kvm: disabled by bios

does your kvm VM feel sluggish? mine did feel pretty slow.. as it turned out virt-install quietly overrode ‘hvm’ preferences and created a fully emulated qemu vm when it failed to make use of hardware-assisted virtualization.

after noticing unusually slow boot time i’ve run both on the host and guest:

root@host:~# openssl speed md5
Doing md5 for 3s on 16 size blocks: 21529562 md5's in 3.00s

vs

root@guest:~# openssl speed md5
Doing md5 for 3s on 16 size blocks: 2072732  md5's in 3.00s

notice that the later result is ~ 10x slower. i’ve diffed /etc/libvirt/qemu/guest.xml with a definition of similar VM from another server and found out the difference:

< <domain type='kvm'>
---
> <domain type='qemu'>

editing the definition file manually and trying to start the guest cryptic:

error: Failed to start domain guest
error: unsupported configuration: Domain requires KVM, but it is not available. Check that virtualization is enabled in the host BIOS, and host configuration is setup to load the kvm modules.

since /proc/cpuinfo contained lines with vmx and i had another identical physical server with well performing KVM guests – i’ve checked BIOS and indeed – interl virtualisation technology was disabled. after flipping it on it was possible to boot the KVM guest with type=’kvm’.

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