![Eric Van Hensbergen](/assets/img/avatar_default.png)
This adds a transport to 9p for communicating between guests and a host using a virtio based transport. Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
354 lines
9.1 KiB
C
354 lines
9.1 KiB
C
/*
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* The Guest 9p transport driver
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*
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* This is a trivial pipe-based transport driver based on the lguest console
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* code: we use lguest's DMA mechanism to send bytes out, and register a
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* DMA buffer to receive bytes in. It is assumed to be present and available
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* from the very beginning of boot.
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*
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* This may be have been done by just instaniating another HVC console,
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* but HVC's blocksize of 16 bytes is annoying and painful to performance.
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*
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* A more efficient transport could be built based on the virtio block driver
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* but it requires some changes in the 9p transport model (which are in
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* progress)
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*
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*/
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/*
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* Copyright (C) 2007 Eric Van Hensbergen, IBM Corporation
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*
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* Based on virtio console driver
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* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to:
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* Free Software Foundation
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* 51 Franklin Street, Fifth Floor
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* Boston, MA 02111-1301 USA
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*
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*/
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#include <linux/in.h>
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#include <linux/module.h>
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#include <linux/net.h>
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#include <linux/ipv6.h>
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/un.h>
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#include <linux/uaccess.h>
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#include <linux/inet.h>
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#include <linux/idr.h>
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#include <linux/file.h>
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#include <net/9p/9p.h>
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#include <linux/parser.h>
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#include <net/9p/transport.h>
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#include <linux/scatterlist.h>
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#include <linux/virtio.h>
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#include <linux/virtio_9p.h>
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/* a single mutex to manage channel initialization and attachment */
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static DECLARE_MUTEX(virtio_9p_lock);
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/* global which tracks highest initialized channel */
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static int chan_index;
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/* We keep all per-channel information in a structure.
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* This structure is allocated within the devices dev->mem space.
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* A pointer to the structure will get put in the transport private.
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*/
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static struct virtio_chan {
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bool initialized; /* channel is initialized */
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bool inuse; /* channel is in use */
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struct virtqueue *in_vq, *out_vq;
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struct virtio_device *vdev;
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/* This is our input buffer, and how much data is left in it. */
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unsigned int in_len;
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char *in, *inbuf;
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wait_queue_head_t wq; /* waitq for buffer */
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} channels[MAX_9P_CHAN];
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/* How many bytes left in this page. */
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static unsigned int rest_of_page(void *data)
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{
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return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
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}
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static int p9_virtio_write(struct p9_trans *trans, void *buf, int count)
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{
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struct virtio_chan *chan = (struct virtio_chan *) trans->priv;
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struct virtqueue *out_vq = chan->out_vq;
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struct scatterlist sg[1];
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unsigned int len;
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P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio write (%d)\n", count);
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/* keep it simple - make sure we don't overflow a page */
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if (rest_of_page(buf) < count)
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count = rest_of_page(buf);
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sg_init_one(sg, buf, count);
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/* add_buf wants a token to identify this buffer: we hand it any
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* non-NULL pointer, since there's only ever one buffer. */
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if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) == 0) {
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/* Tell Host to go! */
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out_vq->vq_ops->kick(out_vq);
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/* Chill out until it's done with the buffer. */
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while (!out_vq->vq_ops->get_buf(out_vq, &len))
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cpu_relax();
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}
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P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio wrote (%d)\n", count);
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/* We're expected to return the amount of data we wrote: all of it. */
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return count;
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}
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/* Create a scatter-gather list representing our input buffer and put it in the
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* queue. */
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static void add_inbuf(struct virtio_chan *chan)
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{
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struct scatterlist sg[1];
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sg_init_one(sg, chan->inbuf, PAGE_SIZE);
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/* We should always be able to add one buffer to an empty queue. */
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if (chan->in_vq->vq_ops->add_buf(chan->in_vq, sg, 0, 1, chan->inbuf))
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BUG();
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chan->in_vq->vq_ops->kick(chan->in_vq);
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}
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static int p9_virtio_read(struct p9_trans *trans, void *buf, int count)
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{
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struct virtio_chan *chan = (struct virtio_chan *) trans->priv;
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struct virtqueue *in_vq = chan->in_vq;
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P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio read (%d)\n", count);
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/* If we don't have an input queue yet, we can't get input. */
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BUG_ON(!in_vq);
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/* No buffer? Try to get one. */
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if (!chan->in_len) {
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chan->in = in_vq->vq_ops->get_buf(in_vq, &chan->in_len);
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if (!chan->in)
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return 0;
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}
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/* You want more than we have to give? Well, try wanting less! */
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if (chan->in_len < count)
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count = chan->in_len;
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/* Copy across to their buffer and increment offset. */
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memcpy(buf, chan->in, count);
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chan->in += count;
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chan->in_len -= count;
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/* Finished? Re-register buffer so Host will use it again. */
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if (chan->in_len == 0)
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add_inbuf(chan);
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P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio finished read (%d)\n",
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count);
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return count;
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}
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/* The poll function is used by 9p transports to determine if there
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* is there is activity available on a particular channel. In our case
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* we use it to wait for a callback from the input routines.
