host info:
qemu-kvm-rhev-2.3.0-1.el7.x86_64

(qemu) change ide1-cd0 cdrom1.iso 
(qemu) info block
ide1-cd0: cdrom1.iso (raw, read-only)
    Removable device: not locked, tray closed
    Cache mode:       writethrough
(qemu) block_set_io_throttle ide1-cd0 10000 0 0 0 0 0
(qemu) info block
ide1-cd0: cdrom1.iso (raw, read-only)
    Removable device: not locked, tray closed
    Cache mode:       writethrough
    I/O throttling:   bps=10000 bps_rd=0 bps_wr=0 bps_max=1000 bps_rd_max=0 bps_wr_max=0 iops=0 iops_rd=0 iops_wr=0 iops_max=0 iops_rd_max=0 iops_wr_max=0 iops_size=0

(qemu) change ide1-cd0 cdrom2.iso 
(qemu) info block
ide1-cd0: cdrom2.iso (raw, read-only)
    Removable device: not locked, tray closed
    Cache mode:       writethrough

Best Regards,
sluo

It seems the bug has been fixed on current rhel7.3, following is the test result:

Test sw versions:
Host kernel: 3.10.0-406.el7.x86_64
Qemu-kvm-rhev: qemu-kvm-rhev-2.6.0-2.el7.x86_64


Test steps:
1. Boot up a guest:

/usr/libexec/qemu-kvm -name rhel7.3 -enable-kvm -m 4G -smp 4 -uuid ae361e8d-288b-4e70-8783-bda0d450ce38 -nodefconfig --nodefaults -boot order=cd,menu=on -device virtio-scsi-pci,id=virtio_scsi_pci0,bus=pci.0,addr=03 -drive id=drive_image1,if=none,cache=none,snapshot=off,aio=native,format=qcow2,file=/home/rhel7.3,bps=512000,bps_max=1024000,throttling.bps-total-max-length=2 -device scsi-hd,id=image1,drive=drive_image1,bootindex=0 -drive file=/home/kvm_autotest_root/iso/linux/RHEL-7.2-20151030.0-Server-x86_64-dvd1.iso,media=cdrom,id=cdrom,if=none,bps=512000,bps_max=1024000,throttling.bps-total-max-length=2 -device ide-drive,drive=cdrom,bootindex=1 -vnc 0.0.0.0:14 -monitor stdio -netdev tap,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown,id=hostnet0 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=00:52:5a:30:2e:61,bus=pci.0,addr=0x7 -chardev socket,id=qmpmonitor1,path=/tmp/monitor1,server,nowait -mon chardev=qmpmonitor1,mode=control

2. Connect to the qmp monitor:

# nc -U /tmp/monitor1
{"QMP": {"version": {"qemu": {"micro": 94, "minor": 5, "major": 2}, "package": " (qemu-kvm-rhev-2.6.0-2.el7)"}, "capabilities": []}}
{"execute":"qmp_capabilities"}
{"return": {}}
{"execute":"query-block"}
{"return": [{"io-status": "ok", "device": "drive_image1", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "bps_max_length": 2, "image": {"virtual-size": 21474836480, "filename": "/home/rhel7.3", "cluster-size": 65536, "format": "qcow2", "actual-size": 1461919744, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false, "refcount-bits": 16, "corrupt": false}}, "dirty-flag": false}, "iops_wr": 0, "group": "", "ro": false, "node-name": "#block132", "backing_file_depth": 0, "drv": "qcow2", "bps_max": 1024000, "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 512000, "bps_rd": 0, "cache": {"no-flush": false, "direct": true, "writeback": true}, "file": "/home/rhel7.3", "encryption_key_missing": false}, "type": "unknown"}, {"io-status": "ok", "device": "cdrom", "locked": false, "removable": true, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "bps_max_length": 2, "image": {"virtual-size": 4043309056, "filename": "/home/kvm_autotest_root/iso/linux/RHEL-7.2-20151030.0-Server-x86_64-dvd1.iso", "format": "raw", "actual-size": 4051255296, "dirty-flag": false}, "iops_wr": 0, "group": "", "ro": true, "node-name": "#block371", "backing_file_depth": 0, "drv": "raw", "bps_max": 1024000, "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 512000, "bps_rd": 0, "cache": {"no-flush": false, "direct": false, "writeback": true}, "file": "/home/kvm_autotest_root/iso/linux/RHEL-7.2-20151030.0-Server-x86_64-dvd1.iso", "encryption_key_missing": false}, "tray_open": false, "type": "unknown"}]}
{"execute":"change","arguments":{"device":"cdrom","target":"/home/kvm_autotest_root/iso/linux/RHEL-7.2-20151027.3-Server-x86_64-dvd1.iso"}}
{"timestamp": {"seconds": 1463997311, "microseconds": 319521}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "cdrom", "tray-open": true}}
{"timestamp": {"seconds": 1463997311, "microseconds": 319672}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "cdrom", "tray-open": false}}
{"return": {}}
{"execute":"query-block"}
{"return": [{"io-status": "ok", "device": "drive_image1", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "bps_max_length": 2, "image": {"virtual-size": 21474836480, "filename": "/home/rhel7.3", "cluster-size": 65536, "format": "qcow2", "actual-size": 1461919744, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false, "refcount-bits": 16, "corrupt": false}}, "dirty-flag": false}, "iops_wr": 0, "group": "", "ro": false, "node-name": "#block132", "backing_file_depth": 0, "drv": "qcow2", "bps_max": 1024000, "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 512000, "bps_rd": 0, "cache": {"no-flush": false, "direct": true, "writeback": true}, "file": "/home/rhel7.3", "encryption_key_missing": false}, "type": "unknown"}, {"io-status": "ok", "device": "cdrom", "locked": true, "removable": true, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "bps_max_length": 2, "image": {"virtual-size": 4043309056, "filename": "/home/kvm_autotest_root/iso/linux/RHEL-7.2-20151027.3-Server-x86_64-dvd1.iso", "format": "raw", "actual-size": 4051255296, "dirty-flag": false}, "iops_wr": 0, "group": "", "ro": true, "node-name": "#block550", "backing_file_depth": 0, "drv": "raw", "bps_max": 1024000, "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 512000, "bps_rd": 0, "cache": {"no-flush": false, "direct": false, "writeback": true}, "file": "/home/kvm_autotest_root/iso/linux/RHEL-7.2-20151027.3-Server-x86_64-dvd1.iso", "encryption_key_missing": false}, "tray_open": false, "type": "unknown"}]}

3. Check io throttling status with qmp cmd "query-block"(Please check the qmp cmd output in step2)
4. Change cdrom iso in qmp(Please check the qmp cmd execution result in step2)
5. Check io throttling status again and it's found the io throttling parameters are the same as that in step3((Please check the qmp cmd output in step2)

Thank you for the update.

Based on this information, I'll be moving this to status: POST as per our qemu-kvm-rebase process for upcoming releases.

Thank you, Gu Nini.

Verify the bug on following sw versions:

kernel: 3.10.0-458.el7.x86_64
qemu-kvm-rhev: qemu-kvm-rhev-2.6.0-11.el7.x86_64

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.

https://rhn.redhat.com/errata/RHBA-2016-2673.html