block/export: convert vhost-user-blk server to block export API

Use the new QAPI block exports API instead of defining our own QOM
objects.

This is a large change because the lifecycle of VuBlockDev needs to
follow BlockExportDriver. QOM properties are replaced by QAPI options
objects.

VuBlockDev is renamed VuBlkExport and contains a BlockExport field.
Several fields can be dropped since BlockExport already has equivalents.

The file names and meson build integration will be adjusted in a future
patch. libvhost-user should probably be built as a static library that
is linked into QEMU instead of as a .c file that results in duplicate
compilation.

The new command-line syntax is:

  $ qemu-storage-daemon \
      --blockdev file,node-name=drive0,filename=test.img \
      --export vhost-user-blk,node-name=drive0,id=export0,unix-socket=/tmp/vhost-user-blk.sock

Note that unix-socket is optional because we may wish to accept chardevs
too in the future.

Markus noted that supported address families are not explicit in the
QAPI schema. It is unlikely that support for more address families will
be added since file descriptor passing is required and few address
families support it. If a new address family needs to be added, then the
QAPI 'features' syntax can be used to advertize them.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20200924151549.913737-12-stefanha@redhat.com
[Skip test on big-endian host architectures because this device doesn't
support them yet (as already mentioned in a code comment).
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

7 files changed, 154 insertions, 356 deletions

diff --git a/block/export/export.c b/block/export/export.c
index f2c00d1..bd7cac2 100644
--- a/block/export/export.c
+++ b/block/export/export.c
@@ -17,6 +17,9 @@
 #include "sysemu/block-backend.h"
 #include "block/export.h"
 #include "block/nbd.h"
+#if CONFIG_LINUX
+#include "block/export/vhost-user-blk-server.h"
+#endif
 #include "qapi/error.h"
 #include "qapi/qapi-commands-block-export.h"
 #include "qapi/qapi-events-block-export.h"
@@ -24,6 +27,9 @@
 
 static const BlockExportDriver *blk_exp_drivers[] = {
     &blk_exp_nbd,
+#if CONFIG_LINUX
+    &blk_exp_vhost_user_blk,
+#endif
 };
 
 /* Only accessed from the main thread */
diff --git a/block/export/meson.build b/block/export/meson.build
index 558ef35..ef3a957 100644
--- a/block/export/meson.build
+++ b/block/export/meson.build
@@ -1 +1,2 @@
 block_ss.add(files('export.c'))
+block_ss.add(when: 'CONFIG_LINUX', if_true: files('vhost-user-blk-server.c', '../../contrib/libvhost-user/libvhost-user.c'))
diff --git a/block/export/vhost-user-blk-server.c b/block/export/vhost-user-blk-server.c
index faefcfc..3e5bd6c 100644
--- a/block/export/vhost-user-blk-server.c
+++ b/block/export/vhost-user-blk-server.c
@@ -11,6 +11,9 @@
  */
 #include "qemu/osdep.h"
 #include "block/block.h"
+#include "contrib/libvhost-user/libvhost-user.h"
+#include "standard-headers/linux/virtio_blk.h"
+#include "util/vhost-user-server.h"
 #include "vhost-user-blk-server.h"
 #include "qapi/error.h"
 #include "qom/object_interfaces.h"
@@ -24,7 +27,7 @@ struct virtio_blk_inhdr {
     unsigned char status;
 };
 
-typedef struct VuBlockReq {
+typedef struct VuBlkReq {
     VuVirtqElement elem;
     int64_t sector_num;
     size_t size;
@@ -32,9 +35,19 @@ typedef struct VuBlockReq {
     struct virtio_blk_outhdr out;
     VuServer *server;
     struct VuVirtq *vq;
-} VuBlockReq;
+} VuBlkReq;
 
-static void vu_block_req_complete(VuBlockReq *req)
+/* vhost user block device */
+typedef struct {
+    BlockExport export;
+    VuServer vu_server;
+    uint32_t blk_size;
+    QIOChannelSocket *sioc;
+    struct virtio_blk_config blkcfg;
+    bool writable;
+} VuBlkExport;
+
+static void vu_blk_req_complete(VuBlkReq *req)
 {
     VuDev *vu_dev = &req->server->vu_dev;
 
