diff --git a/block/blkdebug.c b/block/blkdebug.c
index e686cd9..742b4a3 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -684,7 +684,7 @@
 }
 
 static int coroutine_fn blkdebug_co_pwrite_zeroes(BlockDriverState *bs,
-                                                  int64_t offset, int bytes,
+                                                  int64_t offset, int64_t bytes,
                                                   BdrvRequestFlags flags)
 {
     uint32_t align = MAX(bs->bl.request_alignment,
diff --git a/block/blklogwrites.c b/block/blklogwrites.c
index ca174ab..d7ae64c 100644
--- a/block/blklogwrites.c
+++ b/block/blklogwrites.c
@@ -468,8 +468,8 @@
 }
 
 static int coroutine_fn
-blk_log_writes_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int bytes,
-                                BdrvRequestFlags flags)
+blk_log_writes_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
+                                int64_t bytes, BdrvRequestFlags flags)
 {
     return blk_log_writes_co_log(bs, offset, bytes, NULL, flags,
                                  blk_log_writes_co_do_file_pwrite_zeroes, 0,
diff --git a/block/blkreplay.c b/block/blkreplay.c
index 7ba62dc..89d74a3 100644
--- a/block/blkreplay.c
+++ b/block/blkreplay.c
@@ -94,7 +94,7 @@
 }
 
 static int coroutine_fn blkreplay_co_pwrite_zeroes(BlockDriverState *bs,
-    int64_t offset, int bytes, BdrvRequestFlags flags)
+    int64_t offset, int64_t bytes, BdrvRequestFlags flags)
 {
     uint64_t reqid = blkreplay_next_id();
     int ret = bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index 74360b4..d210e87 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -75,7 +75,7 @@
 }
 
 static int coroutine_fn cbw_co_pwrite_zeroes(BlockDriverState *bs,
-        int64_t offset, int bytes, BdrvRequestFlags flags)
+        int64_t offset, int64_t bytes, BdrvRequestFlags flags)
 {
     int ret = cbw_do_copy_before_write(bs, offset, bytes, flags);
     if (ret < 0) {
diff --git a/block/copy-on-read.c b/block/copy-on-read.c
index b2ec36b..f83dd83 100644
--- a/block/copy-on-read.c
+++ b/block/copy-on-read.c
@@ -193,7 +193,7 @@
 
 
 static int coroutine_fn cor_co_pwrite_zeroes(BlockDriverState *bs,
-                                             int64_t offset, int bytes,
+                                             int64_t offset, int64_t bytes,
                                              BdrvRequestFlags flags)
 {
     return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
diff --git a/block/file-posix.c b/block/file-posix.c
index ed71e8d..f375070 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2972,7 +2972,7 @@
 }
 
 static int coroutine_fn
-raw_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int bytes,
+raw_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int64_t bytes,
                      BdrvRequestFlags flags, bool blkdev)
 {
     BDRVRawState *s = bs->opaque;
@@ -3040,7 +3040,7 @@
 
 static int coroutine_fn raw_co_pwrite_zeroes(
     BlockDriverState *bs, int64_t offset,
-    int bytes, BdrvRequestFlags flags)
+    int64_t bytes, BdrvRequestFlags flags)
 {
     return raw_do_pwrite_zeroes(bs, offset, bytes, flags, false);
 }
@@ -3605,7 +3605,7 @@
 }
 
 static coroutine_fn int hdev_co_pwrite_zeroes(BlockDriverState *bs,
-    int64_t offset, int bytes, BdrvRequestFlags flags)
+    int64_t offset, int64_t bytes, BdrvRequestFlags flags)
 {
     int rc;
 
diff --git a/block/filter-compress.c b/block/filter-compress.c
index 505822a..fb85686 100644
--- a/block/filter-compress.c
+++ b/block/filter-compress.c
@@ -86,7 +86,7 @@
 
 
 static int coroutine_fn compress_co_pwrite_zeroes(BlockDriverState *bs,
-                                                  int64_t offset, int bytes,
+                                                  int64_t offset, int64_t bytes,
                                                   BdrvRequestFlags flags)
 {
     return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
diff --git a/block/gluster.c b/block/gluster.c
index d51938e..4e3c9cd 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -1003,19 +1003,19 @@
 #ifdef CONFIG_GLUSTERFS_ZEROFILL
 static coroutine_fn int qemu_gluster_co_pwrite_zeroes(BlockDriverState *bs,
                                                       int64_t offset,
-                                                      int size,
+                                                      int64_t bytes,
                                                       BdrvRequestFlags flags)
 {
     int ret;
     GlusterAIOCB acb;
     BDRVGlusterState *s = bs->opaque;
 
