// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/fs/9p/trans_xen
*
* Xen transport layer.
*
* Copyright (C) 2017 by Stefano Stabellini <[email protected]>
*/
#include <xen/events.h>
#include <xen/grant_table.h>
#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/interface/io/9pfs.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>
#include <net/9p/transport.h>
#define XEN_9PFS_NUM_RINGS 2
#define XEN_9PFS_RING_ORDER 9
#define XEN_9PFS_RING_SIZE(ring) XEN_FLEX_RING_SIZE(ring->intf->ring_order)
struct xen_9pfs_header {
uint32_t size;
uint8_t id;
uint16_t tag;
/* uint8_t sdata[]; */
} __attribute__((packed));
/* One per ring, more than one per 9pfs share */
struct xen_9pfs_dataring {
struct xen_9pfs_front_priv *priv;
struct xen_9pfs_data_intf *intf;
grant_ref_t ref;
int evtchn;
int irq;
/* protect a ring from concurrent accesses */
spinlock_t lock;
struct xen_9pfs_data data;
wait_queue_head_t wq;
struct work_struct work;
};
/* One per 9pfs share */
struct xen_9pfs_front_priv {
struct list_head list;
struct xenbus_device *dev;
char *tag;
struct p9_client *client;
struct xen_9pfs_dataring *rings;
};
static LIST_HEAD(xen_9pfs_devs);
static DEFINE_RWLOCK(xen_9pfs_lock);
/* We don't currently allow canceling of requests */
static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
{
return 1;
}
static int p9_xen_create(struct p9_client *client, const char *addr, char *args)
{
struct xen_9pfs_front_priv *priv;
if (addr == NULL)
return -EINVAL;
read_lock(&xen_9pfs_lock);
list_for_each_entry(priv, &xen_9pfs_devs, list) {
if (!strcmp(priv->tag, addr)) {
priv->client = client;
read_unlock(&xen_9pfs_lock);
return 0;
}
}
read_unlock(&xen_9pfs_lock);
return -EINVAL;
}
static void p9_xen_close(struct p9_client *client)
{
struct xen_9pfs_front_priv *priv;
read_lock(&xen_9pfs_lock);
list_for_each_entry(priv, &xen_9pfs_devs, list) {
if (priv->client == client) {
priv->client = NULL;
read_unlock(&xen_9pfs_lock);
return;
}
}
read_unlock(&xen_9pfs_lock);
}
static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
{
RING_IDX cons, prod;
cons = ring->intf->out_cons;
prod = ring->intf->out_prod;
virt_mb();
return XEN_9PFS_RING_SIZE(ring) -
xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) >= size;
}
static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
{
struct xen_9pfs_front_priv *priv;
RING_IDX cons, prod, masked_cons, masked_prod;
unsigned long flags;
u32 size = p9_req->tc.size;
struct xen_9pfs_dataring *ring;
int num;
read_lock(&xen_9pfs_lock);
list_for_each_entry(priv, &xen_9pfs_devs, list) {
if (priv->client == client)
break;
}
read_unlock(&xen_9pfs_lock);
if (list_entry_is_head(priv, &xen_9pfs_devs, list))
return -EINVAL;
num = p9_req->tc.tag % XEN_9PFS_NUM_RINGS;
ring = &priv->rings[num];
again:
while (wait_event_killable(ring->wq,
p9_xen_write_todo(ring, size)) != 0)
;
spin_lock_irqsave(&ring->lock, flags);
cons = ring->intf->out_cons;
prod = ring->intf->out_prod;
virt_mb();
if (XEN_9PFS_RING_SIZE(ring) -
xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) < size) {
spin_unlock_irqrestore(&ring->lock, flags);
goto again;
}
masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
xen_9pfs_write_packet(ring->data.out, p9_req->tc.sdata, size,
&masked_prod, masked_cons,
XEN_9PFS_RING_SIZE(ring));
WRITE_ONCE(p9_req->status, REQ_STATUS_SENT);
virt_wmb(); /* write ring before updating pointer */
prod += size;
ring->intf->out_prod = prod;
spin_unlock_irqrestore(&ring->lock, flags);
notify_remote_via_irq(ring->irq);
p9_req_put(client, p9_req);
return 0;
}
static void p9_xen_response(struct work_struct *work)
{
struct xen_9pfs_front_priv *priv;
struct xen_9pfs_dataring *ring;
RING_IDX cons, prod, masked_cons, masked_prod;
struct xen_9pfs_header h;
struct p9_req_t *req;
int status;
ring = container_of(work, struct xen_9pfs_dataring, work);
priv = ring->priv;
while (1) {
cons = ring->intf->in_cons;
prod = ring->intf->in_prod;
virt_rmb();
if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) <
sizeof(h)) {
notify_remote_via_irq(ring->irq);
return;
}
masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
/* First, read just the header */
xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
masked_prod, &masked_cons,
XEN_9PFS_RING_SIZE(ring));
req = p9_tag_lookup(priv->client, h.tag);
if (!req || req->status != REQ_STATUS_SENT) {
dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
cons += h.size;
virt_mb();
ring->intf->in_cons = cons;
continue;
}
if (h.size > req->rc.capacity) {
dev_warn(&priv->dev->dev,
"requested packet size too big: %d for tag %d with capacity %zd\n",
h.size, h.tag, req->rc.capacity);
WRITE_ONCE(req->status, REQ_STATUS_ERROR);
goto recv_error;
}
req->rc.size = h.size;
req->rc.id = h.id;
req->rc.tag = h.tag;
req->rc.offset = 0;
masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
/* Then, read the whole packet (including the header) */
xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
masked_prod, &masked_cons,
XEN_9PFS_RING_SIZE(ring));
recv_error:
virt_mb();
cons += h.size;
ring->intf->in_cons = cons;
status = (req->status != REQ_STATUS_ERROR) ?
