diff --git a/block/nbd-client.c b/block/nbd-client.c
index 9206652e45c6dc856dfa9a9403a1764dfc6081e1..7b68499b76a3c74f635f51ca5affb834152709a5 100644
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -846,9 +846,6 @@ int nbd_client_init(BlockDriverState *bs,
     if (client->info.flags & NBD_FLAG_SEND_WRITE_ZEROES) {
         bs->supported_zero_flags |= BDRV_REQ_MAY_UNMAP;
     }
-    if (client->info.min_block > bs->bl.request_alignment) {
-        bs->bl.request_alignment = client->info.min_block;
-    }
 
     qemu_co_mutex_init(&client->send_mutex);
     qemu_co_queue_init(&client->free_sema);
diff --git a/block/nbd.c b/block/nbd.c
index ef81a9f53baaf1a09ed50af1ed09d741f947280a..69b5fd5e8fabd18d548cba073053571b872245d0 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -474,8 +474,10 @@ static int nbd_co_flush(BlockDriverState *bs)
 static void nbd_refresh_limits(BlockDriverState *bs, Error **errp)
 {
     NBDClientSession *s = nbd_get_client_session(bs);
+    uint32_t min = s->info.min_block;
     uint32_t max = MIN_NON_ZERO(NBD_MAX_BUFFER_SIZE, s->info.max_block);
 
+    bs->bl.request_alignment = min ? min : BDRV_SECTOR_SIZE;
     bs->bl.max_pdiscard = max;
     bs->bl.max_pwrite_zeroes = max;
     bs->bl.max_transfer = max;
diff --git a/include/block/nbd.h b/include/block/nbd.h
index fc500030038d7d9f35a5ca0fc7216f7dcf1b1658..495564c73a425d2371a8b86221932909381fd98e 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -41,6 +41,12 @@ struct NBDOptionReply {
 } QEMU_PACKED;
 typedef struct NBDOptionReply NBDOptionReply;
 
+typedef struct NBDOptionReplyMetaContext {
+    NBDOptionReply h; /* h.type = NBD_REP_META_CONTEXT, h.length > 4 */
+    uint32_t context_id;
+    /* meta context name follows */
+} QEMU_PACKED NBDOptionReplyMetaContext;
+
 /* Transmission phase structs
  *
  * Note: these are _NOT_ the same as the network representation of an NBD
@@ -105,6 +111,19 @@ typedef struct NBDStructuredError {
     uint16_t message_length;
 } QEMU_PACKED NBDStructuredError;
 
+/* Header of NBD_REPLY_TYPE_BLOCK_STATUS */
+typedef struct NBDStructuredMeta {
+    NBDStructuredReplyChunk h; /* h.length >= 12 (at least one extent) */
+    uint32_t context_id;
+    /* extents follows */
+} QEMU_PACKED NBDStructuredMeta;
+
+/* Extent chunk for NBD_REPLY_TYPE_BLOCK_STATUS */
+typedef struct NBDExtent {
+    uint32_t length;
+    uint32_t flags; /* NBD_STATE_* */
+} QEMU_PACKED NBDExtent;
+
 /* Transmission (export) flags: sent from server to client during handshake,
    but describe what will happen during transmission */
 #define NBD_FLAG_HAS_FLAGS         (1 << 0) /* Flags are there */
@@ -128,21 +147,24 @@ typedef struct NBDStructuredError {
 #define NBD_FLAG_C_NO_ZEROES      (1 << 1) /* End handshake without zeroes. */
 
 /* Option requests. */
-#define NBD_OPT_EXPORT_NAME      (1)
-#define NBD_OPT_ABORT            (2)
-#define NBD_OPT_LIST             (3)
-/* #define NBD_OPT_PEEK_EXPORT   (4) not in use */
-#define NBD_OPT_STARTTLS         (5)
-#define NBD_OPT_INFO             (6)
-#define NBD_OPT_GO               (7)
-#define NBD_OPT_STRUCTURED_REPLY (8)
+#define NBD_OPT_EXPORT_NAME       (1)
+#define NBD_OPT_ABORT             (2)
+#define NBD_OPT_LIST              (3)
+/* #define NBD_OPT_PEEK_EXPORT    (4) not in use */
+#define NBD_OPT_STARTTLS          (5)
+#define NBD_OPT_INFO              (6)
+#define NBD_OPT_GO                (7)
+#define NBD_OPT_STRUCTURED_REPLY  (8)
+#define NBD_OPT_LIST_META_CONTEXT (9)
+#define NBD_OPT_SET_META_CONTEXT  (10)
 
