sd: remove 'ssd' driver support

[unleashed/tickless.git] / usr / src / uts / common / xen / io / xenbus_xs.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 *
 * xenbus_xs.c
 *
 * This is the kernel equivalent of the "xs" library.  We don't need everything
 * and we use xenbus_comms for communication.
 *
 * Copyright (C) 2005 Rusty Russell, IBM Corporation
 *
 * This file may be 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.
 */

/*
 * NOTE: To future maintainers of the Solaris version of this file:
 * I found the Linux version of this code to be very disgusting in
 * overloading pointers and error codes into void * return values.
 * The main difference you will find is that all such usage is changed
 * to pass pointers to void* to be filled in with return values and
 * the functions return error codes.
 */

#include <sys/errno.h>
#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/uio.h>
#include <sys/mutex.h>
#include <sys/condvar.h>
#include <sys/rwlock.h>
#include <sys/disp.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/avintr.h>
#include <sys/cmn_err.h>
#include <sys/mach_mmu.h>
#include <util/sscanf.h>
#define _XSD_ERRORS_DEFINED
#ifdef XPV_HVM_DRIVER
#include <sys/xpv_support.h>
#endif
#include <sys/hypervisor.h>
#include <sys/taskq.h>
#include <sys/sdt.h>
#include <xen/sys/xenbus_impl.h>
#include <xen/sys/xenbus_comms.h>
#include <xen/sys/xendev.h>
#include <xen/public/io/xs_wire.h>

#define streq(a, b) (strcmp((a), (b)) == 0)

#define list_empty(list) (list_head(list) == NULL)

struct xs_stored_msg {
        list_node_t list;

        struct xsd_sockmsg hdr;

        union {
                /* Queued replies. */
                struct {
                        char *body;
                } reply;

                /* Queued watch events. */
                struct {
                        struct xenbus_watch *handle;
                        char **vec;
                        unsigned int vec_size;
                } watch;
        } un;
};

static struct xs_handle {
        /* A list of replies. Currently only one will ever be outstanding. */
        list_t reply_list;
        kmutex_t reply_lock;
        kcondvar_t reply_cv;

        /* One request at a time. */
        kmutex_t request_mutex;

        /* Protect transactions against save/restore. */
        krwlock_t suspend_lock;
} xs_state;

static int last_req_id;

/*
 * List of clients wanting a xenstore up notification, and a lock to protect it
 */
static boolean_t xenstore_up;
static list_t notify_list;
static kmutex_t notify_list_lock;
static taskq_t *xenbus_taskq;

/* List of registered watches, and a lock to protect it. */
static list_t watches;
static kmutex_t watches_lock;

/* List of pending watch callback events, and a lock to protect it. */
static list_t watch_events;
static kmutex_t watch_events_lock;

/*
 * Details of the xenwatch callback kernel thread. The thread waits on the
 * watch_events_cv for work to do (queued on watch_events list). When it
 * wakes up it acquires the xenwatch_mutex before reading the list and
 * carrying out work.
 */
static kmutex_t xenwatch_mutex;
static kcondvar_t watch_events_cv;

static int process_msg(void);

static int
get_error(const char *errorstring)
{
        unsigned int i;

        for (i = 0; !streq(errorstring, xsd_errors[i].errstring); i++) {
                if (i == (sizeof (xsd_errors) / sizeof (xsd_errors[0])) - 1) {
                        cmn_err(CE_WARN,
                            "XENBUS xen store gave: unknown error %s",
                            errorstring);
                        return (EINVAL);
                }
        }
        return (xsd_errors[i].errnum);
}

