Archipelago » qemu

/*

 *  xen paravirt block device backend

 *

 *  (c) Gerd Hoffmann <kraxel@redhat.com>

 *

 *  This program is free software; you can redistribute it and/or modify

 *  it under the terms of the GNU General Public License as published by

 *  the Free Software Foundation; under version 2 of the License.

 *

 *  This program is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *  GNU General Public License for more details.

 *

 *  You should have received a copy of the GNU General Public License along

 *  with this program; if not, see <http://www.gnu.org/licenses/>.

 */

#include <stdio.h>

#include <stdlib.h>

#include <stdarg.h>

#include <string.h>

#include <unistd.h>

#include <signal.h>

#include <inttypes.h>

#include <time.h>

#include <fcntl.h>

#include <errno.h>

#include <sys/ioctl.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <sys/mman.h>

#include <sys/uio.h>

#include <xs.h>

#include <xenctrl.h>

#include <xen/io/xenbus.h>

#include "hw.h"

#include "block_int.h"

#include "qemu-char.h"

#include "xen_blkif.h"

#include "xen_backend.h"

/* ------------------------------------------------------------- */

static int syncwrite    = 0;

static int batch_maps   = 0;

static int max_requests = 32;

static int use_aio      = 1;

/* ------------------------------------------------------------- */

#define BLOCK_SIZE  512

#define IOCB_COUNT  (BLKIF_MAX_SEGMENTS_PER_REQUEST + 2)

struct ioreq {

    blkif_request_t     req;

    int16_t             status;

    /* parsed request */

    off_t               start;

    QEMUIOVector        v;

    int                 presync;

    int                 postsync;

    /* grant mapping */

    uint32_t            domids[BLKIF_MAX_SEGMENTS_PER_REQUEST];

    uint32_t            refs[BLKIF_MAX_SEGMENTS_PER_REQUEST];

    int                 prot;

    void                *page[BLKIF_MAX_SEGMENTS_PER_REQUEST];

    void                *pages;

    /* aio status */

    int                 aio_inflight;

    int                 aio_errors;

    struct XenBlkDev    *blkdev;

    QLIST_ENTRY(ioreq)   list;

};

struct XenBlkDev {

    struct XenDevice    xendev;  /* must be first */

    char                *params;

    char                *mode;

    char                *type;

    char                *dev;

    char                *devtype;

    const char          *fileproto;

    const char          *filename;

    int                 ring_ref;

    void                *sring;

    int64_t             file_blk;

    int64_t             file_size;

    int                 protocol;

    blkif_back_rings_t  rings;

    int                 more_work;

    int                 cnt_map;

    /* request lists */

    QLIST_HEAD(inflight_head, ioreq) inflight;

    QLIST_HEAD(finished_head, ioreq) finished;

    QLIST_HEAD(freelist_head, ioreq) freelist;

    int                 requests_total;

    int                 requests_inflight;

    int                 requests_finished;

    /* qemu block driver */

    DriveInfo           *dinfo;

    BlockDriverState    *bs;

    QEMUBH              *bh;

};

/* ------------------------------------------------------------- */

static struct ioreq *ioreq_start(struct XenBlkDev *blkdev)

{

    struct ioreq *ioreq = NULL;

    if (QLIST_EMPTY(&blkdev->freelist)) {

        if (blkdev->requests_total >= max_requests)

            goto out;

        /* allocate new struct */

        ioreq = qemu_mallocz(sizeof(*ioreq));

        ioreq->blkdev = blkdev;

        blkdev->requests_total++;

        qemu_iovec_init(&ioreq->v, BLKIF_MAX_SEGMENTS_PER_REQUEST);

    } else {

        /* get one from freelist */

        ioreq = QLIST_FIRST(&blkdev->freelist);

        QLIST_REMOVE(ioreq, list);

        qemu_iovec_reset(&ioreq->v);

    }

    QLIST_INSERT_HEAD(&blkdev->inflight, ioreq, list);

    blkdev->requests_inflight++;

out:

    return ioreq;

}

static void ioreq_finish(struct ioreq *ioreq)

