diff --git a/include/block/block.h b/include/block/block.h
index 19b3ab9cb5e..947e8876cdd 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -115,19 +115,19 @@ typedef struct HDGeometry {
  * BDRV_BLOCK_ZERO: offset reads as zero
  * BDRV_BLOCK_OFFSET_VALID: an associated offset exists for accessing raw data
  * BDRV_BLOCK_ALLOCATED: the content of the block is determined by this
- *                       layer (short for DATA || ZERO), set by block layer
- * BDRV_BLOCK_EOF: the returned pnum covers through end of file for this layer
+ *                       layer rather than any backing, set by block layer
+ * BDRV_BLOCK_EOF: the returned pnum covers through end of file for this
+ *                 layer, set by block layer
  *
  * Internal flag:
  * BDRV_BLOCK_RAW: for use by passthrough drivers, such as raw, to request
  *                 that the block layer recompute the answer from the returned
  *                 BDS; must be accompanied by just BDRV_BLOCK_OFFSET_VALID.
  *
- * If BDRV_BLOCK_OFFSET_VALID is set, bits 9-62 (BDRV_BLOCK_OFFSET_MASK) of
- * the return value (old interface) or the entire map parameter (new
- * interface) represent the offset in the returned BDS that is allocated for
- * the corresponding raw data.  However, whether that offset actually
- * contains data also depends on BDRV_BLOCK_DATA, as follows:
+ * If BDRV_BLOCK_OFFSET_VALID is set, the map parameter represents the
+ * host offset within the returned BDS that is allocated for the
+ * corresponding raw guest data.  However, whether that offset
+ * actually contains data also depends on BDRV_BLOCK_DATA, as follows:
  *
  * DATA ZERO OFFSET_VALID
  *  t    t        t       sectors read as zero, returned file is zero at offset
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 5ea63f8fa8a..c93722b43a4 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -202,15 +202,25 @@ struct BlockDriver {
     /*
      * Building block for bdrv_block_status[_above] and
      * bdrv_is_allocated[_above].  The driver should answer only
-     * according to the current layer, and should not set
-     * BDRV_BLOCK_ALLOCATED, but may set BDRV_BLOCK_RAW.  See block.h
-     * for the meaning of _DATA, _ZERO, and _OFFSET_VALID.  The block
-     * layer guarantees input aligned to request_alignment, as well as
-     * non-NULL pnum and file.
+     * according to the current layer, and should only need to set
+     * BDRV_BLOCK_DATA, BDRV_BLOCK_ZERO, BDRV_BLOCK_OFFSET_VALID,
+     * and/or BDRV_BLOCK_RAW; if the current layer defers to a backing
+     * layer, the result should be 0 (and not BDRV_BLOCK_ZERO).  See
+     * block.h for the overall meaning of the bits.  As a hint, the
+     * flag want_zero is true if the caller cares more about precise
+     * mappings (favor accurate _OFFSET_VALID/_ZERO) or false for
+     * overall allocation (favor larger *pnum, perhaps by reporting
+     * _DATA instead of _ZERO).  The block layer guarantees input
+     * clamped to bdrv_getlength() and aligned to request_alignment,
+     * as well as non-NULL pnum, map, and file; in turn, the driver
+     * must return an error or set pnum to an aligned non-zero value.
      */
     int64_t coroutine_fn (*bdrv_co_get_block_status)(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, int *pnum,
         BlockDriverState **file);
+    int coroutine_fn (*bdrv_co_block_status)(BlockDriverState *bs,
+        bool want_zero, int64_t offset, int64_t bytes, int64_t *pnum,
+        int64_t *map, BlockDriverState **file);

     /*
      * Invalidate any cached meta-data.
diff --git a/block/io.c b/block/io.c
index 89d0745e952..b00c7e2e2c0 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1899,10 +1899,10 @@ int64_t coroutine_fn bdrv_co_get_block_status_from_backing(BlockDriverState *bs,
  * Drivers not implementing the functionality are assumed to not support
  * backing files, hence all their sectors are reported as allocated.
  *
- * If 'want_zero' is true, the caller is querying for mapping purposes,
- * and the result should include BDRV_BLOCK_OFFSET_VALID and
- * BDRV_BLOCK_ZERO where possible; otherwise, the result may omit those
- * bits particularly if it allows for a larger value in 'pnum'.
+ * If 'want_zero' is true, the caller is querying for mapping
+ * purposes, with a focus on valid BDRV_BLOCK_OFFSET_VALID, _DATA, and
+ * _ZERO where possible; otherwise, the result favors larger 'pnum',
+ * with a focus on accurate BDRV_BLOCK_ALLOCATED.
  *
  * If 'offset' is beyond the end of the disk image the return value is
  * BDRV_BLOCK_EOF and 'pnum' is set to 0.
@@ -1959,7 +1959,7 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,

     /* Must be non-NULL or bdrv_getlength() would have failed */
     assert(bs->drv);
-    if (!bs->drv->bdrv_co_get_block_status) {
+    if (!bs->drv->bdrv_co_get_block_status && !bs->drv->bdrv_co_block_status) {
         *pnum = bytes;
         ret = BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED;
         if (offset + bytes == total_size) {
@@ -1976,13 +1976,14 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
     bdrv_inc_in_flight(bs);

     /* Round out to request_alignment boundaries */
-    /* TODO: until we have a byte-based driver callback, we also have to
-     * round out to sectors, even if that is bigger than request_alignment */
-    align = MAX(bs->bl.request_alignment, BDRV_SECTOR_SIZE);
+    align = bs->bl.request_alignment;
+    if (bs->drv->bdrv_co_get_block_status && align < BDRV_SECTOR_SIZE) {
+        align = BDRV_SECTOR_SIZE;
+    }
     aligned_offset = QEMU_ALIGN_DOWN(offset, align);
     aligned_bytes = ROUND_UP(offset + bytes, align) - aligned_offset;

-    {
+    if (bs->drv->bdrv_co_get_block_status) {
         int count; /* sectors */
         int64_t longret;

@@ -2007,6 +2008,15 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
         }
         ret = longret & ~BDRV_BLOCK_OFFSET_MASK;
         *pnum = count * BDRV_SECTOR_SIZE;
+    } else {
+        ret = bs->drv->bdrv_co_block_status(bs, want_zero, aligned_offset,
+                                            aligned_bytes, pnum, &local_map,
+                                            &local_file);
+        if (ret < 0) {
+            *pnum = 0;
+            goto out;
+        }
+        assert(*pnum); /* The block driver must make progress */
     }

     /*
