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