
    .release = port_fops_release,
    .fasync = port_fops_fasync,
    .llseek = no_llseek,
};

/*
 * The put_chars() callback is pretty straightforward.
 *
 * We turn the characters into a scatter-gather list, add it to the
 * output queue and then kick the Host.  Then we sit here waiting for
 * it to finish: inefficient in theory, but in practice
 * implementations will do it immediately (lguest's Launcher does).
 */
static int put_chars(u32 vtermno, const char *buf, int count)
{
    struct port *port;

    if (unlikely(early_put_chars))
        return early_put_chars(vtermno, buf, count);

    port = find_port_by_vtermno(vtermno);
    if (!port)
        return -EPIPE;

    return send_buf(port, (void *)buf, count, false);
}

/*
 * get_chars() is the callback from the hvc_console infrastructure
 * when an interrupt is received.
 *
 * We call out to fill_readbuf that gets us the required data from the
 * buffers that are queued up.
 */
static int get_chars(u32 vtermno, char *buf, int count)
{
    struct port *port;

    /* If we've not set up the port yet, we have no input to give. */
    if (unlikely(early_put_chars))
        return 0;

    port = find_port_by_vtermno(vtermno);
    if (!port)
        return -EPIPE;

    /* If we don't have an input queue yet, we can't get input. */
    BUG_ON(!port->in_vq);

    return fill_readbuf(port, buf, count, false);
}

static void resize_console(struct port *port)
{
    struct virtio_device *vdev;

    /* The port could have been hot-unplugged */
    if (!port || !is_console_port(port))
        return;

    vdev = port->portdev->vdev;
    if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE))
        hvc_resize(port->cons.hvc, port->cons.ws);
}

/* We set the configuration at this point, since we now have a tty */
static int notifier_add_vio(struct hvc_struct *hp, int data)
{
    struct port *port;

    port = find_port_by_vtermno(hp->vtermno);
    if (!port)
        return -EINVAL;

    hp->irq_requested = 1;
    resize_console(port);

    return 0;
}

static void notifier_del_vio(struct hvc_struct *hp, int data)
{
    hp->irq_requested = 0;
}

/* The operations for console ports. */
static const struct hv_ops hv_ops = {
    .get_chars = get_chars,
    .put_chars = put_chars,
    .notifier_add = notifier_add_vio,
    .notifier_del = notifier_del_vio,
    .notifier_hangup = notifier_del_vio,
};

/*
 * Console drivers are initialized very early so boot messages can go
 * out, so we do things slightly differently from the generic virtio
 * initialization of the net and block drivers.
 *
 * At this stage, the console is output-only.  It's too early to set
 * up a virtqueue, so we let the drivers do some boutique early-output
 * thing.
 */
int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
{
    early_put_chars = put_chars;
    return hvc_instantiate(0, 0, &hv_ops);
}

int init_port_console(struct port *port)
{
    int ret;

    /*
     * The Host's telling us this port is a console port.  Hook it
     * up with an hvc console.
     *
     * To set up and manage our virtual console, we call
     * hvc_alloc().
     *
     * The first argument of hvc_alloc() is the virtual console
     * number.  The second argument is the parameter for the
     * notification mechanism (like irq number).  We currently
     * leave this as zero, virtqueues have implicit notifications.
     *
     * The third argument is a "struct hv_ops" containing the
     * put_chars() get_chars(), notifier_add() and notifier_del()
     * pointers.  The final argument is the output buffer size: we
     * can do any size, so we put PAGE_SIZE here.
     */
    port->cons.vtermno = pdrvdata.next_vtermno;

    port->cons.hvc = hvc_alloc(port->cons.vtermno, 0, &hv_ops, PAGE_SIZE);
    if (IS_ERR(port->cons.hvc)) {
        ret = PTR_ERR(port->cons.hvc);
        dev_err(port->dev,
            "error %d allocating hvc for port\n", ret);
        port->cons.hvc = NULL;
        return ret;
    }
    spin_lock_irq(&pdrvdata_lock);
    pdrvdata.next_vtermno++;
    list_add_tail(&port->cons.list, &pdrvdata.consoles);
    spin_unlock_irq(&pdrvdata_lock);
    port->guest_connected = true;

