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SubjectRe: [PATCH] virtio_console: Add support for multiple ports for generic guest and host communication
On (Tue) Sep 29 2009 [15:31:23], Christian Borntraeger wrote:
> Am Dienstag 29 September 2009 15:09:50 schrieb Amit Shah:
> > Great, thanks. However I was thinking of moving this init to the probe()
> > routine instead of in the init_conosle routine just because multiple
> > consoles can be added and we don't want to init this each time.. just
> > once in probe is fine.
>
> If you have new patch CC me and I can give it a spin.

Hey Christian,

I have a new patch that changes a few things:
- moves the put_char fix to probe instead of doing it in
init_port_console(), which gets called on each console port found.
- uses port->id instead of a static hvc_vtermno to pass on a value to
hvc_alloc(). Motivation explained within comments in the code.
- A few other changes that introduce and make use of port->vcon instead
of accessing the static virtconsole directly -- aimed at easing future
fix to have multiple virtio-console devices.

It would be great if you could test this.

Amit


diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 6a06913..7b4602f 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -679,6 +679,12 @@ config VIRTIO_CONSOLE
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. If specified by the host, a sysfs attribute called
+ 'name' will be populated with a name for the port which can
+ be used by udev scripts to create a symlink to /dev/vconNN.

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..16cdcec 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -9,10 +9,8 @@
* functions.
:*/

-/*M:002 The console can be flooded: while the Guest is processing input the
- * 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
@@ -28,115 +26,468 @@
* 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
- * operations for them. */
-static struct virtqueue *in_vq, *out_vq;
-static struct virtio_device *vdev;
+/* This struct stores data that's common to all the ports */
+struct virtio_console_struct {
+ /*
+ * Workqueue handlers where we process deferred work after an
+ * interrupt
+ */
+ 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;
+ /* The input and the output queues */
+ 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)
+ /* The current config space is stored here */
+ 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;
+
+ /* length of the buffer */
+ size_t len;
+ /* offset in the buf from which to consume data */
+ size_t offset;
+};
+
+/* This struct holds the per-port data */
+struct virtio_console_port {
+ /* Next port in the list, head is in the virtio_console_struct */
+ struct list_head next;
+
+ /* Pointer to the virtio_console device */
+ struct virtio_console_struct *vcon;
+
+ /* Buffer management */
+ struct list_head readbuf_head;
+
+ /* A waitqueue for poll() or blocking read operations */
+ 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;
+
+ /* The 'name' of the port that we expose via sysfs properties */
+ char *name;
+
+ /* The 'id' to identify the port with the Host */
+ u32 id;
+
+ /* Is the host device open */
+ bool host_connected;
+};
+
+static struct virtio_console_struct virtconsole;
+
+static struct virtio_console_port *get_port_from_devt(dev_t devt)
{
- 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 (port->dev->devt == devt)
+ return port;
}
+ return NULL;
+}
+
+static struct virtio_console_port *get_port_from_id(u32 id)
+{
+ struct virtio_console_port *port;

- /* We're expected to return the amount of data we wrote: all of it. */
- return count;
+ list_for_each_entry(port, &virtconsole.port_head, next) {
+ if (port->id == id)
+ return port;
+ }
+ return NULL;
}

-/* Create a scatter-gather list representing our input buffer and put it in the
- * queue. */
-static void add_inbuf(void)
+static int get_id_from_port(struct virtio_console_port *port)
{
- struct scatterlist sg[1];
- sg_init_one(sg, inbuf, PAGE_SIZE);
+ return port->id;
+}

- /* 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);
+static bool is_console_port(struct virtio_console_port *port)
+{
+ if (port->hvc)
+ 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;
+}
+
+/*
+ * Give out the data that's requested from the buffers that we have
+ * queued up per port
+ */
+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;
+}
+
+/* The condition that must be true for polling to end */
+static bool wait_is_over(struct virtio_console_port *port)
+{
+ return !list_empty(&port->readbuf_head) || !port->host_connected;
+}
+
+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;

- /* No buffer? Try to get one. */
- if (!in_len) {
- in = in_vq->vq_ops->get_buf(in_vq, &in_len);
- if (!in)
+ 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;

