diff --git a/docs/interop/nbd.txt b/docs/interop/nbd.txt
index f5ca25174a6..abaf4c28a96 100644
--- a/docs/interop/nbd.txt
+++ b/docs/interop/nbd.txt
@@ -69,3 +69,4 @@ NBD_CMD_BLOCK_STATUS for "qemu:dirty-bitmap:", NBD_CMD_CACHE
 NBD_CMD_FLAG_FAST_ZERO
 * 5.2: NBD_CMD_BLOCK_STATUS for "qemu:allocation-depth"
 * 7.1: NBD_FLAG_CAN_MULTI_CONN for shareable writable exports
+* 8.1: NBD_OPT_EXTENDED_HEADERS
diff --git a/include/block/nbd.h b/include/block/nbd.h
index 50626ab2744..d753fb8006f 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -87,13 +87,24 @@ typedef struct NBDStructuredReplyChunk {
     uint32_t length; /* length of payload */
 } QEMU_PACKED NBDStructuredReplyChunk;

+typedef struct NBDExtendedReplyChunk {
+    uint32_t magic;  /* NBD_EXTENDED_REPLY_MAGIC */
+    uint16_t flags;  /* combination of NBD_REPLY_FLAG_* */
+    uint16_t type;   /* NBD_REPLY_TYPE_* */
+    uint64_t handle; /* request handle */
+    uint64_t offset; /* request offset */
+    uint64_t length; /* length of payload */
+} QEMU_PACKED NBDExtendedReplyChunk;
+
 typedef union NBDReply {
     NBDSimpleReply simple;
     NBDStructuredReplyChunk structured;
+    NBDExtendedReplyChunk extended;
     struct {
-        /* @magic and @handle fields have the same offset and size both in
-         * simple reply and structured reply chunk, so let them be accessible
-         * without ".simple." or ".structured." specification
+        /*
+         * @magic and @handle fields have the same offset and size in all
+         * forms of replies, so let them be accessible without ".simple.",
+         * ".structured.", or ".extended." specifications.
          */
         uint32_t magic;
         uint32_t _skip;
@@ -126,15 +137,29 @@ typedef struct NBDStructuredError {
 typedef struct NBDStructuredMeta {
     /* header's length >= 12 (at least one extent) */
     uint32_t context_id;
-    /* extents follows */
+    /* NBDExtent extents[] follows, array length implied by header */
 } QEMU_PACKED NBDStructuredMeta;

-/* Extent chunk for NBD_REPLY_TYPE_BLOCK_STATUS */
+/* Extent array for NBD_REPLY_TYPE_BLOCK_STATUS */
 typedef struct NBDExtent {
     uint32_t length;
     uint32_t flags; /* NBD_STATE_* */
 } QEMU_PACKED NBDExtent;

+/* Header of NBD_REPLY_TYPE_BLOCK_STATUS_EXT */
+typedef struct NBDStructuredMetaExt {
+    /* header's length >= 24 (at least one extent) */
+    uint32_t context_id;
+    uint32_t count; /* header length must be count * 16 + 8 */
+    /* NBDExtentExt extents[count] follows */
+} QEMU_PACKED NBDStructuredMetaExt;
+
+/* Extent array for NBD_REPLY_TYPE_BLOCK_STATUS_EXT */
+typedef struct NBDExtentExt {
+    uint64_t length;
+    uint64_t flags; /* NBD_STATE_* */
+} QEMU_PACKED NBDExtentExt;
+
 /* Transmission (export) flags: sent from server to client during handshake,
    but describe what will happen during transmission */
 enum {
@@ -187,6 +212,7 @@ enum {
 #define NBD_OPT_STRUCTURED_REPLY  (8)
 #define NBD_OPT_LIST_META_CONTEXT (9)
 #define NBD_OPT_SET_META_CONTEXT  (10)
+#define NBD_OPT_EXTENDED_HEADERS  (11)

