1 /******************************************************************************
4 * Low level code to talks to Xen Store: ringbuffer and event channel.
6 * Copyright (C) 2005 Rusty Russell, IBM Corporation
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License version 2
10 * as published by the Free Software Foundation; or, when distributed
11 * separately from the Linux kernel or incorporated into other
12 * software packages, subject to the following license:
14 * Permission is hereby granted, free of charge, to any person obtaining a copy
15 * of this source file (the "Software"), to deal in the Software without
16 * restriction, including without limitation the rights to use, copy, modify,
17 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
18 * and to permit persons to whom the Software is furnished to do so, subject to
19 * the following conditions:
21 * The above copyright notice and this permission notice shall be included in
22 * all copies or substantial portions of the Software.
24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
25 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
26 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
27 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
28 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
29 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
33 #include <linux/wait.h>
34 #include <linux/interrupt.h>
35 #include <linux/sched.h>
36 #include <linux/err.h>
37 #include <xen/xenbus.h>
38 #if defined(CONFIG_XEN) || defined(MODULE)
39 #include <xen/evtchn.h>
40 #include <asm/hypervisor.h>
42 #include <asm/xen/hypervisor.h>
43 #include <xen/events.h>
47 #include "xenbus_comms.h"
49 #ifdef HAVE_XEN_PLATFORM_COMPAT_H
50 #include <xen/platform-compat.h>
53 static int xenbus_irq;
55 static DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
57 static irqreturn_t wake_waiting(int irq, void *unused)
59 #ifdef CONFIG_XEN_PRIVILEGED_GUEST
60 static DECLARE_WORK(probe_work, xenbus_probe);
63 old = atomic_read(&xenbus_xsd_state);
65 case XENBUS_XSD_UNCOMMITTED:
69 case XENBUS_XSD_FOREIGN_INIT:
70 new = XENBUS_XSD_FOREIGN_READY;
73 case XENBUS_XSD_LOCAL_INIT:
74 new = XENBUS_XSD_LOCAL_READY;
77 case XENBUS_XSD_FOREIGN_READY:
78 case XENBUS_XSD_LOCAL_READY:
83 old = atomic_cmpxchg(&xenbus_xsd_state, old, new);
85 schedule_work(&probe_work);
93 static int check_indexes(XENSTORE_RING_IDX cons, XENSTORE_RING_IDX prod)
95 return ((prod - cons) <= XENSTORE_RING_SIZE);
98 static void *get_output_chunk(XENSTORE_RING_IDX cons,
99 XENSTORE_RING_IDX prod,
100 char *buf, uint32_t *len)
102 *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod);
103 if ((XENSTORE_RING_SIZE - (prod - cons)) < *len)
104 *len = XENSTORE_RING_SIZE - (prod - cons);
105 return buf + MASK_XENSTORE_IDX(prod);
108 static const void *get_input_chunk(XENSTORE_RING_IDX cons,
109 XENSTORE_RING_IDX prod,
110 const char *buf, uint32_t *len)
112 *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(cons);
113 if ((prod - cons) < *len)
115 return buf + MASK_XENSTORE_IDX(cons);
119 * xb_write - low level write
120 * @data: buffer to send
121 * @len: length of buffer
123 * Returns 0 on success, error otherwise.
125 int xb_write(const void *data, unsigned len)
127 struct xenstore_domain_interface *intf = xen_store_interface;
128 XENSTORE_RING_IDX cons, prod;
135 rc = wait_event_interruptible(
137 (intf->req_prod - intf->req_cons) !=
142 /* Read indexes, then verify. */
143 cons = intf->req_cons;
144 prod = intf->req_prod;
145 if (!check_indexes(cons, prod)) {
146 intf->req_cons = intf->req_prod = 0;
150 dst = get_output_chunk(cons, prod, intf->req, &avail);
156 /* Must write data /after/ reading the consumer index. */
159 memcpy(dst, data, avail);
163 /* Other side must not see new producer until data is there. */
165 intf->req_prod += avail;
167 /* Implies mb(): other side will see the updated producer. */
168 notify_remote_via_evtchn(xen_store_evtchn);
174 int xb_data_to_read(void)
176 struct xenstore_domain_interface *intf = xen_store_interface;
177 return (intf->rsp_cons != intf->rsp_prod);
180 int xb_wait_for_data_to_read(void)
182 return wait_event_interruptible(xb_waitq, xb_data_to_read());
185 int xb_read(void *data, unsigned len)
187 struct xenstore_domain_interface *intf = xen_store_interface;
188 XENSTORE_RING_IDX cons, prod;
195 rc = xb_wait_for_data_to_read();
199 /* Read indexes, then verify. */
200 cons = intf->rsp_cons;
201 prod = intf->rsp_prod;
202 if (!check_indexes(cons, prod)) {
203 intf->rsp_cons = intf->rsp_prod = 0;
207 src = get_input_chunk(cons, prod, intf->rsp, &avail);
213 /* Must read data /after/ reading the producer index. */
216 memcpy(data, src, avail);
220 /* Other side must not see free space until we've copied out */
222 intf->rsp_cons += avail;
224 pr_debug("Finished read of %i bytes (%i to go)\n", avail, len);
226 /* Implies mb(): other side will see the updated consumer. */
227 notify_remote_via_evtchn(xen_store_evtchn);
234 * xb_init_comms - Set up interrupt handler off store event channel.
236 int xb_init_comms(void)
238 struct xenstore_domain_interface *intf = xen_store_interface;
241 if (intf->req_prod != intf->req_cons)
242 pr_err("XENBUS request ring is not quiescent "
243 "(%08x:%08x)!\n", intf->req_cons, intf->req_prod);
245 if (intf->rsp_prod != intf->rsp_cons) {
246 pr_warning("XENBUS response ring is not quiescent"
247 " (%08x:%08x): fixing up\n",
248 intf->rsp_cons, intf->rsp_prod);
251 intf->rsp_cons = intf->rsp_prod;
254 #if defined(CONFIG_XEN) || defined(MODULE)
256 unbind_from_irqhandler(xenbus_irq, &xb_waitq);
258 err = bind_caller_port_to_irqhandler(
259 xen_store_evtchn, wake_waiting,
260 0, "xenbus", &xb_waitq);
262 pr_err("XENBUS request irq failed %i\n", err);
269 /* Already have an irq; assume we're resuming */
270 rebind_evtchn_irq(xen_store_evtchn, xenbus_irq);
272 err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting,
273 0, "xenbus", &xb_waitq);
275 pr_err("XENBUS request irq failed %i\n", err);