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[Qemu-devel] [PATCH 1/1] virtio_console: Add interface for guest and hos


From: Amit Shah
Subject: [Qemu-devel] [PATCH 1/1] virtio_console: Add interface for guest and host communication
Date: Thu, 3 Sep 2009 18:23:30 +0530

Expose multiple char devices ("ports") for simple communication
between the host userspace and guest.

Sample offline usages can be: poking around in a guest to find out
the file systems used, applications installed, etc. Online usages
can be sharing of clipboard data between the guest and the host,
sending information about logged-in users to the host, locking the
screen or session when a vnc session is closed, and so on.

The interface presented to guest userspace is of a simple char
device, so it can be used like this:

    fd = open("/dev/vcon2", O_RDWR);
    ret = read(fd, buf, 100);
    ret = write(fd, string, strlen(string));

Each port is to be assigned a unique function, for example, the
first 4 ports may be reserved for libvirt usage, the next 4 for
generic streaming data and so on. This port-function mapping
isn't finalised yet.

For requirements, use-cases and some history see

    http://www.linux-kvm.org/page/VMchannel_Requirements

Signed-off-by: Amit Shah <address@hidden>
---
 drivers/char/Kconfig           |    4 +-
 drivers/char/virtio_console.c  |  980 ++++++++++++++++++++++++++++++++++------
 include/linux/virtio_console.h |   34 ++
 3 files changed, 889 insertions(+), 129 deletions(-)

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index b8368e2..cbbb9a1 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -678,7 +678,9 @@ config VIRTIO_CONSOLE
        select HVC_DRIVER
        help
          Virtio console for use with lguest and other hypervisors.
-
+         Also serves as a general-purpose serial device for data transfer
+         between the guest and host. Character devices at /dev/vconNN will
+         be created when corresponding ports are found.
 
 config HVCS
        tristate "IBM Hypervisor Virtual Console Server support"
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 0d328b5..edea6d3 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -13,6 +13,7 @@
  * Host can send more.  Buffering in the Host could alleviate this, but it is a
  * difficult problem in general. :*/
 /* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
+ * Copyright (C) 2009, Amit Shah, Red Hat, Inc.
  *
  * 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
@@ -28,116 +29,395 @@
  * 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/device.h>
 #include <linux/err.h>
+#include <linux/fs.h>
 #include <linux/init.h>
+#include <linux/poll.h>
+#include <linux/spinlock.h>
 #include <linux/virtio.h>
 #include <linux/virtio_ids.h>
 #include <linux/virtio_console.h>
+#include <linux/workqueue.h>
 #include "hvc_console.h"
 
-/*D:340 These represent our input and output console queues, and the virtio
+/*D:340 FIXME These represent our input and output console queues, and the 
virtio
  * operations for them. */
-static struct virtqueue *in_vq, *out_vq;
-static struct virtio_device *vdev;
+struct virtio_console_struct {
+       struct work_struct rx_work;
+       struct work_struct tx_work;
+       struct work_struct config_work;
 
-/* This is our input buffer, and how much data is left in it. */
-static unsigned int in_len;
-static char *in, *inbuf;
+       struct list_head port_head;
+       struct list_head unused_read_head;
+       struct list_head unused_write_head;
 
-/* The operations for our console. */
-static struct hv_ops virtio_cons;
+       /* To protect the list of unused write buffers */
+       spinlock_t write_list_lock;
 
-/* The hvc device */
-static struct hvc_struct *hvc;
+       struct virtio_device *vdev;
+       struct class *class;
+       struct virtqueue *in_vq, *out_vq;
 
-/*D:310 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 virtio_console_config *config;
+};
+
+/* This struct holds individual buffers received for each port */
+struct virtio_console_port_buffer {
+       struct list_head next;
+
+       char *buf;
+
+       size_t len; /* length of the buffer */
+       size_t offset; /* offset in the buf from which to consume data */
+};
+
+struct virtio_console_port {
+       /* Next port in the list */
+       struct list_head next;
+
+       /* Buffer management */
+       struct list_head readbuf_head;
+       wait_queue_head_t waitqueue;
+
+       /* Each port associates with a separate char device */
+       struct cdev cdev;
+       struct device *dev;
+
+       /* The hvc device, if this port is associated with a console */
+       struct hvc_struct *hvc;
+
+       bool host_connected;  /* Is the host device open */
+};
+
+static struct virtio_console_struct virtconsole;
+
+static int major = 60; /* from the experimental range */
+
+static struct virtio_console_port *get_port_from_id(u32 id)
 {
-       struct scatterlist sg[1];
-       unsigned int len;
-
-       /* This is a convenient routine to initialize a single-elem sg list */
-       sg_init_one(sg, buf, count);
-
-       /* add_buf wants a token to identify this buffer: we hand it any
-        * non-NULL pointer, since there's only ever one buffer. */
-       if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) >= 0) {
-               /* Tell Host to go! */
-               out_vq->vq_ops->kick(out_vq);
-               /* Chill out until it's done with the buffer. */
-               while (!out_vq->vq_ops->get_buf(out_vq, &len))
-                       cpu_relax();
+       struct virtio_console_port *port;
+
+       list_for_each_entry(port, &virtconsole.port_head, next) {
+               if (MINOR(port->dev->devt) == id)
+                       return port;
        }
+       return NULL;
+}
 
