--- /dev/null
+/******************************************************************************
+ * 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 <asm/hypervisor.h>
+#include <xen/evtchn.h>
+#include <linux/wait.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/err.h>
+#include <xen/xenbus.h>
+#include "xenbus_comms.h"
+
+static int xenbus_irq;
+
+extern void xenbus_probe(void *);
+extern int xenstored_ready;
+static DECLARE_WORK(probe_work, xenbus_probe, NULL);
+
+DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
+
+static inline struct xenstore_domain_interface *xenstore_domain_interface(void)
+{
+ return mfn_to_virt(xen_start_info->store_mfn);
+}
+
+static irqreturn_t wake_waiting(int irq, void *unused, struct pt_regs *regs)
+{
+ 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);
+}
+
+int xb_write(const void *data, unsigned len)
+{
+ struct xenstore_domain_interface *intf = xenstore_domain_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;
+ mb();
+ 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;
+
+ memcpy(dst, data, avail);
+ data += avail;
+ len -= avail;
+
+ /* Other side must not see new header until data is there. */
+ wmb();
+ intf->req_prod += avail;
+
+ /* This implies mb() before other side sees interrupt. */
+ notify_remote_via_evtchn(xen_start_info->store_evtchn);
+ }
+
+ return 0;
+}
+
+int xb_read(void *data, unsigned len)
+{
+ struct xenstore_domain_interface *intf = xenstore_domain_interface();
+ XENSTORE_RING_IDX cons, prod;
+ int rc;
+
+ while (len != 0) {
+ unsigned int avail;
+ const char *src;
+
+ rc = wait_event_interruptible(
+ xb_waitq,
+ intf->rsp_cons != intf->rsp_prod);
+ if (rc < 0)
+ return rc;
+
+ /* Read indexes, then verify. */
+ cons = intf->rsp_cons;
+ prod = intf->rsp_prod;
+ mb();
+ 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;
+
+ /* We must read header before we read data. */
+ 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(): they will see new header. */
+ notify_remote_via_evtchn(xen_start_info->store_evtchn);
+ }
+
+ return 0;
+}
+
+/* Set up interrupt handler off store event channel. */
+int xb_init_comms(void)
+{
+ int err;
+
+ if (xenbus_irq)
+ unbind_from_irqhandler(xenbus_irq, &xb_waitq);
+
+ err = bind_evtchn_to_irqhandler(
+ xen_start_info->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;
+}
git://git.onelab.eu / linux-2.6.git / blobdiff