/****************************************************************************** * 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 #include #include #include #include #include #include #include #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; }