Zesty / Artful zKVM does not have /dev/kvm

[Po-Hsu Lin]

For now we have 3 zKVM instances running Xenial, Zesty and Artful kernel respectively.

The /dev/kvm does not exist on Zesty and Artful kernel.

kvm-ok output on Zesty
$ sudo kvm-ok
INFO: /dev/kvm does not exist
HINT: sudo modprobe kvm
modprobe: FATAL: Module msr not found in directory /lib/modules/4.10.0-40-generic

kvm-ok output on Artful
$ sudo kvm-ok
INFO: /dev/kvm does not exist
HINT: sudo modprobe kvm
modprobe: FATAL: Module msr not found in directory /lib/modules/4.13.0-17-generic

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: linux-image-4.13.0-17-generic 4.13.0-17.20
ProcVersionSignature: Ubuntu 4.13.0-17.20-generic 4.13.8
Uname: Linux 4.13.0-17-generic s390x
NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
AlsaDevices: Error: command ['ls', '-l', '/dev/snd/'] failed with exit code 2: ls: cannot access '/dev/snd/': No such file or directory
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay'
ApportVersion: 2.20.7-0ubuntu3.2
Architecture: s390x
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord': 'arecord'
CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 not found.
CurrentDmesg:

Date: Tue Nov 14 11:18:49 2017
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig': 'iwconfig'
Lspci:

Lsusb: Error: command ['lsusb'] failed with exit code 1:
PciMultimedia:

ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C
 SHELL=/bin/bash
ProcFB: Error: [Errno 2] No such file or directory: '/proc/fb'
ProcKernelCmdLine: root=UUID=d86dc8de-6ac8-4e4b-aba8-92872a209a8c crashkernel=196M
RelatedPackageVersions:
 linux-restricted-modules-4.13.0-17-generic N/A
 linux-backports-modules-4.13.0-17-generic N/A
 linux-firmware 1.169
RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1732162

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Christian Ehrhardt  (paelzer)]

Hi,
I investigated this a bit.

TL;DR - this is intentionally off by default and opt in.
To use it you need:
- in the host set kvm.nested=1
- depending on your other virt stack set you might need to set host-passthrough or the sief2 feature (qemu -cpu host or ...,sief2=1)

Then the guest will have virt features "sie" in /proc/cpuinfo | grep features

If anything we should consider backporting the "needs opt in" to Xenial.
That would be the following patch:
commit a411edf1320ed8fa3b4560902ac4e033c4a72bcf
Author: David Hildenbrand <email address hidden>
Date: Tue Feb 2 15:41:22 2016 +0100

    KVM: s390: vsie: add module parameter "nested"

    Let's be careful first and allow nested virtualization only if enabled
    by the system administrator. In addition, user space still has to
    explicitly enable it via SCLP features for it to work.

[Frank Heimes (fheimes)]

Changing to Invalid due to last comment and the fact that Zesty and Artful are out of support.