cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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pvcalls-front.c (32726B)


      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 * (c) 2017 Stefano Stabellini <stefano@aporeto.com>
      4 */
      5
      6#include <linux/module.h>
      7#include <linux/net.h>
      8#include <linux/socket.h>
      9
     10#include <net/sock.h>
     11
     12#include <xen/events.h>
     13#include <xen/grant_table.h>
     14#include <xen/xen.h>
     15#include <xen/xenbus.h>
     16#include <xen/interface/io/pvcalls.h>
     17
     18#include "pvcalls-front.h"
     19
     20#define PVCALLS_INVALID_ID UINT_MAX
     21#define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
     22#define PVCALLS_NR_RSP_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE)
     23#define PVCALLS_FRONT_MAX_SPIN 5000
     24
     25static struct proto pvcalls_proto = {
     26	.name	= "PVCalls",
     27	.owner	= THIS_MODULE,
     28	.obj_size = sizeof(struct sock),
     29};
     30
     31struct pvcalls_bedata {
     32	struct xen_pvcalls_front_ring ring;
     33	grant_ref_t ref;
     34	int irq;
     35
     36	struct list_head socket_mappings;
     37	spinlock_t socket_lock;
     38
     39	wait_queue_head_t inflight_req;
     40	struct xen_pvcalls_response rsp[PVCALLS_NR_RSP_PER_RING];
     41};
     42/* Only one front/back connection supported. */
     43static struct xenbus_device *pvcalls_front_dev;
     44static atomic_t pvcalls_refcount;
     45
     46/* first increment refcount, then proceed */
     47#define pvcalls_enter() {               \
     48	atomic_inc(&pvcalls_refcount);      \
     49}
     50
     51/* first complete other operations, then decrement refcount */
     52#define pvcalls_exit() {                \
     53	atomic_dec(&pvcalls_refcount);      \
     54}
     55
     56struct sock_mapping {
     57	bool active_socket;
     58	struct list_head list;
     59	struct socket *sock;
     60	atomic_t refcount;
     61	union {
     62		struct {
     63			int irq;
     64			grant_ref_t ref;
     65			struct pvcalls_data_intf *ring;
     66			struct pvcalls_data data;
     67			struct mutex in_mutex;
     68			struct mutex out_mutex;
     69
     70			wait_queue_head_t inflight_conn_req;
     71		} active;
     72		struct {
     73		/*
     74		 * Socket status, needs to be 64-bit aligned due to the
     75		 * test_and_* functions which have this requirement on arm64.
     76		 */
     77#define PVCALLS_STATUS_UNINITALIZED  0
     78#define PVCALLS_STATUS_BIND          1
     79#define PVCALLS_STATUS_LISTEN        2
     80			uint8_t status __attribute__((aligned(8)));
     81		/*
     82		 * Internal state-machine flags.
     83		 * Only one accept operation can be inflight for a socket.
     84		 * Only one poll operation can be inflight for a given socket.
     85		 * flags needs to be 64-bit aligned due to the test_and_*
     86		 * functions which have this requirement on arm64.
     87		 */
     88#define PVCALLS_FLAG_ACCEPT_INFLIGHT 0
     89#define PVCALLS_FLAG_POLL_INFLIGHT   1
     90#define PVCALLS_FLAG_POLL_RET        2
     91			uint8_t flags __attribute__((aligned(8)));
     92			uint32_t inflight_req_id;
     93			struct sock_mapping *accept_map;
     94			wait_queue_head_t inflight_accept_req;
     95		} passive;
     96	};
     97};
     98
     99static inline struct sock_mapping *pvcalls_enter_sock(struct socket *sock)
    100{
    101	struct sock_mapping *map;
    102
    103	if (!pvcalls_front_dev ||
    104		dev_get_drvdata(&pvcalls_front_dev->dev) == NULL)
    105		return ERR_PTR(-ENOTCONN);
    106
    107	map = (struct sock_mapping *)sock->sk->sk_send_head;
    108	if (map == NULL)
    109		return ERR_PTR(-ENOTSOCK);
    110
    111	pvcalls_enter();
    112	atomic_inc(&map->refcount);
    113	return map;
    114}
    115
    116static inline void pvcalls_exit_sock(struct socket *sock)
    117{
    118	struct sock_mapping *map;
    119
    120	map = (struct sock_mapping *)sock->sk->sk_send_head;
    121	atomic_dec(&map->refcount);
    122	pvcalls_exit();
    123}
    124
    125static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
    126{
    127	*req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
    128	if (RING_FULL(&bedata->ring) ||
    129	    bedata->rsp[*req_id].req_id != PVCALLS_INVALID_ID)
    130		return -EAGAIN;
    131	return 0;
    132}
    133
    134static bool pvcalls_front_write_todo(struct sock_mapping *map)
    135{
    136	struct pvcalls_data_intf *intf = map->active.ring;
    137	RING_IDX cons, prod, size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
    138	int32_t error;
    139
    140	error = intf->out_error;
    141	if (error == -ENOTCONN)
    142		return false;
    143	if (error != 0)
    144		return true;
    145
    146	cons = intf->out_cons;
    147	prod = intf->out_prod;
    148	return !!(size - pvcalls_queued(prod, cons, size));
    149}
    150
    151static bool pvcalls_front_read_todo(struct sock_mapping *map)
    152{
    153	struct pvcalls_data_intf *intf = map->active.ring;
    154	RING_IDX cons, prod;
    155	int32_t error;
    156
    157	cons = intf->in_cons;
    158	prod = intf->in_prod;
    159	error = intf->in_error;
    160	return (error != 0 ||
    161		pvcalls_queued(prod, cons,
    162			       XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER)) != 0);
    163}
    164
    165static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
    166{
    167	struct xenbus_device *dev = dev_id;
    168	struct pvcalls_bedata *bedata;
    169	struct xen_pvcalls_response *rsp;
    170	uint8_t *src, *dst;
    171	int req_id = 0, more = 0, done = 0;
    172
    173	if (dev == NULL)
    174		return IRQ_HANDLED;
    175
    176	pvcalls_enter();
    177	bedata = dev_get_drvdata(&dev->dev);
    178	if (bedata == NULL) {
    179		pvcalls_exit();
    180		return IRQ_HANDLED;
    181	}
    182
    183again:
    184	while (RING_HAS_UNCONSUMED_RESPONSES(&bedata->ring)) {
    185		rsp = RING_GET_RESPONSE(&bedata->ring, bedata->ring.rsp_cons);
    186
    187		req_id = rsp->req_id;
    188		if (rsp->cmd == PVCALLS_POLL) {
    189			struct sock_mapping *map = (struct sock_mapping *)(uintptr_t)
    190						   rsp->u.poll.id;
    191
    192			clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
    193				  (void *)&map->passive.flags);
    194			/*
    195			 * clear INFLIGHT, then set RET. It pairs with
    196			 * the checks at the beginning of
    197			 * pvcalls_front_poll_passive.
