// SPDX-License-Identifier: GPL-2.0-only
/*
* 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
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#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/file.h>
#include <linux/highmem.h>
#include <linux/slab.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/swap.h>
#include <linux/virtio.h>
#include <linux/virtio_9p.h>
#include "trans_common.h"
#define VIRTQUEUE_NUM 128
/* a single mutex to manage channel initialization and attachment */
static DEFINE_MUTEX(virtio_9p_lock);
static DECLARE_WAIT_QUEUE_HEAD(vp_wq);
static atomic_t vp_pinned = ATOMIC_INIT(0);
/**
* struct virtio_chan - per-instance transport information
* @inuse: whether the channel is in use
* @lock: protects multiple elements within this structure
* @client: client instance
* @vdev: virtio dev associated with this channel
* @vq: virtio queue associated with this channel
* @ring_bufs_avail: flag to indicate there is some available in the ring buf
* @vc_wq: wait queue for waiting for thing to be added to ring buf
* @p9_max_pages: maximum number of pinned pages
* @sg: scatter gather list which is used to pack a request (protected?)
* @chan_list: linked list of channels
*
* 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.
*
*/
struct virtio_chan {
bool inuse;
spinlock_t lock;
struct p9_client *client;
struct virtio_device *vdev;
struct virtqueue *vq;
int ring_bufs_avail;
wait_queue_head_t *vc_wq;
/* This is global limit. Since we don't have a global structure,
* will be placing it in each channel.
*/
unsigned long p9_max_pages;
/* Scatterlist: can be too big for stack. */
struct scatterlist sg[VIRTQUEUE_NUM];
/**
* @tag: name to identify a mount null terminated
*/
char *tag;
struct list_head chan_list;
};
static struct list_head virtio_chan_list;
/* How many bytes left in this page. */
static unsigned int rest_of_page(void *data)
{
return PAGE_SIZE - offset_in_page(data);
}
/**
* p9_virtio_close - reclaim resources of a channel
* @client: client instance
*
* This reclaims a channel by freeing its resources and
* resetting its inuse flag.
*
*/
static void p9_virtio_close(struct p9_client *client)
{
struct virtio_chan *chan = client->trans;
mutex_lock(&virtio_9p_lock);
if (chan)
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;
unsigned int len;
struct p9_req_t *req;
bool need_wakeup = false;
unsigned long flags;
p9_debug(P9_DEBUG_TRANS, ": request done\n");
spin_lock_irqsave(&chan->lock, flags);
while ((req = virtqueue_get_buf(chan->vq, &len)) != NULL) {
if (!chan->ring_bufs_avail) {
chan->ring_bufs_avail = 1;
need_wakeup = true;
}
if (len) {
req->rc.size = len;
p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
}
}
spin_unlock_irqrestore(&chan->lock, flags);
/* Wakeup if anyone waiting for VirtIO ring space. */
if (need_wakeup)
wake_up(chan->vc_wq);
}
/**
* 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;
BUG_ON(index >= limit);
/* Make sure we don't terminate early. */
sg_unmark_end(&sg[index]);
sg_set_buf(&sg[index++], data, s);
count -= s;
data += s;
}
if (index-start)
sg_mark_end(&sg[index - 1]);
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;
}
/* Reply won't come, so drop req ref */
static int p9_virtio_cancelled(struct p9_client *client, struct p9_req_t *req)
{
p9_req_put(client, req);
return 0;
}
/**
* pack_sg_list_p - Just like pack_sg_list. Instead of taking a buffer,
* this takes a list of pages.
* @sg: scatter/gather list to pack into
* @start: which segment of the sg_list to start at
* @limit: maximum number of pages in sg list.
* @pdata: a list of pages to add into sg.
