diff options
Diffstat (limited to 'drivers/xen/xenbus/xenbus_comms.c')
| -rw-r--r-- | drivers/xen/xenbus/xenbus_comms.c | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/drivers/xen/xenbus/xenbus_comms.c b/drivers/xen/xenbus/xenbus_comms.c new file mode 100644 index 000000000..fdb0f339d --- /dev/null +++ b/drivers/xen/xenbus/xenbus_comms.c @@ -0,0 +1,243 @@ +/****************************************************************************** + * 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. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#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) + pr_err("request ring is not quiescent (%08x:%08x)!\n", + intf->req_cons, intf->req_prod); + + if (intf->rsp_prod != intf->rsp_cons) { + pr_warn("response ring is not quiescent (%08x:%08x): fixing up\n", + intf->rsp_cons, intf->rsp_prod); + /* breaks kdump */ + if (!reset_devices) + 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) { + pr_err("request irq failed %i\n", err); + return err; + } + + xenbus_irq = err; + } + + return 0; +} + +void xb_deinit_comms(void) +{ + unbind_from_irqhandler(xenbus_irq, &xb_waitq); + xenbus_irq = 0; +} |