Re: [libvirt] [PATCH 2/9] qemu: domain: Reject copy_on_read for read-only disks

The sectors read from the backing image need to be written to the top level image. If a disk is marked read-only the image can't be written. QEMU handled that by disabling copy_on_read and reporting a warning: -drive file=/var/lib/libvirt/images/c,format=qcow2,if=none, id=drive-scsi0-0-1,readonly=on,copy-on-read=on: warning: disabling copy-on-read on read-only drive Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- src/qemu/qemu_domain.c | 7 +++++++ 1 file changed, 7 insertions(+)