 /* Option reply types. */
 #define NBD_REP_ERR(value) ((UINT32_C(1) << 31) | (value))
@@ -204,6 +230,8 @@ enum {
 #define NBD_REP_ERR_UNKNOWN         NBD_REP_ERR(6)  /* Export unknown */
 #define NBD_REP_ERR_SHUTDOWN        NBD_REP_ERR(7)  /* Server shutting down */
 #define NBD_REP_ERR_BLOCK_SIZE_REQD NBD_REP_ERR(8)  /* Need INFO_BLOCK_SIZE */
+#define NBD_REP_ERR_TOO_BIG         NBD_REP_ERR(9)  /* Payload size overflow */
+#define NBD_REP_ERR_EXT_HEADER_REQD NBD_REP_ERR(10) /* Need extended headers */

 /* Info types, used during NBD_REP_INFO */
 #define NBD_INFO_EXPORT         0
@@ -212,12 +240,14 @@ enum {
 #define NBD_INFO_BLOCK_SIZE     3

 /* Request flags, sent from client to server during transmission phase */
-#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 */
-#define NBD_CMD_FLAG_FAST_ZERO  (1 << 4) /* fail if WRITE_ZEROES is not fast */
+#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 */
+#define NBD_CMD_FLAG_FAST_ZERO   (1 << 4) /* fail if WRITE_ZEROES is not fast */
+#define NBD_CMD_FLAG_PAYLOAD_LEN (1 << 5) \
+    /* length describes payload, not effect; only with ext header */

 /* Supported request types */
 enum {
@@ -243,12 +273,17 @@ enum {
  */
 #define NBD_MAX_STRING_SIZE 4096

-/* Transmission request structure */
+/* Two types of request structures, a given client will only use 1 */
 #define NBD_REQUEST_MAGIC           0x25609513
+#define NBD_EXTENDED_REQUEST_MAGIC  0x21e41c71

-/* Two types of reply structures */
+/*
+ * Three types of reply structures, but what a client expects depends
+ * on NBD_OPT_STRUCTURED_REPLY and NBD_OPT_EXTENDED_HEADERS.
+ */
 #define NBD_SIMPLE_REPLY_MAGIC      0x67446698
 #define NBD_STRUCTURED_REPLY_MAGIC  0x668e33ef
+#define NBD_EXTENDED_REPLY_MAGIC    0x6e8a278c

 /* Structured reply flags */
 #define NBD_REPLY_FLAG_DONE          (1 << 0) /* This reply-chunk is last */
@@ -256,12 +291,13 @@ enum {
 /* Structured reply types */
 #define NBD_REPLY_ERR(value)         ((1 << 15) | (value))

-#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)
+#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_BLOCK_STATUS_EXT  6
+#define NBD_REPLY_TYPE_ERROR             NBD_REPLY_ERR(1)
+#define NBD_REPLY_TYPE_ERROR_OFFSET      NBD_REPLY_ERR(2)

 /* Extent flags for base:allocation in NBD_REPLY_TYPE_BLOCK_STATUS */
 #define NBD_STATE_HOLE (1 << 0)
diff --git a/nbd/common.c b/nbd/common.c
index ddfe7d11837..137466defd2 100644
--- a/nbd/common.c
+++ b/nbd/common.c
@@ -79,6 +79,8 @@ const char *nbd_opt_lookup(uint32_t opt)
         return "list meta context";
     case NBD_OPT_SET_META_CONTEXT:
         return "set meta context";
+    case NBD_OPT_EXTENDED_HEADERS:
+        return "extended headers";
     default:
         return "<unknown>";
     }
@@ -112,6 +114,10 @@ const char *nbd_rep_lookup(uint32_t rep)
         return "server shutting down";
     case NBD_REP_ERR_BLOCK_SIZE_REQD:
         return "block size required";
+    case NBD_REP_ERR_TOO_BIG:
+        return "option payload too big";
+    case NBD_REP_ERR_EXT_HEADER_REQD:
+        return "extended headers required";
     default:
         return "<unknown>";
     }
@@ -170,7 +176,9 @@ const char *nbd_reply_type_lookup(uint16_t type)
     case NBD_REPLY_TYPE_OFFSET_HOLE:
         return "hole";
     case NBD_REPLY_TYPE_BLOCK_STATUS:
-        return "block status";
+        return "block status (32-bit)";
+    case NBD_REPLY_TYPE_BLOCK_STATUS_EXT:
+        return "block status (64-bit)";
     case NBD_REPLY_TYPE_ERROR:
         return "generic error";
     case NBD_REPLY_TYPE_ERROR_OFFSET:
