Patchwork [v2,08/18] xen: duplicate xen_disk.c as basis of dataplane/xen-block.c

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Submitter Paul Durrant
Date Dec. 6, 2018, 3:08 p.m.
Message ID <1544108924-10841-9-git-send-email-paul.durrant@citrix.com>
Download mbox | patch
Permalink /patch/674229/
State New
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Comments

Paul Durrant - Dec. 6, 2018, 3:08 p.m.
The new xen-block XenDevice implementation requires the same core
dataplane as the legacy xen_disk implementation it will eventually replace.
This patch therefore copies the legacy xen_disk.c source module into a new
dataplane/xen-block.c source module as the basis for the new dataplane and
adjusts the MAINTAINERS file accordingly.

NOTE: The duplicated code is not yet built. It is simply put into place by
      this patch (just fixing style violations) such that the
      modifications that will need to be made to the code are not
      conflated with code movement, thus making review harder.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony Perard <anthony.perard@citrix.com>
---
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
---
 MAINTAINERS                    |    1 +
 hw/block/dataplane/xen-block.c | 1019 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 1020 insertions(+)
 create mode 100644 hw/block/dataplane/xen-block.c

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index dd728c3..ab62ad4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -404,6 +404,7 @@  F: hw/char/xen_console.c
 F: hw/display/xenfb.c
 F: hw/net/xen_nic.c
 F: hw/block/xen*
+F: hw/block/dataplane/xen*
 F: hw/xen/
 F: hw/xenpv/
 F: hw/i386/xen/
diff --git a/hw/block/dataplane/xen-block.c b/hw/block/dataplane/xen-block.c
new file mode 100644
index 0000000..9fae505
--- /dev/null
+++ b/hw/block/dataplane/xen-block.c
@@ -0,0 +1,1019 @@ 
+/*
+ *  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 "qemu/osdep.h"
+#include "qemu/units.h"
+#include <sys/ioctl.h>
+#include <sys/uio.h>
+
+#include "hw/hw.h"
+#include "hw/xen/xen_backend.h"
+#include "xen_blkif.h"
+#include "sysemu/blockdev.h"
+#include "sysemu/iothread.h"
+#include "sysemu/block-backend.h"
+#include "qapi/error.h"
+#include "qapi/qmp/qdict.h"
+#include "qapi/qmp/qstring.h"
+#include "trace.h"
+
+/* ------------------------------------------------------------- */
+
+#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;
+    void                *buf;
+    size_t              size;
+    int                 presync;
+
+    /* aio status */
+    int                 aio_inflight;
+    int                 aio_errors;
+
+    struct XenBlkDev    *blkdev;
+    QLIST_ENTRY(ioreq)   list;
+    BlockAcctCookie     acct;
+};
+
+#define MAX_RING_PAGE_ORDER 4
+
+struct XenBlkDev {
+    struct XenLegacyDevice    xendev;  /* must be first */
+    char                *params;
+    char                *mode;
+    char                *type;
+    char                *dev;
+    char                *devtype;
+    bool                directiosafe;
+    const char          *fileproto;
+    const char          *filename;
+    unsigned int        ring_ref[1 << MAX_RING_PAGE_ORDER];
+    unsigned int        nr_ring_ref;
+    void                *sring;
+    int64_t             file_blk;
+    int64_t             file_size;
+    int                 protocol;
+    blkif_back_rings_t  rings;
+    int                 more_work;
+
+    /* 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;
+    unsigned int        max_requests;
+
+    gboolean            feature_discard;
+
+    /* qemu block driver */
+    DriveInfo           *dinfo;
+    BlockBackend        *blk;
+    QEMUBH              *bh;
+
+    IOThread            *iothread;
+    AioContext          *ctx;
+};
+
+/* ------------------------------------------------------------- */
+
+static void ioreq_reset(struct ioreq *ioreq)
+{
