Thursday, November 9, 2017

Notes from KVM Forum 2017

KVM Forum 2017 took place in Prague Oct 25 - 27 and I had the pleasure of attending. Let me share some of my notes and observations (not exhaustive in any way).

General notes

KVM Forum this year was quite large, but with enough space to sit down and talk to others (or do some hacking). As always, the hallway track was great to meet some people (both old acquaintances and folks you never met in real life before) and to discuss things face-to-face that would take more time done via the mailing lists or IRC.

The first day featured a single track (shared with OSS Europe), and also the invitation-only QEMU summit in the morning (minutes will be posted to qemu-devel). Days two and three were dual-track except for the first sessions. Obviously, this means I was only able to see a subset of sessions (and one also needs a break sometimes...); fortunately, videos are slowly making their way unto youtube (check here for updates).


Christian Bornträger presented the KVM status, Paolo Bonzini the QEMU status and Peter Krempa the libvirt status. We seem to have a healthy development community, and interesting new topics still come up.


I listened with interest to Christoffer Dall's talks about KVM on ARM: Reducing hypervisor overhead, and nested virtualization. Seeing the virtualization architecture on ARM makes me really glad to work on s390, and it makes the efforts of the ARM folks all the more impressive (writing code for an architecture revision for which no hardware yet exists... oh dear).


Virtio is currently moving towards the 1.1 revision of the standard, with one of the biggest changes a new ring layout. Jens Freimann (who took over last minute from Michael S. Tsirkin, who unfortunately could not make it) presented about this ongoing work, and also gave some tips on how to get changes included in the standard (let me point to the OASIS virtio TC here). There was also a presentation about virtio-crypto, which I unfortunately was not able to attend.

VFIO (and the mediated device framework) continues to be a topic of interest. There were talks about enabling migration, buffer sharing, and adding support for a new platform bus. On a related note, we (the s390 maintainers) were able to sit down with Alex Williamson and Daniel Berrange to discuss the vfio-ap proposal for s390 crypto cards; this approach has a good chance of being workable.

Hannes Reinecke and Paolo Bonzini presented about the challenges virtualizing SCSI Fibre Channel (NPIV): A good overview of what the challenges are and how we might be able to solve them.

Also of note: Improving virtio-blk performance with polling, introducing a paravirtualized RDMA device, and vhost-user-scsi and SPDK.


I'm currently trying to learn more about tcg and used the opportunity to attend two talks.

Alessandro Di Federico started his talk with a good general introduction to tcg. His work to split out a libtcg is interesting, but it might be done at the wrong level for usage with QEMU (or so I understood from the discussion.)

I also enjoyed Alex Bennée's talk about handling vectors in tcg (complete with an historical overview of vector instructions).


David Gilbert presented on the various reasons a migration might fail. Most migrations don't fail, so people tend to do it more and more in an automated way. If you have the misfortune of having a migration actually do fail on you, his talk gives a lot of pointers on how to find out why it happened (and hopefully, avoiding the problem in the future.)

Markus Armbruster gave an overview of the current QEMU command line infrastructure and how to improve it via QAPIfication (we probably need to sacrifice some rubber chickens backward compatibility).

Also: KubeVirt, running large deployments via libvirt, and the effects of changed defaults on users.


KVM Forum 2017 was really interesting (if somewhat exhausting) for learning about new developments and discussing with people; if you are working in the area, I can only recommend trying to attend KVM Forum.

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