-       /* We're expected to return the amount of data we wrote: all of it. */
-       return count;
+static int get_id_from_port(struct virtio_console_port *port)
+{
+       return MINOR(port->dev->devt);
 }
 
-/* Create a scatter-gather list representing our input buffer and put it in the
- * queue. */
-static void add_inbuf(void)
+static bool is_console_port(struct virtio_console_port *port)
 {
-       struct scatterlist sg[1];
-       sg_init_one(sg, inbuf, PAGE_SIZE);
+       u32 port_nr = get_id_from_port(port);
 
-       /* We should always be able to add one buffer to an empty queue. */
-       if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) < 0)
-               BUG();
-       in_vq->vq_ops->kick(in_vq);
+       if (port_nr == VIRTIO_CONSOLE_CONSOLE_PORT ||
+           port_nr == VIRTIO_CONSOLE_CONSOLE2_PORT)
+               return true;
+       return false;
 }
 
-/*D:350 get_chars() is the callback from the hvc_console infrastructure when
- * an interrupt is received.
- *
- * Most of the code deals with the fact that the hvc_console() infrastructure
- * only asks us for 16 bytes at a time.  We keep in_offset and in_used fields
- * for partially-filled buffers. */
-static int get_chars(u32 vtermno, char *buf, int count)
+static inline bool use_multiport(void)
 {
-       /* If we don't have an input queue yet, we can't get input. */
-       BUG_ON(!in_vq);
+       /* This condition can be true when put_chars is called from
+        * early_init
+        */
+       if (!virtconsole.vdev)
+               return 0;
+       return virtconsole.vdev->features[0] & (1 << 
VIRTIO_CONSOLE_F_MULTIPORT);
+}
+
+static inline bool is_internal(u32 flags)
+{
+       return flags & VIRTIO_CONSOLE_ID_INTERNAL;
+}
+
+static ssize_t fill_readbuf(struct virtio_console_port *port,
+                           char *out_buf, size_t out_count, bool to_user)
+{
+       struct virtio_console_port_buffer *buf, *buf2;
+       ssize_t out_offset, ret;
+
+       out_offset = 0;
+       list_for_each_entry_safe(buf, buf2, &port->readbuf_head, next) {
+               size_t copy_size;
+
+               copy_size = out_count;
+               if (copy_size > buf->len - buf->offset)
+                       copy_size = buf->len - buf->offset;
+
+               if (to_user) {
+                       ret = copy_to_user(out_buf + out_offset,
+                                          buf->buf + buf->offset,
+                                          copy_size);
+                       /* FIXME: Deal with ret != 0 */
+               } else {
+                       memcpy(out_buf + out_offset,
+                              buf->buf + buf->offset,
+                              copy_size);
+                       ret = 0; /* Emulate copy_to_user behaviour */
+               }
+
+               /* Return the number of bytes actually copied */
+               ret = copy_size - ret;
+               buf->offset += ret;
+               out_offset += ret;
+               out_count -= ret;
+
+               if (buf->len - buf->offset == 0) {
+                       list_del(&buf->next);
+                       kfree(buf->buf);
+                       kfree(buf);
+               }
+               if (!out_count)
+                       break;
+       }
+       return out_offset;
+}
+
+static bool wait_is_over(struct virtio_console_port *port)
+{
+       return !list_empty(&port->readbuf_head) || !port->host_connected;
+}
 
-       /* No buffer?  Try to get one. */
-       if (!in_len) {
-               in = in_vq->vq_ops->get_buf(in_vq, &in_len);
-               if (!in)
+static ssize_t virtconsole_read(struct file *filp, char __user *ubuf,
+                              size_t count, loff_t *offp)
+{
+       struct virtio_console_port *port;
+       ssize_t ret;
+
+       port = filp->private_data;
+
+       if (list_empty(&port->readbuf_head)) {
+               /* 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 (list_empty(&port->readbuf_head) && !port->host_connected)
+               return 0;
+
+       return fill_readbuf(port, ubuf, count, true);
+}
+
+static ssize_t send_buf(struct virtio_console_port *port,
+                       const char *in_buf, size_t in_count,
+                       u32 flags, bool from_user)
+{
+       struct virtqueue *out_vq;
+       struct virtio_console_port_buffer *buf, *buf2;
+       struct scatterlist sg[1];
+       struct virtio_console_header header;
+       size_t in_offset, copy_size;
+       ssize_t ret;
+       unsigned int header_len;
+
+       if (!in_count)
+               return 0;
+
+       out_vq = virtconsole.out_vq;
+
+       /* We can't send internal messages to a host that won't understand it */
+       if (!use_multiport() && is_internal(flags))
+               return 0;
+       header_len = 0;
+       if (use_multiport()) {
+               header.id = get_id_from_port(port);
+               header.flags = flags;
+               header.size = in_count;
+               header_len = sizeof(header);
        }
 