{

    struct XenBlkDev *blkdev = ioreq->blkdev;

    QLIST_REMOVE(ioreq, list);

    QLIST_INSERT_HEAD(&blkdev->finished, ioreq, list);

    blkdev->requests_inflight--;

    blkdev->requests_finished++;

}

static void ioreq_release(struct ioreq *ioreq)

{

    struct XenBlkDev *blkdev = ioreq->blkdev;

    QLIST_REMOVE(ioreq, list);

    memset(ioreq, 0, sizeof(*ioreq));

    ioreq->blkdev = blkdev;

    QLIST_INSERT_HEAD(&blkdev->freelist, ioreq, list);

    blkdev->requests_finished--;

}

/*

 * translate request into iovec + start offset

 * do sanity checks along the way

 */

static int ioreq_parse(struct ioreq *ioreq)

{

    struct XenBlkDev *blkdev = ioreq->blkdev;

    uintptr_t mem;

    size_t len;

    int i;

    xen_be_printf(&blkdev->xendev, 3,

                  "op %d, nr %d, handle %d, id %" PRId64 ", sector %" PRId64 "\n",

                  ioreq->req.operation, ioreq->req.nr_segments,

                  ioreq->req.handle, ioreq->req.id, ioreq->req.sector_number);

    switch (ioreq->req.operation) {

    case BLKIF_OP_READ:

        ioreq->prot = PROT_WRITE; /* to memory */

        break;

    case BLKIF_OP_WRITE_BARRIER:

        if (!syncwrite)

            ioreq->presync = ioreq->postsync = 1;

        /* fall through */

    case BLKIF_OP_WRITE:

        ioreq->prot = PROT_READ; /* from memory */

        if (syncwrite)

            ioreq->postsync = 1;

        break;

    default:

        xen_be_printf(&blkdev->xendev, 0, "error: unknown operation (%d)\n",

                      ioreq->req.operation);

        goto err;

    };

    if (ioreq->req.operation != BLKIF_OP_READ && blkdev->mode[0] != 'w') {

        xen_be_printf(&blkdev->xendev, 0, "error: write req for ro device\n");

        goto err;

    }

    ioreq->start = ioreq->req.sector_number * blkdev->file_blk;

    for (i = 0; i < ioreq->req.nr_segments; i++) {

        if (i == BLKIF_MAX_SEGMENTS_PER_REQUEST) {

            xen_be_printf(&blkdev->xendev, 0, "error: nr_segments too big\n");

            goto err;

        }

        if (ioreq->req.seg[i].first_sect > ioreq->req.seg[i].last_sect) {

            xen_be_printf(&blkdev->xendev, 0, "error: first > last sector\n");

            goto err;

        }

        if (ioreq->req.seg[i].last_sect * BLOCK_SIZE >= XC_PAGE_SIZE) {

            xen_be_printf(&blkdev->xendev, 0, "error: page crossing\n");

            goto err;

        }

        ioreq->domids[i] = blkdev->xendev.dom;

        ioreq->refs[i]   = ioreq->req.seg[i].gref;

        mem = ioreq->req.seg[i].first_sect * blkdev->file_blk;

        len = (ioreq->req.seg[i].last_sect - ioreq->req.seg[i].first_sect + 1) * blkdev->file_blk;

        qemu_iovec_add(&ioreq->v, (void*)mem, len);

    }

    if (ioreq->start + ioreq->v.size > blkdev->file_size) {

        xen_be_printf(&blkdev->xendev, 0, "error: access beyond end of file\n");

        goto err;

    }

    return 0;

err:

    ioreq->status = BLKIF_RSP_ERROR;

    return -1;

}

static void ioreq_unmap(struct ioreq *ioreq)

{

    int gnt = ioreq->blkdev->xendev.gnttabdev;

    int i;

    if (ioreq->v.niov == 0)

        return;

    if (batch_maps) {

        if (!ioreq->pages)

            return;

        if (xc_gnttab_munmap(gnt, ioreq->pages, ioreq->v.niov) != 0)

            xen_be_printf(&ioreq->blkdev->xendev, 0, "xc_gnttab_munmap failed: %s\n",

                          strerror(errno));

        ioreq->blkdev->cnt_map -= ioreq->v.niov;

        ioreq->pages = NULL;