-    acb.size = size;
+    acb.size = bytes;
     acb.ret = 0;
     acb.coroutine = qemu_coroutine_self();
     acb.aio_context = bdrv_get_aio_context(bs);
 
-    ret = glfs_zerofill_async(s->fd, offset, size, gluster_finish_aiocb, &acb);
+    ret = glfs_zerofill_async(s->fd, offset, bytes, gluster_finish_aiocb, &acb);
     if (ret < 0) {
         return -errno;
     }
diff --git a/block/iscsi.c b/block/iscsi.c
index 01fdd17..74ff7e3 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -427,14 +427,14 @@
     return sector * BDRV_SECTOR_SIZE / iscsilun->block_size;
 }
 
-static bool is_byte_request_lun_aligned(int64_t offset, int count,
+static bool is_byte_request_lun_aligned(int64_t offset, int64_t bytes,
                                         IscsiLun *iscsilun)
 {
-    if (offset % iscsilun->block_size || count % iscsilun->block_size) {
+    if (offset % iscsilun->block_size || bytes % iscsilun->block_size) {
         error_report("iSCSI misaligned request: "
                      "iscsilun->block_size %u, offset %" PRIi64
-                     ", count %d",
-                     iscsilun->block_size, offset, count);
+                     ", bytes %" PRIi64,
+                     iscsilun->block_size, offset, bytes);
         return false;
     }
     return true;
@@ -1202,12 +1202,12 @@
 
 static int
 coroutine_fn iscsi_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
-                                    int bytes, BdrvRequestFlags flags)
+                                    int64_t bytes, BdrvRequestFlags flags)
 {
     IscsiLun *iscsilun = bs->opaque;
     struct IscsiTask iTask;
     uint64_t lba;
-    uint32_t nb_blocks;
+    uint64_t nb_blocks;
     bool use_16_for_ws = iscsilun->use_16_for_rw;
     int r = 0;
 
@@ -1247,11 +1247,21 @@
     iscsi_co_init_iscsitask(iscsilun, &iTask);
 retry:
     if (use_16_for_ws) {
+        /*
+         * iscsi_writesame16_task num_blocks argument is uint32_t. We rely here
+         * on our max_pwrite_zeroes limit.
+         */
+        assert(nb_blocks <= UINT32_MAX);
         iTask.task = iscsi_writesame16_task(iscsilun->iscsi, iscsilun->lun, lba,
                                             iscsilun->zeroblock, iscsilun->block_size,
                                             nb_blocks, 0, !!(flags & BDRV_REQ_MAY_UNMAP),
                                             0, 0, iscsi_co_generic_cb, &iTask);
     } else {
+        /*
+         * iscsi_writesame10_task num_blocks argument is uint16_t. We rely here
+         * on our max_pwrite_zeroes limit.
+         */
+        assert(nb_blocks <= UINT16_MAX);
         iTask.task = iscsi_writesame10_task(iscsilun->iscsi, iscsilun->lun, lba,
                                             iscsilun->zeroblock, iscsilun->block_size,
                                             nb_blocks, 0, !!(flags & BDRV_REQ_MAY_UNMAP),
@@ -2071,10 +2081,10 @@
         bs->bl.pdiscard_alignment = iscsilun->block_size;
     }
 
-    if (iscsilun->bl.max_ws_len < 0xffffffff / block_size) {
-        bs->bl.max_pwrite_zeroes =
-            iscsilun->bl.max_ws_len * iscsilun->block_size;
-    }
+    bs->bl.max_pwrite_zeroes =
+        MIN_NON_ZERO(iscsilun->bl.max_ws_len * iscsilun->block_size,
+                     max_xfer_len * iscsilun->block_size);
+
     if (iscsilun->lbp.lbpws) {
         bs->bl.pwrite_zeroes_alignment =
             iscsilun->bl.opt_unmap_gran * iscsilun->block_size;
diff --git a/block/mirror.c b/block/mirror.c
index c4c623c..fab7508 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -1501,7 +1501,7 @@
 }
 
 static int coroutine_fn bdrv_mirror_top_pwrite_zeroes(BlockDriverState *bs,
-    int64_t offset, int bytes, BdrvRequestFlags flags)
+    int64_t offset, int64_t bytes, BdrvRequestFlags flags)
 {
     return bdrv_mirror_top_do_write(bs, MIRROR_METHOD_ZERO, offset, bytes, NULL,
                                     flags);
diff --git a/block/nbd.c b/block/nbd.c
index caee396..c0c479a 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -1407,15 +1407,17 @@
 }
 
 static int nbd_client_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
-                                       int bytes, BdrvRequestFlags flags)
+                                       int64_t bytes, BdrvRequestFlags flags)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
     NBDRequest request = {
         .type = NBD_CMD_WRITE_ZEROES,
         .from = offset,
-        .len = bytes,
+        .len = bytes,  /* .len is uint32_t actually */
     };
 