-       /* You want more than we have to give?  Well, try wanting less! */
-       if (in_len < count)
-               count = in_len;
+       in_offset = 0; /* offset in the user buffer */
+       while (in_count - in_offset) {
+               copy_size = min(in_count - in_offset + header_len, PAGE_SIZE);
+
+               spin_lock(&virtconsole.write_list_lock);
+               list_for_each_entry_safe(buf, buf2,
+                                        &virtconsole.unused_write_head,
+                                        next) {
+                       list_del(&buf->next);
+                       break;
+               }
+               spin_unlock(&virtconsole.write_list_lock);
+               if (!buf)
+                       break;
+               if (header_len) {
+                       memcpy(buf->buf, &header, header_len);
+                       copy_size -= header_len;
+               }
+               if (from_user)
+                       ret = copy_from_user(buf->buf + header_len,
+                                            in_buf + in_offset, copy_size);
+               else {
+                       /* Since we're not sure when the host will actually
+                        * consume the data and tell us about it, we have
+                        * to copy the data here in case the caller
+                        * frees the in_buf
+                        */
+                       memcpy(buf->buf + header_len,
+                              in_buf + in_offset, copy_size);
+                       ret = 0; /* Emulate copy_from_user */
+               }
+               buf->len = header_len + copy_size - ret;
+               sg_init_one(sg, buf->buf, buf->len);
+
+               ret = out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, buf);
+               if (ret < 0) {
+                       /* FIXME: Put the buf back in the list */
+                       break;
+               }
+
+               in_offset += buf->len - header_len;
+               /* Only send size with the first buffer.  This way
+                * userspace can find out a continuous stream of data
+                * belonging to one write request and consume it
+                * appropriately
+                */
+               header.size = 0;
+
+               /* No space left anyway */
+               if (!ret)
+                       break;
+       }
+       /* Tell Host to go! */
+       out_vq->vq_ops->kick(out_vq);
 
-       /* Copy across to their buffer and increment offset. */
-       memcpy(buf, in, count);
-       in += count;
-       in_len -= count;
+       /* We're expected to return the amount of data we wrote */
+       return in_offset;
+}
+
+static ssize_t virtconsole_write(struct file *filp, const char __user *ubuf,
+                                size_t count, loff_t *offp)
+{
+       struct virtio_console_port *port;
 
-       /* Finished?  Re-register buffer so Host will use it again. */
-       if (in_len == 0)
-               add_inbuf();
+       port = filp->private_data;
 
-       return count;
+       return send_buf(port, ubuf, count, 0, true);
 }
-/*:*/
 
-/*D:320 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.
+static unsigned int virtconsole_poll(struct file *filp, poll_table *wait)
+{
+       struct virtio_console_port *port;
+       unsigned int ret;
+
+       port = filp->private_data;
+       poll_wait(filp, &port->waitqueue, wait);
+
+       ret = 0;
+       if (!list_empty(&port->readbuf_head))
+               ret |= POLLIN | POLLRDNORM;
+       if (!port->host_connected)
+               ret |= POLLHUP;
+
+       return ret;
+}
+
+static int virtconsole_release(struct inode *inode, struct file *filp)
+{
+       struct virtio_console_control cpkt;
+
+       /* Notify host of port being closed */
+       cpkt.event = VIRTIO_CONSOLE_PORT_OPEN;
+       cpkt.value = 0;
+       send_buf(filp->private_data, (char *)&cpkt, sizeof(cpkt),
+                VIRTIO_CONSOLE_ID_INTERNAL, false);
+       return 0;
+}
+
+static int virtconsole_open(struct inode *inode, struct file *filp)
+{
+       struct cdev *cdev = inode->i_cdev;
+       struct virtio_console_port *port;
+       struct virtio_console_control cpkt;
+
+       port = container_of(cdev, struct virtio_console_port, cdev);
+       filp->private_data = port;
+
+       /* Notify host of port being opened */
+       cpkt.event = VIRTIO_CONSOLE_PORT_OPEN;
+       cpkt.value = 1;
+       send_buf(filp->private_data, (char *)&cpkt, sizeof(cpkt),
+                VIRTIO_CONSOLE_ID_INTERNAL, false);
+
+       return 0;
+}
+
+static const struct file_operations virtconsole_fops = {
+       .owner = THIS_MODULE,
+       .open  = virtconsole_open,
+       .read  = virtconsole_read,
+       .write = virtconsole_write,
+       .poll  = virtconsole_poll,
+       .release = virtconsole_release,
+};
+
+/*D:310 The cons_put_chars() callback is pretty straightforward.
  *
- * 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))
+ * 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 cons_put_chars(u32 vtermno, const char *buf, int count)
 {
-       virtio_cons.put_chars = put_chars;
-       return hvc_instantiate(0, 0, &virtio_cons);
+       struct virtio_console_port *port;
+
+       port = get_port_from_id(vtermno);
+       if (!port)
+               return 0;
+
+       return send_buf(port, buf, count, 0, false);
 }
 