- /* You want more than we have to give? Well, try wanting less! */
- if (in_len < count)
- count = in_len;
+ 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 should not send internal messages to a host that won't
+ * understand them
+ */
+ 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);
+ }
+ in_offset = 0; /* offset in the user buffer */
+ while (in_count - in_offset) {
+ copy_size = min(in_count - in_offset + header_len, PAGE_SIZE);

- /* Copy across to their buffer and increment offset. */
- memcpy(buf, in, count);
- in += count;
- in_len -= count;
+ 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 behaviour */
+ }
+ buf->len = header_len + copy_size - ret;
+ sg_init_one(sg, buf->buf, buf->len);

- /* Finished? Re-register buffer so Host will use it again. */
- if (in_len == 0)
- add_inbuf();
+ ret = out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, buf);
+ if (ret < 0) {
+ 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);
+ 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;

- return count;
+ /* No space left in the vq anyway */
+ if (!ret)
+ break;
+ }
+ /* Tell Host to go! */
+ out_vq->vq_ops->kick(out_vq);
+
+ /* We're expected to return the amount of data we wrote */
+ return in_offset;
}
-/*:*/

-/*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 ssize_t virtconsole_write(struct file *filp, const char __user *ubuf,
+ size_t count, loff_t *offp)
+{
+ struct virtio_console_port *port;
+
+ port = filp->private_data;
+
+ return send_buf(port, ubuf, count, 0, true);
+}
+
+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;
+}
+
+/*
+ * 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/vconNN
+ */
+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,
+};
+
+
+static ssize_t show_port_name(struct device *dev,
+ struct device_attribute *attr, char *buffer)
+{
+ struct virtio_console_port *port;
+
+ port = get_port_from_devt(dev->devt);
+ if (!port || !port->name)
+ return 0;
+
+ return sprintf(buffer, "%s\n", port->name);
+}
+
+static DEVICE_ATTR(name, S_IRUGO, show_port_name, NULL);
+
+static struct attribute *virtcon_sysfs_entries[] = {
+ &dev_attr_name.attr,
+ NULL
+};
+
+static struct attribute_group virtcon_attribute_group = {
+ .name = NULL, /* put in device directory */
+ .attrs = virtcon_sysfs_entries,
+};
+
+
+/*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.
+ *
+ * If the data to be outpu spans more than a page, it's split into
+ * page-sized buffers and then individual buffers are pushed to Host.
+ */
+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.
+ *
+ * We call out to fill_readbuf that gets us the required data from the
+ * buffers that are queued up.
+ */
+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:
@@ -153,98 +504,579 @@ 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 (VIRTIO_CONSOLE_F_MULTPORT+),
+ * use internal messages to indicate console size
+ * changes so that it can be done per-port
+ */
+ if (!use_multiport())
+ hvc_resize(get_port_from_id(0)->hvc, ws);
}
}

/*
- * 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))
{
- if (hvc_poll(hvc))
- hvc_kick();
+ virtio_cons.put_chars = put_chars;
+ return hvc_instantiate(0, 0, &virtio_cons);
}