/*
 * Read a synchronous reply from xenstore.  Since we can return early before
 * reading a relevant reply, we discard any messages not matching the request
 * ID.  Caller must free returned message on success.
 */
static int
read_reply(struct xsd_sockmsg *req_hdr, struct xs_stored_msg **reply)
{
        extern int do_polled_io;

        mutex_enter(&xs_state.reply_lock);

        for (;;) {
                while (list_empty(&xs_state.reply_list)) {
                        if (interrupts_unleashed && !do_polled_io) {
                                if (cv_wait_sig(&xs_state.reply_cv,
                                    &xs_state.reply_lock) == 0) {
                                        mutex_exit(&xs_state.reply_lock);
                                        *reply = NULL;
                                        return (EINTR);
                                }
                        } else { /* polled mode needed for early probes */
                                mutex_exit(&xs_state.reply_lock);
                                (void) HYPERVISOR_yield();
                                (void) process_msg();
                                mutex_enter(&xs_state.reply_lock);
                        }
                }

                *reply = list_head(&xs_state.reply_list);
                list_remove(&xs_state.reply_list, *reply);

                if ((*reply)->hdr.req_id == req_hdr->req_id)
                        break;
        }

        mutex_exit(&xs_state.reply_lock);
        return (0);
}

/* Emergency write. */
void
xenbus_debug_write(const char *str, unsigned int count)
{
        struct xsd_sockmsg msg = { 0 };

        msg.type = XS_DEBUG;
        msg.len = sizeof ("print") + count + 1;

        mutex_enter(&xs_state.request_mutex);
        (void) xb_write(&msg, sizeof (msg));
        (void) xb_write("print", sizeof ("print"));
        (void) xb_write(str, count);
        (void) xb_write("", 1);
        mutex_exit(&xs_state.request_mutex);
}

/*
 * This is pretty unpleasant.  First off, there's the horrible logic around
 * suspend_lock and transactions.  Also, we can be interrupted either before we
 * write a message, or before we receive a reply.  A client that wants to
 * survive this can't know which case happened.  Luckily all clients don't care
 * about signals currently, and the alternative (a hard wait on a userspace
 * daemon) isn't exactly preferable.  Caller must free 'reply' on success.
 */
int
xenbus_dev_request_and_reply(struct xsd_sockmsg *msg, void **reply)
{
        struct xsd_sockmsg req_msg = *msg;
        struct xs_stored_msg *reply_msg = NULL;
        int err;

        if (req_msg.type == XS_TRANSACTION_START)
                rw_enter(&xs_state.suspend_lock, RW_READER);

        mutex_enter(&xs_state.request_mutex);

        msg->req_id = last_req_id++;

        err = xb_write(msg, sizeof (*msg) + msg->len);
        if (err) {
                if (req_msg.type == XS_TRANSACTION_START)
                        rw_exit(&xs_state.suspend_lock);
                msg->type = XS_ERROR;
                *reply = NULL;
                goto out;
        }

        err = read_reply(msg, &reply_msg);

        if (err) {
                if (msg->type == XS_TRANSACTION_START)
                        rw_exit(&xs_state.suspend_lock);
                *reply = NULL;
                goto out;
        }

        *reply = reply_msg->un.reply.body;
        *msg = reply_msg->hdr;

        if (reply_msg->hdr.type == XS_TRANSACTION_END)
                rw_exit(&xs_state.suspend_lock);

out:
        if (reply_msg != NULL)
                kmem_free(reply_msg, sizeof (*reply_msg));

        mutex_exit(&xs_state.request_mutex);
        return (err);
}

/*
 * Send message to xs, return errcode, rval filled in with pointer
 * to kmem_alloc'ed reply.
 */
static int
xs_talkv(xenbus_transaction_t t,
                    enum xsd_sockmsg_type type,
                    const iovec_t *iovec,
                    unsigned int num_vecs,
                    void **rval,
                    unsigned int *len)
{
        struct xsd_sockmsg msg;
        struct xs_stored_msg *reply_msg;
        char *reply;
        unsigned int i;
        int err;

        msg.tx_id = (uint32_t)(unsigned long)t;
        msg.type = type;
        msg.len = 0;
        for (i = 0; i < num_vecs; i++)
                msg.len += iovec[i].iov_len;

        mutex_enter(&xs_state.request_mutex);

        msg.req_id = last_req_id++;