+/*D:350 cons_get_chars() is the callback from the hvc_console
+ * infrastructure when an interrupt is received.
+ *
+ * Most of the code deals with the fact that the hvc_console() infrastructure
+ * only asks us for 16 bytes at a time.  We keep in_offset and in_used fields
+ * for partially-filled buffers. */
+static int cons_get_chars(u32 vtermno, char *buf, int count)
+{
+       struct virtio_console_port *port;
+
+       /* If we don't have an input queue yet, we can't get input. */
+       BUG_ON(!virtconsole.in_vq);
+
+       port = get_port_from_id(vtermno);
+       if (!port)
+               return 0;
+
+       if (list_empty(&port->readbuf_head))
+               return 0;
+
+       return fill_readbuf(port, buf, count, false);
+
+}
+/*:*/
+
 /*
  * virtio console configuration. This supports:
  * - console resize
@@ -153,7 +433,11 @@ static void virtcons_apply_config(struct virtio_device 
*dev)
                dev->config->get(dev,
                                 offsetof(struct virtio_console_config, rows),
                                 &ws.ws_row, sizeof(u16));
-               hvc_resize(hvc, ws);
+               /* We'll use this way of resizing only for legacy support
+                * for newer userspace, use internal messages to indicate
+                * console size changes so that it can be done per-port
+                */
+               hvc_resize(get_port_from_id(VIRTIO_CONSOLE_CONSOLE_PORT)->hvc, 
ws);
        }
 }
 
@@ -161,23 +445,363 @@ static void virtcons_apply_config(struct virtio_device 
*dev)
  * we support only one console, the hvc struct is a global var
  * We set the configuration at this point, since we now have a tty
  */
-static int notifier_add_vio(struct hvc_struct *hp, int data)
+static int cons_notifier_add_vio(struct hvc_struct *hp, int data)
 {
        hp->irq_requested = 1;
-       virtcons_apply_config(vdev);
+       virtcons_apply_config(virtconsole.vdev);
 
        return 0;
 }
 
-static void notifier_del_vio(struct hvc_struct *hp, int data)
+static void cons_notifier_del_vio(struct hvc_struct *hp, int data)
 {
        hp->irq_requested = 0;
 }
 