REQ_STATUS_RCVD : REQ_STATUS_ERROR;
p9_client_cb(priv->client, req, status);
}
}
static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
{
struct xen_9pfs_dataring *ring = r;
if (!ring || !ring->priv->client) {
/* ignore spurious interrupt */
return IRQ_HANDLED;
}
wake_up_interruptible(&ring->wq);
schedule_work(&ring->work);
return IRQ_HANDLED;
}
static struct p9_trans_module p9_xen_trans = {
.name = "xen",
.maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
.pooled_rbuffers = false,
.def = 1,
.create = p9_xen_create,
.close = p9_xen_close,
.request = p9_xen_request,
.cancel = p9_xen_cancel,
.owner = THIS_MODULE,
};
static const struct xenbus_device_id xen_9pfs_front_ids[] = {
{ "9pfs" },
{ "" }
};
static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
{
int i, j;
write_lock(&xen_9pfs_lock);
list_del(&priv->list);
write_unlock(&xen_9pfs_lock);
for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
struct xen_9pfs_dataring *ring = &priv->rings[i];
cancel_work_sync(&ring->work);
if (!priv->rings[i].intf)
break;
if (priv->rings[i].irq > 0)
unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
if (priv->rings[i].data.in) {
for (j = 0;
j < (1 << priv->rings[i].intf->ring_order);
j++) {
grant_ref_t ref;
ref = priv->rings[i].intf->ref[j];
gnttab_end_foreign_access(ref, NULL);
}
free_pages_exact(priv->rings[i].data.in,
1UL << (priv->rings[i].intf->ring_order +
XEN_PAGE_SHIFT));
}
gnttab_end_foreign_access(priv->rings[i].ref, NULL);
free_page((unsigned long)priv->rings[i].intf);
}
kfree(priv->rings);
kfree(priv->tag);
kfree(priv);
}
static void xen_9pfs_front_remove(struct xenbus_device *dev)
{
struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
dev_set_drvdata(&dev->dev, NULL);
xen_9pfs_front_free(priv);
}
static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
struct xen_9pfs_dataring *ring,
unsigned int order)
{
int i = 0;
int ret = -ENOMEM;
void *bytes = NULL;
init_waitqueue_head(&ring->wq);
spin_lock_init(&ring->lock);
INIT_WORK(&ring->work, p9_xen_response);
ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
if (!ring->intf)
return ret;
ret = gnttab_grant_foreign_access(dev->otherend_id,
virt_to_gfn(ring->intf), 0);
if (ret < 0)
goto out;
ring->ref = ret;
bytes = alloc_pages_exact(1UL << (order + XEN_PAGE_SHIFT),
GFP_KERNEL | __GFP_ZERO);
if (!bytes) {
ret = -ENOMEM;
goto out;
}
for (; i < (1 << order); i++) {
ret = gnttab_grant_foreign_access(
dev->otherend_id, virt_to_gfn(bytes) + i, 0);
if (ret < 0)
goto out;
ring->intf->ref[i] = ret;
}
ring->intf->ring_order = order;
ring->data.in = bytes;
ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
if (ret)
goto out;
ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
xen_9pfs_front_event_handler,
0, "xen_9pfs-frontend", ring);
if (ring->irq >= 0)
return 0;
xenbus_free_evtchn(dev, ring->evtchn);
ret = ring->irq;
out:
if (bytes) {
for (i--; i >= 0; i--)
gnttab_end_foreign_access(ring->intf->ref[i], NULL);
free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT));
}
gnttab_end_foreign_access(ring->ref, NULL);
free_page((unsigned long)ring->intf);
return ret;
}
static int xen_9pfs_front_init(struct xenbus_device *dev)
{
int ret, i;
struct xenbus_transaction xbt;
struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
char *versions, *v;
unsigned int max_rings, max_ring_order, len = 0;
versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
if (IS_ERR(versions))
return PTR_ERR(versions);
for (v = versions; *v; v++) {
if (simple_strtoul(v, &v, 10) == 1) {
v = NULL;
break;
}
}
if (v) {
kfree(versions);
return -EINVAL;
}
kfree(versions);
max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
if (max_rings < XEN_9PFS_NUM_RINGS)
return -EINVAL;