    } else {

        for (i = 0; i < ioreq->v.niov; i++) {

            if (!ioreq->page[i])

                continue;

            if (xc_gnttab_munmap(gnt, ioreq->page[i], 1) != 0)

                xen_be_printf(&ioreq->blkdev->xendev, 0, "xc_gnttab_munmap failed: %s\n",

                              strerror(errno));

            ioreq->blkdev->cnt_map--;

            ioreq->page[i] = NULL;

        }

    }

}

static int ioreq_map(struct ioreq *ioreq)

{

    int gnt = ioreq->blkdev->xendev.gnttabdev;

    int i;

    if (ioreq->v.niov == 0)

        return 0;

    if (batch_maps) {

        ioreq->pages = xc_gnttab_map_grant_refs

            (gnt, ioreq->v.niov, ioreq->domids, ioreq->refs, ioreq->prot);

        if (ioreq->pages == NULL) {

            xen_be_printf(&ioreq->blkdev->xendev, 0,

                          "can't map %d grant refs (%s, %d maps)\n",

                          ioreq->v.niov, strerror(errno), ioreq->blkdev->cnt_map);

            return -1;

        }

        for (i = 0; i < ioreq->v.niov; i++)

            ioreq->v.iov[i].iov_base = ioreq->pages + i * XC_PAGE_SIZE +

                (uintptr_t)ioreq->v.iov[i].iov_base;

        ioreq->blkdev->cnt_map += ioreq->v.niov;

    } else  {

        for (i = 0; i < ioreq->v.niov; i++) {

            ioreq->page[i] = xc_gnttab_map_grant_ref

                (gnt, ioreq->domids[i], ioreq->refs[i], ioreq->prot);

            if (ioreq->page[i] == NULL) {

                xen_be_printf(&ioreq->blkdev->xendev, 0,

                              "can't map grant ref %d (%s, %d maps)\n",

                              ioreq->refs[i], strerror(errno), ioreq->blkdev->cnt_map);

                ioreq_unmap(ioreq);

                return -1;

            }

            ioreq->v.iov[i].iov_base = ioreq->page[i] + (uintptr_t)ioreq->v.iov[i].iov_base;

            ioreq->blkdev->cnt_map++;

        }

    }

    return 0;

}

static int ioreq_runio_qemu_sync(struct ioreq *ioreq)

{

    struct XenBlkDev *blkdev = ioreq->blkdev;

    int i, rc, len = 0;

    off_t pos;

    if (ioreq_map(ioreq) == -1)

        goto err;

    if (ioreq->presync)

        bdrv_flush(blkdev->bs);

    switch (ioreq->req.operation) {

    case BLKIF_OP_READ:

        pos = ioreq->start;

        for (i = 0; i < ioreq->v.niov; i++) {

            rc = bdrv_read(blkdev->bs, pos / BLOCK_SIZE,

                           ioreq->v.iov[i].iov_base,

                           ioreq->v.iov[i].iov_len / BLOCK_SIZE);

            if (rc != 0) {

                xen_be_printf(&blkdev->xendev, 0, "rd I/O error (%p, len %zd)\n",

                              ioreq->v.iov[i].iov_base,

                              ioreq->v.iov[i].iov_len);

                goto err;

            }

            len += ioreq->v.iov[i].iov_len;

            pos += ioreq->v.iov[i].iov_len;

        }

        break;

    case BLKIF_OP_WRITE:

    case BLKIF_OP_WRITE_BARRIER:

        pos = ioreq->start;

        for (i = 0; i < ioreq->v.niov; i++) {

            rc = bdrv_write(blkdev->bs, pos / BLOCK_SIZE,

                            ioreq->v.iov[i].iov_base,

                            ioreq->v.iov[i].iov_len / BLOCK_SIZE);

            if (rc != 0) {

                xen_be_printf(&blkdev->xendev, 0, "wr I/O error (%p, len %zd)\n",

                              ioreq->v.iov[i].iov_base,

                              ioreq->v.iov[i].iov_len);

                goto err;