-static void hvc_handle_input(struct virtqueue *vq)
+/* The operations for our console. */
+static struct hv_ops virtio_cons = {
+       .get_chars = cons_get_chars,
+       .put_chars = cons_put_chars,
+       .notifier_add = cons_notifier_add_vio,
+       .notifier_del = cons_notifier_del_vio,
+       .notifier_hangup = cons_notifier_del_vio,
+};
+
+/*D:320 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))
+{
+       virtio_cons.put_chars = put_chars;
+       return hvc_instantiate(0, 0, &virtio_cons);
+}
+
+static struct virtio_console_port_buffer *get_buf(size_t buf_size)
+{
+       struct virtio_console_port_buffer *buf;
+
+       buf = kzalloc(sizeof(*buf), GFP_KERNEL);
+       if (!buf)
+               goto out;
+       buf->buf = kzalloc(buf_size, GFP_KERNEL);
+       if (!buf->buf) {
+               kfree(buf);
+               goto out;
+       }
+       buf->len = buf_size;
+out:
+       return buf;
+}
+
+static void fill_queue(struct virtqueue *vq, size_t buf_size,
+                      struct list_head *unused_head)
 {
-       if (hvc_poll(hvc))
+       struct scatterlist sg[1];
+       struct virtio_console_port_buffer *buf;
+       int ret;
+
+       do {
+               buf = get_buf(buf_size);
+               if (!buf)
+                       break;
+               sg_init_one(sg, buf->buf, buf_size);
+
+               ret = vq->vq_ops->add_buf(vq, sg, 0, 1, buf);
+               if (ret < 0) {
+                       kfree(buf->buf);
+                       kfree(buf);
+                       break;
+               }
+               /* We have to keep track of the unused buffers
+                * so that they can be freed when the module
+                * is being removed
+                */
+               list_add_tail(&buf->next, unused_head);
+       } while (ret > 0);
+       vq->vq_ops->kick(vq);
+}
+
+static void fill_receive_queue(void)
+{
+       fill_queue(virtconsole.in_vq, PAGE_SIZE, &virtconsole.unused_read_head);
+}
+
+/* This function is only called from the init routine so the spinlock
+ * for the unused_write_head list isn't taken
+ */
+static void alloc_write_bufs(void)
+{
+       struct virtio_console_port_buffer *buf;
+       int i;
+
+       for (i = 0; i < 1024; i++) {
+               buf = get_buf(PAGE_SIZE);
+               if (!buf)
+                       break;
+               list_add_tail(&buf->next, &virtconsole.unused_write_head);
+       }
+}
+
+static void handle_control_message(struct virtio_console_port *port,
+                                  struct virtio_console_control *cpkt)
+{
+       switch (cpkt->event) {
+       case VIRTIO_CONSOLE_PORT_OPEN:
+               port->host_connected = cpkt->value;
+               break;
+       }
+}
+
+static void virtio_console_rx_work_handler(struct work_struct *work)
+{
+       struct virtio_console_port *port;
+       struct virtio_console_port_buffer *buf;
+       struct virtio_console_header header;
+       struct virtqueue *vq;
+       unsigned int tmplen, header_len;
+
+       header_len = use_multiport() ? sizeof(header) : 0;
+
+       port = NULL;
+       vq = virtconsole.in_vq;
+       while ((buf = vq->vq_ops->get_buf(vq, &tmplen))) {
+               /* The buffer is no longer unused */
+               list_del(&buf->next);
+
+               if (use_multiport()) {
+                       memcpy(&header, buf->buf, header_len);
+                       port = get_port_from_id(header.id);
+               } else
+                       port = get_port_from_id(VIRTIO_CONSOLE_CONSOLE_PORT);
+               if (!port) {
+                       /* No valid index at start of
+                        * buffer. Drop it.
+                        */
+                       pr_debug("%s: invalid index in buffer, %c %d\n",
+                                __func__, buf->buf[0], buf->buf[0]);
+                       kfree(buf->buf);
+                       kfree(buf);
+                       break;
+               }
+               if (use_multiport() && is_internal(header.flags)) {
+                       handle_control_message(port,
+                                              (struct virtio_console_control *)
+                                              (buf->buf + header_len));
+
+                       /* OPT: This buffer can be added to the
+                        * unused list to avoid free/alloc
+                        */
+                       kfree(buf->buf);
+                       kfree(buf);
+               } else {
+                       buf->len = tmplen;
+                       buf->offset = header_len;
+                       list_add_tail(&buf->next, &port->readbuf_head);
+                       /* We might have missed a connection
+                        * notification, e.g. before the queues were
+                        * initialised.
+                        */
+                       port->host_connected = true;
+               }
+               wake_up_interruptible(&port->waitqueue);
+       }
+       /* hvc_poll takes a spinlock and calls hvc_push which calls
+        * put_chars which results in a call to send_buf.
+        *
+        * It also calls get_chars with the spinlock held.
+        */
+       if (port && is_console_port(port) && hvc_poll(port->hvc))
                hvc_kick();
+
+       /* Allocate buffers for all the ones that got used up */
+       fill_receive_queue();
+}
+
+static void virtio_console_tx_work_handler(struct work_struct *work)
+{
+       struct virtqueue *vq;
+       struct virtio_console_port_buffer *buf;
+       unsigned int tmplen;
+
+       vq = virtconsole.out_vq;
+       while ((buf = vq->vq_ops->get_buf(vq, &tmplen))) {
+               /* 0 the buffer to not leak data from other processes */
+               memset(buf->buf, 0, buf->len);
+               spin_lock(&virtconsole.write_list_lock);
+               list_add_tail(&buf->next, &virtconsole.unused_write_head);
+               spin_unlock(&virtconsole.write_list_lock);
+       }
+}
+
+static void rx_intr(struct virtqueue *vq)
+{
+       schedule_work(&virtconsole.rx_work);
+}
+
+static void tx_intr(struct virtqueue *vq)
+{
+       schedule_work(&virtconsole.tx_work);
+}
+
+static void config_intr(struct virtio_device *vdev)
+{
+       /* Handle port hot-add */
+       schedule_work(&virtconsole.config_work);
+
+       /* Handle console size changes */
+       virtcons_apply_config(vdev);
+}
+
+static u32 virtconsole_get_hot_add_port(struct virtio_console_config *config)
+{
+       u32 i;
+       u32 port_nr;
+
+       for (i = 0; i < virtconsole.config->max_nr_ports / 32; i++) {
+               port_nr = ffs(config->ports_map[i] ^ 
virtconsole.config->ports_map[i]);
+               if (port_nr)
+                       break;
+       }
+       if (unlikely(!port_nr))
+               return VIRTIO_CONSOLE_BAD_ID;
+
+       /* We used ffs above */
+       port_nr--;
+
+       /* FIXME: Do this only when add_port is successful */
+       virtconsole.config->ports_map[i] |= 1U << port_nr;
+
+       port_nr += i * 32;
+       return port_nr;
+}
+
+static u32 virtconsole_find_next_port(u32 *map, int *map_i)
+{
+       u32 port_nr;
+
+       while (1) {
+               port_nr = ffs(*map);
+               if (port_nr)
+                       break;
+
+               if (unlikely(*map_i >= virtconsole.config->max_nr_ports / 32))
+                       return VIRTIO_CONSOLE_BAD_ID;
+               ++*map_i;
+               *map = virtconsole.config->ports_map[*map_i];
+       }
+       /* We used ffs above */
+       port_nr--;
+
+       /* FIXME: Do this only when add_port is successful / reset bit
+        * in config space if add_port was unsuccessful
+        */
+       *map &= ~(1U << port_nr);
+
+       port_nr += *map_i * 32;
+       return port_nr;
+}
+
+static int virtconsole_add_port(u32 port_nr)
+{
+       struct virtio_console_port *port;
+       dev_t devt;
+       int ret;
+
+       port = kzalloc(sizeof(*port), GFP_KERNEL);
+       if (!port)
+               return -ENOMEM;
+
+       devt = MKDEV(major, port_nr);
+       cdev_init(&port->cdev, &virtconsole_fops);
+
+       ret = register_chrdev_region(devt, 1, "virtio-console");
+       if (ret < 0) {
+               pr_err("%s: error registering chrdev region, ret = %d\n",
+                      __func__, ret);
+               goto free_cdev;
+       }
+       ret = cdev_add(&port->cdev, devt, 1);
+       if (ret < 0) {
+               pr_err("%s: error adding cdev, ret = %d\n", __func__, ret);
+               goto free_cdev;
+       }
+       port->dev = device_create(virtconsole.class, NULL, devt, NULL,
+                                 "vcon%u", port_nr);
+       if (IS_ERR(port->dev)) {
+               ret = PTR_ERR(port->dev);
+               pr_err("%s: Error creating device, ret = %d\n", __func__, ret);
+               goto free_cdev;
+       }
+       INIT_LIST_HEAD(&port->readbuf_head);
+       init_waitqueue_head(&port->waitqueue);
+
+       list_add_tail(&port->next, &virtconsole.port_head);
+
+       if (is_console_port(port)) {
+               /* The first argument of hvc_alloc() is the virtual
+                * console number, so we use zero.  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->hvc = hvc_alloc(port_nr, 0, &virtio_cons, PAGE_SIZE);
+               if (IS_ERR(port->hvc)) {
+                       ret = PTR_ERR(port->hvc);
+                       goto free_cdev;
+               }
+       }
+       pr_info("virtio-console port found at id %u\n", port_nr);
+
+       return 0;
+free_cdev:
+       unregister_chrdev(major, "virtio-console");
+       return ret;
+}
+
+static u32 get_ports_map_size(u32 max_ports)
+{
+       return sizeof(u32) * ((max_ports + 31) / 32);
+}
+
+static void virtio_console_config_work_handler(struct work_struct *work)
+{
+       struct virtio_console_config *virtconconf;
+       struct virtio_device *vdev = virtconsole.vdev;
+       u32 i, port_nr;
+       int ret;
+
+       virtconconf = kzalloc(sizeof(*virtconconf) +
+                             
get_ports_map_size(virtconsole.config->max_nr_ports),
+                             GFP_KERNEL);
+       vdev->config->get(vdev,
+                         offsetof(struct virtio_console_config, 
nr_active_ports),
+                         &virtconconf->nr_active_ports,
+                         sizeof(virtconconf->nr_active_ports));
+       vdev->config->get(vdev,
+                         offsetof(struct virtio_console_config, ports_map),
+                         virtconconf->ports_map,
+                         get_ports_map_size(virtconsole.config->max_nr_ports));
+
+       /* Hot-add ports */
+       for (i = virtconsole.config->nr_active_ports;
+            i < virtconconf->nr_active_ports; i++) {
+               port_nr = virtconsole_get_hot_add_port(virtconconf);
+               if (port_nr == VIRTIO_CONSOLE_BAD_ID)
+                       continue;
+               ret = virtconsole_add_port(port_nr);
+               if (!ret)
+                       virtconsole.config->nr_active_ports++;
+       }
+       kfree(virtconconf);
 }
 