+    memset(&ioreq->req, 0, sizeof(ioreq->req));
+    ioreq->status = 0;
+    ioreq->start = 0;
+    ioreq->buf = NULL;
+    ioreq->size = 0;
+    ioreq->presync = 0;
+
+    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 struct ioreq *ioreq_start(struct XenBlkDev *blkdev)
+{
+    struct ioreq *ioreq = NULL;
+
+    if (QLIST_EMPTY(&blkdev->freelist)) {
+        if (blkdev->requests_total >= blkdev->max_requests) {
+            goto out;
+        }
+        /* allocate new struct */
+        ioreq = g_malloc0(sizeof(*ioreq));
+        ioreq->blkdev = blkdev;
+        blkdev->requests_total++;
+        qemu_iovec_init(&ioreq->v, 1);
+    } 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;
+    struct XenLegacyDevice *xendev = &blkdev->xendev;
+    size_t len;
+    int i;
+
+    xen_pv_printf(
+        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:
+        break;
+    case BLKIF_OP_FLUSH_DISKCACHE:
+        ioreq->presync = 1;
+        if (!ioreq->req.nr_segments) {
+            return 0;
+        }
+        /* fall through */
+    case BLKIF_OP_WRITE:
+        break;
+    case BLKIF_OP_DISCARD:
+        return 0;
+    default:
+        xen_pv_printf(xendev, 0, "error: unknown operation (%d)\n",
+                      ioreq->req.operation);
+        goto err;
+    };
+
+    if (ioreq->req.operation != BLKIF_OP_READ && blkdev->mode[0] != 'w') {
+        xen_pv_printf(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_pv_printf(xendev, 0, "error: nr_segments too big\n");
+            goto err;
+        }
+        if (ioreq->req.seg[i].first_sect > ioreq->req.seg[i].last_sect) {
+            xen_pv_printf(xendev, 0, "error: first > last sector\n");
+            goto err;
+        }
+        if (ioreq->req.seg[i].last_sect * BLOCK_SIZE >= XC_PAGE_SIZE) {
+            xen_pv_printf(xendev, 0, "error: page crossing\n");
+            goto err;
+        }
+
+        len = (ioreq->req.seg[i].last_sect -
+               ioreq->req.seg[i].first_sect + 1) * blkdev->file_blk;
+        ioreq->size += len;
+    }
+    if (ioreq->start + ioreq->size > blkdev->file_size) {
+        xen_pv_printf(xendev, 0, "error: access beyond end of file\n");
+        goto err;
+    }
+    return 0;
+
+err:
+    ioreq->status = BLKIF_RSP_ERROR;
+    return -1;
+}
+
+static int ioreq_grant_copy(struct ioreq *ioreq)
+{
+    struct XenBlkDev *blkdev = ioreq->blkdev;
+    struct XenLegacyDevice *xendev = &blkdev->xendev;
+    XenGrantCopySegment segs[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+    int i, count, rc;
+    int64_t file_blk = blkdev->file_blk;
+    bool to_domain = (ioreq->req.operation == BLKIF_OP_READ);
+    void *virt = ioreq->buf;
+
+    if (ioreq->req.nr_segments == 0) {
+        return 0;
+    }
+
+    count = ioreq->req.nr_segments;
+
+    for (i = 0; i < count; i++) {
+        if (to_domain) {
+            segs[i].dest.foreign.ref = ioreq->req.seg[i].gref;
+            segs[i].dest.foreign.offset = ioreq->req.seg[i].first_sect *
+                file_blk;
+            segs[i].source.virt = virt;
+        } else {
+            segs[i].source.foreign.ref = ioreq->req.seg[i].gref;
+            segs[i].source.foreign.offset = ioreq->req.seg[i].first_sect *
+                file_blk;
+            segs[i].dest.virt = virt;
+        }
+        segs[i].len = (ioreq->req.seg[i].last_sect
+                       - ioreq->req.seg[i].first_sect + 1) * file_blk;
+        virt += segs[i].len;
+    }
+
+    rc = xen_be_copy_grant_refs(xendev, to_domain, segs, count);
+
+    if (rc) {
+        xen_pv_printf(xendev, 0,
+                      "failed to copy data %d\n", rc);
+        ioreq->aio_errors++;
+        return -1;
+    }
+
+    return rc;
+}
+
+static int ioreq_runio_qemu_aio(struct ioreq *ioreq);
+
+static void qemu_aio_complete(void *opaque, int ret)
+{
+    struct ioreq *ioreq = opaque;
+    struct XenBlkDev *blkdev = ioreq->blkdev;