    198			 */
    199			smp_wmb();
    200			set_bit(PVCALLS_FLAG_POLL_RET,
    201				(void *)&map->passive.flags);
    202		} else {
    203			dst = (uint8_t *)&bedata->rsp[req_id] +
    204			      sizeof(rsp->req_id);
    205			src = (uint8_t *)rsp + sizeof(rsp->req_id);
    206			memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
    207			/*
    208			 * First copy the rest of the data, then req_id. It is
    209			 * paired with the barrier when accessing bedata->rsp.
    210			 */
    211			smp_wmb();
    212			bedata->rsp[req_id].req_id = req_id;
    213		}
    214
    215		done = 1;
    216		bedata->ring.rsp_cons++;
    217	}
    218
    219	RING_FINAL_CHECK_FOR_RESPONSES(&bedata->ring, more);
    220	if (more)
    221		goto again;
    222	if (done)
    223		wake_up(&bedata->inflight_req);
    224	pvcalls_exit();
    225	return IRQ_HANDLED;
    226}
    227
    228static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
    229				   struct sock_mapping *map)
    230{
    231	int i;
    232
    233	unbind_from_irqhandler(map->active.irq, map);
    234
    235	spin_lock(&bedata->socket_lock);
    236	if (!list_empty(&map->list))
    237		list_del_init(&map->list);
    238	spin_unlock(&bedata->socket_lock);
    239
    240	for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
    241		gnttab_end_foreign_access(map->active.ring->ref[i], NULL);
    242	gnttab_end_foreign_access(map->active.ref, NULL);
    243	free_page((unsigned long)map->active.ring);
    244
    245	kfree(map);
    246}
    247
    248static irqreturn_t pvcalls_front_conn_handler(int irq, void *sock_map)
    249{
    250	struct sock_mapping *map = sock_map;
    251
    252	if (map == NULL)
    253		return IRQ_HANDLED;
    254
    255	wake_up_interruptible(&map->active.inflight_conn_req);
    256
    257	return IRQ_HANDLED;
    258}
    259
    260int pvcalls_front_socket(struct socket *sock)
    261{
    262	struct pvcalls_bedata *bedata;
    263	struct sock_mapping *map = NULL;
    264	struct xen_pvcalls_request *req;
    265	int notify, req_id, ret;
    266
    267	/*
    268	 * PVCalls only supports domain AF_INET,
    269	 * type SOCK_STREAM and protocol 0 sockets for now.
    270	 *
    271	 * Check socket type here, AF_INET and protocol checks are done
    272	 * by the caller.
    273	 */
    274	if (sock->type != SOCK_STREAM)
    275		return -EOPNOTSUPP;
    276
    277	pvcalls_enter();
    278	if (!pvcalls_front_dev) {
    279		pvcalls_exit();
    280		return -EACCES;
    281	}
    282	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
    283
    284	map = kzalloc(sizeof(*map), GFP_KERNEL);
    285	if (map == NULL) {
    286		pvcalls_exit();
    287		return -ENOMEM;
    288	}
    289
    290	spin_lock(&bedata->socket_lock);
    291
    292	ret = get_request(bedata, &req_id);
    293	if (ret < 0) {
    294		kfree(map);
    295		spin_unlock(&bedata->socket_lock);
    296		pvcalls_exit();
    297		return ret;
    298	}
    299
    300	/*
    301	 * sock->sk->sk_send_head is not used for ip sockets: reuse the
    302	 * field to store a pointer to the struct sock_mapping
    303	 * corresponding to the socket. This way, we can easily get the
    304	 * struct sock_mapping from the struct socket.