            }

            len += ioreq->v.iov[i].iov_len;

            pos += ioreq->v.iov[i].iov_len;

        }

        break;

    default:

        /* unknown operation (shouldn't happen -- parse catches this) */

        goto err;

    }

    if (ioreq->postsync)

        bdrv_flush(blkdev->bs);

    ioreq->status = BLKIF_RSP_OKAY;

    ioreq_unmap(ioreq);

    ioreq_finish(ioreq);

    return 0;

err:

    ioreq->status = BLKIF_RSP_ERROR;

    return -1;

}

static void qemu_aio_complete(void *opaque, int ret)

{

    struct ioreq *ioreq = opaque;

    if (ret != 0) {

        xen_be_printf(&ioreq->blkdev->xendev, 0, "%s I/O error\n",

                      ioreq->req.operation == BLKIF_OP_READ ? "read" : "write");

        ioreq->aio_errors++;

    }

    ioreq->aio_inflight--;

    if (ioreq->aio_inflight > 0)

        return;

    ioreq->status = ioreq->aio_errors ? BLKIF_RSP_ERROR : BLKIF_RSP_OKAY;

    ioreq_unmap(ioreq);

    ioreq_finish(ioreq);

    qemu_bh_schedule(ioreq->blkdev->bh);

}

static int ioreq_runio_qemu_aio(struct ioreq *ioreq)

{

    struct XenBlkDev *blkdev = ioreq->blkdev;

    if (ioreq_map(ioreq) == -1)

        goto err;

    ioreq->aio_inflight++;

    if (ioreq->presync)

        bdrv_flush(blkdev->bs); /* FIXME: aio_flush() ??? */

    switch (ioreq->req.operation) {

    case BLKIF_OP_READ:

        ioreq->aio_inflight++;

        bdrv_aio_readv(blkdev->bs, ioreq->start / BLOCK_SIZE,

                       &ioreq->v, ioreq->v.size / BLOCK_SIZE,

                       qemu_aio_complete, ioreq);

        break;

    case BLKIF_OP_WRITE:

    case BLKIF_OP_WRITE_BARRIER:

        ioreq->aio_inflight++;

        bdrv_aio_writev(blkdev->bs, ioreq->start / BLOCK_SIZE,

                        &ioreq->v, ioreq->v.size / BLOCK_SIZE,

                        qemu_aio_complete, ioreq);

        break;

    default:

        /* unknown operation (shouldn't happen -- parse catches this) */

        goto err;

    }

    if (ioreq->postsync)

        bdrv_flush(blkdev->bs); /* FIXME: aio_flush() ??? */

    qemu_aio_complete(ioreq, 0);

    return 0;

err:

    ioreq->status = BLKIF_RSP_ERROR;

    return -1;

}

static int blk_send_response_one(struct ioreq *ioreq)

{

    struct XenBlkDev  *blkdev = ioreq->blkdev;

    int               send_notify   = 0;

    int               have_requests = 0;

    blkif_response_t  resp;

    void              *dst;

    resp.id        = ioreq->req.id;

    resp.operation = ioreq->req.operation;

    resp.status    = ioreq->status;

    /* Place on the response ring for the relevant domain. */

    switch (blkdev->protocol) {

    case BLKIF_PROTOCOL_NATIVE:

        dst = RING_GET_RESPONSE(&blkdev->rings.native, blkdev->rings.native.rsp_prod_pvt);

        break;

    case BLKIF_PROTOCOL_X86_32:

        dst = RING_GET_RESPONSE(&blkdev->rings.x86_32_part,

                                blkdev->rings.x86_32_part.rsp_prod_pvt);

        break;

    case BLKIF_PROTOCOL_X86_64:

        dst = RING_GET_RESPONSE(&blkdev->rings.x86_64_part,

                                blkdev->rings.x86_64_part.rsp_prod_pvt);

        break;

    default:

        dst = NULL;

    }

    memcpy(dst, &resp, sizeof(resp));

    blkdev->rings.common.rsp_prod_pvt++;

    RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blkdev->rings.common, send_notify);

    if (blkdev->rings.common.rsp_prod_pvt == blkdev->rings.common.req_cons) {

        /*

         * Tail check for pending requests. Allows frontend to avoid

         * notifications if requests are already in flight (lower

         * overheads and promotes batching).