@@ -45,14 +58,9 @@ static void vu_block_req_complete(VuBlockReq *req)
     free(req);
 }
 
-static VuBlockDev *get_vu_block_device_by_server(VuServer *server)
-{
-    return container_of(server, VuBlockDev, vu_server);
-}
-
 static int coroutine_fn
-vu_block_discard_write_zeroes(VuBlockReq *req, struct iovec *iov,
-                              uint32_t iovcnt, uint32_t type)
+vu_blk_discard_write_zeroes(BlockBackend *blk, struct iovec *iov,
+                            uint32_t iovcnt, uint32_t type)
 {
     struct virtio_blk_discard_write_zeroes desc;
     ssize_t size = iov_to_buf(iov, iovcnt, 0, &desc, sizeof(desc));
@@ -61,16 +69,14 @@ vu_block_discard_write_zeroes(VuBlockReq *req, struct iovec *iov,
         return -EINVAL;
     }
 
-    VuBlockDev *vdev_blk = get_vu_block_device_by_server(req->server);
     uint64_t range[2] = { le64_to_cpu(desc.sector) << 9,
                           le32_to_cpu(desc.num_sectors) << 9 };
     if (type == VIRTIO_BLK_T_DISCARD) {
-        if (blk_co_pdiscard(vdev_blk->backend, range[0], range[1]) == 0) {
+        if (blk_co_pdiscard(blk, range[0], range[1]) == 0) {
             return 0;
         }
     } else if (type == VIRTIO_BLK_T_WRITE_ZEROES) {
-        if (blk_co_pwrite_zeroes(vdev_blk->backend,
-                                 range[0], range[1], 0) == 0) {
+        if (blk_co_pwrite_zeroes(blk, range[0], range[1], 0) == 0) {
             return 0;
         }
     }
@@ -78,22 +84,15 @@ vu_block_discard_write_zeroes(VuBlockReq *req, struct iovec *iov,
     return -EINVAL;
 }
 
-static int coroutine_fn vu_block_flush(VuBlockReq *req)
+static void coroutine_fn vu_blk_virtio_process_req(void *opaque)
 {
-    VuBlockDev *vdev_blk = get_vu_block_device_by_server(req->server);
-    BlockBackend *backend = vdev_blk->backend;
-    return blk_co_flush(backend);
-}
-
-static void coroutine_fn vu_block_virtio_process_req(void *opaque)
-{
-    VuBlockReq *req = opaque;
+    VuBlkReq *req = opaque;
     VuServer *server = req->server;
     VuVirtqElement *elem = &req->elem;
     uint32_t type;
 
-    VuBlockDev *vdev_blk = get_vu_block_device_by_server(server);
-    BlockBackend *backend = vdev_blk->backend;
+    VuBlkExport *vexp = container_of(server, VuBlkExport, vu_server);
+    BlockBackend *blk = vexp->export.blk;
 
     struct iovec *in_iov = elem->in_sg;
     struct iovec *out_iov = elem->out_sg;
@@ -133,16 +132,19 @@ static void coroutine_fn vu_block_virtio_process_req(void *opaque)
         bool is_write = type & VIRTIO_BLK_T_OUT;
         req->sector_num = le64_to_cpu(req->out.sector);
 