    305	 */
    306	sock->sk->sk_send_head = (void *)map;
    307	list_add_tail(&map->list, &bedata->socket_mappings);
    308
    309	req = RING_GET_REQUEST(&bedata->ring, req_id);
    310	req->req_id = req_id;
    311	req->cmd = PVCALLS_SOCKET;
    312	req->u.socket.id = (uintptr_t) map;
    313	req->u.socket.domain = AF_INET;
    314	req->u.socket.type = SOCK_STREAM;
    315	req->u.socket.protocol = IPPROTO_IP;
    316
    317	bedata->ring.req_prod_pvt++;
    318	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
    319	spin_unlock(&bedata->socket_lock);
    320	if (notify)
    321		notify_remote_via_irq(bedata->irq);
    322
    323	wait_event(bedata->inflight_req,
    324		   READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
    325
    326	/* read req_id, then the content */
    327	smp_rmb();
    328	ret = bedata->rsp[req_id].ret;
    329	bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
    330
    331	pvcalls_exit();
    332	return ret;
    333}
    334
    335static void free_active_ring(struct sock_mapping *map)
    336{
    337	if (!map->active.ring)
    338		return;
    339
    340	free_pages_exact(map->active.data.in,
    341			 PAGE_SIZE << map->active.ring->ring_order);
    342	free_page((unsigned long)map->active.ring);
    343}
    344
    345static int alloc_active_ring(struct sock_mapping *map)
    346{
    347	void *bytes;
    348
    349	map->active.ring = (struct pvcalls_data_intf *)
    350		get_zeroed_page(GFP_KERNEL);
    351	if (!map->active.ring)
    352		goto out;
    353
    354	map->active.ring->ring_order = PVCALLS_RING_ORDER;
    355	bytes = alloc_pages_exact(PAGE_SIZE << PVCALLS_RING_ORDER,
    356				  GFP_KERNEL | __GFP_ZERO);
    357	if (!bytes)
    358		goto out;
    359
    360	map->active.data.in = bytes;
    361	map->active.data.out = bytes +
    362		XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
    363
    364	return 0;
    365
    366out:
    367	free_active_ring(map);
    368	return -ENOMEM;
    369}
    370
    371static int create_active(struct sock_mapping *map, evtchn_port_t *evtchn)
    372{
    373	void *bytes;
    374	int ret, irq = -1, i;
    375
    376	*evtchn = 0;
    377	init_waitqueue_head(&map->active.inflight_conn_req);
    378
    379	bytes = map->active.data.in;
    380	for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
    381		map->active.ring->ref[i] = gnttab_grant_foreign_access(
    382			pvcalls_front_dev->otherend_id,
    383			pfn_to_gfn(virt_to_pfn(bytes) + i), 0);
    384
    385	map->active.ref = gnttab_grant_foreign_access(
    386		pvcalls_front_dev->otherend_id,
    387		pfn_to_gfn(virt_to_pfn((void *)map->active.ring)), 0);
    388
    389	ret = xenbus_alloc_evtchn(pvcalls_front_dev, evtchn);
    390	if (ret)
    391		goto out_error;
    392	irq = bind_evtchn_to_irqhandler(*evtchn, pvcalls_front_conn_handler,
    393					0, "pvcalls-frontend", map);
    394	if (irq < 0) {
    395		ret = irq;
    396		goto out_error;
    397	}
    398
    399	map->active.irq = irq;
    400	map->active_socket = true;
    401	mutex_init(&map->active.in_mutex);
    402	mutex_init(&map->active.out_mutex);
    403
    404	return 0;
    405
    406out_error:
    407	if (*evtchn > 0)
    408		xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
    409	return ret;
    410}
    411
    412int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
    413				int addr_len, int flags)
    414{
    415	struct pvcalls_bedata *bedata;
    416	struct sock_mapping *map = NULL;
    417	struct xen_pvcalls_request *req;
    418	int notify, req_id, ret;
    419	evtchn_port_t evtchn;
    420
    421	if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
    422		return -EOPNOTSUPP;
    423
    424	map = pvcalls_enter_sock(sock);
    425	if (IS_ERR(map))
    426		return PTR_ERR(map);
    427
    428	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
    429	ret = alloc_active_ring(map);
    430	if (ret < 0) {
    431		pvcalls_exit_sock(sock);
    432		return ret;
    433	}
    434
    435	spin_lock(&bedata->socket_lock);
    436	ret = get_request(bedata, &req_id);
    437	if (ret < 0) {
    438		spin_unlock(&bedata->socket_lock);
    439		free_active_ring(map);
    440		pvcalls_exit_sock(sock);
    441		return ret;
    442	}
    443	ret = create_active(map, &evtchn);
    444	if (ret < 0) {
    445		spin_unlock(&bedata->socket_lock);
    446		free_active_ring(map);
    447		pvcalls_exit_sock(sock);
    448		return ret;
    449	}
    450
    451	req = RING_GET_REQUEST(&bedata->ring, req_id);
    452	req->req_id = req_id;
    453	req->cmd = PVCALLS_CONNECT;
    454	req->u.connect.id = (uintptr_t)map;
    455	req->u.connect.len = addr_len;
    456	req->u.connect.flags = flags;
    457	req->u.connect.ref = map->active.ref;
    458	req->u.connect.evtchn = evtchn;
    459	memcpy(req->u.connect.addr, addr, sizeof(*addr));
    460
    461	map->sock = sock;
    462
    463	bedata->ring.req_prod_pvt++;
    464	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
    465	spin_unlock(&bedata->socket_lock);
    466
    467	if (notify)
    468		notify_remote_via_irq(bedata->irq);
    469
    470	wait_event(bedata->inflight_req,
    471		   READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
    472
    473	/* read req_id, then the content */
    474	smp_rmb();
    475	ret = bedata->rsp[req_id].ret;
    476	bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
    477	pvcalls_exit_sock(sock);
    478	return ret;
    479}
    480
    481static int __write_ring(struct pvcalls_data_intf *intf,
    482			struct pvcalls_data *data,
    483			struct iov_iter *msg_iter,
    484			int len)
    485{
    486	RING_IDX cons, prod, size, masked_prod, masked_cons;
    487	RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
    488	int32_t error;
    489
    490	error = intf->out_error;
    491	if (error < 0)
    492		return error;
    493	cons = intf->out_cons;
    494	prod = intf->out_prod;
    495	/* read indexes before continuing */
    496	virt_mb();