        err = xb_write(&msg, sizeof (msg));
        if (err) {
                mutex_exit(&xs_state.request_mutex);
                return (err);
        }

        for (i = 0; i < num_vecs; i++) {
                err = xb_write(iovec[i].iov_base, iovec[i].iov_len);
                if (err) {
                        mutex_exit(&xs_state.request_mutex);
                        return (err);
                }
        }

        err = read_reply(&msg, &reply_msg);

        mutex_exit(&xs_state.request_mutex);

        if (err)
                return (err);

        reply = reply_msg->un.reply.body;

        if (reply_msg->hdr.type == XS_ERROR) {
                err = get_error(reply);
                kmem_free(reply, reply_msg->hdr.len + 1);
                goto out;
        }

        if (len != NULL)
                *len = reply_msg->hdr.len + 1;

        ASSERT(reply_msg->hdr.type == type);

        if (rval != NULL)
                *rval = reply;
        else
                kmem_free(reply, reply_msg->hdr.len + 1);

out:
        kmem_free(reply_msg, sizeof (*reply_msg));
        return (err);
}

/* Simplified version of xs_talkv: single message. */
static int
xs_single(xenbus_transaction_t t,
                        enum xsd_sockmsg_type type,
                        const char *string, void **ret,
                        unsigned int *len)
{
        iovec_t iovec;

        iovec.iov_base = (char *)string;
        iovec.iov_len = strlen(string) + 1;
        return (xs_talkv(t, type, &iovec, 1, ret, len));
}

static unsigned int
count_strings(const char *strings, unsigned int len)
{
        unsigned int num;
        const char *p;

        for (p = strings, num = 0; p < strings + len; p += strlen(p) + 1)
                num++;

        return (num);
}

/* Return the path to dir with /name appended. Buffer must be kmem_free()'ed */
static char *
join(const char *dir, const char *name)
{
        char *buffer;
        size_t slashlen;

        slashlen = streq(name, "") ? 0 : 1;
        buffer = kmem_alloc(strlen(dir) + slashlen + strlen(name) + 1,
            KM_SLEEP);

        (void) strcpy(buffer, dir);
        if (slashlen != 0) {
                (void) strcat(buffer, "/");
                (void) strcat(buffer, name);
        }
        return (buffer);
}

static char **
split(char *strings, unsigned int len, unsigned int *num)
{
        char *p, **ret;

        /* Count the strings. */
        if ((*num = count_strings(strings, len - 1)) == 0)
                return (NULL);

        /* Transfer to one big alloc for easy freeing. */
        ret = kmem_alloc(*num * sizeof (char *) + (len - 1), KM_SLEEP);
        (void) memcpy(&ret[*num], strings, len - 1);
        kmem_free(strings, len);

        strings = (char *)&ret[*num];
        for (p = strings, *num = 0; p < strings + (len - 1);
            p += strlen(p) + 1) {
                ret[(*num)++] = p;
        }

        return (ret);
}

char **
xenbus_directory(xenbus_transaction_t t,
                        const char *dir, const char *node, unsigned int *num)
{
        char *strings, *path;
        unsigned int len;
        int err;

        path = join(dir, node);
        err = xs_single(t, XS_DIRECTORY, path, (void **)&strings, &len);
        kmem_free(path, strlen(path) + 1);
        if (err != 0 || strings == NULL) {
                /* sigh, we lose error code info here */
                *num = 0;
                return (NULL);
        }

        return (split(strings, len, num));
}

/* Check if a path exists. */
boolean_t
xenbus_exists(const char *dir, const char *node)
{
        void    *p;
        uint_t  n;

        if (xenbus_read(XBT_NULL, dir, node, &p, &n) != 0)
                return (B_FALSE);
        kmem_free(p, n);
        return (B_TRUE);
}