 /* Option reply types. */
 #define NBD_REP_ERR(value) ((UINT32_C(1) << 31) | (value))
 
-#define NBD_REP_ACK             (1)             /* Data sending finished. */
-#define NBD_REP_SERVER          (2)             /* Export description. */
-#define NBD_REP_INFO            (3)             /* NBD_OPT_INFO/GO. */
+#define NBD_REP_ACK             (1)    /* Data sending finished. */
+#define NBD_REP_SERVER          (2)    /* Export description. */
+#define NBD_REP_INFO            (3)    /* NBD_OPT_INFO/GO. */
+#define NBD_REP_META_CONTEXT    (4)    /* NBD_OPT_{LIST,SET}_META_CONTEXT */
 
 #define NBD_REP_ERR_UNSUP           NBD_REP_ERR(1)  /* Unknown option */
 #define NBD_REP_ERR_POLICY          NBD_REP_ERR(2)  /* Server denied */
@@ -163,6 +185,8 @@ typedef struct NBDStructuredError {
 #define NBD_CMD_FLAG_FUA        (1 << 0) /* 'force unit access' during write */
 #define NBD_CMD_FLAG_NO_HOLE    (1 << 1) /* don't punch hole on zero run */
 #define NBD_CMD_FLAG_DF         (1 << 2) /* don't fragment structured read */
+#define NBD_CMD_FLAG_REQ_ONE    (1 << 3) /* only one extent in BLOCK_STATUS
+                                          * reply chunk */
 
 /* Supported request types */
 enum {
@@ -173,6 +197,7 @@ enum {
     NBD_CMD_TRIM = 4,
     /* 5 reserved for failed experiment NBD_CMD_CACHE */
     NBD_CMD_WRITE_ZEROES = 6,
+    NBD_CMD_BLOCK_STATUS = 7,
 };
 
 #define NBD_DEFAULT_PORT	10809
@@ -200,9 +225,15 @@ enum {
 #define NBD_REPLY_TYPE_NONE          0
 #define NBD_REPLY_TYPE_OFFSET_DATA   1
 #define NBD_REPLY_TYPE_OFFSET_HOLE   2
+#define NBD_REPLY_TYPE_BLOCK_STATUS  5
 #define NBD_REPLY_TYPE_ERROR         NBD_REPLY_ERR(1)
 #define NBD_REPLY_TYPE_ERROR_OFFSET  NBD_REPLY_ERR(2)
 
+/* Flags for extents (NBDExtent.flags) of NBD_REPLY_TYPE_BLOCK_STATUS,
+ * for base:allocation meta context */
+#define NBD_STATE_HOLE (1 << 0)
+#define NBD_STATE_ZERO (1 << 1)
+
 static inline bool nbd_reply_type_is_error(int type)
 {
     return type & (1 << 15);
diff --git a/nbd/client.c b/nbd/client.c
index 89f80f9590532de37a6eed22baa5ea37266e1d09..9c3fe4aaa67bb5d14d6568ddd6067b89e423ea11 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -158,14 +158,14 @@ static int nbd_handle_reply_err(QIOChannel *ioc, NBDOptionReply *reply,
 
     if (reply->length) {
         if (reply->length > NBD_MAX_BUFFER_SIZE) {
-            error_setg(errp, "server error 0x%" PRIx32
+            error_setg(errp, "server error %" PRIu32
                        " (%s) message is too long",
                        reply->type, nbd_rep_lookup(reply->type));
             goto cleanup;
         }
         msg = g_malloc(reply->length + 1);
         if (nbd_read(ioc, msg, reply->length, errp) < 0) {
-            error_prepend(errp, "failed to read option error 0x%" PRIx32
+            error_prepend(errp, "failed to read option error %" PRIu32
                           " (%s) message: ",
                           reply->type, nbd_rep_lookup(reply->type));
             goto cleanup;
@@ -180,22 +180,22 @@ static int nbd_handle_reply_err(QIOChannel *ioc, NBDOptionReply *reply,
         goto cleanup;
 
     case NBD_REP_ERR_POLICY:
-        error_setg(errp, "Denied by server for option %" PRIx32 " (%s)",
+        error_setg(errp, "Denied by server for option %" PRIu32 " (%s)",
                    reply->option, nbd_opt_lookup(reply->option));
         break;
 
     case NBD_REP_ERR_INVALID:
-        error_setg(errp, "Invalid data length for option %" PRIx32 " (%s)",
+        error_setg(errp, "Invalid parameters for option %" PRIu32 " (%s)",
                    reply->option, nbd_opt_lookup(reply->option));
         break;
 
     case NBD_REP_ERR_PLATFORM:
-        error_setg(errp, "Server lacks support for option %" PRIx32 " (%s)",
+        error_setg(errp, "Server lacks support for option %" PRIu32 " (%s)",
                    reply->option, nbd_opt_lookup(reply->option));
         break;
 
     case NBD_REP_ERR_TLS_REQD:
-        error_setg(errp, "TLS negotiation required before option %" PRIx32
+        error_setg(errp, "TLS negotiation required before option %" PRIu32
                    " (%s)", reply->option, nbd_opt_lookup(reply->option));
         break;
 