+    struct XenLegacyDevice *xendev = &blkdev->xendev;
+
+    aio_context_acquire(blkdev->ctx);
+
+    if (ret != 0) {
+        xen_pv_printf(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);
+        goto done;
+    }
+    if (ioreq->aio_inflight > 0) {
+        goto done;
+    }
+
+    switch (ioreq->req.operation) {
+    case BLKIF_OP_READ:
+        /* in case of failure ioreq->aio_errors is increased */
+        if (ret == 0) {
+            ioreq_grant_copy(ioreq);
+        }
+        qemu_vfree(ioreq->buf);
+        break;
+    case BLKIF_OP_WRITE:
+    case BLKIF_OP_FLUSH_DISKCACHE:
+        if (!ioreq->req.nr_segments) {
+            break;
+        }
+        qemu_vfree(ioreq->buf);
+        break;
+    default:
+        break;
+    }
+
+    ioreq->status = ioreq->aio_errors ? BLKIF_RSP_ERROR : BLKIF_RSP_OKAY;
+    ioreq_finish(ioreq);
+
+    switch (ioreq->req.operation) {
+    case BLKIF_OP_WRITE:
+    case BLKIF_OP_FLUSH_DISKCACHE:
+        if (!ioreq->req.nr_segments) {
+            break;
+        }
+    case BLKIF_OP_READ:
+        if (ioreq->status == BLKIF_RSP_OKAY) {
+            block_acct_done(blk_get_stats(blkdev->blk), &ioreq->acct);
+        } else {
+            block_acct_failed(blk_get_stats(blkdev->blk), &ioreq->acct);
+        }
+        break;
+    case BLKIF_OP_DISCARD:
+    default:
+        break;
+    }
+    qemu_bh_schedule(blkdev->bh);
+
+done:
+    aio_context_release(blkdev->ctx);
+}
+
+static bool blk_split_discard(struct ioreq *ioreq, blkif_sector_t sector_number,
+                              uint64_t nr_sectors)
+{
+    struct XenBlkDev *blkdev = ioreq->blkdev;
+    int64_t byte_offset;
+    int byte_chunk;
+    uint64_t byte_remaining, limit;
+    uint64_t sec_start = sector_number;
+    uint64_t sec_count = nr_sectors;
+
+    /* Wrap around, or overflowing byte limit? */
+    if (sec_start + sec_count < sec_count ||
+        sec_start + sec_count > INT64_MAX >> BDRV_SECTOR_BITS) {
+        return false;
+    }
+
+    limit = BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS;
+    byte_offset = sec_start << BDRV_SECTOR_BITS;
+    byte_remaining = sec_count << BDRV_SECTOR_BITS;
+
+    do {
+        byte_chunk = byte_remaining > limit ? limit : byte_remaining;
+        ioreq->aio_inflight++;
+        blk_aio_pdiscard(blkdev->blk, byte_offset, byte_chunk,
+                         qemu_aio_complete, ioreq);
+        byte_remaining -= byte_chunk;
+        byte_offset += byte_chunk;
+    } while (byte_remaining > 0);
+
+    return true;
+}
+
+static int ioreq_runio_qemu_aio(struct ioreq *ioreq)
+{
+    struct XenBlkDev *blkdev = ioreq->blkdev;
+
+    ioreq->buf = qemu_memalign(XC_PAGE_SIZE, ioreq->size);
+    if (ioreq->req.nr_segments &&
+        (ioreq->req.operation == BLKIF_OP_WRITE ||
+         ioreq->req.operation == BLKIF_OP_FLUSH_DISKCACHE) &&
+        ioreq_grant_copy(ioreq)) {
+        qemu_vfree(ioreq->buf);
+        goto err;
+    }
+
+    ioreq->aio_inflight++;
+    if (ioreq->presync) {
+        blk_aio_flush(ioreq->blkdev->blk, qemu_aio_complete, ioreq);
+        return 0;
+    }
+
+    switch (ioreq->req.operation) {
+    case BLKIF_OP_READ:
+        qemu_iovec_add(&ioreq->v, ioreq->buf, ioreq->size);
+        block_acct_start(blk_get_stats(blkdev->blk), &ioreq->acct,
+                         ioreq->v.size, BLOCK_ACCT_READ);
+        ioreq->aio_inflight++;
+        blk_aio_preadv(blkdev->blk, ioreq->start, &ioreq->v, 0,
+                       qemu_aio_complete, ioreq);
+        break;
+    case BLKIF_OP_WRITE:
+    case BLKIF_OP_FLUSH_DISKCACHE:
+        if (!ioreq->req.nr_segments) {
+            break;
+        }
+
+        qemu_iovec_add(&ioreq->v, ioreq->buf, ioreq->size);
+        block_acct_start(blk_get_stats(blkdev->blk), &ioreq->acct,
+                         ioreq->v.size,
+                         ioreq->req.operation == BLKIF_OP_WRITE ?
