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/>.

 *

 *  Contributions after 2012-01-13 are licensed under the terms of the

 *  GNU GPL, version 2 or (at your option) any later version.

 */

#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 "hw/hw.h"

#include "hw/xen/xen_backend.h"

#include "xen_blkif.h"

#include "sysemu/blockdev.h"

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

static int batch_maps   = 0;

static int max_requests = 32;

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

#define BLOCK_SIZE  512

#define IOCB_COUNT  (BLKIF_MAX_SEGMENTS_PER_REQUEST + 2)

struct PersistentGrant {

    void *page;

    struct XenBlkDev *blkdev;

};

typedef struct PersistentGrant PersistentGrant;

struct ioreq {

    blkif_request_t     req;

    int16_t             status;

    /* parsed request */

    off_t               start;

    QEMUIOVector        v;

    int                 presync;

    int                 postsync;

    uint8_t             mapped;

    /* 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;

    int                 num_unmap;

    /* aio status */

    int                 aio_inflight;

    int                 aio_errors;

    struct XenBlkDev    *blkdev;

    QLIST_ENTRY(ioreq)   list;

    BlockAcctCookie     acct;

};

struct XenBlkDev {

    struct XenDevice    xendev;  /* must be first */

    char                *params;

    char                *mode;

    char                *type;

    char                *dev;

    char                *devtype;

    bool                directiosafe;

    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;

    /* Persistent grants extension */

    gboolean            feature_persistent;

    GTree               *persistent_gnts;

    unsigned int        persistent_gnt_count;

    unsigned int        max_grants;

    /* qemu block driver */

    DriveInfo           *dinfo;

    BlockDriverState    *bs;

    QEMUBH              *bh;

};

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

static void ioreq_reset(struct ioreq *ioreq)

{

    memset(&ioreq->req, 0, sizeof(ioreq->req));

    ioreq->status = 0;

    ioreq->start = 0;

    ioreq->presync = 0;

    ioreq->postsync = 0;

    ioreq->mapped = 0;

    memset(ioreq->domids, 0, sizeof(ioreq->domids));

    memset(ioreq->refs, 0, sizeof(ioreq->refs));

    ioreq->prot = 0;

    memset(ioreq->page, 0, sizeof(ioreq->page));

    ioreq->pages = NULL;

    ioreq->aio_inflight = 0;

    ioreq->aio_errors = 0;

    ioreq->blkdev = NULL;

    memset(&ioreq->list, 0, sizeof(ioreq->list));

    memset(&ioreq->acct, 0, sizeof(ioreq->acct));

    qemu_iovec_reset(&ioreq->v);

}

static gint int_cmp(gconstpointer a, gconstpointer b, gpointer user_data)

{

    uint ua = GPOINTER_TO_UINT(a);

    uint ub = GPOINTER_TO_UINT(b);

    return (ua > ub) - (ua < ub);

}

static void destroy_grant(gpointer pgnt)

{

    PersistentGrant *grant = pgnt;

    XenGnttab gnt = grant->blkdev->xendev.gnttabdev;

    if (xc_gnttab_munmap(gnt, grant->page, 1) != 0) {

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

                      "xc_gnttab_munmap failed: %s\n",

                      strerror(errno));

    }

    grant->blkdev->persistent_gnt_count--;

    xen_be_printf(&grant->blkdev->xendev, 3,

                  "unmapped grant %p\n", grant->page);

    g_free(grant);

}

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 = g_malloc0(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);

    }

    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, bool finish)

{

    struct XenBlkDev *blkdev = ioreq->blkdev;

    QLIST_REMOVE(ioreq, list);

    ioreq_reset(ioreq);

    ioreq->blkdev = blkdev;

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

    if (finish) {

        blkdev->requests_finished--;

    } else {

        blkdev->requests_inflight--;

    }

}

/*

 * 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_FLUSH_DISKCACHE:

        ioreq->presync = 1;

        if (!ioreq->req.nr_segments) {

            return 0;

        }

        /* fall through */

    case BLKIF_OP_WRITE:

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

        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)

{

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

    int i;

    if (ioreq->num_unmap == 0 || ioreq->mapped == 0) {

        return;

    }

    if (batch_maps) {

        if (!ioreq->pages) {

            return;

        }

        if (xc_gnttab_munmap(gnt, ioreq->pages, ioreq->num_unmap) != 0) {

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

                          strerror(errno));

        }

        ioreq->blkdev->cnt_map -= ioreq->num_unmap;

        ioreq->pages = NULL;

    } else {

        for (i = 0; i < ioreq->num_unmap; 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;

        }

    }

    ioreq->mapped = 0;

}

static int ioreq_map(struct ioreq *ioreq)

{

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

    uint32_t domids[BLKIF_MAX_SEGMENTS_PER_REQUEST];

    uint32_t refs[BLKIF_MAX_SEGMENTS_PER_REQUEST];

    void *page[BLKIF_MAX_SEGMENTS_PER_REQUEST];

    int i, j, new_maps = 0;

    PersistentGrant *grant;

    /* domids and refs variables will contain the information necessary

     * to map the grants that are needed to fulfill this request.

