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 <asm/hypervisor.h>
34 #include <xen/evtchn.h>
35 #include <linux/wait.h>
36 #include <linux/interrupt.h>
37 #include <linux/sched.h>
38 #include <linux/err.h>
39 #include <xen/xenbus.h>
40 #include "xenbus_comms.h"
42 static int xenbus_irq;
44 extern void xenbus_probe(void *);
45 extern int xenstored_ready;
46 static DECLARE_WORK(probe_work, xenbus_probe, NULL);
48 DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
50 static irqreturn_t wake_waiting(int irq, void *unused, struct pt_regs *regs)
52 if (unlikely(xenstored_ready == 0)) {
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);
86 int xb_write(const void *data, unsigned len)
88 struct xenstore_domain_interface *intf = xen_store_interface;
89 XENSTORE_RING_IDX cons, prod;
96 rc = wait_event_interruptible(
98 (intf->req_prod - intf->req_cons) !=
103 /* Read indexes, then verify. */
104 cons = intf->req_cons;
105 prod = intf->req_prod;
107 if (!check_indexes(cons, prod)) {
108 intf->req_cons = intf->req_prod = 0;
112 dst = get_output_chunk(cons, prod, intf->req, &avail);
118 memcpy(dst, data, avail);
122 /* Other side must not see new header until data is there. */
124 intf->req_prod += avail;
126 /* This implies mb() before other side sees interrupt. */
127 notify_remote_via_evtchn(xen_store_evtchn);
133 int xb_read(void *data, unsigned len)
135 struct xenstore_domain_interface *intf = xen_store_interface;
136 XENSTORE_RING_IDX cons, prod;
143 rc = wait_event_interruptible(
145 intf->rsp_cons != intf->rsp_prod);
149 /* Read indexes, then verify. */
150 cons = intf->rsp_cons;
151 prod = intf->rsp_prod;
153 if (!check_indexes(cons, prod)) {
154 intf->rsp_cons = intf->rsp_prod = 0;
158 src = get_input_chunk(cons, prod, intf->rsp, &avail);
164 /* We must read header before we read data. */
167 memcpy(data, src, avail);
171 /* Other side must not see free space until we've copied out */
173 intf->rsp_cons += avail;
175 pr_debug("Finished read of %i bytes (%i to go)\n", avail, len);
177 /* Implies mb(): they will see new header. */
178 notify_remote_via_evtchn(xen_store_evtchn);
184 /* Set up interrupt handler off store event channel. */
185 int xb_init_comms(void)
190 unbind_from_irqhandler(xenbus_irq, &xb_waitq);
192 err = bind_evtchn_to_irqhandler(
193 xen_store_evtchn, wake_waiting,
194 0, "xenbus", &xb_waitq);
196 printk(KERN_ERR "XENBUS request irq failed %i\n", err);