/* Check if a directory path exists. */
boolean_t
xenbus_exists_dir(const char *dir, const char *node)
{
        char **d;
        unsigned int dir_n;
        int i, len;

        d = xenbus_directory(XBT_NULL, dir, node, &dir_n);
        if (d == NULL)
                return (B_FALSE);
        for (i = 0, len = 0; i < dir_n; i++)
                len += strlen(d[i]) + 1 + sizeof (char *);
        kmem_free(d, len);
        return (B_TRUE);
}

/*
 * Get the value of a single file.
 * Returns a kmem_alloced value in retp: call kmem_free() on it after use.
 * len indicates length in bytes.
 */
int
xenbus_read(xenbus_transaction_t t,
            const char *dir, const char *node, void **retp, unsigned int *len)
{
        char *path;
        int err;

        path = join(dir, node);
        err = xs_single(t, XS_READ, path, retp, len);
        kmem_free(path, strlen(path) + 1);
        return (err);
}

int
xenbus_read_str(const char *dir, const char *node, char **retp)
{
        uint_t  n;
        int     err;
        char    *str;

        /*
         * Since we access the xenbus value immediatly we can't be
         * part of a transaction.
         */
        if ((err = xenbus_read(XBT_NULL, dir, node, (void **)&str, &n)) != 0)
                return (err);
        ASSERT((str != NULL) && (n > 0));

        /*
         * Why bother with this?  Because xenbus is truly annoying in the
         * fact that when it returns a string, it doesn't guarantee that
         * the memory that holds the string is of size strlen() + 1.
         * This forces callers to keep track of the size of the memory
         * containing the string.  Ugh.  We'll work around this by
         * re-allocate strings to always be of size strlen() + 1.
         */
        *retp = strdup(str);
        kmem_free(str, n);
        return (0);
}

/*
 * Write the value of a single file.
 * Returns err on failure.
 */
int
xenbus_write(xenbus_transaction_t t,
                const char *dir, const char *node, const char *string)
{
        char *path;
        iovec_t iovec[2];
        int ret;

        path = join(dir, node);

        iovec[0].iov_base = (void *)path;
        iovec[0].iov_len = strlen(path) + 1;
        iovec[1].iov_base = (void *)string;
        iovec[1].iov_len = strlen(string);

        ret = xs_talkv(t, XS_WRITE, iovec, 2, NULL, NULL);
        kmem_free(path, iovec[0].iov_len);
        return (ret);
}

/* Create a new directory. */
int
xenbus_mkdir(xenbus_transaction_t t, const char *dir, const char *node)
{
        char *path;
        int ret;

        path = join(dir, node);
        ret = xs_single(t, XS_MKDIR, path, NULL, NULL);
        kmem_free(path, strlen(path) + 1);
        return (ret);
}

/* Destroy a file or directory (directories must be empty). */
int
xenbus_rm(xenbus_transaction_t t, const char *dir, const char *node)
{
        char *path;
        int ret;

        path = join(dir, node);
        ret = xs_single(t, XS_RM, path, NULL, NULL);
        kmem_free(path, strlen(path) + 1);
        return (ret);
}

/*
 * Start a transaction: changes by others will not be seen during this
 * transaction, and changes will not be visible to others until end.
 */
int
xenbus_transaction_start(xenbus_transaction_t *t)
{
        void *id_str;
        unsigned long id;
        int err;
        unsigned int len;

        rw_enter(&xs_state.suspend_lock, RW_READER);

        err = xs_single(XBT_NULL, XS_TRANSACTION_START, "", &id_str, &len);
        if (err) {
                rw_exit(&xs_state.suspend_lock);
                return (err);
        }