    497
    498	size = pvcalls_queued(prod, cons, array_size);
    499	if (size > array_size)
    500		return -EINVAL;
    501	if (size == array_size)
    502		return 0;
    503	if (len > array_size - size)
    504		len = array_size - size;
    505
    506	masked_prod = pvcalls_mask(prod, array_size);
    507	masked_cons = pvcalls_mask(cons, array_size);
    508
    509	if (masked_prod < masked_cons) {
    510		len = copy_from_iter(data->out + masked_prod, len, msg_iter);
    511	} else {
    512		if (len > array_size - masked_prod) {
    513			int ret = copy_from_iter(data->out + masked_prod,
    514				       array_size - masked_prod, msg_iter);
    515			if (ret != array_size - masked_prod) {
    516				len = ret;
    517				goto out;
    518			}
    519			len = ret + copy_from_iter(data->out, len - ret, msg_iter);
    520		} else {
    521			len = copy_from_iter(data->out + masked_prod, len, msg_iter);
    522		}
    523	}
    524out:
    525	/* write to ring before updating pointer */
    526	virt_wmb();
    527	intf->out_prod += len;
    528
    529	return len;
    530}
    531
    532int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
    533			  size_t len)
    534{
    535	struct sock_mapping *map;
    536	int sent, tot_sent = 0;
    537	int count = 0, flags;
    538
    539	flags = msg->msg_flags;
    540	if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
    541		return -EOPNOTSUPP;
    542
    543	map = pvcalls_enter_sock(sock);
    544	if (IS_ERR(map))
    545		return PTR_ERR(map);
    546
    547	mutex_lock(&map->active.out_mutex);
    548	if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
    549		mutex_unlock(&map->active.out_mutex);
    550		pvcalls_exit_sock(sock);
    551		return -EAGAIN;
    552	}
    553	if (len > INT_MAX)
    554		len = INT_MAX;
    555
    556again:
    557	count++;
    558	sent = __write_ring(map->active.ring,
    559			    &map->active.data, &msg->msg_iter,
    560			    len);
    561	if (sent > 0) {
    562		len -= sent;
    563		tot_sent += sent;
    564		notify_remote_via_irq(map->active.irq);
    565	}
    566	if (sent >= 0 && len > 0 && count < PVCALLS_FRONT_MAX_SPIN)
    567		goto again;
    568	if (sent < 0)
    569		tot_sent = sent;
    570
    571	mutex_unlock(&map->active.out_mutex);
    572	pvcalls_exit_sock(sock);
    573	return tot_sent;
    574}
    575
    576static int __read_ring(struct pvcalls_data_intf *intf,
    577		       struct pvcalls_data *data,
    578		       struct iov_iter *msg_iter,
    579		       size_t len, int flags)
    580{
    581	RING_IDX cons, prod, size, masked_prod, masked_cons;
    582	RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
    583	int32_t error;
    584
    585	cons = intf->in_cons;
    586	prod = intf->in_prod;
    587	error = intf->in_error;
    588	/* get pointers before reading from the ring */
    589	virt_rmb();
    590
    591	size = pvcalls_queued(prod, cons, array_size);
    592	masked_prod = pvcalls_mask(prod, array_size);
    593	masked_cons = pvcalls_mask(cons, array_size);
    594
    595	if (size == 0)
    596		return error ?: size;
    597
    598	if (len > size)
    599		len = size;
    600
    601	if (masked_prod > masked_cons) {
    602		len = copy_to_iter(data->in + masked_cons, len, msg_iter);
    603	} else {
    604		if (len > (array_size - masked_cons)) {
    605			int ret = copy_to_iter(data->in + masked_cons,
    606				     array_size - masked_cons, msg_iter);
    607			if (ret != array_size - masked_cons) {
    608				len = ret;
    609				goto out;
    610			}
    611			len = ret + copy_to_iter(data->in, len - ret, msg_iter);
    612		} else {
    613			len = copy_to_iter(data->in + masked_cons, len, msg_iter);
    614		}
    615	}
    616out:
    617	/* read data from the ring before increasing the index */
    618	virt_mb();
    619	if (!(flags & MSG_PEEK))
    620		intf->in_cons += len;
    621
    622	return len;
    623}
    624
    625int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
    626		     int flags)
    627{
    628	int ret;
    629	struct sock_mapping *map;
    630
    631	if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
    632		return -EOPNOTSUPP;
    633
    634	map = pvcalls_enter_sock(sock);
    635	if (IS_ERR(map))
    636		return PTR_ERR(map);
    637
    638	mutex_lock(&map->active.in_mutex);
    639	if (len > XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER))
    640		len = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
    641
    642	while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
    643		wait_event_interruptible(map->active.inflight_conn_req,
    644					 pvcalls_front_read_todo(map));
    645	}
    646	ret = __read_ring(map->active.ring, &map->active.data,
    647			  &msg->msg_iter, len, flags);
    648
    649	if (ret > 0)
    650		notify_remote_via_irq(map->active.irq);
    651	if (ret == 0)
    652		ret = (flags & MSG_DONTWAIT) ? -EAGAIN : 0;
    653	if (ret == -ENOTCONN)
    654		ret = 0;
    655
    656	mutex_unlock(&map->active.in_mutex);
    657	pvcalls_exit_sock(sock);
    658	return ret;
    659}
    660
    661int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
    662{
    663	struct pvcalls_bedata *bedata;
    664	struct sock_mapping *map = NULL;
    665	struct xen_pvcalls_request *req;
    666	int notify, req_id, ret;
    667
    668	if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
    669		return -EOPNOTSUPP;
    670
    671	map = pvcalls_enter_sock(sock);
    672	if (IS_ERR(map))
    673		return PTR_ERR(map);
    674	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
    675
    676	spin_lock(&bedata->socket_lock);
    677	ret = get_request(bedata, &req_id);
    678	if (ret < 0) {
    679		spin_unlock(&bedata->socket_lock);
    680		pvcalls_exit_sock(sock);
    681		return ret;
    682	}
    683	req = RING_GET_REQUEST(&bedata->ring, req_id);
    684	req->req_id = req_id;
    685	map->sock = sock;
    686	req->cmd = PVCALLS_BIND;
    687	req->u.bind.id = (uintptr_t)map;
