xen/io/xenbus_comms.c

	xenbus_comms.c revision 843e19887f64dde75055cf8842fc4db2171eff45
/*
 * 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 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 *
 * xenbus_comms.c
 *
 * Low level code to talks to Xen Store: ringbuffer and event channel.
 *
 * 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.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/types.h>
#include <vm/hat.h>
#include <vm/as.h>
#include <sys/bootinfo.h>
#include <sys/bootconf.h>
#include <vm/kboot_mmu.h>
#include <vm/seg_kmem.h>
#include <sys/hypervisor.h>
#include <sys/evtchn_impl.h>
#include <sys/condvar.h>
#include <sys/mutex.h>
#include <sys/atomic.h>
#include <sys/mman.h>
#include <sys/errno.h>
#include <sys/cmn_err.h>
#include <sys/avintr.h>
#include <xen/sys/xenbus_comms.h>
#include <xen/public/io/xs_wire.h>

static int xenbus_irq;
static ddi_umem_cookie_t xb_cookie; /* cookie for xenbus comm page */
extern caddr_t xb_addr; /* va of xenbus comm page */

static kcondvar_t xb_wait_cv;
static kmutex_t xb_wait_lock;

#define xs_domain_interface(ra) ((struct xenstore_domain_interface *)(ra))

/*ARGSUSED*/
static uint_t
xenbus_intr(void *unused)
{
    mutex_enter(&xb_wait_lock);
    cv_broadcast(&xb_wait_cv);
    mutex_exit(&xb_wait_lock);
    return (DDI_INTR_CLAIMED);
}

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 ((void *)(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 ((void *)(buf + MASK_XENSTORE_IDX(cons)));
}


int
xb_write(const void *data, unsigned len)
{
    volatile struct xenstore_domain_interface *intf =
        xs_domain_interface(xb_addr);
    XENSTORE_RING_IDX cons, prod;
    extern int do_polled_io;

    while (len != 0) {
        void *dst;
        unsigned int avail;

        mutex_enter(&xb_wait_lock);
        while ((intf->req_prod - intf->req_cons) ==
            XENSTORE_RING_SIZE) {
            if (interrupts_unleashed && !do_polled_io) {
                if (cv_wait_sig(&xb_wait_cv,
                    &xb_wait_lock) == 0) {
                    mutex_exit(&xb_wait_lock);
                    return (EINTR);
                }
            } else { /* polled mode needed for early probes */
                (void) HYPERVISOR_yield();
            }
        }
        mutex_exit(&xb_wait_lock);
        /* Read indexes, then verify. */
        cons = intf->req_cons;
        prod = intf->req_prod;
        membar_enter();
        if (!check_indexes(cons, prod))
            return (EIO);

        dst = get_output_chunk(cons, prod, (char *)intf->req, &avail);
        if (avail == 0)
            continue;
        if (avail > len)
            avail = len;

        (void) memcpy(dst, data, avail);
        data = (void *)((uintptr_t)data + avail);
        len -= avail;

        /* Other side must not see new header until data is there. */
        membar_producer();
        intf->req_prod += avail;

        /* This implies mb() before other side sees interrupt. */
        ec_notify_via_evtchn(xen_info->store_evtchn);
    }

    return (0);
}

int
xb_read(void *data, unsigned len)
{
    volatile struct xenstore_domain_interface *intf =
        xs_domain_interface(xb_addr);
    XENSTORE_RING_IDX cons, prod;
    extern int do_polled_io;

    while (len != 0) {
        unsigned int avail;
        const char *src;

        mutex_enter(&xb_wait_lock);
        while (intf->rsp_cons == intf->rsp_prod) {
            if (interrupts_unleashed && !do_polled_io) {
                if (cv_wait_sig(&xb_wait_cv,
                    &xb_wait_lock) == 0) {
                    mutex_exit(&xb_wait_lock);
                    return (EINTR);
                }
            } else { /* polled mode needed for early probes */
                (void) HYPERVISOR_yield();
            }
        }
        mutex_exit(&xb_wait_lock);
        /* Read indexes, then verify. */
        cons = intf->rsp_cons;
        prod = intf->rsp_prod;
        membar_enter();
        if (!check_indexes(cons, prod))
            return (EIO);

        src = get_input_chunk(cons, prod, (char *)intf->rsp, &avail);
        if (avail == 0)
            continue;
        if (avail > len)
            avail = len;

        /* We must read header before we read data. */
        membar_consumer();

        (void) memcpy(data, src, avail);
        data = (void *)((uintptr_t)data + avail);
        len -= avail;

        /* Other side must not see free space until we've copied out */
        membar_enter();
        intf->rsp_cons += avail;

        /* Implies mb(): they will see new header. */
        ec_notify_via_evtchn(xen_info->store_evtchn);
    }

    return (0);
}

void
xb_suspend(void)
{
    rem_avintr(NULL, IPL_XENBUS, (avfunc)xenbus_intr, xenbus_irq);
}

void
xb_setup_intr(void)
{
    xenbus_irq = ec_bind_evtchn_to_irq(xen_info->store_evtchn);
    if (!add_avintr(NULL, IPL_XENBUS, (avfunc)xenbus_intr, "xenbus",
        xenbus_irq, NULL, NULL, NULL, NULL))
        cmn_err(CE_WARN, "XENBUS add intr failed\n");
}

/*
 * Set up our xenstore page and event channel. Domain 0 needs to allocate a
 * page and event channel; other domains use what we are told.
 */
void
xb_init(void)
{
    int err;

    if (DOMAIN_IS_INITDOMAIN(xen_info)) {

        if (xb_addr != NULL)
            return;

        xb_addr = ddi_umem_alloc(PAGESIZE, DDI_UMEM_SLEEP,
            &xb_cookie);
        xen_info->store_mfn = pfn_to_mfn(hat_getpfnum(kas.a_hat,
            xb_addr));

        err = xen_alloc_unbound_evtchn(0,
            (int *)&xen_info->store_evtchn);
        ASSERT(err == 0);
    } else {
        /*
         * This is harmless on first boot, but needed for resume and
         * migrate. We use kbm_map_ma() as a shortcut instead of
         * directly using HYPERVISOR_update_va_mapping().
         */
        ASSERT(xb_addr != NULL);
        kbm_map_ma(mfn_to_ma(xen_info->store_mfn),
            (uintptr_t)xb_addr, 0);
    }

    ASSERT(xen_info->store_evtchn);
}

void *
xb_xenstore_cookie(void)
{
    ASSERT(DOMAIN_IS_INITDOMAIN(xen_info));
    return (xb_cookie);
}