         */

        RING_FINAL_CHECK_FOR_REQUESTS(&blkdev->rings.common, have_requests);

    } else if (RING_HAS_UNCONSUMED_REQUESTS(&blkdev->rings.common)) {

        have_requests = 1;

    }

    if (have_requests)

        blkdev->more_work++;

    return send_notify;

}

/* walk finished list, send outstanding responses, free requests */

static void blk_send_response_all(struct XenBlkDev *blkdev)

{

    struct ioreq *ioreq;

    int send_notify = 0;

    while (!QLIST_EMPTY(&blkdev->finished)) {

        ioreq = QLIST_FIRST(&blkdev->finished);

        send_notify += blk_send_response_one(ioreq);

        ioreq_release(ioreq);

    }

    if (send_notify)

        xen_be_send_notify(&blkdev->xendev);

}

static int blk_get_request(struct XenBlkDev *blkdev, struct ioreq *ioreq, RING_IDX rc)

{

    switch (blkdev->protocol) {

    case BLKIF_PROTOCOL_NATIVE:

        memcpy(&ioreq->req, RING_GET_REQUEST(&blkdev->rings.native, rc),

               sizeof(ioreq->req));

        break;

    case BLKIF_PROTOCOL_X86_32:

        blkif_get_x86_32_req(&ioreq->req,

                             RING_GET_REQUEST(&blkdev->rings.x86_32_part, rc));

        break;

    case BLKIF_PROTOCOL_X86_64:

        blkif_get_x86_64_req(&ioreq->req,

                             RING_GET_REQUEST(&blkdev->rings.x86_64_part, rc));

        break;

    }

    return 0;

}

static void blk_handle_requests(struct XenBlkDev *blkdev)

{

    RING_IDX rc, rp;

    struct ioreq *ioreq;

    blkdev->more_work = 0;

    rc = blkdev->rings.common.req_cons;

    rp = blkdev->rings.common.sring->req_prod;

    xen_rmb(); /* Ensure we see queued requests up to 'rp'. */

    if (use_aio)

        blk_send_response_all(blkdev);

    while (rc != rp) {

        /* pull request from ring */

        if (RING_REQUEST_CONS_OVERFLOW(&blkdev->rings.common, rc))

            break;

        ioreq = ioreq_start(blkdev);

        if (ioreq == NULL) {

            blkdev->more_work++;

            break;

        }

        blk_get_request(blkdev, ioreq, rc);

        blkdev->rings.common.req_cons = ++rc;

        /* parse them */

        if (ioreq_parse(ioreq) != 0) {

            if (blk_send_response_one(ioreq))

                xen_be_send_notify(&blkdev->xendev);

            ioreq_release(ioreq);

            continue;

        }

        if (use_aio) {

            /* run i/o in aio mode */

            ioreq_runio_qemu_aio(ioreq);

        } else {

            /* run i/o in sync mode */

            ioreq_runio_qemu_sync(ioreq);

        }

    }

    if (!use_aio)

        blk_send_response_all(blkdev);

    if (blkdev->more_work && blkdev->requests_inflight < max_requests)

        qemu_bh_schedule(blkdev->bh);

}

/* ------------------------------------------------------------- */

static void blk_bh(void *opaque)

{

    struct XenBlkDev *blkdev = opaque;

    blk_handle_requests(blkdev);

}

static void blk_alloc(struct XenDevice *xendev)

{

    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);

    QLIST_INIT(&blkdev->inflight);

    QLIST_INIT(&blkdev->finished);

    QLIST_INIT(&blkdev->freelist);

    blkdev->bh = qemu_bh_new(blk_bh, blkdev);

    if (xen_mode != XEN_EMULATE)

        batch_maps = 1;

}

static int blk_init(struct XenDevice *xendev)

{

    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);

    int index, mode, qflags, have_barriers, info = 0;

    char *h;

