Opened 4 years ago
Closed 4 years ago
#19659 closed defect (invalid)
Nested VT-X can be enabled with VBoxManage when CPU doesn't provide the VMCS Shadowing feature
| Reported by: | fth0 | Owned by: | |
|---|---|---|---|
| Component: | VMM/HWACCM | Version: | VirtualBox 6.1.10 |
| Keywords: | nested virtualization | Cc: | |
| Guest type: | all | Host type: | all |
Description
Many current Intel mobile CPUs do not provide the VMCS Shadowing feature that VirtualBox needs to provide efficient nested virtualization.
While the VirtualBox Manager prevents the user from enabling Nested VT-X in this case (by greying out), the VBoxManage modifyvm <vm name> --nested-hw-virt on command allows the user to enable Nested VT-X. But then VirtualBox does not even provide EPT to the primary VM. Is this an oversight, or is this working as intended?
Note:
See TracTickets
for help on using tickets.
This is a good question. The answer is that this behaviour is intentional since VBoxManage can be used to create/modify VMs which are going to be run on a different host system than the host where VBoxManage is run. The VirtualBox GUI obviously deals with guest VMs that are going to run on the same host so the CPU features and etc. need to be rationalized to align with the host's features and capabilities. But by design VBoxManage and users of the VirtualBox API aren't constrained to the host system's capabilities or configuration in order to provide flexibility for provisioning VMs of varying configurations to be deployed elsewhere.
Closing this as 'not a bug'.