RHEL 7.5 Beta supports KVM on Z

The Red Hat Enterprise Linux 7.5 Beta ships with support for KVM on Z through the kernel-alt packages. This will essentially ship Linux kernel 4.14.
Here is the respective section from the release notes:

KVM virtualization is now supported on IBM z Systems. However, this feature is only available in the newly introduced user space based on kernel version 4.14, provided by the kernel-alt packages.

See here for further details.