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*/
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static unsigned int
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p9_virtio_poll(struct p9_trans *trans, struct poll_table_struct *pt)
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{
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struct virtio_chan *chan = (struct virtio_chan *)trans->priv;
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struct virtqueue *in_vq = chan->in_vq;
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int ret = POLLOUT; /* we can always handle more output */
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poll_wait(NULL, &chan->wq, pt);
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/* No buffer? Try to get one. */
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if (!chan->in_len)
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chan->in = in_vq->vq_ops->get_buf(in_vq, &chan->in_len);
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if (chan->in_len)
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ret |= POLLIN;
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return ret;
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}
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static void p9_virtio_close(struct p9_trans *trans)
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{
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struct virtio_chan *chan = trans->priv;
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down(&virtio_9p_lock);
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chan->inuse = false;
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up(&virtio_9p_lock);
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kfree(trans);
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}
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static bool p9_virtio_intr(struct virtqueue *q)
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{
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struct virtio_chan *chan = q->vdev->priv;
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P9_DPRINTK(P9_DEBUG_TRANS, "9p poll_wakeup: %p\n", &chan->wq);
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wake_up_interruptible(&chan->wq);
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return true;
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}
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static int p9_virtio_probe(struct virtio_device *dev)
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{
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int err;
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struct virtio_chan *chan;
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int index;
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down(&virtio_9p_lock);
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index = chan_index++;
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chan = &channels[index];
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up(&virtio_9p_lock);
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if (chan_index > MAX_9P_CHAN) {
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printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
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BUG();
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}
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chan->vdev = dev;
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/* This is the scratch page we use to receive console input */
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chan->inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
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if (!chan->inbuf) {
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err = -ENOMEM;
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goto fail;
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}
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/* Find the input queue. */
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dev->priv = chan;
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chan->in_vq = dev->config->find_vq(dev, p9_virtio_intr);
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if (IS_ERR(chan->in_vq)) {
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err = PTR_ERR(chan->in_vq);
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goto free;
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}
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chan->out_vq = dev->config->find_vq(dev, NULL);
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if (IS_ERR(chan->out_vq)) {
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err = PTR_ERR(chan->out_vq);
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goto free_in_vq;
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}
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init_waitqueue_head(&chan->wq);
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/* Register the input buffer the first time. */
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add_inbuf(chan);
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chan->inuse = false;
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chan->initialized = true;
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return 0;
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free_in_vq:
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dev->config->del_vq(chan->in_vq);
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free:
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kfree(chan->inbuf);
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fail:
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down(&virtio_9p_lock);
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chan_index--;
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up(&virtio_9p_lock);
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return err;
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}
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/* This sets up a transport channel for 9p communication. Right now
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* we only match the first available channel, but eventually we couldlook up
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* alternate channels by matching devname versus a virtio_config entry.
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* We use a simple reference count mechanism to ensure that only a single
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* mount has a channel open at a time. */
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static struct p9_trans *p9_virtio_create(const char *devname, char *args)
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{
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struct p9_trans *trans;
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int index = 0;
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struct virtio_chan *chan = channels;
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down(&virtio_9p_lock);
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while (index < MAX_9P_CHAN) {
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if (chan->initialized && !chan->inuse) {
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chan->inuse = true;
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break;
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} else {
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index++;
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chan = &channels[index];
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}
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}
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up(&virtio_9p_lock);
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if (index >= MAX_9P_CHAN) {
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printk(KERN_ERR "9p: virtio: couldn't find a free channel\n");
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return NULL;
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}
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trans = kmalloc(sizeof(struct p9_trans), GFP_KERNEL);
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if (!trans) {
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printk(KERN_ERR "9p: couldn't allocate transport\n");
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return ERR_PTR(-ENOMEM);
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}
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trans->write = p9_virtio_write;
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trans->read = p9_virtio_read;
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trans->close = p9_virtio_close;
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trans->poll = p9_virtio_poll;
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trans->priv = chan;
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return trans;
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}
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#define VIRTIO_ID_9P 9
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static struct virtio_device_id id_table[] = {
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{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
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{ 0 },
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};
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/* The standard "struct lguest_driver": */
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static struct virtio_driver p9_virtio_drv = {
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.driver.name = KBUILD_MODNAME,
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.driver.owner = THIS_MODULE,
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.id_table = id_table,
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.probe = p9_virtio_probe,
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};
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static struct p9_trans_module p9_virtio_trans = {
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.name = "virtio",
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.create = p9_virtio_create,
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.maxsize = PAGE_SIZE,
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.def = 0,
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};
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/* The standard init function */
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static int __init p9_virtio_init(void)
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{
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int count;
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for (count = 0; count < MAX_9P_CHAN; count++)
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channels[count].initialized = false;
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v9fs_register_trans(&p9_virtio_trans);
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return register_virtio_driver(&p9_virtio_drv);
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}
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module_init(p9_virtio_init);
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MODULE_DEVICE_TABLE(virtio, id_table);
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MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
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MODULE_DESCRIPTION("Virtio 9p Transport");
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MODULE_LICENSE("GPL");
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