/******************************************************************************
* xenbus_comms.c
*
* Low level code to talks to Xen Store: ringbuffer and event channel.
*
* Copyright (C) 2005 Rusty Russell, IBM Corporation
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation; or, when distributed
* separately from the Linux kernel or incorporated into other
* software packages, subject to the following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this source file (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify,
* merge, publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include <linux/wait.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/err.h>
#include <xen/xenbus.h>
#include <asm/xen/hypervisor.h>
#include <xen/events.h>
#include <xen/page.h>
#include "xenbus_comms.h"
static int xenbus_irq;
static DECLARE_WORK(probe_work, xenbus_probe);
static DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
static irqreturn_t wake_waiting(int irq, void *unused)
{
if (unlikely(xenstored_ready == 0)) {
xenstored_ready = 1;
schedule_work(&probe_work);
}
wake_up(&xb_waitq);
return IRQ_HANDLED;
}
static int check_indexes(XENSTORE_RING_IDX cons, XENSTORE_RING_IDX prod)
{
return ((prod - cons) <= XENSTORE_RING_SIZE);
}
static void *get_output_chunk(XENSTORE_RING_IDX cons,
XENSTORE_RING_IDX prod,
char *buf, uint32_t *len)
{
*len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod);
if ((XENSTORE_RING_SIZE - (prod - cons)) < *len)
*len = XENSTORE_RING_SIZE - (prod - cons);
return buf + MASK_XENSTORE_IDX(prod);
}
static const void *get_input_chunk(XENSTORE_RING_IDX cons,
XENSTORE_RING_IDX prod,
const char *buf, uint32_t *len)
{
*len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(cons);
if ((prod - cons) < *len)
*len = prod - cons;
return buf + MASK_XENSTORE_IDX(cons);
}
/**
* xb_write - low level write
* @data: buffer to send
* @len: length of buffer
*
* Returns 0 on success, error otherwise.
*/
int xb_write(const void *data, unsigned len)
{
struct xenstore_domain_interface *intf = xen_store_interface;
XENSTORE_RING_IDX cons, prod;
int rc;
while (len != 0) {
void *dst;
unsigned int avail;
rc = wait_event_interruptible(
xb_waitq,
(intf->req_prod - intf->req_cons) !=
XENSTORE_RING_SIZE);
if (rc < 0)
return rc;
/* Read indexes, then verify. */
cons = intf->req_cons;
prod = intf->req_prod;
if (!check_indexes(cons, prod)) {
intf->req_cons = intf->req_prod = 0;
return -EIO;
}
dst = get_output_chunk(cons, prod, intf->req, &avail);
if (avail == 0)
continue;
if (avail > len)
avail = len;
/* Must write data /after/ reading the consumer index. */
mb();
memcpy(dst, data, avail);
data += avail;
len -= avail;
/* Other side must not see new producer until data is there. */
wmb();
intf->req_prod += avail;
/* Implies mb(): other side will see the updated producer. */
notify_remote_via_evtchn(xen_store_evtchn);
}
return 0;
}
int xb_data_to_read(void)
{
struct xenstore_domain_interface *intf = xen_store_interface;
return (intf->rsp_cons != intf->rsp_prod);
}
int xb_wait_for_data_to_read(void)
{
return wait_event_interruptible(xb_waitq, xb_data_to_read());
}
int xb_read(void *data, unsigned len)
{
struct xenstore_domain_interface *intf = xen_store_interface;
XENSTORE_RING_IDX cons, prod;
int rc;
while (len != 0) {
unsigned int avail;
const char *src;
rc = xb_wait_for_data_to_read();
if (rc < 0)
return rc;
/* Read indexes, then verify. */
cons = intf->rsp_cons;
prod = intf->rsp_prod;
if (!check_indexes(cons, prod)) {
intf->rsp_cons = intf->rsp_prod = 0;
return -EIO;
}
src = get_input_chunk(cons, prod, intf->rsp, &avail);
if (avail == 0)
continue;
if (avail > len)
avail = len;
/* Must read data /after/ reading the producer index. */
rmb();
memcpy(data, src, avail);
data += avail;
len -= avail;
/* Other side must not see free space until we've copied out */
mb();
intf->rsp_cons += avail;
pr_debug("Finished read of %i bytes (%i to go)\n", avail, len);
/* Implies mb(): other side will see the updated consumer. */
notify_remote_via_evtchn(xen_store_evtchn);
}
return 0;
}
/**
* xb_init_comms - Set up interrupt handler off store event channel.
*/
int xb_init_comms(void)
{
struct xenstore_domain_interface *intf = xen_store_interface;
if (intf->req_prod != intf->req_cons)
printk(KERN_ERR "XENBUS request ring is not quiescent "
"(%08x:%08x)!\n", intf->req_cons, intf->req_prod);
if (intf->rsp_prod != intf->rsp_cons) {
printk(KERN_WARNING "XENBUS response ring is not quiescent "
"(%08x:%08x): fixing up\n",
intf->rsp_cons, intf->rsp_prod);
intf->rsp_cons = intf->rsp_prod;
}
if (xenbus_irq) {
/* Already have an irq; assume we're resuming */
rebind_evtchn_irq(xen_store_evtchn, xenbus_irq);
} else {
int err;
err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting,
0, "xenbus", &xb_waitq);
if (err <= 0) {
printk(KERN_ERR "XENBUS request irq failed %i\n", err);
return err;
}
xenbus_irq = err;
}
return 0;
}
