xen: add block device backend driver. (Gerd Hoffmann)

This patch adds a block device backend driver to qemu.  It is a pure
userspace implemention using the gntdev interface.  It uses "qdisk" as
backend name in xenstore so it doesn't interfere with the other existing
backends (blkback aka "vbd" and tapdisk aka "tap").

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7223 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 779 insertions, 0 deletions

diff --git a/hw/xen_disk.c b/hw/xen_disk.c
new file mode 100644
index 0000000..527f84b
--- /dev/null
+++ b/hw/xen_disk.c
@@ -0,0 +1,779 @@
+/*
+ *  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, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#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;
+    LIST_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 */
+    LIST_HEAD(inflight_head, ioreq) inflight;
+    LIST_HEAD(finished_head, ioreq) finished;
+    LIST_HEAD(freelist_head, ioreq) freelist;
+    int                 requests_total;
+    int                 requests_inflight;
+    int                 requests_finished;
+
+    /* qemu block driver */
+    int                 index;
+    BlockDriverState    *bs;
+    QEMUBH              *bh;
+};
+
+/* ------------------------------------------------------------- */
+
+static struct ioreq *ioreq_start(struct XenBlkDev *blkdev)
+{
+    struct ioreq *ioreq = NULL;
+
+    if (LIST_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 = LIST_FIRST(&blkdev->freelist);
+	LIST_REMOVE(ioreq, list);
+        qemu_iovec_reset(&ioreq->v);
+    }
+    LIST_INSERT_HEAD(&blkdev->inflight, ioreq, list);
+    blkdev->requests_inflight++;
+
+out:
+    return ioreq;
+}
+
+static void ioreq_finish(struct ioreq *ioreq)
+{
+    struct XenBlkDev *blkdev = ioreq->blkdev;
+
+    LIST_REMOVE(ioreq, list);
+    LIST_INSERT_HEAD(&blkdev->finished, ioreq, list);
+    blkdev->requests_inflight--;
+    blkdev->requests_finished++;
+}
+
+static void ioreq_release(struct ioreq *ioreq)
+{
+    struct XenBlkDev *blkdev = ioreq->blkdev;
+
+    LIST_REMOVE(ioreq, list);
+    memset(ioreq, 0, sizeof(*ioreq));
+    ioreq->blkdev = blkdev;
+    LIST_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 */
+	if (BLKIF_OP_READ != ioreq->req.operation && blkdev->mode[0] != 'w') {
+	    xen_be_printf(&blkdev->xendev, 0, "error: write req for ro device\n");
+	    goto err;
+	}
+	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;
+    };
+
+    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, blkdev->rings.x86_32.rsp_prod_pvt);
+	break;
+    case BLKIF_PROTOCOL_X86_64:
+	dst = RING_GET_RESPONSE(&blkdev->rings.x86_64, blkdev->rings.x86_64.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 (!LIST_EMPTY(&blkdev->finished)) {
+        ioreq = LIST_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, rc));
+	break;
+    case BLKIF_PROTOCOL_X86_64:
+	blkif_get_x86_64_req(&ioreq->req, RING_GET_REQUEST(&blkdev->rings.x86_64, 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);
+
+    LIST_INIT(&blkdev->inflight);
+    LIST_INIT(&blkdev->finished);
+    LIST_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 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 */
+    blkdev->index = (blkdev->xendev.dev - 202 * 256) / 16;
+    blkdev->index = drive_get_index(IF_XEN, 0, blkdev->index);
+    if (blkdev->index == -1) {
+        /* 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_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 = drives_table[blkdev->index].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, 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, 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->index == -1) {
+            /* 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 (!LIST_EMPTY(&blkdev->freelist)) {
+	ioreq = LIST_FIRST(&blkdev->freelist);
+        LIST_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,
+};