        (void) ddi_strtoul((char *)id_str, NULL, 0, &id);
        *t = (xenbus_transaction_t)id;
        kmem_free(id_str, len);

        return (0);
}

/*
 * End a transaction.
 * If abandon is true, transaction is discarded instead of committed.
 */
int
xenbus_transaction_end(xenbus_transaction_t t, int abort)
{
        char abortstr[2];
        int err;

        if (abort)
                (void) strcpy(abortstr, "F");
        else
                (void) strcpy(abortstr, "T");

        err = xs_single(t, XS_TRANSACTION_END, abortstr, NULL, NULL);

        rw_exit(&xs_state.suspend_lock);

        return (err);
}

/*
 * Single read and scanf: returns errno or 0.  This can only handle a single
 * conversion specifier.
 */
/* SCANFLIKE4 */
int
xenbus_scanf(xenbus_transaction_t t,
                const char *dir, const char *node, const char *fmt, ...)
{
        va_list ap;
        int ret;
        char *val;
        unsigned int len;

        ret = xenbus_read(t, dir, node, (void **)&val, &len);
        if (ret)
                return (ret);

        va_start(ap, fmt);
        if (vsscanf(val, fmt, ap) != 1)
                ret = ERANGE;
        va_end(ap);
        kmem_free(val, len);
        return (ret);
}

/* Single printf and write: returns errno or 0. */
/* PRINTFLIKE4 */
int
xenbus_printf(xenbus_transaction_t t,
                const char *dir, const char *node, const char *fmt, ...)
{
        va_list ap;
        int ret;
#define PRINTF_BUFFER_SIZE 4096
        char *printf_buffer;

        printf_buffer = kmem_alloc(PRINTF_BUFFER_SIZE, KM_SLEEP);

        va_start(ap, fmt);
        ret = vsnprintf(printf_buffer, PRINTF_BUFFER_SIZE, fmt, ap);
        va_end(ap);

        ASSERT(ret <= PRINTF_BUFFER_SIZE-1);
        ret = xenbus_write(t, dir, node, printf_buffer);

        kmem_free(printf_buffer, PRINTF_BUFFER_SIZE);

        return (ret);
}


/* Takes tuples of names, scanf-style args, and void **, NULL terminated. */
int
xenbus_gather(xenbus_transaction_t t, const char *dir, ...)
{
        va_list ap;
        const char *name;
        int ret = 0;
        unsigned int len;

        va_start(ap, dir);
        while (ret == 0 && (name = va_arg(ap, char *)) != NULL) {
                const char *fmt = va_arg(ap, char *);
                void *result = va_arg(ap, void *);
                char *p;

                ret = xenbus_read(t, dir, name, (void **)&p, &len);
                if (ret)
                        break;
                if (fmt) {
                        ASSERT(result != NULL);
                        if (sscanf(p, fmt, result) != 1)
                                ret = EINVAL;
                        kmem_free(p, len);
                } else
                        *(char **)result = p;
        }
        va_end(ap);
        return (ret);
}

static int
xs_watch(const char *path, const char *token)
{
        iovec_t iov[2];

        iov[0].iov_base = (void *)path;
        iov[0].iov_len = strlen(path) + 1;
        iov[1].iov_base = (void *)token;
        iov[1].iov_len = strlen(token) + 1;

        return (xs_talkv(XBT_NULL, XS_WATCH, iov, 2, NULL, NULL));
}

static int
xs_unwatch(const char *path, const char *token)
{
        iovec_t iov[2];

        iov[0].iov_base = (char *)path;
        iov[0].iov_len = strlen(path) + 1;
        iov[1].iov_base = (char *)token;
        iov[1].iov_len = strlen(token) + 1;

        return (xs_talkv(XBT_NULL, XS_UNWATCH, iov, 2, NULL, NULL));
}

static struct xenbus_watch *
find_watch(const char *token)
{
        struct xenbus_watch *i, *cmp;

        (void) ddi_strtoul(token, NULL, 16, (unsigned long *)&cmp);

        for (i = list_head(&watches); i != NULL; i = list_next(&watches, i))
                if (i == cmp)
                        break;

        return (i);
}

/* Register a xenstore state notify callback */
int
xs_register_xenbus_callback(void (*callback)(int))
{
        struct xenbus_notify *xbn, *xnp;

        xbn = kmem_alloc(sizeof (struct xenbus_notify), KM_SLEEP);
        xbn->notify_func = callback;
        mutex_enter(&notify_list_lock);
        /*
         * Make sure not already on the list
         */
        xnp = list_head(&notify_list);
        for (; xnp != NULL; xnp = list_next(&notify_list, xnp)) {
                if (xnp->notify_func == callback) {
                        kmem_free(xbn, sizeof (struct xenbus_notify));
                        mutex_exit(&notify_list_lock);
                        return (EEXIST);
                }
        }
        xnp = xbn;
        list_insert_tail(&notify_list, xbn);
done:
        if (xenstore_up)
                xnp->notify_func(XENSTORE_UP);
        mutex_exit(&notify_list_lock);
        return (0);
}