    /*
     * Start using the new console output if this is the first
     * console to come up.
     */
    if (early_put_chars)
        early_put_chars = NULL;

    /* Notify host of port being opened */
    send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 1);

    return 0;
}

static ssize_t show_port_name(struct device *dev,
                  struct device_attribute *attr, char *buffer)
{
    struct port *port;

    port = dev_get_drvdata(dev);

    return sprintf(buffer, "%s\n", port->name);
}

static DEVICE_ATTR(name, S_IRUGO, show_port_name, NULL);

static struct attribute *port_sysfs_entries[] = {
    &dev_attr_name.attr,
    NULL
};

static struct attribute_group port_attribute_group = {
    .name = NULL,       /* put in device directory */
    .attrs = port_sysfs_entries,
};

static ssize_t debugfs_read(struct file *filp, char __user *ubuf,
                size_t count, loff_t *offp)
{
    struct port *port;
    char *buf;
    ssize_t ret, out_offset, out_count;

    out_count = 1024;
    buf = kmalloc(out_count, GFP_KERNEL);
    if (!buf)
        return -ENOMEM;

    port = filp->private_data;
    out_offset = 0;
    out_offset += snprintf(buf + out_offset, out_count,
                   "name: %s\n", port->name ? port->name : "");
    out_offset += snprintf(buf + out_offset, out_count - out_offset,
                   "guest_connected: %d\n", port->guest_connected);
    out_offset += snprintf(buf + out_offset, out_count - out_offset,
                   "host_connected: %d\n", port->host_connected);
    out_offset += snprintf(buf + out_offset, out_count - out_offset,
                   "outvq_full: %d\n", port->outvq_full);
    out_offset += snprintf(buf + out_offset, out_count - out_offset,
                   "bytes_sent: %lu\n", port->stats.bytes_sent);
    out_offset += snprintf(buf + out_offset, out_count - out_offset,
                   "bytes_received: %lu\n",
                   port->stats.bytes_received);
    out_offset += snprintf(buf + out_offset, out_count - out_offset,
                   "bytes_discarded: %lu\n",
                   port->stats.bytes_discarded);
    out_offset += snprintf(buf + out_offset, out_count - out_offset,
                   "is_console: %s\n",
                   is_console_port(port) ? "yes" : "no");
    out_offset += snprintf(buf + out_offset, out_count - out_offset,
                   "console_vtermno: %u\n", port->cons.vtermno);

    ret = simple_read_from_buffer(ubuf, count, offp, buf, out_offset);
    kfree(buf);
    return ret;
}

static const struct file_operations port_debugfs_ops = {
    .owner = THIS_MODULE,
    .open  = simple_open,
    .read  = debugfs_read,
};

static void set_console_size(struct port *port, u16 rows, u16 cols)
{
    if (!port || !is_console_port(port))
        return;

    port->cons.ws.ws_row = rows;
    port->cons.ws.ws_col = cols;
}

static unsigned int fill_queue(struct virtqueue *vq, spinlock_t *lock)
{
    struct port_buffer *buf;
    unsigned int nr_added_bufs;
    int ret;

    nr_added_bufs = 0;
    do {
        buf = alloc_buf(PAGE_SIZE);
        if (!buf)
            break;

        spin_lock_irq(lock);
        ret = add_inbuf(vq, buf);
        if (ret < 0) {
            spin_unlock_irq(lock);
            free_buf(buf);
            break;
        }
        nr_added_bufs++;
        spin_unlock_irq(lock);
    } while (ret > 0);

    return nr_added_bufs;
}

static void send_sigio_to_port(struct port *port)
{
    if (port->async_queue && port->guest_connected)
        kill_fasync(&port->async_queue, SIGIO, POLL_OUT);
}

static int add_port(struct ports_device *portdev, u32 id)
{
    char debugfs_name[16];
    struct port *port;
    struct port_buffer *buf;
    dev_t devt;
    unsigned int nr_added_bufs;
    int err;