     *

     * After mapping the needed grants, the page array will contain the

     * memory address of each granted page in the order specified in ioreq

     * (disregarding if it's a persistent grant or not).

     */

    if (ioreq->v.niov == 0 || ioreq->mapped == 1) {

        return 0;

    }

    if (ioreq->blkdev->feature_persistent) {

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

            grant = g_tree_lookup(ioreq->blkdev->persistent_gnts,

                                    GUINT_TO_POINTER(ioreq->refs[i]));

            if (grant != NULL) {

                page[i] = grant->page;

                xen_be_printf(&ioreq->blkdev->xendev, 3,

                              "using persistent-grant %" PRIu32 "\n",

                              ioreq->refs[i]);

            } else {

                    /* Add the grant to the list of grants that

                     * should be mapped

                     */

                    domids[new_maps] = ioreq->domids[i];

                    refs[new_maps] = ioreq->refs[i];

                    page[i] = NULL;

                    new_maps++;

            }

        }

        /* Set the protection to RW, since grants may be reused later

         * with a different protection than the one needed for this request

         */

        ioreq->prot = PROT_WRITE | PROT_READ;

    } else {

        /* All grants in the request should be mapped */

        memcpy(refs, ioreq->refs, sizeof(refs));

        memcpy(domids, ioreq->domids, sizeof(domids));

        memset(page, 0, sizeof(page));

        new_maps = ioreq->v.niov;

    }

    if (batch_maps && new_maps) {

        ioreq->pages = xc_gnttab_map_grant_refs

            (gnt, new_maps, domids, refs, ioreq->prot);

        if (ioreq->pages == NULL) {

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

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

                          new_maps, strerror(errno), ioreq->blkdev->cnt_map);

            return -1;

        }

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

            if (page[i] == NULL) {

                page[i] = ioreq->pages + (j++) * XC_PAGE_SIZE;

            }

        }

        ioreq->blkdev->cnt_map += new_maps;

    } else if (new_maps)  {

        for (i = 0; i < new_maps; i++) {

            ioreq->page[i] = xc_gnttab_map_grant_ref

                (gnt, domids[i], 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",

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

                ioreq_unmap(ioreq);

                return -1;

            }

            ioreq->blkdev->cnt_map++;

        }

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

            if (page[i] == NULL) {

                page[i] = ioreq->page[j++];

            }

        }

    }

    if (ioreq->blkdev->feature_persistent) {

        while ((ioreq->blkdev->persistent_gnt_count < ioreq->blkdev->max_grants)

              && new_maps) {

            /* Go through the list of newly mapped grants and add as many

             * as possible to the list of persistently mapped grants.

             *

             * Since we start at the end of ioreq->page(s), we only need

             * to decrease new_maps to prevent this granted pages from

             * being unmapped in ioreq_unmap.

             */

            grant = g_malloc0(sizeof(*grant));

            new_maps--;

            if (batch_maps) {

                grant->page = ioreq->pages + (new_maps) * XC_PAGE_SIZE;

            } else {

                grant->page = ioreq->page[new_maps];

            }

            grant->blkdev = ioreq->blkdev;

            xen_be_printf(&ioreq->blkdev->xendev, 3,

                          "adding grant %" PRIu32 " page: %p\n",

                          refs[new_maps], grant->page);

            g_tree_insert(ioreq->blkdev->persistent_gnts,

                          GUINT_TO_POINTER(refs[new_maps]),

                          grant);

            ioreq->blkdev->persistent_gnt_count++;

        }

    }

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

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

    }

    ioreq->mapped = 1;

    ioreq->num_unmap = new_maps;

    return 0;

}

static int ioreq_runio_qemu_aio(struct ioreq *ioreq);

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->presync) {

        ioreq->presync = 0;

        ioreq_runio_qemu_aio(ioreq);

        return;

    }

    if (ioreq->aio_inflight > 0) {

        return;

    }

    if (ioreq->postsync) {

        ioreq->postsync = 0;

        ioreq->aio_inflight++;

        bdrv_aio_flush(ioreq->blkdev->bs, qemu_aio_complete, ioreq);

        return;

    }

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

    ioreq_unmap(ioreq);

    ioreq_finish(ioreq);

    bdrv_acct_done(ioreq->blkdev->bs, &ioreq->acct);

    qemu_bh_schedule(ioreq->blkdev->bh);

}

static int ioreq_runio_qemu_aio(struct ioreq *ioreq)

{

    struct XenBlkDev *blkdev = ioreq->blkdev;

    if (ioreq->req.nr_segments && ioreq_map(ioreq) == -1) {

        goto err_no_map;

    }

    ioreq->aio_inflight++;

    if (ioreq->presync) {

        bdrv_aio_flush(ioreq->blkdev->bs, qemu_aio_complete, ioreq);

        return 0;

