hw/xen_disk.c - qemu - Git at Google

 /*
  *  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 = BDRV_O_RDONLY;
 	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,
 };
	/*
	* 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 = BDRV_O_RDONLY;
	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,
	};