    port = kmalloc(sizeof(*port), GFP_KERNEL);
    if (!port) {
        err = -ENOMEM;
        goto fail;
    }
    kref_init(&port->kref);

    port->portdev = portdev;
    port->id = id;

    port->name = NULL;
    port->inbuf = NULL;
    port->cons.hvc = NULL;
    port->async_queue = NULL;

    port->cons.ws.ws_row = port->cons.ws.ws_col = 0;

    port->host_connected = port->guest_connected = false;
    port->stats = (struct port_stats) { 0 };

    port->outvq_full = false;

    port->in_vq = portdev->in_vqs[port->id];
    port->out_vq = portdev->out_vqs[port->id];

    port->cdev = cdev_alloc();
    if (!port->cdev) {
        dev_err(&port->portdev->vdev->dev, "Error allocating cdev\n");
        err = -ENOMEM;
        goto free_port;
    }
    port->cdev->ops = &port_fops;

    devt = MKDEV(portdev->chr_major, id);
    err = cdev_add(port->cdev, devt, 1);
    if (err < 0) {
        dev_err(&port->portdev->vdev->dev,
            "Error %d adding cdev for port %u\n", err, id);
        goto free_cdev;
    }
    port->dev = device_create(pdrvdata.class, &port->portdev->vdev->dev,
                  devt, port, "vport%up%u",
                  port->portdev->drv_index, id);
    if (IS_ERR(port->dev)) {
        err = PTR_ERR(port->dev);
        dev_err(&port->portdev->vdev->dev,
            "Error %d creating device for port %u\n",
            err, id);
        goto free_cdev;
    }

    spin_lock_init(&port->inbuf_lock);
    spin_lock_init(&port->outvq_lock);
    init_waitqueue_head(&port->waitqueue);

    /* Fill the in_vq with buffers so the host can send us data. */
    nr_added_bufs = fill_queue(port->in_vq, &port->inbuf_lock);
    if (!nr_added_bufs) {
        dev_err(port->dev, "Error allocating inbufs\n");
        err = -ENOMEM;
        goto free_device;
    }

    /*
     * If we're not using multiport support, this has to be a console port
     */
    if (!use_multiport(port->portdev)) {
        err = init_port_console(port);
        if (err)
            goto free_inbufs;
    }

    spin_lock_irq(&portdev->ports_lock);
    list_add_tail(&port->list, &port->portdev->ports);
    spin_unlock_irq(&portdev->ports_lock);

    /*
     * Tell the Host we're set so that it can send us various
     * configuration parameters for this port (eg, port name,
     * caching, whether this is a console port, etc.)
     */
    send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);

    if (pdrvdata.debugfs_dir) {
        /*
         * Finally, create the debugfs file that we can use to
         * inspect a port's state at any time
         */
        sprintf(debugfs_name, "vport%up%u",
            port->portdev->drv_index, id);
        port->debugfs_file = debugfs_create_file(debugfs_name, 0444,
                             pdrvdata.debugfs_dir,
                             port,
                             &port_debugfs_ops);
    }
    return 0;

free_inbufs:
    while ((buf = virtqueue_detach_unused_buf(port->in_vq)))
        free_buf(buf);
free_device:
    device_destroy(pdrvdata.class, port->dev->devt);
free_cdev:
    cdev_del(port->cdev);
free_port:
    kfree(port);
fail:
    /* The host might want to notify management sw about port add failure */
    __send_control_msg(portdev, id, VIRTIO_CONSOLE_PORT_READY, 0);
    return err;
}

/* No users remain, remove all port-specific data. */
static void remove_port(struct kref *kref)
{
    struct port *port;

    port = container_of(kref, struct port, kref);

    sysfs_remove_group(&port->dev->kobj, &port_attribute_group);
    device_destroy(pdrvdata.class, port->dev->devt);
    cdev_del(port->cdev);

    kfree(port->name);

    debugfs_remove(port->debugfs_file);

    kfree(port);
}

static void remove_port_data(struct port *port)
{
    struct port_buffer *buf;

    /* Remove unused data this port might have received. */
    discard_port_data(port);

    reclaim_consumed_buffers(port);