-        int64_t offset = req->sector_num * vdev_blk->blk_size;
+        if (is_write && !vexp->writable) {
+            req->in->status = VIRTIO_BLK_S_IOERR;
+            break;
+        }
+
+        int64_t offset = req->sector_num * vexp->blk_size;
         QEMUIOVector qiov;
         if (is_write) {
             qemu_iovec_init_external(&qiov, out_iov, out_num);
-            ret = blk_co_pwritev(backend, offset, qiov.size,
-                                 &qiov, 0);
+            ret = blk_co_pwritev(blk, offset, qiov.size, &qiov, 0);
         } else {
             qemu_iovec_init_external(&qiov, in_iov, in_num);
-            ret = blk_co_preadv(backend, offset, qiov.size,
-                                &qiov, 0);
+            ret = blk_co_preadv(blk, offset, qiov.size, &qiov, 0);
         }
         if (ret >= 0) {
             req->in->status = VIRTIO_BLK_S_OK;
@@ -152,7 +154,7 @@ static void coroutine_fn vu_block_virtio_process_req(void *opaque)
         break;
     }
     case VIRTIO_BLK_T_FLUSH:
-        if (vu_block_flush(req) == 0) {
+        if (blk_co_flush(blk) == 0) {
             req->in->status = VIRTIO_BLK_S_OK;
         } else {
             req->in->status = VIRTIO_BLK_S_IOERR;
@@ -169,8 +171,13 @@ static void coroutine_fn vu_block_virtio_process_req(void *opaque)
     case VIRTIO_BLK_T_DISCARD:
     case VIRTIO_BLK_T_WRITE_ZEROES: {
         int rc;
-        rc = vu_block_discard_write_zeroes(req, &elem->out_sg[1],
-                                           out_num, type);
+
+        if (!vexp->writable) {
+            req->in->status = VIRTIO_BLK_S_IOERR;
+            break;
+        }
+
+        rc = vu_blk_discard_write_zeroes(blk, &elem->out_sg[1], out_num, type);
         if (rc == 0) {
             req->in->status = VIRTIO_BLK_S_OK;
         } else {
@@ -183,22 +190,22 @@ static void coroutine_fn vu_block_virtio_process_req(void *opaque)
         break;
     }
 
-    vu_block_req_complete(req);
+    vu_blk_req_complete(req);
     return;
 
 err:
-    free(elem);
+    free(req);
 }
 
-static void vu_block_process_vq(VuDev *vu_dev, int idx)
+static void vu_blk_process_vq(VuDev *vu_dev, int idx)
 {
     VuServer *server = container_of(vu_dev, VuServer, vu_dev);
     VuVirtq *vq = vu_get_queue(vu_dev, idx);
 
     while (1) {
-        VuBlockReq *req;
+        VuBlkReq *req;
 
-        req = vu_queue_pop(vu_dev, vq, sizeof(VuBlockReq));
+        req = vu_queue_pop(vu_dev, vq, sizeof(VuBlkReq));
         if (!req) {
             break;
         }
@@ -207,26 +214,26 @@ static void vu_block_process_vq(VuDev *vu_dev, int idx)
         req->vq = vq;
 
         Coroutine *co =
-            qemu_coroutine_create(vu_block_virtio_process_req, req);
+            qemu_coroutine_create(vu_blk_virtio_process_req, req);
         qemu_coroutine_enter(co);
     }
 }
 
-static void vu_block_queue_set_started(VuDev *vu_dev, int idx, bool started)
+static void vu_blk_queue_set_started(VuDev *vu_dev, int idx, bool started)
 {
     VuVirtq *vq;
 
     assert(vu_dev);
 
     vq = vu_get_queue(vu_dev, idx);
-    vu_set_queue_handler(vu_dev, vq, started ? vu_block_process_vq : NULL);
+    vu_set_queue_handler(vu_dev, vq, started ? vu_blk_process_vq : NULL);
 }
 
-static uint64_t vu_block_get_features(VuDev *dev)
+static uint64_t vu_blk_get_features(VuDev *dev)
 {
     uint64_t features;
     VuServer *server = container_of(dev, VuServer, vu_dev);
-    VuBlockDev *vdev_blk = get_vu_block_device_by_server(server);
+    VuBlkExport *vexp = container_of(server, VuBlkExport, vu_server);
     features = 1ull << VIRTIO_BLK_F_SIZE_MAX |
                1ull << VIRTIO_BLK_F_SEG_MAX |
                1ull << VIRTIO_BLK_F_TOPOLOGY |
@@ -240,35 +247,35 @@ static uint64_t vu_block_get_features(VuDev *dev)
                1ull << VIRTIO_RING_F_EVENT_IDX |
                1ull << VHOST_USER_F_PROTOCOL_FEATURES;
 