@@ -204,17 +204,17 @@ static int nbd_handle_reply_err(QIOChannel *ioc, NBDOptionReply *reply,
         break;
 
     case NBD_REP_ERR_SHUTDOWN:
-        error_setg(errp, "Server shutting down before option %" PRIx32 " (%s)",
+        error_setg(errp, "Server shutting down before option %" PRIu32 " (%s)",
                    reply->option, nbd_opt_lookup(reply->option));
         break;
 
     case NBD_REP_ERR_BLOCK_SIZE_REQD:
-        error_setg(errp, "Server requires INFO_BLOCK_SIZE for option %" PRIx32
+        error_setg(errp, "Server requires INFO_BLOCK_SIZE for option %" PRIu32
                    " (%s)", reply->option, nbd_opt_lookup(reply->option));
         break;
 
     default:
-        error_setg(errp, "Unknown error code when asking for option %" PRIx32
+        error_setg(errp, "Unknown error code when asking for option %" PRIu32
                    " (%s)", reply->option, nbd_opt_lookup(reply->option));
         break;
     }
@@ -378,8 +378,8 @@ static int nbd_opt_go(QIOChannel *ioc, const char *wantname,
             return 1;
         }
         if (reply.type != NBD_REP_INFO) {
-            error_setg(errp, "unexpected reply type %" PRIx32
-                       " (%s), expected %x",
+            error_setg(errp, "unexpected reply type %" PRIu32
+                       " (%s), expected %u",
                        reply.type, nbd_rep_lookup(reply.type), NBD_REP_INFO);
             nbd_send_opt_abort(ioc);
             return -1;
@@ -534,7 +534,7 @@ static int nbd_request_simple_option(QIOChannel *ioc, int opt, Error **errp)
 
     if (reply.type != NBD_REP_ACK) {
         error_setg(errp, "Server answered option %d (%s) with unexpected "
-                   "reply %" PRIx32 " (%s)", opt, nbd_opt_lookup(opt),
+                   "reply %" PRIu32 " (%s)", opt, nbd_opt_lookup(opt),
                    reply.type, nbd_rep_lookup(reply.type));
         nbd_send_opt_abort(ioc);
         return -1;
diff --git a/nbd/common.c b/nbd/common.c
index 6295526dd14379b90ae846d07cc1e9000ed029c7..8c95c1d606ea6e3b261b195e23452f47d56273e6 100644
--- a/nbd/common.c
+++ b/nbd/common.c
@@ -75,6 +75,10 @@ const char *nbd_opt_lookup(uint32_t opt)
         return "go";
     case NBD_OPT_STRUCTURED_REPLY:
         return "structured reply";
+    case NBD_OPT_LIST_META_CONTEXT:
+        return "list meta context";
+    case NBD_OPT_SET_META_CONTEXT:
+        return "set meta context";
     default:
         return "<unknown>";
     }
@@ -90,6 +94,8 @@ const char *nbd_rep_lookup(uint32_t rep)
         return "server";
     case NBD_REP_INFO:
         return "info";
+    case NBD_REP_META_CONTEXT:
+        return "meta context";
     case NBD_REP_ERR_UNSUP:
         return "unsupported";
     case NBD_REP_ERR_POLICY:
@@ -144,6 +150,8 @@ const char *nbd_cmd_lookup(uint16_t cmd)
         return "trim";
     case NBD_CMD_WRITE_ZEROES:
         return "write zeroes";
+    case NBD_CMD_BLOCK_STATUS:
+        return "block status";
     default:
         return "<unknown>";
     }
@@ -159,6 +167,8 @@ const char *nbd_reply_type_lookup(uint16_t type)
         return "data";
     case NBD_REPLY_TYPE_OFFSET_HOLE:
         return "hole";
+    case NBD_REPLY_TYPE_BLOCK_STATUS:
+        return "block status";
     case NBD_REPLY_TYPE_ERROR:
         return "generic error";
     case NBD_REPLY_TYPE_ERROR_OFFSET:
diff --git a/nbd/server.c b/nbd/server.c
index 112e3f69dff7b336f05a5db1638dbd1ecf7bbc53..4990a5826e61f2ea66bdd55e94d7e55dcd7fc7b9 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -806,7 +806,7 @@ static int nbd_negotiate_options(NBDClient *client, uint16_t myflags,
 
