First, compared with RHEL 8, a lot of generic packages have been updated, of course. For example, RHEL 9 on IBM Z comes with:
- Linux kernel 5.14
- glibc 2.34
- gcc 11.2
- clang 13.0
- binutils 2.35
- s390utils 2.19
And of course all of these have been thoroughly tested during the past months, which is also the reason why RHEL sometimes does not ship the very latest bleeding edge versions of the upstream projects – thorough testing needs some time. But you can be sure that Red Hat also backported lots of selected upstream fixes and improvements e.g. for the kernel to their downstream packages, so this is very up to date and stable software here.
The new KVM virtualization stack
The first big news is: There is no need anymore to install the separate virt:av (“Advanced Virtualization”) module to get the latest and greatest virtualization features on IBM Z. Everything is packaged along with the main RHEL distribution for easier installation now and will be kept up-to-date there, with important new features like virtio-fs enabled by default. And of course, as with the latest releases of RHEL 8, there is also no limit to 4 guests anymore, so you don’t have to worry about the number of supported KVM guests (as long as your hardware can handle them).
The versions that will be shipped with RHEL 9.0 are:
- QEMU 6.2.0
- libvirt 8.0.0
- libguestfs 1.46.1
- virt-install 3.2.0
- libslirp 4.4.0
To answer the maybe most important question: Yes, this will also support the brand new IBM z16 mainframe already. Basic support for this new generation has already been added to QEMU 6.1.0 and kernel 5.14, and additional z16 features have been enabled by default in QEMU 6.2.0.
Another great new change is that it is now possible to
configure mediated devices directly with the virtualization CLI tools on IBM Z.
You can now add vfio-ap and vfio-ccw mediated devices to your KVM guests
virt-install, you can
also create a VM that uses an existing DASD mediated device as its primary disk.
Additionally, many small performance improvements (like the specification exception interpretation feature) and bug fixes have been backported to the RHEL 9 kernel and the userspace tools to give you a great virtualization experience with RHEL 9.
One more thing that is worth mentioning (though it is not specific to IBM Z), which you might have noticed by clicking on the links in the previous paragraphs already, there is another big change in RHEL 9: The development of the upcoming minor RHEL 9 releases (i.e. 9.1, 9.2, etc.) is now done in the public via the CentOS Stream repositories. That means you can not only peak on the work that will be integrated in the next 9.y release, you can now even directly participate in the development of these next release if you like! Isn’t that cool?
Anyway, no matter whether you are planning to participate or just want to use the software, please enjoy the new KVM virtualization stack on the mainframe!