To allow using -blockdev with blockjobs QEMU needs to reopen files in
read-write mode when modifying the backing chain. To achieve this we
need to use 'auto-read-only' for the backing files rather than the
normal 'read-only' property. That way qemu knows that the files need to
be reopened.
Note that the format drivers (e.g. qcow2) are still opened with the
read-only property enabled when being a member of the backing chain
since they are supposed to be immutable unless a block job is started.
QEMU v4.0 (since commit 23dece19da4) allows also dynamic behaviour for
auto-read-only which allows us to use sVirt as we only grant write
permissions to files when doing a blockjob.
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Reference the storage via node name rather than inlining it. This is
the approach that will be used with -blockdev/blockdev-add since it
allows more control and is more future proof.
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>
Add tests for backing chain handling, including a very long chain which
is fully specified in the XML and an unterminated chain.
The top level disk image would generate the following '-drive':
file-qcow2-backing-chain-encryption.xml:
-drive file=/var/lib/libvirt/images/a,encrypt.format=luks,
encrypt.key-secret=node-b-f-encalias,format=qcow2,if=none,id=drive-dummy
-device virtio-blk-pci,scsi=off,drive=drive-dummy,id=dummy
file-qcow2-backing-chain-noopts.xml:
-drive file=/var/lib/libvirt/images/rhel7.3.1507297895,format=qcow2,if=none,id=drive-dummy
-device virtio-blk-pci,scsi=off,drive=drive-dummy,id=dummy
file-qcow2-backing-chain-unterminated.xml:
-drive file=/var/lib/libvirt/images/rhel7.3.1507297895,format=qcow2,if=none,id=drive-dummy
-device virtio-blk-pci,scsi=off,drive=drive-dummy,id=dummy
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>
