OpenBSD Guest on a KVM Host

Computer environments without virtualisation are not possible anymore. Theoretically all problems in this are should be solved by now. There are is an exception:

Running OpenBSD as a guest under KVM, unfortunately gives some headaches. ⇒SEPPmail, our preferred mail encryption gateway, is a prominent example. It was running for years without problems. It has no problems under VMware, neither as appliance. As a KVM guest it started to behave badly.

2 countermeasures are required to make it run smooth again:

The configuration of the virtual machine in ⇒Proxmox:

boot: c
bootdisk: virtio0
cores: 1
hotplug: 0
memory: 4096
name: <hostname>
net0: virtio=<mac-addresse>,bridge=vmbr0,tag=3
numa: 0
ostype: other
scsihw: virtio-scsi-pci
serial0: socket
smbios1: uuid=<uuid>
sockets: 1
tablet: 0
vga: serial0
virtio0: ceph:<disk>,size=30G

Important are sockets: 1 and serial0: socket.

Using a VGA console, the CPU starts using 100% and the machine freezes. Use a serial console as the solution for this problem.

On current Proxmox versions, the synchronisation of the time does not work anymore.

Running the command:

time sleep 1

I expect a duration of 1 second. Not so with OpenBSD and KVM (Proxmox). After a few hours uptime the duration of this command takes several seconds. After a reboot everything is fine for a short time period.

This problem can be solved:

On the host system (Proxmox) you execute the command:

echo options kvm-intel preemption_timer=N >>/etc/modprobe.d/kvm-intel.conf

Reboot the host system.

Then check the values:

cat /sys/module/kvm_intel/parameters/preemption_timer

If it returns “N”, the problem is solved.

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