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>
Formats supporting backing chain such as qed, vmdk, don't have any other
parameters than the backing store and 'qcow' has only encryption params
which will be tested extra. Add this test case so they are covered since
any further test cases will mainly care about 'qcow2' and 'raw'.
The top level disk image would generate the following '-drive' cmdline:
-drive file=/var/lib/libvirt/images/a,format=qed,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>
