docs/interop/qcow2.rst

54                     the maximum L1 table size.  With a 2 MB cluster
59                     table layouts limit an image to no more than 64 PB
70                     Number of entries in the active L1 table
73                     Offset into the image file at which the active L1 table
77                     Offset into the image file at which the refcount table
81                     Number of clusters that the refcount table occupies
87                     Offset into the image file at which the snapshot table
127                                 L2 table entries use an extended format that
168                                 of only setting the zero flag in the L2 table
258                         0x6803f857 - Feature name table
294 Feature name table
297 The feature name table is an optional header extension that contains the name
302 The number of entries in the feature name table is determined by the length of
461 The refcounts are managed in a two-level table. The first level is called
462 refcount table and has a variable size (which is stored in the header). The
463 refcount table can cover multiple clusters, however it needs to be contiguous
469 Although a large enough refcount table can reserve clusters past 64 PB
476     table size.  With a 2 MB cluster size and a default refcount_order of
492 Refcount table entry::
515 guest clusters to host clusters. They are called L1 and L2 table.
517 The L1 table has a variable size (stored in the header) and may use multiple
522 size; for a given L1 table size, a larger cluster size is required for
546 L1 table entry::
551                     table starts. Must be aligned to a cluster boundary. If the
552                     offset is 0, the L2 table and all clusters described by this
553                     L2 table are unallocated.
557              63:    0 for an L2 table that is unused or requires COW, 1 if its
559                     in the active L1 table.
561 L2 table entry::
571                     that are reachable from the active L1 table.
636 The size of an extended L2 entry is 128 bits so the number of entries per table
643 The first 64 bits have the same format as the standard L2 table entry described
683 switch the active L1 table, so that a different set of host clusters are
686 When creating a snapshot, the L1 table should be copied and the refcount of all
687 L2 tables and clusters reachable from this L1 table must be increased, so that
690 When loading a snapshot, bit 63 of all entries in the new active L1 table and
691 all L2 tables referenced by it must be reconstructed from the refcount table
694 A directory of all snapshots is stored in the snapshot table, a contiguous area
696 fields snapshots_offset and nb_snapshots. The entries of the snapshot table
699 Snapshot table entry::
701     Byte 0 -  7:    Offset into the image file at which the L1 table for the
704          8 - 11:    Number of entries in the L1 table of the snapshots
721                     described by first L1 table entry that doesn't describe a
726         36 - 39:    Size of extra data in the table entry (used for future
731                     table entry):
751         variable:   Padding to round up the snapshot table entry size to the
786                     Offset into the image file at which the bitmap table
791                     Number of entries in the bitmap table of the bitmap.
864 Bitmap table
869 bitmap data to host clusters. This structure is called the bitmap table.
871 Each bitmap table has a variable size (stored in the bitmap directory entry)
875 Structure of a bitmap table entry::
896 bitmap table. Given an offset (in bytes) into the bitmap data, the offset into
903 This offset is not defined if bits 9 - 55 of bitmap table entry are zero (see