-    if (!vdev_blk->writable) {
+    if (!vexp->writable) {
         features |= 1ull << VIRTIO_BLK_F_RO;
     }
 
     return features;
 }
 
-static uint64_t vu_block_get_protocol_features(VuDev *dev)
+static uint64_t vu_blk_get_protocol_features(VuDev *dev)
 {
     return 1ull << VHOST_USER_PROTOCOL_F_CONFIG |
            1ull << VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD;
 }
 
 static int
-vu_block_get_config(VuDev *vu_dev, uint8_t *config, uint32_t len)
+vu_blk_get_config(VuDev *vu_dev, uint8_t *config, uint32_t len)
 {
+    /* TODO blkcfg must be little-endian for VIRTIO 1.0 */
     VuServer *server = container_of(vu_dev, VuServer, vu_dev);
-    VuBlockDev *vdev_blk = get_vu_block_device_by_server(server);
-    memcpy(config, &vdev_blk->blkcfg, len);
-
+    VuBlkExport *vexp = container_of(server, VuBlkExport, vu_server);
+    memcpy(config, &vexp->blkcfg, len);
     return 0;
 }
 
 static int
-vu_block_set_config(VuDev *vu_dev, const uint8_t *data,
+vu_blk_set_config(VuDev *vu_dev, const uint8_t *data,
                     uint32_t offset, uint32_t size, uint32_t flags)
 {
     VuServer *server = container_of(vu_dev, VuServer, vu_dev);
-    VuBlockDev *vdev_blk = get_vu_block_device_by_server(server);
+    VuBlkExport *vexp = container_of(server, VuBlkExport, vu_server);
     uint8_t wce;
 
     /* don't support live migration */
@@ -282,8 +289,8 @@ vu_block_set_config(VuDev *vu_dev, const uint8_t *data,
     }
 
     wce = *data;
-    vdev_blk->blkcfg.wce = wce;
-    blk_set_enable_write_cache(vdev_blk->backend, wce);
+    vexp->blkcfg.wce = wce;
+    blk_set_enable_write_cache(vexp->export.blk, wce);
     return 0;
 }
 
@@ -295,7 +302,7 @@ vu_block_set_config(VuDev *vu_dev, const uint8_t *data,
  * of vu_process_message.
  *
  */
-static int vu_block_process_msg(VuDev *dev, VhostUserMsg *vmsg, int *do_reply)
+static int vu_blk_process_msg(VuDev *dev, VhostUserMsg *vmsg, int *do_reply)
 {
     if (vmsg->request == VHOST_USER_NONE) {
         dev->panic(dev, "disconnect");
@@ -304,29 +311,29 @@ static int vu_block_process_msg(VuDev *dev, VhostUserMsg *vmsg, int *do_reply)
     return false;
 }
 
-static const VuDevIface vu_block_iface = {
-    .get_features          = vu_block_get_features,
-    .queue_set_started     = vu_block_queue_set_started,
-    .get_protocol_features = vu_block_get_protocol_features,
-    .get_config            = vu_block_get_config,
-    .set_config            = vu_block_set_config,
-    .process_msg           = vu_block_process_msg,
+static const VuDevIface vu_blk_iface = {
+    .get_features          = vu_blk_get_features,
+    .queue_set_started     = vu_blk_queue_set_started,
+    .get_protocol_features = vu_blk_get_protocol_features,
+    .get_config            = vu_blk_get_config,
+    .set_config            = vu_blk_set_config,
+    .process_msg           = vu_blk_process_msg,
 };
 
 static void blk_aio_attached(AioContext *ctx, void *opaque)
 {
-    VuBlockDev *vub_dev = opaque;
-    vhost_user_server_attach_aio_context(&vub_dev->vu_server, ctx);
+    VuBlkExport *vexp = opaque;
+    vhost_user_server_attach_aio_context(&vexp->vu_server, ctx);
 }
 
 static void blk_aio_detach(void *opaque)
 {
-    VuBlockDev *vub_dev = opaque;
-    vhost_user_server_detach_aio_context(&vub_dev->vu_server);
+    VuBlkExport *vexp = opaque;
+    vhost_user_server_detach_aio_context(&vexp->vu_server);
 }
 
 static void
-vu_block_initialize_config(BlockDriverState *bs,
+vu_blk_initialize_config(BlockDriverState *bs,
                            struct virtio_blk_config *config, uint32_t blk_size)
 {
     config->capacity = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
@@ -343,290 +350,67 @@ vu_block_initialize_config(BlockDriverState *bs,
     config->max_write_zeroes_seg = 1;
 }
 
