id summary reporter owner description type status component version resolution keywords cc guest host 15728 VM Hangs at 100% CPU On Boot rfkrocktk-oracle "This issue has been present since VirtualBox 4, and is still present in the latest release of VirtualBox 5.1 on Ubuntu, package version: 5.1.2-108956~Ubuntu~trusty. The issue is reproducible across all types of guest operating systems, therefore it appears to be a host-level bug in VirtualBox itself. I've seen this issue manifest on various Ubuntu and Fedora versions as well as Windows 7. I can install an operating system on the first boot up (ie, when there's nothing installed on the virtual disk). After that, as soon as I power off and then power on the machine, I cannot even get the guest to POST. The machine hangs at 100% CPU usage and I don't even get the VirtualBox BIOS boot screen. I get a progress bar that eventually displays saying ""Starting Virtual Machine"", but no progress is made and one CPU is locked to 100% utilization. Interestingly enough, I don't have this problem with headless VMs created via Vagrant, only with VMs I have manually installed using live CDs. I'm running kernel 4.4.0 from the official Ubuntu repositories. The filesystem on the host is a BTRFS subvolume on top of a LUKS encrypted container. I have BTRFS compression enabled on the subvolume, but the bug is present with or without compression enabled. There's nothing triggered in syslog or dmesg on the host during the issue with the guest, nothing seems amiss. A screenshot of starting the VM: https://imgur.com/bsyvLrp Here is my VM's log with all of the attempted boots: https://gist.github.com/rfkrocktk/a0e7e52151f36b4cf4e131b639330864 " defect closed other VirtualBox 5.1.2 duplicate all Linux