/*
 * Notify clients of xenstore state
 */
static void
do_notify_callbacks(void *arg)
{
        struct xenbus_notify *xnp;

        mutex_enter(&notify_list_lock);
        xnp = list_head(&notify_list);
        for (; xnp != NULL; xnp = list_next(&notify_list, xnp)) {
                xnp->notify_func((int)((uintptr_t)arg));
        }
        mutex_exit(&notify_list_lock);
}

void
xs_notify_xenstore_up(void)
{
        xenstore_up = B_TRUE;
        (void) taskq_dispatch(xenbus_taskq, do_notify_callbacks,
            (void *)XENSTORE_UP, 0);
}

void
xs_notify_xenstore_down(void)
{
        xenstore_up = B_FALSE;
        (void) taskq_dispatch(xenbus_taskq, do_notify_callbacks,
            (void *)XENSTORE_DOWN, 0);
}

/* Register callback to watch this node. */
int
register_xenbus_watch(struct xenbus_watch *watch)
{
        /* Pointer in ascii is the token. */
        char token[sizeof (watch) * 2 + 1];
        int err;

        ASSERT(xenstore_up);
        (void) snprintf(token, sizeof (token), "%lX", (long)watch);

        rw_enter(&xs_state.suspend_lock, RW_READER);

        mutex_enter(&watches_lock);
        /*
         * May be re-registering a watch if xenstore daemon was restarted
         */
        if (find_watch(token) == NULL)
                list_insert_tail(&watches, watch);
        mutex_exit(&watches_lock);

        DTRACE_XPV3(xenbus__register__watch, const char *, watch->node,
            uintptr_t, watch->callback, struct xenbus_watch *, watch);

        err = xs_watch(watch->node, token);

        /* Ignore errors due to multiple registration. */
        if ((err != 0) && (err != EEXIST)) {
                mutex_enter(&watches_lock);
                list_remove(&watches, watch);
                mutex_exit(&watches_lock);
        }

        rw_exit(&xs_state.suspend_lock);

        return (err);
}

static void
free_stored_msg(struct xs_stored_msg *msg)
{
        int i, len = 0;

        for (i = 0; i < msg->un.watch.vec_size; i++)
                len += strlen(msg->un.watch.vec[i]) + 1 + sizeof (char *);
        kmem_free(msg->un.watch.vec, len);
        kmem_free(msg, sizeof (*msg));
}

void
unregister_xenbus_watch(struct xenbus_watch *watch)
{
        struct xs_stored_msg *msg;
        char token[sizeof (watch) * 2 + 1];
        int err;

        (void) snprintf(token, sizeof (token), "%lX", (long)watch);

        rw_enter(&xs_state.suspend_lock, RW_READER);

        mutex_enter(&watches_lock);
        ASSERT(find_watch(token));
        list_remove(&watches, watch);
        mutex_exit(&watches_lock);

        DTRACE_XPV3(xenbus__unregister__watch, const char *, watch->node,
            uintptr_t, watch->callback, struct xenbus_watch *, watch);

        err = xs_unwatch(watch->node, token);
        if (err)
                cmn_err(CE_WARN, "XENBUS Failed to release watch %s: %d",
                    watch->node, err);

        rw_exit(&xs_state.suspend_lock);