-static VuBlockDev *vu_block_init(VuBlockDev *vu_block_device, Error **errp)
+static void vu_blk_exp_request_shutdown(BlockExport *exp)
 {
+    VuBlkExport *vexp = container_of(exp, VuBlkExport, export);
 
-    BlockBackend *blk;
-    Error *local_error = NULL;
-    const char *node_name = vu_block_device->node_name;
-    bool writable = vu_block_device->writable;
-    uint64_t perm = BLK_PERM_CONSISTENT_READ;
-    int ret;
-
-    AioContext *ctx;
-
-    BlockDriverState *bs = bdrv_lookup_bs(node_name, node_name, &local_error);
-
-    if (!bs) {
-        error_propagate(errp, local_error);
-        return NULL;
-    }
-
-    if (bdrv_is_read_only(bs)) {
-        writable = false;
-    }
-
-    if (writable) {
-        perm |= BLK_PERM_WRITE;
-    }
-
-    ctx = bdrv_get_aio_context(bs);
-    aio_context_acquire(ctx);
-    bdrv_invalidate_cache(bs, NULL);
-    aio_context_release(ctx);
-
-    /*
-     * Don't allow resize while the vhost user server is running,
-     * otherwise we don't care what happens with the node.
-     */
-    blk = blk_new(bdrv_get_aio_context(bs), perm,
-                  BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
-                  BLK_PERM_WRITE | BLK_PERM_GRAPH_MOD);
-    ret = blk_insert_bs(blk, bs, errp);
-
-    if (ret < 0) {
-        goto fail;
-    }
-
-    blk_set_enable_write_cache(blk, false);
-
-    blk_set_allow_aio_context_change(blk, true);
-
-    vu_block_device->blkcfg.wce = 0;
-    vu_block_device->backend = blk;
-    if (!vu_block_device->blk_size) {
-        vu_block_device->blk_size = BDRV_SECTOR_SIZE;
-    }
-    vu_block_device->blkcfg.blk_size = vu_block_device->blk_size;
-    blk_set_guest_block_size(blk, vu_block_device->blk_size);
-    vu_block_initialize_config(bs, &vu_block_device->blkcfg,
-                                   vu_block_device->blk_size);
-    return vu_block_device;
-
-fail:
-    blk_unref(blk);
-    return NULL;
-}
-
-static void vu_block_deinit(VuBlockDev *vu_block_device)
-{
-    if (vu_block_device->backend) {
-        blk_remove_aio_context_notifier(vu_block_device->backend, blk_aio_attached,
-                                        blk_aio_detach, vu_block_device);
-    }
-
-    blk_unref(vu_block_device->backend);
+    vhost_user_server_stop(&vexp->vu_server);
 }
 