    /* Remove buffers we queued up for the Host to send us data in. */
    while ((buf = virtqueue_detach_unused_buf(port->in_vq)))
        free_buf(buf);
}

/*
 * Port got unplugged.  Remove port from portdev's list and drop the
 * kref reference.  If no userspace has this port opened, it will
 * result in immediate removal the port.
 */
static void unplug_port(struct port *port)
{
    spin_lock_irq(&port->portdev->ports_lock);
    list_del(&port->list);
    spin_unlock_irq(&port->portdev->ports_lock);

    if (port->guest_connected) {
        port->guest_connected = false;
        port->host_connected = false;
        wake_up_interruptible(&port->waitqueue);

        /* Let the app know the port is going down. */
        send_sigio_to_port(port);
    }

    if (is_console_port(port)) {
        spin_lock_irq(&pdrvdata_lock);
        list_del(&port->cons.list);
        spin_unlock_irq(&pdrvdata_lock);
        hvc_remove(port->cons.hvc);
    }

    remove_port_data(port);

    /*
     * We should just assume the device itself has gone off --
     * else a close on an open port later will try to send out a
     * control message.
     */
    port->portdev = NULL;

    /*
     * Locks around here are not necessary - a port can't be
     * opened after we removed the port struct from ports_list
     * above.
     */
    kref_put(&port->kref, remove_port);
}

/* Any private messages that the Host and Guest want to share */
static void handle_control_message(struct ports_device *portdev,
                   struct port_buffer *buf)
{
    struct virtio_console_control *cpkt;
    struct port *port;
    size_t name_size;
    int err;

    cpkt = (struct virtio_console_control *)(buf->buf + buf->offset);

    port = find_port_by_id(portdev, cpkt->id);
    if (!port && cpkt->event != VIRTIO_CONSOLE_PORT_ADD) {
        /* No valid header at start of buffer.  Drop it. */
        dev_dbg(&portdev->vdev->dev,
            "Invalid index %u in control packet\n", cpkt->id);
        return;
    }

    switch (cpkt->event) {
    case VIRTIO_CONSOLE_PORT_ADD:
        if (port) {
            dev_dbg(&portdev->vdev->dev,
                "Port %u already added\n", port->id);
            send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);
            break;
        }
        if (cpkt->id >= portdev->config.max_nr_ports) {
            dev_warn(&portdev->vdev->dev,
                "Request for adding port with out-of-bound id %u, max. supported id: %u\n",
                cpkt->id, portdev->config.max_nr_ports - 1);
            break;
        }
        add_port(portdev, cpkt->id);
        break;
    case VIRTIO_CONSOLE_PORT_REMOVE:
        unplug_port(port);
        break;
    case VIRTIO_CONSOLE_CONSOLE_PORT:
        if (!cpkt->value)
            break;
        if (is_console_port(port))
            break;

        init_port_console(port);
        complete(&early_console_added);
        /*
         * Could remove the port here in case init fails - but
         * have to notify the host first.
         */
        break;
    case VIRTIO_CONSOLE_RESIZE: {
        struct {
            __u16 rows;
            __u16 cols;
        } size;

        if (!is_console_port(port))
            break;

        memcpy(&size, buf->buf + buf->offset + sizeof(*cpkt),
               sizeof(size));
        set_console_size(port, size.rows, size.cols);

        port->cons.hvc->irq_requested = 1;
        resize_console(port);
        break;
    }
    case VIRTIO_CONSOLE_PORT_OPEN:
        port->host_connected = cpkt->value;
        wake_up_interruptible(&port->waitqueue);
        /*
         * If the host port got closed and the host had any
         * unconsumed buffers, we'll be able to reclaim them
         * now.
         */
        spin_lock_irq(&port->outvq_lock);
        reclaim_consumed_buffers(port);
        spin_unlock_irq(&port->outvq_lock);

        /*
         * If the guest is connected, it'll be interested in
         * knowing the host connection state changed.
         */
        send_sigio_to_port(port);
        break;
    case VIRTIO_CONSOLE_PORT_NAME:
        /*
         * If we woke up after hibernation, we can get this
         * again.  Skip it in that case.
         */
        if (port->name)
            break;