        /* Cancel pending watch events. */
        mutex_enter(&watch_events_lock);
        msg = list_head(&watch_events);

        while (msg != NULL) {
                struct xs_stored_msg *tmp = list_next(&watch_events, msg);
                if (msg->un.watch.handle == watch) {
                        list_remove(&watch_events, msg);
                        free_stored_msg(msg);
                }
                msg = tmp;
        }

        mutex_exit(&watch_events_lock);

        /* Flush any currently-executing callback, unless we are it. :-) */
        if (mutex_owner(&xenwatch_mutex) != curthread) {
                mutex_enter(&xenwatch_mutex);
                mutex_exit(&xenwatch_mutex);
        }
}

void
xenbus_suspend(void)
{
        rw_enter(&xs_state.suspend_lock, RW_WRITER);
        mutex_enter(&xs_state.request_mutex);

        xb_suspend();
}

void
xenbus_resume(void)
{
        struct xenbus_watch *watch;
        char token[sizeof (watch) * 2 + 1];

        mutex_exit(&xs_state.request_mutex);

        xb_init();
        xb_setup_intr();

        /* No need for watches_lock: the suspend_lock is sufficient. */
        for (watch = list_head(&watches); watch != NULL;
            watch = list_next(&watches, watch)) {
                (void) snprintf(token, sizeof (token), "%lX", (long)watch);
                (void) xs_watch(watch->node, token);
        }

        rw_exit(&xs_state.suspend_lock);
}

static void
xenwatch_thread(void)
{
        struct xs_stored_msg *msg;
        struct xenbus_watch *watch;

        for (;;) {
                mutex_enter(&watch_events_lock);
                while (list_empty(&watch_events))
                        cv_wait(&watch_events_cv, &watch_events_lock);
                msg = list_head(&watch_events);
                ASSERT(msg != NULL);
                list_remove(&watch_events, msg);
                watch = msg->un.watch.handle;
                mutex_exit(&watch_events_lock);

                mutex_enter(&xenwatch_mutex);

                DTRACE_XPV4(xenbus__fire__watch,
                    const char *, watch->node,
                    uintptr_t, watch->callback,
                    struct xenbus_watch *, watch,
                    const char *, msg->un.watch.vec[XS_WATCH_PATH]);

                watch->callback(watch, (const char **)msg->un.watch.vec,
                    msg->un.watch.vec_size);

                free_stored_msg(msg);
                mutex_exit(&xenwatch_mutex);
        }
}

static int
process_msg(void)
{
        struct xs_stored_msg *msg;
        char *body;
        int err, mlen;

        msg = kmem_alloc(sizeof (*msg), KM_SLEEP);

        err = xb_read(&msg->hdr, sizeof (msg->hdr));
        if (err) {
                kmem_free(msg, sizeof (*msg));
                return (err);
        }

        mlen = msg->hdr.len + 1;
        body = kmem_alloc(mlen, KM_SLEEP);

        err = xb_read(body, msg->hdr.len);
        if (err) {
                kmem_free(body, mlen);
                kmem_free(msg, sizeof (*msg));
                return (err);
        }

        body[mlen - 1] = '\0';

        if (msg->hdr.type == XS_WATCH_EVENT) {
                const char *token;
                msg->un.watch.vec = split(body, msg->hdr.len + 1,
                    &msg->un.watch.vec_size);
                if (msg->un.watch.vec == NULL) {
                        kmem_free(msg, sizeof (*msg));
                        return (EIO);
                }

                mutex_enter(&watches_lock);
                token = msg->un.watch.vec[XS_WATCH_TOKEN];
                if ((msg->un.watch.handle = find_watch(token)) != NULL) {
                        mutex_enter(&watch_events_lock);

                        DTRACE_XPV4(xenbus__enqueue__watch,
                            const char *, msg->un.watch.handle->node,
                            uintptr_t, msg->un.watch.handle->callback,
                            struct xenbus_watch *, msg->un.watch.handle,
                            const char *, msg->un.watch.vec[XS_WATCH_PATH]);