    688	memcpy(req->u.bind.addr, addr, sizeof(*addr));
    689	req->u.bind.len = addr_len;
    690
    691	init_waitqueue_head(&map->passive.inflight_accept_req);
    692
    693	map->active_socket = false;
    694
    695	bedata->ring.req_prod_pvt++;
    696	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
    697	spin_unlock(&bedata->socket_lock);
    698	if (notify)
    699		notify_remote_via_irq(bedata->irq);
    700
    701	wait_event(bedata->inflight_req,
    702		   READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
    703
    704	/* read req_id, then the content */
    705	smp_rmb();
    706	ret = bedata->rsp[req_id].ret;
    707	bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
    708
    709	map->passive.status = PVCALLS_STATUS_BIND;
    710	pvcalls_exit_sock(sock);
    711	return 0;
    712}
    713
    714int pvcalls_front_listen(struct socket *sock, int backlog)
    715{
    716	struct pvcalls_bedata *bedata;
    717	struct sock_mapping *map;
    718	struct xen_pvcalls_request *req;
    719	int notify, req_id, ret;
    720
    721	map = pvcalls_enter_sock(sock);
    722	if (IS_ERR(map))
    723		return PTR_ERR(map);
    724	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
    725
    726	if (map->passive.status != PVCALLS_STATUS_BIND) {
    727		pvcalls_exit_sock(sock);
    728		return -EOPNOTSUPP;
    729	}
    730
    731	spin_lock(&bedata->socket_lock);
    732	ret = get_request(bedata, &req_id);
    733	if (ret < 0) {
    734		spin_unlock(&bedata->socket_lock);
    735		pvcalls_exit_sock(sock);
    736		return ret;
    737	}
    738	req = RING_GET_REQUEST(&bedata->ring, req_id);
    739	req->req_id = req_id;
    740	req->cmd = PVCALLS_LISTEN;
    741	req->u.listen.id = (uintptr_t) map;
    742	req->u.listen.backlog = backlog;
    743
    744	bedata->ring.req_prod_pvt++;
    745	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
    746	spin_unlock(&bedata->socket_lock);
    747	if (notify)
    748		notify_remote_via_irq(bedata->irq);
    749
    750	wait_event(bedata->inflight_req,
    751		   READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
    752
    753	/* read req_id, then the content */
    754	smp_rmb();
    755	ret = bedata->rsp[req_id].ret;
    756	bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
    757
    758	map->passive.status = PVCALLS_STATUS_LISTEN;
    759	pvcalls_exit_sock(sock);
    760	return ret;
    761}
    762
    763int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
    764{
    765	struct pvcalls_bedata *bedata;
    766	struct sock_mapping *map;
    767	struct sock_mapping *map2 = NULL;
    768	struct xen_pvcalls_request *req;
    769	int notify, req_id, ret, nonblock;
    770	evtchn_port_t evtchn;
    771
    772	map = pvcalls_enter_sock(sock);
    773	if (IS_ERR(map))
    774		return PTR_ERR(map);
    775	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
    776
    777	if (map->passive.status != PVCALLS_STATUS_LISTEN) {
    778		pvcalls_exit_sock(sock);
    779		return -EINVAL;
    780	}
    781
    782	nonblock = flags & SOCK_NONBLOCK;
    783	/*
    784	 * Backend only supports 1 inflight accept request, will return
    785	 * errors for the others
    786	 */
    787	if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
    788			     (void *)&map->passive.flags)) {
    789		req_id = READ_ONCE(map->passive.inflight_req_id);
    790		if (req_id != PVCALLS_INVALID_ID &&
    791		    READ_ONCE(bedata->rsp[req_id].req_id) == req_id) {
    792			map2 = map->passive.accept_map;
    793			goto received;
    794		}
    795		if (nonblock) {
    796			pvcalls_exit_sock(sock);
    797			return -EAGAIN;
    798		}
    799		if (wait_event_interruptible(map->passive.inflight_accept_req,
    800			!test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
    801					  (void *)&map->passive.flags))) {
    802			pvcalls_exit_sock(sock);
    803			return -EINTR;
    804		}
    805	}
    806
    807	map2 = kzalloc(sizeof(*map2), GFP_KERNEL);
    808	if (map2 == NULL) {
    809		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
    810			  (void *)&map->passive.flags);
    811		pvcalls_exit_sock(sock);
    812		return -ENOMEM;
    813	}
    814	ret = alloc_active_ring(map2);
    815	if (ret < 0) {
    816		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
    817				(void *)&map->passive.flags);
    818		kfree(map2);
    819		pvcalls_exit_sock(sock);
    820		return ret;
    821	}
    822	spin_lock(&bedata->socket_lock);
    823	ret = get_request(bedata, &req_id);
    824	if (ret < 0) {
    825		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
    826			  (void *)&map->passive.flags);
    827		spin_unlock(&bedata->socket_lock);
    828		free_active_ring(map2);
    829		kfree(map2);
    830		pvcalls_exit_sock(sock);
    831		return ret;
    832	}
    833
    834	ret = create_active(map2, &evtchn);
    835	if (ret < 0) {
    836		free_active_ring(map2);
    837		kfree(map2);
    838		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
    839			  (void *)&map->passive.flags);
    840		spin_unlock(&bedata->socket_lock);
    841		pvcalls_exit_sock(sock);
    842		return ret;
    843	}
    844	list_add_tail(&map2->list, &bedata->socket_mappings);
    845
    846	req = RING_GET_REQUEST(&bedata->ring, req_id);
    847	req->req_id = req_id;
    848	req->cmd = PVCALLS_ACCEPT;
    849	req->u.accept.id = (uintptr_t) map;
    850	req->u.accept.ref = map2->active.ref;
    851	req->u.accept.id_new = (uintptr_t) map2;
    852	req->u.accept.evtchn = evtchn;
    853	map->passive.accept_map = map2;
    854
    855	bedata->ring.req_prod_pvt++;
    856	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
    857	spin_unlock(&bedata->socket_lock);
    858	if (notify)
    859		notify_remote_via_irq(bedata->irq);
    860	/* We could check if we have received a response before returning. */
    861	if (nonblock) {
    862		WRITE_ONCE(map->passive.inflight_req_id, req_id);
    863		pvcalls_exit_sock(sock);
    864		return -EAGAIN;