        /*
         * Skip the size of the header and the cpkt to get the size
         * of the name that was sent
         */
        name_size = buf->len - buf->offset - sizeof(*cpkt) + 1;

        port->name = kmalloc(name_size, GFP_KERNEL);
        if (!port->name) {
            dev_err(port->dev,
                "Not enough space to store port name\n");
            break;
        }
        strncpy(port->name, buf->buf + buf->offset + sizeof(*cpkt),
            name_size - 1);
        port->name[name_size - 1] = 0;

        /*
         * Since we only have one sysfs attribute, 'name',
         * create it only if we have a name for the port.
         */
        err = sysfs_create_group(&port->dev->kobj,
                     &port_attribute_group);
        if (err) {
            dev_err(port->dev,
                "Error %d creating sysfs device attributes\n",
                err);
        } else {
            /*
             * Generate a udev event so that appropriate
             * symlinks can be created based on udev
             * rules.
             */
            kobject_uevent(&port->dev->kobj, KOBJ_CHANGE);
        }
        break;
    }
}

static void control_work_handler(struct work_struct *work)
{
    struct ports_device *portdev;
    struct virtqueue *vq;
    struct port_buffer *buf;
    unsigned int len;

    portdev = container_of(work, struct ports_device, control_work);
    vq = portdev->c_ivq;

    spin_lock(&portdev->cvq_lock);
    while ((buf = virtqueue_get_buf(vq, &len))) {
        spin_unlock(&portdev->cvq_lock);

        buf->len = len;
        buf->offset = 0;

        handle_control_message(portdev, buf);

        spin_lock(&portdev->cvq_lock);
        if (add_inbuf(portdev->c_ivq, buf) < 0) {
            dev_warn(&portdev->vdev->dev,
                 "Error adding buffer to queue\n");
            free_buf(buf);
        }
    }
    spin_unlock(&portdev->cvq_lock);
}

static void out_intr(struct virtqueue *vq)
{
    struct port *port;

    port = find_port_by_vq(vq->vdev->priv, vq);
    if (!port)
        return;

    wake_up_interruptible(&port->waitqueue);
}

static void in_intr(struct virtqueue *vq)
{
    struct port *port;
    unsigned long flags;

    port = find_port_by_vq(vq->vdev->priv, vq);
    if (!port)
        return;

    spin_lock_irqsave(&port->inbuf_lock, flags);
    port->inbuf = get_inbuf(port);

    /*
     * Don't queue up data when port is closed.  This condition
     * can be reached when a console port is not yet connected (no
     * tty is spawned) and the host sends out data to console
     * ports.  For generic serial ports, the host won't
     * (shouldn't) send data till the guest is connected.
     */
    if (!port->guest_connected)
        discard_port_data(port);

    spin_unlock_irqrestore(&port->inbuf_lock, flags);

    wake_up_interruptible(&port->waitqueue);

    /* Send a SIGIO indicating new data in case the process asked for it */
    send_sigio_to_port(port);

    if (is_console_port(port) && hvc_poll(port->cons.hvc))
        hvc_kick();
}

static void control_intr(struct virtqueue *vq)
{
    struct ports_device *portdev;

    portdev = vq->vdev->priv;
    schedule_work(&portdev->control_work);
}

static void config_intr(struct virtio_device *vdev)
{
    struct ports_device *portdev;

    portdev = vdev->priv;

    if (!use_multiport(portdev)) {
        struct port *port;
        u16 rows, cols;

        vdev->config->get(vdev,
                  offsetof(struct virtio_console_config, cols),
                  &cols, sizeof(u16));
        vdev->config->get(vdev,
                  offsetof(struct virtio_console_config, rows),
                  &rows, sizeof(u16));

        port = find_port_by_id(portdev, 0);
        set_console_size(port, rows, cols);

        /*
         * We'll use this way of resizing only for legacy
         * support.  For newer userspace
         * (VIRTIO_CONSOLE_F_MULTPORT+), use control messages
         * to indicate console size changes so that it can be
         * done per-port.
         */
        resize_console(port);
    }
}

static int init_vqs(struct ports_device *portdev)
{
    vq_callback_t **io_callbacks;
    char **io_names;
    struct virtqueue **vqs;
    u32 i, j, nr_ports, nr_queues;
    int err;

    nr_ports = portdev->config.max_nr_ports;
    nr_queues = use_multiport(portdev) ? (nr_ports + 1) * 2 : 2;

    vqs = kmalloc(nr_queues * sizeof(struct virtqueue *), GFP_KERNEL);
    io_callbacks = kmalloc(nr_queues * sizeof(vq_callback_t *), GFP_KERNEL);
    io_names = kmalloc(nr_queues * sizeof(char *), GFP_KERNEL);
    portdev->in_vqs = kmalloc(nr_ports * sizeof(struct virtqueue *),
                  GFP_KERNEL);
    portdev->out_vqs = kmalloc(nr_ports * sizeof(struct virtqueue *),
                   GFP_KERNEL);
    if (!vqs || !io_callbacks || !io_names || !portdev->in_vqs ||
        !portdev->out_vqs) {
        err = -ENOMEM;
        goto free;
    }

    /*
     * For backward compat (newer host but older guest), the host
     * spawns a console port first and also inits the vqs for port
     * 0 before others.
     */
    j = 0;
    io_callbacks[j] = in_intr;
    io_callbacks[j + 1] = out_intr;
    io_names[j] = "input";
    io_names[j + 1] = "output";
    j += 2;

    if (use_multiport(portdev)) {
        io_callbacks[j] = control_intr;
        io_callbacks[j + 1] = NULL;
        io_names[j] = "control-i";
        io_names[j + 1] = "control-o";

        for (i = 1; i < nr_ports; i++) {
            j += 2;
            io_callbacks[j] = in_intr;
            io_callbacks[j + 1] = out_intr;
            io_names[j] = "input";
            io_names[j + 1] = "output";
        }
    }
    /* Find the queues. */
    err = portdev->vdev->config->find_vqs(portdev->vdev, nr_queues, vqs,
                          io_callbacks,
                          (const char **)io_names);
    if (err)
        goto free;

    j = 0;
    portdev->in_vqs[0] = vqs[0];
    portdev->out_vqs[0] = vqs[1];
    j += 2;
    if (use_multiport(portdev)) {
        portdev->c_ivq = vqs[j];
        portdev->c_ovq = vqs[j + 1];

        for (i = 1; i < nr_ports; i++) {
            j += 2;
            portdev->in_vqs[i] = vqs[j];
            portdev->out_vqs[i] = vqs[j + 1];
        }
    }
    kfree(io_names);
    kfree(io_callbacks);
    kfree(vqs);

    return 0;

free:
    kfree(portdev->out_vqs);
    kfree(portdev->in_vqs);
    kfree(io_names);
    kfree(io_callbacks);
    kfree(vqs);

    return err;
}

static const struct file_operations portdev_fops = {
    .owner = THIS_MODULE,
};

static void remove_vqs(struct ports_device *portdev)
{
    portdev->vdev->config->del_vqs(portdev->vdev);
    kfree(portdev->in_vqs);
    kfree(portdev->out_vqs);
}

static void remove_controlq_data(struct ports_device *portdev)
{
    struct port_buffer *buf;
    unsigned int len;

    if (!use_multiport(portdev))
        return;

    while ((buf = virtqueue_get_buf(portdev->c_ivq, &len)))
        free_buf(buf);

    while ((buf = virtqueue_detach_unused_buf(portdev->c_ivq)))
        free_buf(buf);
}

/*
 * Once we're further in boot, we get probed like any other virtio
 * device.
 *
 * If the host also supports multiple console ports, we check the
 * config space to see how many ports the host has spawned.  We
 * initialize each port found.
 */
static int __devinit virtcons_probe(struct virtio_device *vdev)
{
    struct ports_device *portdev;
    int err;
    bool multiport;
    bool early = early_put_chars != NULL;

    /* Ensure to read early_put_chars now */
    barrier();

    portdev = kmalloc(sizeof(*portdev), GFP_KERNEL);
    if (!portdev) {
        err = -ENOMEM;
        goto fail;
    }

    /* Attach this portdev to this virtio_device, and vice-versa. */
    portdev->vdev = vdev;
    vdev->priv = portdev;

    spin_lock_irq(&pdrvdata_lock);
    portdev->drv_index = pdrvdata.index++;
    spin_unlock_irq(&pdrvdata_lock);

    portdev->chr_major = register_chrdev(0, "virtio-portsdev",
                         &portdev_fops);
    if (portdev->chr_major < 0) {
        dev_err(&vdev->dev,
            "Error %d registering chrdev for device %u\n",
            portdev->chr_major, portdev->drv_index);
        err = portdev->chr_major;
        goto free;
    }

    multiport = false;
    portdev->config.max_nr_ports = 1;
    if (virtio_config_val(vdev, VIRTIO_CONSOLE_F_MULTIPORT,
                  offsetof(struct virtio_console_config,
                       max_nr_ports),
                  &portdev->config.max_nr_ports) == 0)
        multiport = true;

    err = init_vqs(portdev);
    if (err < 0) {
        dev_err(&vdev->dev, "Error %d initializing vqs\n", err);
        goto free_chrdev;
    }

    spin_lock_init(&portdev->ports_lock);
    INIT_LIST_HEAD(&portdev->ports);

    if (multiport) {
        unsigned int nr_added_bufs;

        spin_lock_init(&portdev->cvq_lock);
        INIT_WORK(&portdev->control_work, &control_work_handler);

        nr_added_bufs = fill_queue(portdev->c_ivq, &portdev->cvq_lock);
        if (!nr_added_bufs) {
            dev_err(&vdev->dev,
                "Error allocating buffers for control queue\n");
            err = -ENOMEM;
            goto free_vqs;
        }
    } else {
        /*
         * For backward compatibility: Create a console port
         * if we're running on older host.
         */
        add_port(portdev, 0);
    }

    spin_lock_irq(&pdrvdata_lock);
    list_add_tail(&portdev->list, &pdrvdata.portdevs);
    spin_unlock_irq(&pdrvdata_lock);

    __send_control_msg(portdev, VIRTIO_CONSOLE_BAD_ID,
               VIRTIO_CONSOLE_DEVICE_READY, 1);

    /*
     * If there was an early virtio console, assume that there are no
     * other consoles. We need to wait until the hvc_alloc matches the
     * hvc_instantiate, otherwise tty_open will complain, resulting in
     * a "Warning: unable to open an initial console" boot failure.
     * Without multiport this is done in add_port above. With multiport
     * this might take some host<->guest communication - thus we have to
     * wait.
     */
    if (multiport && early)
        wait_for_completion(&early_console_added);

    return 0;

free_vqs:
    /* The host might want to notify mgmt sw about device add failure */
    __send_control_msg(portdev, VIRTIO_CONSOLE_BAD_ID,
               VIRTIO_CONSOLE_DEVICE_READY, 0);
    remove_vqs(portdev);
free_chrdev:
    unregister_chrdev(portdev->chr_major, "virtio-portsdev");
free:
    kfree(portdev);
fail:
    return err;
}

static void virtcons_remove(struct virtio_device *vdev)
{
    struct ports_device *portdev;
    struct port *port, *port2;

    portdev = vdev->priv;

    spin_lock_irq(&pdrvdata_lock);
    list_del(&portdev->list);
    spin_unlock_irq(&pdrvdata_lock);

    /* Disable interrupts for vqs */
    vdev->config->reset(vdev);
    /* Finish up work that's lined up */
    cancel_work_sync(&portdev->control_work);

    list_for_each_entry_safe(port, port2, &portdev->ports, list)
        unplug_port(port);

    unregister_chrdev(portdev->chr_major, "virtio-portsdev");