+                         BLOCK_ACCT_WRITE : BLOCK_ACCT_FLUSH);
+        ioreq->aio_inflight++;
+        blk_aio_pwritev(blkdev->blk, ioreq->start, &ioreq->v, 0,
+                        qemu_aio_complete, ioreq);
+        break;
+    case BLKIF_OP_DISCARD:
+    {
+        struct blkif_request_discard *req = (void *)&ioreq->req;
+        if (!blk_split_discard(ioreq, req->sector_number, req->nr_sectors)) {
+            goto err;
+        }
+        break;
+    }
+    default:
+        /* unknown operation (shouldn't happen -- parse catches this) */
+        goto err;
+    }
+
+    qemu_aio_complete(ioreq, 0);
+
+    return 0;
+
+err:
+    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;
+
+    /* Place on the response ring for the relevant domain. */
+    switch (blkdev->protocol) {
+    case BLKIF_PROTOCOL_NATIVE:
+        resp = (blkif_response_t *)RING_GET_RESPONSE(
+            &blkdev->rings.native,
+            blkdev->rings.native.rsp_prod_pvt);
+        break;
+    case BLKIF_PROTOCOL_X86_32:
+        resp = (blkif_response_t *)RING_GET_RESPONSE(
+            &blkdev->rings.x86_32_part,
+            blkdev->rings.x86_32_part.rsp_prod_pvt);
+        break;
+    case BLKIF_PROTOCOL_X86_64:
+        resp = (blkif_response_t *)RING_GET_RESPONSE(
+            &blkdev->rings.x86_64_part,
+            blkdev->rings.x86_64_part.rsp_prod_pvt);
+        break;
+    default:
+        return 0;
+    }
+
+    resp->id        = ioreq->req.id;
+    resp->operation = ioreq->req.operation;
+    resp->status    = ioreq->status;
+
+    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_pv_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;
+    }
+    /* Prevent the compiler from accessing the on-ring fields instead. */
+    barrier();
+    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) {
+
+            switch (ioreq->req.operation) {
+            case BLKIF_OP_READ:
+                block_acct_invalid(blk_get_stats(blkdev->blk),
+                                   BLOCK_ACCT_READ);
+                break;
+            case BLKIF_OP_WRITE:
+                block_acct_invalid(blk_get_stats(blkdev->blk),
+                                   BLOCK_ACCT_WRITE);
+                break;
+            case BLKIF_OP_FLUSH_DISKCACHE:
+                block_acct_invalid(blk_get_stats(blkdev->blk),
+                                   BLOCK_ACCT_FLUSH);
+            default:
+                break;
+            };
+
+            if (blk_send_response_one(ioreq)) {
+                xen_pv_send_notify(&blkdev->xendev);
+            }
+            ioreq_release(ioreq, false);
+            continue;
+        }
+
+        ioreq_runio_qemu_aio(ioreq);
+    }
+
+    if (blkdev->more_work && blkdev->requests_inflight < blkdev->max_requests) {
+        qemu_bh_schedule(blkdev->bh);
+    }
+}
+
+/* ------------------------------------------------------------- */
+
+static void blk_bh(void *opaque)
+{
+    struct XenBlkDev *blkdev = opaque;
+
+    aio_context_acquire(blkdev->ctx);
+    blk_handle_requests(blkdev);
+    aio_context_release(blkdev->ctx);
+}
+
+static void blk_alloc(struct XenLegacyDevice *xendev)
+{
+    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
+    Error *err = NULL;
+
+    trace_xen_disk_alloc(xendev->name);
+
+    QLIST_INIT(&blkdev->inflight);
+    QLIST_INIT(&blkdev->finished);
