/*
* The Virtio 9p transport driver
*
* This is a block based transport driver based on the lguest block driver
* code.
*
* Copyright (C) 2007, 2008 Eric Van Hensbergen, IBM Corporation
*
* Based on virtio console driver
* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* 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:
* Free Software Foundation
* 51 Franklin Street, Fifth Floor
* Boston, MA 02111-1301 USA
*
*/
#include <linux/in.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/ipv6.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/un.h>
#include <linux/uaccess.h>
#include <linux/inet.h>
#include <linux/idr.h>
#include <linux/file.h>
#include <net/9p/9p.h>
#include <linux/parser.h>
#include <net/9p/client.h>
#include <net/9p/transport.h>
#include <linux/scatterlist.h>
#include <linux/virtio.h>
#include <linux/virtio_9p.h>
#define VIRTQUEUE_NUM 128
/* a single mutex to manage channel initialization and attachment */
static DEFINE_MUTEX(virtio_9p_lock);
/* global which tracks highest initialized channel */
static int chan_index;
/**
* struct virtio_chan - per-instance transport information
* @initialized: whether the channel is initialized
* @inuse: whether the channel is in use
* @lock: protects multiple elements within this structure
* @vdev: virtio dev associated with this channel
* @vq: virtio queue associated with this channel
* @tagpool: accounting for tag ids (and request slots)
* @reqs: array of request slots
* @max_tag: current number of request_slots allocated
* @sg: scatter gather list which is used to pack a request (protected?)
*
* We keep all per-channel information in a structure.
* This structure is allocated within the devices dev->mem space.
* A pointer to the structure will get put in the transport private.
*
*/
static struct virtio_chan {
bool initialized;
bool inuse;
spinlock_t lock;
struct p9_client *client;
struct virtio_device *vdev;
struct virtqueue *vq;
/* Scatterlist: can be too big for stack. */
struct scatterlist sg[VIRTQUEUE_NUM];
} channels[MAX_9P_CHAN];
/* How many bytes left in this page. */
static unsigned int rest_of_page(void *data)
{
return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
}
/**
* p9_virtio_close - reclaim resources of a channel
* @trans: transport state
*
* This reclaims a channel by freeing its resources and
* reseting its inuse flag.
*
*/
static void p9_virtio_close(struct p9_client *client)
{
struct virtio_chan *chan = client->trans;
mutex_lock(&virtio_9p_lock);
chan->inuse = false;
mutex_unlock(&virtio_9p_lock);
}
/**
* req_done - callback which signals activity from the server
* @vq: virtio queue activity was received on
*
* This notifies us that the server has triggered some activity
* on the virtio channel - most likely a response to request we
* sent. Figure out which requests now have responses and wake up
* those threads.
*
* Bugs: could do with some additional sanity checking, but appears to work.
*
*/
static void req_done(struct virtqueue *vq)
{
struct virtio_chan *chan = vq->vdev->priv;
struct p9_fcall *rc;
unsigned int len;
struct p9_req_t *req;
P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");
while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag);
req = p9_tag_lookup(chan->client, rc->tag);
req->status = REQ_STATUS_RCVD;
p9_client_cb(chan->client, req);
}
}
/**
* pack_sg_list - pack a scatter gather list from a linear buffer
* @sg: scatter/gather list to pack into
* @start: which segment of the sg_list to start at
* @limit: maximum segment to pack data to
* @data: data to pack into scatter/gather list
* @count: amount of data to pack into the scatter/gather list
*
* sg_lists have multiple segments of various sizes. This will pack
* arbitrary data into an existing scatter gather list, segmenting the
* data as necessary within constraints.
*
*/
static int
pack_sg_list(struct scatterlist *sg, int start, int limit, char *data,
int count)
{
int s;
int index = start;
while (count) {
s = rest_of_page(data);
if (s > count)
s = count;
sg_set_buf(&sg[index++], data, s);
count -= s;
data += s;
BUG_ON(index > limit);
}
return index-start;
}
/* We don't currently allow canceling of virtio requests */
static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
{
return 1;
}
/**
* p9_virtio_request - issue a request
* @t: transport state
* @tc: &p9_fcall request to transmit
* @rc: &p9_fcall to put reponse into
*
*/
static int
p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
{
int in, out;
struct virtio_chan *chan = client->trans;
char *rdata = (char *)req->rc+sizeof(struct p9_fcall);
P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");
out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, req->tc->sdata,
req->tc->size);
in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata,
client->msize);
req->status = REQ_STATUS_SENT;
if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, req->tc)) {
P9_DPRINTK(P9_DEBUG_TRANS,
"9p debug: virtio rpc add_buf returned failure");
return -EIO;
}
chan->vq->vq_ops->kick(chan->vq);
P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request kicked\n");
return 0;
}
/**
* p9_virtio_probe - probe for existence of 9P virtio channels
* @vdev: virtio device to probe
*
* This probes for existing virtio channels. At present only
* a single channel is in use, so in the future more work may need
* to be done here.