-/*D:370 Once we're further in boot, we get probed like any other virtio device.
- * At this stage we set up the output virtqueue.
+int init_port_console(struct virtio_console_port *port)
+{
+ int ret = 0;
+
+ /*
+ * 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. hvc_alloc() checks if a console with the same value
+ * was used in hvc_instantiate(). We may not end up passing
+ * the same value here (we use the value 0 in
+ * hvc_instantiate() but the console port may not be at id
+ * 0). This isn't a problem, though. Nothing in hvc really
+ * depends on these numbers and since this number is passed on
+ * to us when cons_get/put_chars() is called, it's preferable
+ * to pass on the port->id so that we can get the port struct
+ * via get_port_from_id().
+ *
+ * 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->id, 0, &virtio_cons, PAGE_SIZE);
+ if (IS_ERR(port->hvc)) {
+ ret = PTR_ERR(port->hvc);
+ pr_err("%s: Could not alloc hvc for virtio console port, ret = %d\n",
+ __func__, ret);
+ port->hvc = NULL;
+ }
+ return ret;
+}
+
+/* Any secret messages that the Host and Guest want to share */
+static void handle_control_message(struct virtio_console_port *port,
+ struct virtio_console_port_buffer *buf)
+{
+ struct virtio_console_control *cpkt;
+ size_t name_size;
+
+ cpkt = (struct virtio_console_control *)(buf->buf + buf->offset);
+
+ switch (cpkt->event) {
+ case VIRTIO_CONSOLE_PORT_OPEN:
+ port->host_connected = cpkt->value;
+ break;
+ case VIRTIO_CONSOLE_PORT_NAME:
+ /*
+ * 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) {
+ pr_err("%s: not enough space to store port name\n",
+ __func__);
+ break;
+ }
+ strncpy(port->name, buf->buf + buf->offset + sizeof(*cpkt),
+ name_size - 1);
+ port->name[name_size - 1] = 0;
+ break;
+ case VIRTIO_CONSOLE_CONSOLE_PORT:
+ if (!cpkt->value)
+ break;
+ init_port_console(port);
+ /*
+ * Could remove the port here in case init fails - but
+ * have to notify the host first
+ */
+ break;
+ }
+}
+
+
+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)
+{
+ 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(struct virtio_console_struct *vcon)
+{
+ fill_queue(vcon->in_vq, PAGE_SIZE, &vcon->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(struct virtio_console_struct *vcon)
+{
+ 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, &vcon->unused_write_head);
+ }
+}
+
+/*
+ * The workhandler for any buffers that appear on our input queue.
+ * Pick the buffer; if it's some internal communication meant for the
+ * us, just process it. Otherwise queue it up for the read() or
+ * get_chars() routines to pick the data up later.
+ */
+static void virtio_console_rx_work_handler(struct work_struct *work)
+{
+ struct virtio_console_struct *vcon;
+ struct virtio_console_port *port;
+ struct virtio_console_port_buffer *buf;
+ struct virtio_console_header header;
+ struct virtqueue *vq;
+ unsigned int tmplen, header_len;
+
+ vcon = container_of(work, struct virtio_console_struct, rx_work);
+ header_len = use_multiport() ? sizeof(header) : 0;
+
+ port = NULL;
+ vq = vcon->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(0);
+ if (!port) {
+ /* No valid header at start of buffer. Drop it. */
+ pr_debug("%s: invalid index in buffer, %c %d\n",
+ __func__, buf->buf[0], buf->buf[0]);
+ /*
+ * OPT: This buffer can be added to the unused
+ * list to avoid free / alloc
+ */
+ kfree(buf->buf);
+ kfree(buf);
+ break;
+ }
+ buf->len = tmplen;
+ buf->offset = header_len;
+ if (use_multiport() && is_internal(header.flags)) {
+ handle_control_message(port, buf);
+ /*
+ * OPT: This buffer can be added to the unused
+ * list to avoid free/alloc
+ */
+ kfree(buf->buf);
+ kfree(buf);
+ } else {
+ 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);
+ }
+ if (port) {
+ if(is_console_port(port) && !list_empty(&port->readbuf_head))
+ if (hvc_poll(port->hvc))
+ hvc_kick();
+ /* Allocate buffers for all the ones that got used up */
+ fill_receive_queue(port->vcon);
+ }
+}
+
+/*
+ * This is the workhandler for buffers that get received on the output
+ * virtqueue, which is an indication that Host consumed the data we
+ * sent it. Since all our buffers going out are of a fixed size we can
+ * just reuse them instead of freeing them and allocating new ones.
*