+    QLIST_INIT(&blkdev->freelist);
+
+    blkdev->iothread = iothread_create(xendev->name, &err);
+    assert(!err);
+
+    blkdev->ctx = iothread_get_aio_context(blkdev->iothread);
+    blkdev->bh = aio_bh_new(blkdev->ctx, blk_bh, blkdev);
+}
+
+static void blk_parse_discard(struct XenBlkDev *blkdev)
+{
+    struct XenLegacyDevice *xendev = &blkdev->xendev;
+    int enable;
+
+    blkdev->feature_discard = true;
+
+    if (xenstore_read_be_int(xendev, "discard-enable", &enable) == 0) {
+        blkdev->feature_discard = !!enable;
+    }
+
+    if (blkdev->feature_discard) {
+        xenstore_write_be_int(xendev, "feature-discard", 1);
+    }
+}
+
+static int blk_init(struct XenLegacyDevice *xendev)
+{
+    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
+    int info = 0;
+    char *directiosafe = NULL;
+
+    trace_xen_disk_init(xendev->name);
+
+    /* read xenstore entries */
+    if (blkdev->params == NULL) {
+        char *h = NULL;
+        blkdev->params = xenstore_read_be_str(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 (!strcmp("vhd", blkdev->fileproto)) {
+        blkdev->fileproto = "vpc";
+    }
+    if (blkdev->mode == NULL) {
+        blkdev->mode = xenstore_read_be_str(xendev, "mode");
+    }
+    if (blkdev->type == NULL) {
+        blkdev->type = xenstore_read_be_str(xendev, "type");
+    }
+    if (blkdev->dev == NULL) {
+        blkdev->dev = xenstore_read_be_str(xendev, "dev");
+    }
+    if (blkdev->devtype == NULL) {
+        blkdev->devtype = xenstore_read_be_str(xendev, "device-type");
+    }
+    directiosafe = xenstore_read_be_str(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(xendev, "feature-flush-cache", 1);
+    xenstore_write_be_int(xendev, "info", info);
+
+    xenstore_write_be_int(xendev, "max-ring-page-order",
+                          MAX_RING_PAGE_ORDER);
+
+    blk_parse_discard(blkdev);
+
+    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 XenLegacyDevice *xendev)
+{
+    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
+    int index, qflags;
+    bool readonly = true;
+    bool writethrough = true;
+    int order, ring_ref;
+    unsigned int ring_size, max_grants;
+    unsigned int i;
+
+    trace_xen_disk_connect(xendev->name);
+
+    /* read-only ? */
+    if (blkdev->directiosafe) {
+        qflags = BDRV_O_NOCACHE | BDRV_O_NATIVE_AIO;
+    } else {
+        qflags = 0;
+        writethrough = false;
+    }
+    if (strcmp(blkdev->mode, "w") == 0) {
+        qflags |= BDRV_O_RDWR;
+        readonly = false;
+    }
+    if (blkdev->feature_discard) {
+        qflags |= BDRV_O_UNMAP;
+    }
+
+    /* init qemu block driver */
+    index = (xendev->dev - 202 * 256) / 16;
+    blkdev->dinfo = drive_get(IF_XEN, 0, index);
+    if (!blkdev->dinfo) {
+        Error *local_err = NULL;
+        QDict *options = NULL;
+
+        if (strcmp(blkdev->fileproto, "<unset>")) {
+            options = qdict_new();
+            qdict_put_str(options, "driver", blkdev->fileproto);
+        }
+
+        /* setup via xenbus -> create new block driver instance */
+        xen_pv_printf(xendev, 2, "create new bdrv (xenbus setup)\n");
+        blkdev->blk = blk_new_open(blkdev->filename, NULL, options,
+                                   qflags, &local_err);
+        if (!blkdev->blk) {
+            xen_pv_printf(xendev, 0, "error: %s\n",