 /*D:370 Once we're further in boot, we get probed like any other virtio device.
@@ -187,64 +811,143 @@ static void hvc_handle_input(struct virtqueue *vq)
  * never remove the console device we never need this pointer again.
  *
  * Finally we put our input buffer in the input queue, ready to receive. */
-static int __devinit virtcons_probe(struct virtio_device *dev)
+static int __devinit virtcons_probe(struct virtio_device *vdev)
 {
-       vq_callback_t *callbacks[] = { hvc_handle_input, NULL};
+       vq_callback_t *callbacks[] = { rx_intr, tx_intr };
        const char *names[] = { "input", "output" };
        struct virtqueue *vqs[2];
-       int err;
-
-       vdev = dev;
-
-       /* This is the scratch page we use to receive console input */
-       inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
-       if (!inbuf) {
-               err = -ENOMEM;
-               goto fail;
+       u32 i, map;
+       int ret, map_i;
+       u32 max_nr_ports;
+       bool multiport;
+
+       virtconsole.vdev = vdev;
+
+       multiport = false;
+       if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_MULTIPORT)) {
+               multiport = true;
+               vdev->features[0] |= 1 << VIRTIO_CONSOLE_F_MULTIPORT;
+               vdev->config->finalize_features(vdev);
+
+               vdev->config->get(vdev,
+                                 offsetof(struct virtio_console_config,
+                                          max_nr_ports),
+                                 &max_nr_ports,
+                                 sizeof(max_nr_ports));
+               virtconsole.config = kzalloc(sizeof(struct 
virtio_console_config)
+                                            + get_ports_map_size(max_nr_ports),
+                                            GFP_KERNEL);
+               if (!virtconsole.config)
+                       return -ENOMEM;
+               virtconsole.config->max_nr_ports = max_nr_ports;
+
+               vdev->config->get(vdev, offsetof(struct virtio_console_config,
+                                                nr_active_ports),
+                                 &virtconsole.config->nr_active_ports,
+                                 sizeof(virtconsole.config->nr_active_ports));
+               vdev->config->get(vdev,
+                                 offsetof(struct virtio_console_config,
+                                          ports_map),
+                                 virtconsole.config->ports_map,
+                                 get_ports_map_size(max_nr_ports));
        }
-
        /* Find the queues. */
        /* FIXME: This is why we want to wean off hvc: we do nothing
         * when input comes in. */
-       err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
-       if (err)
-               goto free;
+       ret = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
+       if (ret)
+               goto fail;
 