    }

    switch (ioreq->req.operation) {

    case BLKIF_OP_READ:

        bdrv_acct_start(blkdev->bs, &ioreq->acct, ioreq->v.size, BDRV_ACCT_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_FLUSH_DISKCACHE:

        if (!ioreq->req.nr_segments) {

            break;

        }

        bdrv_acct_start(blkdev->bs, &ioreq->acct, ioreq->v.size, BDRV_ACCT_WRITE);

        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;

    }

    qemu_aio_complete(ioreq, 0);

    return 0;

err:

    ioreq_unmap(ioreq);

err_no_map:

    ioreq_finish(ioreq);

    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, true);

    }

    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'. */

    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, false);

            continue;

        }

        ioreq_runio_qemu_aio(ioreq);

    }

    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);

}

/*

 * We need to account for the grant allocations requiring contiguous

 * chunks; the worst case number would be

 *     max_req * max_seg + (max_req - 1) * (max_seg - 1) + 1,

 * but in order to keep things simple just use

 *     2 * max_req * max_seg.

 */

#define MAX_GRANTS(max_req, max_seg) (2 * (max_req) * (max_seg))

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;

    }

    if (xc_gnttab_set_max_grants(xendev->gnttabdev,

            MAX_GRANTS(max_requests, BLKIF_MAX_SEGMENTS_PER_REQUEST)) < 0) {

        xen_be_printf(xendev, 0, "xc_gnttab_set_max_grants failed: %s\n",

                      strerror(errno));

    }

}

static int blk_init(struct XenDevice *xendev)

{

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

    int info = 0;

    char *directiosafe = NULL;

    /* read xenstore entries */

    if (blkdev->params == NULL) {

        char *h = NULL;

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

        if (blkdev->params != NULL) {

            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 (!strcmp("aio", blkdev->fileproto)) {

        blkdev->fileproto = "raw";

    }

    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");

    }

    directiosafe = xenstore_read_be_str(&blkdev->xendev, "direct-io-safe");

    blkdev->directiosafe = (directiosafe && atoi(directiosafe));

    /* do we have all we need? */

    if (blkdev->params == NULL ||

        blkdev->mode == NULL   ||

        blkdev->type == NULL   ||

        blkdev->dev == NULL) {

        goto out_error;

    }

    /* read-only ? */

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

        info  |= VDISK_READONLY;

    }

    /* cdrom ? */

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

        info  |= VDISK_CDROM;

    }

    blkdev->file_blk  = BLOCK_SIZE;

    /* fill info

     * blk_connect supplies sector-size and sectors

     */

    xenstore_write_be_int(&blkdev->xendev, "feature-flush-cache", 1);

    xenstore_write_be_int(&blkdev->xendev, "feature-persistent", 1);

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

    g_free(directiosafe);

    return 0;

out_error:

    g_free(blkdev->params);

    blkdev->params = NULL;

    g_free(blkdev->mode);

    blkdev->mode = NULL;

    g_free(blkdev->type);

    blkdev->type = NULL;

    g_free(blkdev->dev);

    blkdev->dev = NULL;

    g_free(blkdev->devtype);

    blkdev->devtype = NULL;

    g_free(directiosafe);

    blkdev->directiosafe = false;

    return -1;

}

static int blk_connect(struct XenDevice *xendev)

{

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

    int pers, index, qflags;

    bool readonly = true;

    /* read-only ? */

    if (blkdev->directiosafe) {

        qflags = BDRV_O_NOCACHE | BDRV_O_NATIVE_AIO;

    } else {

        qflags = BDRV_O_CACHE_WB;

    }

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

        qflags |= BDRV_O_RDWR;

        readonly = false;

    }

    /* 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) {

            Error *local_err = NULL;

            BlockDriver *drv = bdrv_find_whitelisted_format(blkdev->fileproto,

                                                           readonly);

            if (bdrv_open(blkdev->bs,

                          blkdev->filename, NULL, qflags, drv, &local_err) != 0)

            {

                xen_be_printf(&blkdev->xendev, 0, "error: %s\n",

                              error_get_pretty(local_err));

                error_free(local_err);

                bdrv_unref(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->bs is not create by us, we get a reference

         * so we can bdrv_unref() unconditionally */

        bdrv_ref(blkdev->bs);

    }

    bdrv_attach_dev_nofail(blkdev->bs, blkdev);

    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),

                      bdrv_get_format_name(blkdev->bs) ?: "-");

        blkdev->file_size = 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 in number of sector size and number of sectors */

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

    xenstore_write_be_int64(&blkdev->xendev, "sectors",

                            blkdev->file_size / blkdev->file_blk);

    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;

    }

    if (xenstore_read_fe_int(&blkdev->xendev, "feature-persistent", &pers)) {

        blkdev->feature_persistent = FALSE;

    } else {

        blkdev->feature_persistent = !!pers;

    }

    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++;