* @nr_pages: number of pages to pack into the scatter/gather list
* @offs: amount of data in the beginning of first page _not_ to pack
* @count: amount of data to pack into the scatter/gather list
*/
static int
pack_sg_list_p(struct scatterlist *sg, int start, int limit,
struct page **pdata, int nr_pages, size_t offs, int count)
{
int i = 0, s;
int data_off = offs;
int index = start;
BUG_ON(nr_pages > (limit - start));
/*
* if the first page doesn't start at
* page boundary find the offset
*/
while (nr_pages) {
s = PAGE_SIZE - data_off;
if (s > count)
s = count;
BUG_ON(index >= limit);
/* Make sure we don't terminate early. */
sg_unmark_end(&sg[index]);
sg_set_page(&sg[index++], pdata[i++], s, data_off);
data_off = 0;
count -= s;
nr_pages--;
}
if (index-start)
sg_mark_end(&sg[index - 1]);
return index - start;
}
/**
* p9_virtio_request - issue a request
* @client: client instance issuing the request
* @req: request to be issued
*
*/
static int
p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
{
int err;
int in, out, out_sgs, in_sgs;
unsigned long flags;
struct virtio_chan *chan = client->trans;
struct scatterlist *sgs[2];
p9_debug(P9_DEBUG_TRANS, "9p debug: virtio request\n");
WRITE_ONCE(req->status, REQ_STATUS_SENT);
req_retry:
spin_lock_irqsave(&chan->lock, flags);
out_sgs = in_sgs = 0;
/* Handle out VirtIO ring buffers */
out = pack_sg_list(chan->sg, 0,
VIRTQUEUE_NUM, req->tc.sdata, req->tc.size);
if (out)
sgs[out_sgs++] = chan->sg;
in = pack_sg_list(chan->sg, out,
VIRTQUEUE_NUM, req->rc.sdata, req->rc.capacity);
if (in)
sgs[out_sgs + in_sgs++] = chan->sg + out;
err = virtqueue_add_sgs(chan->vq, sgs, out_sgs, in_sgs, req,
GFP_ATOMIC);
if (err < 0) {
if (err == -ENOSPC) {
chan->ring_bufs_avail = 0;
spin_unlock_irqrestore(&chan->lock, flags);
err = wait_event_killable(*chan->vc_wq,
chan->ring_bufs_avail);
if (err == -ERESTARTSYS)
return err;
p9_debug(P9_DEBUG_TRANS, "Retry virtio request\n");
goto req_retry;
} else {
spin_unlock_irqrestore(&chan->lock, flags);
p9_debug(P9_DEBUG_TRANS,
"virtio rpc add_sgs returned failure\n");
return -EIO;
}
}
virtqueue_kick(chan->vq);
spin_unlock_irqrestore(&chan->lock, flags);
p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
return 0;
}
static int p9_get_mapped_pages(struct virtio_chan *chan,
struct page ***pages,
struct iov_iter *data,
int count,
size_t *offs,
int *need_drop)
{
int nr_pages;
int err;
if (!iov_iter_count(data))
return 0;
if (!iov_iter_is_kvec(data)) {
int n;
/*
* We allow only p9_max_pages pinned. We wait for the
* Other zc request to finish here
*/
if (atomic_read(&vp_pinned) >= chan->p9_max_pages) {
err = wait_event_killable(vp_wq,
(atomic_read(&vp_pinned) < chan->p9_max_pages));
if (err == -ERESTARTSYS)
return err;
}
n = iov_iter_get_pages_alloc2(data, pages, count, offs);
if (n < 0)
return n;
*need_drop = 1;
nr_pages = DIV_ROUND_UP(n + *offs, PAGE_SIZE);
atomic_add(nr_pages, &vp_pinned);
return n;
} else {
/* kernel buffer, no need to pin pages */
int index;
size_t len;
void *p;
/* we'd already checked that it's non-empty */
while (1) {
len = iov_iter_single_seg_count(data);
if (likely(len)) {
p = data->kvec->iov_base + data->iov_offset;
break;
}
iov_iter_advance(data, 0);
}
if (len > count)
len = count;
nr_pages = DIV_ROUND_UP((unsigned long)p + len, PAGE_SIZE) -
(unsigned long)p / PAGE_SIZE;
*pages = kmalloc_array(nr_pages, sizeof(struct page *),
GFP_NOFS);
if (!*pages)
return -ENOMEM;
*need_drop = 0;
p -= (*offs = offset_in_page(p));
for (index = 0; index < nr_pages; index++) {
if (is_vmalloc_addr(p))
(*pages)[index] = vmalloc_to_page(p);
else
(*pages)[index] = kmap_to_page(p);
p += PAGE_SIZE;
}
iov_iter_advance(data, len);
return len;
}
}
static void handle_rerror(struct p9_req_t *req, int in_hdr_len,
size_t offs, struct page **pages)
{
unsigned size, n;
void *to = req->rc.sdata + in_hdr_len;
// Fits entirely into the static data? Nothing to do.