+    assert(bytes <= UINT32_MAX); /* rely on max_pwrite_zeroes */
+
     assert(!(s->info.flags & NBD_FLAG_READ_ONLY));
     if (!(s->info.flags & NBD_FLAG_SEND_WRITE_ZEROES)) {
         return -ENOTSUP;
diff --git a/block/nvme.c b/block/nvme.c
index c44db18..2e0fd9e 100644
--- a/block/nvme.c
+++ b/block/nvme.c
@@ -1296,19 +1296,29 @@
 
 static coroutine_fn int nvme_co_pwrite_zeroes(BlockDriverState *bs,
                                               int64_t offset,
-                                              int bytes,
+                                              int64_t bytes,
                                               BdrvRequestFlags flags)
 {
     BDRVNVMeState *s = bs->opaque;
     NVMeQueuePair *ioq = s->queues[INDEX_IO(0)];
     NVMeRequest *req;
-
-    uint32_t cdw12 = ((bytes >> s->blkshift) - 1) & 0xFFFF;
+    uint32_t cdw12;
 
     if (!s->supports_write_zeroes) {
         return -ENOTSUP;
     }
 
+    if (bytes == 0) {
+        return 0;
+    }
+
+    cdw12 = ((bytes >> s->blkshift) - 1) & 0xFFFF;
+    /*
+     * We should not lose information. pwrite_zeroes_alignment and
+     * max_pwrite_zeroes guarantees it.
+     */
+    assert(((cdw12 + 1) << s->blkshift) == bytes);
+
     NvmeCmd cmd = {
         .opcode = NVME_CMD_WRITE_ZEROES,
         .nsid = cpu_to_le32(s->nsid),
@@ -1472,6 +1482,14 @@
     bs->bl.opt_mem_alignment = s->page_size;
     bs->bl.request_alignment = s->page_size;
     bs->bl.max_transfer = s->max_transfer;
+
+    /*
+     * Look at nvme_co_pwrite_zeroes: after shift and decrement we should get
+     * at most 0xFFFF
+     */
+    bs->bl.max_pwrite_zeroes = 1ULL << (s->blkshift + 16);
+    bs->bl.pwrite_zeroes_alignment = MAX(bs->bl.request_alignment,
+                                         1UL << s->blkshift);
 }
 
 static void nvme_detach_aio_context(BlockDriverState *bs)
diff --git a/block/preallocate.c b/block/preallocate.c
index c19885a..99e28d9 100644
--- a/block/preallocate.c
+++ b/block/preallocate.c
@@ -337,7 +337,7 @@
 }
 
 static int coroutine_fn preallocate_co_pwrite_zeroes(BlockDriverState *bs,
-        int64_t offset, int bytes, BdrvRequestFlags flags)
+        int64_t offset, int64_t bytes, BdrvRequestFlags flags)
 {
     bool want_merge_zero =
         !(flags & ~(BDRV_REQ_ZERO_WRITE | BDRV_REQ_NO_FALLBACK));
diff --git a/block/qcow2.c b/block/qcow2.c
index 520ae37..4b2e869 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3941,7 +3941,7 @@
 }
 
 static coroutine_fn int qcow2_co_pwrite_zeroes(BlockDriverState *bs,
-    int64_t offset, int bytes, BdrvRequestFlags flags)
+    int64_t offset, int64_t bytes, BdrvRequestFlags flags)
 {
     int ret;
     BDRVQcow2State *s = bs->opaque;
diff --git a/block/qed.c b/block/qed.c
index f45c640..558d364 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -582,6 +582,7 @@
     BDRVQEDState *s = bs->opaque;
 
     bs->bl.pwrite_zeroes_alignment = s->header.cluster_size;
+    bs->bl.max_pwrite_zeroes = QEMU_ALIGN_DOWN(INT_MAX, s->header.cluster_size);
 }
 
 /* We have nothing to do for QED reopen, stubs just return
@@ -1397,7 +1398,7 @@
 
 static int coroutine_fn bdrv_qed_co_pwrite_zeroes(BlockDriverState *bs,
                                                   int64_t offset,
-                                                  int bytes,
+                                                  int64_t bytes,
                                                   BdrvRequestFlags flags)
 {
     BDRVQEDState *s = bs->opaque;
@@ -1408,6 +1409,12 @@
      */
     QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, NULL, bytes);
 