-static void vhost_user_blk_server_stop(VuBlockDev *vu_block_device)
+static int vu_blk_exp_create(BlockExport *exp, BlockExportOptions *opts,
+                             Error **errp)
 {
-    vhost_user_server_stop(&vu_block_device->vu_server);
-    vu_block_deinit(vu_block_device);
-}
-
-static void vhost_user_blk_server_start(VuBlockDev *vu_block_device,
-                                        Error **errp)
-{
-    AioContext *ctx;
-    SocketAddress *addr = vu_block_device->addr;
-
-    if (!vu_block_init(vu_block_device, errp)) {
-        return;
-    }
-
-    ctx = bdrv_get_aio_context(blk_bs(vu_block_device->backend));
-
-    if (!vhost_user_server_start(&vu_block_device->vu_server, addr, ctx,
-                                 VHOST_USER_BLK_MAX_QUEUES, &vu_block_iface,
-                                 errp)) {
-        goto error;
-    }
-
-    blk_add_aio_context_notifier(vu_block_device->backend, blk_aio_attached,
-                                 blk_aio_detach, vu_block_device);
-    vu_block_device->running = true;
-    return;
-
- error:
-    vu_block_deinit(vu_block_device);
-}
-
-static bool vu_prop_modifiable(VuBlockDev *vus, Error **errp)
-{
-    if (vus->running) {
-            error_setg(errp, "The property can't be modified "
-                       "while the server is running");
-            return false;
-    }
-    return true;
-}
-
-static void vu_set_node_name(Object *obj, const char *value, Error **errp)
-{
-    VuBlockDev *vus = VHOST_USER_BLK_SERVER(obj);
-
-    if (!vu_prop_modifiable(vus, errp)) {
-        return;
-    }
-
-    if (vus->node_name) {
-        g_free(vus->node_name);
-    }
-
-    vus->node_name = g_strdup(value);
-}
-
-static char *vu_get_node_name(Object *obj, Error **errp)
-{
-    VuBlockDev *vus = VHOST_USER_BLK_SERVER(obj);
-    return g_strdup(vus->node_name);
-}
-
-static void free_socket_addr(SocketAddress *addr)
-{
-        g_free(addr->u.q_unix.path);
-        g_free(addr);
-}
-
-static void vu_set_unix_socket(Object *obj, const char *value,
-                               Error **errp)
-{
-    VuBlockDev *vus = VHOST_USER_BLK_SERVER(obj);
-
-    if (!vu_prop_modifiable(vus, errp)) {
-        return;
-    }
-
-    if (vus->addr) {
-        free_socket_addr(vus->addr);
-    }
-
-    SocketAddress *addr = g_new0(SocketAddress, 1);
-    addr->type = SOCKET_ADDRESS_TYPE_UNIX;
-    addr->u.q_unix.path = g_strdup(value);
-    vus->addr = addr;
-}
-
-static char *vu_get_unix_socket(Object *obj, Error **errp)
-{
-    VuBlockDev *vus = VHOST_USER_BLK_SERVER(obj);
-    return g_strdup(vus->addr->u.q_unix.path);
-}
-
-static bool vu_get_block_writable(Object *obj, Error **errp)
-{
-    VuBlockDev *vus = VHOST_USER_BLK_SERVER(obj);
-    return vus->writable;
-}
-
-static void vu_set_block_writable(Object *obj, bool value, Error **errp)
-{
-    VuBlockDev *vus = VHOST_USER_BLK_SERVER(obj);
-
-    if (!vu_prop_modifiable(vus, errp)) {
-            return;
-    }
-
-    vus->writable = value;
-}
-
-static void vu_get_blk_size(Object *obj, Visitor *v, const char *name,
-                            void *opaque, Error **errp)
-{
-    VuBlockDev *vus = VHOST_USER_BLK_SERVER(obj);
-    uint32_t value = vus->blk_size;
-
-    visit_type_uint32(v, name, &value, errp);
-}
-
-static void vu_set_blk_size(Object *obj, Visitor *v, const char *name,
-                            void *opaque, Error **errp)
-{
-    VuBlockDev *vus = VHOST_USER_BLK_SERVER(obj);
-
+    VuBlkExport *vexp = container_of(exp, VuBlkExport, export);
+    BlockExportOptionsVhostUserBlk *vu_opts = &opts->u.vhost_user_blk;
     Error *local_err = NULL;
-    uint32_t value;
+    uint64_t logical_block_size;
 
-    if (!vu_prop_modifiable(vus, errp)) {
-            return;
-    }
+    vexp->writable = opts->writable;
+    vexp->blkcfg.wce = 0;
 
-    visit_type_uint32(v, name, &value, &local_err);
-    if (local_err) {
-        goto out;
+    if (vu_opts->has_logical_block_size) {
+        logical_block_size = vu_opts->logical_block_size;
+    } else {
+        logical_block_size = BDRV_SECTOR_SIZE;
     }
-
-    check_block_size(object_get_typename(obj), name, value, &local_err);
+    check_block_size(exp->id, "logical-block-size", logical_block_size,
+                     &local_err);
     if (local_err) {
-        goto out;
+        error_propagate(errp, local_err);
+        return -EINVAL;
     }
+    vexp->blk_size = logical_block_size;
+    blk_set_guest_block_size(exp->blk, logical_block_size);
+    vu_blk_initialize_config(blk_bs(exp->blk), &vexp->blkcfg,
+                               logical_block_size);
 
-    vus->blk_size = value;
-
-out:
-    error_propagate(errp, local_err);
-}
-
-static void vhost_user_blk_server_instance_finalize(Object *obj)
-{
-    VuBlockDev *vub = VHOST_USER_BLK_SERVER(obj);
+    blk_set_allow_aio_context_change(exp->blk, true);
+    blk_add_aio_context_notifier(exp->blk, blk_aio_attached, blk_aio_detach,
+                                 vexp);
 
