Interview: Paolo Bonzini

Paolo Bonzini will give a talk about "Virtualization with KVM: bottom to top, past to future" at FOSDEM 2012.

Could you briefly introduce yourself?

I'm 31 years old and I've been working for Red Hat for almost 3 years. I worked for 1.5 years in Brno, where Red Hat has a large engineering site. Right now I work from my home office in Italy, near Milan.

I'm in the "virtualization platform" team, which basically covers QEMU and the KVM hypervisor. We work with the QEMU and Fedora communities, and of course our work is shipped with Red Hat Enterprise Linux. Right now I work almost exclusively on QEMU.

Before joining Red Hat I worked on several GNU programs (as a volunteer), including GCC; I'm still maintaining GNU sed, GNU grep and GNU Smalltalk.

What will your talk be about, exactly? What do you hope to accomplish by giving this talk? What do you expect?

I would like to show how strong and diverse a community has been built around KVM and virtualization. The KVM hypervisor, QEMU and libvirt are the foundation for an incredibly wide range of solutions for cloud computing (OpenStack), data center virtualization (oVirt), and desktop virtualization.

With my talk, I would like to give a general perspective on the whole stack and on the interaction between its components. So, I will talk about where we stand now with open source virtualization and what are the plans for the future.

But since virtualization is such a huge FOSS success story, I would also like to go over that story. I hope it's a pleasurable and instructive one.

In the five years after KVM entered the Linux kernel, it has become a very popular hypervisor and it has managed to attract a big ecosystem of tools around it. What's in your opinion the secret of KVM's success?

In short, I don't think there is a single secret. It's a combination of many factors (both technical and social). It also takes some luck, of course.

It's a hard question, and you will have to come to my talk to get a more complete answer.

What are the domains in which KVM and its accompanying tools are still lacking features compared to proprietary hypervisors? And in which domains is KVM clearly better in your opinion?

The number one missing feature is storage migration; that is, the ability to move the disk images from one disk to another seamlessly. Another is fault tolerance; people often ask about it, but it's not used very much (like driver domains, which KVM also lacks but Xen does support). A more interesting one is 3D acceleration for guests. All of these features are in the works to some extent.

KVM's architecture is clearly better when performance and scalability matters. Working in the Linux kernel community is not easy, but there is a lot of collaboration between people working on different fields and it's not a cliché that improvements in the Linux kernel will directly benefit KVM. Management software for KVM heavily relies on features of the kernel such as SELinux or cgroups.

In fact, KVM also helped improving other parts of Linux. My favorite example is Transparent Huge Pages. Andrea Arcangeli's aim for THP was to speed up virtualization, but in fact it will improve performance by 10% or even more even on unrelated workloads.

Which are the most exciting features we can expect to appear this year in KVM or its accompanying tools?

There's really a lot of exciting features, even only considering user-visible features and omitting internal improvements.

The next release of QEMU will greatly improve support for thin provisioning. It will let you clone an existing disk image instantly and "complete" it in the background while the virtual machine is running. This closes one of the gaps between the KVM stack and proprietary solutions.

The hypervisor itself will gain support for two new architectures: IBM's POWER, which so far supported only a proprietary hypervisor, and ARM. For x86, my colleague Gleb Natapov is working on virtualizing performance counters, so that you can do hardware-assisted profiling inside virtual machines.

These features are mostly interesting for server virtualization. Developers however also like to run virtualized operating systems locally, of course. For them, the new management console for GNOME ("Boxes") will provide an easy to use interface for desktop users.