+                          error_get_pretty(local_err));
+            error_free(local_err);
+            return -1;
+        }
+        blk_set_enable_write_cache(blkdev->blk, !writethrough);
+    } else {
+        /* setup via qemu cmdline -> already setup for us */
+        xen_pv_printf(xendev, 2,
+                      "get configured bdrv (cmdline setup)\n");
+        blkdev->blk = blk_by_legacy_dinfo(blkdev->dinfo);
+        if (blk_is_read_only(blkdev->blk) && !readonly) {
+            xen_pv_printf(xendev, 0, "Unexpected read-only drive");
+            blkdev->blk = NULL;
+            return -1;
+        }
+        /* blkdev->blk is not create by us, we get a reference
+         * so we can blk_unref() unconditionally */
+        blk_ref(blkdev->blk);
+    }
+    blk_attach_dev_legacy(blkdev->blk, blkdev);
+    blkdev->file_size = blk_getlength(blkdev->blk);
+    if (blkdev->file_size < 0) {
+        BlockDriverState *bs = blk_bs(blkdev->blk);
+        const char *drv_name = bs ? bdrv_get_format_name(bs) : NULL;
+        xen_pv_printf(xendev, 1, "blk_getlength: %d (%s) | drv %s\n",
+                      (int)blkdev->file_size, strerror(-blkdev->file_size),
+                      drv_name ?: "-");
+        blkdev->file_size = 0;
+    }
+
+    xen_pv_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 / MiB);
+
+    /* Fill in number of sector size and number of sectors */
+    xenstore_write_be_int(xendev, "sector-size", blkdev->file_blk);
+    xenstore_write_be_int64(xendev, "sectors",
+                            blkdev->file_size / blkdev->file_blk);
+
+    if (xenstore_read_fe_int(xendev, "ring-page-order",
+                             &order) == -1) {
+        blkdev->nr_ring_ref = 1;
+
+        if (xenstore_read_fe_int(xendev, "ring-ref",
+                                 &ring_ref) == -1) {
+            return -1;
+        }
+        blkdev->ring_ref[0] = ring_ref;
+
+    } else if (order >= 0 && order <= MAX_RING_PAGE_ORDER) {
+        blkdev->nr_ring_ref = 1 << order;
+
+        for (i = 0; i < blkdev->nr_ring_ref; i++) {
+            char *key;
+
+            key = g_strdup_printf("ring-ref%u", i);
+            if (!key) {
+                return -1;
+            }
+
+            if (xenstore_read_fe_int(xendev, key,
+                                     &ring_ref) == -1) {
+                g_free(key);
+                return -1;
+            }
+            blkdev->ring_ref[i] = ring_ref;
+
+            g_free(key);
+        }
+    } else {
+        xen_pv_printf(xendev, 0, "invalid ring-page-order: %d\n",
+                      order);
+        return -1;
+    }
+
+    if (xenstore_read_fe_int(xendev, "event-channel",
+                             &xendev->remote_port) == -1) {
+        return -1;
+    }
+
+    if (!xendev->protocol) {
+        blkdev->protocol = BLKIF_PROTOCOL_NATIVE;
+    } else if (strcmp(xendev->protocol, XEN_IO_PROTO_ABI_NATIVE) == 0) {
+        blkdev->protocol = BLKIF_PROTOCOL_NATIVE;
+    } else if (strcmp(xendev->protocol, XEN_IO_PROTO_ABI_X86_32) == 0) {
+        blkdev->protocol = BLKIF_PROTOCOL_X86_32;
+    } else if (strcmp(xendev->protocol, XEN_IO_PROTO_ABI_X86_64) == 0) {
+        blkdev->protocol = BLKIF_PROTOCOL_X86_64;
+    } else {
+        blkdev->protocol = BLKIF_PROTOCOL_NATIVE;
+    }
+
+    ring_size = XC_PAGE_SIZE * blkdev->nr_ring_ref;
+    switch (blkdev->protocol) {