if (req->rc.size < in_hdr_len || !pages)
return;
// Really long error message? Tough, truncate the reply. Might get
// rejected (we can't be arsed to adjust the size encoded in header,
// or string size for that matter), but it wouldn't be anything valid
// anyway.
if (unlikely(req->rc.size > P9_ZC_HDR_SZ))
req->rc.size = P9_ZC_HDR_SZ;
// data won't span more than two pages
size = req->rc.size - in_hdr_len;
n = PAGE_SIZE - offs;
if (size > n) {
memcpy_from_page(to, *pages++, offs, n);
offs = 0;
to += n;
size -= n;
}
memcpy_from_page(to, *pages, offs, size);
}
/**
* p9_virtio_zc_request - issue a zero copy request
* @client: client instance issuing the request
* @req: request to be issued
* @uidata: user buffer that should be used for zero copy read
* @uodata: user buffer that should be used for zero copy write
* @inlen: read buffer size
* @outlen: write buffer size
* @in_hdr_len: reader header size, This is the size of response protocol data
*
*/
static int
p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
struct iov_iter *uidata, struct iov_iter *uodata,
int inlen, int outlen, int in_hdr_len)
{
int in, out, err, out_sgs, in_sgs;
unsigned long flags;
int in_nr_pages = 0, out_nr_pages = 0;
struct page **in_pages = NULL, **out_pages = NULL;
struct virtio_chan *chan = client->trans;
struct scatterlist *sgs[4];
size_t offs = 0;
int need_drop = 0;
int kicked = 0;
p9_debug(P9_DEBUG_TRANS, "virtio request\n");
if (uodata) {
__le32 sz;
int n = p9_get_mapped_pages(chan, &out_pages, uodata,
outlen, &offs, &need_drop);
if (n < 0) {
err = n;
goto err_out;
}
out_nr_pages = DIV_ROUND_UP(n + offs, PAGE_SIZE);
if (n != outlen) {
__le32 v = cpu_to_le32(n);
memcpy(&req->tc.sdata[req->tc.size - 4], &v, 4);
outlen = n;
}
/* The size field of the message must include the length of the
* header and the length of the data. We didn't actually know
* the length of the data until this point so add it in now.
*/
sz = cpu_to_le32(req->tc.size + outlen);
memcpy(&req->tc.sdata[0], &sz, sizeof(sz));
} else if (uidata) {
int n = p9_get_mapped_pages(chan, &in_pages, uidata,
inlen, &offs, &need_drop);
if (n < 0) {
err = n;
goto err_out;
}
in_nr_pages = DIV_ROUND_UP(n + offs, PAGE_SIZE);
if (n != inlen) {
__le32 v = cpu_to_le32(n);
memcpy(&req->tc.sdata[req->tc.size - 4], &v, 4);
inlen = n;
}
}
WRITE_ONCE(req->status, REQ_STATUS_SENT);
req_retry_pinned:
spin_lock_irqsave(&chan->lock, flags);
out_sgs = in_sgs = 0;
/* out data */
out = pack_sg_list(chan->sg, 0,
VIRTQUEUE_NUM, req->tc.sdata, req->tc.size);
if (out)
sgs[out_sgs++] = chan->sg;
if (out_pages) {
sgs[out_sgs++] = chan->sg + out;
out += pack_sg_list_p(chan->sg, out, VIRTQUEUE_NUM,
out_pages, out_nr_pages, offs, outlen);
}
/*
* Take care of in data
* For example TREAD have 11.
* 11 is the read/write header = PDU Header(7) + IO Size (4).
* Arrange in such a way that server places header in the
* allocated memory and payload onto the user buffer.
