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 #include <asm/xen/hypervisor.h>
39 #include <xen/events.h>
41 #include "xenbus_comms.h"
43 static int xenbus_irq;
45 static DECLARE_WORK(probe_work, xenbus_probe);
47 static DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
49 static irqreturn_t wake_waiting(int irq, void *unused)
51 if (unlikely(xenstored_ready == 0)) {
52 printk(KERN_CRIT "xenbus_probe wake_waiting\n");
54 schedule_work(&probe_work);
61 static int check_indexes(XENSTORE_RING_IDX cons, XENSTORE_RING_IDX prod)
63 return ((prod - cons) <= XENSTORE_RING_SIZE);
66 static void *get_output_chunk(XENSTORE_RING_IDX cons,
67 XENSTORE_RING_IDX prod,
68 char *buf, uint32_t *len)
70 *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod);
71 if ((XENSTORE_RING_SIZE - (prod - cons)) < *len)
72 *len = XENSTORE_RING_SIZE - (prod - cons);
73 return buf + MASK_XENSTORE_IDX(prod);
76 static const void *get_input_chunk(XENSTORE_RING_IDX cons,
77 XENSTORE_RING_IDX prod,
78 const char *buf, uint32_t *len)
80 *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(cons);
81 if ((prod - cons) < *len)
83 return buf + MASK_XENSTORE_IDX(cons);
87 * xb_write - low level write
88 * @data: buffer to send
89 * @len: length of buffer
91 * Returns 0 on success, error otherwise.
93 int xb_write(const void *data, unsigned len)
95 struct xenstore_domain_interface *intf = xen_store_interface;
96 XENSTORE_RING_IDX cons, prod;
103 rc = wait_event_interruptible(
105 (intf->req_prod - intf->req_cons) !=
110 /* Read indexes, then verify. */
111 cons = intf->req_cons;
112 prod = intf->req_prod;
113 if (!check_indexes(cons, prod)) {
114 intf->req_cons = intf->req_prod = 0;
118 dst = get_output_chunk(cons, prod, intf->req, &avail);
124 /* Must write data /after/ reading the consumer index. */
127 memcpy(dst, data, avail);
131 /* Other side must not see new producer until data is there. */
133 intf->req_prod += avail;
135 /* Implies mb(): other side will see the updated producer. */
136 notify_remote_via_evtchn(xen_store_evtchn);
142 int xb_data_to_read(void)
144 struct xenstore_domain_interface *intf = xen_store_interface;
145 return (intf->rsp_cons != intf->rsp_prod);
148 int xb_wait_for_data_to_read(void)
150 return wait_event_interruptible(xb_waitq, xb_data_to_read());
153 int xb_read(void *data, unsigned len)
155 struct xenstore_domain_interface *intf = xen_store_interface;
156 XENSTORE_RING_IDX cons, prod;
163 rc = xb_wait_for_data_to_read();
167 /* Read indexes, then verify. */
168 cons = intf->rsp_cons;
169 prod = intf->rsp_prod;
170 if (!check_indexes(cons, prod)) {
171 intf->rsp_cons = intf->rsp_prod = 0;
175 src = get_input_chunk(cons, prod, intf->rsp, &avail);
181 /* Must read data /after/ reading the producer index. */
184 memcpy(data, src, avail);
188 /* Other side must not see free space until we've copied out */
190 intf->rsp_cons += avail;
192 pr_debug("Finished read of %i bytes (%i to go)\n", avail, len);
194 /* Implies mb(): other side will see the updated consumer. */
195 notify_remote_via_evtchn(xen_store_evtchn);
202 * xb_init_comms - Set up interrupt handler off store event channel.
204 int xb_init_comms(void)
206 struct xenstore_domain_interface *intf = xen_store_interface;
208 if (intf->req_prod != intf->req_cons)
209 printk(KERN_ERR "XENBUS request ring is not quiescent "
210 "(%08x:%08x)!\n", intf->req_cons, intf->req_prod);
212 if (intf->rsp_prod != intf->rsp_cons) {
213 printk(KERN_WARNING "XENBUS response ring is not quiescent "
214 "(%08x:%08x): fixing up\n",
215 intf->rsp_cons, intf->rsp_prod);
216 intf->rsp_cons = intf->rsp_prod;
220 /* Already have an irq; assume we're resuming */
221 rebind_evtchn_irq(xen_store_evtchn, xenbus_irq);
224 err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting,
225 0, "xenbus", &xb_waitq);
227 printk(KERN_ERR "XENBUS request irq failed %i\n", err);