-       in_vq = vqs[0];
-       out_vq = vqs[1];
+       virtconsole.in_vq = vqs[0];
+       virtconsole.out_vq = vqs[1];
+
+       INIT_LIST_HEAD(&virtconsole.port_head);
+       INIT_LIST_HEAD(&virtconsole.unused_read_head);
+       INIT_LIST_HEAD(&virtconsole.unused_write_head);
+
+       if (multiport) {
+               map_i = 0;
+               map = virtconsole.config->ports_map[map_i];
+               for (i = 0; i < virtconsole.config->nr_active_ports; i++) {
+                       u32 port_nr;
+
+                       port_nr = virtconsole_find_next_port(&map, &map_i);
+                       if (unlikely(port_nr == VIRTIO_CONSOLE_BAD_ID))
+                               continue;
+                       virtconsole_add_port(port_nr);
+               }
+       } else
+               virtconsole_add_port(VIRTIO_CONSOLE_CONSOLE_PORT);
+
+       INIT_WORK(&virtconsole.rx_work, &virtio_console_rx_work_handler);
+       INIT_WORK(&virtconsole.tx_work, &virtio_console_tx_work_handler);
+       INIT_WORK(&virtconsole.config_work, 
&virtio_console_config_work_handler);
+       spin_lock_init(&virtconsole.write_list_lock);
+
+       fill_receive_queue();
+       alloc_write_bufs();
+       return 0;
 
-       /* Start using the new console output. */
-       virtio_cons.get_chars = get_chars;
-       virtio_cons.put_chars = put_chars;
-       virtio_cons.notifier_add = notifier_add_vio;
-       virtio_cons.notifier_del = notifier_del_vio;
-       virtio_cons.notifier_hangup = notifier_del_vio;
-
-       /* The first argument of hvc_alloc() is the virtual console number, so
-        * we use zero.  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. */
-       hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE);
-       if (IS_ERR(hvc)) {
-               err = PTR_ERR(hvc);
-               goto free_vqs;
+fail:
+       return ret;
+}
+
+static void virtcons_remove_port_data(struct virtio_console_port *port)
+{
+       struct virtio_console_port_buffer *buf, *buf2;
+
+#if 0 /* hvc_console is compiled in, at least on Fedora. */
+       if (is_console_port(port))
+               hvc_remove(hvc);
+#endif
+       device_destroy(virtconsole.class, port->dev->devt);
+       unregister_chrdev_region(port->dev->devt, 1);
+       cdev_del(&port->cdev);
+
+       /* Remove the buffers in which we have unconsumed data */
+       list_for_each_entry_safe(buf, buf2, &port->readbuf_head, next) {
+               list_del(&buf->next);
+               kfree(buf->buf);
+               kfree(buf);
        }
+}
 
