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Cadeyrn

Member

Registered: 2013-04-06

Posts: 170

[SOLVED] libvirt 2.0.0-1: host-model: CPU feature cmt not found

I'm using QEMU/KVM on libvirt to run a gaming Windows virtual machine, using VGA passthrough with OVMF. (I followed the Arch Wiki page on it and this guide to create it: http://vfio.blogspot.com/2015/05/vfio-g … dware.html). It's been working great since August, but when I upgraded libvirt and libvirt-python from 1.3.5-1 to 2.0.0-1, trying to run that VM results in the following error:

$ sudo virsh start Windows
error: Failed to start domain Windows
error: internal error: qemu unexpectedly closed the monitor: 2016-07-06T04:18:08.394668Z qemu-system-x86_64: CPU feature cmt not found

Through process of elimination, I've tracked the culprit down to be setting the CPU to "host-model", i.e. copying the host configuration. In libvirt 1.3.5-1 (and probably all older versions) I can do that, but in 2.0.0-1, it causes that error. Downgrading libvirt and libvirt-python back to 1.3.5-1 fixed it.

EDIT: Fix found here: http://forums.debian.net/viewtopic.php?f=5&t=128949

Changing "host-model" in the setting to "host-passthrough" fixed it, as explained in that link. Makes sense, as before the update, "host-passthrough" is what I had it on. I just assumed it had been renamed to "host-model" in the new version, but no. It looks like some interaction between virt-manager (the GUI) and libvirt caused the way that it stored my "host-passthrough" setting to be recognized as "host-model" in the new version until I changed it back, which I guess is a totally different setting that requires something my hardware doesn't support: "cmt".

Last edited by Cadeyrn (2016-07-12 04:17:44)