             default:
                 ret = nbd_opt_drop(client, NBD_REP_ERR_UNSUP, errp,
-                                   "Unsupported option 0x%" PRIx32 " (%s)",
+                                   "Unsupported option %" PRIu32 " (%s)",
                                    option, nbd_opt_lookup(option));
                 break;
             }
@@ -822,7 +822,7 @@ static int nbd_negotiate_options(NBDClient *client, uint16_t myflags,
                                                         errp);
 
             default:
-                error_setg(errp, "Unsupported option 0x%" PRIx32 " (%s)",
+                error_setg(errp, "Unsupported option %" PRIu32 " (%s)",
                            option, nbd_opt_lookup(option));
                 return -EINVAL;
             }
diff --git a/nbd/trace-events b/nbd/trace-events
index 2b8268ce8c398c383ca7f6439aab2a96a6ce4e73..0d03edc967d031c2d625ab691fe254ea3f93e38a 100644
--- a/nbd/trace-events
+++ b/nbd/trace-events
@@ -1,7 +1,7 @@
 # nbd/client.c
 nbd_send_option_request(uint32_t opt, const char *name, uint32_t len) "Sending option request %" PRIu32" (%s), len %" PRIu32
-nbd_receive_option_reply(uint32_t option, const char *optname, uint32_t type, const char *typename, uint32_t length) "Received option reply 0x%" PRIx32" (%s), type 0x%" PRIx32" (%s), len %" PRIu32
-nbd_reply_err_unsup(uint32_t option, const char *name) "server doesn't understand request 0x%" PRIx32 " (%s), attempting fallback"
+nbd_receive_option_reply(uint32_t option, const char *optname, uint32_t type, const char *typename, uint32_t length) "Received option reply %" PRIu32" (%s), type %" PRIu32" (%s), len %" PRIu32
+nbd_reply_err_unsup(uint32_t option, const char *name) "server doesn't understand request %" PRIu32 " (%s), attempting fallback"
 nbd_opt_go_start(const char *name) "Attempting NBD_OPT_GO for export '%s'"
 nbd_opt_go_success(void) "Export is good to go"
 nbd_opt_go_info_unknown(int info, const char *name) "Ignoring unknown info %d (%s)"
@@ -33,7 +33,7 @@ nbd_receive_structured_reply_chunk(uint16_t flags, uint16_t type, const char *na
 nbd_unknown_error(int err) "Squashing unexpected error %d to EINVAL"
 
 # nbd/server.c
-nbd_negotiate_send_rep_len(uint32_t opt, const char *optname, uint32_t type, const char *typename, uint32_t len) "Reply opt=0x%" PRIx32 " (%s), type=0x%" PRIx32 " (%s), len=%" PRIu32
+nbd_negotiate_send_rep_len(uint32_t opt, const char *optname, uint32_t type, const char *typename, uint32_t len) "Reply opt=%" PRIu32 " (%s), type=%" PRIu32 " (%s), len=%" PRIu32
 nbd_negotiate_send_rep_err(const char *msg) "sending error message \"%s\""
 nbd_negotiate_send_rep_list(const char *name, const char *desc) "Advertising export name '%s' description '%s'"
 nbd_negotiate_handle_export_name(void) "Checking length"
@@ -46,7 +46,7 @@ nbd_negotiate_handle_starttls(void) "Setting up TLS"
 nbd_negotiate_handle_starttls_handshake(void) "Starting TLS handshake"
 nbd_negotiate_options_flags(uint32_t flags) "Received client flags 0x%" PRIx32
 nbd_negotiate_options_check_magic(uint64_t magic) "Checking opts magic 0x%" PRIx64
-nbd_negotiate_options_check_option(uint32_t option, const char *name) "Checking option 0x%" PRIx32 " (%s)"
+nbd_negotiate_options_check_option(uint32_t option, const char *name) "Checking option %" PRIu32 " (%s)"
 nbd_negotiate_begin(void) "Beginning negotiation"
 nbd_negotiate_old_style(uint64_t size, unsigned flags) "advertising size %" PRIu64 " and flags 0x%x"
 nbd_negotiate_new_style_size_flags(uint64_t size, unsigned flags) "advertising size %" PRIu64 " and flags 0x%x"