+    /*
+     * QED is not prepared for 63bit write-zero requests, so rely on
+     * max_pwrite_zeroes.
+     */
+    assert(bytes <= INT_MAX);
+
     /* Fall back if the request is not aligned */
     if (qed_offset_into_cluster(s, offset) ||
         qed_offset_into_cluster(s, bytes)) {
diff --git a/block/quorum.c b/block/quorum.c
index f4b76ea..c28dda7 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -746,7 +746,7 @@
 }
 
 static int quorum_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
-                                   int bytes, BdrvRequestFlags flags)
+                                   int64_t bytes, BdrvRequestFlags flags)
 
 {
     return quorum_co_pwritev(bs, offset, bytes, NULL,
diff --git a/block/raw-format.c b/block/raw-format.c
index 3451378..a2485926 100644
--- a/block/raw-format.c
+++ b/block/raw-format.c
@@ -289,7 +289,7 @@
 }
 
 static int coroutine_fn raw_co_pwrite_zeroes(BlockDriverState *bs,
-                                             int64_t offset, int bytes,
+                                             int64_t offset, int64_t bytes,
                                              BdrvRequestFlags flags)
 {
     int ret;
diff --git a/block/rbd.c b/block/rbd.c
index efc0835..053eb8e 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -1205,9 +1205,9 @@
 #ifdef LIBRBD_SUPPORTS_WRITE_ZEROES
 static int
 coroutine_fn qemu_rbd_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
-                                      int count, BdrvRequestFlags flags)
+                                       int64_t bytes, BdrvRequestFlags flags)
 {
-    return qemu_rbd_start_co(bs, offset, count, NULL, flags,
+    return qemu_rbd_start_co(bs, offset, bytes, NULL, flags,
                              RBD_AIO_WRITE_ZEROES);
 }
 #endif
diff --git a/block/throttle.c b/block/throttle.c
index 1330e84..c13fe90 100644
--- a/block/throttle.c
+++ b/block/throttle.c
@@ -135,7 +135,7 @@
 }
 
 static int coroutine_fn throttle_co_pwrite_zeroes(BlockDriverState *bs,
-                                                  int64_t offset, int bytes,
+                                                  int64_t offset, int64_t bytes,
                                                   BdrvRequestFlags flags)
 {
     ThrottleGroupMember *tgm = bs->opaque;
diff --git a/block/trace-events b/block/trace-events
index 983dd54..d8a0856 100644
--- a/block/trace-events
+++ b/block/trace-events
@@ -80,8 +80,8 @@
 qcow2_writev_start_part(void *co) "co %p"
 qcow2_writev_done_part(void *co, int cur_bytes) "co %p cur_bytes %d"
 qcow2_writev_data(void *co, uint64_t offset) "co %p offset 0x%" PRIx64
-qcow2_pwrite_zeroes_start_req(void *co, int64_t offset, int count) "co %p offset 0x%" PRIx64 " count %d"
-qcow2_pwrite_zeroes(void *co, int64_t offset, int count) "co %p offset 0x%" PRIx64 " count %d"
+qcow2_pwrite_zeroes_start_req(void *co, int64_t offset, int64_t bytes) "co %p offset 0x%" PRIx64 " bytes %" PRId64
+qcow2_pwrite_zeroes(void *co, int64_t offset, int64_t bytes) "co %p offset 0x%" PRIx64 " bytes %" PRId64
 qcow2_skip_cow(void *co, uint64_t offset, int nb_clusters) "co %p offset 0x%" PRIx64 " nb_clusters %d"
 
 # qcow2-cluster.c
diff --git a/block/vmdk.c b/block/vmdk.c
index 8d49e54..fb4cc9d 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -2109,7 +2109,7 @@
 
 static int coroutine_fn vmdk_co_pwrite_zeroes(BlockDriverState *bs,
                                               int64_t offset,
-                                              int bytes,
+                                              int64_t bytes,
                                               BdrvRequestFlags flags)
 {
     int ret;
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 24958ac..d518703 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -301,7 +301,7 @@
      * will be called instead.
      */
     int coroutine_fn (*bdrv_co_pwrite_zeroes)(BlockDriverState *bs,
-        int64_t offset, int bytes, BdrvRequestFlags flags);
+        int64_t offset, int64_t bytes, BdrvRequestFlags flags);
     int coroutine_fn (*bdrv_co_pdiscard)(BlockDriverState *bs,
         int64_t offset, int bytes);