virtio: console: Add file operations to ports for open/read/write/poll

Allow guest userspace applications to open, read from, write to, poll
the ports via the char dev interface.

When a port gets opened, a notification is sent to the host via a
control message indicating a connection has been established. Similarly,
on closing of the port, a notification is sent indicating disconnection.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 64ef476..ece1546 100644 (file)
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -19,11 +19,15 @@
 #include <linux/cdev.h>
 #include <linux/device.h>
 #include <linux/err.h>
+#include <linux/fs.h>
 #include <linux/init.h>
 #include <linux/list.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
 #include <linux/spinlock.h>
 #include <linux/virtio.h>
 #include <linux/virtio_console.h>
+#include <linux/wait.h>
 #include <linux/workqueue.h>
 #include "hvc_console.h"
 
@@ -163,8 +167,14 @@ struct port {
        struct cdev cdev;
        struct device *dev;
 
+       /* A waitqueue for poll() or blocking read operations */
+       wait_queue_head_t waitqueue;
+
        /* The 'id' to identify the port with the Host */
        u32 id;
+
+       /* Is the host device open */
+       bool host_connected;
 };
 
 /* This is the very early arch-specified put chars function. */
@@ -417,6 +427,146 @@ static ssize_t fill_readbuf(struct port *port, char *out_buf, size_t out_count,
        return out_count;
 }
 
+/* The condition that must be true for polling to end */
+static bool wait_is_over(struct port *port)
+{
+       return port_has_data(port) || !port->host_connected;
+}
+
+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_interruptible(port->waitqueue,
+                                              wait_is_over(port));
+               if (ret < 0)
+                       return ret;
+       }
+       /*
+        * 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 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;
+
+       port = filp->private_data;
+
+       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;
+       }
+
+       ret = send_buf(port, buf, count);
+free_buf:
+       kfree(buf);
+       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);
+
+       ret = 0;
+       if (port->inbuf)
+               ret |= POLLIN | POLLRDNORM;
+       if (port->host_connected)
+               ret |= POLLOUT;
+       if (!port->host_connected)
+               ret |= POLLHUP;
+
+       return ret;
+}
+
+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);
+
+       return 0;
+}
+
+static int port_fops_open(struct inode *inode, struct file *filp)
+{
+       struct cdev *cdev = inode->i_cdev;
+       struct port *port;
+
+       port = container_of(cdev, struct port, cdev);
+       filp->private_data = port;
+
+       /*
+        * Don't allow opening of console port devices -- that's done
+        * via /dev/hvc
+        */
+       if (is_console_port(port))
+               return -ENXIO;
+
+       /* Notify host of port being opened */
+       send_control_msg(filp->private_data, VIRTIO_CONSOLE_PORT_OPEN, 1);
+
+       return 0;
+}
+
+/*
+ * 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,
+       .poll  = port_fops_poll,
+       .release = port_fops_release,
+};
+
 /*
  * The put_chars() callback is pretty straightforward.
  *
@@ -560,6 +710,9 @@ int init_port_console(struct port *port)
        list_add_tail(&port->cons.list, &pdrvdata.consoles);
        spin_unlock_irq(&pdrvdata_lock);
 
+       /* Notify host of port being opened */
+       send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 1);
+
        return 0;
 }
 
@@ -599,6 +752,10 @@ static void handle_control_message(struct ports_device *portdev,
                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);
+               break;
        }
 }
 
@@ -645,6 +802,8 @@ static void in_intr(struct virtqueue *vq)
 
        spin_unlock_irqrestore(&port->inbuf_lock, flags);
 
+       wake_up_interruptible(&port->waitqueue);
+
        if (is_console_port(port) && hvc_poll(port->cons.hvc))
                hvc_kick();
 }
@@ -697,10 +856,12 @@ static int add_port(struct ports_device *portdev, u32 id)
        port->inbuf = NULL;
        port->cons.hvc = NULL;
 
+       port->host_connected = false;
+
        port->in_vq = portdev->in_vqs[port->id];
        port->out_vq = portdev->out_vqs[port->id];
 
-       cdev_init(&port->cdev, NULL);
+       cdev_init(&port->cdev, &port_fops);
 
        devt = MKDEV(portdev->chr_major, id);
        err = cdev_add(&port->cdev, devt, 1);
@@ -721,6 +882,7 @@ static int add_port(struct ports_device *portdev, u32 id)
        }
 
        spin_lock_init(&port->inbuf_lock);
+       init_waitqueue_head(&port->waitqueue);
 
        inbuf = alloc_buf(PAGE_SIZE);
        if (!inbuf) {

diff --git a/include/linux/virtio_console.h b/include/linux/virtio_console.h
index f4d183b..bd0e2a5 100644 (file)
--- a/include/linux/virtio_console.h
+++ b/include/linux/virtio_console.h
@@ -39,6 +39,7 @@ struct virtio_console_control {
 #define VIRTIO_CONSOLE_PORT_READY      0
 #define VIRTIO_CONSOLE_CONSOLE_PORT    1
 #define VIRTIO_CONSOLE_RESIZE          2
+#define VIRTIO_CONSOLE_PORT_OPEN       3
 
 #ifdef __KERNEL__
 int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int));