max_ring_order = xenbus_read_unsigned(dev->otherend,
"max-ring-page-order", 0);
if (max_ring_order > XEN_9PFS_RING_ORDER)
max_ring_order = XEN_9PFS_RING_ORDER;
if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
priv->rings = kcalloc(XEN_9PFS_NUM_RINGS, sizeof(*priv->rings),
GFP_KERNEL);
if (!priv->rings) {
kfree(priv);
return -ENOMEM;
}
for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
priv->rings[i].priv = priv;
ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
max_ring_order);
if (ret < 0)
goto error;
}
again:
ret = xenbus_transaction_start(&xbt);
if (ret) {
xenbus_dev_fatal(dev, ret, "starting transaction");
goto error;
}
ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
if (ret)
goto error_xenbus;
ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
XEN_9PFS_NUM_RINGS);
if (ret)
goto error_xenbus;
for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
char str[16];
BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
sprintf(str, "ring-ref%d", i);
ret = xenbus_printf(xbt, dev->nodename, str, "%d",
priv->rings[i].ref);
if (ret)
goto error_xenbus;
sprintf(str, "event-channel-%d", i);
ret = xenbus_printf(xbt, dev->nodename, str, "%u",
priv->rings[i].evtchn);
if (ret)
goto error_xenbus;
}
priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
if (IS_ERR(priv->tag)) {
ret = PTR_ERR(priv->tag);
goto error_xenbus;
}
ret = xenbus_transaction_end(xbt, 0);
if (ret) {
if (ret == -EAGAIN)
goto again;
xenbus_dev_fatal(dev, ret, "completing transaction");
goto error;
}
return 0;
error_xenbus:
xenbus_transaction_end(xbt, 1);
xenbus_dev_fatal(dev, ret, "writing xenstore");
error:
xen_9pfs_front_free(priv);
return ret;
}
static int xen_9pfs_front_probe(struct xenbus_device *dev,
const struct xenbus_device_id *id)
{
struct xen_9pfs_front_priv *priv = NULL;
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
priv->dev = dev;
dev_set_drvdata(&dev->dev, priv);
write_lock(&xen_9pfs_lock);
list_add_tail(&priv->list, &xen_9pfs_devs);
write_unlock(&xen_9pfs_lock);
return 0;
}
static int xen_9pfs_front_resume(struct xenbus_device *dev)
{
dev_warn(&dev->dev, "suspend/resume unsupported\n");
return 0;
}
static void xen_9pfs_front_changed(struct xenbus_device *dev,
enum xenbus_state backend_state)
{
switch (backend_state) {
case XenbusStateReconfiguring:
case XenbusStateReconfigured:
case XenbusStateInitialising:
case XenbusStateInitialised:
case XenbusStateUnknown:
break;
case XenbusStateInitWait:
if (!xen_9pfs_front_init(dev))
xenbus_switch_state(dev, XenbusStateInitialised);
break;
case XenbusStateConnected:
xenbus_switch_state(dev, XenbusStateConnected);
break;
case XenbusStateClosed:
if (dev->state == XenbusStateClosed)
break;
fallthrough; /* Missed the backend's CLOSING state */
case XenbusStateClosing:
xenbus_frontend_closed(dev);
break;
}
}
static struct xenbus_driver xen_9pfs_front_driver = {
.ids = xen_9pfs_front_ids,
.probe = xen_9pfs_front_probe,
.remove = xen_9pfs_front_remove,
.resume = xen_9pfs_front_resume,
.otherend_changed = xen_9pfs_front_changed,
};
static int __init p9_trans_xen_init(void)
{
int rc;
if (!xen_domain())
return -ENODEV;
pr_info("Initialising Xen transport for 9pfs\n");
v9fs_register_trans(&p9_xen_trans);
rc = xenbus_register_frontend(&xen_9pfs_front_driver);
if (rc)
v9fs_unregister_trans(&p9_xen_trans);
return rc;
}
module_init(p9_trans_xen_init);
MODULE_ALIAS_9P("xen");
static void __exit p9_trans_xen_exit(void)
{
v9fs_unregister_trans(&p9_xen_trans);
return xenbus_unregister_driver(&xen_9pfs_front_driver);
}
module_exit(p9_trans_xen_exit);
MODULE_ALIAS("xen:9pfs");
MODULE_AUTHOR("Stefano Stabellini <[email protected]>");
MODULE_DESCRIPTION("Xen Transport for 9P");
MODULE_LICENSE("GPL");