*/
in = pack_sg_list(chan->sg, out,
VIRTQUEUE_NUM, req->rc.sdata, in_hdr_len);
if (in)
sgs[out_sgs + in_sgs++] = chan->sg + out;
if (in_pages) {
sgs[out_sgs + in_sgs++] = chan->sg + out + in;
pack_sg_list_p(chan->sg, out + in, VIRTQUEUE_NUM,
in_pages, in_nr_pages, offs, inlen);
}
BUG_ON(out_sgs + in_sgs > ARRAY_SIZE(sgs));
err = virtqueue_add_sgs(chan->vq, sgs, out_sgs, in_sgs, req,
GFP_ATOMIC);
if (err < 0) {
if (err == -ENOSPC) {
chan->ring_bufs_avail = 0;
spin_unlock_irqrestore(&chan->lock, flags);
err = wait_event_killable(*chan->vc_wq,
chan->ring_bufs_avail);
if (err == -ERESTARTSYS)
goto err_out;
p9_debug(P9_DEBUG_TRANS, "Retry virtio request\n");
goto req_retry_pinned;
} else {
spin_unlock_irqrestore(&chan->lock, flags);
p9_debug(P9_DEBUG_TRANS,
"virtio rpc add_sgs returned failure\n");
err = -EIO;
goto err_out;
}
}
virtqueue_kick(chan->vq);
spin_unlock_irqrestore(&chan->lock, flags);
kicked = 1;
p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
err = wait_event_killable(req->wq,
READ_ONCE(req->status) >= REQ_STATUS_RCVD);
// RERROR needs reply (== error string) in static data
if (READ_ONCE(req->status) == REQ_STATUS_RCVD &&
unlikely(req->rc.sdata[4] == P9_RERROR))
handle_rerror(req, in_hdr_len, offs, in_pages);
/*
* Non kernel buffers are pinned, unpin them
*/
err_out:
if (need_drop) {
if (in_pages) {
p9_release_pages(in_pages, in_nr_pages);
atomic_sub(in_nr_pages, &vp_pinned);
}
if (out_pages) {
p9_release_pages(out_pages, out_nr_pages);
atomic_sub(out_nr_pages, &vp_pinned);
}
/* wakeup anybody waiting for slots to pin pages */
wake_up(&vp_wq);
}
kvfree(in_pages);
kvfree(out_pages);
if (!kicked) {
/* reply won't come */
p9_req_put(client, req);
}
return err;
}
static ssize_t p9_mount_tag_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct virtio_chan *chan;
struct virtio_device *vdev;
int tag_len;
vdev = dev_to_virtio(dev);
chan = vdev->priv;
tag_len = strlen(chan->tag);
memcpy(buf, chan->tag, tag_len + 1);
return tag_len + 1;
}
static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);
/**
* p9_virtio_probe - probe for existence of 9P virtio channels
* @vdev: virtio device to probe
*
* This probes for existing virtio channels.
*
*/
static int p9_virtio_probe(struct virtio_device *vdev)
{
__u16 tag_len;
char *tag;
int err;
struct virtio_chan *chan;
if (!vdev->config->get) {
dev_err(&vdev->dev, "%s failure: config access disabled\n",
__func__);
return -EINVAL;
}
chan = kmalloc(sizeof(struct virtio_chan), GFP_KERNEL);
if (!chan) {
pr_err("Failed to allocate virtio 9P channel\n");
err = -ENOMEM;
goto fail;
}
chan->vdev = vdev;
/* We expect one virtqueue, for requests. */
chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
if (IS_ERR(chan->vq)) {
err = PTR_ERR(chan->vq);
goto out_free_chan;
}
chan->vq->vdev->priv = chan;
spin_lock_init(&chan->lock);
sg_init_table(chan->sg, VIRTQUEUE_NUM);
chan->inuse = false;
if (virtio_has_feature(vdev, VIRTIO_9P_MOUNT_TAG)) {
virtio_cread(vdev, struct virtio_9p_config, tag_len, &tag_len);
} else {
err = -EINVAL;
goto out_free_vq;
}
tag = kzalloc(tag_len + 1, GFP_KERNEL);
if (!tag) {
err = -ENOMEM;
goto out_free_vq;
}
virtio_cread_bytes(vdev, offsetof(struct virtio_9p_config, tag),
tag, tag_len);
chan->tag = tag;
err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
if (err) {
goto out_free_tag;
}
chan->vc_wq = kmalloc(sizeof(wait_queue_head_t), GFP_KERNEL);
if (!chan->vc_wq) {
err = -ENOMEM;
goto out_remove_file;
}
init_waitqueue_head(chan->vc_wq);
chan->ring_bufs_avail = 1;
/* Ceiling limit to avoid denial of service attacks */
chan->p9_max_pages = nr_free_buffer_pages()/4;
virtio_device_ready(vdev);
mutex_lock(&virtio_9p_lock);
list_add_tail(&chan->chan_list, &virtio_chan_list);
mutex_unlock(&virtio_9p_lock);
/* Let udev rules use the new mount_tag attribute. */
kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE);
return 0;
out_remove_file:
sysfs_remove_file(&vdev->dev.kobj, &dev_attr_mount_tag.attr);
out_free_tag:
kfree(tag);
out_free_vq:
vdev->config->del_vqs(vdev);
out_free_chan:
kfree(chan);
fail:
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 could look 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.