-    vhost_user_blk_server_stop(vub);
-
-    /*
-     * Unlike object_property_add_str, object_class_property_add_str
-     * doesn't have a release method. Thus manual memory freeing is
-     * needed.
-     */
-    free_socket_addr(vub->addr);
-    g_free(vub->node_name);
-}
-
-static void vhost_user_blk_server_complete(UserCreatable *obj, Error **errp)
-{
-    VuBlockDev *vub = VHOST_USER_BLK_SERVER(obj);
+    if (!vhost_user_server_start(&vexp->vu_server, vu_opts->addr, exp->ctx,
+                                 VHOST_USER_BLK_MAX_QUEUES, &vu_blk_iface,
+                                 errp)) {
+        blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
+                                        blk_aio_detach, vexp);
+        return -EADDRNOTAVAIL;
+    }
 
-    vhost_user_blk_server_start(vub, errp);
+    return 0;
 }
 
-static void vhost_user_blk_server_class_init(ObjectClass *klass,
-                                             void *class_data)
+static void vu_blk_exp_delete(BlockExport *exp)
 {
-    UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
-    ucc->complete = vhost_user_blk_server_complete;
+    VuBlkExport *vexp = container_of(exp, VuBlkExport, export);
 
-    object_class_property_add_bool(klass, "writable",
-                                   vu_get_block_writable,
-                                   vu_set_block_writable);
-
-    object_class_property_add_str(klass, "node-name",
-                                  vu_get_node_name,
-                                  vu_set_node_name);
-
-    object_class_property_add_str(klass, "unix-socket",
-                                  vu_get_unix_socket,
-                                  vu_set_unix_socket);
-
-    object_class_property_add(klass, "logical-block-size", "uint32",
-                              vu_get_blk_size, vu_set_blk_size,
-                              NULL, NULL);
+    blk_remove_aio_context_notifier(exp->blk, blk_aio_attached, blk_aio_detach,
+                                    vexp);
 }
 
-static const TypeInfo vhost_user_blk_server_info = {
-    .name = TYPE_VHOST_USER_BLK_SERVER,
-    .parent = TYPE_OBJECT,
-    .instance_size = sizeof(VuBlockDev),
-    .instance_finalize = vhost_user_blk_server_instance_finalize,
-    .class_init = vhost_user_blk_server_class_init,
-    .interfaces = (InterfaceInfo[]) {
-        {TYPE_USER_CREATABLE},
-        {}
-    },
+const BlockExportDriver blk_exp_vhost_user_blk = {
+    .type               = BLOCK_EXPORT_TYPE_VHOST_USER_BLK,
+    .instance_size      = sizeof(VuBlkExport),
+    .create             = vu_blk_exp_create,
+    .delete             = vu_blk_exp_delete,
+    .request_shutdown   = vu_blk_exp_request_shutdown,
 };
-
-static void vhost_user_blk_server_register_types(void)
-{
-    type_register_static(&vhost_user_blk_server_info);
-}
-
-type_init(vhost_user_blk_server_register_types)
diff --git a/block/export/vhost-user-blk-server.h b/block/export/vhost-user-blk-server.h
index f06f37c..fcf46fc 100644
--- a/block/export/vhost-user-blk-server.h
+++ b/block/export/vhost-user-blk-server.h
@@ -10,27 +10,10 @@
 
 #ifndef VHOST_USER_BLK_SERVER_H
 #define VHOST_USER_BLK_SERVER_H
-#include "util/vhost-user-server.h"
 
-typedef struct VuBlockDev VuBlockDev;
-#define TYPE_VHOST_USER_BLK_SERVER "vhost-user-blk-server"
-#define VHOST_USER_BLK_SERVER(obj) \
-   OBJECT_CHECK(VuBlockDev, obj, TYPE_VHOST_USER_BLK_SERVER)
+#include "block/export.h"
 
