Moving to qemu-kvm component as we track 7.0.z qemu-kvm-rhev with it. qemu-kvm-rhev component is used for 7.1 and newer only.

Fix included in qemu-kvm-1.5.3-60.el7_0.10

Verify with qemu-kvm-rhev-1.5.3-60.el7_0.10.x86_64:

1. test "backing-file" option of block stream:

with Base->sn1->sn2->sn3:

absolute path:

{ "execute": "block-stream", "arguments": { "device": "drive-virtio-disk0", "base": "/root/nfs/RHEL-Server-7.0-64-virtio.qcow2", "speed": 1000000000,  "backing-file": "/root/nfs/RHEL-Server-7.0-64-virtio.qcow2"} }

info block:

(qemu) info block
drive-virtio-disk0: removable=0 io-status=ok file=/root/sn3 backing_file=/root/nfs/RHEL-Server-7.0-64-virtio.qcow2 backing_file_depth=1 ro=0 drv=qcow2 encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0

relative path:

{ "execute": "block-stream", "arguments": { "device": "drive-virtio-disk0", "base": "/root/nfs/RHEL-Server-7.0-64-virtio.qcow2", "speed": 1000000000,  "backing-file": "./nfs/RHEL-Server-7.0-64-virtio.qcow2"} }

(qemu) info block
drive-virtio-disk0: removable=0 io-status=ok file=/root/sn3 backing_file=./nfs/RHEL-Server-7.0-64-virtio.qcow2 backing_file_depth=1 ro=0 drv=qcow2 encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0


2. test "backing-file" option of block commit:

with Base->sn1->sn2->sn3:

absolute path:

{ "execute": "block-commit", "arguments": { "device": "drive-virtio-disk0", "base": "/root/nfs/RHEL-Server-7.0-64-virtio.qcow2", "top": "/root/sn2", "speed": 1000000000, "backing-file": "/root/nfs/RHEL-Server-7.0-64-virtio.qcow2"} }

(qemu) info block
drive-virtio-disk0: removable=0 io-status=ok file=/root/sn3 backing_file=/root/nfs/RHEL-Server-7.0-64-virtio.qcow2 backing_file_depth=1 ro=0 drv=qcow2 encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0

relative path:

{ "execute": "block-commit", "arguments": { "device": "drive-virtio-disk0", "base": "/root/nfs/RHEL-Server-7.0-64-virtio.qcow2", "top": "/root/sn2", "speed": 1000000000, "backing-file": "./nfs/RHEL-Server-7.0-64-virtio.qcow2"} }

(qemu) info block
drive-virtio-disk0: removable=0 io-status=ok file=/root/sn3 backing_file=./nfs/RHEL-Server-7.0-64-virtio.qcow2 backing_file_depth=1 ro=0 drv=qcow2 encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0

3. the NULL function "__com.redhat_change-backing-file":

{ "execute": "__com.redhat_change-backing-file", "arguments": { "device": "drive-virtio-disk0", "image-node-name": "123",  "backing-file": "./nfs/RHEL-Server-7.0-64-virtio.qcow2"} }
{"error": {"class": "GenericError", "desc": "this feature or command is not currently supported"}}


Verified.

See bug 1150322 for the libvirt counterpart needed to drive this.

Please refer to https://bugzilla.redhat.com/show_bug.cgi?id=1150322#c4 for the libvirt test result.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2014-1670.html