id	summary	reporter	owner	description	type	status	component	version	resolution	keywords	cc	guest	host
12453	Workaround for VT-x unlock on host resume from sleep/hibernate?	PeterVB		"Buggy BIOS/UEFI firmware may cause the host VT-x/AMD-V setting to unlock after it resumes from sleep or hibernation.  When this happens, 64-bit VirtualBox VMs will refuse to power on, and the VirtualBox Manager will no longer show 64-bit operating systems as choices for new VMs.  Host operating systems (e.g. Windows 7 64-bit) seem unaffected by the issue.

When VirtualBox no longer recognizes the host VT-x setting, the only solution is to power off the host completely.  For VirtualBox, the only permanent workaround is to disable sleep and/or hibernation.  However, other virtualization solutions include built-in solutions to this problem (ref. [https://communities.vmware.com/docs/DOC-8978]).

It would be very helpful if VirtualBox also had a method of automatically re-enabling and re-locking VT-x in this situation.  Barring an automatic solution, a global preference to ignore the current VT-x setting might work.  (Not sure if VirtualBox is actually reading out the VT-x setting from the BIOS or picking it up from the host?)

I am in the middle of another round of testing regarding this issue and will submit a logfile shortly.  Thanks.
"	enhancement	closed	VMM/HWACCM	VirtualBox 4.3.4	wontfix	VT-x AMD-V unlock disable resume sleep hibernate		all	all