- * To set up and manage our virtual console, we call hvc_alloc(). Since we
- * never remove the console device we never need this pointer again.
+ * Zero out the buffer so that we don't leak any information from
+ * other processes. There's a small optimisation here as well: the
+ * buffers are PAGE_SIZE-sized; but instead of zeroing the entire
+ * page, we just zero the length that was most recently used and we
+ * can be sure the rest of the page is already set to 0s.
*
- * Finally we put our input buffer in the input queue, ready to receive. */
-static int __devinit virtcons_probe(struct virtio_device *dev)
+ * So once we zero them out we add them back to the unused buffers
+ * list
+ */
+static void virtio_console_tx_work_handler(struct work_struct *work)
{
- vq_callback_t *callbacks[] = { hvc_handle_input, NULL};
+ struct virtio_console_struct *vcon;
+ struct virtqueue *vq;
+ struct virtio_console_port_buffer *buf;
+ unsigned int tmplen;
+
+ vcon = container_of(work, struct virtio_console_struct, tx_work);
+
+ vq = vcon->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(&vcon->write_list_lock);
+ list_add_tail(&buf->next, &vcon->unused_write_head);
+ spin_unlock(&vcon->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 int virtconsole_add_port(u32 port_nr)
+{
+ struct virtio_console_port *port;
+ struct virtio_console_control cpkt;
+ dev_t devt;
+ int ret;
+
+ port = kzalloc(sizeof(*port), GFP_KERNEL);
+ if (!port)
+ return -ENOMEM;
+
+ port->vcon = &virtconsole;
+ port->id = port_nr;
+
+ cdev_init(&port->cdev, &virtconsole_fops);
+
+ ret = alloc_chrdev_region(&devt, 0, 1, "virtio-console");
+ if (ret < 0) {
+ pr_err("%s: error allocing chrdev region, ret = %d\n",
+ __func__, ret);
+ goto free_port;
+ }
+ ret = cdev_add(&port->cdev, devt, 1);
+ if (ret < 0) {
+ pr_err("%s: error adding cdev, ret = %d\n", __func__, ret);
+ goto free_chrdev;
+ }
+ port->dev = device_create(port->vcon->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;
+ }
+ ret = sysfs_create_group(&port->dev->kobj, &virtcon_attribute_group);
+ if (ret) {
+ pr_err("%s: error creating sysfs device attributes, ret = %d\n",
+ __func__, ret);
+ goto free_cdev;
+ }
+
+ INIT_LIST_HEAD(&port->readbuf_head);
+ init_waitqueue_head(&port->waitqueue);
+
+ list_add_tail(&port->next, &port->vcon->port_head);
+
+ /*
+ * Ask for the port's name from Host. The string that we
+ * receive in 'name' can be of arbitrary length; so pass the
+ * maximum available buffer size: PAGE_SIZE.
+ */
+ cpkt.event = VIRTIO_CONSOLE_PORT_NAME;
+ send_buf(port, (char *)&cpkt, sizeof(cpkt),
+ VIRTIO_CONSOLE_ID_INTERNAL, false);
+
+ /*
+ * If we're not using multiport support, this has to be a console port
+ */
+ if (!use_multiport()) {
+ ret = init_port_console(port);
+ if (ret)
+ goto free_cdev;
+ }
+
+ pr_debug("virtio-console port found at id %u\n", port_nr);
+
+ return 0;
+free_cdev:
+ cdev_del(&port->cdev);
+free_chrdev:
+ unregister_chrdev_region(devt, 1);
+free_port:
+ kfree(port);
+ return ret;
+}
+
+
+/* The workhandler for config-space updates
+ *
+ * This is used when new ports are added
+ */
+static void virtio_console_config_work_handler(struct work_struct *work)
+{
+ struct virtio_console_struct *vcon;
+ struct virtio_console_config virtconconf;
+ struct virtio_device *vdev;
+ u32 i;
+ int ret;
+
+ vcon = container_of(work, struct virtio_console_struct, config_work);
+
+ vdev = vcon->vdev;
+ vdev->config->get(vdev,
+ offsetof(struct virtio_console_config, nr_active_ports),
+ &virtconconf.nr_active_ports,
+ sizeof(virtconconf.nr_active_ports));
+
+ /* Hot-add ports */
+ for (i = virtconsole.config.nr_active_ports;
+ i < virtconconf.nr_active_ports; i++) {
+ ret = virtconsole_add_port(virtconsole.config.nr_active_ports + i);
+ if (!ret)
+ virtconsole.config.nr_active_ports++;
+ }
+}
+
+/*D:370
+ * Once we're further in boot, we get probed like any other virtio device.
+ * At this stage we set up the output virtqueue.
+ *
+ * Finally we put our input buffer in the input queue, ready to receive.
+ */
+static int __devinit virtcons_probe(struct virtio_device *vdev)
+{
+ vq_callback_t *callbacks[] = { rx_intr, tx_intr };
const char *names[] = { "input", "output" };
struct virtqueue *vqs[2];
- int err;
+ u32 i;
+ int ret;
+ bool multiport;