-       /* Register the input buffer the first time. */
-       add_inbuf();
-       return 0;
+static void virtcons_remove(struct virtio_device *vdev)
+{
+       struct virtio_console_port *port, *port2;
+       struct virtio_console_port_buffer *buf, *buf2;
+       char *tmpbuf;
+       int len;
+
+       unregister_chrdev(major, "virtio-console");
+       class_destroy(virtconsole.class);
+
+       cancel_work_sync(&virtconsole.rx_work);
+
+       /* Free up the buffers in the 'received' queue */
+       while ((tmpbuf = virtconsole.in_vq->vq_ops->get_buf(virtconsole.in_vq,
+                                                           &len)))
+               kfree(tmpbuf);
 
-free_vqs:
        vdev->config->del_vqs(vdev);
-free:
-       kfree(inbuf);
-fail:
-       return err;
+
+       /* Free up the buffers that were unused */
+       list_for_each_entry_safe(buf, buf2, &virtconsole.unused_read_head, 
next) {
+               list_del(&buf->next);
+               kfree(buf->buf);
+               kfree(buf);
+       }
+       list_for_each_entry_safe(buf, buf2, &virtconsole.unused_write_head, 
next) {
+               list_del(&buf->next);
+               kfree(buf->buf);
+               kfree(buf);
+       }
+       list_for_each_entry_safe(port, port2, &virtconsole.port_head, next) {
+               list_del(&port->next);
+               virtcons_remove_port_data(port);
+               kfree(port);
+       }
+       kfree(virtconsole.config);
 }
 
 static struct virtio_device_id id_table[] = {
@@ -254,6 +957,7 @@ static struct virtio_device_id id_table[] = {
 
 static unsigned int features[] = {
        VIRTIO_CONSOLE_F_SIZE,
+       VIRTIO_CONSOLE_F_MULTIPORT,
 };
 
 static struct virtio_driver virtio_console = {
@@ -263,14 +967,34 @@ static struct virtio_driver virtio_console = {
        .driver.owner = THIS_MODULE,
        .id_table =     id_table,
        .probe =        virtcons_probe,
-       .config_changed = virtcons_apply_config,
+       .remove =       virtcons_remove,
+       .config_changed = config_intr,
 };
 
 static int __init init(void)
 {
-       return register_virtio_driver(&virtio_console);
+       int ret;
+
+       virtconsole.class = class_create(THIS_MODULE, "virtio-console");
+       if (IS_ERR(virtconsole.class)) {
+               pr_err("Error creating virtio-console class\n");
+               ret = PTR_ERR(virtconsole.class);
+               return ret;
+       }
+       ret = register_virtio_driver(&virtio_console);
+       if (ret) {
+               class_destroy(virtconsole.class);
+               return ret;
+       }
+       return 0;
+}
+
+static void __exit fini(void)
+{
+       unregister_virtio_driver(&virtio_console);
 }
 module_init(init);
+module_exit(fini);
 
 MODULE_DEVICE_TABLE(virtio, id_table);
 MODULE_DESCRIPTION("Virtio console driver");
diff --git a/include/linux/virtio_console.h b/include/linux/virtio_console.h
index b5f5198..9a3a3b9 100644
--- a/include/linux/virtio_console.h
+++ b/include/linux/virtio_console.h
@@ -7,14 +7,48 @@
 
 /* Feature bits */
 #define VIRTIO_CONSOLE_F_SIZE  0       /* Does host provide console size? */
+#define VIRTIO_CONSOLE_F_MULTIPORT 1   /* Does host provide multiple ports? */
+
+#define VIRTIO_CONSOLE_BAD_ID  (~(u32)0) /* Invalid port number */
+
+/* Port at which the virtio console is spawned */
+#define VIRTIO_CONSOLE_CONSOLE_PORT    0
+#define VIRTIO_CONSOLE_CONSOLE2_PORT   1
 
 struct virtio_console_config {
        /* colums of the screens */
        __u16 cols;
        /* rows of the screens */
        __u16 rows;
+       /* max. number of ports supported for each PCI device */
+       __u32 max_nr_ports;
+       /* number of ports in use */
+       __u32 nr_active_ports;
+       /* locations of the ports in use */
+       __u32 ports_map[0 /* (max_nr_ports + 31) / 32 */];
+} __attribute__((packed));
+
+struct virtio_console_control {
+       __u16 event;
+       __u16 value;
+};
+
+/* This struct is put in each buffer that gets passed to userspace and
+ * vice-versa
+ */
+struct virtio_console_header {
+       u32 id; /* Port number */
+       u32 flags; /* Some message between host and guest */
+       u32 size; /* Complete size of the write request - only sent
+                  * with the first buffer for each write request
+                  */
 } __attribute__((packed));
 
+/* Messages between host and guest */
+#define VIRTIO_CONSOLE_ID_INTERNAL     (1 << 0)
+
+/* Some events for internal messages */
+#define VIRTIO_CONSOLE_PORT_OPEN       0
 
 #ifdef __KERNEL__
 int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int));
-- 
1.6.2.5





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