    865	}
    866
    867	if (wait_event_interruptible(bedata->inflight_req,
    868		READ_ONCE(bedata->rsp[req_id].req_id) == req_id)) {
    869		pvcalls_exit_sock(sock);
    870		return -EINTR;
    871	}
    872	/* read req_id, then the content */
    873	smp_rmb();
    874
    875received:
    876	map2->sock = newsock;
    877	newsock->sk = sk_alloc(sock_net(sock->sk), PF_INET, GFP_KERNEL, &pvcalls_proto, false);
    878	if (!newsock->sk) {
    879		bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
    880		map->passive.inflight_req_id = PVCALLS_INVALID_ID;
    881		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
    882			  (void *)&map->passive.flags);
    883		pvcalls_front_free_map(bedata, map2);
    884		pvcalls_exit_sock(sock);
    885		return -ENOMEM;
    886	}
    887	newsock->sk->sk_send_head = (void *)map2;
    888
    889	ret = bedata->rsp[req_id].ret;
    890	bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
    891	map->passive.inflight_req_id = PVCALLS_INVALID_ID;
    892
    893	clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
    894	wake_up(&map->passive.inflight_accept_req);
    895
    896	pvcalls_exit_sock(sock);
    897	return ret;
    898}
    899
    900static __poll_t pvcalls_front_poll_passive(struct file *file,
    901					       struct pvcalls_bedata *bedata,
    902					       struct sock_mapping *map,
    903					       poll_table *wait)
    904{
    905	int notify, req_id, ret;
    906	struct xen_pvcalls_request *req;
    907
    908	if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
    909		     (void *)&map->passive.flags)) {
    910		uint32_t req_id = READ_ONCE(map->passive.inflight_req_id);
    911
    912		if (req_id != PVCALLS_INVALID_ID &&
    913		    READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
    914			return EPOLLIN | EPOLLRDNORM;
    915
    916		poll_wait(file, &map->passive.inflight_accept_req, wait);
    917		return 0;
    918	}
    919
    920	if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
    921			       (void *)&map->passive.flags))
    922		return EPOLLIN | EPOLLRDNORM;
    923
    924	/*
    925	 * First check RET, then INFLIGHT. No barriers necessary to
    926	 * ensure execution ordering because of the conditional
    927	 * instructions creating control dependencies.
    928	 */
    929
    930	if (test_and_set_bit(PVCALLS_FLAG_POLL_INFLIGHT,
    931			     (void *)&map->passive.flags)) {
    932		poll_wait(file, &bedata->inflight_req, wait);
    933		return 0;
    934	}
    935
    936	spin_lock(&bedata->socket_lock);
    937	ret = get_request(bedata, &req_id);
    938	if (ret < 0) {
    939		spin_unlock(&bedata->socket_lock);
    940		return ret;
    941	}
    942	req = RING_GET_REQUEST(&bedata->ring, req_id);
    943	req->req_id = req_id;
    944	req->cmd = PVCALLS_POLL;
    945	req->u.poll.id = (uintptr_t) map;
    946
    947	bedata->ring.req_prod_pvt++;
    948	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
    949	spin_unlock(&bedata->socket_lock);
    950	if (notify)
    951		notify_remote_via_irq(bedata->irq);
    952
    953	poll_wait(file, &bedata->inflight_req, wait);
    954	return 0;
    955}
    956
    957static __poll_t pvcalls_front_poll_active(struct file *file,
    958					      struct pvcalls_bedata *bedata,
    959					      struct sock_mapping *map,
    960					      poll_table *wait)
    961{
    962	__poll_t mask = 0;
    963	int32_t in_error, out_error;
    964	struct pvcalls_data_intf *intf = map->active.ring;
    965
    966	out_error = intf->out_error;
    967	in_error = intf->in_error;
    968
    969	poll_wait(file, &map->active.inflight_conn_req, wait);
    970	if (pvcalls_front_write_todo(map))
    971		mask |= EPOLLOUT | EPOLLWRNORM;
    972	if (pvcalls_front_read_todo(map))
    973		mask |= EPOLLIN | EPOLLRDNORM;
    974	if (in_error != 0 || out_error != 0)
    975		mask |= EPOLLERR;
    976
    977	return mask;
    978}
    979
    980__poll_t pvcalls_front_poll(struct file *file, struct socket *sock,
    981			       poll_table *wait)
    982{
    983	struct pvcalls_bedata *bedata;
    984	struct sock_mapping *map;
    985	__poll_t ret;
    986
    987	map = pvcalls_enter_sock(sock);
    988	if (IS_ERR(map))
    989		return EPOLLNVAL;
    990	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
    991
    992	if (map->active_socket)
    993		ret = pvcalls_front_poll_active(file, bedata, map, wait);
    994	else
    995		ret = pvcalls_front_poll_passive(file, bedata, map, wait);
    996	pvcalls_exit_sock(sock);
    997	return ret;
    998}
    999
   1000int pvcalls_front_release(struct socket *sock)
   1001{
   1002	struct pvcalls_bedata *bedata;
   1003	struct sock_mapping *map;
   1004	int req_id, notify, ret;
   1005	struct xen_pvcalls_request *req;
   1006
   1007	if (sock->sk == NULL)
   1008		return 0;
   1009
   1010	map = pvcalls_enter_sock(sock);
   1011	if (IS_ERR(map)) {
   1012		if (PTR_ERR(map) == -ENOTCONN)
   1013			return -EIO;
   1014		else
   1015			return 0;
   1016	}
   1017	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
   1018
   1019	spin_lock(&bedata->socket_lock);
   1020	ret = get_request(bedata, &req_id);
   1021	if (ret < 0) {
   1022		spin_unlock(&bedata->socket_lock);
   1023		pvcalls_exit_sock(sock);
   1024		return ret;
   1025	}
   1026	sock->sk->sk_send_head = NULL;
   1027
   1028	req = RING_GET_REQUEST(&bedata->ring, req_id);
   1029	req->req_id = req_id;
   1030	req->cmd = PVCALLS_RELEASE;
   1031	req->u.release.id = (uintptr_t)map;
   1032
   1033	bedata->ring.req_prod_pvt++;
   1034	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
   1035	spin_unlock(&bedata->socket_lock);
   1036	if (notify)
   1037		notify_remote_via_irq(bedata->irq);
   1038
   1039	wait_event(bedata->inflight_req,
   1040		   READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
   1041
   1042	if (map->active_socket) {
   1043		/*
   1044		 * Set in_error and wake up inflight_conn_req to force
   1045		 * recvmsg waiters to exit.
