Comment 2 for bug 1659225

There is support in qemu and the linux kernel:

[root@s4lp3 ~]# cat /etc/kvmibm-release
KVM for IBM z Systems release 1.1.3-beta4.3 (Z)

[root@s4lp3 ~]# ldd /usr/bin/qemu-system-s390x | grep rbd
 librbd.so.1 => /lib64/librbd.so.1 (0x000003ff8c580000)

[root@s4lp3 ~]# repoquery --requires --recursive --resolve qemu-kvm | grep rbd
librbd1-1:10.2.2-2.el7_2.kvmibm1_1_3.2.s390x

[root@s4lp3 ~]# qemu-kvm --drive format=? |& grep rbd
Supported formats: dmg ssh rbd tftp ftps ftp https http iscsi luks sheepdog nbd null-aio null-co host_cdrom host_device file blkreplay blkverify blkdebug parallels quorum vhdx qed qcow2 vvfat vpc bochs cloop vmdk vdi qcow raw

[root@s4lp3 ~]# stat /lib/modules/4.4.0-40.60.el7_2.kvmibm1_1_3.2.s390x/kernel/drivers/block/rbd.ko | grep file
  Size: 198462 Blocks: 392 IO Block: 4096 regular file

However, there is no support in libvirt:

[root@s4lp3 ~]# virsh --version=long
Virsh command line tool of libvirt 2.3.0
See web site at http://libvirt.org/

Compiled with support for:
 Hypervisors: QEMU/KVM LXC ESX Test
 Networking: Remote Network Bridging Interface netcf Nwfilter VirtualPort
 Storage: Dir Disk Filesystem SCSI Multipath iSCSI LVM
 Miscellaneous: Daemon Nodedev SELinux Secrets Debug DTrace Readline Modular

On a system with RBD compiled it should be listed:
Compiled with support for:
 Hypervisors: QEMU/KVM LXC UML Xen LibXL OpenVZ VMWare VirtualBox ESX Test
 Networking: Remote Network Bridging Interface netcf Nwfilter VirtualPort
 Storage: Dir Disk Filesystem SCSI Multipath iSCSI LVM RBD Sheepdog ZFS
 Miscellaneous: Daemon Nodedev AppArmor Secrets Debug Readline Modular

Sources (just to make sure):
https://libvirt.org/git/?p=libvirt.git;a=blob;f=tools/virsh.c;h=7eb51ab7dc40c93202cb101fc2c3b7bfd6979734;hb=HEAD#l639