- 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;
+ if (virtconsole.vdev) {
+ pr_err("Multiple virtio-console devices not supported yet\n");
+ return -EEXIST;
}
+ 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,
+ nr_active_ports),
+ &virtconsole.config.nr_active_ports,
+ sizeof(virtconsole.config.nr_active_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];

- /* 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;
+ /*
+ * We had set the virtio_cons put_chars implementation to
+ * put_chars for early_init. Now that we're done with the
+ * early init phase, replace it with our cons_put_chars
+ * implementation.
+ */
+ virtio_cons.put_chars = cons_put_chars;
+
+ INIT_LIST_HEAD(&virtconsole.port_head);
+ INIT_LIST_HEAD(&virtconsole.unused_read_head);
+ INIT_LIST_HEAD(&virtconsole.unused_write_head);
+
+ 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(&virtconsole);
+ alloc_write_bufs(&virtconsole);
+
+ virtconsole_add_port(0);
+ if (multiport)
+ for (i = 1; i < virtconsole.config.nr_active_ports; i++)
+ virtconsole_add_port(i);
+
+ return 0;
+
+fail:
+ return ret;
+}
+
+/*
+ * Remove port-specific data.
+ * In case the port can't be removed, return non-zero. This could
+ * then be used in the port hot-unplug case.
+ */
+static int virtcons_remove_port_data(struct virtio_console_port *port)
+{
+ struct virtio_console_port_buffer *buf, *buf2;
+
+ if (is_console_port(port)) {
+ /* hvc_console is compiled in, at least on Fedora. */
+ /* hvc_remove(hvc); */
+ return 1;
}

- /* Register the input buffer the first time. */
- add_inbuf();
+ sysfs_remove_group(&port->dev->kobj, &virtcon_attribute_group);
+ device_destroy(virtconsole.class, port->dev->devt);
+ unregister_chrdev_region(port->dev->devt, 1);
+ cdev_del(&port->cdev);
+
+ kfree(port->name);
+
+ /* 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);
+ }
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;
+
+ class_destroy(virtconsole.class);
+
+ cancel_work_sync(&virtconsole.rx_work);
+ /*
+ * Free up the buffers that we queued up for the Host to pass
+ * us data
+ */
+ 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 sent to us by Host but were
+ * left 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);
+ }
}

static struct virtio_device_id id_table[] = {
@@ -254,6 +1086,7 @@ 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 +1096,34 @@ 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..96bb6f0 100644
--- a/include/linux/virtio_console.h
+++ b/include/linux/virtio_console.h
@@ -2,19 +2,63 @@
#define _LINUX_VIRTIO_CONSOLE_H
#include <linux/types.h>
#include <linux/virtio_config.h>
-/* This header, excluding the #ifdef __KERNEL__ part, is BSD licensed so
- * anyone can use the definitions to implement compatible drivers/servers. */
+/*
+ * This header, excluding the #ifdef __KERNEL__ part, is BSD licensed so
+ * anyone can use the definitions to implement compatible drivers/servers.
+ *
+ * Copyright (C) Red Hat, Inc., 2009
+ */

/* 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 */

struct virtio_console_config {
/* colums of the screens */
__u16 cols;
/* rows of the screens */
__u16 rows;
+ /* number of ports in use */
+ __u32 nr_active_ports;
+} __attribute__((packed));
+
+
+/*
+ * An internal-only message that's passed between the Host and the
+ * Guest for a particular port.
+ */
+struct virtio_console_control {
+ __u16 event;
+ __u16 value;
+};
+
+/* Some events for internal messages (control packets) */
+#define VIRTIO_CONSOLE_PORT_OPEN 0
+#define VIRTIO_CONSOLE_PORT_NAME 1
+#define VIRTIO_CONSOLE_CONSOLE_PORT 2
+
+
+/*
+ * This struct is put in each buffer that gets passed to userspace and
+ * vice-versa
+ */
+struct virtio_console_header {
+ /* Port number */
+ u32 id;
+ /* Some message between host and guest */
+ u32 flags;
+ /*
+ * Complete size of the write request - only sent with the
+ * first buffer for each write request
+ */
+ u32 size;
} __attribute__((packed));

+/* Messages between host and guest ('flags' field in the header above) */
+#define VIRTIO_CONSOLE_ID_INTERNAL (1 << 0)
+

#ifdef __KERNEL__
int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int));

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  Last update: 2009-09-30 19:17    [from the cache]
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