   1046		 */
   1047		map->active.ring->in_error = -EBADF;
   1048		wake_up_interruptible(&map->active.inflight_conn_req);
   1049
   1050		/*
   1051		 * We need to make sure that sendmsg/recvmsg on this socket have
   1052		 * not started before we've cleared sk_send_head here. The
   1053		 * easiest way to guarantee this is to see that no pvcalls
   1054		 * (other than us) is in progress on this socket.
   1055		 */
   1056		while (atomic_read(&map->refcount) > 1)
   1057			cpu_relax();
   1058
   1059		pvcalls_front_free_map(bedata, map);
   1060	} else {
   1061		wake_up(&bedata->inflight_req);
   1062		wake_up(&map->passive.inflight_accept_req);
   1063
   1064		while (atomic_read(&map->refcount) > 1)
   1065			cpu_relax();
   1066
   1067		spin_lock(&bedata->socket_lock);
   1068		list_del(&map->list);
   1069		spin_unlock(&bedata->socket_lock);
   1070		if (READ_ONCE(map->passive.inflight_req_id) != PVCALLS_INVALID_ID &&
   1071			READ_ONCE(map->passive.inflight_req_id) != 0) {
   1072			pvcalls_front_free_map(bedata,
   1073					       map->passive.accept_map);
   1074		}
   1075		kfree(map);
   1076	}
   1077	WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
   1078
   1079	pvcalls_exit();
   1080	return 0;
   1081}
   1082
   1083static const struct xenbus_device_id pvcalls_front_ids[] = {
   1084	{ "pvcalls" },
   1085	{ "" }
   1086};
   1087
   1088static int pvcalls_front_remove(struct xenbus_device *dev)
   1089{
   1090	struct pvcalls_bedata *bedata;
   1091	struct sock_mapping *map = NULL, *n;
   1092
   1093	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
   1094	dev_set_drvdata(&dev->dev, NULL);
   1095	pvcalls_front_dev = NULL;
   1096	if (bedata->irq >= 0)
   1097		unbind_from_irqhandler(bedata->irq, dev);
   1098
   1099	list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
   1100		map->sock->sk->sk_send_head = NULL;
   1101		if (map->active_socket) {
   1102			map->active.ring->in_error = -EBADF;
   1103			wake_up_interruptible(&map->active.inflight_conn_req);
   1104		}
   1105	}
   1106
   1107	smp_mb();
   1108	while (atomic_read(&pvcalls_refcount) > 0)
   1109		cpu_relax();
   1110	list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
   1111		if (map->active_socket) {
   1112			/* No need to lock, refcount is 0 */
   1113			pvcalls_front_free_map(bedata, map);
   1114		} else {
   1115			list_del(&map->list);
   1116			kfree(map);
   1117		}
   1118	}
   1119	if (bedata->ref != -1)
   1120		gnttab_end_foreign_access(bedata->ref, NULL);
   1121	kfree(bedata->ring.sring);
   1122	kfree(bedata);
   1123	xenbus_switch_state(dev, XenbusStateClosed);
   1124	return 0;
   1125}
   1126
   1127static int pvcalls_front_probe(struct xenbus_device *dev,
   1128			  const struct xenbus_device_id *id)
   1129{
   1130	int ret = -ENOMEM, i;
   1131	evtchn_port_t evtchn;
   1132	unsigned int max_page_order, function_calls, len;
   1133	char *versions;
   1134	grant_ref_t gref_head = 0;
   1135	struct xenbus_transaction xbt;
   1136	struct pvcalls_bedata *bedata = NULL;
   1137	struct xen_pvcalls_sring *sring;
   1138
   1139	if (pvcalls_front_dev != NULL) {
   1140		dev_err(&dev->dev, "only one PV Calls connection supported\n");
   1141		return -EINVAL;
   1142	}
   1143
   1144	versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
   1145	if (IS_ERR(versions))
   1146		return PTR_ERR(versions);
   1147	if (!len)
   1148		return -EINVAL;
   1149	if (strcmp(versions, "1")) {
   1150		kfree(versions);
   1151		return -EINVAL;
   1152	}
   1153	kfree(versions);
   1154	max_page_order = xenbus_read_unsigned(dev->otherend,
   1155					      "max-page-order", 0);
   1156	if (max_page_order < PVCALLS_RING_ORDER)
   1157		return -ENODEV;
   1158	function_calls = xenbus_read_unsigned(dev->otherend,
   1159					      "function-calls", 0);
   1160	/* See XENBUS_FUNCTIONS_CALLS in pvcalls.h */
   1161	if (function_calls != 1)
   1162		return -ENODEV;
   1163	pr_info("%s max-page-order is %u\n", __func__, max_page_order);
   1164