    /* read xenstore entries */

    if (blkdev->params == NULL) {

        blkdev->params = xenstore_read_be_str(&blkdev->xendev, "params");

        h = strchr(blkdev->params, ':');

        if (h != NULL) {

            blkdev->fileproto = blkdev->params;

            blkdev->filename  = h+1;

            *h = 0;

        } else {

            blkdev->fileproto = "<unset>";

            blkdev->filename  = blkdev->params;

        }

    }

    if (blkdev->mode == NULL)

        blkdev->mode = xenstore_read_be_str(&blkdev->xendev, "mode");

    if (blkdev->type == NULL)

        blkdev->type = xenstore_read_be_str(&blkdev->xendev, "type");

    if (blkdev->dev == NULL)

        blkdev->dev = xenstore_read_be_str(&blkdev->xendev, "dev");

    if (blkdev->devtype == NULL)

        blkdev->devtype = xenstore_read_be_str(&blkdev->xendev, "device-type");

    /* do we have all we need? */

    if (blkdev->params == NULL ||

        blkdev->mode == NULL   ||

        blkdev->type == NULL   ||

        blkdev->dev == NULL)

        return -1;

    /* read-only ? */

    if (strcmp(blkdev->mode, "w") == 0) {

        mode   = O_RDWR;

        qflags = BDRV_O_RDWR;

    } else {

        mode   = O_RDONLY;

        qflags = 0;

        info  |= VDISK_READONLY;

    }

    /* cdrom ? */

    if (blkdev->devtype && !strcmp(blkdev->devtype, "cdrom"))

        info  |= VDISK_CDROM;

    /* init qemu block driver */

    index = (blkdev->xendev.dev - 202 * 256) / 16;

    blkdev->dinfo = drive_get(IF_XEN, 0, index);

    if (!blkdev->dinfo) {

        /* setup via xenbus -> create new block driver instance */

        xen_be_printf(&blkdev->xendev, 2, "create new bdrv (xenbus setup)\n");

        blkdev->bs = bdrv_new(blkdev->dev);

        if (blkdev->bs) {

            if (bdrv_open2(blkdev->bs, blkdev->filename, qflags,

                           bdrv_find_whitelisted_format(blkdev->fileproto))

                != 0) {

                bdrv_delete(blkdev->bs);

                blkdev->bs = NULL;

            }

        }

        if (!blkdev->bs)

            return -1;

    } else {

        /* setup via qemu cmdline -> already setup for us */

        xen_be_printf(&blkdev->xendev, 2, "get configured bdrv (cmdline setup)\n");

        blkdev->bs = blkdev->dinfo->bdrv;

    }

    blkdev->file_blk  = BLOCK_SIZE;

    blkdev->file_size = bdrv_getlength(blkdev->bs);

    if (blkdev->file_size < 0) {

        xen_be_printf(&blkdev->xendev, 1, "bdrv_getlength: %d (%s) | drv %s\n",

                      (int)blkdev->file_size, strerror(-blkdev->file_size),

                      blkdev->bs->drv ? blkdev->bs->drv->format_name : "-");

        blkdev->file_size = 0;

    }

    have_barriers = blkdev->bs->drv && blkdev->bs->drv->bdrv_flush ? 1 : 0;

    xen_be_printf(xendev, 1, "type \"%s\", fileproto \"%s\", filename \"%s\","

                  " size %" PRId64 " (%" PRId64 " MB)\n",

                  blkdev->type, blkdev->fileproto, blkdev->filename,

                  blkdev->file_size, blkdev->file_size >> 20);

    /* fill info */

    xenstore_write_be_int(&blkdev->xendev, "feature-barrier", have_barriers);

    xenstore_write_be_int(&blkdev->xendev, "info",            info);

    xenstore_write_be_int(&blkdev->xendev, "sector-size",     blkdev->file_blk);

    xenstore_write_be_int(&blkdev->xendev, "sectors",

                          blkdev->file_size / blkdev->file_blk);

    return 0;

}

static int blk_connect(struct XenDevice *xendev)