+    case BLKIF_PROTOCOL_NATIVE:
+    {
+        blkdev->max_requests = __CONST_RING_SIZE(blkif, ring_size);
+        break;
+    }
+    case BLKIF_PROTOCOL_X86_32:
+    {
+        blkdev->max_requests = __CONST_RING_SIZE(blkif_x86_32, ring_size);
+        break;
+    }
+    case BLKIF_PROTOCOL_X86_64:
+    {
+        blkdev->max_requests = __CONST_RING_SIZE(blkif_x86_64, ring_size);
+        break;
+    }
+    default:
+        return -1;
+    }
+
+    /* Add on the number needed for the ring pages */
+    max_grants = blkdev->nr_ring_ref;
+
+    xen_be_set_max_grant_refs(xendev, max_grants);
+    blkdev->sring = xen_be_map_grant_refs(xendev, blkdev->ring_ref,
+                                          blkdev->nr_ring_ref,
+                                          PROT_READ | PROT_WRITE);
+    if (!blkdev->sring) {
+        return -1;
+    }
+
+    switch (blkdev->protocol) {
+    case BLKIF_PROTOCOL_NATIVE:
+    {
+        blkif_sring_t *sring_native = blkdev->sring;
+        BACK_RING_INIT(&blkdev->rings.native, sring_native, ring_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, ring_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, ring_size);
+        break;
+    }
+    }
+
+    blk_set_aio_context(blkdev->blk, blkdev->ctx);
+
+    xen_be_bind_evtchn(xendev);
+
+    xen_pv_printf(xendev, 1, "ok: proto %s, nr-ring-ref %u, "
+                  "remote port %d, local port %d\n",
+                  xendev->protocol, blkdev->nr_ring_ref,
+                  xendev->remote_port, xendev->local_port);
+    return 0;
+}
+
+static void blk_disconnect(struct XenLegacyDevice *xendev)
+{
+    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
+
+    trace_xen_disk_disconnect(xendev->name);
+
+    aio_context_acquire(blkdev->ctx);
+
+    if (blkdev->blk) {
+        blk_set_aio_context(blkdev->blk, qemu_get_aio_context());
+        blk_detach_dev(blkdev->blk, blkdev);
+        blk_unref(blkdev->blk);
+        blkdev->blk = NULL;
+    }
+    xen_pv_unbind_evtchn(xendev);
+
+    aio_context_release(blkdev->ctx);
+
+    if (blkdev->sring) {
+        xen_be_unmap_grant_refs(xendev, blkdev->sring,
+                                blkdev->nr_ring_ref);
+        blkdev->sring = NULL;
+    }
+}
+
+static int blk_free(struct XenLegacyDevice *xendev)
+{
+    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
+    struct ioreq *ioreq;
+
+    trace_xen_disk_free(xendev->name);
+
+    blk_disconnect(xendev);
+
+    while (!QLIST_EMPTY(&blkdev->freelist)) {
+        ioreq = QLIST_FIRST(&blkdev->freelist);
+        QLIST_REMOVE(ioreq, list);
+        qemu_iovec_destroy(&ioreq->v);
+        g_free(ioreq);
+    }
+
+    g_free(blkdev->params);
+    g_free(blkdev->mode);
+    g_free(blkdev->type);
+    g_free(blkdev->dev);
+    g_free(blkdev->devtype);
+    qemu_bh_delete(blkdev->bh);
+    iothread_destroy(blkdev->iothread);
+    return 0;
+}
+
+static void blk_event(struct XenLegacyDevice *xendev)
+{
+    struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
+
+    qemu_bh_schedule(blkdev->bh);
+}
+
+struct XenDevOps xen_blkdev_ops = {
+    .flags      = DEVOPS_FLAG_NEED_GNTDEV,
+    .size       = sizeof(struct XenBlkDev),
+    .alloc      = blk_alloc,
+    .init       = blk_init,
+    .initialise = blk_connect,
+    .disconnect = blk_disconnect,
+    .event      = blk_event,
+    .free       = blk_free,
+};