   1165	bedata = kzalloc(sizeof(struct pvcalls_bedata), GFP_KERNEL);
   1166	if (!bedata)
   1167		return -ENOMEM;
   1168
   1169	dev_set_drvdata(&dev->dev, bedata);
   1170	pvcalls_front_dev = dev;
   1171	init_waitqueue_head(&bedata->inflight_req);
   1172	INIT_LIST_HEAD(&bedata->socket_mappings);
   1173	spin_lock_init(&bedata->socket_lock);
   1174	bedata->irq = -1;
   1175	bedata->ref = -1;
   1176
   1177	for (i = 0; i < PVCALLS_NR_RSP_PER_RING; i++)
   1178		bedata->rsp[i].req_id = PVCALLS_INVALID_ID;
   1179
   1180	sring = (struct xen_pvcalls_sring *) __get_free_page(GFP_KERNEL |
   1181							     __GFP_ZERO);
   1182	if (!sring)
   1183		goto error;
   1184	SHARED_RING_INIT(sring);
   1185	FRONT_RING_INIT(&bedata->ring, sring, XEN_PAGE_SIZE);
   1186
   1187	ret = xenbus_alloc_evtchn(dev, &evtchn);
   1188	if (ret)
   1189		goto error;
   1190
   1191	bedata->irq = bind_evtchn_to_irqhandler(evtchn,
   1192						pvcalls_front_event_handler,
   1193						0, "pvcalls-frontend", dev);
   1194	if (bedata->irq < 0) {
   1195		ret = bedata->irq;
   1196		goto error;
   1197	}
   1198
   1199	ret = gnttab_alloc_grant_references(1, &gref_head);
   1200	if (ret < 0)
   1201		goto error;
   1202	ret = gnttab_claim_grant_reference(&gref_head);
   1203	if (ret < 0)
   1204		goto error;
   1205	bedata->ref = ret;
   1206	gnttab_grant_foreign_access_ref(bedata->ref, dev->otherend_id,
   1207					virt_to_gfn((void *)sring), 0);
   1208
   1209 again:
   1210	ret = xenbus_transaction_start(&xbt);
   1211	if (ret) {
   1212		xenbus_dev_fatal(dev, ret, "starting transaction");
   1213		goto error;
   1214	}
   1215	ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
   1216	if (ret)
   1217		goto error_xenbus;
   1218	ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", bedata->ref);
   1219	if (ret)
   1220		goto error_xenbus;
   1221	ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
   1222			    evtchn);
   1223	if (ret)
   1224		goto error_xenbus;
   1225	ret = xenbus_transaction_end(xbt, 0);
   1226	if (ret) {
   1227		if (ret == -EAGAIN)
   1228			goto again;
   1229		xenbus_dev_fatal(dev, ret, "completing transaction");
   1230		goto error;
   1231	}
   1232	xenbus_switch_state(dev, XenbusStateInitialised);
   1233
   1234	return 0;
   1235
   1236 error_xenbus:
   1237	xenbus_transaction_end(xbt, 1);
   1238	xenbus_dev_fatal(dev, ret, "writing xenstore");
   1239 error:
   1240	pvcalls_front_remove(dev);
   1241	return ret;
   1242}
   1243
   1244static void pvcalls_front_changed(struct xenbus_device *dev,
   1245			    enum xenbus_state backend_state)
   1246{
   1247	switch (backend_state) {
   1248	case XenbusStateReconfiguring:
   1249	case XenbusStateReconfigured:
   1250	case XenbusStateInitialising:
   1251	case XenbusStateInitialised:
   1252	case XenbusStateUnknown:
   1253		break;
   1254
   1255	case XenbusStateInitWait:
   1256		break;
   1257
   1258	case XenbusStateConnected:
   1259		xenbus_switch_state(dev, XenbusStateConnected);
   1260		break;
   1261
   1262	case XenbusStateClosed:
   1263		if (dev->state == XenbusStateClosed)
   1264			break;
   1265		/* Missed the backend's CLOSING state */
   1266		fallthrough;
   1267	case XenbusStateClosing:
   1268		xenbus_frontend_closed(dev);
   1269		break;
   1270	}
   1271}
   1272
   1273static struct xenbus_driver pvcalls_front_driver = {
   1274	.ids = pvcalls_front_ids,
   1275	.probe = pvcalls_front_probe,
   1276	.remove = pvcalls_front_remove,
   1277	.otherend_changed = pvcalls_front_changed,
   1278	.not_essential = true,
   1279};
   1280
   1281static int __init pvcalls_frontend_init(void)
   1282{
   1283	if (!xen_domain())
   1284		return -ENODEV;
   1285
   1286	pr_info("Initialising Xen pvcalls frontend driver\n");
   1287
   1288	return xenbus_register_frontend(&pvcalls_front_driver);
   1289}
   1290
   1291module_init(pvcalls_frontend_init);
   1292
   1293MODULE_DESCRIPTION("Xen PV Calls frontend driver");
   1294MODULE_AUTHOR("Stefano Stabellini <sstabellini@kernel.org>");
   1295MODULE_LICENSE("GPL");