{

    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);

    if (xenstore_read_fe_int(&blkdev->xendev, "ring-ref", &blkdev->ring_ref) == -1)

        return -1;

    if (xenstore_read_fe_int(&blkdev->xendev, "event-channel",

                             &blkdev->xendev.remote_port) == -1)

        return -1;

    blkdev->protocol = BLKIF_PROTOCOL_NATIVE;

    if (blkdev->xendev.protocol) {

        if (strcmp(blkdev->xendev.protocol, XEN_IO_PROTO_ABI_X86_32) == 0)

            blkdev->protocol = BLKIF_PROTOCOL_X86_32;

        if (strcmp(blkdev->xendev.protocol, XEN_IO_PROTO_ABI_X86_64) == 0)

            blkdev->protocol = BLKIF_PROTOCOL_X86_64;

    }

    blkdev->sring = xc_gnttab_map_grant_ref(blkdev->xendev.gnttabdev,

                                            blkdev->xendev.dom,

                                            blkdev->ring_ref,

                                            PROT_READ | PROT_WRITE);

    if (!blkdev->sring)

        return -1;

    blkdev->cnt_map++;

    switch (blkdev->protocol) {

    case BLKIF_PROTOCOL_NATIVE:

    {

        blkif_sring_t *sring_native = blkdev->sring;

        BACK_RING_INIT(&blkdev->rings.native, sring_native, XC_PAGE_SIZE);

        break;

    }

    case BLKIF_PROTOCOL_X86_32:

    {

        blkif_x86_32_sring_t *sring_x86_32 = blkdev->sring;

        BACK_RING_INIT(&blkdev->rings.x86_32_part, sring_x86_32, XC_PAGE_SIZE);

        break;

    }

    case BLKIF_PROTOCOL_X86_64:

    {

        blkif_x86_64_sring_t *sring_x86_64 = blkdev->sring;

        BACK_RING_INIT(&blkdev->rings.x86_64_part, sring_x86_64, XC_PAGE_SIZE);

        break;

    }

    }

    xen_be_bind_evtchn(&blkdev->xendev);

    xen_be_printf(&blkdev->xendev, 1, "ok: proto %s, ring-ref %d, "

                  "remote port %d, local port %d\n",

                  blkdev->xendev.protocol, blkdev->ring_ref,

                  blkdev->xendev.remote_port, blkdev->xendev.local_port);

    return 0;

}

static void blk_disconnect(struct XenDevice *xendev)

{

    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);

    if (blkdev->bs) {

        if (!blkdev->dinfo) {

            /* close/delete only if we created it ourself */

            bdrv_close(blkdev->bs);

            bdrv_delete(blkdev->bs);

        }

        blkdev->bs = NULL;

    }

    xen_be_unbind_evtchn(&blkdev->xendev);

    if (blkdev->sring) {

        xc_gnttab_munmap(blkdev->xendev.gnttabdev, blkdev->sring, 1);

        blkdev->cnt_map--;

        blkdev->sring = NULL;

    }

}

static int blk_free(struct XenDevice *xendev)

{

    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);

    struct ioreq *ioreq;

    while (!QLIST_EMPTY(&blkdev->freelist)) {

        ioreq = QLIST_FIRST(&blkdev->freelist);

        QLIST_REMOVE(ioreq, list);

        qemu_iovec_destroy(&ioreq->v);

        qemu_free(ioreq);

    }

    qemu_free(blkdev->params);

    qemu_free(blkdev->mode);

    qemu_free(blkdev->type);

    qemu_free(blkdev->dev);

    qemu_free(blkdev->devtype);

    qemu_bh_delete(blkdev->bh);

    return 0;

}

static void blk_event(struct XenDevice *xendev)

{

    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);

    qemu_bh_schedule(blkdev->bh);

}

struct XenDevOps xen_blkdev_ops = {

    .size       = sizeof(struct XenBlkDev),

    .flags      = DEVOPS_FLAG_NEED_GNTDEV,

    .alloc      = blk_alloc,

    .init       = blk_init,

    .connect    = blk_connect,

    .disconnect = blk_disconnect,

    .event      = blk_event,

    .free       = blk_free,

};