*
*/
static int
p9_virtio_create(struct p9_client *client, const char *devname, char *args)
{
struct virtio_chan *chan;
int ret = -ENOENT;
int found = 0;
if (devname == NULL)
return -EINVAL;
mutex_lock(&virtio_9p_lock);
list_for_each_entry(chan, &virtio_chan_list, chan_list) {
if (!strcmp(devname, chan->tag)) {
if (!chan->inuse) {
chan->inuse = true;
found = 1;
break;
}
ret = -EBUSY;
}
}
mutex_unlock(&virtio_9p_lock);
if (!found) {
pr_err("no channels available for device %s\n", devname);
return ret;
}
client->trans = (void *)chan;
client->status = Connected;
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;
unsigned long warning_time;
mutex_lock(&virtio_9p_lock);
/* Remove self from list so we don't get new users. */
list_del(&chan->chan_list);
warning_time = jiffies;
/* Wait for existing users to close. */
while (chan->inuse) {
mutex_unlock(&virtio_9p_lock);
msleep(250);
if (time_after(jiffies, warning_time + 10 * HZ)) {
dev_emerg(&vdev->dev,
"p9_virtio_remove: waiting for device in use.\n");
warning_time = jiffies;
}
mutex_lock(&virtio_9p_lock);
}
mutex_unlock(&virtio_9p_lock);
virtio_reset_device(vdev);
vdev->config->del_vqs(vdev);
sysfs_remove_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE);
kfree(chan->tag);
kfree(chan->vc_wq);
kfree(chan);
}
static struct virtio_device_id id_table[] = {
{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
{ 0 },
};
static unsigned int features[] = {
VIRTIO_9P_MOUNT_TAG,
};
/* The standard "struct lguest_driver": */
static struct virtio_driver p9_virtio_drv = {
.feature_table = features,
.feature_table_size = ARRAY_SIZE(features),
.driver.name = KBUILD_MODNAME,
.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,
.zc_request = p9_virtio_zc_request,
.cancel = p9_virtio_cancel,
.cancelled = p9_virtio_cancelled,
/*
* We leave one entry for input and one entry for response
* headers. We also skip one more entry to accommodate, address
* that are not at page boundary, that can result in an extra
* page in zero copy.
*/
.maxsize = PAGE_SIZE * (VIRTQUEUE_NUM - 3),
.pooled_rbuffers = false,
.def = 1,
.owner = THIS_MODULE,
};
/* The standard init function */
static int __init p9_virtio_init(void)
{
int rc;
INIT_LIST_HEAD(&virtio_chan_list);
v9fs_register_trans(&p9_virtio_trans);
rc = register_virtio_driver(&p9_virtio_drv);
if (rc)
v9fs_unregister_trans(&p9_virtio_trans);
return rc;
}
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_ALIAS_9P("virtio");
MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_AUTHOR("Eric Van Hensbergen <[email protected]>");
MODULE_DESCRIPTION("Virtio 9p Transport");
MODULE_LICENSE("GPL");
Codebase Browser
linux