[Qemu-devel] backing file support for vpc/vhd ?

[Philipp Hahn <hahn@univention.de>]

Hello,

while working on a Xen-VM I noticed that qemu-img does not support the backing file mechanism of vpc/vhd files, but Xens blktap2 does; it has a libvhd and some tools to create and modify vpc/vhd files:

tools/blktap2/vhd/lib/atomicio.c: BSD (2 clause)
tools/blktap2/vhd/lib/vhd-util-check.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-modify.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-uuid.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-scan.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-revert.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-snapshot.c: BSD (3 clause)
tools/blktap2/vhd/lib/libvhd.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-query.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-set-field.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-repair.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-fill.c: BSD (3 clause)
tools/blktap2/vhd/lib/libvhd-journal.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-read.c: BSD (3 clause)
tools/blktap2/vhd/lib/relative-path.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-coalesce.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-create.c: BSD (3 clause)
tools/blktap2/vhd/lib/vhd-util-resize.c: BSD (3 clause)
tools/blktap2/vhd/vhd-update.c: BSD (3 clause)
tools/blktap2/vhd/vhd-util.c: BSD (3 clause)

Is the lack of support for backing files in vpc/vjd in qemu just a question of time / interest, are there technical problems, or are there some political issues?

Sincerely
Philipp
-- 
Philipp Hahn           Open Source Software Engineer      hahn@univention.de
Univention GmbH        be open.                       fon: +49 421 22 232- 0
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