*
*/
static int p9_virtio_probe(struct virtio_device *vdev)
{
int err;
struct virtio_chan *chan;
int index;
mutex_lock(&virtio_9p_lock);
index = chan_index++;
chan = &channels[index];
mutex_unlock(&virtio_9p_lock);
if (chan_index > MAX_9P_CHAN) {
printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
BUG();
err = -ENOMEM;
goto fail;
}
chan->vdev = vdev;
/* We expect one virtqueue, for requests. */
chan->vq = vdev->config->find_vq(vdev, 0, req_done);
if (IS_ERR(chan->vq)) {
err = PTR_ERR(chan->vq);
goto out_free_vq;
}
chan->vq->vdev->priv = chan;
spin_lock_init(&chan->lock);
sg_init_table(chan->sg, VIRTQUEUE_NUM);
chan->inuse = false;
chan->initialized = true;
return 0;
out_free_vq:
vdev->config->del_vq(chan->vq);
fail:
mutex_lock(&virtio_9p_lock);
chan_index--;
mutex_unlock(&virtio_9p_lock);
return err;
}
/**
* p9_virtio_create - allocate a new virtio channel
* @client: client instance invoking this transport
* @devname: string identifying the channel to connect to (unused)
* @args: args passed from sys_mount() for per-transport options (unused)
*
* This sets up a transport channel for 9p communication. Right now
* we only match the first available channel, but eventually we couldlook up
* alternate channels by matching devname versus a virtio_config entry.
* We use a simple reference count mechanism to ensure that only a single
* mount has a channel open at a time.
*
* Bugs: doesn't allow identification of a specific channel
* to allocate, channels are allocated sequentially. This was
* a pragmatic decision to get things rolling, but ideally some
* way of identifying the channel to attach to would be nice
* if we are going to support multiple channels.
*
*/
static int
p9_virtio_create(struct p9_client *client, const char *devname, char *args)
{
struct virtio_chan *chan = channels;
int index = 0;
mutex_lock(&virtio_9p_lock);
while (index < MAX_9P_CHAN) {
if (chan->initialized && !chan->inuse) {
chan->inuse = true;
break;
} else {
index++;
chan = &channels[index];
}
}
mutex_unlock(&virtio_9p_lock);
if (index >= MAX_9P_CHAN) {
printk(KERN_ERR "9p: no channels available\n");
return -ENODEV;
}
client->trans = (void *)chan;
chan->client = client;
return 0;
}
/**
* p9_virtio_remove - clean up resources associated with a virtio device
* @vdev: virtio device to remove
*
*/
static void p9_virtio_remove(struct virtio_device *vdev)
{
struct virtio_chan *chan = vdev->priv;
BUG_ON(chan->inuse);
if (chan->initialized) {
vdev->config->del_vq(chan->vq);
chan->initialized = false;
}
}
#define VIRTIO_ID_9P 9
static struct virtio_device_id id_table[] = {
{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
{ 0 },
};
/* The standard "struct lguest_driver": */
static struct virtio_driver p9_virtio_drv = {
.driver.name = KBUILD_MODNAME,
.driver.owner = THIS_MODULE,
.id_table = id_table,
.probe = p9_virtio_probe,
.remove = p9_virtio_remove,
};
static struct p9_trans_module p9_virtio_trans = {
.name = "virtio",
.create = p9_virtio_create,
.close = p9_virtio_close,
.request = p9_virtio_request,
.cancel = p9_virtio_cancel,
.maxsize = PAGE_SIZE*16,
.def = 0,
.owner = THIS_MODULE,
};
/* The standard init function */
static int __init p9_virtio_init(void)
{
int count;
for (count = 0; count < MAX_9P_CHAN; count++)
channels[count].initialized = false;
v9fs_register_trans(&p9_virtio_trans);
return register_virtio_driver(&p9_virtio_drv);
}
static void __exit p9_virtio_cleanup(void)
{
unregister_virtio_driver(&p9_virtio_drv);
v9fs_unregister_trans(&p9_virtio_trans);
}
module_init(p9_virtio_init);
module_exit(p9_virtio_cleanup);
MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
MODULE_DESCRIPTION("Virtio 9p Transport");
MODULE_LICENSE("GPL");
