Re: KVM & VMX root mode

Avi Kivity
2007-09-01T14:25:45Z

Sander van Leeuwen wrote:
> Hi,
>
> We have had several reports of users saying our product VirtualBox
> crashes their (Linux) host. It turned out that KVM is responsible, because
> it leaves the CPU in VMX root mode.
>
> Doing this changes the way the cpu operates: updates to reserved bits in
> control registers cause general protection faults.
> We hit such cases on two occasions; clearing the X86_CR4_VMXE bit in CR4
> and turning off paging.
>
> I have added a workaround to detect VMX root mode, simply refuse to run
> and recommend that the user disables KVM.
> I would however appreciate if you could fix KVM instead.
>
>

Simply '/sbin/rmmod kvm-intel' and kvm will exit vmx root mode.

--
Any sufficiently difficult bug is indistinguishable from a feature.