    /*
     * When yanking out a device, we immediately lose the
     * (device-side) queues.  So there's no point in keeping the
     * guest side around till we drop our final reference.  This
     * also means that any ports which are in an open state will
     * have to just stop using the port, as the vqs are going
     * away.
     */
    remove_controlq_data(portdev);
    remove_vqs(portdev);
    kfree(portdev);
}

static struct virtio_device_id id_table[] = {
    { VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID },
    { 0 },
};

static unsigned int features[] = {
    VIRTIO_CONSOLE_F_SIZE,
    VIRTIO_CONSOLE_F_MULTIPORT,
};

#ifdef CONFIG_PM
static int virtcons_freeze(struct virtio_device *vdev)
{
    struct ports_device *portdev;
    struct port *port;

    portdev = vdev->priv;

    vdev->config->reset(vdev);

    virtqueue_disable_cb(portdev->c_ivq);
    cancel_work_sync(&portdev->control_work);
    /*
     * Once more: if control_work_handler() was running, it would
     * enable the cb as the last step.
     */
    virtqueue_disable_cb(portdev->c_ivq);
    remove_controlq_data(portdev);

    list_for_each_entry(port, &portdev->ports, list) {
        virtqueue_disable_cb(port->in_vq);
        virtqueue_disable_cb(port->out_vq);
        /*
         * We'll ask the host later if the new invocation has
         * the port opened or closed.
         */
        port->host_connected = false;
        remove_port_data(port);
    }
    remove_vqs(portdev);

    return 0;
}

static int virtcons_restore(struct virtio_device *vdev)
{
    struct ports_device *portdev;
    struct port *port;
    int ret;

    portdev = vdev->priv;

    ret = init_vqs(portdev);
    if (ret)
        return ret;

    if (use_multiport(portdev))
        fill_queue(portdev->c_ivq, &portdev->cvq_lock);

    list_for_each_entry(port, &portdev->ports, list) {
        port->in_vq = portdev->in_vqs[port->id];
        port->out_vq = portdev->out_vqs[port->id];

        fill_queue(port->in_vq, &port->inbuf_lock);

        /* Get port open/close status on the host */
        send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);

        /*
         * If a port was open at the time of suspending, we
         * have to let the host know that it's still open.
         */
        if (port->guest_connected)
            send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 1);
    }
    return 0;
}
#endif

static struct virtio_driver virtio_console = {
    .feature_table = features,
    .feature_table_size = ARRAY_SIZE(features),
    .driver.name =  KBUILD_MODNAME,
    .driver.owner = THIS_MODULE,
    .id_table = id_table,
    .probe =    virtcons_probe,
    .remove =   virtcons_remove,
    .config_changed = config_intr,
#ifdef CONFIG_PM
    .freeze =   virtcons_freeze,
    .restore =  virtcons_restore,
#endif
};

static int __init init(void)
{
    int err;

    pdrvdata.class = class_create(THIS_MODULE, "virtio-ports");
    if (IS_ERR(pdrvdata.class)) {
        err = PTR_ERR(pdrvdata.class);
        pr_err("Error %d creating virtio-ports class\n", err);
        return err;
    }

    pdrvdata.debugfs_dir = debugfs_create_dir("virtio-ports", NULL);
    if (!pdrvdata.debugfs_dir) {
        pr_warning("Error %ld creating debugfs dir for virtio-ports\n",
               PTR_ERR(pdrvdata.debugfs_dir));
    }
    INIT_LIST_HEAD(&pdrvdata.consoles);
    INIT_LIST_HEAD(&pdrvdata.portdevs);

    err = register_virtio_driver(&virtio_console);
    if (err < 0) {
        pr_err("Error %d registering virtio driver\n", err);
        goto free;
    }
    return 0;
free:
    if (pdrvdata.debugfs_dir)
        debugfs_remove_recursive(pdrvdata.debugfs_dir);
    class_destroy(pdrvdata.class);
    return err;
}

static void __exit fini(void)
{
    unregister_virtio_driver(&virtio_console);

    class_destroy(pdrvdata.class);
    if (pdrvdata.debugfs_dir)
        debugfs_remove_recursive(pdrvdata.debugfs_dir);
}
module_init(init);
module_exit(fini);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio console driver");
MODULE_LICENSE("GPL");