-/* vhost user block device */
-struct VuBlockDev {
-    Object parent_obj;
-    char *node_name;
-    SocketAddress *addr;
-    AioContext *ctx;
-    VuServer vu_server;
-    bool running;
-    uint32_t blk_size;
-    BlockBackend *backend;
-    QIOChannelSocket *sioc;
-    QTAILQ_ENTRY(VuBlockDev) next;
-    struct virtio_blk_config blkcfg;
-    bool writable;
-};
+/* For block/export/export.c */
+extern const BlockExportDriver blk_exp_vhost_user_blk;
 
 #endif /* VHOST_USER_BLK_SERVER_H */
diff --git a/block/meson.build b/block/meson.build
index 6e6c1dc..78e8b25 100644
--- a/block/meson.build
+++ b/block/meson.build
@@ -60,7 +60,6 @@ block_ss.add(when: 'CONFIG_WIN32', if_true: files('file-win32.c', 'win32-aio.c')
 block_ss.add(when: 'CONFIG_POSIX', if_true: [files('file-posix.c'), coref, iokit])
 block_ss.add(when: 'CONFIG_LIBISCSI', if_true: files('iscsi-opts.c'))
 block_ss.add(when: 'CONFIG_LINUX', if_true: files('nvme.c'))
-block_ss.add(when: 'CONFIG_LINUX', if_true: files('export/vhost-user-blk-server.c', '../contrib/libvhost-user/libvhost-user.c'))
 block_ss.add(when: 'CONFIG_REPLICATION', if_true: files('replication.c'))
 block_ss.add(when: 'CONFIG_SHEEPDOG', if_true: files('sheepdog.c'))
 block_ss.add(when: ['CONFIG_LINUX_AIO', libaio], if_true: files('linux-aio.c'))
diff --git a/qapi/block-export.json b/qapi/block-export.json
index 6580483..a793e34 100644
--- a/qapi/block-export.json
+++ b/qapi/block-export.json
@@ -85,6 +85,21 @@
             '*bitmap': 'str' } }
 
 ##
+# @BlockExportOptionsVhostUserBlk:
+#
+# A vhost-user-blk block export.
+#
+# @addr: The vhost-user socket on which to listen. Both 'unix' and 'fd'
+#        SocketAddress types are supported. Passed fds must be UNIX domain
+#        sockets.
+# @logical-block-size: Logical block size in bytes. Defaults to 512 bytes.
+#
+# Since: 5.2
+##
+{ 'struct': 'BlockExportOptionsVhostUserBlk',
+  'data': { 'addr': 'SocketAddress', '*logical-block-size': 'size' } }
+
+##
 # @NbdServerAddOptions:
 #
 # An NBD block export.
@@ -180,11 +195,12 @@
 # An enumeration of block export types
 #
 # @nbd: NBD export
+# @vhost-user-blk: vhost-user-blk export (since 5.2)
 #
 # Since: 4.2
 ##
 { 'enum': 'BlockExportType',
-  'data': [ 'nbd' ] }
+  'data': [ 'nbd', 'vhost-user-blk' ] }
 
 ##
 # @BlockExportOptions:
@@ -213,7 +229,8 @@
             '*writethrough': 'bool' },
   'discriminator': 'type',
   'data': {
-      'nbd': 'BlockExportOptionsNbd'
+      'nbd': 'BlockExportOptionsNbd',
+      'vhost-user-blk': 'BlockExportOptionsVhostUserBlk'
    } }
 
 ##
diff --git a/util/vhost-user-server.c b/util/vhost-user-server.c
index c448800..516999b 100644
--- a/util/vhost-user-server.c
+++ b/util/vhost-user-server.c
@@ -408,7 +408,15 @@ bool vhost_user_server_start(VuServer *server,
                              Error **errp)
 {
     QEMUBH *bh;
-    QIONetListener *listener = qio_net_listener_new();
+    QIONetListener *listener;
+
+    if (socket_addr->type != SOCKET_ADDRESS_TYPE_UNIX &&
+        socket_addr->type != SOCKET_ADDRESS_TYPE_FD) {
+        error_setg(errp, "Only socket address types 'unix' and 'fd' are supported");
+        return false;
+    }
+
+    listener = qio_net_listener_new();
     if (qio_net_listener_open_sync(listener, socket_addr, 1,
                                    errp) < 0) {
         object_unref(OBJECT(listener));