                        list_insert_tail(&watch_events, msg);
                        cv_broadcast(&watch_events_cv);
                        mutex_exit(&watch_events_lock);
                } else {
                        free_stored_msg(msg);
                }
                mutex_exit(&watches_lock);
        } else {
                msg->un.reply.body = body;
                mutex_enter(&xs_state.reply_lock);
                list_insert_tail(&xs_state.reply_list, msg);
                mutex_exit(&xs_state.reply_lock);
                cv_signal(&xs_state.reply_cv);
        }

        return (0);
}

static void
xenbus_thread(void)
{
        int err;

        /*
         * We have to wait for interrupts to be ready, so we don't clash
         * with the polled-IO code in read_reply().
         */
        while (!interrupts_unleashed)
                delay(10);

        for (;;) {
                err = process_msg();
                if (err)
                        cmn_err(CE_WARN, "XENBUS error %d while reading "
                            "message", err);
        }
}

/*
 * When setting up xenbus, dom0 and domU have to take different paths, which
 * makes this code a little confusing. For dom0:
 *
 * xs_early_init - mutex init only
 * xs_dom0_init - called on xenbus dev attach: set up our xenstore page and
 * event channel; start xenbus threads for responding to interrupts.
 *
 * And for domU:
 *
 * xs_early_init - mutex init; set up our xenstore page and event channel
 * xs_domu_init - installation of IRQ handler; start xenbus threads.
 *
 * We need an early init on domU so we can use xenbus in polled mode to
 * discover devices, VCPUs etc.
 *
 * On resume, we use xb_init() and xb_setup_intr() to restore xenbus to a
 * working state.
 */

void
xs_early_init(void)
{
        list_create(&xs_state.reply_list, sizeof (struct xs_stored_msg),
            offsetof(struct xs_stored_msg, list));
        list_create(&watch_events, sizeof (struct xs_stored_msg),
            offsetof(struct xs_stored_msg, list));
        list_create(&watches, sizeof (struct xenbus_watch),
            offsetof(struct xenbus_watch, list));
        list_create(&notify_list, sizeof (struct xenbus_notify),
            offsetof(struct xenbus_notify, list));
        mutex_init(&xs_state.reply_lock, NULL, MUTEX_DEFAULT, NULL);
        mutex_init(&xs_state.request_mutex, NULL, MUTEX_DEFAULT, NULL);
        mutex_init(&notify_list_lock, NULL, MUTEX_DEFAULT, NULL);
        rw_init(&xs_state.suspend_lock, NULL, RW_DEFAULT, NULL);
        cv_init(&xs_state.reply_cv, NULL, CV_DEFAULT, NULL);

        if (DOMAIN_IS_INITDOMAIN(xen_info))
                return;

        xb_init();
        xenstore_up = B_TRUE;
}

static void
xs_thread_init(void)
{
        (void) thread_create(NULL, 0, xenwatch_thread, NULL, 0, &p0,
            TS_RUN, minclsyspri);
        (void) thread_create(NULL, 0, xenbus_thread, NULL, 0, &p0,
            TS_RUN, minclsyspri);
        xenbus_taskq = taskq_create("xenbus_taskq", 1,
            maxclsyspri - 1, 1, 1, TASKQ_PREPOPULATE);
        ASSERT(xenbus_taskq != NULL);
}

void
xs_domu_init(void)
{
        if (DOMAIN_IS_INITDOMAIN(xen_info))
                return;

        /*
         * Add interrupt handler for xenbus now, must wait till after
         * psm module is loaded.  All use of xenbus is in polled mode
         * until xs_init is called since it is what kicks off the xs
         * server threads.
         */
        xs_thread_init();
        xb_setup_intr();
}


void
xs_dom0_init(void)
{
        static boolean_t initialized = B_FALSE;

        ASSERT(DOMAIN_IS_INITDOMAIN(xen_info));

        /*
         * The xenbus driver might be re-attaching.
         */
        if (initialized)
                return;

        xb_init();
        xs_thread_init();
        xb_setup_intr();

        initialized = B_TRUE;
}